Ancuța Rotaru, Phd

HABILITATION THESIS

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards

Associate Professor Ancuța Rotaru, PhD

2021

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards

To those never distant

Abstract

This habilitation thesis gets the most out of the scientific achievements carried out after the doctoral thesis defence – November 27, 1997, until the end of 2020. Experiments have gone off in the laboratories of the Faculty of Civil Engineering and Building Services of the 'Gheorghe Asachi' Technical University of Iași, where I am carrying out my professional activity in research teams assigned to the Civil Engineering domain. The outcomes appeared in journals/volumes of scientific events with broad international visibility and books/book chapters recognized by CNCSIS or internationally. Also, part of the research activity presented in the thesis was carried out in laboratories abroad, in research partnerships with colleagues from Beira Interior University in Covilha (Portugal), the 'Todor Kableshkov' University of Transport in Sofia (Bulgaria), Jadavpur University in Kolkata (India), American University in Madaba (Jordan), Mohammed V University in Rabat (Morocco). To date, this collaboration has materialized in the publication of 15 scientific papers indexed in international databases (Web of Science, Scopus, Springer). The concept of eco-efficiency was coined first in the book Changing Course (Schmidheiny, 1992) in the 1992 Earth Summit context. This concept expresses 'the development of products and services at competitive prices that meet the needs of humankind with quality of life, while progressively reducing their environmental impact and consumption of raw materials throughout their life cycle, to a level compatible with the capacity of the planet'. Infrastructure materials encompassing bridges, piers, pipelines, dams, pavements or building foundations are crucial to modern civilization activities. Unfortunately, these materials deteriorate due to several causes like excessive loading/ impact (mechanical deterioration) or erosion/ freeze-thaw (physical reasons). Frequently, however, building materials deteriorate through natural disaster effects like earthquakes, landslides, floods, tornadoes, etc. Sustainable repair and rehabilitation mean to increase the service life of substructure works and use eco-efficient materials to design accounting for damaging effects due to hazard risks. The purpose of the habilitation thesis entitled Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards is to contribute to this area of study, showing those factors which negatively influence the service life of structures. Chapter 1, Introduction: Unitary Methodology of Investigation, reviews the unitary methodology for investigating the process of degradation or collapse of structures, identifying the origins and causes, diagnosis and alternative approaches for the maintenance and sustainable rehabilitation of buildings at risk of damage or failure. Each experimental chapter of the thesis (chapters 2-4) analyzes a topic that, in addition to the results disseminated through published papers, highlights the experience gained in one project won through a national competition where the author was the manager. Thus, Chapter 2, Interaction of External Agents (Hazard Risks) Responsible for Building Decay or Failure, analyzes the risks produced to buildings by landslides and earthquakes, design methods, case studies in Romania (intervention proposals and results) as well as some considerations on repairs and

Ancuța Rotaru Habilitation Thesis corrections to prevent and reduce landslides. It also analyzes the factors contributing to building deterioration due to earthquakes, landslides and liquefaction conditions, and Romania's seismicity regarding structure risks to failure: geological structure and specific seismic circumstances, earthquakes and landslides in the Dobrogea region. The unitary methodology of approaching the chapter dedicated to building risks of deterioration and collapse due to natural hazards bases on the most representative scientific papers on the topic. Yet, it also bases on the experience acquired from the CNCSIS project Landslides Risk Mitigation – Challenge and Strategy (2009 – exploratory workshop, PNCDI II - manager) that brought together experts in the field from the European space. Chapter 3, Interaction of Soil / Rock Characteristics Responsible for Foundation Soil / Building Decay, analyzes the deformability of homogeneous and discontinuous rock masses in terms of foundation ground and soil mechanical behaviour, evaluates the slope stability using the finite element method and the role of water in the foundation soil resource management. Also, the chapter analyzes a series of specific characteristics of foundation soils in Romania, like geotechnical factors responsible for the deterioration of foundation soils, geotechnical risks in some regions with difficult foundation soils (Dobrogea and Moldova) to increase their safety and durability. The author’s coordination experience in the project Procedures and Techniques for Improving the Properties of Difficult Foundation Soils to Increase the Safety and Durability of Engineering Constructions (2005 - 2006 – manager, MEC grant A) complements the scientific papers selected to outline the foundation soil characterization. Chapter 4 analyzes the physical and mechanical characteristics of several residual materials used as a binder in infrastructure works for the sustainable built environment. The study performs in two directions: 1) analysis of the properties of different types of ash, residue used as a binder for infrastructure works (roads, improvement of difficult foundation soils, etc.), 2) analysis of physical and mechanical properties of concrete to which the binder is replaced with various residues to streamline production costs and release the environment of polluting waste. This chapter bases on laboratory experiments conducted in recent years and disseminated in a series of scientific papers published in impact factor journals. The experience gained in the strategic partnership project entitled Rehabilitation of the Built Environment in the Context of Smart City and Sustainable Development Concepts for Knowledge Transfer and Lifelong Learning between eight European universities (2018 - 2021, E+ KA203, strategic partnership – manager) completes the discussion. Chapter 5, Objectives of Scientific Research, Contributions to the Field of Civil Engineering and Future Research Directions, outlines three fields of study: 1) the substructure behaviour concerning landslides and earthquakes mitigating the risk effects on foundations and foundation soil; 2) the interaction of the foundation soil and the role of its characteristics on the stability and safety of buildings; 3) improving the performance of materials used in substructure works as well as the quality of the built environment using eco-friendly materials such as polluting wastes from various economic activities.

I authored or co-authored 122 publications, of which: ISI = 11, BDI = 38 and others = 73. So far, I have been a key speaker in 39 scientific events, of which 35 international. I coordinated 5 projects as a manager, one of which with international participation. I participated with papers in 83 conferences and symposiums, of which 65 international. I coordinate 36 Erasmus+ KA103 programmes with the EU Member States and 33 Erasmus+ KA107 programmes with non-EU countries.

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards

Rezumat

Această teză de abilitare prezintă selectiv cele mai importante realizări științifice rezultate din activitatea de cercetare ulterioară datei de 27 noiembrie 1997, data susținerii publice a tezei de doctorat, până la finele anului 2020. Experimentele au fost realizate în laboratoarele de cercetare ale Facultății de Construcții și Instalații din cadrul Universității Tehnice „Gheorghe Asachi” din Iași, unde îmi desfășor activitatea profesională, în colective de cercetare subordonate domeniului Ingineriei Civile. Rezultatele au fost diseminate sub forma unor lucrări științifice în reviste sau în volumele unor manifestări științifice cu largă vizibilitate internațională, precum și în cărți/capitole de cărți recunoscute CNCSIS sau pe plan internațional. De asemenea, o parte din activitatea de cercetare prezentată în teza de abilitare s-a desfășurat în laboratoare din străinătate, în cadrul unor parteneriate de cercetare cu colegii de la Universitatea Beira Interior din Covilha (Portugalia), Universitatea de Transport “Todor Kableshkov” din Sofia (Bulgaria), Universitatea Jadavpur din Kolkata (India), Universitatea Americană din Madaba (Iordania), Universitatea Mohammed V din Rabat (Maroc). Până în prezent, colaborarea aceasta s-a materializat în publicarea a 15 lucrări științifice, toate indexate în baze de date internaționale (Web of Science, Scopus, Springer). Conceptul de eco-eficiență a fost folosit pentru prima dată în cartea Schimbarea cursului (Schmidheiny, 1992) în contextul Summit-ului Pământului din 1992. Acest concept exprimă „dezvoltarea produselor și serviciilor la prețuri competitive care să îmbine armonios nevoile omenirii cu calitatea vieții, reducând, în același timp, impactul asupra mediului și consumul de materii prime pe tot parcursul ciclului lor de viață, la un nivel compatibil cu capacitatea planetei”. Materialele folosite la realizarea lucrărilor de infrastructură precum poduri, conducte, baraje, asfaltarea și modernizarea drumurilor sau la fundațiile clădirilor, sunt extrem de necesare activităților societății moderne. Însă, aceste materiale se deteriorează datorită unor cauze ce includ: greutate excesivă, impact (deteriorări mecanice), eroziune sau îngheț-dezgheț (cauze fizice). Mult mai frecvent, totuși, aceste materiale de construcții se deteriorează datorită efectelor induse de dezastre naturale precum cutremurele de pământ, alunecările de teren, inundații, tornade etc. Repararea și reabilitarea sustenabilă presupune creșterea perioadei de exploatare a lucrărilor de infrastructură și folosirea materialelor eco-eficiente pentru proiectare, ținând cont de efectele distrugătoare ale dezastrelor naturale. Scopul acestei teze de abilitare, intitulată Eco- friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards, are drept scop să aducă contribuții în aceast domeniu de studiu, arătând factorii care influențează negativ durata de viață a structuri. Capitolul 1, Introduction: Unitary Methodology of Investigation, face o trecere în revistă a metodologiei unitare de investigație a procesului de degradare sau colaps al structurilor, identificând originile și cauzele, diagnosticul și alternative de abordare în vederea mentenanței și reabilitării sustenabile a construcțiilor supuse riscului de deteriorare sau prăbușire.

Ancuța Rotaru Habilitation Thesis

Fiecare capitol experimental al tezei (capitolele 2-4) analizază câte un subiect care, pe lângă rezultatele diseminate printr-un număr de lucrări publicate, pune în valoare experiența acumulată în câte un proiect câștigat prin competiție națională la care autoarea a avut calitatea de director. Astfel, Capitolul 2, Interaction of External Agents (Hazard Risks) Responsible for Building Decay or Failure, analizează riscurile provocate de alunecările de teren și cutremurele de pământ construcțiilor aflate în exploatare, modalități de proiectare, studii de caz din România (propuneri de intervenție și rezultate) precum și considerații asupra reparațiilor și corecțiilor realizate pentru prevenirea și reducerea alunecărilor de teren. De asemenea, se analizează factorii ce influențează deteriorarea construcțiilor datorită cutremurelor de pământ, lichefierea pământurilor și condiții de lichefiere in situ, precum și seismicitatea României din punct de vedere al riscului major de colaps al structurilor: structura geologică și condiții specifice de seismicitate, cutremure de pământ în regiunea Dobrogea. Metodologia unitară de abordare a capitolului dedicat riscurilor de deteriorare și colaps ale construcțiilor datorită hazardelor naturale se bazează pe selectarea celor mai reprezentative lucrări științifice dedicate subiectului, dar și pe experiența acumulată în timpul proiectului lansat de CNCSIS de organizare a workshop-ului exploratoriu Landslides Risk Mitigation – Challenge and Strategy (2009 – director, PNCDI II) care a reunit specialiști de renume în domeniu din spațiul european. Capitolul 3, Interaction of Soil/Rock Characteristics Responsible for Foundation Soil/Building Decay, analizează deformabilitatea maselor de roci omogene și discontinue din punct de vedere al terenului de fundare, comportarea mecanică a pământurilor, evaluează stabilitatea taluzurilor folosind metoda elementului finit, rolul apei în managementul resurselor terenului de fundare. De asemenea, capitolul analizează o serie de caracteristici specifice terenurilor de fundare din România: factori geotehnici responsabili de deteriorarea terenurilor de fundare, riscuri geotehnice în unele regiuni cu terenuri dificile de fundare (Dobrogea și Moldova) în vederea creșterii siguranței și durabilității acestora. Lucrările științifice selectate pentru a contura preocupările legate de caracterizarea terenurilor de fundare sunt completate de experiența de coordonare a proiectului Procedee și tehnologii de îmbunătățire a proprietăților terenurilor dificile de fundare în vederea creșterii siguranței și durabilității construcțiilor inginerești (2005 - 2006 – director, grant MEC tip A). În Capitolul 4 sunt analizate caracteristicile fizico-mecanice pentru o serie de materiale reziduale folosite ca liant în lucrări de infrastructură în vederea dezvoltării durabile a mediului construit. Studiul este realizat pe două direcții: 1) analiza proprietăților diferitelor tipuri de cenușă, reziduu folosit ca liant pentru lucrări de infrastructură (drumuri, îmbunătățirea terenurilor dificile de fundare etc.) și 2) analiza proprietăților fizico-mecanice ale betonului la care liantul este înlocuit cu diverse reziduuri în vederea eficientizării costurilor de producție și a degajării mediului înconjurător de deșeuri poluante. Acest capitol se bazează pe experimente de laborator realizate în ultimii ani și diseminate într-o serie de lucrări științifice publicate în reviste cu factor de impact. Discuția este completată de experiența acumulată în proiectul de parteneriat strategic între opt universități europene cu titlul Rehabilitation of the Built Environment in the Context of Smart City and Sustainable Development Concepts for Knowledge Transfer and Lifelong Learning (2018 - 2021, E+ KA203, parteneriat strategic – director). Capitolul 5 prezintă obectivele activității de cercetare științifică, contribuțiile aduse domeniului Inginerie Civilă și trasează direcții de cercetare viitoare în domeniul prezentat, pe trei arii de studiu: 1) comportarea infrastructurii la alunecări de teren și seism și minimizarea efectelor acestor riscuri naturale asupra fundațiilor și terenului de fundare; 2) interacțiunea terenului de fundare și rolul caracteristicilor acestuia asupra stabilității și siguranței în exploatarea a construțiilor; 3) îmbunătățirea performanțelor materialelor puse în operă la lucrările de infrastructură precum și îmbunătățirea calității mediului construit prin folosirea materialelor eco-eficiente precum reziduurile poluante provenite din diverse activități economice.

Sunt autor sau co-autor a 122 de publicații, din care: ISI = 11 , BDI = 38 și altele = 73. Până în prezent, am fost key speaker în 39 de manifestări științifice, dintre care 35 internaționale. 5 proiecte ca director, din care unul cu participare internațională. Participare cu lucrări la 79 de conferințe și simpozioane, din care 65 internaționale. Coordonator a 36 programe Erasmus+ KA103 cu state membre UE și 33 programe Erasmus+ KA107 cu state din afara UE.

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards

Table of Contents

Abstract/Rezumat 1/3

List of figures 5

List of tables 9 I. SYNTHESIS OF DIDACTIC AND SCIENTIFIC ACHIEVEMENTS 12 II. DESCRIPTION OF SCIENTIFIC CONTRIBUTIONS 14 1. Introduction: Unitary Methodology of Investigation 21 1.1. The diagnostic process and its tools 21 1.2. Cause determination 23 1.3. Origins of causes 24 1.4. The decay process and maintenance 24 1.5. Premises 25

2. Interaction of External Agents (Hazard Risks) Responsible for Building Decay or Failure 26 2.1. Landslides 26 2.1.1. Causes of landslides 27 2.1.2. Factors affecting the landslide process (movements of a landslide) 27 2.1.3. Landslide types 28 2.1.4. Processes responsible for landslides 28 2.1.4.1. External change of stability conditions 29 2.1.4.1.1. Seepage from artificial and natural sources of water 29 2.1.4.2. Internal causes of landslides 31 2.1.4.2.1. The presence of groundwater in landslide 31 2.1.4.2.2. Weak zones of a saturated clay landslide 31 2.1.4.2.3. Spontaneous liquefaction 32 2.1.5. Landslide risk evaluation 33 2.1.6. Dynamics of the landslide activity 34 2.1.6.1. Movements preceding a slide 34 2.1.6.2. Movements during the slide 35 2.1.6.2.1. Falls 36 2.1.6.2.2. Topples 37 2.1.6.2.3. Slides 37 2.1.6.2.3.a. Rotational slides 37 2.1.6.2.3.b. Transitional slides 38 2.1.6.2.4. Spread 38 2.1.6.2.5. Flows 38 2.1.6.2.5.a. Rockflow 38 2.1.6.2.5.b. Earthflow 39

Ancuța Rotaru Habilitation Thesis

2.1.6.2.5.c. Debris flow 39 2.1.6.2.5.d. Mudflow 39 2.1.6.2.6. Complex landslides 40 2.1.6.3. Movements after slide 40 2.1.6.4. Reactivation stage 40 2.1.7. “Fresh” and historical landslides 41 2.1.8. The distribution of landslides 41 2.1.8.1. The frequency–area (or volume) distribution of a landslide 41 2.1.8.2. The general landslide distribution 42 2.1.8.2.1. Landslide magnitude scale 43 2.1.8.2.2. Historical and incomplete inventories 43 2.1.8.3. Stability analysis 44 2.1.9. Landslides in Romania 45 2.1.9.1. Characteristics of romanian landslides 45 2.1.9.2. Romanian landslides – Case studies 47 2.1.9.2.1. Moldavian Plateau 47 2.1.9.2.2. Pericarpathian Hills 48 2.1.9.2.3. Getic Piedmont 50 2.1.9.2.4. The Transilvanian Plateau 50 2.1.9.2.5. Danubian side of Dobruja Plateau 50 2.1.10. Landslides repair and correction considerations 52 2.1.10.1. Case study 1 – Zemeș, Bacău County, Romania 54 2.1.10.1.1. Intervention proposals 55 2.1.10.1.2. Results based on the stability calculations 56 2.1.10.1.3. Intervention analysis 57 2.1.10.2. Case study 2 – Toplița municipality, Harghita County, Romania 57 2.1.10.2.1. Intervention proposals 58 2.1.10.2.2. Results 59 2.1.10.3. Case study 3 – Pârcovaci, Iași County, Romania 59 2.2. Earthquakes 60 2.2.1. Factors influencing building damage 60 2.2.2. Liquefaction 63 2.2.2.1. Conditions in a soil deposit before an earthquake 63 2.2.2.2. Criteria for liquefaction 63 2.2.3. Seismicity of Romania 65 2.2.3.1. Geological structure and seismological conditions 67 2.2.3.2. The earthquake influence on environmental damage 67 2.2.3.3. How to build 68 2.2.3.4. Earthquakes in Dobruja region 69

3. Interaction of Soil/Rock Characteristics Responsible for Foundation Soil/Building Decay 72 3.1. Deformability analysis of rock for homogenious and discontinuous multi-crack masses 72 3.1.1. Homogenized Multi-Crack Model (HMCM) 72 3.1.2. Application of 2D-DDM and Homogenization 73 3.1.3. Estimation of Constraint Stress and of Effective Compilance 74 3.1.4. Theoretical Background of the Failure Simulation of Rock Masses by Discountinuous Deformation Analysis (DDA) 75 3.2. Mechanical bevahiour of an unsaturated soil associated with seepage 75 3.2.1. Materials and metods 76 3.2.2. Testing Programme and Proceedings 77

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards

3.2.3. Stress paths in critical state 79 3.2.4. Shear behavior with leakage effect 80 3.3. Stability coefficients vs stability evaluation using Finite Element-Neural Network Hybrid Algorithms for slope analysis 82 3.3.1. Constitutive modelling 83 3.3.2. Incorporation of a NN Constitutive Model within the FE 84 3.3.3. The FE-NN Hybrid Model for Soil 85 3.4.Groundwater resources management 85 3.4.1. Groundwater quality treatment 85 3.4.2. Groundwater monitoring and flow modelling 87

3.4.3. Groundwater quality and remediation 87 3.5.Geotechnical characteristics responsible for foundation soil decay in Romania 88 3.5.1. Geotechnical risk in Dobruja region of Romania/Bulgaria 88 3.5.1.1. Reasons to study the Black Sea Basin 89 3.5.1.2. Tectonic theory vs anomalous magnetic theory on the black sea basin origin 89 3.5.1.2.1. Tectonic Theory 89 3.5.1.2.1.a. Black Sea Tectonic Evolution Models 89 3.5.1.2.1.b. Platform Conditions 90 3.5.1.2.1.c. Romanian Platform Conditions 91 3.5.1.2.1.d. Deep Sea Basin Conditions 91 3.5.1.2.2. The Anomalous Magnetic Theory 92 3.5.1.3. Sedimentation versus erosion 92 3.5.1.3.1. Fresh Water Discharge 92 3.5.1.3.2. Sediment Discharge 93 3.5.1.3.2.a. Coastal (Beach-forming) Sediments 93 3.5.1.3.2.b. Marine (Deep-water) Sediments 94 3.5.1.3.2.c. Sediments in the Romanian Sector 94 3.5.1.4. Erosion 94 3.5.1.5. Specific geology in Dobruja Region 95 3.5.1.5.1. The geologic history of Dobruja Region 95 3.5.1.5.2. Tectonic activity of Dobruja Region 96 3.5.1.5.3. The lakes of the Black Sea coast 97 3.5.1.6. Geological risk 97 3.5.1.6.1. Limestone karsts 97 3.5.1.6.2. Abrasion and erosion of the Black Sea shore and Danube Delta97 3.5.1.7. Technical works carried out on Dobruja Plateau 98 3.5.1.7.1. Wind farm projects 99 3.5.1.7.2. Shore protection projects 100 3.5.1.7.3. Foundation issues on the limestone karsts, liquefacted sand and silty clay 100 3.5.1.7.4. Disposals for the radioactive waste of Cernavoda Nuclear Power Plant 101 3.5.2. Considerations on the hydrostatic level in Romania. Moineşti area 102 3.5.2.1. Climatic and geological data for the considered area 103 3.5.2.2. Hydrological data. Groundwater – depth variation report 104

3.5.3. Difficult foundation soils/swelling-shrinking clays in Iași City, Romania 105 3.5.3.1. Swelling-shrinking clays from Iaşi area, Romania 106

4. Sustainable Development of Materials Used in Substructure Works 108 4.1. The ash – a cement-like material used in substructure and road works 108 4.1.1. Physical Characteristics of Pozzolana Fly Ash from Thermal Power Plant of Iași, Romania 108

Ancuța Rotaru Habilitation Thesis

4.1.1.1. Fly ash - general features 109 4.1.1.2. Chemical analysis of fly ash from Iași thermal power plant 110 4.1.1.3. Physical features of fly ash from Iași thermal power plant 111 4.1.1.4. Compaction characteristics of fly ash from thermal power plant of Iași 113 4.1.1.5. Environmental issues concerning fly ash from thermal power plants 113 4.1.2. Mecanical Characteristics of Pozzolana Fly Ash from Thermal Power Plant of Iași, Romania 114 4.1.3. The compressive behaviour of aggregates cemented with fly ash collected from coal-fired power plants 119 4.1.3.1. Materials 120 4.1.3.1.1. Aggregates 121 4.1.3.1.2. The fly ash 121 4.1.3.2. Methods 122 4.1.3.3. Results 123 4.1.4. The bituminous oil shale ash influence on stabilized silty-sandy brown clay 124 4.1.4.1. Materials 126 4.1.4.1.1. Bituminous oil shale ash 126

4.1.4.1.2. Brown clay 127 4.1.4.2. Methods 127 4.1.4.2.1. The grain-size distribution curve 127 4.1.4.2.2. Atterberg Limits 127 4.1.4.2.3. Compaction test 127 4.1.4.2.4. Permeability test 128 4.1.4.2.5. Unconfined compression test 128 4.1.4.2.6. Consolidation test 129 4.1.4.3. Results 130 4.2. Properties of the concrete with waste replacements 132 4.2.1. Mechanical properties of polymer concrete with waste replacements 132 4.2.1.1. Materials 133 4.2.1.2. Experimental procedure 133 4.2.1.3. Results 134 4.2.1.3.1. Compressive strength 134 4.2.1.3.2. Flexural strength 134 4.2.1.3.3. Split tensile strength 134 4.2.2. Mechanical features of lightweight concretes by aggregate replacement 135 4.2.2.1. Materials 135 4.2.2.2. Results 136 4.2.2.2.1. Density 136 4.2.2.2.2. Compressive strength 136 4.2.2.2.3. Flexural strength 136 4.2.2.2.4. Split tensile strength 137 4.2.3. Tensile properties of the green polymer concrete 137 4.2.3.1. Experimental programme 138 4.2.3.2. Results 138 4.2.3.2.1. Flexural strength 138 4.2.3.2.2. Splitting strength 139

5. Objectives of Scientific Research, Contributions to the Field of Civil Engineering 140 III. DEVELOPMENT DIRECTIONS 141

References 143

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards

List of Figures

Chapter 1 Introduction: Unitary Methodology of Investigation Fig.1. The investigation process Fig.2. The diagnostic process and its tools Fig.3. The decay process

Chapter 2 Interaction of External Agents (Hazard Risks) Responsible for Building Decay or Failure Fig.4. Shear resistance vs shear force during a landslide movement Fig.5. Annual time series of temperature changes of one-meter depth under ground, in Japan (after Malamud et al., 2004) Fig.6. Fall Fig.7. Topple Fig.8. Movement along a circular failure surface of a topple: transition Fig.9. Rotational slide Fig.10. Rotation along a circular failure surface Fig.11. Transitional slide Fig.12. Earthflow Fig.13. Debris flow Fig.14. Mudflow Fig.15. Creep Fig.16. The life cycle of a landslide Fig.17. Dependence of the mean landslide volume on the total number of the landslide in the event (after Malamud et al., 2004) Fig.18. Predicted landslide-event areas and volumes associated with a given landslide event magnitude (after Malamud et al., 2004) Fig. 19. Landslide risk mitigation actions Fig.20. Landslide risk in the European surveyed countries Fig.11. Areas with landslides in Romania (after http://www.geo-strategies.com/) Fig.22. Romanian Counties developping landslides Fig.23. Landslide in Suceava County Fig.24. Iași County landslide Fig.25. Landslides nearby Siriu, Buzău County Fig.26. Hunedoara County landslide Fig.27. Maramureș County landslide Fig.28. Sighișoara landslide, Mureș County Fig.29. Geological cross section on km 58 landslide along Danube-Black Sea Canal Fig.30. Slope stabilization techniques Fig.31. Slope stabilization techniques - retaining walls Fig.32. The Tazlăul Sărat River. a) remains of old concrete walls (left); b) large boulders along the riverbed (right) Fig.33. The Tazlăul Sărat River. a) horizontal translation (left); b) rotational motion,

Ancuța Rotaru Habilitation Thesis the foundation in a console (right) Fig. 32. (a, b) Existing retaining wall: missing/damaged parts Fig.33. (a, b, c) Discontinuities of the beam where the metal safety railing belongs parts Fig.364. Lanslide – Pârcovaci Village, 1996 Fig.37. Romania map of seismic risk Fig.38. Geotechnical profile of the city of Bacău Fig.39. Dobruja Region. Tectonic activity Fig.40. Dobruja’s tectonic fault lines Fig.41. South Dobruja shoreline beween Shabla and Varna City

Chapter 3 Interaction of Soil/Rock Characteristics Responsible for Foundation Soil/Building Decay Fig.42. (left) Homogenized multi-crack model; Fig.43. (up) Elemental region; Fig.44. (right) Displacement discontinuity elements on the crack line Fig.45 (a, b) Residual granite soil of Covilhã: a) relative position of remoulded samples 3 (A-nc) in function of compaction curves defined by the compactive efforts E1=593 kJ/m 3 and E2=112 kJ/m ; b) spatial distribution e:S for a group of samples Fig.46. Prediction of the stress paths for triaxial tests on samples of residual granitic soil Fig.47. Critical state liness of residual granitic soil: representation in the {q: p´: s} space of the stress paths followed in the planes s = 0 kPa and s = 40 kPa and the respective failure plans for the series I Fig.48. Variation of the stiffness module for drained tests with constant suction and sheared off to σ3´ = 100 kPa Fig.49. Stress paths for shear tests with initial ´30 = 100 kPa and leachate water/ gasoline infiltration Fig.50. A three-layer NN constitutive model for soil Fig.51. Incorporation of a NN constitutive model within the FE Fig.52. Training of the NN soil model within the FE Fig.53. FE-NN hybrid model for soil Fig.54. The analytical model of an excavated slope Fig.55. Slope geometry after excavation Fig.56. A typical groundwater discharge Fig.57. Test chilling (subsurface exploration) Fig.58. A shallow overburden aquifer monitoring well and its basic features Fig.59. Computer groundwater modeling Fig.60. Water supply well Fig.61. Treatment system for removing petroleum components from groundwater Fig.62. The Black Sea map Fig.63. The two main basins of Black Sea Fig.64. Romanian platform conditions Fig.65. The rivers' basins of the Black Sea (from Black Sea GIS, 1997) Fig.66. Dobruja Region (Romania and Bulgaria) Fig.67. Dobruja Region in Bulgaria: Cape of Kaliakra Fig.68. Moesian Block, Intramoesian Fault and North, Central and South Dobruja Fig.69. Romanian Dobruja shore line Fig.70. Proposed plan of shore protection in Romania, from Olimp to Mangalia seaside resorts Fig.51. The compression-settlement curve for Cernavodă loess Fig.72. Moineşti area on the physical and geographical map of Romania (after www.multimap.ro) Fig.73. General view of Moineşti Town Fig.74. Different types of aquifers, after Mutihac et al.(1980), modified Fig.75. Water in vertical profile, after Haida et al. (2004), modified Fig.76. Iași County in Romania’s map Fig.77. Shrinkage coefficients α1, αs, αv for Iași clay

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards

Fig.78.a, b. Water content versus geometrical dimensions before and after drying for Iași clay

Chapter 4 Sustainable Development of Materials Used in Substructure Works Fig.79. Details of Coliseum in Rome Fig.80. Entrance to the Pantheon in Rome Fig.81. Fly ash made in a dry boiler Fig.82. Grain-size distribution curve of Iași fly ash Fig.83. Heterogeneous grain-size of fly ash Fig.84. The colour of fly ash varies from tan to black Fig.85. Modified Proctor compaction test curve Fig.86. Hydraulic evaluation using the modified method Fig.87. Grain size distribution curves of aggregates Fig.88. Grain size distribution curves of fly ashes collected from thermal power plants Fig.89. Decreasing rate of compressive strength of aggregate mixtures stabilized with fly ash/ cement as per STAS 10473 / 1-86 Fig.90. Compressive strength values for aggregates stabilized with Iaşi fly ash Fig.91. Compressive strength values for aggregates stabilized with Vaslui fly ash Fig.92. Map of oil shale deposits in Jordan, locations after Jaber and others, 1997; and Hamarneh, 1998 (after the reprint of: United States Geological Survey Scientific Investigations Report 2005-5294 by John R. Dyni) Fig.93. Location of silty-sandy brown clay after “Al-lajjun Oil Shale Project” – Jordan Energy and Mining Limited Fig.94. Testing procedure Fig.95. Grain-size distribution curve of the silty-sandy brown clay Fig.96. Plasticity index variation at different ash percentages Fig.97a. Compaction curve for the brown clay Fig.97.b. Compaction curve for brown clay - 5% oil shale ash Fig.97.c. Compaction curve for brown clay - 10% oil shale ash Fig.97.d. Compaction curve for brown clay - 10% oil shale Fig.97.e. Compaction curve for brown clay with 20% oil shale ash Fig.98. Permeability of brown clay mixed with different percentages of oil shale ash Fig.99. Classification of permeability coefficient Fig.100.a Unconfined compressive strength of the brown clay mixed with oil shale ash at 7 days Fig.100.b Unconfined compressive strength of the brown clay mixed with oil shale ash at 21 Fig.101.a. Consolidation curve of clay without bituminous oil shale ash Fig.101.b. Consolidation curve of clay with 5% ash Fig.101.c. Consolidation curve of clay with 10% ash Fig.101.d. Consolidation curve of clay with 15% ash Fig.101.e. Consolidation curve of clay with 20% ash Fig.102. Variation of mechanical properties of fly ash polymer concrete with different wastes Fig.103. Density of the lightweight concrete with saw dust Fig.104. Variation of compressive strength of the lightweight concrete Fig.105. Variation of compressive strength with the density Fig.106. Variation of the flexural strength Fig.107. Variation of the split tensile strength Fig.108. Variation of flexural strength of polymer concrete Fig.109. Variation of flexural strength with the substitution Fig.110. Variation of split tensile strength of the polymer concrete Fig.111. Variation of split tensile strength function the substitution dosage

Ancuța Rotaru Habilitation Thesis

List of Tables

Chapter 1 Introduction: Unitary Methodology of Investigation Table 1. Check list 'Moisture problems' Table 2. Building defects in % of main origins

Chapter 2 Interaction of External Agents (Hazard Risks) Responsible for Building Decay or Failure Table 3. Landslide triggering conditions Table 4. Classification of landslides after velocity Table 5. Types of landslides (after Varnes, 1978, modified by Cruden and Varnes, 1996) Table 6. Geotechnical input data for the on-site layers Table 7. Stability factors for the stability analysis Table 8. Displacements for the stability analysis Table 9. The variation of efforts for maximal intervention calculus Table 10. Phenomena occurring to rock during earthquakes Table 11. North Dobruja earthquakes (in the last 30 years) Table 12. South Dobruja earthquakes (in the last century)

Chapter 3 Interaction of Soil/Rock Characteristics Responsible for Foundation Soil/Building Decay Table 13. Physical characteristics of Consolidated Undrained series of samples with constant water content tested in triaxial at different stages, group A-nc (SERIES I) Table 14. Physical indexes in different phases of modified triaxial tests with leakage, in stage I corresponding to drained test with constant suction and stage II corresponding to the shearing stage after leakage Table 15. Equations of failure planes for the failure criterion [(1´-3´)ult] in the {q: p: s} space Table 16. Shear test for σ´30 = 100 kPa, with dry samples followed by infiltration (water or leachate or gasoline) in soil type A-nc: stress values for different failure criteria Table 17. Hydrostatic level for different performed drillings

Chapter 4 Sustainable Development of Materials Used in Substructure Works Table 18. Chemical composition of fly ash from different types of coal Table 19. Chemical composition of fly ash from thermal power plant of Iași Table 20. Chemical composition of fly ash from thermal power plant of Suceava Table 21. Characteristics of fly ash from Iași thermal power plant Table 22. Chemical investigation of Suceava fly ash Table 23. Physical features of Iași fly ash Table 24. Physical features of Suceava fly ash Table 25. Compaction characteristics of Iași fly ash Table 26. Fly ash construction related applications Table 27. Sample dimensions based on Dmax

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards

Table 28. Rc compressive strength for fly ash mixture and lime Table 29. Physical characteristics of Iași fly ash stabilized natural ballast Table 30. The internal friction angle and cohesion Table 31. Tensile strength values Table 32. Non-admitted dosages for Iași fly ash Table 33. Mechanical characteristics Rc and Rtg for stabilized mixtures Table 34. The Rc/ Rtg ratio for normal strengthening versus Rc, Rtg for accelerated strengthening Table 35. Physical characteristics of natural aggregates Table 36. Physical characteristics of fly ash Table 37. Test timeline Table 38. Compressive strength for mixtures of aggregate-fly ash from Iaşi thermal power plant Table 39. Compressive strength for mixtures of aggregate-fly ash from Vaslui thermal power plant Table 40. Admissibility conditions Table 41. Chemical composition of the bituminous oil shale ash Table 42. Physical properties of unstabilized silty-sandy brown clay Table 43. Maximum dry unit weight/optimum moisture content, brown clay - different oil shale ash % Table 44. Compression index and swelling index of brown clay with different oil shale ash percentage Table 45. Experimental results on polymer concrete with different types of wastes

Ancuța Rotaru Habilitation Thesis

I. SYNTHESIS OF DIDACTIC AND SCIENTIFIC ACHIEVEMENTS

Synthesis of teaching outcomes I graduated from "Gheorghe Asachi" Technical University of Iași (The Polytechnic Institute of Iași), Faculty of Civil Engineering, the Civil, Industrial and Agricultural Constructions programme, in 1986. In 1997, after defending the thesis entitled Contributions on Stress State Particularities of Soil Masses Driven by Constructions at "Gheorghe Asachi" Technical University of Iaşi, supervisor Prof.Paulică Răileanu, PhD, I received a PhD in Civil Engineering – Geotechnics and Foundations. During 1995-1997, before being enrolled in the academic staff, I taught the discipline entitled Geotechnics and Foundations to students from the Technical College Nr.2, the Civil Engineering programme at “Gheorghe Asachi” Technical University from Iaşi. From 1998 to 2001, I taught yearly Geotechnics and Foundations to students from Technical College No.2, Geotechnics to students from the Civil Engineering programme (both in Romanian and English) and Foundations within the Railways, Roads and Bridges programme. From 2001 to 2004, I taught in the “concurrent position system” each academic year the course and practical courses on Engineering Geology to students from the Civil Engineering programme (both in Romanian and English) as well as practical courses in Geotechnics to students from the Civil Engineering programme (in English). From 2004 to 2007, I taught courses and practical works on Engineering Geology within the Civil Engineering programme in Romanian and English and practical lectures on Geotechnics in English. In 2007, through competition, I held a lecturer position in the Department of Infrastructure Transportation and Foundations at “Gheorghe Asachi” Technical University of Iaşi. From 2009 until the present, I am holding an associate professor position. I have given lectures and practical works as follows: Within the Bachelor programme: Course and practical applications on Engineering Geology, the 2nd year of study, the Civil Engineering Programme (in English); the lectures on Engineering Geology, the 2nd year of study, the Civil Engineering Programme (in Romanian); Geotechnics - practical applications, the 3rd year of study, the Civil Engineering Programme (both in Romanian and English); the course and laboratory on Special Foundations, the 4th year of study, the Civil Engineering Programme; Courses and laboratory on Special Issues on Geotechnics and Foundations, the 4th year of study within the Railways, Roads and Bridges Programme. Within the Master programme: Course and practical works on Complements of Engineering Geology, 1st year of study, the Geotechnical Engineering Programme; Courses and laboratory on Foundations for Special Constructions, the 2nd year of study, the Geotechnical Engineering Programme. The teaching activity materialized through the publication of 3 books as the first author, of which 1 specialized book as sole author, 1 course/textbook for university students as the first author, 1 laboratory guide as the first author: 1. Ancuţa Rotaru, Starea de tesiuni în masivele de pământ ce suportă construcţii, “Matei-Teiu Botez” Publishing House, Iaşi, 222 pp., 2008, ISBN 978-073-8955-48-6, (S1); 2. Ancuţa Rotaru, Paulică Răileanu, Elemente de geologie, “Matei-Teiu Botez” Publishing House, Iaşi, 281 pp., 2004, ISBN 973-7962-42-7 (M1); 3. Ancuţa Rotaru, Paulică Răileanu, Geotechnics – Laboratory Works, “Matei-Teiu Botez” Publishing House, Iaşi, 312 pp., 2004, ISBN 973-7962-51-6 (Î1). Book chapters: 4. Ancuţa Rotaru, Traian Dănuţ Babor, Basic Concepts and Methods of Probability in Geotechnical Engineering, Performance Based Engineering for 21st Century, Genki Yagawa, Masanori Kikuchi, Gabriela M. Atanasiu, Constantin Brătianu (eds.), Cermi Publishing House, Iaşi, pp. 342-348, 2004, ISBN 973-667-063-5. 5. Ancuţa Rotaru, Knowing the Complex of Consequences Produced by Earthquakes in order to Increase the Safety of Buildings, New Solutions for Essential Requirements in Buildings, Secu

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards

Alexandru, Adrian Radu (eds.), “Matei-Teiu Botez” Academic Society Poublishing House, Iaşi, pp.160-165, 2004, ISBN 973-7962-49-4. 6. Ancuţa Rotaru, Systems for the remediation of the Quality of the Contaminated Groundwater, New Solutions for Essential Requirements in Buildings, Secu Alexandru, Adrian Radu (eds.), “Matei-Teiu Botez” Academic Society Poublishing House, Iaşi, pp.174-182, 2004, ISBN 973- 7962-49-4.

Lectures on Geology, 2008, is a course taught in English on Engineering Geology for second-year students in the Civil Engineering Programme, 101 pages + 340 slides. I am the single author of that course posted on the website of the Faculty of Civil Engineering. http://ce.legacy.tuiasi.ro/ro/studenti/informatii-generale/resurse-online/ It strictly includes chapters on the Engineering Geology course and two original PowerPoint presentations, annexes to the chapter "Minerals". In 2010, I was part of the editorial staff of a WoS/ISI indexed book, and in 2020 I was the single editor of a book published by Springer Nature Publishing House: 1. Advances in Environmental and Geological Science and Engineering – Editors: Cornel Panait, Eugen Bârsan, Aida Bulucea, Nikos Mastorakis, Charles Long. Associate editors: Marius Mosoarcă, Ancuța Rotaru, 240 pp., Published by The World Scientific and Engineering Academy and Society Press (WSEAS Press), 2010, ISBN: 978-960-474-221-9; 2. Critical Thinking on Rehabilitation of the Built Environment (CRIT-RE-BUILT), Springer Series in Geomechanics and Geoengineering, Ancuţa Rotaru, Editor, 602 pg., Springer Nature Switzerland Publishing House, ISBN 978-3-030-61117-0, 2020. In my teaching activity, I have had psycho-pedagogical and methodical concerns perfecting myself on techniques and methods of teaching the latest concepts of conveying theoretical knowledge and practical experience to students. To improve the teaching methodology, I used multimedia teaching techniques during lectures, the presentation support being made available to students in electronic format. Throughout the years until the present, I coordinate students to elaborate on bachelor and dissertation theses. I am a member of the licence commission for the Civil Engineering Programme and dissertation commission for the Geotechnical Engineering Programme. I trained teams of students in designing, processing and supporting articles in student scientific communication sessions. To develop the teaching experience, I performed 17 Erasmus + KA103 teaching mobility internships (in EU countries), as follows: “Todor Kableshkov” University of Transport, Sofia, Bulgaria (2011), invited by Assoc. Prof. Chavdar Kolev; Technical University of Brno, Czech Republic (2011), invited by Assoc. Prof. Lumir Mica; „Aydin” University, Istanbul, Turkey (2012); University of Florence, Italy (2012); „Federico II” University of Neaples (2013) invited by Assoc. Prof. Massimo Ramondini, University of Padua (2013) invited by Prof. Paolo Simonini; Polytechnic University of Madrid (2014); University of Seville (2014) invited by Assoc. Prof. Victoria de Montes; University of Applied Sciences in Koln, Germany (2015) invited by Prof. Ansgar Neuenhofer; Nova University, Lisbon, Portugal (2015) invited by Assoc.Prof. Daniel Aelenei; University of Orléans, France (2016) invited by Prof. Dashnor Hoxha, North University in Varaždin, Croatia (2016) invited by lecturer Aleksej Aniskin, ENTPE Lyon, France (2017) invited by Prof. Henry Wong, University of Parma (2017) invited by Assoc. Prof. Andrea Segalini, University of Brescia, Italia (2018) invited by Prof. Roco Lagioia, University of Lille, France (2018) invited by Prof. Isam Shahrour, University of Beira Interior (2019) invited by Assoc. Prof. Luis Pais. Within the Erasmus + KA107 program with non-EU countries, I carried out 13 mobilities: Andres Bello University of Santiago, Chile (2017) invited by Assoc. Prof. Mauricio Toledo; Kathmandu University, Dhulikhel, Nepal (2017, 2018) invited by Assoc. Prof. Prachand Man Pradhan, American University of Madaba, Jordan (2017) invited by Assoc. Prof. Monther Abdelhadi, University of Pretoria, South Africa (2017, 2019 ) invited by Prof. Wynand Steyn, Tsinghua University, Beijing, China (2018) invited by Prof. Liming Hu, Mohammed V University, Rabat, Morocco (2018, 2019) invited by Prof. Toufik Cherradi, Indian Institute of Technology Madras, Chennai , India (2018) invited by Prof. Rajagopal Karpurapu, Bombay Indian Institute of Technology, Mumbai, India (2019) invited

Ancuța Rotaru Habilitation Thesis by Prof. Devendra Narain Singh; Atma Jaya Yogyakarta University, Indonesia (2019) invited by Prof. Yoyong Arfiadi; Mutah University, Kerak, Jordan (2019) invited by Prof. Tayel El-Hasan.

In the last 6 academic years, I coordinated the Erasmus+ mobility for students from Technical University of Iași, the Faculty of Civil Engineering and Building Services, to University of Seville (2 students in 2019/2020), Brno University of Technology (1 student in 2018/2019, 2 students in 2017/2018, 1 student in 2016/2017, 1 student in 2015/2016, 3 students in 2014/2015), Polytechnic University of Madrid (2 students in 2015/2016), University of Parma (2 students 2016/2017), “Andres Bello” University of Santiago de Chile (1 student in 2018/2019). As a programme coordinator, I coordinated students’ Erasmus+ mobility for studies from partner universities at the Technical University of Iași, Faculty of Civil Engineering and Building Services, as follows: from the Polytechnic University of Madrid (2 students in 2018/2019), from the University of Seville (1 student in 2018/2019, 1 student in 2016/2017), from the University of Burgos (2 students in 2015/2016), from the American University of Madaba, Jordan (2 students in 2016/2017, 2 students in 2018/2019), from Epoka University, Tirana, Albania (2 students in 2017/2018), from Mohammed V University, Rabat, Morocco (3 doctoral students in 2018/2019), from the University Atma Jaya Yogyakarta, Indonesia (1 student in 2017/2018).

Also as an Erasmus+ KA103 coordinator, I hosted at my Faculty academics from universities within the EU area giving lectures to our students, but also academics from countries outside EU (E+KA107) as follows: Assoc. Prof. Mauricio Javier Toledo Villegas, University Andres Bello, Santiago de Chile (2016), Assoc. Prof. Monther Abdelrahman Abdelhadi (2017, 2018, 2019) and Assal Haddad (2017, 2019) and Osamah Menwer Yacoub Haddad (2019) from the American University of Madaba, Jordan, Prof. Wynand JvdM Steyn (2017, 2019), Lecturer Sarah Skorpen (2018), Prof. Barend Wilhelm Janse Rensburg and Prof. Chris Roth (2019) from the University of Pretoria, South Africa, Assoc. Prof. Qingbo Wen (2018) from Tsingua University, Beijing, China, Assoc. Prof. Prachand Man Pradhan (2018) and Prof. Ramesh Kumar Maskey (2019) from Kathmandu University, Dhulikhel, Nepal, Yoyong Arfiadi (2018, 2019) and Luky Handoko (2019) from the University Atma Jaya Yogyakarta, Indonesia, Huseyin Bilgin and Lecturer Julinda Keçi (2018), lecturer Enea Mustafaraj (2019) from Epoka University, Albania, Prof. Taoufik Cherradi (2018, 2019) and Assoc. Prof. Youssef Ajdor (2018) from the University Mohammed V, Rabat, Morocco, Prof. Guoqing Cai and Chenggang Zhao (2019) from Beijing Jiaotong University, China, Assoc. Prof. Gerardo Hernandez Gomez and Lecturer David Villalobos (2019) from Fidelitas University, San Jose, Costa Rica, Prof. Manuel Ruiz Sandoval (2019) from the Metropolitan Autonomous University, Mexico, Assoc. Prof. Pham Huy Giao (2019) from Asian Institute of Technology, Thailand, Assoc. Prof. Nguyen Tai and Assoc. Prof. Tran Vu Tu from Ho Chi Ming City University of Technology and Education, Vietnam. Their lectures were a great way to inspire our students, the professionals of tomorrow. Moreover, they built a strong feeling of trust and a strong professional network improving the knowledge transfer to students.

Synthesis of research/scientific outcomes Research activity I am with the research team of the Faculty of Civil Engineering within the “Gheorghe Asachi” Technical University of Iași. My topics of interest aim to reduce the risk of landslides and earthquakes in the built environment, optimize the foundation soils thorough research on soil properties, sustainable and rehabilitation of infrastructure by using recyclable materials in concrete or improving foundation soils. The research activity was materialized through a series of international and national projects. In the following, I only mention the 5 of them for which I was the Manager. They are the following:  2018 - present – Manager of the project Rehabilitation of the Built Environment in the Context of Smart City and Sustainable Development Concepts for Knowledge Transfer and Lifelong Learning (RE-BUILT) – strategic partnership with European Universities: University of Natural Resources and Life Sciences (BOKU) Vienna (Austria), Brno University of Technology (Czech Republic), University of Orléans (France), University of South Lazio and Cassino (Italy), University of Seville, Spain, NOVA University (Portugal), University of Maribor (Sovenia), University of Transport Todor Kableshkov, Sofia (Bulgaria).

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards

 2010 - 2011 – Executive Manager of the CUANTUMDOC Project for the application of managerial, research and didactic strategies assigned to improve the training of future researchers through the doctoral studies programme.  In 2009, I won through national competition the project Landslide Risk Mitigation: Challenge and Strategy, Contract PNCDI II Exploratory Workshop no.17WE/2009, Beneficiary M.E.C., in which I was the Manager.  In 2008, I won through national competition the project Some Aspects of Landslide Risk Evaluation Taking into Account Their Distribution and Properties, PNII Contract, Human Resources Programme, MC project, CNCSIS Code 31/March 2008, Beneficiary M.E.C.  In 2005 and 2006, I won, through CNCSIS national Grant competition, the Grant entitled Procedures and Technologies for Improving the Properties of Difficult Foundation Soils To Increase the Safety and Sustainability of Construction Infrastructure, Grant M.E.C. type A, no. 27637/2005, Theme 49, code CNCSIS 547 and Grant M.E.C. type A, no. A1 GR164/2006, theme 70, code CNCSIS 547, being the Manager of the project.

Scientific activity The scientific activity has materialized through a series of publications and communications, both nationally and internationally. I have elaborated 122 scientific papers published in national and international specialized journals and volumes containing studies and articles of national and international conferences (Romanian Journal of Materials, Environmental Engineering and Management Journal, Journal of Applied Science and Engineering, Proceedia Manufacturing, Advances in Science, Technology and Engineering Systems Journal, Advanced Engineering Forum, Environmental Problems and Development – Energy and Environmental Engineering Series; Australian Journal of Basic and Applied Sciences; Journal of Materials, Methods and Technologies; International Journal of Geology) and national (Acta Technica Napocensis, UT Cluj-Napoca, Revista de Politică şi Scientometrie, Revista Intersecţii/Intersections, Buletinul Institutului Politehnic din Iaşi, section VI, Construction. Architecture, Annals of „Ovidius”University, Constanţa, etc.) in the field of geotechnics and foundations or in the proceedings of international congresses, conferences and symposia (International Conference CRIT-RE-BUILT, Iași; International Conference on Smart City Applications, Casablanca, Maroc; International Conference ”Tradition and Innovation - 65 Years of Constructions in Transilvania”, Cluj-Napoca; International Conference Environmental and Geological Science and Engineering, Constanța; International Geotechnical Conference „Development of Urban Areas and Geotechnical Engineering” – Saint Petersburg; Jubilee International Scientific Conference VSU, Sofia, Bulgaria; International PIARC Seminar „Adapting Road Earthworks to the Local Environment”, Iaşi, Romania; 3rd International Symposium on Environment, Athens, Greece, International Conference „Probleme actuale ale urbanismului şi amenajării teritoriului”, Chişinău, etc.) and nationals (“55 de ani de învăţământ superior de construcţii la Cluj-Napoca”, May 2008, The XIth National Conference on Geotehnics and Fundations, Timişoara, September 2008, CIB 2008, Braşov, November 2008; International PIARC Seminar „Adapting Road Earthworks to the Local Environment”, Iaşi, May-June 2007, National Conferences on Geotehnics and Fundations, Iaşi, 1996, Cluj, 2000, Bucureşti, 2004; Tehnomil Sibiu, 2001, other national conferences held in Timişoara 2001, Braşov 2004, Constanţa 2004, Iaşi 2004, Bucureşti 2004, Chişinău, Republica Moldova 2004, Sofia, Bulgaria 2004, etc. (see the References). Scientific papers can be grouped as follows: • 11 ISI articles; • 33 BDI articles; • 52 articles in B/B+ journals/books. • 3 posters presented at international scientific events. The habilitation thesis cites 87 scientific papers whose author/co-author I am (see the References). Of these, the most representative scientific papers are cited below. 1. Ancuţa Rotaru, Vasile Boboc, Nicolae Țăranu, Monther Abdelhadi, Andrei Boboc, Oana-Mihaela Banu, 2019, The compressive behaviour of aggregates cemented with fly ash collected from coal-fired power plants, Romanian Journal of Materials, 49(1): 141-147.

Ancuța Rotaru Habilitation Thesis

2. Monther Abdelhadi, Ancuța Rotaru, Nafeth Abdel Hadi, Nicolae Țăranu, Andrei Boboc, Oana Mihaela Banu, The Influence of Bituminous Oil Shale Ashes on the Characteristics of Stabilized Silty-sandy Brown Clays, Romanian Journal of Materials, 49(4): 581-590. 3. Monther Abdelhadi, Ancuța Rotaru, Maria Gavrilescu, Nicolae Țăranu, 2018, Compressive Strength Analysis on Problematic Soils Stabilized with Fly Ash in Jordan, Environmental Engineering & Management Journal (EEMJ) 17(8): 1855-1861. 4. Ancuţa Rotaru, Chavdar Kolev, 2010, Addressing Issues of Geoenvironmental Risks in Dobruja, Romania/Bulgaria, Environmental Engineering and Management Journal (EEMJ), 9(7): 961-969. 5. Ancuţa Rotaru, Paulică Răileanu, 2008, Groundwater contamination from waste storage works, Environmental Engineering and Management Journal, 7(6): 731-735, Editura EcoZONE. 6. Ancuţa Rotaru, Some Geo-aspects of the Black Sea Basin, 2010, Poceedings of the 3rd International Conference on Environmental and Geological Science and Engineering (EG '10), Constanța Maritime University (CMU), 3-5 September 2010, Constanța, in Advances in Environmental and Geological Science and Engineering, Published by World Scientific and Engineering Academy and Society Press (WSEAS Press), pp.169-174, ISSN: 1792-4685, ISBN: 978-960-474-221-9. 7. Ancuţa Rotaru, Daniel Oajdea, Paulică Răileanu, 2007, Analysis of the landslide movements, International Journal of Geology, NAUN, 1(3) 70-79. 8. Ancuţa Rotaru, Gupinath Bhandari, 2017, Bridging New Solutions for Sustainable Rehabilitation of Structures Damaged Due to Difficult Soils or Foundation Design, Advanced Engineering Forum, Proceedings of EBUILT International Conference, November 16-19, 2016, Iași, Romania, 21: 346- 351. 9. Ancuţa Rotaru, Vasile Boboc, 2010, Physical Properties of Pozzolana Fly Ash from Thermal Power Plant of Iasi, Romania – A Cement-like Material for Substructure Works, – Recent Advances in Risk Management, Assessment and Mitigation, Poceedings of the International Conference on Risk Management, Assessment and Mitigation (RIMA’10), Universitatea Politehnica, Bucharest, Romania, April 20-22, 2010, in Recent Advances in Electrical Engineering Published by World Scientific and Engineering Academy and Society Press (WSEAS Press), 187-193, ISSN: 1790-2769, ISBN: 978-960-474-182-3. 10. Ancuţa Rotaru, Vasile Boboc, 2010, A Material Used in Substructure and Road Works: Physical Characteristics of Pozzolana Fly Ash from Thermal Power Plant of Iași, Romania, WSEAS Transactions on Environment and Development, Volume 6(6): 427-436, ISSN: 1790-5079. 11. Vasile Boboc, Ancuţa Rotaru, Andrei Boboc, 2010, A Material for Substructure and Road Works: Mechanical Characteristics of Pozzolana Fly Ash from Thermal Power Plant of Iași, Romania, WSEAS Transactions on Environment and Development, 6(6): 437-446, ISSN: 1790-5079. 12. Ancuţa Rotaru, Paulică Răileanu, 2009, Some Models of Soil Behaviour for Evaluation of Consolidation Settlement in Clays, Proceedings of the 17th International Conference on Soil Mechanics and Geotechnical Engineering, Alexandria, Egypt, October 5-9, 2009, Published by IOS Press under the imprint Millpress, ISBN 978-1-60750-031-5 (print). 13. Ancuţa Rotaru, 2008, Quality control and remediation of contaminated soils in urban areas–some examples from Romania, Australian Journal of Basic and Applied Sciences, 2(4): 929-938. 14. Costel Pleşcan, Ancuţa Rotaru, 2010, Aspects Concerning the Improvement of Soils against Liquefaction, Buletinul Institutului Politehnic din Iași, Universitatea Tehnică „Gheorghe Asachi” din Iaşi, Tomul LVI (LX), Fasc. 3, Secţia Construcții. Arhitectură, 39-45.

Synthesis of recognition and impact of the activity It is materialized through a series of activities carried out successfully over time, the most important of which being the following:  Member in editorial boards: American Journal of Civil Engineering, International Research Journal on Advanced Research Hub, Recent Advances in Environmental and Biological Engineering, Recent Research in Urban Sustainability, Architecture and Structure, World Academy of Science, Engineering and Technology (Civil and Environmental Engineering).  Reviewer for international journals: Geomechanics and Geoengineering (ISI, EBSCO, Scopus); Challenge Journal of Structural Mechanics; African Journal of Engineering Research; Athens

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards

Journals; Environmental Geotechnics; WSEAS journals Recent Advances in Civil and Mining Engineering; Recent Advances in Environmental and Biological Engineering; Recent Researches in Urban Sustainability, Architecture and Structures; Recent Advances in Energy, Environment and Geology; Advances in Environmental Development, Geomatics Engineering and Tourism; Recent Advances in Geodesy and Geomatics Engineering, Mathematics and Computers in Contemporary Science.  Member in over 150 international scientific committees of which: ISI: 1st International Conference on Tourism and Economic Development (TEDE'13) Nanjing, China November 17- 19, 2013; 2nd European Conference of Geodesy & Geomatics Engineering (GENG'14) Brașov, România June 26-28, 2014, 3rd International Conference on Sustainable Cities, Urban Sustainability and Transportation (SCUST'14) Istanbul, Turkey December 15-17, 2014; 1st International Conference on New Directions in Business, Management, Finance and Economics (ICNDBM 2013), Famagusta, Northern Cyprus. BDI: International Conference on Critical Thinking in Sustainable Rehabilitation and Risk Management of the Built Environment – CRIT-RE-BUILT – Iași, 7-9 November 2019, president of the scientific committee; International Conference – Towards a Sustainable Built Environment EBUILT, 2016, Iași. WASET - International Scientific Committee of Civil and Environmental Engineering.  Invited Profesor: Technical University of Vienna (2006); National and Kapodistrian University of Athens (2006); Roma Tre University of Rome (2006); BOKU University, Vienna, Austria (2011, CUANTUMDOC); Erasmus+ KA103: „Todor Kableshkov” University of Transport, Sofia, Bulgaria (2011); Technical University of Brno, Czech Republic (2011); „Aydin” University of Istanbul, Turkey (2012); University of Florence, Italy (2012); „Federico II” University of Neaples, Italy (2013), University of Padova, Italy (2013); Polytechnic University of Madrid, Spain (2014); University of Seville, Spain (2014); University of Applied Sciences, Koln, Germany (2015); Nova University, Lisbon, Portugal (2015); University of Orléans, France (2016), North University, Vraždin, Croatia (2016), ENTPE Lyon, France (2017), Universitaty of Parma, Italy (2017), University of Brescia, Italy (2018), University of Lille, France (2018), University of Beira Interior (2019); Erasmus+ KA107: University Andres Bello Santiago de Chile, Chile (2017); University Kathmandu, Dhulikhel, Nepal (2017, 2018), American University of Madaba, Jordan (2017, 2019), University of Pretoria, South Africa (2017, 2019), Tsinghua University, Beijing, China (2018), UniversitY Mohammed V, Rabat, Marocco (2018, 2019), Indian Institute of Technology Madras, Chennai, India (2018), Indian Institute of Technology Bombay, Mumbai, India (2019); Atma Jaya University Yogyakarta, Indonesia (2019); Mutah University, Kerak, Jordan (2019); RE-BUILT: BOKU University, Vienna, Austria (2019); „Todor Kableshkov” University of Transport, Sofia, Bulgaria (2020).  Erasmus+ Coordinator. KA103: University fur Bodenkultur (BOKU) Vienna, Austria – 2011/2014, Graz University of Technology, Graz, Austria – 2012/2013, ”Todor Kableshkov” University of Transport Sofia, Bulgaria – 2010/2014; 2015/2021, Brno University of Technology, Brno, Czech Republic – 2011/2014; 2014/2021, University of Cyprus, Nicosia, Cipru – 2011/2014; 2015/2021, Universite Lille 1, Lille, France – 2011/2014; 2015/2021, „Pierre and Marie Curie” University, Paris, France – 2011/2013, Universite de Poitiers, Poitiers, France – 2011/2014, Technische Universitat Dresden, Dresda, Germany – 2011/2014; 2014/2021, Fachhochschule Koln, Koln, Germany – 2011/2014; 2014/2021, Universita degli Studi della Basilicata, Potenza, Italy 2011/2013, Universita degli Studi di Bergamo, Bergamo, Italy – 2012/2014, Universita degli Studi di Brescia, Brescia, Italy – 2012/2014; 2014/2021, Universita degli Studi di Cassino, Cassino, Italy – 2011/2014; 2014/2021, Universita degli Studi di Catania, Catania, Italy – 2012/2013, Universita degli Studi di Firenze, Florenta, Italy – 2012/2014; 2014/2021, Universita degli Studi di Molise, Termoli, Italy – 2012/2014; 2014/2021, Universita degli Studi di Napoli „Federico II”, Napoli, Italy – 2011/2015, Secunda Universita degli Studi di Napoli, Napoli, Italy – 2011/2014; 2015/2021, Universita degli Studi di Padova, Padova, Italy – 2012/2014; 2014/2021, Universita degli Studi di Salerno, Salerno, Italy – 2011/2014, Instituto Politécnico de Castelo Branco, Castelo Branco, Portugal – 2011/2013; 2015/2021, Universidade de Coimbra, Coimbra, Portugal – 2013/2014, Universidade da Beira Interior, Covilhã, Portugal – 2011/2014; 2016/2021, University of

Ancuța Rotaru Habilitation Thesis

Maribor, Maribor, Slovenia – 2011-2014; 2015/2021, Universidad de Burgos, Burgos, Spain – 2012/2014; 2014/2021, Universidad de Castilla la Mancha, Ciudad Real, Spain – 2011/2012; 2015/2021, Universidad de La Coruna, La Coruna, Spain – 2011/2014, Universidad Politecnica de Madrid, Spain – 2011/2014; 2014/2021, Universidad de Sevilla, Sevilla, Spain – 2011/2014; 2014/2021, Universidad Politecnica di Valencia, Valencia, Spain – 2011/2013, Izmir Yuksek Teknoloji Enstitusu, Izmir, Turkey – 2011/2014; 2015/2021, Yeditepe Universitesi, Istanbul, Turkey – 2013/2014; 2015/2021, Istanbul „Aydin” Universitesi, Istanbul, Turkey – 2013/2014; 2015/2021, Middle East Technical University, Ankara, Turkey – 2011/2013; 2015/2021, Universita degli Studi di Parma, Italy 2015/2021, University North, Vrazdin, Croatia 2015/2021, ENTPE, Vaulx en Velin (Lyon), France 2015/2021. KA107: Indian Institute of Technology Bombay, Mumbai, India 2016/2021, Indian Institute of Technology Madras, Chennai, India 2016/2021, Jadavpur University, Kolkata, India 2016/2021, Tsinghua University, Beijing, China 2016/2021, Jiaotong University, Beijing, China 2016/2021, Universidad Adolfo Ibanez, Santiago de Chile, Chile 2016/2021, Universidad Andres Bello, Santiago de Chile, Chile 2016/2021, Kathmandu University, Dhulikhel, Nepal 2016/2021, American University of Madaba, Madaba, Jordan 2016/2021, University of Pretoria, Pretoria, South Africa 2016/2021, Mohammed 5 University, Rabat, Morocco 2016/2021, Universidad Autonoma Metropolitana, Mexico City, Mexico 2016/2021, University Epoka Tirana, Albania 2016/2021, Universidad Fidelitas San Jose, Costa Rica 2016/2021; Universitas Atma Jaya, Yogyakarta, Indonesia, 2017/2021; University of Lima, Peru, 2018/2021; Universitas Pelita Harapan, Jakarta, Indonesia, 2018/2021; Georgian Technical University, 2018/2021; Misr University for Science and Technology, 6th of October City, Egypt, 2018/2021; Pontificia Universidad Catolica de Chile, Santiago de Chile, Chile, 2018/2021.  Main organizer of international conferences and chair person: ISI - International Conference Risk Management, Assessment and Mitigation (RIMA'10), Bucharest, Romania, April 20-22, 2010 – Special Session Sustainable Civil Engineering; BDI - International Conference – Towards a Sustainable Built Environment EBUILT, 2016, Iași, Romania; International Conference on Critical Thinking in Sustainable Rehabilitation and Risk Management of the Built Environment – CRIT-RE-BUILT – Iași, Romania, November 7-9 2019 (President).  Main organizer of international workshops: Landslide Risk Mitigation: Challenge and Strategy – Iași, Romania, October 28-30, 2009 (Project Director); Sustainability and Perspectives on Geotechnical Engineering Workshop – November 14, 2016, Iași, Romania; Integrating Structures into the Built Environment for Sustainable Development – June 19, 2019, Iași, România; Rehabilitation Challenges and Solutions in the Built Environment – November 5-11, 2019, Iași, Romania.  CNCSIS ISI paper award for „Groundwater Contamination from Waste Storage Works”, Environmental Engineering and Management Journal, EcoZONE Publishing House, ISSN: 1582-9596, 7(6), November/December 2008.

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards

II. DESCRIPTION OF SCIENTIFIC CONTRIBUTIONS 1. INTRODUCTION: UNITARY METHODOLOGY OF INVESTIGATION

There are many defect investigators and many types of defects for a building so that various investigation procedures and methods exist. An investigation method is dependent on the expertise and investigator viewpoint and the nature of the defect. Also, for identical defects, various investigators may decide on alternative approaches built sometimes to different conclusions [43]. The latter aspect, for existing symptoms of defects, must be avoided [42]. It emphasises the need for science like building pathology, and for its use by experts. It makes sense to present a basic investigation process, which gives the essentials of a systematic approach for dealing with the defect of a building [23]. The investigation process represents a synthesis of all logic elements, which play distinct roles in the diagnosis and analysis of defects. This process flow does not pretend to give something new. It is just an attempt to indicate logic steps in the investigation process. The diagnostic process starts from the observation of a failure or acknowledgement of anomalies indicating the presence of either a defect or an initial failure. The diagnostic process develops so as to deal with and methodically analyse all the diagnostic possibilities, which may somehow be related to the failure itself. The analysis of the anomalies that may be found in the building represents a strategic stage in the diagnostic activity. In fact, if they are interpreted as symptoms, this will allow for a pre- acknowledgement of the defects which have caused the failure. Subsequent confirmation of the pre- diagnostic conjectures based on a more accurate survey and elimination of unsuitable conjectures lead to a degree of certainty of the sub-group of established diagnoses. The presence of different possible diagnoses must be considered at the prequalification stage. Diagnostics, if correctly applied and supported by adequate tools (operative and methodological) can optimise the prequalification procedures. Where the survey stage completes in only one visit, collected information can be redundant because establishing what is relevant to the failure before analysing the data could be difficult. It is therefore preferable wherever possible, to iterate the survey stage so that later examinations can be used to test the developing diagnosis.

1.1. THE DIAGNOSTIC PROCESS AND ITS TOOLS Fig.1 presents the investigation process. Solid boxes and arrows represent the main process flow, and the additional 'tools' appear alongside. The concept 'anomalies' designates that signs or symptoms first observed may not always be reliable indicators.

Fig.1. The investigation process

Ancuța Rotaru Habilitation Thesis

Fig.2. The diagnostic process and its tools

Many variations of this diagram depend on the scope and details of the investigation concerned. An example of a slightly different representation, called 'the diagnostic process' is given in Fig.2. The

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards diagnostic process starts from the failure observation or acknowledgement of anomalies that indicate a defect or incipient failure. The diagnostic process develops to methodically analyze all the diagnostic possibilities which may relate to failing. The analysis of the anomalies found in the building represents a strategic stage in the diagnostic activity. If interpreted as symptoms, this will allow for a pre-acknowledgement of the defects which have caused the failure. When dealing with a specific defect – or better: an anomaly indicating a possible error – checking the list can play an important role. That may concern the different aspects, which call a list of possible symptoms to be cheeked, or a list of instruments or measuring devices. A defect might be structural, non-structural or combined. A structural defect means insufficient safety that cannot be observed or measured directly. It is evaluated by calculations, based on material properties, strength criteria, loads, dimensions and other attributes. The term as 'probability of failure' expresses safety [265]. Also, such a probability of failure must be related to some acceptable risk. That belongs to the domain of a structural engineer, acquainted with probabilistic approaches. In reality, the investigation is a decision-making process that might also be influenced by disturbing factors like time-pressures, missing or unrecoverable information and irrationalities. That implies that the investigator faces uncertainties and handle them in some probabilistic way [165].

1.2. CAUSE DETERMINATION The cause of a defect should identify itself to adopt the necessary effective measures. But where does the 'tracing back' stop? In most cases, any event or situation is the consequence of some previous event. That leads inevitably to a conclusion about imperfect human behaviour or knowledge but does not imply that humans are always to blame. Assuming that use of results leads to the analysis of cause(s), three types of cause descriptions limit the in-depth search: - technique-oriented reports (What caused the defect?) - liability-oriented information (Who caused the deficiency?) - system-oriented descriptions (How did the defect originate?).

Table 1. Check list 'Moisture problems' AIR HUMIDITY RISING RAIN WATER SOURCES -people -ground water -rain water (direct) -cooking -rain water -rain water (indirect) -space under ground floor -distinct moisture front -leakage -gas water-heater from below -snow -building moisture -mould on furniture -condensation (frequently showing) on double glazing INDICATIONS & -mould or wet spots on -timber rot (floor joints) -distinct relation with ANOMALIES structure also at the interior wall rain (especially driving -mould in cupboards is rain) -poor functioning or poor efflorescence -solid walls design of ventilation system at moisture (masonry) poor -filthy ventilation system -high ground pointing -wrong use of ventilation water level -wrongly placed cavity system -poor drainage -presence of salts CAUSES OR -masonry foundation -poorly executed anchors STIMULATING without moisture or designed details CONDITIONS barrier (damp proof cavity walls with course) imperfections of -lime mortar, used in insulation material masonry -cavity walls filled with insulation slabs (open joints)

Ancuța Rotaru Habilitation Thesis

A technique-oriented description of causes allows the formulation of technical measures, which cure or prevent an identical defect. Apart from the direct interests of involved parties, this type of information may well be of interest to building participants. A liability-oriented description imposes by reasons of liability and insurance. The investigator should devote particular attention to objective evidence, and keeping also in mind those technical descriptions must be well understood and unambiguous. Table 1 gives a representative but not a detailed example. A system-oriented description is needed when causes of defects need to be the input for quality assurance (QA) in the building process. Representing a tool for managing efficiently and effectively a process, QA represents the strength in preventing defects. But QA is system-oriented: it deals in a managerial way with systems that aim at controlling matters like organisation, resources, communication, information, means, human resources, motivation, and systematic feedback. That implies that the output of building pathology – i.e. causes of defects – should be described in terms of system failures useful as input to QA. The conception that building defects arise from procedural diversity shapes the thinking about causes of lacks. This way of looking at the causes of defects is unadopted. The way of going to the 'source' of a defect very much depends on its nature. In most cases, the determination process will follow some strategy of assessing possible causes, setting hypotheses and rejecting or adopting these hypotheses based on facts. Such a method is quite close to the more or less formalized method of the so-called fault tree analysis, known from (industrial) processes and reliability analysis of structures [22].

1.3. ORIGINS OF CAUSES It might be interesting to know where building defects originate during the building process. Table 2 gives some findings. The manifestation of the defects does not necessarily coincide with the time of origin. These data are a reasonably indicative, but they are of limited values because the types of errors are unspecified. It emphasises that preventive measures at the level of improved quality management of the building process are needed. The observation that 'the material' represents the origin of possible defects (Table 2) illustrates this aspect. But, the material is as it is and can never be the culprit. There must be other causes leading to 'the wrong material'. This report primarily considers the technical aspects of building defects. But one should not overlook that the origins of defects are essentially lack of knowledge, know-how, information and communication. Table 2. Building defects in % of main origins COUNTRY design execution material use Unknown Finland 10 France 30 60 10 Germany 40 40 20 Great Britain 40 50 10 Netherlands 40 35 10 10 5 Norway 45 40 15

USA 50 25 15 10 average 41 42 15 Czech Republic 5 70 25 Hungary 20 38 42 Poland 15 63 22 average 13 57 30

1.4. THE DECAY PROCESS AND MAINTENANCE Diagnosis, which is the fundamental part of the building pathology discipline, requires the knowledge of the decay process suffered by the building components. This process defines the evolution from a performance to a non-performance condition. The pathological decay always starts with one or more errors (Fig.3) committed during the building process stages. But errors committed during design or construction cause defects. These deficits can either stay in a latent form or manifest themselves by the

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards action of external agents. Interaction between external agents and losses represents the necessary condition for decay evidence as a failure. The failure in building elements can be structural, i.e. loss of several characteristics (physical, chemical or technological). Or it can be a performance failure, i.e. the drop of the initial performance level below an established tolerable limit. Or — finally and most commonly — it may concern both aspects. Under these terms, the evidence (called the anomaly) by which the building user becomes aware of a failure may involve both the structural and performance aspects.

Fig.3. The decay process

The decay process needs time to develop, and it does not directly cause components to pass from a performance to a failure condition. That is relevant to the possibility of planning maintenance strategies with a preventive purpose. Anomalies mostly manifest themselves before the ultimate failure occurs. They become somewhat a symptom pointing at one or more (possible) defects. To examine anomalies seems a more convenient way to set up a maintenance programme than to base it on the knowledge of time-dependent parameters of reliability, duration of service life, mean time between failure, which is harder to obtain.

1.5. PREMISES Consequently, if the correct diagnosis of an occurred failure is an essential condition to carry out an effective emergency maintenance strategy, the possibility of an accurate acknowledgement of anomalies - when the collapse has not yet occurred - is fundamental to preventive maintenance planning. Finally, as a consequence of the failure, the (economic) damage appears at the end of the process. Hereafter, the thesis analyzes how external agents (hazard risks) interact with the foundation soil producing instability transmitted to the structure in the form of defects or even failure. It also studies the soil physical and mechanical characteristics. They do not always bring stability and safety to the structure but often transmits defects. Finally, the thesis analyses some ecological materials. They are wastes from processing raw materials. They can either improve the foundation soil characteristics or behave as a binder replacing the cement in concrete for sustainable rehabilitation works. The benefit is the cost, but primarily the use of polluted waste releasing the built environment.

Ancuța Rotaru Habilitation Thesis

2. INTERACTION OF EXTERNAL AGENTS (HAZARD RISKS) RESPONSIBLE FOR BUILDING DECAY OR FAILURE

2.1. LANDSLIDES Despite frequent landslide events and constant efforts to develop effective early warning systems, considerable gaps remain in modelling the triggering mechanisms, the spatial extension of scars and deposition zones [84]. Understanding the causes of slope development, particularly the initiation of movement, requires knowledge of a set of factors, usually associated with groundwater, that are often difficult to determine. Landslides or slope movements are complex natural phenomena which represent a significant hazard in many countries performing a leading role in the evolution of landforms [285]. Many factors such as soil or rock types, bedding planes, topography and moisture content control these phenomena. Landslides cause damages, injuries and death and affect a broad range of resources. Water availability, quantity, quality and supplies, forests, dams and roadways can be affected for years after a slide event. The obstructive economic effects of landslides include the cost to repair structures, loss of property, disruption of transportation routes, medical fees in the event of injury, and indirect costs. Landslides commonly occur as a result of: heavy rainfall, rapid snowmelt, wet winter and spring particularly if previous years were also wet, the removing of the material from the base, loads material at the top, earthquakes, erosion, poor forest management, addition of water to a slope from irrigation, roof downspouts, poor drainage, septic-tank effluent, canal leakage, or broken water. A continuous recording of landslide displacements is often required in order to better understand the complex relationship between the triggering factors and the dynamics of the movement (Fig.4). In recent years, structural geology has been used as a tool to investigate the development and evolution of potential rockslides. The recognition of the processes that triggered the movement is of primary importance to understand the landslide mechanisms. The study analyses the movement of landslides from the point of view of different stages of landslide activity: pre-failure, failure, post-failure stages and reactivation stage. Landslides represent a severe issue almost in all parts of the world because they cause economic or social losses on private and public properties. Landslides demonstrated the destructive power of sudden movements of soil masses claiming lives and causing substantial damage to property and infrastructure on an annual basis [71]. The term „landslide” describes all types of gravitational movements of the earth material. The term landslide indicates “the movement of a mass of rocks, earth or debris down a slope” [84]. Nevertheless, landslides classify according to a variety of types and velocities of movement. Fig.4. Shear resistance vs shear force during a The landslide represents a natural landslide movement process, or it occurs as a result of human activities which disturb the slope stability. These phenomena differ in shape, size of the displaced mass, moving mechanisms and velocity. They can occur on any ground according to the specific conditions of soil, moisture, and slope angle. As a natural process, landslides serve to redistribute soil and sediments developing either in abrupt collapses or in gradual slides. Springs in unwetted areas, cracks in street pavements, tilting concrete floors, broken water lines, leaning retaining walls, sunken roadbeds or water level decreases may anticipate severe landslides. [98].

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards

Slope movements can take various configurations, from toppling to mudflow. They can involve a variety of materials from hard rock to sensitive clay or loess [89]. They can result from a variety of phenomena from rapid snowmelt or excessive rainfall to earthquakes. Factors affecting landslides are geophysical or human-made so that landslides can occur in developed or undeveloped areas or areas with the altered ground by roads, houses, utilities or buildings [68], [101]. Areas prone to landslides locate at the base or on top of slopes of previous or recent landslides, fills, steep cut slopes or minor drainage hollows. Safe areas of landslides are on hard, non-jointed bedrocks which have not moved in the past, on relatively flat-lying zones away from slopes and steep river banks. Landslides represent an extensive geologic hazard because they are widespread, occur all over the world, and cause critical damages and fatalities each year. However, the mitigation of the enormous damage that landslides cause is acquirable. Landslide risk may reduce by engineering and geoscience investigations; yet, geotechnical studies and projects to assess and stabilize potentially vulnerable sites are costly. Landslides also pose significant threats to highways and structures in general. Expansion of urban and recreational developments into hillside areas results in ever-increasing numbers of residential and commercial properties that are threatened by landslides. By geological mapping, detecting slope hazards and assessing the likelihood of landslide incidence, geoscientists can assist engineers, developers, planners and building inspectors in avoiding high-risk areas [287]. Through this process, structures like homes, schools, hospitals, power-lines, fire stations and roads can safely locate away from potential landslide risk areas. The primary objective is to reduce long-term losses by improving the understanding of causes of ground failure and suggesting mitigation strategies. Growth of urban areas has increased the incidence of landslide disasters, but landslides commonly occur in connection with other major natural disasters like floods and earthquakes.Effects of these disasters exacerbate relief reconstruction efforts.

2.1.1. Causes of landslides Some slopes are susceptible to landslides; others are more stable. Many factors contribute to the instability of slopes. The most significant variables are the nature of the underlying bedrock and soil, the configuration and geometry of the slope and ground-water conditions [225]. Three physical events occur during a landslide: the initial slope failure, the subsequent transport, and the final deposition of the slide materials. Landslides can be triggered by gradual processes such as weathering, or by external mechanisms including:  Undercutting of a slope by stream erosion, wave action, glaciers or human activity,  Intense or prolonged rainfall, rapid snowmelt, or sharp fluctuations in ground-water levels,  Shocks or vibrations caused by earthquakes or construction activity,  Loading on upper slopes, or  A combination of these and other factors. Geologists and geotechnical engineers use a variety of classification schemes to describe the causes of landslides. Because of this variety, many plans describing all types of landslides developed: External: Geometrical change: Gradient, Height, Slope length Unloading: Natural, Human-induced Loading: Natural, Human-induced Shocks and Vibrations: Single, Multiple/continuous Internal: Progressive failure: Expansion, Fissuring, Strain soften, Stress concentration [256]. Weathering: Physical property changes, Swelling, Chemical changes Seepage Erosion: Removal of cement, Removal of fines Water Regime Change: Saturation, Rise in the water table, Excess pressures, Drawdown

2.1.2. Factors affecting the landslide process (movements of a landslide) Three factors control the type and rate of mass wasting that may occur on the Earth's surface: 1) Slope gradient: The steeper the slope, the more likely that mass wasting will occur. 2) Slope consolidation: Sediments and fractured or poorly cemented rocks are weak and more prone to mass decay. 3) Water: If the water soaks the slope materials, the slope may lose cohesion and flows.

Ancuța Rotaru Habilitation Thesis

The motion of the heterogeneous mass containing water/snow, soil, and rocks is complicated and does not resemble the flow of a homogeneous and Newtonian fluid. Four distinct stages define the landslide activity [68], [79]: (i) Pre-failure stage when the soil mass is still continuous. Progressive failure and creep; (ii) Failure stage. Formation of a continual shear plane through the entire soil or rock mass; (iii) Post-failure stage which includes movement of the soil or rock mass involved in the landslide, from just after failure until it essentially stops; (iv) Reactivation stage when the soil or rock mass slides along one or several pre-existing shear surfaces. This reactivation can be occasional or continuous with seasonal variations of the rate of movement. From so many types of warning systems proposed, the selection of an appropriate one should take into account the stage of landslide activity: pre-failure, failure, or post-failure stage. At the pre-failure stage, a warning system applies to either revealing factors or aggravating factors. The revealing feature can be the opening of fissures or the movement of given points on the slope. The warning criterion is the magnitude or rate of moving. If the warning system associates with aggravating factors, then the quantum of affecting factors, the stability condition as well as the speed of movement needs to be well-defined. The warning criterion can be the pore water pressure, the stage of erosion, the minimum negative pore pressure or rainfall [194]. For the post-failure stage, the materials involved and the predisposition factors govern the hazard associated with a given rate of movement. At the failure stage, the warning system connects with revealing factors [283]. At the post-failure stage, a warning system has to be associated with the consequences of the movement/the rate of movement and runs out the distance. Warning systems do not modify the hazard but contribute by reducing the consequences of the landslide risk; expressly, the risk associated with the loss of life [8].

2.1.3. Landslide types Geological structure determines types and subtypes of landslides and the intensity of the landslide. Each slope has individual peculiarities, but the general features of the big groups determine the characteristics of the landslide process. The following attributes of slope geological structure are the most relevant: form, size and location conditions; physical and mechanical properties of rocks; contacts between rocks; contact orientation; fissures and other weak surfaces. Landslides can be classified using a lot of attributes as criteria such as:  Rate of movement: It ranges from very slow creep – millimetres/year – to extremely fast – meters/second.  Type of structure: Landslides are composed of bedrock, unconsolidated sediment and organic debris.  How they move: The moving debris can slide, slump, flow or fall.  Types of weakness planes and associated landslides: (1) slope failure in glacial sediment resulting in slumps; (2) parallel bedding in rock causing slides; (3) fracturing of rock promoting falls. Poorly planned forest clearing may increase rates of surface water run-off or ground-water infiltration. Inefficient irrigation may result in increased ground-water pressures, which in turn can reduce the stability of rock and sediment. Landslides may result directly or indirectly from the activities of people. The construction activity triggers slope failures. Many people, unaware of their exposure to landslide risks, modify the landscape building on unstable slopes or redirect the flow of the surface or ground-water.

2.1.4. Processes responsible for landslides Most slope failures occur during periods of exceptional rainfall or in springtime when the snow melts. However, exposure to rain or melting snow belongs to the natural existence of a slope. Nevertheless, if a slope is old, heavy rainstorms or rapidly melting snow can hardly be the only cause of the slope failure. It is most unlikely that they are without any precedent in the history of the slope so that they can only be considered contributing factors [282]. Furthermore, it is conceivable that the deforestation or an adjacent aquifer has produced an unprecedented increase in the highest elevation of the water table associated with unprecedented pore- water pressures at the base of the clay. One of the two changes may account for the catastrophe. The causes of landslides split into external and internal ones.

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards

External causes produce an increase of the shear stresses at unaltered shear strength of the material adjoining the slope [273]. They include a steepening or heightening of the slope by river erosion or artificial excavation. They additionally comprise the deposition of the matter along the upper edge of the slope as well as earthquake shocks. If an external cause leads to a landslide, the conclusion is that it increased the shear stresses along the potential surface of sliding to the point of failure [308]. Landslides in intensive seismic zones possess peculiar features. Several slopes may be stable under static loads (normal state). When the slope is in the limit equilibrium state, even a slight earthquake may destabilise it. An intensive earthquake may directly cause the whole slope to fail. Frequent earthquake activity directly influences the slope stability of the region: Internal causes lead to a slide without any change in surface conditions and assistance of an earthquake shock. Unaltered surface conditions involve unaltered shear stresses in the slope material [274], [292]. If a slope fails despite the absence of an external cause, a decrease of shear strength of the material assumes. The most frequent causes triggering such a reduction are either an increase of the pore-water pressure or progressive drop of the cohesion of the material adjoining the slope. External and internal causes of landslide-triggering are also rapid drawdowns, subsurface erosion, and spontaneous liquefaction [199]. Modelling indicates that an earthquake of magnitude 5 is enough to cause the front slope to slide while an earthquake of magnitude 7 makes the whole slope to fail. Some significant causes responsible for the landslide triggering – analysed below – are the external change of stability conditions, spontaneous liquefaction, and seepage from artificial and natural sources of water.

2.1.4.1. External change of stability conditions Two typical causes triggering landslides consist of undercutting the foot of the slope or deposition of the soil or other materials along the upper edge of the slope. Both operations increase the shear stresses in the ground beneath the slope [307]. If and as soon as the average shear stress on the potential surface of sliding becomes equal to the average shear stress, a landslide occurs [200]. A slope failure on an artificial embankment may occur during construction or at any time after its completion [9]. If the slope fails several weeks after the completion or later, the slide can be ascribed only to an internal cause reducing the shear strength of the slope material. Delayed slip planes occur commonly during severe rainstorms. Earthquake shocks represent external causes of landslides because they increase the shear stresses along the potential surface of sliding, whereas the shear strength stays unchanged [79]. The most steady materials are plastic clays exhibiting low sensitivity, dense sand above or below the water table and loose sand above the water table. The most sensitive materials are slightly cemented grain aggregates such as loess and submerged or partly submerged loose sand. Every rainstorm causes a decrease of the shear strength along potential surfaces of sliding. Therefore, the factor of safety of every slope with relation to sliding conforms to cyclic changes. The frequency of minor variations occurs no more than a few weeks or months, while the critical ones provide a frequency of many years. The total cohesion of the rock along the potential surface of sliding is equal to the combined shear strength of all blocks of rocks interfering with the sliding movement. The analysis of landslides assumes that the soil voids are waterlogged below and above the piezometric surface. The error ascribed to this assumption is minor unless the slope material consists of very coarse- grained sediments like coarse sand or gravel without a mixture of finer fractions. The assumption disregards the effect of capillary forces on the stability of the slope. These forces increase the slope stability under any circumstances.

2.1.4.1.1. Seepage from artificial and natural sources of water Seepage from artificial sources of water may compromise the stability of existing slopes, depending on the character of the slope-forming material and on the conditions of stratification. It may reduce the shearing resistance of the ground. It may eliminate apparent cohesion produced by the surface tension in drained soils and the significant cohesion by eliminating cementing materials in solution. It may cause a slope failure by regressive underground erosion by water veins emerging at the foot of the slope. The meaning of the term artificial source of water is that the reservoir is of recent origin. Otherwise, the slope failure caused by the seepage derived from the fountainhead occurred long in the past.

Ancuța Rotaru Habilitation Thesis

The wet fine silty sand can form permanent vertical slopes of several meters high. The cohesion needed for maintaining the equilibrium of such slopes is responsible for the friction produced by the surface tension of the contact moisture (water particles, surrounding the points of contact of the grains). Therefore, the stability of such slopes involves the existence of a large contact area between the air and soil moisture within the slope-forming material. The water, which seeps towards steep slopes during rainstorms, does not throw out enough air to destroy the apparent cohesion of sand or silt. If water percolates through the ground towards the slope in large quantities and without stopping the air thrown out, apparent cohesion eliminates, and the slope fails. A similar failure occurs if a steep slope of fine sand or silty sand submerges for the first time in its history. Slope failures due to the removal of a binder by the solution stand for a typical phenomenon in loess regions. Loess owes its cohesion to a soluble binder that consists of calcium carbonate. Since typical loess encloses many vertical root holes, it groups vertical cliffs which stand stable for years or decades provided the water table permanently lies below the cliff bases. Additionally, many artificial caves in loess existed for centuries without their unsupported roofs to exhibit signs of deterioration. These facts lead to the conclusion that the water, which percolates through the voids of loess during rainstorms, does not noticeably weaken the bonds between loess particles. If the loess is submerged or a permanent seepage through it settled, the bonds between its particles perish within a few weeks or months. The loess assumes the character of supersaturated rock flour, which flows. After the flow came to rest, the excess water gradually drains out, and the ultimate product of the drainage process possesses the properties of fine loose sand. The intensity of the effects of saturation on the physical properties of loess increases with increasing initial porosity. The evaporation has active influence for the seepage and the mechanical behaviour of unsaturated soil. The evaporation causes the suction value to increase in the surface party of soil-structure. The volume contraction of unsaturated soil by suction increase induces the tension crack in the soil surface. The conventional approach in designing a slope against slide failure is to adopt a set of design criteria and compute a factor of safety (FoS). Selection of a target value for the factor of safety involves the understanding of subsoil nature as well as its variability, geometry, and failure consequences [249]. The modified criterion FoS changes the permeability coefficient of the surface soil layer. Ultimately, the variation of slope stability with the depth of the tension crack zone is analyzed, and FoS increase is modified. If there is a tension crack zone in the surface layer of the slope, the slope stability decreases with the rain infiltration, increasing at the surface. Knowing the stability state of a slope due to rainfall is of paramount importance and all factors need to be studied. Slope failure accepts a direct connection with water seepage in the vast majority of natural and human cut slopes and the evaporation affects the slope seepage as well. If there are tension cracks in the surface layer caused by volume contraction due to water decrease during the rain, the seepage increases the slope potential to collapse. The saturated and unsaturated seepage calculation in seepage analysis problems takes into consideration rain condition only. Therefore, the study of the influence of the evaporation on the seepage and the mechanical behaviour of an unsaturated soil is still not enough. For unsaturated soils, to studying the interaction rain/evaporation during seepage as well as the surface inducing cracks by a suction curve - volumetric strain relation is significant. The influence of evaporation on slope stability connects the general slip stability method to seepage calculation. The suction variation can induce volume shrinkage to unsaturated soils. The volume contraction and suction can bring on tension failure and produce tension crack zones to the surface layer of the slope. When many tension cracks appear in the surface layer, they may cause changes in permeability. Consequently, the seepage results vary whether the evaporation counts or not. If the evaporation is significant in dry periods, the suction values at the slope surface will increase so that the slope stability also increases. If the suction is high before rainfall, it will intensify the water seepage during the rain, raising the degree of saturation. The slope stability decreases rapidly. Following the results, some conclusions come out: (1) The evaporation influences the behaviour of unsaturated soils. The evaporation can cause the suction increase and volume contraction in the surface layer of soil-structure. (2) Because the shrinkage/volume contraction of unsaturated soil can induce the fracture or tension crack at the surface, the permeability of the surface layer changes. (3) When seepage analysis considers the evaporation, the tension crack zone in the slope surface layer will increase the water volume of seepage. The value of the factor of safety when considering

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards rain/evaporation activity is down than considering the rain condition only. So, considering the influence of rain/evaporation process for the stability analysis of the slope is relevant. The natural surface water, as well as the pore water in the subsoil, are not ideal incompressible fluids. Microscopic air (gas) bubbles disperse in the water, so the fluid shows certain compressibility. At boundaries, the compressible pore water causes a delayed reaction at any pressure change if the permeability of the subsoil is less than the velocity of the surface water. Because of this phenomenon, the interaction of surface water with pore water affects bank stability. Pressure release on slope stability depends on soil permeability, compressibility of the pore water, and velocity of the pressure changes. Unstable slopes repeatedly introduce time-dependent movements, which may be extremely variable. In general, the change of water levels resulting from rainfall behind and inside the slope explain these variations, and the engineering practice universally accepts this dependency. However, torrential rain will more likely run off at the surface rather than penetrating the low-permeability soils. In this way, the influence of the rain on the piezometric line is minor and delayed in time. As variations in the pore water pressure control the effective shear stress, they include time-dependent effects of external pressure variation and influence the soil located below the piezometric line. The accepted external pressure variation has emerged in changes in water level. Variations of barometric pressure acting on a slope may also influence pore water pressure conditions. Under certain conditions, this effect may trigger landslides.

2.1.4.2. Internal causes of landslides 2.1.4.2.1. The presence of ground water in landslide Most of the slope failures happen because of excessive rains. The topography of the underground water does not follow the topography of the ground surface. The groundwater topography in moving complex masses forms a series of vein-streams. Detecting the veins of the groundwater on landslide mass represents the first necessary stage for planning drainage network and any other prevention work. One-meter depth temperature measuring remains a reliable method for conducting groundwater detection on landslide masses. Measurements of spring-water and wells temperature in the landslide area shows a negligible variation of groundwater temperature in winter and summer. However, the annual variation of temperature at one-meter depth is appreciable in landslide masses. That could be due to the non-uniform distribution of groundwater. Based on this fact, it is possible to detect the vein- streams of groundwater in displaced soil masses by measuring one-meter depth temperature. This method measures the temperature of the ground at one-meter depth on a network of landslide map. The temperature around the vein-streams is lower during summer and autumn and higher during winter and spring, but it is nearly stable during winter and summer. For example, Fig.5 shows the measured temperature at one-meter depth in Japan for one year. It is about 16.5Cº for all seasons (θw). The surface temperature is affected by groundwater vein-streams. Fig.5 shows the measured temperature at one- meter depth for the same point (θu). It changes from 7.5 Cº in January to a maximum of 24.9 Cº in August. This phenomenon serves as the basis for detecting vein-streams in landslide masses. ,is greater than 2.5Cº. Therefore, late spring ׀ θu - θw׀ This method could be useful when the value of early summer, late autumn and early winter are unappropriate for investigation, as Fig.5 shows. The procedure for this method is as follows: 1. First, the investigation area should be set up by meshes with the dimensions of 15 m x 30 m. 2. Nonconductive rods fixing thermal sensors are added at the bottom of holes. Thermal sensors connect to the thermometer with the precision of ±0.1Cº. 3. One-meter depth temperature is measured after being constant (experimentally, the waiting time should be about 10 minutes). The measured temperature is affected by some factors. Research studies control temperature correction measured by sensors, the effect of annual temperature variation, geological conditions, and the water in holes. All sensors must be calibrated before the field survey adopting a high-precision thermometer. Correction of the annual temperature variation is useful when the fieldwork is old-established; a sensor set on a hole at the middle part mass measuring the temperature three times a day. Experimentally, more than 350m difference in elevation could affect the results. The landslide map shows calibrated values.

2.1.4.2.2. Weak zones of a saturated clay landslide Once a landslide triggered, the material is transported by various mechanisms including sliding, flowing

Ancuța Rotaru Habilitation Thesis

and falling. Landslides often occur along planes of weakness that may parallel the hill slope. In bedrock, planes of weakness are typically beds, joints or fractures. Soils such as silt and clay are weaker than rock and frequently develop complex (or multiple) planes of weakness. In the case of saturated clays, the shearing displacements lead to relative motions of the structural aggregates still uncrushed along surfaces of discontinuity together with their opening. These relative movements bring about mechanical swelling [309]. Consequently the increase of water, the soil shear strength is drastically diminished to the residual value, provoking local failure. This happens in clays located very near from the base of a loessian stratum in which there is free water source (e.g. Tulucești, Dobrogea, Romania). In this way, due to dilatancy, a weak area appears right under the loess. This lead to the detachment of a new plot of Fig.5. Annual time series of temperature soil from the plateau, triggering in detrusive way the changes of one-meter depth under ground, in progressive landslide. Japan (after Malamud et al., 2004) Landslides phenomena occur when permeable strata lying on structured clay deposits facilitate the free water access towards mechanically swollen zones due to dilatancy [244]. It is important to define the weak areas in which dilatancy appears, according to the stress values, because they are parts of the sliding surface. The hyperbolic model uses to simulate the soil behaviour in the plane state strain [94]. For determining the parameters of the material, the tangent modulus Eτ, bulk modulus B and dilatancy modulus H are calculated with relations: 2 n E = {1 – [RF1(1 - sinφ) (σ1 - σ3) / 2c cosφ + 2σ3 sinφ]} K pa (σ1 / pa) E n B = K pa (σ3 / pa) B 2 n H = {1 – [3τnet RF2(1 - sinφ) / 2√2]} K pa (σ1 / pa) H where nE,, K, nB, nH, RF1, RF2 are hyperbolic models parameters and pa is the atmospheric pressure. An extra volumetric strain will appear in those areas of the slope. Assuming that dilatancy appears as isotropic phenomena [259] the correction of stresses is considered a state of initial stresses and a new vector of nodal loadings corresponding to it [289]. In this way we can establish the deformations occurring with the corrected stresses, for all the finite elements, and we can identify the dilatancy areas along the slope [248], [266]. Consequently, the landslides phenomena in fissured clays can be prevented by draining the critical areas or by modifying the soil mechanical properties using chemical or thermical methods.

2.1.4.2.3. Spontaneous liquefaction The arrangement of the grains of fine sand or coarse silt can be so unstable that a slight disturbance of the equilibrium of the grains may cause a rearrangement, whereby the grains settle into more stable positions, and the porosity of the sediment decreases. If this process takes place above the water table, it has no other effect than a settlement of the ground surface. By contrast, consequences can be catastrophic if it occurs below the water table because of the viscosity of the water occupying the sand voids, which prevents a rapid porosity decrease. Between the collapse of the structure and the reconsolidation under the new conditions of equilibrium, the sediment has the properties of a thick viscous liquid that spreads laterally until its surface becomes almost horizontal. The transformation into the liquid state is known as spontaneous liquefaction [297]. Velocity is the most relevant parameter determining the destructive potential of landslides. Catastrophic rates of several meters per second are attained by certain types of landslides only. High velocities are the consequence of strength and failure mechanisms. Strength loss can occur instantly during the failure process through the loss of cohesion, liquefaction of granular material or remoulding of sensitive clay. The most coherent explanation of the process of spontaneous or earthquake liquefaction failure uses the

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards

“collapse surface” concept, proposed by Sladen [327]. Collapsible materials exist in situ at void ratios higher than the steady-state void ratio. Under full saturation, granular collapsible soils are formed by rapid deposition, which prevents proper packing of the soil skeleton. Typical examples are sand or silt deposits on river deltas or artificial hydraulic fills. In saturated clays, a collapsible structure may be due to electrochemical changes induced by pore-water leaching [79]. The origin and behaviour of a collapsible structure for partly saturated soils are barely understood. On saturation, suction moves away, and the ground collapses [79]. However, this would not be an immediate process as saturation of a mass of fine-grained soil takes a long time measured in hours or days. As yet, one can frequently observe sudden liquefaction in some deposits, particularly at basal contacts where perched water tables expect to occur [98]. One possibility of loess to maintain its unstable skeleton until sufficient quantity represents saturation to the point of collapse is to preserve a part of the cohesion chemical. Therefore, the loess can support the soil structure until sudden rupture, even during saturation. This rupture brought about by overstressing occurs due to stress redistribution by progressive failure or earthquake shaking. Cementing by calcium carbonate, iron or aluminium oxides represent a possibility. A similar process may be active in producing a collapsible structure with well-graded materials like natural colluvium or artificial fills. Such material is loosely deposited in a moist condition and held in this state by light cementing. With time, some fine-grained portions of the initial dry deposits become saturated, without a change in void ratio. The collapse occurs when the shearing rupture suddenly disrupts the loose structure of the soil. Thirty years ago, only uniform loose saturated sands were considered able to collapsible liquefaction [327]. Many well-graded materials possess a collapsible structure. The most common stratigraphy involves a colluvial veneer covering residual soil, bedrock or glacial till. Even more unstable remain volcanic ejections covering steep eroded topography [71]. Their presence on slopes that often approach or surpass 45° indicates cohesion. Cohesion gets lost upon initial failure displacement and rapid acceleration results. If the cover of the steep upper slope is essentially unsaturated, a gradual accumulation of seepage may saturate the over-ridden low parts subjected to liquefaction by rapid undrained loading [154]. Debris avalanches starting as localized failures of soil grow as they propagate downslope, increasing in volume many times beyond the magnitude of the initial slide. The effect of spontaneous or earthquake liquefaction purely represents a sudden change of the material from solid to liquid state. Fluid dynamics models use to simulate this change [141]. Liquefaction may affect the depth of the material (usually if fully saturated) [211]. Alternatively, only a thin basal layer may liquefy, due to an accumulation of pore water above an impervious contact. The analysis considers the internal friction and stiffness of the sliding mass [80]. These are a few of landslide causes. Many of them wait to be known, especially the dynamics of a landslide surface and its history because soils are vulnerable to all kinds of landslides [235].

2.1.5. Landslide risk evaluation The degree of stability of a slope cannot be reliably estimated unless the processes which may lead to failure are clearly understood and quantitative information regarding the controlling factors is available. Considering the hazard and probability of landslide development as coincident does not seem correct since “hazard” corresponds to the real danger on a site for the advancing phenomenon. Alternatively, the probability does not show the real danger state, because not all the landslide phenomena are dangerous for the elements at risk. The coincidence hazard-probability is inappropriate because “a hazard” is connected to the real danger, which is related not only to the circumstance probability but also to its intensity. Therefore, it is more correct to define hazard on the basis of both probabilities of happening and intensity of the landslide phenomenon. With this definition, the term "specific risk" disappears and corresponds to the modern definition of vulnerability. The recent definition of the elements of risk comprise the following:  Intensity (I): severity of the landslide phenomenon. It can be assessed in relation with dimensions, velocity and energy of the phenomenon. The assessment of the relative intensity of landslide events accepts the geomorphological evolution of a landscape and for landslide hazard assessment studies.  Probability (P): the probability of appearance of the landslide phenomenon. In its assessment, in the case of active landslides, the return time must also be taken into account.

Ancuța Rotaru Habilitation Thesis

 Hazard (H): the degree of the predicted danger for the elements at risk following the occurrence of a landslide phenomenon. It is a function of intensity and probability.  Elements at Risk (E): they represent the population, property and facilities exposed to landslide risk.  Vulnerability [V = F (H, C)]: a degree of loss (damage) produced or predicted to elements at risk assessed according to their characteristics (C) for a landslide phenomenon of a given level of hazard.  Risk [R = f (V, W)]: the value of predicted damage to elements at risk from a landslide event of a certain level of hazard. It speaks out of annual cost and the number of units (people) lost per year. Intensity and probability represent hazard criteria; hazard and the elements at risk represent risk criteria. The probability of occurrence of a landslide (P) appears from the stability map, which divides the areas into 1) stable areas (P = 0), 2) unstable areas (P = 1), 3) medium-stable areas (0 < P < 1). It follows that the stability map becomes a probability map. In the event of unstable areas, primarily active landslides, the data regarding the return time of landslides complete the probability map. Showing the damage produced or predicted to the elements at risk on the hazard map following landslide phenomena drives to the vulnerability map. This is achieved by keeping human vulnerability distinct from that of property and facilities, therefore gaining two distinct vulnerability maps. The quantification of the predicted damage (the value of goods and services subjected to damage and predicted number of human losses) makes it possible to transform the vulnerability map into a risk map. Since damage and human losses are difficult to assess, the risk map outlines with "relative" criteria as areas arrange in relation with elements at risk subjected to damage. This practice makes it possible to establish, on a geological-technical basis, the programmes of management and mitigation of risk. Elements at risk can be assessed both on the basis of their economic and social value, and on the basis of elements of judgment varying from case to case.

2.1.6. Dynamics of the landslide activity The required conditions for a landslide to occur are: 1) a slope structure with a brittle upper layer and a plastic lower layer; 2) sufficient thickness of the topmost layer to transfer loads to the lower one generating irreversible deformations; 3) plastic deformations and lateral spreading of the lower layer mass. These conditions serve as criteria for the forecasting of the locations of block landslides [7]. The determined reduced speeds of contemporary movements of the block landslides provide the possibility to use the affected territories for construction and other economic activity [87]. The dynamic of the landslide is composed of one or more possible movements representing one or more stages of landslide activity. These movements are analyzed below.

2.1.6.1. Movements preceding a slide Some slides occur without warning. No sliding can take place unless the ratio between the average shearing stress of the ground and the average shearing stresses on the potential surface of sliding has decreased from a value greater than one to unity at the instant of the slide [375]. The only landslides preceded by an almost instantaneous decrease of this ratio are due to earthquakes and spontaneous liquefaction. The others occur by a gradual decline of the correspondence involving a progressive deformation of the slice located above the potential surface of sliding and a downward movement of points located on the surface of the slice. Preliminary processes make the slope susceptible to movement without actually initiating it and thereby tending to place it in a marginally stable state. Triggering processes initiate movement. If a landslide comes as a surprise, we could say that the observers failed to detect the phenomena that preceded the slide. A proper understanding of how landslides trigger is crucial. A summary of the landslide triggering conditions, natural and human, is presented in Table 3. These factors shift the slope from a marginal stable to an actively unstable state. Support removal: Excavation or erosion at the base of a slope can cause an unstable situation. The removed material was supporting the soil from the slippery area. This loss of support triggers landslides. Removal of vegetation: To reduce landslide incidence (i) the vegetation removes water from the soil; and, (ii) the root systems support the ground and provide a stabilizing effect. Areas that experience forest fire or clear-cut timbering are subjected to landslides for many years after the accident. Addition of moisture: Soils, especially clays, are stiff when dry but they transform into a soft mud with mixed water. The addition of water reduces the shear strength of the soil and can develop landslides; it is the most frequent source of landslide troubles.

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Table 3. Landslide triggering conditions Landslide triggers Natural triggers Human triggers Removal of support Erosion at the base of a slope by streams, Excavation at the base of a slope or on Removal of vegetation waves, glaciers, forest fires a hillside Timbering Addition of moisture Rainfall or snowmelt Sewage or runoff disposal, broken water pipes, improper grading Addition of weight Heavy snowfall, volcanic ash, landslides Placement of fill Oversteeping Removal of support Placing fill at a gradient that exceeds the angle of repose Vibrations Earthquakes, nearby landslides Blasting, operation of heavy equipment

Addition of weight: Adding weight to the top of a slope can generate landslides if the added load exceeds the shear strength or increases the pore pressure of the soils below. Oversteepening: The angle of repose represents the maximum angle whereat a material can be stacked and remain stable. If the soil overcrowded at an angle that exceeds the angle of repose, landslides result. Vibrations: Sudden movements can cause the soil particles to lose contact one with another. Thus, the frictional forces that enable the fabric to remain on a slope are lost so that landslides occur. Vibrations from earthquakes and heavy equipment trigger landslides. Frequently, the massive amount of groundwater and excess hydrostatic pressures caused considerable pot-holing to occur before the slope commences to move [166]. Such hydrostatic pressures are transmitted down-slope through natural pipe networks and have some influence on the gradual creep movement that occurs on the majority of such slopes. Very gradual ground shifts are known to introduce extensive landslides. Repeatedly, these are on a scale of millimetres, too slight for local observers to even notice them, but enough to be detected via satellite using radar interferometry [117]. The total displacement just before failure is dependent on the strain that corresponds to the peak strength and on the thickness of the failure area. The movement is slighter in case of normally consolidated clay than for stiff overconsolidated clay [119].

2.1.6.2. Movements during the slide Shear failures through any material along a surface of sliding are associated with a decrease of the shearing resistance. Therefore, during the first phase of the slide, the sliding masses advance at an accelerated rate. However, as the slide proceeds, the force that maintains the sliding movement decreases because the soil mass comes into more stable positions. Therefore, the accelerated motion changes into a delayed one and finally stops or assumes the character of a creep. The maximum velocity of motion depends on the average angle of the sliding surface, the effect of slip on the resistance against sliding, nature and orientation of stratification. The slope angle represents the angle between the horizontal and the ground surface. Landslides on slopes with low angles highlight the role of clay layers within the shale formations in slope stability. The steepest surfaces of sliding develop in quasi-homogeneous materials such as irregularly jointed rocks, cemented sands and loess, which combine cohesion with high internal friction. Therefore, slides in such materials are likely to be sudden. Landslides are more likely to occur on slopes with lines to the north (north-facing slopes). The hypothesis is that less direct sunlight and slightly cooler temperatures lead to less evaporation and more moisture in the soils on north-facing slopes. Velocity remains the most relevant parameter determining the destructive potential of landslides. “Catastrophic” rates of several meters per second are reached only by certain types of landslides. High velocities are the consequence of a range of strength loss mechanisms. Strength loss can occur instantly during the process of failure, through the loss of cohesion, liquefaction of granular material or remoulding of sensitive clay. Significant loss of strength can occur during movement, including rock joint roughness reduction, shearing, liquefaction, frictional heating, loss of internal cohesion, material/water entrainment, and rapid undrained loading. Extremely fast landslides include rock, debris and earth fall, rock and flow slide in granular soil, debris and rock avalanche, debris flow. There is a need to study the post-failure behaviour of materials, to facilitate predictions of the behaviour of

Ancuța Rotaru Habilitation Thesis extremely rapid landslides for hazard assessment. Based on their velocity, landslides divide into seven classes. Table 4 summarizes the velocity scale and the associated destructive significance. Failure phenomena observed in rainfall-induced landslides showed that the failure mode depends on the grain size. The flow behaviour of soils with 20-30% loess is different from sands or a mixture with 10% loess, showing considerable velocity without deceleration. It implies the existence of a mechanism that maintains high pore pressures during the motion.

Table 4. Classification of landslides after velocity Landslide velocity Destructive significance < 1.6mm/yr Imperceptible without instruments. Construction possible with precautions. 16mm/yr to 1.6m/yr Permanent structures undamaged by movement. 1.6m/yr to 13m/mon Remedial constructions can be undertaken during movement. Insensitive structures can be maintained. 13m/mon to 1.8m/hr Some insensitive structures can be temporarily maintained. 1.8m/hr to 3m/min Escape evacuation possible. Structures and equipments destroyed. 3m/min to 5m/sec Some lives lost because not all persons are able to escape. > 5 m/sec Catastrophe of major violence. Buildings destroyed by impact of displaced material. Many deaths.

In saturated soils, during motion, the pore pressure of the soaked mixture increased with velocity because of the floating of sand grains accompanying the movement for each test [166]. The sample with a fine-grained size or significant fine-particle contents (loess) floats lightly, and high pore pressure is maintainable during the motion. The floating ratios of grains attained a significant value (>0.85) at an extremely slow velocity for samples with 20-30% loess. The grain size and fine-particle contents can deliver a significant impact on the mobility of rainfall-induced landslides [194]. Shear strength decreases because of slip ranges from 20% for loose sands and clays with reduced sensitivity to 90% for loose saturated sands, silts, or extra-sensitive clays. Slides in very sensitive clays and loose, saturated sand occur very rapidly. Slides triggered by a shear stress increase on the potential surface of sliding in low-sensitive residual soils seldom reach velocities of 0.30 cm/h [155]. The weight of standing water imposes hydrostatic pressure on a structure. The deeper the water, the more it weighs and the greater the hydrostatic pressure. If the hydrostatic pressure in excces at the horizontal boundary between sand/silt/clay triggers a slide, its maximum velocity is high. The type of movement depends on many factors including the slope gradient, type of material, and hydrological conditions [166]. There are six distinct types of landslide movement as follows:

2.1.6.2.1. Falls Falls occur in almost all types of rocks, especially along bedding planes, joints or local fault areas or fault planes (Fig.6). However, falls are one of the main erosion mechanisms occurring when the erodible sand or silt underlies an erosion-resistant overconsolidated clay [166]. Falls are abrupt movements of masses of geologic materials, like rocks and boulders. A fall starts with the detachment of soil or rock from a steep slope along a surface with little or no shear displacement. The material descends primarily through the air by falling, bouncing, or rolling. Separation occurs along discontinuities like fractures and joints. Bedding Fig.6. Fall planes occurs by free-fall, bouncing, and toppling. The material may roll for considerable distances downslope forming talus slopes. Movement is very rapid to extremely rapid, with no prior indication. Except when the displaced mass is undercut, falling is preceded by small sliding or toppling movements that separate the displacing material from the undisturbed soil mass. Gravity, mechanical weathering, and the presence of interstitial water significantly influence falls. They are familiar, both in rock and debris, on steep slopes below bedrock

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards scarps in upland areas. Falls trigger because of support loss due to basal erosion, undercutting, loss of internal strength by weathering, mechanical break-up by freezing/thawing or high water pressures. There are no reliable methods for calculating the stability of a slope concerning falls. These processes are most common in crystalline rocks on the steep slopes of glacial cirques and valleys. In the alpine belt of the Carpathian Mountains, rockfalls are the most typical mass movements.

2.1.6.2.2. Topples A topple represents the forward rotation of a mass of soil or rock out of the slope around a point or axis below the centre of gravity of the displaced mass (Fig.7, Fig.8). The rock mass may stay in place in this position for a long time, or it may fall away down-slope due to weakening or undercutting. It depends on the type of rock, the geometry of the rock mass, and the extent of the discontinuities. Topples range from extremely slow to extremely rapid, sometimes accelerating throughout the movement.

2.1.6.2.3. Slides A slide represents a down-slope movement of a soil or rock mass that occurs dominantly on the surface of rupture or on relatively thin zones of intense shear strain [314]. Slides involve the displacement of masses of material along well-defined surfaces of rupture called slip or shear surfaces. The material moves in mass but is likely to break up with distance from the initial rupture point. Frequently, the first signs of ground movement are cracks in the original ground surface along which the main scarp of the slide will form. The displaced mass may slide beyond the toe of the surface of rupture covering the original ground surface of the slope, which becomes a surface of separation. Whenever a mass of slope material moves as a coherent block, a slide has taken place. There are several types of slides, but one of the most common is a slump. A slump occurs when a portion of hillside moves downslope under the influence of gravity. It has a characteristic shape, with a scarp or cliff at the top, and a bulge of material (ordinarily called the toe) at the base. Slides divide into rotational and translational. Rotational and translational landslides are movements above one or more failure surfaces. The motion occurs as a result of either sliding on discrete shear surfaces or ductile deformation within a shear zone. One of the two movement styles is evident during accelerating phases for all landslides. The first style assumes a linear form in a plot of 1/v against time (v represents velocity). The second style maintains an asymptotic shape in the same scheme trending toward steady-state movement rates. The linear form occurs in landslides whereby crack propagation (shear surface generation) remains the dominant process. The second style triggers where movement occurs across existing planes of weakness or as a result of ductile deformation processes [207], [375].

Fig.7. Topple Fig.8. Movement along a circular failure surface of a topple: transition

2.1.6.2.3.a. Rotational slides Rotational slides involve sliding on a concave shear surface upwards in the direction of movement where the displaced mass rotates around an axis parallel to the slope (Fig.9, Fig.10). Cracks or scarps mark the concentric back of the slide slope. The displaced mass may flow further down-slope beyond the rupture surface to form an accumulation zone at the toe. Rotational slides can be single or multiple events [207].

Ancuța Rotaru Habilitation Thesis

2.1.6.2.3.b. Transitional slides Transitional slides are also called planar slides. The mass of material moves down-slope on a broad planar surface (Fig.11). Translational slides can produce disparate impacts on rotational slides. If the slope is sufficiently steep and the shearing resistance along the slip surface remains low, the movement goes on for a great distance, different to rotational slides. Translational slides in rock usually occur along discontinuities like bedding planes or joints. In the event of a debris slide failure on shallow shear surfaces at or near the surface, changes in strength and permeability occur. Slopes are prone to translational sliding if the discontinuities lie parallel to the ground surface [207].

Fig.9. Rotational slide Fig.10. Rotation along a circular failure surface Fig.11. Transitional slide

2.1.6.2.4. Spread Spread defines as an extension of cohesive soil or rock mass combined with general subsidence into the soft underlying material. The spread may result from liquefaction or flow of the soft material. Spreads are distinctive because they typically occur on very gentle slopes or flat terrain. The dominant movement in spreads involves the lateral extension of the underlying weak material (soil or bedrock) due to shearing or tensional fractures. It is due to liquefaction or plastic flow. Routinely, rapid ground motion, like that experienced during an earthquake, triggers the failure, but can also be artificially induced. The resulting lateral movement breaks up the overlying material into more or less independent units or lumps that may subside, translate, rotate, or disintegrate. This extension of coherent rock or soil may be due to plastic flow of a weaker subjacent layer. The coherent mass may subside into layers, it may slide or flow. Spreading in fine-grained materials on shallow slopes is usually progressive. The failure starts suddenly in a minor area and spreads rapidly.

2.1.6.2.5. Flows A flow represents a spatially continuous movement in which surfaces of shear are short-lived, closely spaced, and usually not preserved. The distribution of velocities in the displacing mass resembles that in a viscous liquid. The lower boundary of the displaced accumulation represents a surface along which appreciable differential movement or a broad zone of distributed shear have taken place. Thus, there is a gradation from slides to flows depending on water content, mobility, and movement evolution [140]. Flows can occur in bedrock, but they are extremely slow and occur in areas of high relief. Flows in unconsolidated materials are evident. During a flow, the material breaks up as it moves down a slope and flows as a viscous fluid. The rate of movement can range from very slow to extremely quick, and in terms of moisture content, can extent from totally saturated to dry. The effect of water is relevant in initiating flow. There are numerous types of flows: rock flow, earth flows, debris flow, mudflow, spontaneous liquefaction and solifluction.

2.1.6.2.5.a. Rockflow Rock flow involves gradual deformation of the rock mass along joints and fractures following no distinct failure plane. The movements are extraordinarily slow and constant with time. This type of motion refers to as creep. Flow movements may result in folding, bending, bulging, or other manifestations of plastic behaviour [367]. In Romania, the rockfall area on steep slopes comprise folded

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards and faulted Paleocene sandstones in the Eastern Carpathians [264]. Rockfalls in the Buzau Mountains resulted from the earthquake that occurred on March 4, 1977 (Mw = 7.2). The volume of rock displaced by the shock was 20-50 times larger than the average annual volume emanating from the cliffs. 2.1.6.2.5.b. Earthflow Earthflow represents a transition between a slide and a mudflow [138]. Earth flows are viscous fluid flows (Fig.12). The flowing mass can be wet or dry. Slip surfaces within the active accumulation are not visible. The boundary between the effective concentration and the material in place may represent a distinct surface, or it may comprise a relatively broad area. The slope material liquefies and runs out, developing depression at the head. The flow is elongate and usually occurs in fine-grained materials or clay-bearing rocks on moderate slopes and under saturated conditions. Many earth flows continue to move for many years until the inclination of the shear strength is insufficient. 2.1.6.2.5.c. Debris flow Debris flow represents a rapid mass movement in which loose soil, rock, organic matter, air, and water mobilize as a slurry flowing downslope (Fig.13). Debris flows contain a significant percentage of coarse fragments (<50% fines) and result from intense precipitation or rapid snowmelt, which erode and mobilize loose soil or rock on steep slopes. The moving soil and rock debris quickly gain the capacity to move significant amounts of material at faster and faster Fig.12. Earthflow speeds. They follow existing stream channels and can extend for several kilometres before stopping and dropping their debris load in river valleys or at the base of steep slopes. Debris flows commonly mobilize from other types of landslides (Table 5) that occur on steep slopes, are nearly saturated, and consist of a large proportion of silt and sand-sized material [83]. Debris flows develop in arid and semiarid regions where the ground is uncovered by vegetation or in slopes filled with debris. Fires that denude slopes of vegetation intensify the susceptibility of slopes to debris flows [353]. 2.1.6.2.5.d. Mudflow Mudflow or mudslide comprise the most rapid (up to 80 km/h/50 Fig.13. Debris flow mph) and fluid type of downhill mass wasting (Fig.14). A mudflow is an earthflow consisting of material that is wet enough to flow rapidly. Mudflow occurs on steep slopes over 10°. It is a sudden movement which occurs after periods of excessive rain. When there is not enough vegetation to hold the soil in place, saturated soil flows over impermeable subsoil, causing great devastation and endangering lives. Mudflows are composed of fine-grained soils (>50% sand-, silt-, clay-sized particles [166]. They are highly saturated and can propagate very quickly.

Fig.14. Mudflow Fig.15. Creep

Ancuța Rotaru Habilitation Thesis

2.1.6.2.6. Complex landslides Complex landslides involve more than one type of movement mechanism. There are different types of movement in the effective mass at the same time or a change of motion if the landslide develops and proceeds with down-slope. Though there are different types in nature, two or more types of movement are frequently involved. A typical event is if slides trigger flows in the lower parts of the slope. Large landslide zones traditionally have complex landslide types. The experts recognize a complex landslide where mass movements achieve ground displacement. That should be not confused with landslide complex, an area of instability where various motions occur. In a complex landslide, materials can divide into rock, debris and earth. There is a continuum of mass movements from falls through slides to flows. It is challenging to decide whether masses of material fell or slide, and there are instances where material both slides and flows.

Table 5. Types of landslides (after Varnes, 1978, modified by Cruden and Varnes, 1996) Type of material Type of Type of soil movement Bedrock Coarse Fine Fall Rock fall Debris fall Earth fall Topple Rock topple Debris topple Earth topple Slide Rock slide Debris slide Earth slide Spread Rock spread Debris spread Earth spread Flow Rock flow (deep creep) Debris flow (soil creep) Earth flow (soil creep) Complex Combination of two or more principal types of movement

2.1.6.3. Movements after slide If the descent of the sliding mass eliminated driving and resisting force disparities, the motion turns into a gentle creep unless the slide altered sliding mass properties [354]. The change occurs because of the mechanical mixture of the material with water or destruction of the intergranular bonds at an unaltered water content. Soil creep represents an ultra-slow movement, occurring on very gentle slopes because of the way soil particles repeatedly expand and contract in wet and dry periods. When wet, soil particles increase in size and weight, and swell at right angles. When the soil dries out, it contracts vertically. As a result, the ground slowly moves downslope. Extra sensitive clays are commonly very thixotropic. If the clay is oversensitive, the slide turns it into a flowing mass whereas a similar slip in clays with reduced sensitivity merely produces local deformation. A rapid change in consistency because of disturbance of sensitive clay associates with changes in permeability. Hence, after the clay moved out of the slope, the strength of such clays increases at unaltered water content. If a slide causes disintegration and breakdown of a non-thixotropic mass of sediments during a heavy rainfall period, the material creeps for many years. Each rainstorm accelerates the creep rate [354].

2.1.6.4. Reactivation stage The creep phase of landslides is a preparatory stage of progressive failure and gives enough signals before turning into a catastrophic slope disaster. The creep phase is the reactivation of old landslides that took place in the long past due mainly to earthquake forces or tectonic activities through the faults. The formation of clay layers as a result of rock mineral weathering through the slip surfaces of the landslides justify the creep phase. The decomposition of rock minerals under the chemical action of underground water takes place through a previously developed plane of failure. After reaching the decomposition Fig.16. The life cycle of a landslide state, the shear strength of the slip layer

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards reduces considerably but not necessarily resulting in the complete creeping of the slope (Fig.15). The stress conditions along the slip surface lead to creep failure, in which the stresses do not change, but shear deformations occur under constant high confining stresses. An increase in rainfall could also lead to increased reactivation of ancient landslides. High groundwater levels promote each phase of reactivation [373]. If a slope has moved before, it has a higher chance to move on than one with similar characteristics, which has never moved. Those characteristics such as scarps, toes, and seeps hint old landslide activity. Building on the toe of a reactivated old slide can be devastating if buildings and roads raise upon them. Once moving, many early landslides are difficult to stop. Movement can occur after many years of inactivity, so sites are never safe. Dormant landslides are difficult to recognize. Vegetation covers the slides characterized by trees and cracks that have been filled by debris. Even small changes of the stability conditions (excavation at the toe of the slope) can activate dormant landslides (Fig.16). The age of a dormant landslide can be determined from the age of the oldest tree that is growing within the landslide area, from the stage of the erosion, and the development of recent soil profiles. The slides which have been stabilized by chemical or mechanical means can be either active or dormant.

2.1.7. “Fresh” and historical landslides Landslide events conventionally divide into two classes: (1) landslide-events associated with a trigger; and (2) historical (geomorphological) landslides, which are the sum of one or many landslide events in a region over time. Instantly after a landslide event, independent landslides are “fresh” and recognizable. The boundaries between the failure areas (depletion, transport and deposition areas) and the unaffected zones are usually distinct, making it easy to identify the landslide. That is peculiarly valid for minor, shallow landslides, such as soil slips or debris flows. For large, complex slope movements, the boundary between the stable area and the failed mass is transitional, particularly at the toe. The limit may also be transitional along the sides. For massive deep- seated landslides, identifying the limitation of the failed mass may not be easy even for recent failures, particularly in urban or forest areas. Investigators concentrate on areas where landslides were more abundant or where the damage was most severe. “Fresh” landslides can be complete plotted if the detailed mapping has been carried out shortly after the landslide event. Landslide boundaries become indistinct with the age of the landslide. That happens because of various factors, including local adjustments of the landslide to the new morphological setting, other landslides, and erosion. Historical landslide inventories are the total sum of a single to many landslide events that were occurring in a region over time (tens, hundreds or even thousands of years). In many landscapes, landslides occur where they triggered in the past. A characteristic of historical landslides is that evidence of many smaller landslides has lost due to modification by subsequent landslides, erosional processes, human activities and vegetation growth. Evidence of smaller landslides is likely to be lost, and the landslide boundaries become indistinct, making the landslides themselves much harder to identify. A formal definition requires that a landslide inventory includes all landslides associated with a landslide event (a single trigger) or multiple landslide events over time (historical). This definition assumes that all landslides are visible and recognizable and the entire study area affected by triggers, even marginally, is investigated. In practice, this criterion is never met. A functional definition requires including substantial fractions of landslides at all scales in the landslide inventory. A comprehensive catalogue must contain a dominant portion of minor landslides. This definition may apply to landslide event inventories, but not to historical ones because erosion and human actions erased many minor and intermediate-size landslides.

2.1.8. The distribution of landslides 2.1.8.1. The frequency–area (or volume) distribution of a landslide Landslides are generally associated with a trigger, like an earthquake, rapid snowmelt or a big storm. The landslide event can include an isolated landslide or many thousands. Slope failures typically occur

Ancuța Rotaru Habilitation Thesis within minutes after an earthquake triggered, hours to days after a snowmelt triggered, and days to weeks after an intense rainfall triggered [82]. A conventional model explains landslide behaviour. The model is the “sandpile” model. Noever (1993) and other authors have associated the power-law frequency–area statistics of broad landslides with the sand-pile model. In this model, there is a square grid of boxes. At each time step, a particle drops into a randomly selected box. When a box accumulates four particles, they go to the four adjacent boxes, or they get lost from the grid in the case of edge boxes. Redistributions can lead to further instabilities and avalanches of particles in which many particles get lost from the edges of the grid. Each of the multiple redistributions during a time step contributes to the size of the model “avalanche”. Having specified the size of the grid, the number of avalanches NL with area AL is determined. The area AL is defined to be the number of boxes that participate in an avalanche. There is an extrapolation from the “sand-pile” model to actual landslides, especially for the medium and massive landslides. Considering the simplicity of the model and the three-dimensional nature of current landslides, a revision of the rules for the “sandpile” model can show the practical landslide state. Nevertheless, the relatively standard “sand-pile” model may provide the basis for understanding the power-law statistics of massive landslides. In the “sand-pile” model, the region over which an avalanche will spread is well-defined before the avalanche. Similarly, the area over which a landslide will spread defines before landslide is triggered. In both, there are metastable areas. As particles added, the metastable avalanche areas grow. As mountains grow, metastable landslide areas grow. The coalescence of smaller metastable regions dominates this growth [107], [365]. Besides, the coalescence cross- sections lead directly to a power-law distribution of metastable areas. Similar coalescence and growth apply to metastable landslides. It explains the power-low frequency and distribution area of massive landslides. Pelletier (1997) gave other explanations for the power-law dependence. A slope stability analysis combines with a soil-moisture analysis to obtain a power-law distribution. Hergaten (1998) and Neugebauer (2000) proposed two alternative models for power-law distributions [129], [130]. In many historical and fresh-event landslides, the frequency–area distribution of medium and large landslides decays as an inverse power of the landslide area [118]. The frequency–area (or volume) distribution of a landslide event quantifies the number of landslides that occur at various sizes. The quantification of landslides can stimate erosional processes and assess landslide hazards. The quantification of the landslide-event is in terms of a general landslide distribution. Based on distribution, landslide-event magnitude scales quantify landslide events. An implication of general landslide probability distribution is the ability to generate a landslide event magnitude scale. Measures of event sizes are effectual for natural hazards. For example, the Richter scale universally uses for earthquakes. Other magnitude scales are available for other natural hazards including the Saffir-Simpson scale for hurricanes, Fujita scale for tornadoes and the Volcanic Explosivity Index. Malamud et al. (2004) proposed a magnitude scale mL for landslides [169] based on the logarithm to the base 10 of the number of landslides associated with the event: mL = log(NLT), where: NLT represents the number of landslides associated with a trigger. When examining landslides associated with individual landslide events, the area of all landslides that occurred as part of the event (ALT) is interesting to be known. Using the mean landslide area AL, and the number of landslides that occur during the event, a predicted area ALT of landslides in the inventory can be calculated. The total measured area of landslides associated with a landslide event ALT can decide the landslide magnitude mL. The distribution computes the largest landslide areas associated with a landslide event to estimate the landslide-event magnitude as well as the number and surface of landslides. The frequency-area statistics of landslides use either cumulative or non-cumulative statistics [168]. Fig.17 plotted the cumulative number of landslides NCL with areas greater than or equal to landslide area AL as a function of AL.NCL = C(AL)-α, where α is the power-low exponent and C a constant.

2.1.8.2. The general landslide distribution The focus is on the probability distribution of landslide areas for landslide events and several implications of the distribution. That includes the magnitude scale and incomplete inventories of landslide-events for historical landslides. The direct determination of the landslide-event magnitude depends upon a complete landslide inventory. However, the general landslide distribution can establish the extent of the landslide-event from a partial catalogue. The list is integral for landslide areas

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards exceeding a specified value only. The list is useful for historical inventories which include the sum of landslide events over time. The landslide distribution relates the area, volume and number of one or many landslides to the landslide magnitude, mL. That can estimate regional erosion due to landslides.

2.1.8.2.1. Landslide magnitude scale Keefer (1984) [25] and Rodriguez et al. [244] used a similar scale to Malamud et al. (2004) to quantify the number of landslides [169] in earthquake-triggered landslide events (Fig.18): 100-1,000 landslides classified as two, 1,000-10,000 landslides three, etc. Some important landslide event magnitudes Fig.17. Dependence of the mean landslide volume Malamud et al. (2004) considered [169] are on the total number of the landslide in the event Northridge earthquake-triggered event, mL = (after Malamud et al., 2004) [169] 4.05; Umbria snow-melt triggered event, mL = 3.63; Guatemala rainfall triggered event, mL = 3.98. While observed earthquakes span a broad range on the Richter scale, available landslide-event inventories limit to a relatively narrow magnitude range. In this manner, in investigated regions, only a few large landslide events with mL > 4.0 occurred. Given several hundred landslide events and their magnitudes in a region, there will be many smaller magnitude events compared to the massive ones. These follow the relationship log NC = - bmL + a where NC represents the number of landslides with magnitudes greater than mL, and b and a are constants.

Fig.18. Predicted landslide-event areas and 2.1.8.2.2. Historical and incomplete volumes associated with a given landslide inventories event magnitude (after Malamud et al., 2004) Assuming the landslide probability distribution [169] applies to all landslide events, the sum of events over time (the historical inventory) equally satisfies it [169]. However, concerning historical lists, the evidence of many of the minor and medium landslides got away because of wasting processes over time. For knowing the number and volume of zonal slides, it is enough for the catalogue to contain massive landslides. Given several hundred landslide events and their magnitudes in a region, there will be many smaller magnitude events compared to the massive ones. These follow the relationship log NC = - bmL + a where NC represents the number of landslides with magnitudes greater than mL, and a and b are constants. The same method can be used for a single incomplete landslide event inventory where only the largest landslides have been measured and the medium and smaller landslides sizes are not know. Using the general landslide distribution we can extrapolate the frequency densities of the largest landslides in the event, and estimate of the equivalent landslide event magnitude. Malamud et al. (2004) related the landslide-event magnitude for individual events to the total area and volume of the maximum landslides [169]. They used the historical landslide inventories and made estimates of total area and volumes of landslides involved over time for each of the regions, and from these a lower bound estimate on regional erosion rates due to landslides. Landslides satisfy power-law frequency–area statistics. Certainly, landslide distribution is only approximate, but is it useful? The quantification of landslides serves to estimate erosional processes and assessing hazards. It is only in terms of a general landslide distribution that the landslide-event is

Ancuța Rotaru Habilitation Thesis quantified. Based on this distribution, a landslide-event magnitude scale quantifies landslide events. Distribution management controls the largest landslide areas associated with a landslide event. This approach should be useful to hazard managers who do not have the time and resources to derive substantially complete inventories. The one-meter depth temperature measurement detects the groundwater of the landslide. It appears more rational to identify the weak zones and apply the dilatancy criterion than adopting models with more than seven constants hard to control.

2.1.8.3. Stability analysis The major challenge for site-based stability analysis is the conversion of the factor of safety or equivalent stability assessment into a useful expression of hazard that can then be used as a component of risk assessment [80]. This involves employing the factor of safety along with temporal variability in triggering factors to determine the probability of failure per unit of time. Probability of occurrence, in turn, needs to be qualified by a statement of expected behaviour of the failure in terms of its impact characteristics [98]. Predicting the nature of the landslide, particularly for first-time failures, is another challenge for landslide hazard science [80]. Gravity-driven movement of earth material can result from water saturation, slope modifications, rainfall occurring after wildfire, and earthquakes [278], [373]. Techniques for reducing landslide risks to structures include selecting non-hillside or stable slope sites; constructing channels, drainage systems, retention structures, and deflection walls; planting groundcover; and soil reinforcement using geo-synthetic materials, and avoiding cut and fill building sites [375]. Design for the direct effects of a landslide is not cost-effective. Landslide and subsidence risk mitigation actions (Fig.19) [47]. Ground subsidence can result from mining, sinkholes, underground fluid withdrawal, hydro-compaction, and organic soil drainage and oxidation. Subsidence mitigation can be achieved through careful site selection, including geotechnical Fig. 19. Landslide risk mitigation actions study of the site [120].

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards

In subsidence-prone areas, foundations must be appropriately constructed, and utility lines and connections must be stress-resistant. When retrofitting structures to be more subsidence-resistant, shear walls, geo-fabrics, and earth reinforcement techniques such as dynamic compaction can be used to increase resistance to subsidence damage and to stabilize collapsible soils [14], [101].

2.1.9. Landslides in Romania Romania is the most affected European country regarding landslide risk (Fig.20). In Romania, landslides are priority hazards because they represent a significant risk to people and the environment. Many landslides in Romania have been reported as in conjunction with major floods and poor forest management. Most landslides result as a combination of poor forest management and intense rainfall. Romanian territory holds 238,300 km2. Romania includes a variety of landscapes resulting from its broad range of distinct relief forms, well proportioned: 36% Carpathian Mountains and Subcarpathians, 34% hills and tablelands, 30% plains. Altitude ranges from sea level to 2,544 m above sea level at the highest point of the Romanian Carpathians. The total estimated area of landslides covers about 800,000 ha, putting at risk 50,000 households, 250,000 people, agricultural land, public and private buildings, public utility networks and roads.

2.1.9.1. Characteristics of romanian landslides Serious hazards in Romania are sliding of soils resulting from excessive rainfall. They have claimed many lives and produced landslide damages in significant areas. An abundant number of populated areas are prone to landslide phenomena because of the accumulation of a series of negative factors. The analyse of variables which affect the evidence and evolution of such phenomena can establish the appropriate places for particular urban development. The outcome of such an investigation is the compilation of comprehensive maps that define the microzones of different landslide hazard. The following factors and variables need a thorough approach: (i) morphological condition; (ii) development, geographical distribution and nature of soil formation; (iii) spatial distribution and geometry of rock formation; (iv) the presence of superficial and groundwater and (v) other factors, like the human intervention.

Fig.20. Landslide risk in the European surveyed countries

Ancuța Rotaru Habilitation Thesis

Landslide causal factors form two groups: (1) precursory factors and (2) triggering factors. The former makes the slope susceptible to movement without actually initiating it, while the latter brings out the motion [166]. The trigger represents an external stimulus that produces an instantaneous change in the stress-strain relationships in the slope, resulting in movement [284]. The typical triggers of landslides in Romania are heavy rainfall or snowmelt, earthquake shaking, erosion or human factors. As the leading factors that control landslide, there are 1) geological conditions, 2) groundwater conditions, 3) geomorphological conditions, 4) climatic factors, 5) seismic activity, 6) weathering and 7) artificial factors [211]. In the rural environment of Romania, distinctly in mountainous areas, landslides represent critical hazards. However, landslides trigger mainly in the deforested hilly regions and tableland areas consisting of loess, sands and clays. Consequently, landslides in Romania concentrate in five broad areas: I. Transilvania Plateau; II. Getic Piedmont; III. Pericarpathian Hills; IV. Moldavian Plateau and V. Danubian side of Dobruja Plateau. In Romania, mass movements cause a significant hazard in the hilly and mountainous regions, particularly those underlain by flysch deposits (Fig.21). These deposits consist of complexes of folded and faulted sedimentary rocks containing marls, clays, shales, sandstones, and conglomerates. Various climatic, tectonic, and lithologic factors influenced by land-management practices ensure the distribution of mass movements in these deposits. There are significant regional differences among types of mass movements, the quantities of materials delivered from the slopes into adjacent stream channels and risks to various human activities. In the Subcarpathians, formed predominantly of folded and faulted molasse deposits, slopes may be unstable. The instability manifests itself by shallow (sheet) slides, landslides of medium depth and mudflows typically 300-700 meters in length. The areas most affected by these features lie within the curvature of Subcarpathians in Vrancea Seismic Region [244]. Landslides are widespread in many mountainous and hilly regions of Romania, particularly those underlain by flysch deposits. These deposits comprise complexes of folded and faulted sedimentary rocks containing marls, clays, shales, sandstones and conglomerates. Various climatic, tectonic, and lithologic factors influenced by different land-management practices ensure the distribution of mass movements in these deposits. Precipitations, slope degree, soil condition, land use and management are sources of landslides. Water pollution from mining pollutants from erosion and catastrophic releases are also facing by Romania [372]. In the Moldavian Plateau, the areas most affected by landslides occur on slopes built up of alternations of marls and clays, with intercalations of conglomerates and sandstones. In the Eastern Carpathians, predominantly formed of Cretaceous and Paleocene flysch deposits, periglacial or immediate postglacial colluvial materials are the prime sources of mass movements. These deposits count 10 to 30 meters depth, and landslides are activated or reactivated by a zonal deepening of the valley network in the long term, or deforestation practices. These landslides frequently affect towns, communication lines and roads because of their association with stream valleys, and may partially block valleys when they move. In the Moldavian Plateau, the areas most affected by landslides occur on slopes built up of alternations of marls and clays, with intercalations of conglomerates and sandstones. In the Transylvanian Plateau, heavy rains commonly trigger deep landslides. In the alpine belt of the Carpathian Mountains, the most widespread mass movements are rockfalls and rock avalanches. These processes are most common in the crystalline rocks on the steep slopes of glacial cirques and valleys. In the Subcarpathians, formed predominantly of folded and faulted molasse deposits, slopes are unstable. Fig.61. Areas with landslides in Romania The instability frequently manifested by (in light-blue, after http://www.geo-strategies.com/) shallow slides, landslides of medium

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards depth and mudflows typically 300-700 meters in length. The most affected areas lie within the curvature, in Vrancea Seismic Region. In the Transylvanian Plateau, torrential rains commonly triggered deep landslides. In Romania, slopes affected by reactivation of landslides are located in the Eastern Carpathians. Landslides occur in colluvial deposits 10-30 meters thick developed on Paleogene flysch. Oil production during the last years in the eastern part of Romania's Carpathian Mountains has added to the total number of drilling/production wells and led to such related activities as the construction of roads, platforms, and earthworks. Other harmful human influences include heavy traffic, forest exploitation, dirty water in wells, vibration in soils, removal of gravel deposits from rivers. Critical natural circumstances such as lithologic nonuniformity, heavy rainfalls or engineering works accelerate local predictability. It can lower the base level in the adjacent valleys by 1-2 meters, rising the slide potential. An example for the eastern part of Romanian Carpathian Mountains is the Zemeș landslide, which extends over 1.4 - 1.8 km in length, with a width of around 500 m at the slope base and a total change in elevation of about 350 m. Similar slides cover 30-40% of the land on both sides of Tazlaul Sarat Valley. They have developed especially on soft or altered rocks and almost always involve the quaternary deposits (coarse altered materials in a clay matrix). Unfortunately, these recurrent landslides produce an asymmetric shape to the valley, which increases the potential for landslide reactivation because of infiltration of water into the ground [92]. While some landslides move slowly and cause damage gradually, others move quickly destroying property and take lives suddenly and unexpectedly. Mudflows are common types of fast-moving landslides due to excessive rain. Various parts of Romania have been suffering from excessive rains (which caused flooding and landslides). From 9 to 25 June 1999 Romania excessive rains which resulted in swelling rivers, floods, landslides and waves of mud hit Romania through hillside village. Altogether 130 areas in 21 counties were affected, 19 people died (10 drowned and 9 struck by lightning) and 3 wounded; another 1526 houses and 3,262 house annexes damaged; 320 km of communal and rural roads affected, as well as 1 km of the national roadway; 185 bridges and platforms. Besides, 20 hydro-technical sites were ruined and electrical and telephone lines damaged. During 11-13 July 1999, torrential rains hit Romania again in northwest and northeast. Fig.22. Romanian Counties developping landslides Rains affected 47 regions in 10 counties; 15 people died, and landslides injured many people; 362 houses, 1280 offices, 624 households, 11 roads and 34 footbridges, 18 km of the county and national roadways damaged. The “victims” of landslides in Romania are agricultural lands, roads, county roads, railroads, and utilities, transportation or distribution networks, equally located in urban or rural territory. Romania locates in an active seismic zone. Many earthquakes occurred there in the past with magnitudes greater than 7.0 on the Richter Scale. So, earthquakes represent another dominant factor inducing landslides.

2.1.9.2. Romanian landslides – Case studies Many of Romania’s 41 administrative counties are prone to landslides (Fig.22).

2.1.9.2.1. Moldavian Plateau Botoșani County. Botoșani County includes 68 rural villages, 2 towns and 2 cities affected by active, in the course of reactivation or latent slidings. Of the total area of the county, 70% is at risk of surface

Ancuța Rotaru Habilitation Thesis erosion, which leads to additional active landslides producing severe damage to 15-20% of the land. Suceava County (Fig.23). In the town of Fălticeni, landslides began in previous years, but after excessive rains from June to July 2010, the ground saturated destabilizing the slopes, and landslides have reactivated. After flooding, waterlogged hillsides to Milișăuți take it down, with all the houses. A sector of the national road connecting Suceava and Rădăuți collapsed because of landslides. People waken up overnight by 8 m deep craters in the garden and under their homes. Neamț County. In Hangu, a picturesque areas of the Neamț County, landslides occurred in 2008. The unstable land because of groundwater seepage has taken down carrying-forward farms and forests. Torrential rain produced unpleasant consequences in Piatra-Neamț City regarding landslides from June to July 2010. The slope seepage at Cozla has softened the ground so far that the soil started to slide. Landslides affected the road towards Housewives Terrace connecting with the gondola arrival base. Iași County (Fig.24). In Iași County, 82 landslide risk areas identified [299]. The broadest regions affected by exacerbated land degradation [272] are on the steep slopes along Bârnova-Voinești-Strunga coast, steep slopes north of Târgu Frumos-Cucuteni-Hârlău-Deleni, and on the north and west slopes [254]. Landslides risk areas are Copou-Sărărie-Țicău in Iași City; Cotnari-Deleni; Bârnova-Dobrovăț; Comarna-Dolhești; Popricani-Probota; Miroslava area; Tomești area; Valea Seacă area. The areas affected by landslide increased from 15,000 ha in 1985 to 63,021 ha in 2005. Active and semi-active landslides affect approximately 26,000 ha.

Fig.23. Landslide in Suceava County Fig.24. Iași County landslide

Vaslui County. Since 1999, the landslide located in Jigalia Village quickly extended. A landslide also exists in Laza Village where the 30 years old sliding catches proportions. Galați County. A large-scale landslide destroying the superstructure of the hill and the railway line over a distance of 700 m took place just 5 km away from Galați railway station in Brateș Lake in 2000. The area is affected by the twenty-six years, and last massive landslide occurred in 1993, train traffic being interrupted at the time for almost a year.

2.1.9.2.2. Pericarpathian Hills Bacău County. In 2010 in Zemeş Village, 10 areas observed without interruption endangered lives in places with landslides. Mărgineni mudslide left without water four villages, while the landslide from the town of Moineşti activated a bank of earth that slid. Vrancea County. Vrancea landslides are the effect of large areas of deforestation. Recent landslide phenomena are reactivations of landslides occurred at least 30-40 years ago. Lately, landslide reactivation is the consequence of massive amounts of rainfall related to the relief and lithological substrate prone to such processes. In the event of moving-forested land, the reactivation processes have not exceeded 10% of the area. However, forestation demonstrates a maximum efficiency after 10 to 15 years from planting. Buzău County (Fig.25). In February 2010, landslides due to severe rain and melting snow affected three roads in Colți Village. The DC78 road was blocked by a landslide affecting the access to Muscelu Cărămănești Village in Balta point, 75 families remaining isolated. The DC71 road Colți-Aluniș at Râpa point was affected after an entire slope has taken down. Landslides equally affected the DC69 road. Prahova County. In January 2006, torrential rains happened in January have affected areas as Breaza, Sirna and Lapos. The access to the DJ 101 road, from Sirna village was closed because of damage to a

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards bridge. In 2009 landslides have been produced in 11 neighbourhoods of Prahova County. Suggestive are those triggered in the town of Comarnic, on DJ 101 road and those from Teleaga Baths, where the lake practically disappeared. Salt baths from Teleaga are well-known in Romania and abroad. Here thousands of people came each year to treat gynaecological diseases or rheumatism. In February 2010, 19 municipalities were affected by landslides in Prahova County: 5 cities, namely Azuga, Comarnic, Breaza, Boldești-Scăieni and Vălenii de Munte, and 14 villages. In Azuga, a bridge for pedestrian traffic built over the Azuga Creek, at km 135-136 on DN 1 National Road area, was damaged because of landslides. There, several pipes broke after bank deployment. In Breaza, five streets were affected. In Vălenii de Munte, landslides partially affected two roads restricting the heavy motor vehicles traffic on DJ 132 county road at Boldești-Scăieni. There, the ground split apart into two levels with 4.50 m difference between them. In the town of Comarnic, 12 houses were isolated and stuck by landslides and other six areas are affected by old landslides.

Fig.25. Landslides nearby Siriu, Buzău County Fig.26. Hunedoara County landslide

Dâmbovița County. In February 2010, several county roads were affected by landslides: DJ724 road destroyed over 800 m, DC10 road hit in three places, Gordun road damaged in two points. The communal road passing through Ștubeie Village damaged where the erosion occurred on the Tisa River stream banks. At Iedera, a landslide on the right side of the River Cricovul Dulce hit the DC9 road putting oil, gas and water networks out of service. Hunedoara County (Fig.26). Caused by floods, landslides occurred in June 2010 in two areas of Hunedoara County. The earth has slipped at Silvașu de Sus, affecting DJ 687C road, and in Certeju de Sus village another landslide triggered. Cluj County. The city of Cluj-Napoca has active landslides on Uliului Street, on Făget Street, on Făget Road and Valea Seacă. Cetățuia Hill area is prone to landslides, with buildings threatened by heavy rains. The present situation does not provide adequate prevention against this phenomenon. Sălaj County. In April 2009, a landslide triggered in Sărmășag on the county road linking Sărmășag and Chieşd. The landslide began slipping a year ahead, but the weather reactivated it, and the slope slid down more than half a meter.

Fig.27. Maramureș County landslide Fig.28. Sighișoara landslide, Mureș County

Maramureș County (Fig.27). Precipitation from June to July 2010 combined with runoff from slopes and infiltration of groundwater contributed to soil slip near the Mogoșa Lake. The landslide destroyed

Ancuța Rotaru Habilitation Thesis the large water discharger and formed a deep crater. Erosion is active, and land and water infiltration together with distinct settlements have contributed to land cracking, threatening the stability of the lake. A similar situation occurred in the early 1960s when the discharge of Mogoșa Lake caused damage destroying Baia Sprie town.

2.1.9.2.3. Getic Piedmont Argeș County. In April 2010 on DN7 National Road, in Morărești village, a landslide was reactivated, with involvement of a large amount of landmass. Landslides have occurred also on DN7 in Drăganu. Vâlcea County. In 2008, on the area of Vâlcea County landslides occurred in 18 localities, 22 homes being completely destroyed and another eight being cracked. In March 2008, after Panga North coal deposit from Mateeşti village destroyed eight houses in the Turcești village and affected tens of hectares of agricultural land, a landslide began to Panga South coal deposit. Because of the moisture, the landslide from Panga South has widened and advanced to the people's homes from Valea Mare. It was a sliding front that blocked an access road linking Valea Mare and Damțeni villages and affecting 7 ha of soil. In 2009, after heavy rains, the landslides of Olănești Baths were reactivated in two areas. The first landslide occurred on the county road DJ 656 at 2 + 700 km, in 2006, followed by another sliding on DJ 656 at 2 + 500 km. After this accident, the road has been reinforced, but reinforcing the river has never done. 60 households are in danger of sliding along the terrain. In danger of being destroyed are gas and water networks, and also electricity and telephone networks passing through the area. Gorj County. Seciurile village was severely affected by landslides in the spring of 2006. Then, 300 houses were destroyed. Landslides occurred due to mining work done in that area. The government built houses in two locations: Câmpu Mare and Cojani. Rainfalls from February 2010 facilitated the reactivation of a landslide having a few years old in Prigoria village. Mehedinți County. In January 2009, a landslide caused by heavy rains blocked the national road DN 67 D, between Baia de Aramă and Herculane. Rockfalls on the slopes blocked the DN57 road between New Orșova and Moldova, flooding over 2,000 hectares of farmland, pastures and meadows. In February 2009, landslides activated by recent rainfall isolated five municipalities in Mehedinți County. Two high voltage poles broke and obstructed the county road connecting Drobeta Turnu Severin City with Ilovița. In May 2009, the DN57 National Road connecting Orșova with Moldova Nouă locked away in both directions because of a landslide occurred at Sviniţa Village. In February 2010, rail traffic stopped on 990 Highway between Valea Albă and Balota stations since the railway embankment slide 30 m because of torrential rains and melting snow.

2.1.9.2.4. The Transilvanian Plateau Brașov County. In July 2010, a landslide occurred on DN1 National Road. The land bank of a wall collapsed at the roadside, near Mândra Village. The incident passes after a torrential rain with hail running a couple of hours. Sibiu County. In February 2010, the traffic along the Olt Valley blocked near Lazaret. Rocks, earth and tree roots fell on the slopes. Mureș County (Fig.28). Because of intense rainfall in June-July 2010, in Sighișoara City, Mureș County, landslides have been reactivated in hilly areas: Dealul Strâmb – Vasile Lucaci Street, Station Hill-Tudor Vladimirescu, and Yellow Hill-Caraiman and Ceahlău streets.

2.1.9.2.5. Danubian side of Dobruja Plateau Constanța County. Along the Danube-Black Sea Canal [21], landslides are active because of lithology and accumulation of water infiltrations from precipitations [219]. They occur when loess deposits contact over-consolidated fissured red clay. The ' 58 Km landslide' represents a progressive one [351]. The basal slip surface is seated in the red clay layer [215]. Recognition of the processes that triggered the movement is of primary importance to understand the landslide mechanisms. Many recent landslides reported their origin in Romania in conjunction with recent major floods and poor forest management [253]. In Romania, most slope failures occur during periods of unusually excessive rainfall or in spring when the snow thaws. However, exposure to rain or melting snow belongs to the typical existence of a slope. If the ramp is old, severe rainstorms or rapidly melting snow can barely represent the sole cause of

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards failure. It is most unlikely they are without any precedent in the history of the slope. They can purely be contributing factors [281]. Deforestation or an adjacent aquifer may produce an unprecedented increase of the highest elevation of the water table, associated with unprecedented pore-water pressures at the base of the clay. One of the two changes may account for the catastrophe. Dobruja region includes Constanța and Tulcea counties in Romania — 15,500 km2, one million inhabitants — plus Dobrich and Silistra in Bulgaria — 7,565 km2, 350,000 people. Dobruja is the easternmost region of Romania and the northernmost region of Bulgaria, lying between the northward course of the Danube and the Black Sea shores (Fig.29). Geoenvironmental natural risk phenomena in Dobruja are related to the local or regional forms of instability: landslides, soil liquefaction, and earthquakes [260]. Landslide risk represents the value of predicted damage from a landslide event of a certain level of risk. It expresses itself in terms of annual cost or the number of units (people) lost per year [281]. Dobruja geologic structure and climate promote landslides activated, especially by growing of the modern urban infrastructure along the Black Sea coast [278], [327]. The landslides are active along the Danube–Black Sea Canal. Stratigraphy, groundwater between loess and fissured red clay as well as inefficacious maintenance triggered them. The landslide from “km 58” (Fig. 4) is of progressive type [351]. The basal slip surface is bedding - controlled and seated in the clay layer [215]. Consolidation works consist of concrete reinforcements, rearrangements, drains at the base of the loess deposit and draining belts at the foot of the red clay [20]. The measurements started in early 2001. They have been conducted every month for eight months [84].

Fig.29. Geological cross section on km 58 landslide along Danube-Black Sea Canal

All the Bulgarian coastal strip measuring 30 km length and about 1–2 km width is sliding, from Varna City to Kavarna Town creating remarkable corrections of the shoreline [20]; [159]. The active landslides reflect in the specific relief with many adverse and favourable characteristics. Some territories suffered devastating effects while others have fallen into the sea basin. These landslides are ancients, significant, frequently activated, deep, measuring more than a few dozen metres under the sea and spreading a massive part of the steep coastal slope. The difference between the topmost and deeper parts of such landslides is up to 160-180 m. For example, the landslide triggered in Balchik Town originates about - 6.0 m depth in the shallow coastal part of the Black Sea Basin [158]; [262].

Ancuța Rotaru Habilitation Thesis

The landslide processes developed primarily in the Middle and Lower Sarmatian horizons. The only layers existing in the Lower Sarmatian deposit possess the following characteristics: reduced density, high plasticity and low shear strength. According to the plasticity index, the landslide material classifies as a clay. Undrained shear tests determine the residual shear strength because it is infeasible to drain the landslide zones in natural conditions [58]. The shear strength parameters obtained in this way for the deep-landslide zones named primary landslides have the following values: 7° the angle of internal friction and 6 kN/m2 cohesion. Coastal sectors with vertical or strongly inclined slopes are subjected to very intensive sea erosion – abrasion, altering their characteristics from stable to unstable ones [164]. The slope fundaments perish, and every soil deformation could provoke landslides, rockfalls, earth flows and significant collapse effects. Besides these processes, Neogene sediments, mainly the Sarmatian limestone, are subjected to groundwater and surface water erosion developing fractures, cavities and caves in the coastal zone.

2.1.10. Landslides repair and correction considerations If a slope started to move, the means for stopping the movement must adapt to processes triggering the slide. It is hardly an exaggeration to say that most landslides occur due to an abnormal increase of the pore-water pressure in the slope-forming material or a part of its base. Radical drainage meets the case. If the permeability of slides is too low to allow the drainage by pumping from wells or bleeding through galleries, the resistance against sliding increases and the ground movements stop employing the vacuum or electro-osmotic method. Both procedures create a reduction of the pore-water pressure associated with a permanent decrease in water content of drained strata which, in turn, increases the cohesion and shearing resistance of the ground. Similar effects arrive circulating hot, dry air through galleries located within the non-stable material. If the drainage success is doubtful, the ground movements stop either by reducing the slope angle or by constructing artificial barriers, such as retaining walls or rows of piles

Fig.30. Slope stabilization techniques

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards across the path of moving material. Every landslide or slope failure is a large-scale experiment that enables competent investigators to draw reliable conclusions regarding the shearing resistance of involved materials. Once a landslide occurred, data derived from the failure process allow reliable computation of the factor of safety and design modification. Increased development in hillside areas has underlined the importance of understanding the geologic factors promoting instability before the engineering analysis or repair begins. Too often, sites prone to landslides have been the scenes of repeated repair attempts within a few years. Experience over the past half-century suggests that many landslide repair attempts have no benefit or full understanding of the geometry and hydrologic regimen of the affected sites. Besides, the blind implementation of a traditional repair scheme such as re-compaction may not serve to mitigate the slope instability. The rational design of a landslide repair begins with the proper evaluation of sensitive factors of site geometry, which are: (1) the relative position of the groundwater table, (2) fluctuation of groundwater or subaqueous flow, (3) location of ancient/ active slip surfaces. Selection of soil slope stabilization techniques considers factors which use a decision support system and examination of the landslide (Fig.30). The number of alternatives for soil slope stabilization is large. It ranges from simple drainage measures, going through the use of bio-engineering techniques, ending with the traditional use of gravity and embedded retaining structures. Earth structures often apply to infrastructure construction works. Vegetation is one of the most economical and effective alternatives for the surface treatment of relatively flat slopes. The aesthetic impression for the public also gives a high advantage to choose the vegetation as a surface treatment. The calculation principles and interpretation of results use three alternative methods for slope stability analysis: 1) The traditional deterministic principle, 2) The partial factor principle and 3) The probabilistic approach. The traditional deterministic approach, with the calculation of one sole factor of safety, maintains the general advantages of being well established and easy to understand. For conformity to the current guidelines, this approach has to be replaced by the partial factor principle, with partial factors on actions and material strengths.

Fig.31. Slope stabilization techniques - retaining walls

Ancuța Rotaru Habilitation Thesis

The analysis of these alternative remedial measures for soil slope requires experience and sound judgment. In evaluating the alternatives, some factors influence the engineer: nature of failure, groundwater conditions; ground topography, environmental impact, material and equipment availability, design and maintenance specifications, adjacent and underground structures, time constraints, and costs. The ultimate decision will be unstraightforward. It will base on many associated factors and will frequently have significant cost implications and degree of success in terms of practical and meaningful result. Also, the information could be incomplete, imprecise and uncertain. The engineer may, therefore, have to develop decisions using empirical rules established from experience. Conventional slope remediation techniques alone may not be long-term sustainable due to significant initial capital expenditure and, in some cases, increasing maintenance demands. The integrated use of bio-engineering techniques and conventional methods may have advantages in the form of cost savings and sustainable solutions (Fig.31). If vegetation works complete at railway sites, they may influence the stability of earth structure. Insulating effects, especially against rainfall, should settle down to keep a safe mass-transport of the railway. Once it covers slopes, the vegetation can impede part of rainwater to go inside earth structures. After the rainfall, it can make an inside soil dry by effects of evapotranspiration. Targeting the bearing capacities induced by vegetation on the slope against rainfall, the following elements act as effects by vegetation: (a) Interception loss of partial rainwater before it gets under the ground; (b) Avoid erosions due to surface-runoff by increasing roughness on the surface of the slope; (c) Improve the ability of drainage of soil-structure; (d) Dry the inside soil and change of the moisture distribution by up-taking soil-moisture through roots; (e) Increase the shear strength of soil as soil - root adhesion and to reinforce soil by root-net. Because of the uncertainty and often variability of input parameters, the probabilistic approach possesses evident advantages. The recommendation is, therefore, to develop the most satisfactory basis for evaluation and perform probabilistic analysis as a supplement. A variety of tools are available for analyzing rock slope stability, and in theory, high accuracy calculation is possible for any situation. Typically, analysis is a stepwise procedure with the following three specific steps: 1) Definition of potential stability problem. 2) Quantification of input constants. 3) Calculation of stability. The steps that preface calculation are crucial for the analysis result. On the calculation principles, the interpretation produces significant development, particularly to new standards and guidelines like Eurocode 7 [387] and the increased use of probabilistic methods. A continuous recording of landslide movements demands to define the intricate relationship between the triggering factors and dynamics of displacement. The recognition of the processes triggering the movement is of paramount importance to understand the landslide mechanisms [375]. Climate change locally increases the intensity of rainfall, raising the frequency of fast-moving shallow landslides. Intensification of land-use management amplifies the hazard. Population growth and expansion of settlements and infrastructure over potentially hazardous areas have increased the impact of landslides. The enormous damage from landslides can decrease. The primary objective is to reduce long-term losses from these hazards by improving our understanding of the causes of ground failure and suggesting mitigation strategies.

2.1.10.1. Case study 1 – Zemeș, Bacău County, Romania The site is nestled in the minor riverbed of the Tazlăul Sărat River known because of its high landslide potential [261], Zemeș village, Bacău County. On the on-site visit, the followings were detected [286]:  the riverbed of the Tazlăul Sărat River was almost 50-60% blocked by large boulders as well as tree trunks and vegetation debris (Fig.32b);  remains of some ruined concrete walls and gabions (Fig.32a);  a landslide like a bank collapse impacted the road embankment [98]. It occurred due to water erosion of the Tazlăul Sărat River that undermined the foot of the slope over which the DC 130 road passes;

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards

 downstream the sliding area, in the riverbed of the Tazlăul Sărat River, there is a gravity retaining wall that maintains the concrete road embankment [364]. Its section next to the Fig.32. The Tazlăul Sărat River. a) remains of old concrete walls (left); studied area b) large boulders along the riverbed (right) underwent a GEO- type transfer following a horizontal translation (Fig.33a); the other sectors show structural degradation as well as tracks of a rotational GEO motion as a result of the sub-erosion of the foundation soil; currently, approximative 30-40% of foundation area appears in a console (Fig.33b). Geotechnical prospecting works reveal the following geological stratification as from the upper zone of the borehole to its base: 60 cm of boulders supported by 230 cm of weak clay bounded in a clay-gravel-boulder mix underlain by 90 cm of a gravel-bolder mix supported by 100 cm grey marl clay and Fig.33. The Tazlăul Sărat River. a) horizontal translation (left); the bedding composed of b) rotational motion, the foundation in a console (right) compact grey sandstone.

2.1.10.1.1. Intervention proposals It results that the activation of landslides is Table 6. Geotechnical input data for the on-site layers due to the following factors:  in time, the waters of the Tazlăul Sărat Layer Design approach 1 – Combination 2

River eroded the foot of the slope E φ d cd γnat ν supporting the DC 130 road, leading to its - kN/m2 ° kPa kN/m3 - failure by downfall; 1. Fillings 1.7E+4 19.65 14.34 18.50 0.30  the erosion process induced by the river 2. Boulders 5.0E+3 10.45 8.85 19.20 0.27 at the slope foot triggered the failure of 3. Sandy clay 2.5E+4 19.75 19.46 19.82 0.30 the existing retaining walls; currently, 4. Sandstone 4.0E+4 50.00 200.00 22.88 0.27 retaining walls downstream, near the collapsed area, provide stability;  a low percentage of foresting concerning adjacent areas;  counter slopes upstream of the road, allowing the surface water stagnation over long periods, influencing the local physical-mechanical characteristics of the soil layers in site. Stability calculations were performed using the Plaxis 2D programme with the Mohr-Coulomb constitutive model considered as a first order approximation of the real soil behaviour [58] and the "Phi- c reduction" algorithm [385]. In the Safety approach, Plaxis successively and monotonically reduces the soil strength parameters until the convergence of the boundary-value issue is no longer achieved [386]. Failure of the structure occurs (the soil collapses) introducing deformations. The lowest reduction factor producing non-convergence is reported as the “factor of safety” of the boundary-value issue. Table 6 pesents the input values of ground characteristics used by the linear perfectly-plastic model considered by the programme, namely Young’s modulus E, designed angle of internal friction φd, designed cohesion cd, natural unit weight γnat, and Poisson’s ratio, ν.

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Following the design concepts of the EUROCODE 7 [387], to ensure stability and adequate strength in the structure and ground, the analysis is carried out for the Design Approach 1, Combination 2 for the GEO ultimate state. The partial factors are applied to material parameters of soil and to variable load actions, and the remain coefficients are set equal to 1.0. Table 7 presents the values of stability factors for the stability analysis performed. Table 8 presents the values of theoretical total displacements for performed stability analysis.

Table 8. Displacements for Table 7. Stability factors for the stability analysis the stability analysis Proposed intervention Calculus Stability Total factor displacements [cm] 1. Without loading 1.48 57.95 I. Embankment restructuring 1.29 2. With loading 66.70

1. Support wall without 1.30 22.73 loading II. Minimal intervention 2. Support wall with loading 1.19 28.92 3. Erosion without loading 1.27 31.37 4. Erosion with loading 1.16 39.10 1. Pile wall without loading 1.75 5.14 2. Pile wall with loading 1.72 7.98 III. Maximal intervention 3. Erosion without loading 2.02 6.77 4. Erosion with loading 2.15 8.56

2.1.10.1.2. Results based on the stability calculations The following results arose (Table 9): Table 9. The variation of efforts for maximal intervention calculus  in the case of the slope in an Maximal Deformed mesh Bending Diagram Shear Diagram embankment without load, intervention moment force the failure occurs at the foot, [kNm] [kN] by hydraulic erosion; in the 1. Pile wall without case of the loaded slope, the 285 51 yielding surface has a loading

circular cylinder shape while 2. Pile wall failure affects the entire road with loading embankment. The stability 531 87

factors are only valid if the waters of the Tazlăul Sărat 3. Erosion without River do not erode the foot of loading 453 118 the slope; if they eroded it,

the stability factors have subunit values, which was the 4. Erosion with loading case on the site; 895 241  in the case of the slope of the

reinforced concrete retaining wall with a corner, a cylindrical circular yielding surface forms and extends in-depth covering the entire supported area; the erosion of the foot of the slope that would trigger the subsidence of the embankment in front of the retaining wall about 2.00 m is a critical situation; the formation of a yielding surface downstream of the retaining wall is noted, indicating the possibility of losing the stability and bearing capacity of the wall by GEO-type yielding when rotating;  in case of the retaining wall from bored piles, interspaced, supporting the embankment, the yield surface has a circular cylindrical shape that comes out just downstream of the retaining wall so that the road embankment shows stability; the erosion of the embankment foot, which could lead to about

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3.00 m high subsidence of the roadbed in front of the retaining wall, is critical; an increase of the stability factor due to the yield surface formed in-depth comprising the supported area is observed.

2.1.10.1.3. Intervention analysis All the three intervention proposed above invest stability on the site but analyzing the building technologies and conditions of service in time, the following have resulted: - remediating the slope of the road without requiring other protection works has applicability for a short term because of its erosion; on this account, the slope collapses again; - open excavations with depths of about 2,00 m (settlement depth + embedding depth) leading to 3.00 m high vertical excavation are necessary for the completion of the retaining wall as to apply the minimum intervention proposal; - the slope support system carried off at 5.00 m from the road embankment rest stable through earthworks; works for preventing the foundation soil scouring phenomenon performed to unclog the riverbed are necessary, with the disposal of the boulders recovered from the riverbed at the base of the support wall; as observed on the site, the discharge of the river leads to a notable landslide beneath the existing wall foundations (Fig.3); - completing boring piles to support the retaining wall is the best intervention solution regarding the road edge that assures stability to the embankment even though subsidence occurred 3.00 m downstream of the retaining wall. It is necessary to safely carry out the piles, unclog the riverbank, work out a slope on the embankment edge, and arrange boulders along the riverbank. Those supplementary measures confer slope stability during completion and service of boring piles playing anti-erosion function.

2.1.10.2. Case study 2 – Toplița municipality, Harghita County, Romania The case study refers to a 275 m length retaining wall of Măgura Street, Topliţa municipality, Harghita County, Romania, executed in 1940-1950 epoch, at which crest underpinning has been made in 2006. The retaining wall is located in the Mureș River Valley. The retaining wall is located in the northeastern part of Romania, in the central area of the Eastern Carpathians, in the Toplița Depression, in the town of Toplița, Harghita County [271]. The area has Fig. 37. (a, b) Existing retaining wall: missing/damaged parts heights of 1500-1700m in Gurghiului Mountains. Măgura Street is a coastal mountainous road 6.0 - 7.0 m width only. On Măgura Street, there is a stone masonry retaining wall of 275 m length (Fig.34 a, b). On certain parts on the right side of the road, there is another stone masonry retaining wall that stabilizes the area of individual houses [388]. The area settles on volcanic strata of sandstones, conglomerates, micro-conglomerates, sandstones and andesitic sands. On both sides of the Mureș River, starting with the northern extremity of the Gheorghieni basin, there are remains of the lower and upper terrace. The lithological composition of terraces includes sand and rolled gravel with schists, covered by diluvial-proluvial deposits of sandy clays or clayey sands. The thickness of the terrace deposits is between 5-15m in Toplița municipality. The retaining wall has an approximate height of 5 m, stabilized with buttresses. The retaining wall serves throughout its operation (so far) as an element of stability and strength to support the road (its left side) but incorrect operated and maintained. There are areas where parts of the retaining wall are missing or damaged (Fig.34 a, b), significant cracks are detected, which influence the stability of the massif. Rainwater created channels damaging the retaining wall and transporting the granular material. Consequently, there were landslides, entrainment of vegetation, weak areas in terms of strength and stability of the slope. Structural degradations of the wall, as well as collapses of the granular material

Ancuța Rotaru Habilitation Thesis due to the washing of the aggregates by floods during the rainy periods were reported. The systems for taking over the meteoric waters are unmaintained and clogged, and the vegetation has infiltrated its roots in the granular material of the retaining wall. The retaining wall is the stability and strength element that supports the road, but it was not properly operated and maintained. There are significant cracks affecting the slope stability which can be observed. Stormwaters created ruts and transporting granular material, damaged the retaining wall. Collapses, displacements of vegetation, or weak areas in terms of strength and stability of the slope can be noticed. Building a sidewalk on the left of Măgura Street, the City Hall of Topliţa, Harghita County, Romania requested a survey of the retaining wall because pedestrian access route is unsafe and uncomfortable at present, with no sidewalk set up. Investigations revealed that the Fig.38. (a, b, c) Discontinuities of the beam where the metal retaining wall structural damage and safety railing belongs parts collapse appeared in the rainy seasons due to washing aggregates of granular material by floods creating ruts. Systems for retrieving rainwater are poorly maintained and clogged, and vegetation has infiltrated roots in the granular material of the retaining wall. Both structural and nonstructural elements of the retaining wall suffered significant degradation during operation. The beam where the metal safety railing belongs has discontinuities causing rainwater to flow in an unorganised course (Fig.35 a, b, c). There is not a system for collecting the rainwater along the street. In the rainy seasons, the rainwater torrents coming from the high slope spreading on the right side reach the road and descend as floods washing the embankment of natural vegetation covering the retaining wall. The runoff had washed in this way, repeated over time, the soft, unconsolidated fabric of the slope creating gullies and infiltrating into the retaining wall what grows negative action on its stability and admissible settlements. The rainfall is not picked up by any system of drains being left to infiltrate chaotically water through the plant roots and gullies created in the granular material, thereby influencing the stability and settlements of the retaining wall. Here and there, collapses develop at the contact between the road and the beam placed in the metal safety railing, the material beneath the hard covering of the road being washed by the rain.

2.1.10.2.1. Intervention proposals Two intervention solutions consolidate the retaining wall of Măgura Street, Topliţa municipality, Harghita County. The first solution consists of the following steps: 1. To uncover the current slope in its integrity to the parament of the existing retaining wall. 2. Local repairs and strengthening of the existing retaining wall, where they are proper. 3. A continuous vertical drain of river rocks of 1 m thick, followed by a continuous horizontal drain of 1 m thick, with a slope at most 4% to remove the collected water from the base of the retaining wall. 4. Filling of ballast. 5. A 1.50 m width sidewalk protected by a pedestrian guardrail at the canopy of the retaining wall. 6. A new retaining wall to take over the displacements of the soil mass that the existing retaining wall is no longer able to take over. 7. An embankment of concrete stone pitching, 30 - 50 cm thick, from the end of the sidewalk to the top of the new retaining wall. 8. The new retaining wall will be provided with barbicans at not less than 2.50 m and waterproofed with fillerized bitumen at the contact with the slope and drains. 9. A drainage culvert in the outer area of the retaining wall footing. The second solution focused on the following goals: 1. To uncover the current slope in its integrity up to the parament of an existing retaining wall. 2. Local renovation and strengthening of the existing retaining wall, where they are proper.

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3. Clay fill, clay and gravel, ballast, at a maximum slope angle not exceeding 33° for safety reasons. One metre high at the base of the filler, 10-50 cm width steps on the slope made of existing material at an angle of no more than 3%. 4. The fill protected by geocomposites. 5. A 5-10 cm layer of humus spreads out over geocomposites. 6. Making a 1.50 m width sidewalk protected by a pedestrian guardrail at the canopy of the existing retaining wall. 7. Making a new retaining wall to take over the displacements of the soil mass that the existing retaining wall is no longer able to take over. 8. Carry out, behind the retaining wall, of a vertical stone drain at least 1m height, on which to place a reverse filter from granular material. 9. The new retaining wall will be provided with barbicans at not less than 2.50 m and waterproofed with fillerized bitumen at the contact with the slope and drains. 10. A drainage culvert in the outer area of the retaining wall footing.

2.1.10.2.2. Results Several results can be drawn:  The relief conditions of the studied perimeter on the Mureş Valley promote surface and intermediate drainage depending on the season.  The rainfall level determines the local hydrological conditions.  The specific weather in the area is favourable to carry out construction ditches, culverts for drainage, retaining walls, culverts and rainwater collection system. Sustainable rehabilitation of the retaining wall in Măgura Street, Topliţa is a priority, but both methods take into account the necessity of systems for retrieving rainwater to remove the collected water from the base of the retaining wall [52]. The first solution proposes the collection of the rainwater through a continuous vertical drain of river rocks no more than 1.00 m thick followed by a continuous horizontal drain not exceeding 1.00 m thick. Unlike that, the second method proposes a 1.00 m high clay fill at the base of the filler and 10-50 cm width steps made of existing material at an angle of no more than 3%. First method proposes a 30 to 50 cm thick embankment of concrete stone pitching between the end of the sidewalk and the top of the new retaining wall, while the second method advises protection by geocomposites.

2.1.10.3. Case study 3 – Pârcovaci, Iași County, Romania Pârcovaci locality, Iaşi county, Romania, is located west of the town of Hârlău. It spreads about 7 km along the Bahlui River [296]. The hills to the right of the Bahlui River are prone to landslides [11]. The regularization of the flood rates occurs under the management of the Department of Water Resources of the Prut River, through the Storage Lake Pârcovaci, a hydropower work installed at approx. 10 km upstream of the town of Hârlău. The landslide occurred in Pârcovaci village in early December 1996 (Fig.36). The landslide was profound, induced on a wide-spread area in continuous expansion, determining the damage of 97 peasant households out of the 186 located in the area. a) Characteristics of the landslide: The affected area is located on the right side of the Bahlui River, downstream of the Pârcovaci accumulation dam (2-3 km). b) Characteristics of the slide: the length measured on the steepest slope gradient up to the axis of the Bahlui River is about 2.5 km with the width of 1 km, with extension tendency [296]. The area strongly affected is about 250 ha. Geomorphologically, the area presents a very pronounced relief energy, there being a level difference between the Bahlui River bed and the ridge slope over 250 m. The slip surface comes into the site in the upstream area as very rough, with vertical cracks in the order of tens of centimetres. Vertical displacements attributed to Fig.369. Lanslide – Pârcovaci zonal collisions turned up, some with shallow overlaid Village, 1996 compressed layers, others through stretching due to the layer

Ancuța Rotaru Habilitation Thesis bending. In the order of several meters, visible slides through horizontal movements go out between the slip surfaces and seemingly stable areas. The general deep slip surface rounded with a partial sliding mass directed to the valleys of the torrents facing the Bahlui River. The area had high humidity as a result of the existence of the groundwater at shallow depths highlighted by a series of springs and a very high level of water in the local wells (1-1.5 m from the ground elevation). c) On the land affected by the landslide (250 ha), 186 peasant households (houses and annexes) settled down, and the rest availed for agricultural use and grazing. The peasant houses covered with tile, tin or asbestos cement held local materials (adobe, shallow foundations). The landslide affected 97 households (400 people) and destroyed a large number of houses (cracks in the walls and foundations of about 10-15 cm). The landslide changed the hydrostatic regime of the area, completely changing the directions of water movement, also having effects on the well water [261]. By raising the slope of the Bahlui River about 40 cm, the drainage slope reduced, the riverbed narrowed, which resulted in an accumulation of water upstream with the continuous rise of the level, leading to the danger of flooding 300 peasant households (1,300 individuals). The decrease of the flow section of the Bahlui River by sliding mass obstruction could have affected the normal functioning of the Pârcovaci storage lake (2.75-4.02 million cubic meters of water) preventing the taking-over of the floods from the winter-spring period. Measures: Deterioration of buildings made them unfit to habitation, endangering the lives of people, necessitating emergency evacuation, finding acceptable housing solutions in hygienic-sanitary conditions. The slip area being strongly fragmented and with sliding tendencies, it was necessary to allocate plots for new farms. To avoid the flooding of more or less than 300 households as well as the disturbance of the normal functioning of Pârcovaci storage lake by raising the Bahlui River thalweg and reducing its flow section, the riverbed of the water storage upstream of the slipped area necessitated urgent corrective measures. Technical improvements to limit the landslides and their effects in Pârcovaci village were: 1. Interception-collection-evacuation works of the groundwater from the plateau area carried out by the rapid capture and evacuation of the surface stagnant waters originated from heavy rains [261]. They employ interception drains, absorption drains, or spring water catchment chambers. 2. Interception-collection-evacuation works of the water within the slip surface originated from heavy rains through a network of open drainage collection channels, systematic drainage networks through absorbent drains, spring water catchment chambers, land modelling works, consolidation of slopes and the riverbed of the existing cloughs. 3. Anti-erosive roads and water-related works to consolidate the technological road platform through compaction and ballast addition. 4. 2.85km of marginal channels along to protect the road platform; 5. Nine platforms at the junction of roads with canals of which a paved bridge; 6. Consolidation of the river bank with a pitching wall on a concrete foundation.

2.2. EARTHQUAKES 2.2.1. Factors influencing building damage The buildings located on the glacial moraines, composed of poorly rounded pieces of limestone in clay and fine sand, are the most damaged in the earthquake. The buildings made on carbonate rocks are damaged the least. The damage mainly occurred because of the poor construction of old buildings. The database must consist of: geotechnical and geological profiles, surface accelerograms, response spectra and amplification spectra for three severe earthquakes recorded in the region in the last time. One of the main elements needed to be well known for seismic soil is the responses of future building sites. The site-response factor represents the numerical quantity that multiplies the amplitude of a reference wave motion to match the observed ground motion at the site. Site-response factor demonstrates how shaking varies depending upon the types of geologic materials. Generally, less amplification occurs in mountainous areas or firmer rock sites. Significant amplification occurs in basins which primarily contain alluvial deposits. In this manner, the softer sediments in a valley usually exhibit more intensive shaking than the hard-rock sites in the mountains. The majority of methods evaluating the seismic response rest on a soil deposit shaped like a pack of homogenous layers relying on a harder homogenous rock. Theoretically, this rock has an infinite thickness, and its the base rock. Nearly all of the ground motion prediction models employed in seismology assume the linear elastic behaviour of the ground during earthquakes. Most of the methods based on the hypothesis stating that

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards principal responses of the soil deposit occur because of the vertical propagation of shear waves from the base rock. The analytical procedures based on these models have provided outcomes following the real behaviour of the soil [174]. Seismic waves magnify by the low impedance of shallow soil deposits [270]. The engineering community long believed in the significance of the sediment nonlinearity. This perspective rests almost entirely on laboratory studies, where observed stress-strain loops involve a reduced effective shear modulus and increased damping (lower Q) at elevated levels of strain. A reduced shear modulus alone involves an increased amplification, depending on how it is measured. However, the increased damping typically tends to dominate, resulting in a reduced amplification, which involves less demanding building requirements. Soil amplification correction is introduced by a mere multiplication of the synthetic seismogram by the corresponding amplification factor. These factors are empirical, deduced from the records of weak seismic events or micro-tremors. There is no significant difference in the soil amplification on the light and intensive motion. Following the conservation of energy, seismic-wave amplitudes typically increase in sediments due to reduced densities and low seismic velocities. Resonance effects can occur where abrupt impedance contrast exists. If deposits were perfectly elastic, their response would be independent of incident-wave amplitudes. As with any material, however, sediments begin to yield at some level of strain. This violation of Hooke's law gives rise to a nonlinear response. Nonlinear effects have been exerted in engineering practice since the early '70s and account for current building codes. Examining the differences in S-waves velocities among various stratified deposits, it appears that the high-damage areas frequently correspond to prominent layers of low S-wave acceleration. Relevant damage and severe shaking equally occur to stiffer soils and S-wave relatively high speed. Layered structures more than 100 meters below the surface can be relevant contributors to site response. The curved boundary between a sedimentary basin and underlying hard rock can act as a lens causing at the surface an amplification of peak acceleration by 2-3 times over distances of a few hundred meters. It stands as one of the most relevant issues to understand and predict earthquake ground motion. Surface soils can be classified in terms of their response to the earthquake shaking, and site-response studies search for controlling the degree of linearity or nonlinearity of the soil response. For a linear soil, the observed motions at the surface proportionally amplify with the input ground motion. For nonlinear conditions, the soil tends to damp out more of the energy of large amplitude ground motions. Nonlinear behaviour in soft soils can reduce the intensity of shaking at high frequencies. Hence, in a severe earthquake, the nonlinear behaviour of the ground causes less severe shaking than the linear one. The most common evidence of nonlinearity of S waves represents the shift in the resonance frequency to lower values and the reduction in amplification [173]. Although sediments can amplify earthquake ground motion [111], there has been a lingering uncertainty whether the degree of amplification varies with the level of input motion or not. The effects of sedimentary basins on seismic waves are more extensive than the amplification and resonances caused by soft alluvium near the surface [293]. Complex interactions between the ground structure and the travelling seismic waves can increase the amplitude and time of shaking during the earthquake [291]. These interactions can focus the waves from the bottom of the area, concentrating the intensity of strong shaking in small regions at the surface while diminishing the severity on other sites. Additionally, the edges of basins can effectively trap incoming seismic waves increasing the length of time of shaking in the area. The most popular approach to calculate the attenuation of particle velocity in the soil is the cube root scaling of distance [218]. This approach makes possible prediction of the peak particle velocity when both the explosive charge and length vary. The scaled distance approach takes into account direct waves only. It does not consider reflections due to soil stratification and ground surface even if reflections from interfaces may enhance the peak particle velocity to a significant extent [238]. The attenuation with the distance of peak particle velocity (ppv) in soil without stratification: where: v, = ppv (mvs); f = explosive-soil coupling factor, namely, the fraction of the energy directed toward the ground (Kg); W = trinitrotoluene (TNT) equivalent charge weight (Kg); R = distance to the explosion (m) and n = attenuation coefficient that accounts for the influence of soil. The ppv decays exponentially in time giving to [36]: u(t) = vet" (2) If the wave met a layer with different impedance, reflections from interfaces significantly change the magnitude/ velocity of soil particles next to a buried structure. Compressional-wave reflections from interfaces with lower impedance, like the ground surface, reflect

Ancuța Rotaru Habilitation Thesis waves producing tensile waves that can reduce the amplitude of the incident compressional wave. Reflections from interfaces with greater impedance such as rock layers return as compressional waves, which can combine and intensify the incident wave field. For shear wave is assumed that reflections from interfaces of any kind produce waves that always contribute positively to the amplification of an incident wave [93]. An application of this conclusion is modelling large-scale problems implementing finite-element or finite-difference methods. If the distance between structure and explosion source is of a tenth of meters and its structure dimensions are large, a 3D model is necessary. In geotechnical engineering, structural dynamics substantially influenced by the ground local behaviour cause concern. So, the shear deformation in soil deviates from the linear elasticity above a particular acceleration. That is why nonlinear site effects consider the modelling soil response to seismic loading. A critical factor affecting intensity at a site represents the geologic material underneath the site. Deep, loose soils tend to amplify and prolong the shaking. The worst layers are loose clays (mud) and filled areas. The type of rock that least augments the shake is the granite. The remaining materials fall between these two extremes, with the deeper soils in the valley shaking more than the rock shakes in hills. The distance-based intensities mapped for each scenario earthquake are increased or decreased based on the shaking amplification potential of each geologic material to produce the final intensity maps. During strong earthquakes, loads can be so large that some deformations become unavoidable. Like a chain, a layered soil-structure system is likely to deform at the weakest link. A strengthen sand layer may transmit significant accelerations to overlying surface deposits and surface structures [38]. The interface between a thick deposit of medium-dense sand and an overlying impermeable layer is susceptible to weakening and lateral spreading because of pore pressures developed in the sand. Ultimately, they dissipate by water flowing upward. An impermeable layer limits the upward flow of water resulting in low effective stresses near the interface [250]. The water accumulation beneath relatively impermeable deposits due to the partial drainage can cause a weak zone to develop, with shear resistance much smaller than the undrained residual strength. The shear resistance at the interface will be a function of thickness, volumetric strain, and permeability of the underlying soil. Densification increases the stiffness and the shear resistance of the sand. Yet, stiffer is not necessarily better. Changes in stiffness induce changes in the soil deposit. Depending on the predominant periods of earthquake ground motions, the amplification may be increased or decreased by soil densification. Seismologists were sceptical that laboratory studies reflect in situ behaviour, both because of well- known difficulties in collecting undisturbed samples, and because such analysis does not include the effects of scattering attenuation [252]. Given a lack of evidence for sediment nonlinearity, seismologists opted for the simpler linear model. But, nonlinear amplification at sediment sites appears to be more pervasive than seismologists used to think [38]. This new perspective bases on the nonlinear effect in data from the 1989 Loma Prieta earthquake. In this perspective, Hooke's law is only an approximation, especially because some degree of nonlinearity is apparent in laboratory studies at even the lowest detectable strain levels. The question is more a matter of degree or the adequacy of the linear model under various conditions, especially in comparison with other commonly made approximations (such as isotropy). The question is: when is sediment nonlinearity, from the geological engineer point of view, the first-order effect in terms of understanding or predicting earthquake ground motion? Some specific issues to respond to this question: 1) Do laboratory studies reflect in situ behaviour? 2) Is nonlinearity in rock or very stiff soil significant? 3) Are multi-dimensional effects (in terms of sediment-deposit geometries) and P/SV-wave coupling effects relevant? 4) Is sediment nonlinearity significant at extended periods (greater than one second)? Will it reduce the severity of near-source effects? 5) Is soil stratification significant? The election of the method to decide the ground response to seismic excitements depends on the configuration of the soil deposit [37]. If all the frontiers of a stratified or homogeneous deposit are horizontal, the ground acts as a series of semi-infinite strata. This way, the analysis presents a one- dimensional problem. This technique identifies with the model of the vertical shear beam [238]. On the other hand, if the deposit presents irregular or inclined interfaces between each layer, a procedure that takes care of the two-dimensional aspects of the problem is needed. An appropriate method is the Finite

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Element Method. The fundamental concept of nonlinear soil behaviour comes from the vibratory tests on soil samples performed under laboratory conditions showing that soil shearing deformation follows the hysteretic low. Stratification and nonlinearity stand one of the final frontiers in our understanding of site effects. People need conducting more laboratory tests to reflect in situ sediment behaviour and more dynamic-range recordings to infer behaviour at all frequencies of interest.

2.2.2. Liquefaction Liquefaction represents a phenomenon in which the strength of a soil decreases by earthquake shaking or cyclic loading [288]. Liquefaction has been responsible for tremendous amounts of damage in historical earthquakes around the world. Liquefaction occurs in saturated soils in which water fills the space between particles. The water pressure exerted on soil particles also influences the tight inter- particle pressure. Generally, the water pressure is relatively low, but the shaking cause the increase of water pressure to the point where soil particles move to each other. The earthquake shaking is the main cause of water pressure increase, but building activities such as blasting can also increase the water pressure. When liquefaction occurs, the strength of the soil decreases and the capacity of a soil deposit to support foundations for buildings and bridges reduces. Liquefaction soil also exerts higher pressure on retaining walls, which can cause them tilt or slide. This motion cause settlements and destruction of structures. The increase in water pressure can also trigger landslides and cause the collapse of dams. The effect of liquefaction commonly occurs in the low-lying areas of saturated soils, near water bodies like rivers, lakes, bays or oceans. It includes a massive sliding of soil or light movements producing tension cracks [267]. Consequently, harbours frequently locate in areas sensitive to liquefaction. Routinely, they utilize retaining structures or quay walls. When the soil behind/beneath the quay wall liquefies, the pressure on the wall increases, producing the slide/tilt of the wall in the water direction. For bridges, liquefaction-induced soil motions can push foundations out of place to the point where the spans lose support or compress to the buckling point.

2.2.2.1. Conditions in a soil deposit before an earthquake A soil deposit consists of a sum of soil particles, each particle being in contact with neighbouring particles. The weight of the overlying soil produces contact forces between particles. These forces hold discrete particles in place and give soil strength. Liquefaction occurs when the structure of a loose and saturated soil breaks down due to some dynamic loading. The separate soil particles, loosely packed, try to move into a denser arrangement. During an earthquake, there is no time for pore water to squeeze out, but it prevents particles move closer together. An increase in water pressure reducing the impact forces between the soil particles accompanies this phenomenon softening and weakening the soil deposit. In terms of high water pressure, the impact forces are small. At the limit, the pore water pressure may become so high that many of the soil particles lose contact one to another. Accordingly, the soil behaves like a liquid.

2.2.2.2. Criteria for liquefaction The factors affecting the liquefaction of soil are: Grain size. Fine and uniform sands are more predisposed to liquefaction than coarse-grained ones; the more porous soil will allow the build-up in pore pressure to dissipate, so liquefaction will not occur freely. Initial relative density. If the initial density is relevant, chances of liquefaction reduce. Vibration characteristics. Under steady vibration, the maximum pressure develops after some time, in contrasts with shock loading where whole strata can liquefy at the same time. Horizontal vibrations are more relevant than vertical ones because they lead to broader settlements. During earthquakes, shaking in more than one dimension at the same time causes the increase of the pore pressure faster than a one- dimensional shake. The effect of an earthquake causes minor displacements of the soil particles and this, in turn, causes the soil to become denser. As a result of densification, the pore pressure rises weakening effective stresses. As the pore pressure increases, the effective stress decreases. The strain

Ancuța Rotaru Habilitation Thesis achieves the critical value, and failure occurs. Therefore, the soil overcomes its resistance to move (the friction between the soil particles decreases). Since the shear strength of the sand is dependent upon the internal friction between particles, the soil strength reduces or does not manifest in some cases. The shaking forces caused by the earthquake add up to the shear forces already present in the ground. When all stresses transfer to the pore water, the soil behaves as a viscous material so that structures over it sink or tilt. The amount they move depends on both the viscosity of the liquefied soil and how long it keeps liquefied. Local ground structure. This characteristic can decrease the ground quality. An epicentral area is mostly composed of carbonate rock (limestone and dolomites) transformed into marl from place to place. Carbonate rock is a favourable ground, while marl is somewhat worse. In seismological terms, the worst soils are river and creak alluvium and talus slopes. Glacier morainic gravel is also unfavourable. All of the most damaged locations are, without exception, built on such sediments. The characteristics and influences of earthquakes in the mountainous areas differ in many ways compared to earthquake characteristics occurring in plains, along the coast, or in hilly areas. The main feature of the mountainous region is its structure, as it is composed of hard rock, forming very steep, even sub- vertical slopes. Above all, a mountainous area, in particular, presents unstableness of the steep slopes, e.g. falls and solids of rock masses. The earthquake effects in mountainous areas extend to more than several years when rockfalls and other phenomena of rock instability can appear during aftershocks, rain, wind, avalanches or while walking or climbing over unstable areas. Drainage and deposits. If a deposit has large dimensions (deep layers), the increased drainage path causes the soil to act as an undrained soil under rapid loading as occurs in an earthquake. Drainage helps a sand deposit with a risk of liquefaction to stabilize since the drainage path reduces and allows the pore pressure to dissipate. Magnitude and nature of loads. When significant effective stress applies to the soil, vibration intensity or the number of particular stress cycles must be large enough for stress to transfer to pore pressure. The initial representative effective stresses reduce the possibility of liquefaction. Period of loading. Because of cementation, liquefaction increases up to 75% under a loading in sand deposits, undisturbed for long periods. Previous strain history. If the soil previously complies with stress, the resistance to liquefaction increases. Trapped air. The trapped voids help the pore pressure excess and reduce the risk of liquefaction. The material. A component of the liquefaction hazard is estimating the shaking needed to trigger liquefaction. The answer bases on the susceptibility of the material to liquefaction. In this way, a material moderately susceptible to liquefaction may liquefy in areas with moderate shaking, but other moderately susceptible adjacent material may not. The key idea is to quantify this relationship to estimate the liquefaction hazard. The most artificial fills extremely susceptible to liquefaction are the mud-fills, materials significantly amplifying shaking [135]. Distance from earthquake source. In the '70s and '80s, shaking effects were estimated by relating earthquake magnitude to the maximum distance from the earthquake source for liquefaction effects. Shaking intensity. Other efforts to estimate levels of ground shaking needed to trigger liquefaction have used shaking intensity, a measure of the effect of an earthquake at a specific location. The modified Mercalli intensity scale defines the shaking level in terms of damage. Qualitative assignments of the relative liquefaction hazard for various combinations of liquefaction susceptibility and shaking intensity sets up. Some sites develop very high earthquake magnitude that triggers liquefaction. The distance from the fault source progresses liquefaction susceptibility during an earthquake, and the soil liquefies when exposed to robust shaking. The liquefaction of materials less susceptible triggers during powerful shaking only. Soil strength. When a shear force applies to a dry sand sample, the soil densifies reducing the volume. The amount it reduces depends upon the initial density; displacement/volume curves for two sand samples show the opposite. The shear strength of the soil depends upon the friction between the sand particles. In turn, friction depends on the applied normal stress. The greater the normal stress, the greater the friction. When the sand voids contain water, the strength reduces. The water quantity in the soil adjusts the amount of air reduction. The total stress reduces to effective stress. When a layer liquefies, the ground loses strength triggering movements of large soil blocks (lateral spreading), causing damage to manufactured structures.

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Other factors affecting the liquefaction of soil are volume pore pressures in soil during liquefaction and the displecement before and during the earthquake. In situ proof of liquefaction may lack because of depth and small thickness of liquefied layers. Ground cracking without venting of sand is more likely to produce as the depth and thickness of the liquefied layer increase and decrease, respectively. Minimum width of the improved zone should be twice the thickness of the liquefiable layer [135]. Lately, the liquefaction of soils has been the subject of laborious research. As a consequence, a significant database exists on the liquefaction of soils [116]. During an earthquake, it is relevant to know whether the ground is liquefiable or not. From this point of view, there are some criteria to obey: a. To compile existing shallow geologic and soils data, subsurface and borehole data, and historical records of earthquake-induced liquefaction. b. Near-surface conditions are seasonally dependent. In some cases, groundwater data gather by depth measurement to the water surface in streams, creeks, and drainage ditches. These measurements assume the stream level is representative to the level of shallow groundwater in the area. c. To compile the existing liquefaction hazard data. d. To obtain historical accounts of liquefaction in the area including reports on the previous earthquakes. Information on the behaviour of certain types of deposits gets from intensively studied earthquakes. e. To compile data on building damage due to earthquakes, hazardous materials issues, highway system disruptions, water and gas pipeline breaks and road damage. f. To match Quaternary geologic deposits depending on the available mapping and population density with stratigraphic conditions. g. To explore data on sub liquefaction of subsurface data and prepare the liquefaction susceptibility maps. Liquefaction susceptibility ratings include: very high, high, moderate, low and very low. “Very high” rating belongs to areas of known historical liquefaction and saturated artificial fill. Low rating occurs to units pre-dating the latest Pleistocene, not liquefiable, or zones with the groundwater below the critical depth for Holocene or latest Pleistocene deposits. h. To prepare the liquefaction potential or liquefaction scenario maps. After establishing the relative susceptibility of the various units, the estimation of the relative frequency of occurrence of ground shaking sufficiently to produce liquefaction depends upon a technique. The old method base on earthquake magnitude, distance from active faults, and recurrence intervals. The modern method indicates an element of directivity included in the critical distance as a variation of damage focusing the energy along the fault in the direction of rupture. The analysis of past liquefaction damage syllogizes to include directivity in the liquefaction mapping. i. To develop information on materials used to interpret the revised maps. f. To match Quaternary geologic deposits depending on the available mapping and population density with stratigraphic conditions. Damage to structures like buildings, bridges, and waterfront structures can be severe because of settlement and lateral spreading associated with liquefaction. Liquefaction is one of the Major causes of ground or geotechnical failure in earthquakes. Criteria triggering liquefaction for various categories of deposits demand increased research. Such kind of research improves the reliability of the regional liquefaction hazard mapping.

2.2.3. Seismicity of Romania Romania is a moderate-high seismic area, and its history reminds of frequent disasters caused by earthquakes. The movements of tectonic plates are reasons for Romanian earthquakes, especially in Vrancea County; but the geological structures cause the entire territory to be seismological active. Based on the geographical distribution of the seismic activity, the Romanian territory divides into seismogenic provinces as Vrancea, Banat, Crișana, Maramureș, Moldova, Transilvania, Westem Muntenia, Eastern Muntenia and Dobrogea. Based on tectonic units and seismicity features, the Romanian territory classifies into distinct seismogenic zones (Fig.37). To the east, the earthquakes are related to the subduction process at the Carpathians arch (Vrancea region); to the west, they follow the contact between the Pannonian Plateau and the Carpathians mountains [137]. The western side of the Carpathians (Apuseni Mountains) is aseismic as the eastern side is except for its southern extremity (Vrancea region). The southern Carpathians are significantly more seismically

Ancuța Rotaru Habilitation Thesis active, especially in the eastern and western sides. The plateau regions are stable, except the small strip crossing the Carpathians foredeep area on an SW — NE direction, in front of Vrancea region.

Therefore, the Transylvanian Plateau is almost aseismic at present. The small isolated seismogenic zone established there is defined based on historical earthquakes. Vrancea region puts at least three tectonic units in contact: the East European plate, Intra-Alpine and Moesian subplate. In Romania, the strongest earthquakes concentrate at intermediate depths (60 — 200 Km) in Fig.37. Romania’s map of seismic risk an old subducting slab almost vertical. For this region, the historical records of subcrustal earthquake events date more than a millennium. During this period, at least 37 severe earthquakes with a minimum intensity of VII on the Mercalli Scale recorded. That intensity represents the level/threshold at which the tremors bring damage. For building securely in Romania, the Sand and gravel, vp=1700nv/s, vs=694.54rn/s, construction industry needs data about ρ=1.9g/cm3 local conditions beyond the standardized

seismic codes. These data become even Clayey marls, vp=2100m/s, vs=940m/s, 9 more important for the regions oriented 3 ρ=2.1g/cm N-E, S-W with Vrancea region. Ultimately, densely populated areas in 3 Sandy clays, vp=2600m/s,vs=1080m/s, ρ=2.2g/cm Romania need a database. The database consists of the geotechnical and geological profile, surface accelerograms, response spectra (5%, Grey densely marls, vp=3050rm/s, vs=1245m/s, ρ=2.35g/cm3 10% and 20% damping) and amplification spectra for three violent earthquakes recorded in the region in the last century. The characteristics of the 3 Marl, vp=2400m/s, vs=1350m/s, ρ=2.4g/cm Romanian earthquakes derive in the number and variety of consequences drawn on the landscape, ranging from rockfall to slight cracks in the rock itself. To establish the influence of the Fig.38. Geotechnical profile of the city of Bacău geological condition on the increase of the earthquake effects, not only the damage to the architecture but also the landscape is relevant (Fig.38). Determination of increased earthquakes effects needs a Geological map as well as many other data on geological, geomechanical and geophysical ground/soil attributes. Seismicity beneath Vrancea distinguished by the incidence of intermediate-depth earthquakes in a narrow epicentral and hypocentral region. The epicentral area is confined to about 30 Km x 70 Km. Severe earthquakes occur from 70 to 200 Km depth within an almost vertical column. Earthquakes have recurrence times of 10 years for Mw > 6.5, 25 years for Mw > 7.0, and 50 years for Mw > 7.4. Historical data indicate 3 earthquakes/century with Mw > 7.2 and 6 events/century with Mw > 6.8.

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Romanian earthquake characteristics consist of a wide variety of consequences on the landscape, from large rockfall to cracks. To establish the influence of geological conditions on the increase of earthquake effects, the damage produced to architecture and landscape must count [374]. Two significant approaches can evaluate the local seismic hazard: (a) a collection of recorded intensive motion data for engineering purposes and (b) advanced modelling techniques allowing seismic input computation. It compensates the lack of intensive motion records, available only for events that occurred in the last 40 years. Alongside a geologic profile representative for Bucharest area, the presence of deep alluvial sediments influence the components of the motion, the most significant local effect being visible in the transversal (T) profile. Details of local impact vary with the earthquake motion, R and V components being very sensitive.

2.2.3.1. Geological structure and seismological conditions There are many consequences related to earthquakes; restricted to independent effect, everyone influences the others. Most often, direct aftermaths on people mind only, forgetting the others. This approach is appropriate for densely populated level areas. However, in a sparsely populated alpine area, seismic impacts treat differently modern technology serving to estimate the increased earthquake effects. Digitized maps like Geologic map, Engineering-geologic map and Soil Map with seismic attributes reflect the spacial data of geologic structures as well as soil properties. The information about layers correlated with the damage and soil structure combines into final prediction. The modelling results show a significant correlation between the earthquake consequences and soil structure, plotting the seismic micro-zonation map and predicting the forthcoming earthquake impact. At the same instant, it helps the reconstruction of damaged and current buildings to mitigate earthquake effects. Another analysis that takes into account the damage caused on landscape induces the landslide, falling rock and stone areas at risk which threaten the area stability [113]. At present, there are many methods to compute the seismic response at the surface of the earth, the majority based on soil deposit modelling. Between them, the pack of homogenous and horizontal layers relying on a harder rock, also homogenous but theoretically with infinite thickness, the so-called „bedrock”. Most of these methods based on the hypothesis that the responses of the soil deposit are consistent with the vertical propagation of the shear waves from the bedrock. Analytical procedures based on these models/hypothesis considering the nonlinear behaviour of the soil have given results per in situ behaviour. The methodology determines the variation of G (shear modulus) and D (damping) with shear stress in each layer. The strain develops due to seismic movements. The shear modulus and damping strain functions use as input data to compute the response of the soil deposit. To achieve this aim, samples are tested in the resonant column and triaxial. As input data for layers, the study used data from geotechnical (Fig.1) and geological profiles of the city of Bacău, an industrial and cultural city in Eastern Romania. Computation on site: 1) Vrancea surface accelerograms on 30 of August 1986 (7.2 Mw), 30 of May 1990 (6.9 Mw), and 31 of May 1990 (6.4 Mw); 2) the response spectra, damping of 5%, 10% and 20%; 3) the amplification spectrum from bedrock to surface. As the seismic motions recorded in urban areas develop rather scarcely, the database for the city of Bacău use is to assess the seismic hazard and seismic site impact for micro-zonation and shake map purposes. The experience in eliminating the consequences of the 1977 Romanian earthquake that involved a wide national area showed the elaborate way taken to act. The main measures in the activity regarding the post-earthquake renovation of buildings and stimulation of development in the area stricken by the earthquake include the reconstruction or removal of the damaged buildings, construction of entirely new buildings as well as the reconstruction of buildings used as infrastructure, trade activities and other public services. A conflict about how to rehabilitate buildings and construct infrastructure without threatening the environment and its natural beauty has appeared. To use the funding without dissipation and protect nature, the influence of geological conditions on seismic effects needs identification, and the effects on animate and inanimate nature become of great importance.

2.2.3.2. The earthquake influence on environmental damage The Romanian earthquake on March 04, 1977, triggered over 100 large geoenvironmental phenomena. They divided into phenomena of a lost equilibrium and the appearance of damage to the rock itself. Both phenomena connect when the destruction causes loss to natural stability. The lost of natural steadiness divides phenomena into falls, slides, rolling and bouncing of stones, rock blocks and talus

Ancuța Rotaru Habilitation Thesis on the one hand and cracked rock/rockfalls, planar and wedge failures on the other hand. Rockfalls and rockslides differ according to their size (Table 10). Their dimensions are from small to medium and large to regional. The higher the intensity of an earthquake, the higher the number of large-scale phenomena. The list of events giving the classification presents related groups and earthquake intensity.

Table 10. Phenomena occurring to rock during earthquakes a. Phenomena of losing the natural equilibrium of the b. Damage to rock itself rock 1. Phenomena in poor rocks and 2. Phenomena in Openings of short fresh joints in the rock slope deposits massive rocks Falls of individual stones Rock blocks Falls of individual rock blocks Planar failures Movements of rock blocks on gently sloping areas Slides of talus and weathering cover Wedge failures Openings of long fresh joints Landslides Rock blocks turning over Mud and stone flows Splitting of rock blocks Large crumbling of stones Large falls of rock blocks

The Vrancea region is responsible for the most destructive effects experienced in the Romanian territory. It can severely affect high-risk construction located on an expanded area, from Central to Eastern Europe. The region distinguishes by focal depths bigger than 60 Km. It is the most active seismic zone of Romania, with past historical earthquakes of 7 - 7.7 Mw on the Richter scale. The 7.4 Mw earthquake occurred on March 4, 1977, was the last relevant Romanian event with a lot of life losses (approximately 1.500 dead people) and consequential damages. Other recent significant Vrancea earthquakes were on August 30, 1986 (7.2 Mw), May 30, 1990 (6.9 Mw), May 31, 1990 (6.4 Mw). The volume of seismic activity is relevant for seismic hazard analysis at the regional level (southeastern Europe) and national level (Romania and Bulgaria) as well as for micro-zonation of densely populated cities. These data become more important for the regions oriented N-E, S-W, the directivity of Vrancea earthquakes. The city of Iași, significant industrial and cultural town in the North-East of Romania, locates on this direction (N-E, S-W). Since about four destructive earthquakes occurred every century in Vrancea, the micro-zonation of Bucharest, a capital exposed to damage due to strong intermediate- depth shocks, represents an essential step.

2.2.3.3. How to build Some general characteristics of the inspected buildings: * Foundations: The most damaged were the buildings without or very slight foundations, then the buildings with stone foundations. The most resistant were the buildings with concrete foundations. * Walls: The most damaged are the buildings having stonewall, then those with walls made by hybrid materials, then buildings with brick walls. The most resistant remain the buildings with concrete walls. * Year of construction: In Romania, the most damaged were the buildings built before 1914, then those built between the two World Wars (from 1914 to 1945), then the buildings made between 1945 and 1977. The most resistant are the buildings erected after 1977, which obey the earthquake-resistant construction regulations in all regions of the country. The year of construction influences the damage. Most damage occurs on buildings constructed at the beginning of the century and until World War II. For most of the buildings, the damage was either negligible or slight, but not structural. Losses during the Romanian 1977 earthquake were huge: about 2,000 lives lost, some 30,000 apartments heavily damaged, and more than thirty buildings collapsed [374]. The 1977 earthquake drew attention to the significant vulnerability of unprotected buildings, but it also highlighted the efficiency of earthquake engineering design rules. While 7% of the (approximately 400) pre-war-rise buildings in Bucharest collapsed, the earthquakes destroyed only one in ten thousand apartments designed to resist. If the area is affected by the intensities of VII or more, the incidence of collapsed apartments is three- to-four times lower. Even the damage occurs for most of the buildings located on slopes at more than 20-degree inclination, the screen of the inclination influence on damage level is not possible. Engineers have developed several ways to construct earthquake-resistant structures. Their techniques range from extremely simple to complex. For reinforcing small to medium-sized buildings, some classic approaches include bolting foundation and support walls (shear walls). Shear walls made of reinforced

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards concrete help the structure to strengthen and resist rocking forces. Shear walls in the centre of a building, often around an elevator shaft or stairwell, form what it is entitled a shear core. Diagonal steel beams can also reinforce walls utilizing a cross-bracing technique. Additionally, builders secure medium-sized buildings utilizing devices as shock absorbers between the structure and foundation. Base isolation absorbs part of the lateral movement, otherwise it could damage the building. Skyscrapers require a peculiar structure to make them earthquake-resistant. They must provide deep anchors securely embedded into the ground. They need a reinforcement framework with stronger joints than an ordinary building might have. Such a framework makes the skyscraper strong enough, yet flexible enough to withstand an earthquake. Flexible joints must peculiarly reinforce the gas and water lines to prevent breaking.

2.2.3.4. Earthquakes in Dobruja region The first step in Dobruja geoenvironmental risk analysis involves the risk identification of all potential causes or actions with undesired consequences that may affect the area [241]. The next step depends upon the risk assessment, while further steps address issues like risk evaluation to select the most suitable approach for the reduction of unacceptable risks [242]. Finally, the mission is to integrate the hazard into the geoenvironmental impact assessment. Besides the seismic activity of Vrancea (Romania), the Vidraru – Snagov (Romania) – Shabla (Bulgaria) tectonic fault line that extends under the Black Sea has been reactivated, making it able to produce earthquakes with severe effects, especially in Dobruja region. The most significant Dobruja earthquakes registered in North Dobruja and coastal area of South Dobruja, from south Mangalia, Romania to the east of Cape Shabla, Bulgaria (Fig.39). Regarding the coastal zone of South Dobruja is noteworthy that sometimes earthquakes reached 7 to 7.5 degrees on the Richter scale producing a devastating effect [316]. In response to the characteristics of Dobruja soils, earthquakes stimulated liquefaction and landslides at times. The beaches of Eforie, Costinești, Olimp, Venus, and Cap Aurora – Romania have equally been affected by erosion resulting from the significant quantity of rainfall. Consequently, the sand has been washed and the cliffs collapsed triggering massive amounts of weathered rocks. Inadequate irrigation systems increased the piezometric levels in South Dobrogea (3-10 m) allowing contaminants to enter into the groundwater [295]. The actual cinematic of Dobruja structural units is under the Alpino-Carpathian-Pannonic system, Vrancea geodynamic area and crust movements triggered by the post-rift phase of the Western Black Sea basin influence [40]. A variable sinking of the terrestrial crust of -2.5 mm/year produced at the Romanian Black Sea Fig.39. Dobruja Region. Tectonic activity. shore near Constanța City and around -1.0 mm/year towards Mangalia City [220]. North Dobruja Alpine orogen is bounded southerly by the transform fault Peceneaga – Camena and northerly by Sfântu Gheorghe fault [279]. Dobruja earthquakes along Capidava – Ovidiu and Horia faults and along the transverse boundaries near Medgidia (Romania), registered since 543 A.D. The seismic analysis for 1872-2006 period (134 years) indicates 30 events (0.223 events/year), maximum magnitude Mw = 4.7 (06/06/1906), an average focal depth of 12 km [88]. Although seismological recordings led to several poles, major earthquake epicentres located in northern Dobruja and its southern coastal area, from South of Mangalia City, Romania to East of Cape Shabla, Bulgaria (Fig.40). Dobruja terrestrial crust varies between 38 km thick in its northern part and 30 km thick in its southern part. Consequently, the Dobruja region experiences shallow earthquakes emerging at less than 40 km depth, followed by aftershocks. North Dobruja local earthquakes become perceptible strong enough

Ancuța Rotaru Habilitation Thesis because of their shallow focuses, although their magnitudes are only just up to 5.5 on the Richter scale. Seismically, Tulcea area is the most affected. An earthquake measuring 4.6 degrees on the Richter scale occurred on September 11, 1980, in Galați – Brăila area; another quake of 5.2 degrees on the Richter scale occurred on November 13, 1981, in Mahmudia – Bestepe zone. The North Dobruja seismic activity has been unimportant since October 3, 2004, when an earthquake of 5.4 degrees on the Richter scale occurred at about 20 km depth in Tulcea – Mahmudia area. An earthquake that reached 5.2 degrees on the Richter scale occurred on May 7, 2008, near the Snake Island (Ukraine) at about 10 km depth (Fig.39); it was not an earthquake detected exclusively in Dobruja, but also in the eastern part of Moldavia and Ukraine. The seismic risk of the region derives from the extremely active Shabla seismic zone (Matova, 1996) (Fig.41). The earthquake focuses are ordinarily between 15 and 30 km beneath the Black Sea while the epicentres locate offshore near Cape Kaliakra. Destructive South Dobruja earthquakes with Mw = 7 have a return period Fig.40. Dobruja’s tectonic fault lines (recurrence interval) of 300-500 years. A destructive earthquake occurred in the 1st century A.D. near Cape Chirakman stroking the ancient town of Bysone and losing it into the sea.

Table 11. North Dobruja earthquakes (in the last 30 years) Date of the earthquake Magnitude Location Depth (km) September 11th, 1980 4.6 Galați – Brăila shallow November 13th, 1981 5.2 Mahmudia - Bestepe shallow October 3rd, 2004 5.4 Tulcea - Mahmudia 20 May 7th, 2008 5.2 The Snake Island 10

Other destructive earthquakes occurred in 543 A.D., around 800 A.D., or in 1444 A.D. (Ranguelov and Gospodinov, 1994). A strong earthquake stroked Dobruja on March 31, 1901, with 7.2 Mw on the Richter scale triggering a large landslide near Balchik Town (Fig.41). Other relevant earthquakes stroked the zone in the modern times of the 20th century: in 1911 (Mw = 4.8) and 1956 (Mw = 5.5). The coastal structures minimize the effects of these earthquakes over a narrow strip of Dobruja territory. A 20 km focal depth earthquake with an epicentre in the Black Sea near Romania-Bulgaria border registered on August 5, 2009 (Table 11). Its epicentre was 95 km far from Constanța City, 135 km northeast from Bourgas City, 61 km east from Varna City, 24 km east from Fig.41. South Dobruja shoreline Kavarna, and 20 km south from Shabla (Fig.41). The beween Shabla and Varna City earthquake recorded a 5.5 Mw on the Richter scale and VII degrees according to the Mercalli intensity scale. Several weak aftershocks followed the shallow earthquake. The earthquake was felt in Bucharest, the capital of Romania (Fig.39) and throughout Bulgaria including Sofia, the capital (Fig.39), located in west Bulgaria.

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Two shallow earthquakes occurred on November 30, 2009, beneath the Black Sea and one on Bulgarian territory. One of the shallow earthquakes occurred at 10 km depth in the Black Sea; its epicentre was located 7 km east of Shabla and 27 km south of Mangalia City, respectively; it hit with a magnitude of 4.4 Mw on the Richter scale and was felt all over the Dobruja region. An earthquake of 4.3 Mw on the Richter scale occurred at 2 km beneath the Black Sea and another one stroked the Bulgarian territory at 35 km depth at the same time (Table 12).

Table 12. South Dobruja earthquakes (in the last century) Date of the earthquake Magnitude Location Depth (km) March 31st, 1901 7.2 near Balchik shallow 1911 4.8 Shabla area shallow 1956 5.5 Shabla area shallow August 5th, 2009 5.5 Black Sea, Romania- Bulgaria border 20 November 30th, 2009 4.4 Black Sea, 7 km east of Shabla 10 November 30th, 2009 4.3 Black Sea 2

Vrancea (Romania) is the second seismic risk zone in Dobruja (Fig.39). Vrancea seismic area produces periodic intermediate earthquakes with Mw = 7, which cause destructive effects marked by fracturing, block subsidence, ground settlement and liquefaction [177] Some of these movements provoked local low-magnitude earthquakes [230]. There is a theory about tsunami effects related to earthquakes as those occurring in the 1st century A.D. and 1901, or to the undated severe earthquakes distributed along the north-eastern Bulgarian coast [231]. Yet, there is not enough evidence to support this hypothesis [316]. Loess deposits of 30-40 m thick formed by rapid deposition preventing proper packing of the soil skeleton lie in the southern part of Dobruja [75]. When an earthquake occurs, these deposits are responsible for soil liquefaction. Silt particles can be as unstable as a slight disturbance of the equilibrium may cause grain rearrangements into more stable positions and decreased porosity of the sediment. During earthquakes, groundwater rises and reaches the loess deposits; on saturation, suctions move away and the soil collapses [142]. The sand strips near South Dobruja lakes and the Palaeogene deposits between Varna City and Balchik Town (Fig.3) are susceptible to liquefaction risk [25], [178]. Using calcium carbonate, iron or aluminium oxides, the cementation technique represents a possible improvement method for these difficult soils [34]. Structural units of Dobruja have the actual cinematic under the Alpino-Carpathian-Pannonic system and Vrancea geodynamic influence and under crust movements from the Black Sea (post-rift phase). In the Romanian seashore of the Black Sea, near Constanţa, a sinking of the terrestrial crust with a velocity of -2.5mm/yr is producing. Towards Mangalia, sinking velocities are around 1 mm/yr [217]. In Dobruja, the terrestrial crust has 38 km depth in the northern part and 30 km in the southern sector. Consequently, shallow earthquakes emerging at up to 40 km depth occur followed by aftershocks. Loess deposits of 30-40 m thick formed by rapid deposition that prevents proper packing of the soil skeleton lay in the southern part of Dobruja. They are responsible for liquefaction when an earthquake occurs. Silt particles can be so unstable that a slight disturbance of the equilibrium may cause grain rearrangement into more stable positions, and the porosity of the sediment decreases. During an earthquake groundwater table rise and reach the loess deposits; on saturation, the suctions are removed, and the soil collapses. Risk of liquefaction has occurred on the sand strips near South Dobruja lakes and Palaeogene deposits between Varna City and Town of Balchik. Calcium carbonate, iron or aluminium oxides cementation are possible techniques for soil improvement. The seismic risk to the South Dobruja Region (located in Bulgaria) resides primarily from Shabla seismic zone. The epicentres located on the Black Sea, near Cape Kaliakra. Earthquakes with M=7 assume an appearance in the period of around 500 years. The 1901 earthquake caused a massive landslide near the town of Balchik. During I century A.C., the ancient borough of Bysone near Cape Chirakman had disrupted and got lost under the sea. There are other considerable earthquakes in the corresponding zone during the XX century – 1911 (Mw=4.8) and 1956 (Mw=5.5). The hypocenters are typically on 15 to 30 km of the depth. The block structure of the coast decreases the effect of these earthquakes to the narrow strip of the territory. The Shabla seismic zone is very active. The second leading factor of seismic risk for South Dobruja is Vrancea seismic area.

Ancuța Rotaru Habilitation Thesis

3. INTERACTION OF SOIL/ROCK CHARACTERISTICS RESPONSIBLE FOR FOUNDATION SOIL/BUILDING DECAY

3.1.DEFORMABILITY ANALYSIS OF ROCK FOR HOMOGENIOUS AND DISCONTINUOUS MULTI-CRACK MASSES The deformation and failure of a rock mass are predominantly dependent on the presence of geological discontinuities such as cracks or faults. To estimate the deformability of rock masses containing cracks, Akira Sato proposed a Homogenized Multitrack Model. In his model, cracks are parallel and infinitely arranged at equal intervals in all directions, and the crack pattern around a fissure is always the same at any part of the model. In the case of high crack density, the mechanical properties of the rock mass, such as compliance or Young’s modulus, are strongly affected by the mechanical interaction between cracks. So, an evaluation of interaction is needed. There are few studies about it, especially in the compressive stress field or mixed mode-loading issue. If all cracks behave the same, the analysis of a region containing one fracture estimates both mechanical properties and fracture process of the model. Discontinuous Deformation Analysis (DDA) is a method used by Zhou Weiyuan from Tsinghua University, Beijing, China, to analyze the motional law for discontinuous, jointed rock masses. This method widely applies in engineering practice, but there are still some limitations in both theory and practical application. Some promising results were obtained and performed a significant role in designing the systems of support stabilization and the sequence of work. Joints, faults and other discontinuities which control the failure and sliding of the masses always dissect rock masses. The discontinuous deformation model provides the most rational way to analyze such geotechnical problems [270]. The frequently used discontinuous numerical methods include Discrete Element Method, Rigid-Block Spring Method, Fast Lagrangian Analysis of Continua, Contact-Spring Model and Discontinuous Deformation Analysis (DDA). The DDA method provides the theoretical basis for a numerical model of rock block systems and a more convenient approach in numerical analyses. This method developed to compute stress, strain, sliding and opening of rock blocks; rigid body movement and deformation arrive simultaneously. Input data consist of block geometry, loading forces, Young modulus E and Poisson ratio n deformability constants and the restraint or boundary conditions of the block system. The output of such analyses includes the movements, deformations, stresses and strains of each block, and the sliding and detachment, or rejoining of blocks. Besides, applying the 2-Dimensional Displacement Discontinuity Method (2D-DDM) introduces a method that estimates the compliance of the model. The distribution of the yielding to the arbitrary loading direction shows complicate shapes when cracking length increases. When the interval of cracks in the usual direction decrease, the compliance shows a complicated distribution. The alternative stacking model deforms more than the latticed model for a given crack length and density. These results indicate that both the mechanical interaction in the crack line direction. The usual course of cracks is crucial to the compliance of the model. These effects also depend on the pattern of the cracks in the model.

3.1.1. Homogenized Multi-Crack Model (HMCM) The Homogenized Multitrack Model proposes to estimate the deformability of a rock mass, which has a high crack density. The 2-dimensional Displacement Discontinuity Method 2D-DDM [64] and linear fracture mechanics estimate the effective compliance of this model. The influence of the mechanical interaction of each crack towards effective compliance is of interest. The deformability of the model in the axial direction is strongly affected by the fissure length, intervals in the axial direction and crack patterns [312]. Fig.42 shows the homogenized multi-crack model [269]. In this model, all cracks are parallel and present anisotropic and linear elastic medium. Each one has a 2a length, a 2w interval on the x-axis direction, a 2h interval on the normal direction towards each crack. All cracks are inclined related to the y-axis. The model has the cracks arranged in a uniform pattern. Consequently, the displacement of each fissure and the stress distribution around each crack are the same. The evaluation of the macroscopic strain field is possible by estimating the displacement distribution of a representative fissure in the elemental region (Fig.43).

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Fig.42. (left) Homogenized multi-crack model; Fig.43. (up) Elemental region; Fig.44. (right) Displacement discontinuity elements on the crack line

0 0 0 (εxx , εyy , γxy ) is given by using effective compliance βxx xx, βxx yy, … , βxy xy.

εx = βxx xx σxx0 + βxx yy x 0 σyy0 + βxx xy τxy0 (1) εy = βyy xx σxx0 + βyy yy y 0 σyy0 + βyy xy τxy0 (2) = βxy xx σxx0 + βxy yy 0 0 0 γxy σyy + βxy xy τxy (3)

3.1.2. Application of 2D-DDM and Homogenization HMCM consists of groups of displacement discontinuity elements. Each element has a length of 2∆ and the uniform shear and normal displacements (Ds, Dn). Each crack with a length of 2a expressed itself by N number of elements (Fig.44) which approximate smooth crack surface displacement. It is necessary to have as many factors as possible on the crack line to obtain accurate crack surface displacement. Let us denote the displacement discontinuity of the j-th element on the i-th crack as (Ds ij, Dn ij). The vector {Di} which consists of displacement discontinuity components of the i-th crack is defined as

Τ {Di } = {D s i1 , D n i1 , D s i2 ,D n i2 , _ ,D s iN ,D n iN } (4)

As stated above, all cracks deform uniformly, and the stress distribution around each crack is the same. The vectors of displacement discontinuities {Di} are equal, and the number of displacement discontinuities becomes 2N. Stress components acting on each element express themselves as the displacement discontinuities. Let us denote the shear stress and axial stress acting on the j-th discontinuity element on the i- th crack as (τsij, σnij). The stress vector, which consists of stress components of the i-th crack, is defined as

Τ {σi} = {τs i1 , σn i1 , τs i2 , σn i2 , _ , τs ij , σn ij , _ , τs iN , σn iN } (5)

The stress vectors {σi} are equal to each other, as the vectors of displacement discontinuities are. 0 0 0 The superposition of two answers offers the solution: (a) the uniform stresses (σxx , σyy , τxy ) act on an

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elastic body without cracks and (b) tensile and shear stresses (σn, τs) act on the inner surface of fissures and the far-field strain is zero. Here, tensions (σn, τs) have to satisfy the boundary condition on the crack 0 0 0 surface by superposition. We indicate the force which corresponds to the uniform stress (σxx , σyy , τxy ) 0 0 on the crack line as (σn , τs ). In the case of the open crack problem, the stress on the crack surface is 0 0 indicated by (-σn , - τs ). Since the far-field strain is zero in the analysis of 2D-DDM, constraint stress (σxx*, σyy*, τxy*), which corresponds to the constraint of the displacement at far-field, is acting in the model. Therefore, in this answer (we declare it an answer (c)) the inner stress and constraint stress are simultaneously operating on the model when 2D-DDM applies. For an accurate solution, it is necessary to eliminate the constraint stress from the answer of (a) + (c). This elimination occurs by loading the constraint stress (- σxx*, - σyy*, - τxy*) acting at the far-field while the force on the crack surface is zero. If we denote this answer as the answer (d), the ultimate solution is obtained by (a)+(c)+(d). In the initial problem, no forces act on the crack surface, and the uniform 0 0 0 stress (σxx , σyy , τxy ) runs at the far-field. In the case of answer (d) no stresses act on the crack surface and constraint stress (-σxx*, - σyy*, - τxy*), which corresponds to the constraint of displacement, is acting at the far-field. Therefore, the difference of the accurate solution and answer (d) represents the magnitude of the stress acting at the far-field. In the following section, the method to estimate the effective compliance from the constraint stress (σxx*, σyy*, τxy*) focuses on the relation stated above.

3.1.3. Estimation of Constraint Stress and of Effective Compilance It is necessary to analyze the stress distribution in the model to estimate the constraint stress from displacement discontinuity analysis. As stated before, the stress distribution is the same around each crack in any part of the model. Therefore, the constraint stress represents the mean value of the stress distribution around the representative crack. As the boundary of elemental regions coincides, it is necessary to determine the stresses acting on it. Imaginary elements get up on the borders of the elemental region (ABCD) with zero displacements, allowing the evaluation of the stress distribution performing on each boundary (AB, BC, CD and DA). The constraint stress components represent the mean values of the stress distribution acting on these boundaries. The model achieves effective compliance by considering the macroscopic strain of HMCM. Equations (1) to (3) identify the correct solution of strain components. Since the macroscopic stress in the answer (c) is zero, the summation of the strain components of (a) and (d) answers represents the correct strain components. The compliance of the alternative stacking model is more comprehensive than of the latticed model for crack lengths and densities. It manifests a similar tendency as Kaneko (1990) and Hirakawa's (1999) [134] numerical analyses. Hence, the crack pattern represents a significant factor in the deformability of the model. The relations between compliance and constraint stress are given by

0 0 0 2 0 0 βxx xx (σxx +σxx*)+βxx yy(σyy +σyy*)+βxx xy(τxy +τxy*)= (1- ν )σxx /E +ν(1+ν)σyy /E) (6)

0 0 0 0 2 0 βyy xx(σxx +σxx*)+βyy yy(σyy +σyy*)+βyy xy(τxy +τxy*)= - ν(1+ν)σxx /E+(1-ν )σyy /E)- (7)

0 0 0 0 βxy xx(σxx +σxx*)+βxy yy(σyy +σyy*)+βxy xy(τxy +τxy*)= 2(1+ν) τxy /E (8)

To gain nine components of compliance, estimation of the constraint stress components is necessary. When displacement discontinuity analysis is applied to the following independent three loadings: first 0 0 0 0 0 0 0 loading (σxx = σ, σyy = 0, τxy = 0), second loading (σxx = 0, syy = σ, τxy = 0) and third loading (σxx 0 0 = 0, σyy = 0, τxy = σ), the components of the constraint stress for each loading are acquired. The components of the constraint stress are considered the mean values of the stress distribution. The elements of the constraint stress for the three loading parameters support equation (6), βxx xx, βxx yy and βxx xy estimation. The constraint stress for the three loading constants, and equations (7) and (8), respectively estimate the other components of the compliance. The displacement discontinuity analysis applies to this model. The uniaxial stress loads from an arbitrary direction and the compliance of the model is estimated.

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3.1.4. Theoretical Background of the Failure Simulation of Rock Masses by Discountinuous Deformation Analysis (DDA) The displacement u of v any point x, y of a block can be represented by six displacement variables (uo, vo, ro, εx, εy, γxy). For a system of N blocks, with the total potential energy as π, minimizing the total potential energy derives the equilibrium equations.

∂Π / ∂ dri = 0 r = 1, ... ,6 (9) where: dri denotes the displacement component of the i-th block.

After minimization of potential energy π, i Fri = - ∂ Π (0) / ∂dri , r = 1, ... ,6 (10) 2 [κij] = ∂ Π /∂dri dsj, r = 1, ... ,6 (11)

According to DDA, the slope is in an original stable state under the given mechanical parameters. From the initial stable state of the slope, diminishing geomechanical parameters pursues a DDA computation process, so that the slope becomes collapsed. By diminishing values of the strength in rock and joints, the rock in the slope will start cracking in blocks and will progressively mobilize. DDA is a promising numerical computing method, but the DDA method still needs more improvements to fulfil more engineering requirements, especially in three-dimensional problems and its numerical computation method.

3.2. MECHANICAL BEVAHIOUR OF AN UNSATURATED SOIL ASSOCIATED WITH SEEPAGE Frequently, residual soils formed under unsaturated conditions because of volatile fluids with different absorption coefficients found at the interface between the skeleton and fluid. That leads to the requirement of controlling the stress increment derived from suction potentials by performing constant shear tests to water, leachate and gasoline infiltrations. As follows, the saturation with fluids having different specific weights and viscosities than water may occur in the unsaturated gaseous zone. The adsorption is according to their physical and chemical properties (volatility, solubility, adsorption coefficient) and the time past after contamination. Analysing these phenomena is of particular interest to evaluate the mechanical constants and changes in shear strength [12]. Even though classical Soil Mechanics developed predominantly from studies in saturated soils, the soil above the water table keeps unsaturated in some temperate zones. Water captured above the water table is in a reduced pressure state (below atmospheric pressure) called groundwater suction or matric suction. Suction means the force whereby the soil holds water. It can vary up to thousands of kPa. When it refers to air pressure in the voids, the matric suction sometimes contributes to slope stability in residual soils. Modern concepts for unsaturated soils developed based on practical results acquired on modified shear tests of residual soils [361]. The definition of the shear stress versus matric suction envelope explains the mechanical behaviour of the soil generating the suction effect [223]. Several authors propose an extension to the Mohr-Coulomb envelope theory through three-dimensional evaluation (shear stress: confinement stress: matric suction - t: s´30: s), defining the boundary between possible and impossible states by a flat or curved surface. For all suction values, the friction angle is constant and equal to its value under complete saturation. The relation between the matric suction (s = ua - uw) and the shear stress (t) assumed linearity, but its nonlinearity was confirmed later [105]. Angle ɸb indicates the ratio of the increment of t in translational terms relative to the suction (ua - uw)f. When the partially saturated soil gets moist to an ideal saturation condition, a minor transformation concerning its strength comes up in the shear stress equation. The relation changes in respect to translation and rotation of effective cohesion, and it relates to the cohesion as follows [224]:

b c = c´ + (ua - uw)f tg ɸ (1)

Ancuța Rotaru Habilitation Thesis where: c - the intersection of the Mohr-Coulomb failure envelope in the plane defined by the matric suction and the axis of the shear stress; c´- the effective cohesion read off for an extended Mohr-Coulomb model, achieved at the cross point of the envelope and axis, where not only the normal stress but also the suction stress at failure is equal to zero; (ua - uw)f - matric suction in the failure plane; ɸb - angle indicating the ratio of the increment of  in translational terms relative to the suction (ua - uw)f.

Various combinations of s, ua and uw are in usage. However, (s-ua) and (ua-uw) are currently generally recognized. Under normal in situ conditions, ua = pa, where (s - ua) is the net normal stress and (ua - uw) the matric suction. Here, ua and uw are the air pressure and the pore water pressure, respectively meaning that the water pressure is negative (-uw). In most cases, it is more convenient to work in terms of the mean stress (p) and shear stress (q) invariants in the triaxial space [188]. Provided an invariant coordinate system sets out the shear strength parameters (assuming the sum of principal stresses), either the shear stress vs the average stress or deviator stress (q) vs the octahedral stress (p´), the following equation expresses the critical state [85]:

q = M(s) + (s) (2)

The infiltration of water in the soil causes a decrease in suction forces of the soil matric up to instability, assuming the importance of this variable in the evaluation of slope stability. Generally, both normal stress and shear stress keep constant in the process of slope infiltration, yet initially, the failure goes with a decrease in suction stress by increasing soil saturation [186]. The experimental evaluation of this subject is carried out by conducting conventional triaxial tests, modified to allow the translation of the shear plane or stress plane. The tests use this technique, that is, with the imposed and controlled suction (s = 40 kPa), performing the shear tests with the constant minimum principal stress (σ3) and carried out in remoulded specimens. The sections were developed in two ways: i) keeping the water content constant throughout the test and ii) drying the specimen followed by infiltration by a few different fluids and for imposed deformation. Environmental geotechnics also studies the infiltration and contamination of soil masses by pipe and sediment failure, to which are associated with the effects of volatility and suction tensions that develop in the pores. A light approach or comparative interpretation is only made in cases of soil infiltration by gasoline and leachate in a given deformation state.

3.2.1. Materials and metods Tests run away with the residual granite soil of Covilhã. During sampling, the in situ degrees of saturation ranged from 50 to 65% and in the natural state it tended to form aggregates frequently larger than 20 mm in diameter. Corresponding to this degree of saturation, the interstitial or matrix suction, a function of the water-soil characteristic curve is approximately 40 kPa [63]. The residual granitic soil is non-plastic silty sand in its natural state, and it is classified in the SW-SM in a similar group with the rubble [17]. The soils were unstructured and reshaped in terms of compactness, void ratio and degree of saturation. The group A-nc (series I) appears in the area of the dry compaction curve for an effort (energy E2) of 112 kJ/m3. The samples are separated giving their compactness and initial degree of saturation: series I (A-nc: n = 0.550 to 0.630; Si = 52% to 68%). The groups of tests, defined in this way, are presented in Fig.45.a and Fig.45.b. Tests run away with the residual granite soil of Covilhã. During sampling, The water content represents the amount of water independent of void ratio, yet the residual saturation degree arises as a fundamental parameter that depends on the void ratio. In unsaturated soils, the soil fabric is of greater importance than in saturated soils. The compacted soil on the dry branch of the compaction curve or at optimum water content can generate aggregates. On the moist side of the compaction curve, this aggregation virtually does not exist. Porosity inside aggregates may not vary, but the void ratio of the sample as a whole may vary considerably, depending on the degree of aggregation and the size of the inter-aggregate voids. That becomes important for the interpretation of the mechanical behaviour of the soil.

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a) b) Fig.45 (a, b) Residual granite soil of Covilhã: a) relative position of remoulded samples (A-nc) in 3 3 function of compaction curves defined by the compactive efforts E1=593 kJ/m and E2=112 kJ/m ; b) spatial distribution e:S for a group of samples

3.2.2. Testing Programme and Proceedings The series of Consolidated Undrained triaxial tests (CU tests) performed on saturated and unsaturated soil samples to establish a reference state to interpret seepage tests. Conducting direct shear tests with constant water content in undrained conditions is like studying the critical scenario of pore water pressure during structure collapse. Samples consolidate at s´30 = 50, 100, 200 and 400 kPa and shear test fulfils in an undrained manner keeping s30 constant. Samples series I have residual suction from sr = 15 to 40 kPa. Tests carried out for s = 40 kPa, a typical in-situ value in these types of soils as Sr = 55 to 60%. Initially, procedures equalised the sample pressure decrease at 40 kPa with water entering or leaving the specimen. As for shear tests with constant water content and imposed suction, the sample reaches the suction of 40 kPa. That is, water inlet or outlet (O´X´) consolidated until the pressure equalisation (X´Y´) and sheared off in an undrained manner with constant s30 (Y´Z´). The final suction (sf) differs as it is a volumetric dependent parameter. Table 13 presents physical indexes of samples establishing the stress plane at residual suction, s = 40kPa.

Table 13. Physical characteristics of Consolidated Undrained series of samples with constant water content tested in triaxial at different stages, group A-nc (SERIES I)

Initial Condition Consolidation Residual (Ultimate) Shear Stress Phase

A ´30 d Sr e0 efc sfc ef Sf sf Serie (I) (kPa) (kN/m3) (%) (kPa) (%) (kPa) CU 50 16.4 57.1 0.599 0.528 39.6 0.517 76.7 33.6 CU 50 16.3 66.7 0.608 0,554 39.9 0.544 68.6 32.7 CU 100 16.5 67.0 0.553 0,510 39.7 0.480 68.9 15.3 CU 200 16.3 62.5 0.614 0,479 39.7 0.430 84.3 -3.1

Tests conducted in partial saturation conditions establish three stages [108]: 1) Suction consisting in percolating water through the inner sample, opening the water channel at the base of the sample and getting a reduced hydraulic load (10 kPa) with a decrease of pressure at its top [210]. 2) “Consolidation”

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/compression and pressure equalisation inside the specimen. That is, application of the average stress {p´ = [(s1 + 2s3) / 3-ua]} with s1 = s30 in different samples waiting for equalisation of pressures at the top and bottom [stop = sbase = (ua-uw) = 40 kPa]; and 3) Shear off the constant moisture content in the s = 40 kPa plane with 0.04 mm/min speed reaching the 25% axial deformation of the specimen (Y´Z´) [290]. The leakage effect reveals the soil shear strength at failure due to water, leachate or gasoline infiltration, at significant stresses. The programme included soils after drying, and the stress paths followed during the equalisation process are the same as in the shear tests with initial suction of 40 kPa (Fig.46). The specimen follows the established path and action mode at point X', i.e. the imposition of suction (O´) followed by the required compression stage (σ´3 = 100 kPa) and pressure equalisation (Y´). Upon reaching Y´, the shearing process starts with constant suction to specific axial stress, when the shear test breaks for the time required to infiltrate the fluid. As soon as the specimen is saturated, the compression stage continues in a drained way to Z´´. Fig.46 shows various stress paths in the {q:p´:s} space for triaxial tests carried out on residual granitic soil with small to moderate compactness [104].

Matrix suction, s (kPa) Z

Z , q q (kPa),

stress X

Y Deviator

Mean effective stress, p (kPa)

Fig.46. Prediction of the stress paths for triaxial tests on samples of residual granitic soil [224]

Table 14. Physical indexes in different phases of modified triaxial tests with leakage, in stage I corresponding to drained test with constant suction and stage II corresponding to the shearing stage after leakage Initial Residual Condi- Stage Stage Reference tion

´30 d Sr e0 ef Sf sf (kPa) (kN/m3) (%) (%) (kPa) A cid100-s40i-nc-A2 100 16.0 43.4 0.642 0.495 56.2 18.9 B Infiltration - Water 60 18.3 56.2 0.495 0.499 83.85 -4.1 A cid100-s40i-nc-LA1 100 16.0 62.8 0.642 0.538 74.9 38.1 B Infiltration - Leachate 60 17.1 74.9 0.538 0.496 78.5 -2.5 A cid100-s40i-nc-GA1 100 16.0 62.8 0.642 0.641 71.1 38.5 B Infiltration - Gasoline 60 16.8 71.1 0.561 0.564 73.65 6.4 CID cid100-s40-A1(s=40kPa) 100 16.1 52.5 0.631 0.534 69.35 39

Percolating the sample one and a half times its volume ensured 70 to 75% saturation and generated a suction of 10 kPa. At this time, the effective compressive stress changes by increasing the water pressure in the pores. The suction decreases and the shearing process continues in a drained manner, and the

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards horizontal force must decrease. The water input ratio must be low and depends on the permeability (k = 10-5 m/s, for this type of samples). The specimens used in the leakage test were remoulded with the similar physical characteristics as the specimens used in series I. Table 14 presents the stress typology and physical indexes of stage A, corresponding to the drained sample with constant suction and stage B, corresponding to the shearing stage after leakage. The wetting test with the water changed its density from stage A to B and presented the highest degree of saturation at the end. Infiltrations with leachate and gasoline show more subtle changes in density and saturation increase. Thus, a significant reduction in suction reflected in the shear strength occurs when infiltrating water.

3.2.3. Stress paths in critical state The true critical point (critical state) will be unreached in unsaturated tests as all samples continue to expand even over large extensions (ea > 25%). However, the critical state paths plot assuming the closest value to the critical state. Fig.47 shows the paths defined in the space of deviatoric stresses vs mean stress (q: p´) for the failure criterion [(s1´/s3´)ult] of the series I of samples, unsaturated [s = (ua - uw) = 40 kPa] and the corresponding samples tested in the same way, but saturated [s = (ua - uw) = 0 kPa]. The gradient is essentially similar [M(s) = M]. This real similarity becomes increasingly evident when reported to the failure criterion (s1´-s3´)ult, with the respective results of tests on saturated samples having the same initial physical characteristics. This may suggest that the effective friction angle (´) in the q:p´ plane is constant and independent with the s = 0 kPa or s = 40 kPa plane, which means the independence of ´ with the applied suction. The plans assume 100% degree of saturation. That is b = ´ for the first interpolation. For the second interpolation, b < ´ assumes and associates with the residual degree of saturation for suction of 40 kPa. The geometry is planar although it is an approximation, as it would require shearing tests in different imposed suction planes. Table 15 presents the equations describing the failure planes for the failure criteria (1´-3´)ult in the {q: p: s} space.

1600

1400

1200 q =0.20075u - 9.520p 1600 q =0.20075u - 1.409p ...... 1400 1000

800 1200 Group (serie I) A-nc s= 40 kPa 1000 600

800 400

s=u -u (kPa)

600 200 a w Deviator stress, q (kPa) stress, q Deviator 400 0 0 200 400 600 800 1000 Group 200 A-nc s= 0 kPa 0 0 200 400 600 800 1000 Mean effective stress, p´(kPa)

Fig.47. Critical state liness of residual granitic soil: representation in the {q: p´: s} space of the stress paths followed in the planes s = 0 kPa and s = 40 kPa and the respective failure plans for the series I

The values of M(s) decrease and their variation is smaller between planes, which supposes a greater independence of  from the imposed suction (series I: s = 40kPa = 36 to 39º s = 0kPa = 35 to 39º), in contrast to cohesion (c) (series I: cs = 40kPa = 2.3 to 2.6 and cs = 0kPa = 0). The value of b is between

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3.4º and 3.8º. This interval is small because it is close to the intrinsic behaviour and increasingly dependent only on the friction effect and the suction in the sample.

Table 15. Equations of failure planes for the failure criterion [(1´-3´)ult] in the {q: p: s} space Failure Criterion

Suction [(1´-3´)ult] Serie (kPa) Mean Plan Shear Parameters Failure Envelope c´ [kPa] ´ [º] b [º] I 0 0 35 40 q=0,20075u-5,4645p 2.6 36 3.8 40 2.3 39

3.2.4. Shear behavior with leakage effect The total shear stress with σ´30 and constant suction (σ´30 = 100 kPa and s = 40 kPa) and the curve in the space can provide an estimation of the maximum shear stress at the beginning of the leakage. In tests affected by leakage, the shearing stage developed with constant suction (s = 40 kPa) except this occurs until 3 to 4% of axial compression increase is reached, followed by leakage. The development of axial stress relates to the time the abrupt discontinuity starts in stiffness evolution (E), marking the first yield, for the dry shear test without leakage. Fig.48 shows the discontinuity of the tangent deformability modulus for 3 to 4% axial deformation. When the test stops, the creep effect must dissociate to proceed with the leakage. That relates to the change in the volumetric stress before infiltration begins, checked by the deformation of the soil specimen under constant shear and suction stresses [304]. The creep effect is negligible in this type of soil concerning maintaining or correcting the vertical tension when leakage acts [305]. The absence of the creep at this stage ensures the material does not yield during leakage. The water pressure variations in pores cause displacement during the leakage. In the first stage of tests considering infiltration, the stress level fixes at the first yield (εa = 3 to 4%), and the shear stress reduces by decreasing the suction during the infiltration process. The strength reduction is gradual, starting at the base and moving towards the top while water flowed into the soil. The yield strength gradually decreases, and a larger shear surface sets in tests without leakage. That is in line with the need to increase the axial stress up to failure. Samples with water infiltration and leachate have shrinkage behaviour, and the volumetric growth relates to the soil skeleton failure. However, the magnitude of volumetric increase associated with the failure process is less than the one induced by tests with constant moisture content. That relates to the wetting process (or suction reduction) carried out at a high-stress ratio or the level of acquired axial stress increase, suppressing the negative dilation.

Fig.48. Variation of the stiffness module for drained tests with constant suction and sheared off to σ3´ = 100 kPa

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The sample infiltrated with gasoline displays a virtually dilating behaviour due to the gradual corrosion of the membrane. Although it is challenging to maintain the membrane effect separated from the physical one inherent in the evolution of the air-fluid-solid skeleton system (coagulation of fines, particle bonds, gasoline volatility and lubrication), this infiltration certainly provides the highest shear stress for small axial stresses. In the representation of the space defined by the planes {q: p: s} (Fig.49), the stress paths of infiltration tests follow the pathway defined by the imposition of suction, compression and pressure equalisation of the specimen, drained shear test with σ´30 = 100 kPa, seepage, and final shear under similar conditions but with the average shear stress altered by the decreased suction. Tests proceeded as the drained shear tests with σ´30 = 50 to 55 kPa. The maximum shear stress showed a loss in all samples tested after the leakage by various fluids compared to compression shear tests σ´30 = 50 kPa. The stress paths follow the break envelope defined in the stress plane for s = 0kPa without touching it.

300

qmax = 1.676p 300 R2 = 0,9972 qult = 1.4485p 250 (s=0 kPa) R2 = 0,9972 (s=0 kPa)

250 gasoline 200 leachate 200 w ater Group (serie I) 150 s= 40 kPa

150 100 Group (serie I)

s=0 kPa Deviator stress, q (kPa) stress, q Deviator 100 cid10 0-s40i-nc-LA1 50 1:3 cid100-s40i-nc-GA1

50 cid10 0-s40i-nc-A2 0 0 50 100 150 200 250 300 0 0 50 100 150 200 250 300 Mean effective stress, p´(kPa)

Fig.49. Stress paths for shear tests with initial ´30 = 100 kPa and leachate water/gasoline infiltration

Table 16 reports the values of shear stress vs mean stress at failure for different criteria, for samples with infiltration of diverse fluids and samples with constant suction without infiltration.

Table 16. Shear test for σ´30 = 100 kPa, with dry samples followed by infiltration (water or leachate or gasoline) in soil type A-nc: stress values for different failure criteria Infiltration Without infiltration Fluid Water Leachate Gasoline 3 (kPa) 60 60 60 60 sinitial (kPa) 40 40 40 40 plast (kPa) 1.5 2.5 -6.4 40 p´(kPa)  128.4 126.0 148.6 200.1 q (kPa) 1´/3´)max 206.1 213.56 245.7 279.3 a (%) 11.8 14.0 13.5 15.1 p´(kPa) 127.9 126.1 150.9 202.9 q (kPa) 1´-3´)max 206.5 213.8 249.76 278.4 a (%) 13.3 13.6 13.0 14.4 p´(kPa)  124.6 123.2 148.4 194.8 q (kPa) 1´-3´)ult 191.1 198.6 239.6 254.2 a (%) 25.4 24.9 25.2 25.1

Ancuța Rotaru Habilitation Thesis

Following different criteria, the soil strength after leakage is lower than those without infiltration or wetting. The average difference of shear stress of samples infiltrated with water and leachate is approximately 70 kPa. This difference is smaller when compared to the infiltration of petrol. The axial stress required at failure is generally lower when the infiltration occurs. During the shearing stage and after infiltration the suction however exists. The failure occurs under conditions of negative pore water pressure, and the soil strength decreases precisely how much the suction decreases. In tests with infiltration, the failure area is more substantial than in tests with constant suction or saturated.

The convergence of yield lines at high stresses means that M (from the expression q = Mp´ + d) tends to be constant. So,  depends only on frictional characteristics of the soil, admitting ´(s = 40 kPa) = 37º and ´(s = 0 kPa) = 36º and the cohesion grows because of the small variation of b. The value of b is practically constant (b = 3,5º). That is not so evident as it depends on Sr and fabric. That fact makes it impossible to develop a unique plan for the limit state in the {q: p: s} space. The soil shear strength for p´0 = 100 kPa, after infiltration or wetting with water or leachate, decreases with approximately 70 kPa. This difference is minor in case of infiltration with petrol. In the first stage of the shear test at constant moisture content, particles and aggregates act individually. Yet, with the reduction of suction by leakage, the aggregate structure becomes unstable, and the collapse guarantees the decrease of strength and volume. In tests with infiltration, the soil collapse at a lower saturation than 100%, and the suction decreases with the increase of the effective mean stress. This fact is equally evident for tests at constant water content by increasing the volumetric compression. The magnitude of the volumetric stress at collapse during wetting is less than that induced by shear stress at a constant water content. That is because of the infiltration process at significant stresses already installed, which suppressed some contraction. Displacement during leakage stage is due to pore water pressure changes. Even so, this is a failure criterion for slopes subjected to infiltration. The failure occurs when the displacement ratio increases rapidly. The suction measured at this point still exists and should be unoverlooked. In other words, this means the slope may fail in an unsaturated condition. There is a negative water pressure in the pores. In the first shear stage, the imposed suction is high, but the aggregates act as individual particles. The soil typical behaves as granular justifying the actual grain-size distribution of the soil. When the suction reduces at leakage, the aggregate structure becomes unstable generating a decrease in strength and volume due to structure collapse. Put differently, steep slopes may be less vulnerable than gentle slopes.

3.3. STABILITY COEFFICIENTS VS STABILITY EVALUATION USING FINITE ELEMENT-NEURAL NETWORK HYBRID ALGORITHMS FOR SLOPE ANALYSIS The application of the effective stress analysis to earth slopes has suffered through lack of a general solution such as that presented by Taylor (1937) for the total stress analysis. Developments in computing technologies have been applied to the slip circle method and have made it possible to present the results of the effective stress analysis in terms of stability coefficients from which the factor of safety can be rapidly obtained. Recent developments based on structural tests of soil specimens have applied a neural network (NN) soil model incorporated into the finite element method (FEM). The stability of an excavated soil slope evaluates the finite element-neural network (FE-NN) hybrid algorithm [268]. The practising engineer frequently requires a rapid means of estimating the factor of safety of a cutting, an embankment, or a natural slope. A detailed analysis was often impracticable in the preliminary stage when several alternative schemes are under consideration. Current methods of stability analysis used for the long-term stability of slopes and most earth-dam problems include the observed or predicted pore-pressure distribution as a significant factor in the calculation. These problems call for a general solution but expressed in terms of effective stress rather than of total stress. Relevant recent interest in neural networks (NNs) within soil mechanics and geotechnics is the question of its coupling with other numerical methods. In the majority of reported cases, the application of NNs leads to a stand-alone system. In some cases, to establish precisely how these new tools fit together with the existing tools (numerical methods) is difficult. The key to maximizing the benefits of this new NN technology is in its integration into our existing tools, for example, FEM, thereby endowing the later with increased capability. This paper targets this issue specifically, evaluating stability for an excavated

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards soil slope employing FE- NN hybrid model, and the numerical results are quite good. The training data for the new NN computation containing the knowledge of the nonlinear mapping must include a sufficient number of stress paths, acquired by the network. The paper presents both methods: the classical one, using the stability coefficients with the distribution of pore pressure encountered in typical earth dams and cuts, and the use of neural networks, a new technology for earth slopes analysis.

3.3.1. Constitutive modelling By the factor of safety, the shear strength parameters related to effective stress c´ and tan Φ´ decrease before the slope reaches the limiting equilibrium. For manageable slopes securing a homogeneous distribution of pore pressure, the circular arc method provides the factor of safety to an adequate accuracy for all practical proposes. Taylor presented his results in terms of the value of stability number c/F·γ·H required for a given value of friction angle Φ to maintain the equilibrium. That enabled the general solution to appear in a compact form. It also means that a step-by-step numerical method had to evaluate the factor of safety of any actual slope, which is not in limiting equilibrium. In Taylor’s solution, the stability coefficients lead directly to the factor of safety. This presentation occupies rather more space but permits obtaining results by simple interpolations in a particular case. Taylor’s solution works for effective stress with no pore pressures. The neural networks (NNs) within soil mechanics and geotechnics is of interest by coupling it with other numerical methods. In the majority of reported cases, the application of NNs leads to a stand- alone system. In some cases, it is challenging to establish how modern tools fit together with the existing tools (numerical methods). The key to maximizing the benefits of this new NN technology is in its integration into our existing tools, for example, FEM, thereby endowing the later with increased capability. This paper explicitly targets this issue, evaluating the stability for an excavated slope employing FE-NN hybrid model. Numerical results are reasonably promising. Modelling represents a fundamental method in research of engineering problems. Modelling of the observed phenomena, like the constitutive behaviour of the material, enables the understanding of phenomena and makes most engineering analysis possible. NNs (Fig.50) offer an innovative and unique method of approaching the constitutive modelling. Initially, the investigation of material behaviour in the experimental data helps to identify the dominant features of material behaviour. Once the material behaviour is explained and its particular features identified, a mathematical model develops to simulate this behaviour. The artificial neurons in the input layer may represent the state of stresses, the nature of strains and the stress increments. The units in the output layer may represent the strain increments. In constitutive modelling, NNs learning capabilities capture the constitutive behaviour from structural tests (Fig.51). The connection strength of a self-organizing feed-forward NN encodes them. The training specifies the activation values of both input and output layers and the learning rules applied to modify the strengths of connections. After training the NN with sufficient test data along different stress paths, it will produce the correct strain for any set of stress increments, at any state of stress.

Fig.50. A three-layer NN Fig.51. Incorporation of a NN constitutive model for soil constitutive model within the FE

The experimental constitutive modelling model provides the mapping from stress increments to strain increments (stress-controlled model). However, in computational mechanics and finite element

Ancuța Rotaru Habilitation Thesis analysis, the inverse mapping from the strain increments to the stress increments (strain controlled model) is needed [64]. One of the essential features of the NN computational models is that the inverse mapping develops as smoothly as the direct mapping. The training data for the new NN calculation containing the knowledge of the nonlinear mapping must include a sufficient number of stress paths got by the network. A data set, which incorporates the relevant information, calls a comprehensive data set. NN trained with a complete data set on the constitutive behaviour will respond appropriately on stress paths even if they do not appear in the training data set.

3.3.2. Incorporation of a NN Constitutive Model within the FE Fig.2 shows the concept of incorporation of a NN constitutive model within the FE. The purpose of the NN constitutive model within the FE is to use boundary forces and displacements to train a soil model replacing the role of conventional constitutive laws. The FE-NN hybrid approach allows the training of the NN soil model in a FE analysis of the structural test (Fig.52). The FE-NN hybrid algorithm applies on one set of boundary conditions, iteratively modifying connection weights of the NN model, so FE results match the second set of boundary conditions. The algorithm steps in which force boundary conditions apply and displacement boundary conditions enforce through training the NN material model are

Pn = Pn-1 + ∆Pn (1)

j-k j j-1 Kt =δUn = pn – In-1 – δIn-1 (2) n = load increment number ; j = iteration number

j j δεn =BδUn (3) j j-1 j ∆Un = ∆Un + δUn (4)

j j-1 ∆εn = ∆ εn + δεn j (5) j j-1 ∆σn = ∆σn + δσn j (6) and go to the first step and apply the next load increment. Otherwise, continue. The boundary displacement errors apply as displacement boundary conditions. The strain increments δ∆εnj compute at the integration points, and they are propagated through the NN soil model to determine the corresponding stress increments δ∆σnj. These stress increments represent the errors at the output of the NN soil models, corresponding to the errors at the measured Fig.52. Training of the NN soil Fig.53. FE-NN hybrid boundary displacements. The model within the FE model for soil error at the output of the NNs, δ∆σnj, is back-propagated through the NN soil model and the connection weights are modified. These steps repeat themselves until the NN soil model determines the material behaviour. With the trained NN, the FE analysis will be able to produce the correct measured boundary displacements, when subjected to the measured boundary forces.

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards

3.3.3. The FE-NN Hybrid Model for Soil Fig.54 shows the analytical model of a 10m high-excavated soil slope. Movement on the vertical boundaries is restricted horizontally solely, while both horizontal and vertical directions constrain the move on the bottom line [132]. The analysis employs a mesh consisting of 250 nodes and 216 rectangular elements. The deformed geometries of the soil slope, after excavation, are presented with continuous lines in Fig.55. The ground surface behind the crest settles approximately 0.88m (in situ measurement 0.88m; limit analysis 0.94m) and the bulging extends 0.16m (site measurement 0.15m; limit analysis 0.21m) from the incipiently vertical slope line. For the FE- NN hybrid model (Fig.53), the loss of ground evaluated by the largest Fig.54. The analytical Fig.55. Slope geometry horizontal displacement along the model of an excavated slope after excavation vertical slope line occurs at the nodal point above the toe. Conclusively, the results of the FE-NN hybrid model are valid. 1. After the excavation of the soil slope, the ground surface behind the crest settles approximately 0.88m, and the bulging extends 0.16m from the incipiently vertical slope line. The results are in agreement with the site material. 2. The FE-NN hybrid model for soil has a nonlinear stress-strain relation, and the asymptote of the relation curve represents the horizontal straight line of the rigid-plastic model. 3. The FE-NN hybrid model generalizes the NN giving the correct strain increments for any set of stress increments at any stress paths not included in the training data set.

3.4. GROUNDWATER RESOURCES MANAGEMENT The study deals with the optimal management of groundwater in aquifer systems. The objective of groundwater management, with only a moderate availability of surface water, is to evolve appropriate operational strategies controlling the aquifer quality. The water resources represent strategic, vital resources considering interstate importance. Romania possesses a significant supply of underground and ground waters, the essential Fig.56. A typical groundwater discharge stocks of which are in the rivers and snow massifs. There is a remarkable number of lakes and other natural reservoirs in the country, a relevant per cent locating in high regions of tectonic origin. The reason for taking away waters consists of unsatisfactory technical conditions of irrigation and water distribution systems, equipment, imperfect methods for watering and absence of water-saving technologies.

3.4.1. Groundwater quality treatment Most groundwater originates from rainfall that entered the earth. The drawing shows a typical situation with water-saturated soils (overburden aquifer) over a bedrock aquifer. In the overburden aquifer, water fills the void space between soil grains. Bedrock aquifers underlie the surface soils (overburden) and

Ancuța Rotaru Habilitation Thesis overburden aquifers. In the bedrock aquifers, water occurs in fractures and other voids in the bedrock. Some types of bedrock like sandstone may equally have additional voids (intergranular voids) saturated with groundwater [136]. As in the case of surface water, groundwater flows from higher elevations (or pressures) toward lower elevations (or lower pressures). Groundwater flow is typically toward a groundwater discharge area as Fig.56 shows. The stream in the drawing represents a typical groundwater discharge area. Groundwater pressure, rather than elevation, controls the rate and direction of flow in confined (or artesian) aquifers. Those aquifers divide under impervious or poorly previous strata (aqicludes and aquitards). Every year, a significant quantity of various drains draws out from surface water objects, and high amounts of wastewaters stand biological, physicochemical or mechanical clearing. Every year, dangerously polluted wastewaters hold without clearing in open water reservoir and channels. The content of toxic substances surpasses the established bacteriological and physicochemical norms. An appearance of organic pollution, petroleum, phenols and other hazardous substances in water objects connect to an inefficient clearing. It is a case of urban drains, drains of the enterprises of meat, food and local industry, leather-processing and agricultural manufacture, motor transportation enterprises. Besides, a relevant per cent of various complexes of clearing structures is in an unsatisfactory technical condition and does not provide effective clearing of waste. All these jointly represent a potential ecological danger for the surface and underground water in the future. River waters abide by pollution. Increased content of ammonium and nitrate nitrogen, compounds of zinc, petroleum, an organic and other dangerous substances appear here. Underground sources supply an amount of drinking water (for household needs) and a large part of water for industrial needs. A threat to the quality of underground water goes on pollution of the uppermost part of water-bearing layers. Reasons for underground water pollution are:  location of objects of stock-breeding in zones of sanitary water protection, development of irrigated agriculture, unfavourable sterile condition of populated regions, absence of water supply systems and drains;  location of heaps, and tail storages of waste from mines in intermountain troughs and hollows, flood plains of rivers, radioactive substances, salts of heavy metals, cyanogen-contained substances. Examples of pollution of underground waters:  increase of concentration of nitrates up to depths of 150 m in the region where water supply ensure the drinking water;  pollution by nitrates and manganese because of the outflow in the last of polluted industrial drains from tail storages of mining plants;  increase of mineralization and concentration of chlorates and sulphates in regions of gold extracting. Pollution by nitrates, petroleum, and toxic chemical substances are equally marked. In this way, an increase of polluting substances in the environment, unsatisfactory storage, processing, usage of industrial and household wastes [226], low culture of agricultural manufacture have resulted in local pollution of open water reservoirs and underground waters. Subsurface exploration confirms what exists below the surface of the earth. Fig. 57 shows a test drilling that is a type of subsurface exploration. Drilling, samples come to the surface. After completing the drilling, the reconstruction of the subsurface is possible. The borings turn into wells by installing pipes with slots or holes, or a screen section to allow water to enter. The measured water depth and Fig.57. Test chilling (subsurface exploration) collected groundwater samples support investigation on flow direction, water composition and contaminants [251]; [301].

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards

Other methods explore the subterranean realm. They include excavation and mining, cavern entry and exploration, and indirect approaches that may involve geophysical technique.

3.4.2. Groundwater monitoring and flow modelling Groundwater monitoring performs in situations with varying objectives. It involves measuring the physical and chemical properties of groundwater periodically [294]. Monitoring the concentrations of contaminants controls if they are increasing, decreasing or staying in the same range. Monitoring also performs in the vicinity of water supply sources to prepare the quality of water and trends of indicators of quality. Groundwater monitoring programs involve an array of monitoring or observation wells [298]. Fig.58 indicates a shallow overburden aquifer monitoring a well and some of its basic features. A well of this type makes possible the measurement of the groundwater elevation and allows water sampling to test the composition of the groundwater. Groundwater flow Fig.58. A shallow overburden aquifer modelling uses to define the quantity of groundwater monitoring well and its basic features available or direction of dissolved contaminant migration. It establishes the limits of a capture zone for a contamination recovery well or for delineating a water well protection area or recharge area for a water supply [382]. Scientists frequently use classical mathematical formulas to estimate the effect on the groundwater surface. To shape the long-term yield, and water level draw-down of a water-supply well, classical formulas use for preparing projections [232]. Modelling by manual calculations (analytical modelling) is time-consuming and, therefore, expensive. Scientists prepared computer groundwater modelling for the efficient assessment of Fig.59. Computer groundwater modeling groundwater flow under the addition of simulated wells and recharge sources in an existing flow field. Models often generate contour maps to illustrate relevant data related to groundwater flow (Fig.59). The computer output usually presents groundwater elevation (artesian pressure) maps for further studies.

3.4.3. Groundwater quality and remediation Groundwater quality reflects the substances dissolved or suspended in the water. Suspended material is not transported far in most subsurface materials, but it is usually filtered out. In general, groundwater flow is so slow and depends on the permeability (water transmitting ability) of the subsurface materials, as well as the hydraulic gradient (slope of the water- table or pressure gradient for artesian conditions). The rate of groundwater flow usually measures in meters/day or meters/year. In some situations, where Fig.60. Water supply well the flow is slow-moving, it measures in centimetres/year. Groundwater contains higher

Ancuța Rotaru Habilitation Thesis concentrations of natural dissolved materials than the surface water. Materials dissolved in the water reflect the composition and solubility of earth materials (soil or rock) the groundwater is in contact with and the time they have been in the subsurface. A number of artificial activities pose threats to water quality. They include landfill solid waste disposal, liquid waste disposal basins, septic waste infiltration systems, highway deicing with chemicals, gasoline service stations, petroleum bulk storage facilities, industrial activities, underground storage tanks, livestock feedlots as well as urban stormwater infiltration. A source of groundwater contamination can pollute millions of litres of water in an underlying aquifer. The groundwater contaminants are volatile organic chemicals used as solvents or degreasers in various industrial processes. The concentration of total volatile organics by contours indicates the degree of contamination illustrated in Fig.60. The closest to the industrial area include the highest concentrations while those at a distance of upgradient have low concentrations. The downgradient water supply well is being impacted by the contamination from the industrial area and may have to be shut down until the aquifer is clear. Groundwater scientists have used different computer models to evaluate the transport of various dissolved organic and inorganic compounds in groundwater in several situations. One modelling situation involves the assessment of hydrocarbon distribution concentrations around a contaminant source to evaluate various remedial Fig.61. Treatment system for removing scenarios including removal of the origin of petroleum components from groundwater contamination, concentration reductions resulting from consumption by microbes, the effect of groundwater recovery wells and recharge sources. The illustration shows a simple grid layout for solute transport modelling. Such models use to predict the time required for aquifer cleanup or natural concentration reductions by existing processes in the subsurface. Fig.61 shows a schematic drawing for a treatment system for removing petroleum (gasoline or on) components from groundwater. If groundwater contamination identifies on a site and contaminant concentrations are found above regulatory limits, remedial activities or feasibility studies preserve the site in compliance [312]. Such activities vary with the contaminant, contaminated medium and surrounding environmental factors [255]. Standard remedial methods include the following: excavation and off-site removal, excavation and onsite treatment, groundwater "pump and treat", soil vapour extraction, passive recovery of non- aqueous phase liquids (NAPL), enhanced bioremediation, onsite encapsulation, in-situ onsite treatment.

3.5. GEOTECHNICAL CHARACTERISTICS RESPONSIBLE FOR FOUNDATION SOIL DECAY IN ROMANIA 3.5.1. Geotechnical risk in Dobruja region of Romania/Bulgaria Dobruja, the region in the Balkan Peninsula shared by Bulgaria and Romania, locates between the eastern part of the lower Danube River and the Black Sea, including the Danube Delta, Romanian coast and the northernmost part of the Bulgarian coast. The territory of Dobruja contains Northern Dobruja, which represents the south-eastern part of Romania and Southern Dobruja, which belongs to the north- eastern part of Bulgaria. Except for the Danube Delta located in the north-eastern part of Dobruja, this region is hilly, with altitudes of 200-300 m; the highest point is the Ţuţuiatu Peak, in Măcin Mountains, 467 m. The Dobruja Plateau covers most of the Romanian part of the region. In the Bulgarian part the Ludogorie Plateau, weak in water resources but rich in underground waters, formed from karst limestones. Dobruja lies in the temperate continental climatic area; the local climate is due to the oceanic air from the north-west and north-east and continental atmosphere from the East European Plain. With average annual temperatures ranging from 11°C and annual precipitation of 450 millimetres only, the Black Sea influences not only the region's climate, particularly within 40-60 kilometres from the coast, but also

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards its geotechnical characteristics.

3.5.1.1. Reasons to study the Black Sea Basin The Black Sea consists of two main basins separated by a continental ridge (Fg.62). The western basin is oceanic while the eastern one has a thinned continental basement. Data for the timing and mechanism of opening of both basins come primarily from the geology of the surrounding regions but limit to basins itself [321]. There are several significant reasons why the Black Sea seems to be interesting. In the first place, the water area of the Black Sea locates at the boundary of arid and humid regions. The role of eolian material is relevant here. A single basin can collect data from both dry and wet zones occupying more than half of the total world ocean area. The Black Sea represent a fundamental region for the south European climate as it is the source for the south European rainfall [187]. Secondarily, the Black Sea is the largest stagnant basin in the world. The horizontal transport of suspended matter is weaker than in the other seas and occurs exclusively in the shelf regions (Fig.63). The Black Sea is almost isolated from the world's oceans. It connects with the Mediterranean Sea only through the Bosphorus Strait, which is a 35 km natural channel, 40 m deep and 700 m wide. It leads to the Sea of Marmara and then to the Aegean Sea through the Strait of Dardanelles. This natural system carries out the renewal of the bottom waters of the Black Sea with new seawater in the Black Sea very slow; it takes hundreds of years. Therefore, the Black Sea is presently the largest natural anoxic water basin in the world. Thus, 87% of its volume is practically devoid of marine life [201].

Fig.62. The Black Sea map Fig.63. The two main basins of Black Sea

Thirdly, the Black Sea is a solar place. Examining the daily temperature changes in several control fields in 810 years, scientists have proved the existence of temperature anomaly on a global scale in the sea surface. Dynamics of the atmospheric processes at the time of the generation of the anomaly conditions for the increase of solar radiation, reaching the sea surface [294]. Many marine research institutions in countries located on the Black Seashore investigate the processes producing an increase of solar radiation achieving the Black Sea surface. They are experts in marine research who already gathered a large amount of relevant data. The Black Sea offers favourable conditions for the use of satellites. Using simultaneous data from satellite systems and ground stations, scientists analysed the correlation between the sea surface temperature and atmospheric processes in the troposphere and stratosphere. The warming of the observed seawater spreads from west to east at a speed of 1,316 kph. The analysis identifies a strong correlation between the shallow anomaly and the thickness of the ozone layer. The changes in the solar radiant flux compare to the solar eruption. This natural anomaly may cause ecological changes.

3.5.1.2. Tectonic theory vs anomalous magnetic theory on the black sea basin origin 3.5.1.2.1. Tectonic Theory 3.5.1.2.1.a. Black Sea Tectonic Evolution Models The conceptions of the Black Sea basin origin show clearly their contradictions. The problem of the Black Sea Basin origin directed researches' attention since the end of the 19th century. Appeared in the early works of E. Suess in 1886, the problem has currently two distinct conceptions.

Ancuța Rotaru Habilitation Thesis

The first one assumes the basin as a remnant in the Alpine folding belt [368]. This conception shows that the valley was an ancient "matrix geosyncline depression" [153] as well as a fragment of the most ancient oceanic crust [147]; [213]. This theory assumes the Black Sea as a vast Cretaceous-Tertiary basin. It consists predominantly of two large subbasins separated by the NWSE trending Mid-Black Sea ridge. The oceanic crust floors the West Black Sea Basin, overlain by over three thick flat-lying sediments probably of Cretaceous and younger [96]; [78]. The northwest-trending East Black Sea Basin has a thinned continental or oceanic crust overlain by less than 10 km thick sediments intersected by many faults. The Black Sea opened during the Mesozoic as a back arch basin above the northward subducting Tethyan oceanic lithosphere [328]. A dominant feature of the Black Sea region continues to be its position within the ancient Tethys Ocean and the surrounding paleo-continents, which were progressing rapidly during the Phanerozoic time. Such a conception is uncertain insomuch as the most recent data on the deep basin structure along with the cover of sediment structure indicate. Giving the seismic reflection profile recording, the Black Sea Basin was superimposed on the surrounding structures at least during the Cenozoic period. Since that time, the basin has actively been progressing. The second conception assumes a new formation origin of the basin. The so-called Eucsinian Basin paved the way for the modern sea. The time of the Black Sea Basin origin is Late Neogene, but some authors assume the Early Quaternary. There are two most widespread hypotheses considering the hypothesis of the consequent Black Sea basin modern formation. The first one deals predominantly with the rapid vertical crust movement; the second one deals mainly with the crust spreading. The latter bases on 1) riftogene rupture followed by 'granite metamorphic' crust gapping, 2) suboceanic basin aerial spreading. The aerial spreading hypothesis overcomes discrepancies between the primitive plate tectonic patterns of the suboceanic Mediterranean basin genesis and geological and geophysical data. In this event, there are spreading structures within the basins and so-called "tectonic density" like orogeneses and folding systems along their boundary as the riftogenesis indications. The Zavaritzky-Benioff zones are an additional indication because they partially compensate for the seafloor spreading [153]. The heterogenic tectonic structures - from the ancient platform to recent orogenic geostructures - explains regional contradictions [27]; [208]. There are distinguished tectonic elements of various rank (structural as well as substantial complexes). Eurasian and Arabian plates with the Rodopy-Pontian subduction suture and Arkhangelsky-Andrusov lineament accredited with global structures. The earth-crust type transition of the frontal areas of the plate does not contradict seismic data. A kinematic model for the Black Sea opening based on data from onshore areas represent the third conception regarding the formation origin of its basin suggested in 1994. The model involved separate mechanisms for finding out the West and East Black Sea basin origin. The West Black Sea Basin opened by the rifting of a continental fragment from the Odesa shelf starting in the Albanian-Cenomanian. This continental fragment drifted south bounded by two major strike-slip faults, opening the oceanic West Black Sea Basin in the north and closing the Tethyan Ocean in the south. During Early Eocene, this collided with the Sakarya Zone in the south, causing a changeover from extension to compression in the Black Sea [153]. The eastern Black Sea including the East Basin, Mid Ridge and the Eastern part of the West Basin opened by a continental block rotation around a pole in Crimea. In the West Black Sea Basin, the gyration has been contemporary with the rifting. Although the mechanisms for the opening of both Black Sea basins are broadly accepted [201], there are significant disagreements on the timing of opening and location of some faults [27].

3.5.1.2.1.b. Platform Conditions Platform conditions display in the northwestern Black Sea including Bulgarian and Romanian northwestern Black Sea shelves, north of Crimea, Azov Sea and Kuban territory. The ancient East European plate and recent epi-Hercynian Scythian and Moesian plates outline there as well as an epi- platform orogenic foredeep from the Oligocene - Miocene period [366]; [369]. Recent orogenic conditions areas tend to elevate within the region. In some sectors, orogenic conditions stand out in Palaeocene and Eocene. Platform conditions manifested in the northwest of the Black Sea including Bulgarian, Romanian and the northwestern Black Sea shelves and north of Crimea, Azov Sea and Kuban territory. The Black Sea continental and suboceanic platforms are distinct within the Eurasian plate beside the mentioned frontal zone.

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards

The continental platform divides into the ancient East European platform and the recent Scythian and Moesian plates. Composed of the alteration of the Caledonian Hercynian and the Kimmerian rocks, there are areas of different folding basement age within the Scythia-Moesian Plate. The distal part, bordering the suboceanic Black Sea platform, consists of the Baikalian age rocks. Up to 22 km of sedimentary rocks cover the crystalline crust of Moesia that measures more than 25 km.

3.5.1.2.1.c. Romanian Platform Conditions The North Dobrogea crust in Romania attains a thickness of about 44 km and consists of a thick Eastern European crust overthrust by a thin 1–2 km deep wedge of the North Dobrogea Orogen. The deepening of the basement in the Dobrogea area is of 1–3 km. Based on seismic data, crust layers in Dobruja average 22 km depth at Conrad discontinuity and 45 km at Moho disruption. In North Dobrogea, the sedimentary cover extends 6 km depth, while Moho discontinuity reaches 42–43 km depth [213]. The significant platform structures are Late Permian/Early Triassic rifts. The deformed rocks of the North Dobrogea Orogen include a complex poly-deformed Variscan basement and a Permian–Cretaceous sedimentary and volcanic cover. The whole complex was overthrust NNEward onto the Scythian Platform between the Late Triassic and the Late Jurassic. The Scythian, Moesian and North Dobrogea crustal blocks belong to the southeastern extension of the Trans-European suture zone. The Trotuș-Peceneaga–Camena crustal fault separates them. Trotuș/ Peceneaga–Fault system represents a tectonically active structure formed in Quaternary. It extends down to Moho discontinuity, even deeper [369]. Fig.64. Romanian platform conditions On the Moesian Platform, the Capidava–Ovidiu Fault and Intramoesian Fault separate basements of distinct composition. The Capidava–Ovidiu Fault separates a greenschist basement to the north from a higher grade metamorphic basement to the south (Fig.64). The Peceneaga–Camena Fault and the Capidava–Ovidiu Fault are outcropping in Dobrogea area near the Black Sea [369]. On the Moesian Platform, the seismic refraction line crosses the Capidava–Ovidiu Fault and Peceneaga–Camena Fault.

3.5.1.2.1.d. Deep Sea Basin Conditions The deep-sea basin conditions are the Azov and Black Sea region tectonic. Along its boundary, the Black Sea continental slope restricted conditions existed in the Black Sea Basin in recent time. The total recent deep-sea basin subsidence seems to manifest a common Cenozoic region tendency. The seismic data analysis makes the Black Sea basin formation to retrace through the whole of the Cenozoic time. The Black Sea originated as a single basin in the Late Eocene and the Early Oligocene time. Two deepwater basins seemed to exist in the Palaeocene to Eocene time: the East and the West Black Sea basins separated by the ablation zone within the Andrusov swell and the Arkhangelsky rise. The elevation zone forming the shelf areas existed along the Maikopian boundary of the Black Sea deep basin. The Oligocene to Miocene down warping belt, namely the Sorokin and Tuapse foredeep, stretched within the northern part connected to the active system of Crimean and Caucasian orogenies. Broadening and superimposing of the subsequent Black Sea Basin on the orogenic foredeep along with the recent structural pattern change accompanied its subsequent progress recently. The Black Sea basin crust thickness is diminishing from 40-45 km within the surrounding land to 20-25 km within its central part. The East Black Sea basin crust thickness is about 25 km while the West Black Sea Basin crust has 20 km. In both western and eastern parts, the absence of the granitic layer marks the Black Sea deep basin. The "granite less" area is shallow in the eastern part because of heterogeneous tectonic elements

Ancuța Rotaru Habilitation Thesis involved in the basin formation process during the Cenozoic stage. These tectonic elements present a continental type of thin crust. The basaltic layer thickness changes from 56 km within the West Black Sea Basin to 12-18 km in the East Basin. Its density is 2.97 g/cm3 [369]; [240].

3.5.1.2.2. The Anomalous Magnetic Theory Until recently, the age of the Black Sea Basin based on land geological observations in coastal areas, underwater observations, data of seismic reflection and refraction and drilling. Formerly, the information led to a wide spreading of the age determinations: from Jurassic to Eocene. Recently, based upon the geological and geophysical data, the range of the estimated age has been considerably reduced, although this opinion is no commonly accepted. Therefore, to determine the age of the Western Black Sea Basin using an analysis of the anomalous magnetic field is of interest [153]. The double segmented character of the Black Sea manifests in the lateral variation of the heat flow pattern, anomalous magnetic T field pattern, gravity isostatic anomaly field, Bouguer anomalies and upper crust stress field. A surplus mass over the isostatic compensation level is characteristic for the East Black Sea Basin and a deficiency mass for the West Basin. The studies revealed the low-density substance layer in the upper crust from 20 to 160 km depths. The layers beneath 250 km are denser. Furthermore, positive anomalies of the observed field correspond to both depocenters [370]. Interpretation of recent data requires significant revision regarding the timing of the Black Sea Basin’s opening. The following results showed that the West Black Sea Basin opened in a short interval during the Campanian-Maastrichtian phase, through rifting of a continental sliver from the Odesa shelf. This orthogonal rift type opening has preceded the development of the Pontide magmatic arc [201]. The basin probably opened between 71.338 and 71.587 My B.P. The total duration of the opening was about 3 My B.P. (from 71.587 to 68.737 My B.P.) [193]. The Moesian and Scythian Platform are parts of the East European Platform. There are distinct magnetic anomalies resulted from differences in the crystalline basement and between the detritic and carbonaceous cover of the platform. Outside the deep-sea basin, a series of contrast magnetic anomalies mark the northwestern Black Sea shelf [193] and the land part of the East-European platform. One of them corresponds to volcanic Ilychevsk elevation, which makes it possible to interpret some anomalies. Magnetic anomalies equally mark distal structures of the Ukrainian shield. This lineament has been most active in Cretaceous. The recent movements fixed the lineament as a steep flexure bending to the West Black Sea Basin [371] together with a heat flow contrast anomaly. The Arkhangelsky-Andrusov lineament strike turns into the Thornquist line in the northwest and into the Zagros lineament in the southeast. In contrast, the East Black Sea Basin has formed through anticlockwise rotation of a large continental block during the Maastrichtian-Paleocene. This revision in the timing of the opening of the West and East Black Sea basins has direct implications on the age of the sediments in these basins [201]. This result does not agree with the present geological and geophysical data. The geophysical field variations reflect the double segmented character of the Black Sea Basin, typical for the whole period of its progress as a distinct structure from Early Cenozoic. Recent geological data and studies of the anomalous magnetic field tried to solve this issue [153].

3.5.1.3. Sedimentation versus erosion 3.5.1.3.1. Fresh Water Discharge The Black Sea Basin has asymmetric form and covers 423,000 km2 receiving river inputs from half- Europe and part of Asia (Fig.65). The total freshwater discharged into the Black Sea is 353.3 km³/year. Since it receives more fresh water than it loses [170] from evaporation, the average salinity is low, 18‰. The river discharges into this basin are built up in various natural and climatic conditions. About 500 rivers are running to the Black Sea, differing from one another by the size of their catchment areas and their water mass fluctuation. In the northwestern part of the Black Sea, Don, Dnieper, Bug, Dniester and Danube rivers deliver 75.79% of the total volume of continental waters. The absolute river discharge coming from the northwestern part of the Black Sea represents about 300 km³ of water annually [146]. Hydrological and hydrographic measurements of Romanian fluvial and sea-shore zones fulfiled upwards of 160 years [136]. In Romania, temporary streams discharge into the sea. The Danube has a catchment area of

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards

817,000 km2 and an expenditure of water in the delta of 6,268 m3/s. The river discharge into the sea represents 198 km³ of waters annually [56]; [185]; [187]; [328]. Therefore, the Danube contributes to river discharge from the northwest of the Black Sea only with more than 70% and about 56% of total river discharge. The significant volume of water delivered by the Danube to the Black Sea produces annual variations of the water table. Nearly in a centenary historical cycle, the Danube runoff periodically increased by 1.52 times, Fig.65. The rivers' basins of the Black Sea compared to the present period [212]. Its (from Black Sea GIS, 1997) maximum values came into sight during periods of increased humidity in 1940-1941, 1955, 1967 and 1980. A spring maximum (March-May) and a small peak in autumn characterise the northwestern rivers [198]. In springtime, the Danube runoff increases by 1.5 times. The maximum values from spring to early summer (April-June) are typical for the vastest rivers of the Georgian watershed [147].

3.5.1.3.2. Sediment Discharge The rivers constitute the topmost source of sediments. Their irregular supply received from different catchment areas determines the nature of sedimentation of the Black Sea [131]. The rivers discharge into the sea about 51.6 x 106 m3 of sediments accumulated on coasts and delta, participating in the modern process of sedimentation of the Black Sea. Deposits originate in the land, and their quality depends on the characteristics of the river basins and their transport capacity [147]. The terrigenous material represents a significant component of the recent sediments of the Black Sea Basin [100]. The river sediment discharged from the watershed is irregular. The most notable release comes from the Northwestern region drained by the significant rivers of the Black Sea Basin: the Danube, the Dnieper and the Dniester. A relatively small part of the discharge comes from the minor rivers of Crimea, Bulgaria and the northwestern Caucasus. The mountain watershed from Turkey and Georgia occupies an intermediate position in terms of the amount of river runoff [147]. The sediment runoff typically presents significant annual fluctuations explored primarily for the northwestern Danube, Dnieper, Dniester, Bug and northern rivers Don, Kuban [212]; [205]. Fluxes of sedimentary constituents vary quantitatively, and also in terms of granulometric composition. In the mountain/plane rivers like the Danube, the fraction of sandy-silty components increases significantly [321]. A total flux of the stream sediments consists primarily of fine-grained dispersed elements with a small amount of coarse-grained bedload material. The northwestern streams supply more silty suspensive matter compared to clayey fractions. Silt fractions surpass the clay fragments in river suspension of the Caucasian watershed in marked contrast with the Danube, the Dnieper and other waterways [376]. Sediments divide into coastal and marine ones.

3.5.1.3.2.a. Coastal (Beach-forming) Sediments The rivers transport weathered rocks from elevated areas to lower ones. The ultimate accumulation of detritus ends in seas and oceans. During this process, part of the alluvium accumulated in the coastal zone. The coastal region acts as a filter for the detritus discharging from land to sea. It delays the terrigenous material for further treatment or long preservation, supplying it to the sea [187]. In this process, the essential role belongs to river mouths, since the alluvial material is differentiated and sorted out in coastal (beach forming) and marine (deepwater) materials [205]. Thus, the river/sea mouth represents a significant area for research. The alluvium coming from the river enters the river mouth as suspended load and bedload. The mode of transfer depends on the grain size of sediments. Bottom sediments are forming the coast, creating the beaches. The coarse suspended load may also end up as coastal deposits, especially in the case of

Ancuța Rotaru Habilitation Thesis mountain’s rivers. Beaches forming sediments are coarser than 0.25 mm on the deeper pebble shores, and rougher than 0.1 mm on sandy shores [96]; [146]; [147]. Sea factors influence the river mouth offshore sedimentation. At this place, two zones of sedimentation get above: (i) a zone of wave action and (ii) a zone located below the wave base level [56]; [146]; [147]; [187]. A large amount of sediment is transported as bedload and coarse suspended load, forming submarine detritus fans and the submarine part of the delta. Fresh river water transporting a substantial quantity of sediment does not mix with marine waters. It spreads into the 23 m thick surface layer because the fresh river water is lighter than the marine water even if it contains sediments [146].

3.5.1.3.2.b. Marine (Deep-water) Sediments In the marine area, after tearing off a river stream, the bottom bed loads move partially by force of inertia but, in general, under the wave influence. The suspended load falls out of the river stream as “sandy rain”. Coarseness and intensity of this “rain” are very close to the river mouth where it settles. Offshore, the river flow discharges into the sea, forming clay fractions. Thus, river sediments accumulate in a coastal zone as continental or coastal sediments. Yet, fine-grained sediment load moves over large areas and takes part in the process of marine sedimentation [321]. The Black Sea bottom relief is moderately smooth; the maximum water depth is 2,212 m. The soft surface of the bottom reflects a prominent intensity of the regional subsidence and slight movement differentiation. The recent sediments thickness is 860 m. The great sedimentation rate does not compensate the regular Black Sea bottom sinking. This peculiar feature of the basin sedimentation manifests itself in the sediment infilling character. The upper stage sediments consist of the terrigenous silt, clay layers, carbonates interbedded with the turbidites of the Meotian to Quaternary age. Turbidites do not contribute considerably to the infilling of sediment of the Black Sea Basin except for parts neighbouring the river systems of Danube, Don, Kuban, Bzyb, Kodori, Rioni, Kelkit. Here, the rivers form thick delta fans.

3.5.1.3.2.c. Sediments in the Romanian Sector In the Romanian sector, the Danube water flow delivers an annual sediment discharge of about 31.680 x 106 m3 sediments into the Black Sea, 54,000,000 t, representing 84% of the total river sediment input. They consist of silt, clay and sand, with a grain size of up to 1.5 mm. The specific sediment discharge of this river is 38,8 m3/km2 [146]. In the relatively wet periods as 1940-1941, 1955, 1967 and 1980, the Danube River sediments played a significant role in the Black Sea sediment genesis, but between these intervals, their importance dropped sharply [136]. During the last two decades, the Danube runoff is within 4050 x 10 6 t/year [146]. The time with large and small sediment runoff from the Danube repeats every 22 years. During the last four decades, the sediment runoff of the Danube is continually decreasing due to natural and made causes. Artificial causes led to a reduction in sediment supply due to construction of a significant embankment and hydro-technical works on the Danube and its tributaries. As a consequence of dam-building on riverbeds, a decrease of the sediment discharge from the Danube basin developed [56]. The variation in the large volume of sediments delivered by the Danube to the Black Sea produced some annual oscillations in the distribution of debris in the littoral zone, with effects on the coastal morphological balance and seawater transparency. The decreasing trend of the sandy sediments input of the Danube into the Black Sea harmed the beaches, causing erosion. The beach grain-size distribution and mineral composition changed radically due to the increase of the organogenic distribution of sand and the presence of broken marine shells and snails [56].

3.5.1.4. Erosion Sediments discharging from rivers into the sea are the result of the process of erosion. Data on river sediments from different sources most often include the suspended load only. That is why observations on bedload have been conducted in very few cases only [321]. The western Black Sea coast, especially the Romanian area, has been affected by high rates of erosion, especially in the last several decades. Last 40 years, 22 km2 of beaches got lost. The erosion has primarily affected the south Romanian coastline, where relevant beach losses registered. Erosion processes are further intense during winter when storms are more frequent and powerful. Storms have induced deficits of beaches sediments. They are less frequent during the summer, and their intensity is

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards limited; however, the beaches do not restore completely and consequently, the sedimentary budget remains negative. The driving wind, waves and currents combined with anthropogenic impact on the coast, has produced increased beach erosion. Besides, temporary sea-level rise due to a wind set up and mainly in winter contributes to the erosion process [65]. The coasts are mainly sandy beaches directly exposed to wave action. The waves impacting the western shores of the Black Sea and particularly the open coasts of Romania are much energetic because of the long fetch in the southwest direction [159]. The reduction of sediment fluxes by waves, generating nearshore currents, coastal sediment transport, sea-level rise and climatic changes represented the significant causes of coastal erosion in the last decades. Hydro-technical works on the Danube and its tributaries resulted in a severe decrease of Danube sediment load, imposing negative consequences on the littoral sediment balance [56]; [77]. Moreover, hydro-technical and harbour works intercept the longshore drift, leading to a reduction of the littoral sediment budget and acute erosion [66]. Various types of protection works have been constructed in the southern part of the coast, most affected by decay [56]; [78]; [268]. Causes and effects. The rectification of Sulina branch of the Danube Delta and extension of jetties 8 km seaward determined a constant migration of sediment discharging points to areas of greater depths (>15 m). However, this sediment load has an influential role in replenishing coastal sand bars from the southern part of the coast, from Mamaia to Vama Veche. The seaward extension of the jetties for navigation purposes created a sediment trap for the sediments discharged through the Chilia branch contributing to a secondary delta north of Sulina. The Sahalin Island, a naturally formed littoral sand bar and Midia, Constanta South – Agigea, Mangalia harbour dikes disturbed the natural direction of the longshore drift, having adverse effects both on the littoral sediment budget and the shoreline. Sea level rise and intensification of hydrodynamic factors contribute to the erosion phenomenon [78]. Significant erosion occurred in the northern Romanian coastal zone (Danube Delta Biosphere Reserve) [239]; [209] wherein certain places the seawater enters 200–400 m into the beaches. In the south, the erosion represents 13 m/year. With such a rate of decay, its impact is substantial because of the destructive risk of buildings. The existing shore protection structures were severely affected by damaging factors.

3.5.1.5. Specific geology in Dobruja Region 3.5.1.5.1. The geologic history of Dobruja Region Since the end of Proterozoic, geological evidence indicates that areas from Central and South Dobruja (Fig.66) repeatedly subjected to periods of uplift and erosion followed by deposition and subsidence. Sedimentation took place in marine environments from Ordovician, passing through Silurian, Devonian, to Early Carboniferous. This terrane was close to southern Laurussia during the Lower Devonian. The northern position of the Moesian Terrane in Lower Devonian came into conflict with most of the current palaeogeographic reconstructions, but it partially supports the migration hypothesis from Gondwanaland to Laurasia in Palaeozoic. The Dobruja orogen built up under N–S compression, with strain partitioning between thrusting at its front and dextral–reverse slip along the Peceneaga–Camena and Capidava–Ovidiu faults during the Late Jurassic–Early Cretaceous. From Early Cretaceous to Late Cretaceous, the Dobruja platform was identified by SE extension compatible with the western Black Sea rifting, followed by SE drifting of part of Moesian Block. During the Late Tertiary, the Carpathian compression poorly transmitted to Dobruja. Extension dominated the Neogene deformation, indicating weak coupling between the Carpathians and their foreland [133]. North Dobruja has a composite geologic origin. Its Alpine orogen is bounded southerly by the Peceneaga-Camena Fig.66. Dobruja Region transform fault and northerly by the Sfântu Gheorghe fault (Romania and Bulgaria) [311]. During the Cambrian-Carboniferous cycle, extensive

Ancuța Rotaru Habilitation Thesis sedimentation took place in the northern Moesian Platform (North Dobruja). During the Lower/Upper Carboniferous, detrital sedimentation with local coal and clastic rocks combined with carbonate sediments. Active during Cretaceous, the Moesian platform moved at least 400 km to the west along the Peceneaga- Camena transform fault. As an effect, the western Black Sea Basin opened. In the South of Peceneaga- Camena transform fault, Proterozoic rocks crop out; on the other side, Sfântu Gheorghe fault marks the thrust front of the North Dobruja orogen over the Scythian platform. Hercynian [317] and Alpine orogenies influenced the North Dobruja. Both orogenies consist of Orliga and Megina metamorphic complexes, Boclugea metaquartzite - parts of the North African Armorican quartzite, magmatites connected to Paleozoic and Mesozoic non-metamorphosed sedimentary formations [311]. Its orogen was part of the southern margin of the Rheic Ocean and component of the north-eastern part of Gondwanaland [26]. South Dobruja is the region of the plateau and rocks of the Black Sea coast near the town of Balchik and Cape of Kaliakra (Fig.67). The area is a build-up Sarmatian sedimentary. Three horizons mark it:  Upper, Limestone horizon, made of organogenesis limestones;  Middle, limestone-marl horizon, which subdivides into two complexes: Upper complex, consisting of marls and thin intercalated beige calcareous clays, and Lower complex, composed by marls, darker coloured calcareous clays, alternating with limestones and calcareous sandstones.  Lower, clay-marl horizon made of silt clays, slightly cemented sandstones and clay marls. High plasticity of clayey materials identifies this horizon [246]. A variety of gravity structures caused by slope slumping processes shows in geophysical profiles from the peripheral shelf terrace and elevated part of the continental slope in Cape Kaliakra. On the upper slope, a series of rotational-transitional slides are developed on areas of 5 - 6" to 10" gradient. Two Fig.67. Dobruja Region in Bulgaria: Cape of circular rotational slides localize too. Data suggest Kaliakra they are geologically recent - Upper Pleistocene. The most probable triggering mechanisms are sea- level change, earthquakes or sediment instability. A system of plough structures and slide grooves developed along a tensional fault landward the slide crowns on the peripheral shelf terrace [90].

3.5.1.5.2. Tectonic activity of Dobruja Region Dobruja is the East Moesian block where the Intramoesian Fault of NW-SE direction runs along the Bulgarian-Romanian terrestrial boundary. This region is the only place South of Poland where Tornquist–Teisseyre Line, Europe's longest lineament, outcrops. The Tornquist–Teisseyre Zone or TTZ is the plate boundary of the old continent of Baltica (a Cambrian continent, present Western Eurasia). The Peceneaga–Camena Fault is regarded as a major crustal boundary within the Tornquist-Teisseyre Zone, along which large horizontal motions took place [110]. Dobruja tectonic activity is characterized in north, central, and south by the fracturing rocks from Late Jurassic to Neogene, in relation with the Carpathians and Black Sea Basin structures. The fault zone is the key structure for estimating the seismic hazard of the region, since the latest studies indicate relatively young tectonic processes. Thus, the Intramoesian fault sets bounds to the tectonic plate that subductes under the Carpathian fold system in the Vrancea Mountains. In Bulgaria, the south-eastern part of the fault has segmented structure, generating specific features of its intersection with disjunctives of another structural orientation [246]. The compression direction after the Early Cretaceous was NE–SW and since Sarmatian to Early Quaternary was NW–SE. The contemporary contraction is directed also NW–SE, according to the fault- plane solutions determined for crustal earthquakes in the region. It is suggested that there was a

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards clockwise rotation of the stress field due to the evolution of curved fold–thrust belt in the south-eastern Carpathians and the collision of the Balkanides with the Moesian Platform (Fig.68) [319].

3.5.1.5.3. The lakes of the Black Sea coast Romania has a territorial coastline extending over 244 km along the north-western side of the Black Sea, different because of Danube freshwater and load influence. The Black Sea and its coastal lakes are well-known from ancient times as unicum hydrobiological due to their specific features having an impact on the coastal area [362]. The lakes Razelm, Sinoe and Siutghiol from the former Black Sea coast lagoons are Romanian the most important lakes. Lake Razelm, 500 km², the largest in Romania, represents a group of lakes in the South of the Danube Delta covering about 1,000 km² separated into two subgroups. The northern subgroup is made up of the freshwater lakes Razelm and Goloviţa, whereas the southern group contains salt lakes. Other Black Sea coastal lakes offer spa resources as mineral waters and mud treatment therapy: Techirghiol, Tatlageac, Neptun, Belona, Corbu, Năvodari, Taşaul. The lakes are a result of slow submergence of tectonic blocks and transgression of the Black Sea water to the decreasing territory. During the last Holocene transgression, the Dobruja lakes are formed. Such types of lakes are Duranculashko, Kartaliysko, Ezeretzko, Shablensko, Tuzla, Taukliman. There are and more similar lakes to the South part of the Bulgarian Black Sea coast. All of them are separate from the sea by a stripe of sand. Periodically during the storm, the sea waves are spilling over the stripes and change the chemical composition of the lakes and territory.

Fig.68. Moesian Block, Intramoesian Fault 3.5.1.6. Geological risk and North, Central and South Dobruja 3.5.1.6.1. Limestone karsts Limestone occupies 13% of Northern Dobruja area and over 21% of the limestone regions of Romania. Loess covers them. These limestones formed a variety of landforms, including more than 59 caves. The specialists distinguish - despite blurring by denudation or fossilization - three morphogenetic types of karsts in Northern Dobruja: holocaust, naked and covered karsts (transition) and fossil covered karsts, (merokarst, criptokarst). In Romanian Northern Dobruja there are characteristic inselbergs, lapies in Popina Island and Bisericuţa (Razelm Lake), rocks near Enisala, keys in the upper valleys of Tait and Teliţa rivers or dry valleys in Babadag Plateau. There are just a few caves with no water: Tunnel Cave (Nufaru), Călugăru Cave. Northern Dobruja karsts is a relict of tertiary wet climatic conditions, similar to the types that grow today in Cuba, Antilles, Indonesia and SE China. In Romanian Central Dobruja there are natural bridges, keys (Visterna, Casimcea), karstic springs and a group of 14 caves: Lilieci Cave (400 m), "To Adam" Cave and others. In Romanian Southern Dobruja, Sarmatian limestones form a continuous plate that lies also in Bulgaria, covered by loess deposits of 30-40 m thick removed along the valleys. Caves grouped at the west of Medgidia–Negru Vodă line and around Mangalia Lake; Limanu Cave, the largest in Dobruja (3,640 m), karst lakes Gâlda–Negru Vodă and Murfatlar chalk karsts are there. The South Dobruja limestone karsts are a continuation of the picture of the Northern part of the region.

3.5.1.6.2. Abrasion and erosion of the Black Sea shore and Danube Delta In the past decades, most of the Romanian Black Sea shore areas suffered severe erosion issues, by erosion up to 2.0 m/year. The northern Romanian coastal area representing the Danube Delta Biosphere Reservation is the most affected, but its south is also in danger. The Danube River mouths were places of abundant sediment depositions. Vast progradation of Danube Delta into the Black Sea triggered during 19th century – the first part of the 20th century when Danube

Ancuța Rotaru Habilitation Thesis

Delta trapped 10–20% of river sediments [184]. For example, during 1830–1980 Chilia Branch of Danube prograded into the Black Sea 730–970 m/year, about 1.8 km2/year, 11–15 km. In the middle of the 20th-century, the situation sharply changed. The Danube Delta coastline depends on strong abrasion in response to a significant reduction of sediments due to river flow regulation. In situ measurements performed the last 30 years have indicated a continuous increase in the advancing speed of the sea towards the Romanian seashore. Chief anthropogenic activities which perturb the natural ecosystem equilibrium incorporate the building of non-properly harbour structures, coastal zone highway constructions, run-off rivers regulation and beach sediment removal. A 15-20 m/year active and almost continuous retract of the beach is attributed to a decrease in sediment supply, a rise in sea level and anthropogenic effects. Such a retreat has a severe economic and environmental impact on Danube Delta and Danube mouths Chilia, Sulina and Sfântul Gheorghe. Erosive coasts on low plateaus and plains consist of active cliffs in loess deposits with very narrow beaches in front of the rocks [381]. This intensive erosion process influences over 100 km of the Romanian resort, about 70 km being in Danube Delta. Approximately 100 ha yearly lost, 70% in the northern part of Cap Midia. The southern part of Mamaia Beach witnesses the severest erosion. Without countermeasures against beach erosion, the shorelines have retreated about 70 m in twenty years. Sandy beaches will disappear, and some hotels will be in danger of total collapse. Many cliffs are eroded by wave abrasion at their feet and slip failure in their elevated part due to the rise of the groundwater table during excessive rain. The north-eastern part of Constanţa City and the shore-side of Eforie Town occupy many buildings, but there are no preventive measures adopted near the cliffs. Their shores have eroded with a rate of about 0.6 m/year. In the northern Bulgarian Black Sea coast between the Cape of Sivriburun and Cape of Shabla, the rate of abrasion is the highest. There are three beaches - Durankulak- North, Durankulak-Krapets and Shabla in this area. The beaches boast similar features, so they display similarities in their development. Some typical features revealed in the development of the beaches as the east exposure, low identity coefficient, characteristic sickle-like form. Besides, the southern part of the beach is more sea-ward than the northern one. The coast is open to the wind waves from NE, E and SE. All of this features cause correlation in the beaches development: sand accumulation in the southern part of the beach and shore cutting in the northern one; the collection maintains a remarkably elevated area, the shore cutting is typical for the northerly parts with East-exposition; coarse and medium sands are predominant; coarse grains lie close to shoreline and front of the beach; Averaged grain-size varies between coarse-size in the northern part and medium-size in the southern one. Performed investigations show - there is relatively equilibrium of the beach dynamics. The trend is toward increasing, although the cape areas split these beaches indicate the steepest rate of abrasion in the Bulgarian Black Sea Coast [362]. Many factors account for the increasing abrasion. One of the principal causes is the construction of dams across the rivers, including the Danube, decreasing the settlement flows to the Black Sea. The second factor has in view the construction of coast-protection structures across tangential sand flows near the coast. The negative balance of the deposits near the Kamchia river mouth during the last 30 years is a typical confirmation of the thesis above. New Kamchia Dam stopped enough the influx of sediments to the mouth. There are similar problems on the South part of Bulgarian Black Sea coast too. As erosion is responsible for irreversible consequences on the environmental impact of the western Black Sea coast, assessing efficient actions to mitigate it is an urgent task. It considers the negative impact on coastal zones (tourism, transportation, harbours, industry, agriculture), costs for specific engineering structures and restoration of beaches and coastal line.

3.5.1.7. Technical works carried out on Dobruja Plateau The example of the cliff instability phenomena on the Black Sea shore of Dobruja region illustrates the relationship between causes and remediation in landslide works [218]. High-intensity environmental alarm signals [113] warn the rupture time of different lithological layers. The inventory map of Dobruja landslides has been realized only in small areas, limiting the statistical data interpretation and disabling the experts to find slope stability models useful over large zones. Therefore, all the factors triggering landslides have to be studied to develop the Dobruja landslide susceptibility map. The processes involved in slope movements involve a continual series of events that try to trace cause from effect [25]. For a particular site, the recognition of conditions causing slope instability and triggering the movement is of primary importance. Only an accurate diagnosis makes it

Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards possible to understand the landslide mechanisms and can propose effective remedial measures [217]. Monitoring the landslides plays an increasingly important role in the context of living with these natural hazards [218]. Practical examples of landslide risk and environmental impact mitigation are a strategy adopted to reduce landslide damage at km 58 of the Danube-Black Sea Canal or the complex stabilization measures undertaken in the shore area of Constanța [352]. Intensification of land-use management amplifies the hazard. Population growth and expansion of settlements and infrastructure over potentially hazardous areas have increased the landslide impact [258]. Dobruja region represents an active seismically area with sand layers prone to liquefaction. Consequently, this may damage buildings and structures [389]. Liquefaction phenomenon acts on those buildings having sand as direct foundation soil. The effect endures a sudden loss of support during the earthquake, resulting in significant irregular settlements of the foundation as well as possible building collapse and slope failures. Because of Dobruja specificity, many unique technical works emphasize its environmental potential especially in the “sensible ecological zones” of maritime port areas, significant transport knots between sea and land [183]. The wind transforms in electrical power while the only Romanian nuclear power plant lies at Cernavodă [78]. Nuclear waste deposition represents a current challenge for geotechnical engineers to identify secure practical ways to preserve radioactive waste in deep-lying bedrock [302]. The abrasion and erosion damage ask for shore protection works between Cape Midia and Mangalia City (Fig.69) in the forthcoming years. This area has high average annual wind speeds as wind farm development requires. Fig.69. Romanian Dobruja shore line Acquainted with Dobruja geoenvironmental potential, some complex technical infrastructures have risen in Dobruja region. However, the risk analysis of the Dobruja region has to consider the potential environmental impact and the existing land use issues. In the European environment, there are countries which already established well-structured procedures for taking into account extensive accident hazards in land use planning [173]. Dobruja region represents an area for which such routines are under development. Both Romania and Bulgaria carried out shore protection works related to Dobruja wind and abrasion phenomena. Foundations on limestone karsts, liquefied sand or silty clay as well as waste disposals for the Romanian nuclear power plant from Cernavodă are additionally at risk.

3.5.1.7.1. Wind farm projects Romania has the highest wind potential in southeastern Europe as it is able to produce 14,000 MW; Dobruja region is the best place in Romania and the second in Europe to give wind power. Dobruja is a region with approximately 85% windy days known for its old windmills [384]. Here, the wind blows especially from the north or northeast direction, with the highest speed near the sea. The construction of the Romanian first large-scale wind farm at Fântânele-Cogealac, 55 km far from Constanța City (Fig. 2), started in September 2008 and completed in November 2012. At the Fântânele-Cogealac Wind Complex, 240 turbines with 99 m blade diameters produce 600 MW. It surpasses the Maranchòn Wind Farm located in Guadalajara, Spain and the 539 MW Whitelee Wind Farm in Scotland, United Kingdom. It produces 10% of the Romanian renewable energy. The first offshore wind-power project

Ancuța Rotaru Habilitation Thesis in Dobruja expects its completion in 2026 along territorial waters of the Romanian Black Sea. This Wind-power Complex will produce 300 MW using wind-turbines fixed into the seawater. Vast wind generator parks estimated at 600-700MW of total power output are developing in South Dobruja near the Bulgarian towns of Kavarna, Shabla, General Toshevo, and Balchik [156]. At Fântânele, the loess foundation bed is a difficult soil. The onshore geotechnical ground investigation uses CPT from Lankelma (UK) that includes a repertoire of 17 cones and piezocones, establishing the following geotechnical aspects: nature and sequence of subsurface soil layers, in situ physical and mechanical properties (stress condition, shear strength criteria), depth and thickness of layers, groundwater conditions, data employed in geotechnical design, the inclination of soil layers in the lithological profile, the density of the soil and bearing capacity across the site. The CPT investigation additionally includes the 130 km of access roads. Some geotechnical risks evaluated by seismic analysis as liquefaction potential of loess during regional seismic activity are of particular interest. Cone penetration tests show results to map loess soils that overlie weathered schist bedrock in that area. Consequently, seismic cone penetration tests provide valuable information regarding the settlement assessment analyzing the small strain stiffness of the loess deposit.

3.5.1.7.2. Shore protection projects Erosion of the Western Black Sea coast has irreversible consequences on environmental impact. Efficient actions of assessing and mitigating it are urgent tasks considering its negative-impact upon tourism, transportation, harbours, industry and agriculture of coastal zones [157]; [381]. The Romanian seashore suffers from severe erosion issues. Corresponding to the northern part of Dobruja coastal area, the Danube Delta Biosphere Reservation suffers from strong abrasion and sediment reduction because of river flow regulation [184]. Besides, about 80 km of Dobruja southern unit between Cape Midia and Vama Veche, excluding the port areas of Midia, Constanța, and Mangalia, are additionally in danger (Fig.69). Consequently, the southern Romanian seashore needs protection and rehabilitation by creating new beach areas. The project develops through two stages: the first period between 2007 and 2020 and the second one beginning in 2021 and continuing afterwards. In the first instance, coastal protection between Mamaia and South Eforie as well as shoreline rehabilitation between Olimp and Mangalia have already performed (Fig.70). In Fig.70, the dark shaded areas between Olimp and Mangalia along the shoreline show enormous quantities of sand brought from external sources on the beach in the shoreline rehabilitation process; this phenomenon may affect the Danube River course.

3.5.1.7.3. Foundation issues on the limestone karsts, liquefacted sand and silty clay Limestone karsts typically covered with loess represent familiar layers in Dobruja. The limestone formed different landforms, including many caves. The design of the modern foundations demands additional investigations regarding the limestone caves beneath structures; geophysical methods typically complete these types of inspections. If cavities are present under the erection, the injection of a clay-cement solution is necessary to strengthen the foundation soil. During the last 5-6 years, this geotechnical problem became very actual, mostly related to the new wind generators which rise on the litoral strip of Dobruja [156]. Varna City is the most important of all Bulgarian harbours; it lies on a broad bay on the northern coastline of Bulgarian Black Sea. The soil consists of thick clay layers, which filter and reduce the amplification of seismic waves from the focus existing in front of Kaliakra Cape to the northeast. Until now, the most relevant issues have derived from slope stability and abrasion of the seacoast clay. The exclusive usage of deep foundation techniques, especially piles, can ensure the bearing capacity of the clay under intensive vertical loads and its significant seismic activity [111]. Appreciable settlements appeared soon after the breakwater of Varna City construction, in the first years of the 20th century, because of the silty clay foundation soil. Sometimes during one hundred years of exploitation, stress conditions change, increasing the soil pressure around the breakwater. The same situation can meet towards the north, around the Black Sea lakes, which represent ecosystems contaminated by the anthropic influences [25]. Peat, silty clay and fine-sand settlements identify the lake banks. Because of the vicinity of the sea, there are no tall buildings around lakes and the risk of sand liquefaction diminish.

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Fig.70. Proposed plan of shore protection in Romania, from Olimp to Mangalia seaside resorts

3.5.1.7.4. Disposals for the radioactive waste of Cernavoda Nuclear Power Plant Cernavoda NPP represents the only nuclear power plant in Romania, in Dobruja specifically. Unit 1 Reactor is in operation since December 1996, while Unit 2 started on May 7th, 2007. Unit 3 and 4 are under construction, the rest of one reactor being under the preservation stage. Since 2007, with Unit 1 and Unit 2 reactors in operation, Cernavoda NPP gives around 20% of the electricity produced in Romania. Therefore, it makes the country the 23rd largest user of nuclear power in the world [171]. Cernavoda NPP caused radioactive waste disposal issues [176]. The general opinion is that the only secure practical way to preserve radioactive waste is in deep-lying bedrock [95]. Fig.101. The compression-settlement curve for The soil of Cernavodă NPP site is a loess. Cernavodă loess Loesses have the largest additional settlements when subjected to water and present significant differences between laboratory and in situ physical and mechanical constants. Overlying Sarmatian limestone or Aptian clay, the Cernavodă loess has been studied under saturated conditions, being overflowed during tests. The specific deformation follows the natural water content and degree of saturation. Tests go through the oedometer device as well as triaxial apparatus, and Fig.71 shows the compression-settlement curve. The M2-3 oedometer module values range from 2,800 kPa to 4,800 kPa classifying the sample in the group of highly compressible soils. Because of the very high porosity of loess, its permeability may significantly decrease ranging from 1*10-10 m/s to 5*10-6 m/s when supporting heavy loads from constructions. Significant values of the internal friction angle found in the direct shear device and confirmed by triaxial tests express the aeolian nature of the loess deposit. Like so, silt and sand particles have scratched surfaces because of abrasion. The internal friction angle under consolidated drained tests is ɸ’ = 37°; under undrained–unconsolidated conditions corresponding to an excavation in the saturated loess, at a shear rate of 2mm/min, the internal friction angle is ɸ = 25°. The loess is cohesionless as the soil mass is under consolidated [25]. Consequently, the Cernavodă loess is inadequate for radioactive waste disposal. There are five rock types recommended around the world as geological barriers for underground disposals that are widespread in Romania: salt, volcanic tuff, granite, old platform green shists and clay [95]. In Dobruja Central Massif the old platform green shists are extremely hard, strong, massive and weather resistantly. This massif is a rigid horst with more than 5,000 m thick Hercynian green shists, overlaying Pre-Cambrian crystalline rocks with four stratigraphic levels: (1) the low level

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Ancuța Rotaru Habilitation Thesis consisting of coarse-grained sandstone and conglomerates; (2) the low coarse-grained level with 0.10– 1.00 m thick layers, sometimes with 1,00–3,00 m thick fine-grained intercalations; (3) the more homogeneous and massive 300 m thick upper level consisting of coarse-grained particles with 2.00– 6.00 m thick sandstones and 0.10–0.20 m thick conglomerate intercalations and a fine-grained, homogeneous and continuous layer at its upper part; and (4) the upper level with stripped and fine- grained textures. Laboratory tests determined on the green shists present the following geotechnical features: density = 2.60–2.75 g/cm3; degree of compaction = 98%; porosity = 0.4 – 2.0%; compressive strength = 80,000–140,000 kN/m2, bearing capacity > 6,000 kN/m2. The discontinuous weathering is only just up to 20 – 50 m depth. The intensity generated by the 1901 largest Pontic earthquake was no more than VII and the magnitude less than 4 Mw on the Richter scale. Following the above characteristics, five high-compacted sites from the western part of the Central Dobruja, not far from Cernavodă NPP, have been chosen to preserve radioactive waste. They possess vertical stability, thickness, hardness, homogeneity, lack of permeability and absence of fault zones. They have only 30–60 inhabitants/km2 and rare small villages.

Dobruja represents a specific region because of its intense winds eroding its shores and transforming their blowing into electricity, characteristic earthquakes, landslides or special karsts. Some conclusions may synthesize the geoenvironmental risks in this region as follows:  Dobruja earthquake and landslide monitoring fulfils an increasingly substantial role in the context of living with these natural hazards and solving important technical works built on affected areas.  The sea waves eroding Dobruja shoreline, a long-lasting programme of shore protection is required.  The soil erosion process responsible for desertification [111] leads to unpopulated areas. Knowing how to mitigate the erosion risk improving the soil quality is, so, essential to preserve the geoenvironmental integrity and get sustainable technical works on problematic soils.  Dobruja region presents specific foundations established on limestone karsts or sand and silty clay prone to liquefaction.  The number of wind farms is continuously developing and a three-time increase in the contribution of wind energy to European electricity consumption is forecast for the next twenty years [360]. One of the best ways to follow is to invest in renewable energy [156]. Therefore, large wind generator farms will be developed in the next years in Dobruja, challenging geotechnical engineers to decide the issues related to specific foundations for turbines.

3.5.2. Considerations on the hydrostatic level in Romania. Moineşti area. The study presents the groundwater movement and the influence of hydrostatic level on buildings in the area of Moineşti City, Bacău County (Fig.72). Some unusual situations may occur on the hydrostatic level due to the diversification of the local relief. The region has been heavily industrialized in the past so that economic recovery is possible based on mining and tourism activities (Fig.73). Accordingly, the area progress depends primarily on tourism development and judicious use of raw resources like mineral water springs with varied chemical composition. The study also presents a summarized water analysis of the hydrostatic level in the zone. Designs of building foundations and their operating time indicate the influence of the hydrostatic level variation. Increasing the hydrostatic level produces an unfavourable effect on foundations because of the changes occurring on the soil physical and mechanical properties in the active area: low cohesion, reduction of internal friction angle, the breakup of links between solid particles. These changes can decrease the bearing capacity leading to additional settlements. Planet Earth consists of 70% of water, the primary source of life. An approach to groundwater from the standpoint of an engineer advances several problems requiring extensive knowledge of its presence in the foundation soil. Groundwater appears in the gaps of the Earth’s crust [291]. However, a thorough analysis has determined groundwater as not the particular form of water in the Earth’s crust. Water in the soft rocks appears as follows: chemically bound water, physically bound water, free water, water vapour, and water in solid form - ice [323]. Gravitational water as a form of free water is of interest in the context of building settlements. Besides, the design, construction and building maintenance consider the groundwater movement. The groundwater of the area locates at depths between 1.4m and 10.00 m. Low flow rates and significant concentration of salts, which represent specific features of the mountain areas in Romania, characterize

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Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards the groundwater. Seepage water coming from elevated areas shapes its course to low hydraulic resistance zones (clayey sand or gravel) [196].

3.5.2.1. Climatic and geological data for the considered area Meteorological, morpho-geological and biological factors produce considerable variations of the hydrostatic level in the studied area [323].

Fig.72. Moineşti area on the physical and Fig.73. General view of Moineşti Town geographical map of Romania (after www.multimap.ro)

Meteorological factors, specific to the area are:  Air temperature. The average annual temperature in Moineşti Town oscillates around +8°C: +7.3°C in 1980 and +9.3°C in 1975. The lowest temperature recorded on 16.01.1972 was of -24°C, and the highest temperature recorded on 10.07.1980 was of +37°C. Annually, temperatures higher than 0°C occur in about 270 days.  Average annual rainfall. It is about 655 l/m2 in Moineşti area.  Precipitation intensity. Generally, the highest quantity of rains falls in June: approximately 108.6 l/m2; less precipitation falls in December: about 20.6 l/m2 [196].  Soil temperature. Considering the area locates in a temperate continental climate, the existence of four seasons leads to significant variations of soil temperature. The standard depth of soil freezing is 0.90m -1.00 m (STAS 6054/1977).  Wind speed and pressure. The estimated wind speed is 35m/s for a 50-year average recurrence interval. The reference wind pressure based on wind velocity assumes to be 0.5 kPa for a 50-year average recurrence interval (NP 082-04, 2004). The mountain area induces the dependence of morpho-geological factors on slope and relief forms. The territory lies on three distinctive areas: Moineşti Saddle holding the inner part of the town, the southern sector that is the NE extension of the Comăneşti Hollow and the NE part that includes Tazlău Valley. The research performed on Moineşti Saddle, whose highest area locates at about 480 m altitude bounded on the NW and SE by mountains reaching 700-800 m heights, does not show the interception of the hydrostatic level at depths beyond drillings. The stratification shows a clay layer with gravel debris up to 0.60 m, clay with traces of siliceous sandstone between 0.60 m and 3.50 m depth and some clay mixed with gravel and sand beneath 3.50 m depth [121]. The foundation soil consists of a clay layer with traces of siliceous sandstone exhibiting the following geotechnical characteristics: oedometer modulus M2-3 = 46.51 daN/cm2 - high compressibility; water content w = 27.80%; plasticity index IP = 46.31% - very high plasticity; consistency index IC = 0.75 - hard plastic; void ratio e = 0.61; porosity n = 37.67%; bulk unit weight γ = 19.93 kN/m3. Data collected at about 430 m altitude, from the southern part of the town that is the NE extension of the Comăneşti Hollow, have been determined on drillings performed at 6.00 m depth [19]. The hydrostatic level varies between 1.5 and 2.5 m. The lithological sequence consists of filler composed of clay, brick and gravel debris before 0.80 m, a sandy-clay layer between 0.80 m and 2.50 m and clay

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Ancuța Rotaru Habilitation Thesis beneath it. The foundation soil consists of clay with traces of siliceous sandstone. The geotechnical 2 characteristics for that layer are: oedometric modulus M2-3 = 80 daN/cm – high compressibility; water content w = 21.87%; plasticity index IP = 40.23% – very high plasticity; consistency index IC = 0.76 – plastic consistent; void ratio e = 0.78; porosity n = 43.99%; bulk unit weight γ = 18.13 kN/m3; angle of internal friction ɸ = 14°; cohesion c = 45 kPa. The NE area of Moineşti Town sets at about 420 m altitude including Tazlău Valley that suddenly expands at the exit of the river from the mountainous area and its entering into Subcarpathian Hollow. In this manner, the hydrostatic level in drillings performed in the area locates at approximately 4.00 m depth. The ground stratification highlighted by drillings is a vegetal soil composed of clay, gravel and plant debris up to 0.60 m, a layer of silty sand with gravel traces between 0.60 m and 4.00 m, and silty clay. Geotechnical characteristics of the silty sand layer with gravel traces are: water content w = 21.11%; plasticity index IP = 27.80% - high plasticity; consistency index IC = 0.63 - plastic consistent; void ratio e = 0.73; porosity n = 42.20%; bulk unit weight γ = 18.80 kN/m3 [18]. Human presence and existing vegetation represent the biological factors influencing the area. Current trends for particular buildings to the prejudice of collective housing lead to the extending of the city. It contributes to changes in the morpho-dynamic equilibrium of the area.

3.5.2.2. Hydrological data. Groundwater – depth variation report Groundwater comes typically from precipitation [172]. Moineşti is a mountain area, and its average value of rainfall is higher than in Romania. In many cases, groundwater affects foundations and even basements in lack of appropriate drainage [295]. In the considered geographical territory, both underground aquifers and deep aquifers are found (Fig.74). Underground aquifers with free water levels, without pressure, have been found at low depth in the area. The outside factors influence the hydrostatic level, which follows the general shape of the region. The deep aquifers locate between two impermeable layers. The aquifer is under pressure when the water covers the whole rock layer; otherwise, it is with free water level [18]. Fig.4 shows a cross-section of a groundwater Fig.74. Different types of aquifers, after sequence, highlighting the variation of the Mutihac et al.(1980), modified hydrostatic level in case of a permeable layer. Hydrostatic level transient occurs over time and is linked to the existing climate of the area [214]. Drillings allowed the knowledge of groundwater level and lithologic sequences of Moineşti Town area. Table 17 shows the depth of the hydrostatic level in all the performed drillings. The dissolving process of the layers encountered by the groundwater increases the level of dissolution of constituents and has an alteration effect on rocks reducing bearing capacity. Samples for determining the water chemical composition and its possible negative consequences on the existing or future Fig.75. Water in vertical profile, after Haida et al. (2004), modified

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Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards foundations have been taken from the studied area. Water laboratory tests drew out from drillings performed in the inner part of Moineşti Town revealed an intense concentration of calcium and iron: Calcium – 152.3...169.9 mg/l, according to STAS 3662/1990; Total iron – 3.142...3.338 mg/l, according to SR ISO 6332/1996. In all drillings, the chemical analysis of water established an elevated level of sulphate – up to 70 mg/l according to STAS 3069/1987; sulphides – up to 8.73 mg/l; magnesium – up to 38.67 mg/l; chlorides – up to 243.2 mg/l according to SR ISO 9297/2001 [383]. There are lots of mineral springs in town. Ensuring their appropriate use could contribute to the economic revival of Moineşti Town. Mineral springs with a high level of chlorate locate in Lucăceşti, Schela Moineşti, and Lunca. Ferruginous and sulphurous springs settle in Moineşti (Băi Park) and Lucăceşti. Sulphurous springs from Moineşti have a flow rate of 52.128 litres/24 hours. The mineral springs from Lucăceşti maintain a flow of 6.200 litres/24 hours being uncollected [306]. The relief and geological stratifications in the area cause a high hydraulic conductivity of the groundwater experiencing the water-driven phenomenon with negative consequences on the foundation soil (Fig.75) [295]. This phenomenon develops because of: • suphozy, which occupies a significant role in washing and transport processes of the soft particles, leading to the loss of ground stability [306]. • erosion affecting construction stability, developing holes of variable dimensions at the foundation contact with a sandy layer. In this event, groundwater carries along with fractions of all sizes. • scouring causing possible liquefaction phenomena on sands due to the groundwater flow velocity; • hydraulic break in groundwater flow direction when the permeability decreases in nonhomogeneous soils [172]. Table 17. Hydrostatic level for different performed drillings Drilling F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 Drilling 6 6 4 4 6 8 6 6 6 6 8 depth [m] Hydrostatic 2.5 1.5 3.5 1.8 3.5 -- -- 4.1 -- 4.0 -- level [m]

The following conclusions can be withdrawn from the considered area:  A rich content of chemical substances exists in the groundwater at depths ranging between 1.50 m and 10.00 m affecting foundations and the foundation soil.  The presence of groundwater at shallow depths, a low permeable soil, and the absence of drainage works lead to water presence in downtown building basements.  The chemical composition of water influences the soil behaviour as a three-phase system. To protect the future or existing foundations in areas with high mineral content in the groundwater, in situ measures have to be adopted [346].  Being a mountain region, there is a spring flood risk. Therefore, measures minimizing the effect of floods are: avoid deforestation on slopes or excavations, artificial gradient overflow and adjustment works dispersing the water energy and decreasing its erosive action [195]; [255].  Because of the economic decline of the area, the research activity stopped lately so that information helps in design, performing, and maintenance of engineering works in the area.  The economic and tourist potential of the area has to be exploited. Thereby, a sustained research activity has to give all the necessary data for designing and execution of engineering works.

3.5.3. Difficult foundation soils/swelling-shrinking clays in Iași City, Romania The research program has investigated some processes responsible for difficult foundation soils in Iași, Romania (Fig.76) [263], [300]: earthquakes, landslides, swelling-shrinking phenomena in clays. The study presents the behaviour of swelling-shrinking clay of Iași and its swelling anisotropy, to estimate the depth of the active zone and produce predictive models used to estimate the swelling potential of swelling-shrinking clays from their mineralogical and engineering characteristics [257]. The landslide in the intensive seismic zone has its peculiar features.

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Some slope may be stable under static load (normal state). When the climb is in the limit equilibrium state, even a slight earthquake may destabilize. An intensive shake may be the cause of a slope to fail. Iași City locates in an active seismic zone. There, many earthquakes with significant intensities occurred in the past. Iaşi City settles in north-eastern Romania, where the 47o 10' N parallel meets the 27o 35' E meridian. It is the capital of Iaşi County, with an area of 5,470 square kilometres. Seated on seven hills which cover 3,770 ha, Iași City has an altitude varying between 40 meters in the Fig.76. Iași County in Romania’s map Bahlui Meadow and 407 metres in Păun Hill. The climate is temperate continental, with dry- hot summers and frosty winters. Iaşi area lies at the crossing point of two significant geographical sub-units of the Moldavian Plateau: Gentle hills whose elevation increase going west, where they meet the Eastern Carpathian mountain chain, the Moldavian Plain and the Central Moldavian Plateau. The Bahlui River crosses Iași City. Its meadow contains sensitive soils like contractive and macroporous clays, which puzzle the location and design selection as well as building execution and exploitation.

3.5.3.1. Swelling-shrinking clays from Iaşi area, Romania During the last three decades, damage due to swelling phenomena of swelling-shrinking clays from Iaşi area, Romania has been detected more clearly in some parts of Iaşi where the rapid expansion of the urban areas led to the construction of various structures. Foundation soil consists primarily of brown plastic clay with thin zones of bluish and yellowish. To -1.10m, the plastic clay is stiff and it is possible to dig it. From this depth to -1.90m, the colour becomes darker with ferruginous zones with concretions of limestone; the clay is very stiff so hard to dig it. This sector allows the influence of the compressive process, realized by repeated dry and wet tests. Between -1.90 and -2.40 meters, the colour becomes brown-black with ferruginous and bluish zones. From -2.40 to -3.20 meters, the water content keeps constant; the clay is stiff, yellow with bluish–ferruginous zones, and has plastic consistency. The natural water content varies from 28% to 43% [25].

Fig.77. Shrinkage coefficients Fig.78.a, b. Water content versus geometrical dimensions α1, αs, αv for Iași clay before and after drying for Iași clay

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Iaşi clay is high-plasticity inorganic clay with a clay fraction between 61% and 82%. Natural unit weight: 1.67 g/cm3 – 1.69 g/cm3; Dry unit weight: 1.23 g/cm3 – 1.35 g/cm3; Porosity: 5.1% – 55.6%; Degree of saturation: 0.701 – 0.984. Bahlui soils contain clay minerals that absorb water when wet causing them to swell and lose water as they dry, making them shrink. That is why Bahlui clays classify as very active soils and over-swelling – shrinking soils in terms of shrinkage and swelling [74]. Geotechnical indices indicating the properties of these clays are the shrinkage coefficients α1, αs, αv [280]. The montmorillonitic clay of Iaşi has the following values (Fig.77) [228]: αl = 0.52; αs = 1.17; αv = 2.03. Experimental tests for swelling pressure determination develop in triaxial apparatus or adapted odometers. Observations indicate that clays from Iași area produce volume changes and movements of the ground in connection with the transmitted pressure and water content (Fig.78.a,b) [227]. Computing the volumetric swelling coefficient based on experimental results, the volume coefficient values vary from -0.2 to 1.0. Regarding Bahlui clays, the plasticity index, the grain – size composition and distribution, consistency index and activity index classify these soils into active and very active [280]. The chemical and mineralogical study of Bahlui Meadow soils, colour reactions, electron microscope and thermodynamics analysis concludes that most clay minerals belong to montmorillonite and hydrated mica group. The wetting heat classifies the clay as swelling – shrinking soils.

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4. SUSTAINABLE DEVELOPMENT OF MATERIALS USED IN SUBSTRUCTURES 4.1. THE FLY ASH – A CEMENT-LIKE MATERIAL USED IN SUBSTRUCTURE AND ROAD WORKS Fly ash, a coal combustion product once treated as a waste laid-out in landfills, is used today in substructure and road works. The research of fly ash properties may solve the problems of treatment and intelligent use of this residual material. Using laboratory tests specimens, physical and mechanical properties of pozzolanic coal fly ash, a bituminous coal waste of Iași thermal power station, Romania, are investigated to analyze the composition of fly ashes, sometimes associated to the production of those from Suceava thermal power station, Romania. The use of fly ash as a partial replacement for Portland cement is generally limited to the bituminous coal fly ash. Fly ash improves cement performance making it more effective, more durable, and resistant to chemical attack. The recycling of fly ash has become an increasing concern in recent years. Soil stabilization demands fly ash addition to improving the engineering performance of a specific soil. The paper describes some benefits of fly ash use for our environment. The use of fly ash granted in recent years primarily due to saving cement, consuming industrial waste and making durable materials, expressly due to the fly ash stabilization improvement.

4.1.1. Physical Characteristics of Pozzolana Fly Ash from Thermal Power Plant of Iași, Romania Pozzolana applied since Antiquity. Its name comes from the volcanic ash from Pozzuoli, a harbour of Southern Italy, 11 Km west of Naples, where it witnessed for the first time. The town is on the Bay of Pozzuoli, a section of the Bay of Naples, 27 Km from Vesuvius. In 79 A.D. this volcanic ash completely buried the city of Pompeii, near modern Naples, therefore preserving it for today. Romans, replacing the limestone with shale and shale limestone in lime ovens and increasing combustion temperature, got a fine milled material. Mixed with volcanic ash, it is considered to be the first cement in history. This mixture was called “pozzolanic cement”. In his tenth volume De Architectura, Vitruvius devotes a chapter (Book II, ch.VI) to this “powder which, by nature, produces excellent results”. He speaks there of four types of pozzolana: black, white, grey and red. Vitruvius specified 1 part lime to 3 parts of pozzolana for the cement used in buildings and 1 part lime to 2 parts pozzolana for underwater structures. The ratio for modern constructions using pozzolana cement is more or less the same [162]. The use of fly ash as a pozzolanic ingredient was recognized as early as 1914, although the earliest noteworthy study of its use was in 1937. Before losing its usage in the Dark Ages, Roman structures like the Coliseum (Fig.79), Baths of Caracalla, Pantheon (Fig.80) in Rome, the Apian Way in Italy or Pont du Gard aqueduct in South France, used volcanic ash similar to pozzolana for a waterproof resistant concrete. This concrete extensively used in the Roman world when making large outdoor structures like jetties, harbour works, and water channels can harden underwater. The building of the Roman port of Cosa used pozzolana poured underwater, apparently handling a long tube to carefully lay it up without allowing seawater to mix with it. The three piers are still visible today. They conserve underwater portions in excellent conditions after 2100 years [179].

Fig.79. Details of Coliseum in Rome Fig.80. Entrance to the Pantheon in Rome

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The fine-grained volcanic tuff (pozzolana) erupting during the 17th century B.C. on the island of Thera (Santorini) in Greece, was called “the Santorini earth”. It was quarried in mid-nineteenth century A.D. and shipped to Egypt for cement lining the Suez Canal. Pozzolanic natural cement represents for millennia the exclusively available material for lining cisterns and aqueducts and binding the brick and stone of waterfront structures and monumental buildings. The lining of a cistern in Kamiros, Rhodes (230 km east of Santorini), dating from the 6th or 7th century B.C. is still in existence [60] Pozzolana represents a siliceous and aluminous material having reduced or no capacity to cement in its natural state. In the presence of water, it reacts to calcium hydroxide at an ordinary temperature forming compounds with cementing properties. From the chemical point of view, the pozzolans define as composite systems formed of calcium (CaO) silica (SiO2) and alumina (Al2O3) in phases that may consist of solid-liquid disperse systems. They interact, forming masses that harden in certain conditions and transform themselves into stable and durable materials [243]. Modern pozzolanic cement represents a mix of natural or industrial pozzolana and Portland cement. In addition to underwater use, the high alkalinity makes pozzolana resistant to corrosion from sulphates. Once fully hardened, the Portland cement-Pozzolana blend may be more durable than Portland cement due to its lower porosity. That equally makes it more resistant to water absorption. The Portland Pozzolana Cement is a regular Portland cement blended with pozzolanic materials (power station fly ash, burnt clays, ash from burnt plant material or silicious earth) either together or separately. This cement forms extra-strong cementing material which resists wet and thermal cracking and maintains a notable degree of cohesion and workability in concrete and mortar. The fine-grained volcanic tuff (pozzolana) erupting during the seventeenth century B.C. on the island of Thera (Santorini) in Greece, was called “the Santorini earth”. It was quarried in the mid-nineteenth century A.D. and shipped to Egypt for cement lining the Suez Canal. For millennia, pozzolanic natural cement represents the exclusively available material for lining cisterns and aqueducts and binding the brick and stone of waterfront structures and monumental buildings. The lining of a cistern in Kamiros, Rhodes (230 km east of Santorini) dating from the 6th or 7th century B.C. is still in existence [60]. It was only in the late 19th century that Portland cement gradually replaced the pozzolanic cement.

4.1.1.1. Fly ash - general features Natural pozzolanic ash is still being used in various countries like Greece, Italy, Germany, Mexico and China [60] because it reduces costs and improves quality and durability of concrete. The substitution of Portland cement with fly ash reduces the greenhouse effect of concrete significantly reducing carbon emissions associated with construction activity. An industrial source of materials with pozzolanic properties is the siliceous fly ash from coal-fired power plants [277]. Fly ash is a mineral waste, a residue generated by fuel combustion (coals). Fly ash goes out from the chimneys of coal-fired power plants. There are millions of tons of fly ash produced and stored in each thermal power plant. Depending upon the source and makeup of the burned coal, the components of fly ash vary significantly. However, all fly ashes include substantial amounts of silicon dioxide (SiO2) (both amorphous and crystalline) and calcium oxide (CaO). These wastes are polluting materials [303]. New fly ash production by burning the coal produces approximately twenty to thirty tons of CO2 per ton of fly ash. Fly ash contains trace concentrations of heavy metals and other substances that are known to be detrimental to health in sufficient quantities. Toxic constituents include barium (806 ppm), strontium (775 ppm), boron (311 ppm), vanadium (252 ppm), manganese (250 ppm), zinc (178 ppm), chromium (136 ppm), copper (112 ppm), chromium VI (90 ppm), nickel (77.6 ppm), lead (56 ppm), arsenic (43.4 ppm), cobalt (35.9 ppm), fluorine (29 ppm), thallium (9 ppm), selenium (7.7 ppm), beryllium (5 ppm), cadmium (3.4 ppm), mercury, molybdenum, radium, thorium, vanadium, along with dioxins and polycyclic aromatic hydrocarbons (PAH) compounds [127]. Fly ash typically contains 10 to 30 ppm of uranium comparable to the levels found in some granites or phosphate rocks and black shale. However, coal fly ash did not need to be regulated as hazardous waste because its radioactivity compares to that derived from common soils or rocks. Fly ash, even when coming from a single power plant, is not homogeneous to radioactivity content. If the fly ash comes from lignite, as in the thermal power plant of Iași, it will display a particular radioactive behaviour. Lignite contains natural radionuclides from the Uranium and Thorium series and 40K, transferred in fly ash influencing the fly ash applications with their activity and concentration. Determination of the radioactivity content of fly ash can be realized gamma spectrometry and

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Ancuța Rotaru Habilitation Thesis sometimes employing an intensive and costly scientific method: alpha spectrometry, although the use of such analysis is not justified in many cases, as the activity levels found in fly ash are generally correct determined by gamma spectroscopy. The most determined radionuclides using gamma spectrometry are 238U, 226Ra and 210Pb [326]. Besides natural radioactivity content, radon exhalation from fly ash is another issue generally determined in its analysis. In the past, fly ash produced from coal combustion was entrained in flue gases and released into the atmosphere. Pollution control equipment mandated in recent decades requires fly ash capture before release. Fly ash material solidifies while suspended in the exhaust gases and is collected by electrostatic precipitators or filter bags. Fly ashes are proper to accomplish specific elements and structures of architectural open spaces like road construction [49], river channel adjustments, retaining walls and shore defence. Nohow they are intended for housing or social activities. It is increasingly finding use in the synthesis of geopolymers and zeolites as well. In the road construction field, in situ gamma spectrometry supplements fly ash laboratory analyses [245].

4.1.1.2. Chemical analysis of fly ash from Iași thermal power plant Fly ash is one of the burnt coal byproducts (Fig.81). Fly ash contents vary by the type of burnt coal. In Romania, vast amounts of grey fly ash result from the combustion of fine-grounded lignite of the Oltenia Basin in thermal power plants. In comparison with fly ashes resulted from burning hard coal, those resulting from the combustion of lignite have relatively minor differences in oxides content excepting CaO present in large quantities in the fly ashes resulted from lignite combustion [163]. The burned coal (anthracite, bituminous, sub-bituminous, and lignite) [127] influences the fly ash properties. The burning of anthracite and bituminous coal produces fly ash pozzolanic in nature, which contains less than 10% lime (CaO). Fly ash produced from the burning of the lignite also has some self-cementing properties. In the presence of water, this fly ash will harden and gain strength over time. This fly ash generally contains more than 20% lime (CaO).

Table 18. Chemical composition of fly ash from different types of coal Anthracite Sub Component or bituminous Lignite Bituminous coal % % % SiO2 2060 4060 1545 Al2O3 535 2030 2025 Fe2O3 1040 410 415 CaO 112 530 1540 Loss of 015 03 05 ignition

The determination of pH of fly ash from Iași thermal power plant uses 50 g fly ash mixed with 250 cm3 distilled water. The mixture was shaken for 30 minutes, left 1 hour and then the pH was read. The obtained value of 5.8 places the Iași fly ash at the limit between acid and alkaline solution. In general, fly ash consists of three component groups, as Table 18, Table 20, Table 22 presents [243]. The first group exhibits low water reactivity but possesses electric charge (may adsorb metal cations Fig.81. Fly ash made in a dry boiler like Cd, Ni, Pb, or oxyanions). These solids are composed of SiO2,

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Al2O3, and Fe2O3. The second group of components present in coal fly ash represents metals or metalloids adsorbed onto the oxide surfaces. The chemical behaviour or the release of heavy metals and oxyanions to water are related to oxide electric properties. The third group includes highly water-reactive components. It contains oxides of Ca (215,000 ppm), Mg (16,000 ppm), K (23,000 ppm), Na (2,000 ppm), gypsum and sulfite (SO3). Some fly ashes from bituminous coal are acidic and possess no liming value. Most fly ashes from lignite have a high liming value because of their content of alkali oxides and significant quantities of anhydrous Ca or Mg sulfates. Fly ashes from bituminous coal are low in Ca and Mg [160].

Table 19. Chemical composition of fly ash from thermal power plant of Iași Chemical composition (average values) Thermal power plant SiO2 Al2O3 Fe2O3 CaO SO3 Other Iași 50.05% 32.42% 7.58%

5.60% 3.76% 0.59%

Σ = 90.05 admissibility conditions SiO2 + Al2O3 + Fe2O3 > 70 min. 5.0 max. 3.0 max. 5.0

Table 20. Chemical composition of fly ash from thermal power plant of Suceava

Chemical composition (average values)

determined from Xray Fluorescent analysis

Thermal SiO2 Al2O3 Fe2O3 CaO SO3

power plant % % % % %

Suceava 57.50 21.30 5.71 4.51 0.42 Σ = 84.51 (according to DIN EN 1962)

admissibility conditions SiO2 + Al2O3 + Fe2O3> 70 min.5.0 max.3.0

Other chemical components (average values)

Suceava MgO Na2O K2O TiO2 P2O5 F 1.51% 0.73% 2.21% 0.77% 0.56% < 0.50% Σ < 6.28 admissibility conditions max. 5.0 Total 99.80%

Table 21. Characteristics of fly ash from Iași thermal power plant

Indices Basicity CaO

Fly ash type

basicity activity quality module %

0.112 1.54 0.78 0.095 5.60 aluminosiliceous

Table 22. Chemical investigation of Suceava fly ash Components Determined values Admissibility conditions % % Loss of ignition 4.80 < 5.00

SO3 0.40 < 3.00 Chloride 0.01 < 0.10 CaO 0.34 < 1.00

5.1.1.3. Physical features of fly ash from Iași thermal power plant Fly ash particles are generally spherical in shape and range in size from 0.5 to 100 (Fig.83). 75% of the ash have a carbon content of less than 4%. The ordinary spherical shape indicates particles formed under uncrowded freefall conditions and a relatively sudden cooling maintained the spherical shape [202]. They consist primarily of silicon dioxide (SiO2) present in two forms: amorphous, which is rounded and smooth, and crystalline, which is sharp, pointed and hazardous; aluminium oxide (Al2O3) and iron

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oxide (Fe2O3) (Table 19, Table 21 compared to Table 20, Table 22). The carbonaceous material in fly ash is composed of angular particles. The particle size distribution of bituminous coal fly ashes is similar to that of silt (less than 0.075 mm). Although sub-bituminous coal fly ashes are silt-sized, they are slightly coarser than bituminous coal fly ashes [243]. Fly ashes are generally highly heterogeneous (Fig.83), consisting of a mixture of glassy particles with a various identifiable crystalline phase like quartz, mullite, and iron oxides [143]. In terms of mineralogy, fly ashes structurally consist of a crystalline phase and a vitreous phase. Experimentally, ashes developing a vitreous condition possess superior cementing properties [148]. The particle size distribution of most bituminous coal fly ashes is broadly similar to that of silt (Fig.82). The specific gravity of fly ash typically ranges from 2.1 g/cm3 to 3.0 g/cm3, while its specific surface area (measured by the Blaine air permeability method) may vary from 1,700 to 10,000 cm2/g.

100 % 90 80 70 60 50 40 30 20 10 0 0.001 0.005 0.02 0.91 0.2 0.5 1 2 5 10 20 31.5 0.002 0.01 0.05 0.1 025 0.69 3.1 7.1 1 16 d,mm

Fig.82. Grain-size distribution curve of Iași fly ash

The fly ash colour vary from tan to grey or black depending on the amount of unburned carbon (Fig.84). Lighter the colour lower the carbon content. Lignite or sub-bituminous fly ashes are usually light-tan to buff in colour, indicating relatively low amounts of carbon as well as some lime or calcium. Bituminous fly ashes are, typically, some shades of grey with lighter shades indicating a higher quality of ash Fly ashes have a spherical shape, a ball-bearing effect causing lubrication, good strength, workability, reduced permeability [150], sulfate attack, efflorescence, shrinkage, slump loss, segregation, the heat of hydration and alkali-silica reactivity [243].

Fig.83. Heterogeneous grain-size of fly ash Fig.84. The colour of fly ash varies from tan to black

The shrinkage observed after 7, 14, and 28 days demonstrated is stops after 10 days and the material stabilized. The shrinkage varied from 0.70 mm/m in 7 days to 0.90 mm/m in 10 days. These values pose the shrinkage of the fly ash over an ordinary concrete class (εc < 0.42) but under regular mortar shrinkage (εc < 2 mm/m). The thermal conductivity coefficient is the same like brick coefficient and less than the concrete coefficient. Fly ash possesses good hydraulic properties. The average apparent

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Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards density of a fly ash mixture with 20% water, 32% sand, 48% binder is 1840 kg/m3 in 7 days and 1770 kg/m3 in 28 days. The permeability of well-compacted fly ash ranges from 104 to 106 cm/s, roughly equivalent to the standard range of permeability of silty sand to silty clay soil. The permeability of a material is affected by its density or degree of compaction, grain-size distribution, and internal pore structure [204]. As fly ash consists almost exclusively of spherical shaped particles, they become densely packed during compaction occurring low permeability values and minimizing the seepage of water [175]. Table 23 presents physical features of fly ash from Iași thermal power plant and Table 24 shows some physical characteristics of fly ash from Suceava thermal power plant.

Table 23. Physical features of Iași fly ash Table 24. Physical features of Suceava fly ash Physical features Iași fly ash Physical Specific surface (Blaine No.) cm2/g 3490 features Determined Admissibility Density g/cm3 2.209 values conditions Bulk density g/cm3 loose state 0.735 Grain fraction 25.00 % < 40.00 % densest state 0.947 > 0.045 mm 2165 Grain density Kg/m3

5.1.1.4. Compaction characteristics of fly ash from thermal power plant of Iași Compaction fulfilled in two sequences: 30 jolts in 30 seconds for the first half fresh material and 30 jolts in 30 seconds for the steel mould filled with new material [24].

1.4 ρd(g/cmc) 1.3 1.2 1.1 1.0 0.9 0.8 w% 51015202530354045

Fig.85. Modified Proctor compaction test curve

Table 25. Compaction characteristics of Iași fly ash Compaction characteristics Iași fly ash 3 ρdmax (g/cm ) 1.084

w (%) 35 opt

Compared to low calcium fly ash, the optimum moisture content is low, and the maximum dry density is high for high calcium fly ash. Optimum moisture content is directly proportional, and maximum dry density is inversely proportional to the carbon content [229]. Table 25 and Fig.85 show laboratory compaction characteristics (modified Proctor compaction test) of fly ashes from Iași thermal power plant.

4.1.1.5. Environmental issues concerning fly ash from thermal power plants Much of the fly ash generated in power plants lays-out in landfills. This ash, however, is capable of being recovered and used. The fly ash successfully uses as a mineral blend in Portland cement concrete. It is significant in strengthening the concrete composition [41]. Physical properties of the fly ash include texture, loss of ignition and pozzolanic reactivity. Another employment of fly ash is as a substitute mineral filler in asphalt paving mixtures. This material consists of particles less than 0.075 mm in size filling the voids

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Ancuța Rotaru Habilitation Thesis in a paving mix that improves the cohesion of the asphalt cement and the stability of mixture [204]. Fly ash operates as an embankment or structural fill material, particularly in Europe, performing like a well-compacted soil. As an embankment or fill material, fly ash is a substitute for natural soils weather it works at its optimum moisture content to ensure the composite is neither dry and dusty or wet and unmanageable [326]. Fly ash disposal can be in a wet mode or a dry one. Dry storage includes some risks regarding material loose due to its dispersion by the wind and, consequently, air pollution, especially into populated areas [380]. If the fly ash mixes with water, the mixture prevents its dispersion by wind. The quantity of fly ash resulted in the technological process of thermal power plants diminishes due to technology. Suceava thermal power plant, the comparative example of this study, generated only 30 thousand tons of fly ash in 2006 in comparison with 230 thousand tons resulted in the previous years. Nevertheless, Moldavian thermal power plants have an insufficient storage capacity, and the fly ash is transported and stored as hydro-mixture [67].

Table 26. Fly ash construction related applications

Applications Percent of total used 60 Cement production and/or concrete products

Structural fills or embankments 17

Stabilization of waste materials 14

Road base or subbase materials 5

Flowable fill and grouting mixes 2

Mineral filler in asphalt paving 2

Approximate Total 100

Generally, fly ash represents the lighter material (65% to 80%) of the coal ash and its properties vary with coal source, type of coal burned and ash collectors [54]. The reuse of fly ash as an engineering material primarily stems from its pozzolanic nature, spherical shape, and relative uniformity [99]. Comparing chemical composition with the admissibility conditions of fly ash from Iași thermal plant (Table 19), the following results were acquired [48]:  The fly ash obeys the conditions relating to oxides components (SiO2, Al2O3, and Fe2O3); CaO content is within acceptable limits;  Fly ash for stabilized road structures has an SO3 content within a maximum of 4%, although it is greater than the permitted limit for additives in concrete and mortars [144]. Advantages for the use of thermal ash are [48]:  Fly ash captured from percolators of thermal power plants uses in road works for form, foundation or base layer achievement [35].  The significant values for Ra 226, Th232 and K40, [Bq/kg] reduce when some materials used in road layer implementation incorporate fly ashes [81].  The usage of thermal ash, a pollutant waste, improves the ecological environment and diminishes landfill areas for waste storage [247].  With characteristics of thermal fly ashes, a base layer by such concrete possesses excellent resistance to compression and increases the viability of traffic routes, embankments and dams [175]. Table 26 presents the most significant applications of the fly ash in construction works [48]. Fly ash recycling includes practice in embankments and structural fills [60], waste solidification, mine reclamation, soft soils and waste stabilization, flowable fills, roofing tiles, compacted concrete dams [16]. Because fly ash contains toxic elements, disposal sites monitoring should for an excessive buildup of heavy metals, salts and alkalinity. Potential heavy metal issues of power plant wastes diminish because of the pronounced liming effects of wastes [54]. An environmental issue is the heavy metal movement from fly ash in ponds or landfills to drainage waters.

4.1.2. Mecanical Characteristics of Pozzolana Fly Ash from Thermal Power Plant of Iași, Romania The gain in strength with time for high calcium fly ash is very high compared to low calcium fly ash due to reactive minerals and glassy phase presence [216]. When replacing a part of the cement by a high

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Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards amount of fly ash, changes in strength development and resistance to carbonation may cause problems in the concrete applications to actual building construction regarding the structural and durability requirement [148]. Though the replacement of a part of fine aggregate by fly ash reduces low strength development, higher rates of carbonation of the concrete may remain as a problem as calcium hydroxide consumes by pozzolanic reaction with the fly ash [233]. Shear strength tests conducted on fly ash samples show that fly ash derives most of its shear strength from internal friction, although some apparent cohesion has been observed in bituminous (pozzolanic) fly ashes [216]. The sample density and moisture contents affect most the fly ash shear strength at the optimum moisture content. The friction angle: 26° - 42° [180]. Pozzolanic activity is determined based on the physical activity index, given by the relation: R cemtest I = x 100 [%]

R refcem where: 2 R cemtest means compressive strength determined on mortar prisms (N/mm ) 2 R refcem means compressive strength, determined on referential mortar prisms (N/mm ).

The index of activity for fly ashes of Iasi is “I” and represents the minimum activity index. Consequently, the usage of Iași fly ashes as mortar addition is not recommended [245]. Determination of the pozzolanic activity of various materials such as fly ashes is essential for their efficient application in cement [61]. It also occupies a significant role in material selection as a stabilizer in various environmental projects [163]. It demands the development of practice for stimulating the pozzolanic activity of different materials, quite rapidly and simplistic. With this in view, a method that estimates pozzolanic activity of fly ash has been developed [143]. The modified ASTM method determines the compressive strengths on samples of a mixture of one part calcium hydroxide, two parts fly ash and three parts monogranular sand (particle size mainly between 1 and 2 mm) [57]. The quantity of water introduced corresponds to the compaction optimum moisture content. The mixture compaction occurs into cylinders with 5 cm diameter, 10 cm height kept at 23°C for 24 hours and 55°C for 6 days [16]. To be considered active fly ash, the 7-days compression strength must be greater than 5.5 N/mm2 [59]. The proposed method for pozzolanic activity consists of compressive strength determination as follows:  after 2 days for samples kept in a moist atmosphere;  after 7 days for samples kept in a humid atmosphere and then subjected to strengthening under accelerated thermal conditions for 6 days;  after 7 days in a moist atmosphere by hardening under accelerated thermal conditions. Mixtures are composed of 90% fly ash and 10% hydrated lime powder. The amount of supplemental water corresponds to optimum moisture content from the modified Proctor compaction test. No matter chemically active they would stay, alumino-silicate fly ashes like those from Iași thermal power plant do not demonstrate hydraulic properties in the presence of water [50]. Along with water and by activation with CaO, the hydration, cementation and strengthening processes occur displaying two stages. In the first stage forms the ettringite (calcium sulphoaluminate) and in the second one, pozzolanic reactions for calcium silicate hydrate (CSH) and calcium aluminium hydrate (CAH) formation take place. The cementation of compounds develops in an extensive period so that early mechanical resistances of cementation products are reduced, unlike those exhibited in a long time [189]. Extensive use of pozzolanic binders in substructure and road techniques, especially in stabilization [54], aims to reduce the lime and cement [35]. Worldwide, there are many approaches for designing parameters for materials stabilized with pozzolanic binders [206]. Forasmuch as Table 27 shows, after rating compaction characteristics of natural aggregates mixtures containing fly ash (maximum dry density ρdmax and compaction optimum moisture content wopt) samples depending on the size of natural particles are carried out. There are three series of natural ballast samples. The ballast stabilizes with fly ashes in a dosage of 20%, 25% and 30% kept in a moist atmosphere [189]. On these samples, both physical and mechanical characteristics (compressive strength Rc, tensile strength by compression on generators Rtg) at ages of

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14, 28, 60, 90, and 180 days were decided [48]. The comparison of chemical composition with the admissibility conditions of fly ash from Iași thermal power plant leads to the following results:  It satisfies oxidic component condition (SiO2, Al2O3, Fe2O3); CaO content is in allowable limits;  Although the SO3 content is greater than the limit, this compound is within 4%, the maximum value for operating the fly ash in stabilized road structures [234].

Table 27. Sample dimensions based on Dmax

Maximum Sample dimensions Sample

particle size Diameter Height volume

Dmax mm cm cm cm3 31 7.14 10.50 420

7 5.05 7.50 150

In terms of pozzolanic activity, results of the modified method (Fig.86) show that for a strength of 96 daN/cm2, the Iași fly ash is pozzolanic. The proposed method shows that the compressive strength is over 55 daN/cm2 (Table 28) certifying pozzolanic activity [143].

Rc daN/cmp Table 28. R compressive strength for fly ash mixture and lime 100 c 90 2 Compressive strength Rc [daN/cm ] 80 Mixture Strengthening development 70 type normal thermoaccelerated 60 at 7 days at 28 days at 7 days 50 90% Iași fly ash; 40 37.07 58.09 55.42 10% lime 30 20 10 Time 0 days 0 7

f* fundation Fig.86. Hydraulic evaluation using the modified method b* bedding

Table 29. Physical characteristics of Iași fly ash stabilized natural ballast Cement Absorbtion % γ γ γ dosage w d dmax after after Admitted layer % 3 3 3 daN/cm daN/cm daN/cm 7 days 14 days f* b* 20 2.070 1.890 5.33 6.84 25 2.034 1.858 1.890 7.39 9.03 10 5 30 1.983 1.811 8.26 10.04 Swelling % Mass lost % after after Admitted layer after after Admitted layer 7 days 14 days f* b* 7 days 14 days f* b*

2.43 3.04 6.69 3.97 2.94 4.09 5 2 2.98 4.02 10 7 3.07 4.43 2.12 6.72

For 25% fly ash dosage, the 180-days strength must represent about 2/3 of 360 days strengths. Table 29 presents the physical characteristics of stabilized natural ballast and 20%, 25% and 30% Iași fly ash [60]. Table 32 presents the values of non-admitted dosages for Iași fly ash. Table 30 presents the results of the internal friction angle and cohesion. Table 31 shows the tensile

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Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards strength of stabilized mixtures at 90, 180, 360 days. Table 33 presents Rc, Rtg for stabilized mixtures.

Table 30. The internal friction angle and cohesion Table 31. Tensile strength values Age Dosage Φ c Rti days % ° N/mm2 N/mm2 Dosage Rti adm 2 Age % N/mm 20 33 0.85 0.92 20 0.41 0.65 90 days 25 33 0.90 0.97 90 days 25 0.42 0.67 30 40 1.12 1.04 30 0.60 0.97 20 29 1.00 1.18 20 0.43 0.69 180 days 25 33 1.02 1.10 180 days 25 0.5 0.48 0.76 30 42 1.25 1.11 30 0.71 1.11 360 days 25 37 1.31 1.32 20 360 days 25 0.78 1.24 30

Table 32. Non-admitted dosages for Iași fly ash Age Dosage Iași fly ash mixture days % % 14 20 98.50 20 91.30 28 25 98.60

Table 33. Mechanical characteristics Rc and Rtg for stabilized mixtures Accelerated strengthening Age Dosage Normal strengthening +35°C +60°C Rc Rtg Rc Rtg Rc Rtg days % N/mm2 N/mm N/mm2 N/mm2 N/mm2 N/mm2 20 1.40 0.18 3.05 0.41 3 25 1.49 0.21 3.18 0.42 30 1.57 0.24 3.82 0.49 Admissibility conditions 20 2.08 0.21 3.54 0.57 Rc 7 25 2.12 0.23 3.87 0.58 foundation base Rtg 30 2.88 0.35 5.39 0.61 layer layer 20 1.28 0.17 14 25 1.42 0.19 0.70 1.30 30 1.76 0.23 20 2.01 0.27 28 25 2.17 0.29 1.20 2.20 30 2.82 0.34 20 3.00 0.40 60 25 3.16 0.42 30 4.56 0.43 20 3.24 0.49 90 25 3.33 0.52 30 4.83 0.53 20 3.43 0.58 180 25 3.91 0.59 30 5.65 0.70 20 360 25 6.22 0.75 30

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The first part of Table 33 shows the mechanical characteristics obtained by thermo-accelerated strengthening at temperature regimes of 35°C and 60°C. The concluding section of Table 33 expresses the experimental results obtained from specimens preserved in the moist atmosphere at 14, 28, 60, 90, 180 and 360 days. The objectives proposed in this study are to reduce the time required to establish optimum mixture and to establish correlations between mechanical properties and characteristics obtained by thermo- accelerated strengthening and the mechanic features obtained on pressed samples in the moist atmosphere (storage condition according to Romanian norms in force) [51]. The last columns of Table 33 show the admissibility conditions of Romanian regulations. They adopt 1,000 daN/cm2 for the deformation modulus. The difference between values associated with different mixture dosages at 35°C is significant for Rc in 7 days; the differences for Rtg are notable for both sample ages. In the case of 60°C temperature, the difference between dosages appears for Rc at both ages of samples.

Table 34. The Rc/ Rtg ratio for normal strengthening versus Rc, Rtg for accelerated strengthening

Rc and Rtg for accelerated strengthening Rc +35°C +60°C Rtg 3 days 7 days 3 days 7 days

Dosage Age wet Rc Rtg Rc Rtg Rc Rtg Rc Rtg 2 2 2 2 2 2 2 2 % days atm. N/mm N/mm N/mm N/mm N/mm N/mm N/mm N/mm Rc 0.91 1.63 > 2.00 > 2.00 14 Rtg 1.06 1.24 > 2.00 > 2.00 Rc 0.70 1.03 1.52 1.76 28 Rtg 0.67 0.78 1.52 > 2.00 Rc < 0.50 0.69 1.02 1.16 20 60 Rtg < 0.50 0.53 1.03 1.43 Rc < 0.50 0.64 0.94 1.09 90 Rtg < 0.50 < 0.50 0.84 1.16 Rc < 0.50 0.61 0.89 1.03 180 Rtg < 0.50 < 0.50 0.71 0.98 Rc 0.95 1.49 > 2.00 > 2.00 14 Rtg 1.10 1.21 > 2.00 > 2.00 Rc 0.69 0.98 1.47 1.78 28 Rtg 0.72 0.78 1.45 2.00 Rc < 0.50 0.67 1.01 1.22 60 Rtg 0.50 0.55 1.00 1.38 25 Rc < 0.50 0.64 0.95 1.16 90 Rtg < 0.50 < 0.50 0.95 1.12 Rc < 0.50 0.56 0.83 1.02 180 Rtg < 0.50 < 0.50 0.81 1.02 Rc < 0.50 < 0.50 0.61 0.74 360 Rtg 0.50 < 0.50 0.71 0.77 Rc 0.89 1.64 > 2.00 > 2.00 14 Rtg 1.04 1.52 > 2.00 > 2.00

Rc 0.56 1.02 1.35 1.91 28 Rtg 0.71 1.03 1.44 1.79 Rc < 0.50 0.63 0.84 1.18 30 60 Rtg 0.56 0.81 1.14 1.42

Rc < 0.50 0.60 0.79 1.12 90 Rtg < 0.50 0.56 0.78 0.97 Rc < 0.50 0.51 0.68 0.95

180 Rtg < 0.50 0.50 0.70 0.87

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The data analysis from Table 33 shows that de Rc admissibility conditions did not accomplish for realizing base layers, even for 20% fly ash dosage (Table 32). This condition is not relevant since the elasticity modulus is determined. It does not use a unique value for the deformation modulus as in the event of admissibility condition regulations. For the best compressive strength, 30% of fly ash mix with the natural ballast [245]. Table 34 presents the ratio between Rc and Rtg for standard strengthening versus Rc and Rtg for accelerated strengthening. If the values offer an improper fraction (the value of Rc is greater than the value of Rtg), the reports evaluate the mechanical characteristics. A difference of 25% to enhance the confidence level of resistance assessment justify the proper fractions (the value of Rc and the value of Rtg). The insurance of thermo-accelerated strengthening scheme at 35°C and 60°C allows obtaining a 90% confidence level for the significant mechanical characteristics as follows: Establishing, in the design stage, of the value for the deformation module of the material stabilized with fly ash from thermal plants; Obtaining the Rc and Rtg values at standard ages to confirm the fulfilment of quality conditions of road layers stabilized with fly ash from thermal plants [81]. The correlations established between Rc and Rtg in laboratories achieve the compression test only. The stereotype conditions determine the tensile strength by compression on a generator. The fatigue effect on bending tensile strength defines comparing Rtg1 and Rtg2 values corresponding to similar age samples. Rtg1 represents the bending tensile strength for control specimens, and Rti2 has the same meaning for samples previously subjected to fatigue [126]. The obtained fatigue curves show a behaviour corresponding to materials stabilized with Iași fly ash. The cost-effective usage of concrete with thermal ash appears from in-force norms and standards [329]. Also, its usage in building elements means an improvement [112]. It can replace up to 30% by mass of Portland cement [182] improving the final strength, chemical resistance and durability of the concrete. The spherical shape of fly ash particles increases the cement workability reducing water demand [181].

Fly ash properties are somewhat unique as an engineering material [24]. Unlike typical soils used for embankment construction [175], the fly ash has a large uniformity coefficient consisting of silt-sized particles [313]. Engineering properties affecting its usage in embankments [161] include grain size distribution, compaction characteristics, shear strength, compressibility, permeability, and frost susceptibility [13]. Mechanical performances, which the materials stabilized with pozzolana can reach, the economic efficiency and the environmental benefits [180], are redoubtable trumps for the challenge an official decision to resuscitate the interest of stakeholders (directors, producers and users) to maximize the use of pozzolana flash in road construction [13]. Correlations between mechanical strength achieved by accelerated thermal strengthening at 35°C and 60°C at 3 and 7 days respectively and mechanical strength under standard conditions of storage (wet atmosphere) determined at significant ages indicate the usefulness of that method. Correlations reduce the time needed to select the best recipes for pozzolana cement-type stabilization with fly ash from thermal power plants. Correlations between compressive strength and tensile strength limit the laboratory tests to a compression test only. It provides sufficient practical equipment that fit in every geotechnical laboratory. By the physicomechanical performances that fly ashes can achieve with a proper design in the laboratory stage and when the execution complies strictly the technology of the stabilized layers [175], they successfully replace the cement, with both economic and environmental benefits [42].

4.1.3. The compressive behaviour of aggregates cemented with fly ash collected from coal-fired power plants The experimental testing of mixes embedded 20%, 25% and 30% fly ash by weight of the total mixture collected from Iaşi and Vaslui coal-fired power plants. In road works, aggregates stabilized with 30% fly ash only fulfil the acceptability conditions to act as a base layer. Instead, the mixtures stabilized with 20%, and 25% of fly ash could use as sub-base layers. Natural pozzolana, also known as pozzolanic ash, is a porous variety of volcanic tuff or fine, sandy volcanic ash with burnt granules resembling powdered bricks. Since Antiquity, it acted as an activator in the “pozzolanic cement” considered the first cement in history. Pozzolana is a siliceous or siliceous-

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Ancuța Rotaru Habilitation Thesis aluminous material of rough, dusty, granular texture that quickly melts [53]. Added in the pozzolanic cement, it reduces the liability of leaching. However, its hydraulic cement-like underwater property, mixed with hydraulic lime (calcium hydroxide - Ca(OH)2) and water, is significant. It hardens quickly making it more durable underwater than any other cement. Currently, most of the mixed types of cement (CEM II) contain, apart from the principal component named the Portland clinker cement (65-79%) one additional element that can be either natural pozzolana or fly ash collected from a coal-fired power plant (21-35%) [341]. For instance, the modern cement that is also known as Portland-composite cement CEM II/B-M (V-LL) is a blend of natural/industrial fly ash (V) Portland cement and limestone (LL) which contributes to good strength, impermeability and workability [28]. For underwater use, the high alkalinity of pozzolana, due to sulfates, makes it resistant to the common forms of corrosion [4]. Once fully hardened, the Portland Pozzolana Cement (PPC) blend may be stronger than the Portland cement due to its lower porosity, making it more resistant to water absorption [76]; [149]. The current study investigates the compressive behaviour of aggregates stabilized with fly ash examining the potential of employing the fly ash – a residual product acquired by direct combustion of the lignite – as a cement substitute material for ground stabilization, mainly in roads and embankments completion works [48]; [318]; [357]. In Romania, 95% of lignite deposits concentrate in 250 square kilometres in the South-Eastern part of the country, namely the Oltenia mining basin. Here, more than 80% of lignite reserves are surface- mined in twelve opencast pits. Lignite reserves total up to 280 million tonnes with a further 10 billion tonnes of resources [102]. Romanian thermal power plants widely use lignite to gain more than 50% of the electric energy. One concern regarding its exploitation is the fly ash environmental impact from the lignite combustion through the retort residue process [124]. It is either stored inside the plant or laid out in landfills occupying significant land areas. That led to environmental and health concerns, which prompted laws to attenuate fly ash emissions [349]. Environmental protection measures aim to detect regions of efficient use of these wastes. It is the road engineering field that replaces standard materials with the fly ash [315]. Accordingly, a significant percentage of recycled fly ash uses to supplement Portland cement in the concrete manufacture process [191]. Aside from commercial advantages, there are environmental and technical benefits associated with fly ash usage as a binder in hydraulically bound mixtures [192]; [355]. Fly ash applicability as a cement- like material maintains the natural aggregate capacity and diminishes the greenhouse gas emissions [1]; [203]. Its self-hardening features offer benefits over granular materials in soil stabilization and hydraulically bound sub-bases [72]; [123]. Worldwide, the fly ash collected from thermal power plants extensively uses to road works [13] from local roads to highways on embankments, sub- base or base layers, dam performing and strengthening.

4.1.3.1. Materials The concept is to mix aggregates collected from North-Eastern Romanian sites along the Siret River with 20%, 25%, and 30% fly ash by weight of the total mixture. The fly ash results as a waste from the combustion of coal in Iaşi and Vaslui thermal power plants [73]. Fig.87. Grain size distribution curves of aggregates Next, compressive strength tests on

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Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards the mixtures go through. A comparison compressive strength of aggregates/fly ash mixtures from both Romanian thermal power plants performed [45]; [206].

4.1.3.1.1. Aggregates The Romanian North-Eastern area, particularly Iaşi and Vaslui counties, has limited resources of aggregates from quarries. The local ballast collected from the gravel pits along the Siret River at Paşcani and The Moldova River at Timişeşti is necessary for road construction and modernization [345]. Fig.87 shows the grain size distribution curves for both natural aggregates and partially crushed aggregates collected from the Siret River/Moldova River [344] as per SR EN 933-1:2012 [342]. Table 35 presents the characteristics of the natural aggregates utilized for stabilization. All the three types of natural aggregates comply with the Romanian Technical Instructions for the Execution of Road Layers from Natural Aggregates Stabilized with Pozzolanic Binders CD 127-2002 [62]. They are usable equally as sub-base layers and base layers in reinforcing the existing flexible road systems. However, for laboratory testing purposes and layer examination made from stabilized materials under accelerated traffic, the study utilizes natural or partially crushed aggregates from the Siret River only.

Table 35. Physical characteristics of natural aggregates Coefficient Sand Crushing Shape of equivalent index, Ic index uniformity (SR EN (SR EN (SR EN Type of aggregate U (SR EN 933-8+ 1097- 933-4:2008) ISO14688/2 A1:2015) 2:2010) [%] -2018) [%] [%] Natural aggregate from the Siret River 62 51 - - Partially crushed aggegate from the Siret River 60 55 80 20 Natural aggregate from the Moldova River 24 83 - -

The ballast collected from both sites is a quartzy sandstone having the following mineralogical composition determined by Röentgen analysis: quartz 95%, plagioclase feldspar 3-5% and trace elements like sericite (less than 1%), limonite, pyrite, magnetite, hornblende, and kaolinite [345].

4.1.3.1.2. The fly ash Fig.88 shows the grain-size distribution curves for fly ashes collected from Iași and Vaslui thermal power plants as per SR EN 933-1:2012 [343]. The grain-size of Vaslui fly ashes is smaller than that of Iași fly ashes. Table 36 shows the physical characteristics of the studied fly ashes.

Fig.88. Grain size distribution curves of fly Fig.89. Decreasing rate of compressive ashes collected from thermal power plants strength of aggregate mixtures stabilized with fly ash/ cement as per STAS 10473 / 1-86

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Table 36. Physical characteristics of fly ash Fly ash Characteristics Iași thermal Vaslui thermal power plant power plant Blaine specific surface area (SR EN 196-6:2010), [cm2/g] 3490 3800 Apparent specific gravity (SR EN 12697-6:2012) [g/cm3] 2.209 2.349 Bulk density [331]; [337] Loose state 0.735 0.819 (SR EN 1097-3:2002) [g/cm3] Dense state 0.947 0.958

Compaction characteristics acquired from the modified Proctor test [338]; [348] are as follows: 3 3 ρdmax =1.084 g/cm for the fly ash from Iași coal-fired power plant, and ρdmax =1.067 g/cm for the fly ash from Vaslui coal-fired power plant, while the optimum water content is the same for both types of fly ash, i.e. wopt = 35%. Oxic components of fly ashes from Iaşi and Vaslui coal-fired power plants meet the technical conditions of employment for material stabilization [90], [66] regarding the road works. These are aluminosilicate fly ashes with SiO2 / Al2O3 ˂ 2 and CaO% ˂ 15 showing hydraulic activity by activation with hydrated lime powder [46]; [53]. To establish optimal percentages in the laboratory and proper design of semi-rigid road systems, samples stay a maximum of 180 days in standard storage conditions [44]. That is a significant time of transition from mechanical to chemical stabilization.

4.1.3.2. Methods The experimental programme determines the compressive strength of samples kept in a humid atmosphere for 28 days as per SR EN 196-1:2016 [339]. The binder consists of 90% fly ash and 10% lime powder. Fly ash is active if the compressive strength of samples kept in a wet atmosphere 28 days reaches at least 5.5 MPa [15]. Fly ash specimens embed calcium hydroxide - one part, two parts fly ash and three parts monogranular sand. The amount of added water corresponds to the optimum water content [338]; [348]. The compaction test takes place in cylinders with 50 mm diameter and 100 mm height kept at +23ºC for 24 hours and at +55ºC for 6 days. Both sets of specimens containing fly ash from Iaşi and Vaslui sources mixed with 10% of lime powder accomplish the specification: Rc = 5.81 MPa for the mixture including fly ash from Iaşi coal-fired power plant and Rc = 5.52 MPa for the fly ash from Vaslui coal-fired power plant [330]. The aggregates have been mixed with a cement substitute material as follows: 1) fly ash from Iaşi thermal power plant (20%, 25%, and 30% by total mixture weight, respectively); 2) fly ash from Vaslui thermal power plant (20%, 25%, and 30% by total mixture weight, respectively). STAS 10473/2-1986 [35] controls the physical properties of mixtures using fly ash instead of cement [340]. To minimize the possible errors by taking the average value, three distinct sets of eight cylindrical specimens (Φ = 50 mm and h = 100 mm) of natural ballast stabilized with 20%, 25%, and 30% of fly ash, for each of the two sources, the thermal power plants of Iaşi and Vaslui, have been cast, then being preserved in a humid atmosphere as indicated in Table 37 [50]. Specimens tested as per STAS 10473/2-1986 [347] account a 25% decrease of compressive strength as the maximum admissive after 7 days of immersion (Fig.89) [275]. The maximum admitted values follow on the stipulations of the Romanian STAS 10473/2-86 [347] regarding the stabilized aggregates with cement.

Table 37. Test timeline Percentage No. of No. of No. of samples tested to Type of of fly ash samples kept samples to compressive strength, Rc, at aggregate in a wet determine different ages atmosphere the physical 14 28 60 90 180 properties day day day day day Natural ballast 20 52 12 8 8 8 8 8 stabilized with fly 25 52 12 8 8 8 8 8 ash from Iaşi power plant 30 52 12 8 8 8 8 8 Natural ballast 20 52 12 8 8 8 8 8 stabilized with fly 25 52 12 8 8 8 8 8 ash from Vaslui power plant 30 52 12 8 8 8 8 8 TOTAL 312 72 48 48 48 48 48

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As Fig.89 shows, after 7 days of immersion in water, the decreasing rate of the compressive strength for samples made of natural aggregates stabilized with fly ash was found lower than 25% compared to the characteristics of stabilized mixtures with cement as per the Romanian standard STAS 10473/2- 1986 [347]. As a result, the admissibility condition is satisfied [50]. The experimental results obtained by testing the samples of natural aggregates stabilized with different percentages of fly ash at the ages of 14, 28, 60, 90, and 180 days [275] are shown in Fig.90 and Fig.91. Romanian Standard CD 127-2002 [62], the admissibility conditions for the compressive strength in 14 and 28 days limit the fly ash usage to sub-base and base layers (Table 40). Both absorption and swelling in stabilized mixtures [125] lead to a decreased fly ash percentage in base layers [46].

4.1.3.3. Results

Fig.90. Compressive strength values for Fig.91. Compressive strength values for aggregates stabilized with Iaşi fly ash aggregates stabilized with Vaslui fly ash

The compressive strength admissibility conditions at 14 days are unaccomplished for the mix embedding 20% of fly ash from Iaşi thermal power plant used as a base layer. Either 20%, 25% or 30% addition of fly ash accomplishes the admissibility conditions for the compressive strength at 28 days if the mixture uses as a sub-base layer (Fig.90, Table 38) [3].

Table 38. Compressive strength for Table 39. Compressive strength for mixtures mixtures of aggregate-fly ash from Iaşi of aggregate-fly ash from Vaslui thermal thermal power plant power plant

Compressive strength [MPa] Compressive strength Age Age 20% fly 25% fly 30% fly 20% fly 25% fly 30% fly [days] [days] ash ash ash ash ash ash

14 1.28 1.42 1.76 14 1.54 1.61 1.76

8 2.01 2.17 2.17 28 1.88 2.04 2.20 60 3.00 3.16 2.82 60 2.45 2.75 2.79 90 3.24 3.33 4.56 90 3.06 3.15 3.21 180 3.43 3.81 4.83 180 3.64 3.74 3.99

Similarly, adding 20% fly ash from Vaslui thermal power plant does not fulfil the admissibility conditions for compressive strength at 28 days. These requirements are unsatisfied if the mix is designed as a base even when using a percentage of 25% fly ash from the same thermal power plant. If the binder uses as a sub-base layer, any 20% to 30% fly ash added accomplishes the admissibility conditions for compressive strength at 28 days (Fig.91, Table 39). Consequently, natural aggregates stabilized with 30% of fly ash from both Iaşi and Vaslui thermal power plants used as base layers fulfil the compressive strength admissibility conditions. Generalizing,

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Ancuța Rotaru Habilitation Thesis the mixture of aggregates stabilized with 30% of pozzolanic fly ash collected from thermal power plants successfully uses as a base layer for road works. Other mixes of aggregates stabilized with less than 30% of fly ash can use as sub-base layers for road construction works.

Table 40. Admissibility conditions RO Standard admissibility conditions

Binder age Rc [MPa]

[days] Sub-base layer Base layer

14 0.70 1.30 28 1.20 2.20

Construction industry needs materials belonging to the modern era to meet the resistance, safety and environment-friendly demands. Experimental results confirm the possibility of using the fly ash waste in road building works as a cement-like compound of stabilized mixtures of natural aggregates used as sub-base layers. Under these conditions, the fly ash does not compromise the structural integrity. Using the fly ash as a cement-like material is encouraging, mainly because it minimizes the environmental impact of the output of solid waste resulted from the coal combustion in thermal power plants. The results achieved on natural aggregates stabilized with 30% of fly ash from thermal power plants are optimum. They allow the mixture in road building works either as sub-base layers or base layers.

4.1.4. The bituminous oil shale ash influence on stabilized silty-sandy brown clay

The western part of Amman, the capital of Jordan, holds 4 to 5 meters in the depth of brown clay that exhibits plasticity, swelling, settlements and low shear resistance. Also, south Jordan contains vast deposits of bituminous oil shale that extend to considerable depths. The government of Jordan decided to use the bituminous oil shale for power generation and oil production as massive amounts of ash resulted. The current research evaluates the effect of bituminous oil shale ash rich in lime on the silty- sandy brown clay that spreads on substantial areas in middle and northern Jordan [2]. The ash mixed with brown clay in distinct percentages and some geotechnical constants of the resulted mixtures have been measured and analysed. The bituminous oil shale ash exerts a significant effect on lowering the plasticity index of the mix. It decreases its dry unit weight and increases its compressive strength and permeability to a certain percentage. Besides, the binder produces a beneficial effect, reducing the compression index (Cc) and swelling index (Cs) of brown silty-sandy clays. To quickly facilitate the increase of vehicles weight and traffic, the new pavement design/reconstruction calls for relatively low-cost solutions like materials with moderate engineering characteristics [191]; [315]. The soil stabilisation method by treating natural soils and aggregates with additives to achieve properties assigning the appropriate standard specifications is the most employed technique. It aims to increase the physical and mechanical properties of soils [48]; [73]; [349]. The study investigates the effect of oil shale ash stabilisation on the expansive silty-sandy brown clay from the Madaba area near Amman City. The term oil shale refers to Jordanian lithologic bituminous limestones and marls. The Jordanian oil- shale deposits are marinites from Late Cretaceous (Maastrichtian) to Early Tertiary. At that time, Jordan was closed to the southern margin of Neo-Tethys Ocean. The sedimentation occurred on a vast shallow shelf triggering a thick sequence of chalks, marls and limestones over the northern and central Jordanian areas. Jordanian oil shale is usually brown, grey or black weathering to a distinctive light bluish-grey. It consists of unconsolidated gravel and silt with stringers of marlstone, limestone and basalt in isolated areas. There are 26 known Jordanian deposits of oil shale totalling over 4 billion tonnes. The more significant eight are in the marine Chalk-Marl unit, 20 to 75 km east of the Dead Sea (Fig.92). Phosphatic limestone and chert of the Phosphorite unit underlay them [2]. As about 80 billion tons exist in the southern part of the country, the Jordanian government decided to burn the bituminous limestone for power production purposes. This process generated massive amounts of fly ash. This waste possesses complex characteristics so that its management is complex. The distribution and storage of oil shale ashes without treatment leads to surface and groundwater contamination and disturbs the environmental balance [355]. Discovering techniques to use the bituminous oil shale ash to several

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geotechnical purposes would produce a significant environmental impact. The solution may rise by oil shale ash utilisation as a building material in civil engineering and infrastructural projects. Several research scientists have reported the fly ash influence on soil properties. Soils near Amman City are nodules of soft calcium carbonate inserted in the brown silty clay that broke up the Cretaceous bedrock. The upper 2m layer consists of soft to stiff fissured silty clay dark to greyish brown with pebbles, cobbles and boulders of chert and limestone with high shrinkage and swelling characteristics causing severe damage to civil engineering structures. Their geotechnical properties predict the effect of oil shale ash on the mixture. Expansive brown silty-sandy clays derived mainly from marl, limestone and chert bedrocks formed during the Cretaceous Age, spread over 40% of the area located in the central part of the country, in the vicinity of west Amman City [2]. Fig.92. Map of oil shale deposits This clay is a problematic soil as it exhibits excessive differential in Jordan, locations after Jaber settlements and deformations. The swelling and shrinkage and others, 1997; and Hamarneh, potential affected it by mineralogical constituents and 1998 (after the reprint of: United surrounding environment induces building cracks. The smectite, States Geological Survey which is the main component of the sandy-silty brown clay [8], Scientific Investigations Report is responsible for the volume change and shear failure. A while 2005-5294 by John R. Dyni) back, it was the lime that helped the soil to stabilise. It improved plasticity behaviour increasing the workability of soil. Although the hydrated lime proved safe, effective, and easy to mix with water [2], mixing fly ash with expansive clay can improve the product properties [44] in respect with:  A good effect on the plasticity and compressibility of the expansive soil determined by the compression index (Cc), which describes the void ratio variation according to effective stresses and by the rich content of lime in the fly ash [275].  A decrease in permeability with the increase in the ash content [2]. The calcium content is different for various types of fly ash, and even though much of ashes has particular effects on the treated soil, there is no ash able to improve all physical and mechanical properties of soil. The optimal percentage of the fly ash is still unclear even though extensive research on the effect of the fly ash on compressibility developed. The objective is to use well-defined rates by weight of bituminous oil shale ash to improve the silty-sandy brown clay, mainly in pavement foundations controlling its compressibility, permeability and compressive strength [206]. Oil shale is the most abundant fossil energy resource discovered in Jordan. Jordan is ranked immediately after the USA and Brazil in oil shale reserves, huge and sufficient to satisfy the national energy needs for hundreds of years. The burnt oil shale produces ash that usually can use as additives for cement and other building Fig.93. Location of silty-sandy brown clay after materials [2]. However, it is well-known that “Al-lajjun Oil Shale Project” – Jordan Energy and some ashes can stabilise clays. Expansive brown Mining Limited silty-sandy clays near Amman City induce differential settlements and deformations producing cracks in building elements. The study abstracts results on the optimum percentage of oil shale ash used to improve the stabilisation process of brown clays in Jordan reducing the residual deposits of ash and the cost of cement-like materials for a safe built environment.

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4.1.4.1. Materials 4.1.4.1.1. Bituminous oil shale ash

Fig.94. Testing procedure

The bituminous limestone from the surface/near-surface deposits of Al-lajjun in South Karak City, the Jordanian most extensively explored yard (Fig.93), burnt at 950° C in the laboratories of the American University of Madaba, Jordan. The chemical components of the by-product are given in Table 41. Outcomes show (Fig.94) that the resulted ash contains considerable amounts of lime, calcium oxide, and many pozzolanic materials such as silica and iron oxide with an apparent specific gravity of 2.70 g/cm3. The main mineral components of the El Lajjun oil shale are calcite, quartz, kaolinite, apatite. In small amounts, there are feldspar, illite, dolomite, goethite, pyrite and gypsum. The sulfur content of Jordanian oil shale usually ranges from 0.3 to 4.3 per cent, but the percentage was higher on the site. Regarding the specific surface area for ash: Initially, the surface area of oil shale ash combusted at 550°C increased about 2.5 times compared to the raw oil shale sample; from 12 m2/g to 29 m2/g. The opening of new pores due to devolatilisation combustion of organic matter explains that. A further increase of combustion temperature to 950°C results in a decrease of the surface area below the raw sample values. It demonstrates that the sintering of oil shale ash started beyond 600°C, providing a significant reduction in the surface area over this temperature (7 m2/g) [2].

Table 41. Chemical composition of the bituminous oil shale ash Oxide SiO2 Fe2O3 Al2O3 CaO K2O MgO P2O5 SO3 Percentage [%] 32 3.15 1.45 46.3 1.47 2.46 5.62 5.78

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4.1.4.1.2. Brown clay Disturbed samples of silty- Table 42. Physical properties of unstabilized silty-sandy brown sandy brown clays were sampled clay from a shallow borehole of 1 m depth near the American Parameter Value University of Madaba, 30 km Liquid limit [%] 56 south of Amman City (Fig.93). Plastic limit [%] 32 Plasticity index [%] 24 Samples got ready in the 3 University’s lab for testing the Max. compacted dry density [kN/m ] 15.1 Clay fraction [%] 22 main physical and mechanical Apparent specific gravity [g/cm3] 2.61 properties and the effect of oil Sample classification (USCS) CL shale ash stabilizer on these properties. Table 42 shows physical properties of unstabilized silty-sandy brown clay.

4.1.4.2. Methods The purpose of the bituminous oil shale ash addition to brown silty-sandy clay (5%, 10%, 15%, 20%) is to identify geotechnical properties of the mixture. The plasticity index reduces and permeability increases. Tests went through to work on the geotechnical properties of the brown silty-sandy clay.

4.1.4.2.1. The grain-size distribution curve The grain-size distribution curve resulted after conducting the sieve analysis test of the silty- sandy brown clay according to ASTM C136/C136M-14 [2], as shown in Fig.95.

Fig.95. Grain-size distribution curve of the silty-sandy brown clay

4.1.4.2.2. Atterberg Limits For soil plasticity determination of the clay sample passing sieve #40 mixed with different percentages of fly ash, liquid limit (LL) and plastic limit (PL) tests went through. The Casagrande test determines the liquid limit, while the hand- rolling technique determines the plastic limit. Both tests use Fig.96. Plasticity index variation distilled water. The Plasticity Index (PI) of the brown clay is at different ash percentages 25%. Hence, the difference between the liquid limit and the plastic limit is equal to 15%. Fig.96 shows a 7% decrease in the plasticity index at 20% added oil shale ash. That is because of liquid limit reduction and a slight increase in the plastic limit.

4.1.4.2.3. Compaction test Standard Proctor compaction tests set up the maximum dry density (MDD) and optimum moisture content (OMC) of brown silty-clay and brown silty-clay mixed with oil shale ash (5%, 10%, 15% and 20%, respectively). The additive content as a percentage defines by the ratio of the additive dry weight to the clayey soil dry weight. Samples having the same per cent of oil shale ash were repeatedly used (remoulded) for compaction at different moisture content. The material thoroughly combined achieved uniform mixing before compacting in the mould and tests carried out using the equipment and procedure

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as the ASTM D698 specifies for Proctor test [2]. The uniform stabilized soil mixture was transferred to a cylindrical mould and compacted in three similar layers. Fig.97 a-e illustrate typical compaction curves. Table 43 presents results on compaction tests. The increasing fly ash content upon the coefficient of consolidation, compression index, permeability and pre-consolidation pressure was also investigated.

4.1.4.2.4. Permeability test Five samples got ready by compacting the clay/clay with oil shale ash in the Proctor standard mould at the maximum density and optimum moisture content. They were curred inside a tight plastic bag for one week before subjected to a falling head permeability test. Fig.98 illustrates the overall results of the test. Even though the plasticity index increases with the oil shale ash percentage, the study analyses the allowable value of the Fig.97a. Compaction curve for permeability coefficient kall for sandy clays of low plasticity the brown clay (CL).

Fig.97.b. Compaction curve for Fig.97.c. Compaction curve for Fig.97.d. Compaction curve brown clay - 5% oil shale ash brown clay - 10% oil shale ash for brown clay - 10% oil shale ash

It is 5 x 10-8 m/s, similarly to thebrown initial clay brown - 10% sandyoil shale-clay. ash Consequently, 15% of oil shale ash is acceptable. The mixture ranges in the Moderate/Slow zone (Fig.99) like the initial brown sandy-clay with the permeability coefficient k smaller than kall. However, specific conditions for some engineering problems frequently need to be considered for an appropriate choice of geotechnical constants.

4.1.4.2.5. Unconfined compression test Samples of brown clay mixed with distinct percentages of oil shale ash firmed in a small mould at the maximum dry density and optimum moisture content. They were prepared in the laboratory and self-cured in tight plastic bags for 7 and 21 days. The samples sizes were 100mm in length and 50mm in Fig.97.e. Compaction curve for diameter. The results are illustrated in Fig. 100 (a, b).

brown clay with 20% oil shale ash brown clay - 10% oil shale ash

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Fig.98. Permeability of brown clay mixed with Fig.99. Classification of permeability different percentages of oil shale ash coefficient

Fig.100.a Unconfined compressive strength of Fig.100.b Unconfined compressive strength of the brown clay mixed with oil shale ash at 7 days the brown clay mixed with oil shale ash at 21 days

Table 43. Maximum dry unit weight/optimum moisture content, brown clay - different oil shale ash % Sample Maximum Dry Unit Weight Optimum Moisture Content [kN/m3] [%] Brown clay 15.1 26 Brown clay with 5% oil shale ash 14.7 28 Brown clay with 10% oil shale ash 14.3 31 Brown clay with 15% oil shale ash 14.1 33 Brown clay with 20% oil shale ash 13.8 34

4.1.4.2.6. Consolidation test Several one-dimensional consolidation tests performed according to ASTM D2435/ D2435M [2] provisions examine the effect of oil shale ash on the brown clay. Samples of brown clay/brown clay with oil shale ash (5%-20% by weight) got ready. The clay was disturbed, and all specimens passed the sieve #100. All the saturated samples were subjected to effective stress of 50 kPa up to 800 kPa, immediately followed by the unloading process for two consecutive readings. Fig.101 b-e show test results, while Table 44 communicates the summarized results of the consolidation test. Fig.101.a shows the consolidation behaviour of the brown clay without any addition of oil shale

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ash. Table 4 shows a compression index (Cc) of 0.233 and a swelling index (Cs) of 0.014 for the brown clay. Adding the bituminous oil shale ash as a self-cementing material to the brown clay creates a calcination process from the beginning of the consolidation test. At the onset of the compression stage, its effect was reduced but still noticeable. After 2-3 days, the calcination effect reduced the swelling pressure. That indicates that the clay lost much of its plasticity due to the bituminous oil shale ash.

4.1.4.3. Results The plasticity index decreases from 25% (brown clay) to 18% (mix of 20% oil shale ash). A 10% to 20% plasticity index indicates a Fig.101.a. Consolidation curve of clay without medium plastic behaviour of the soil. A bituminous oil shale ash plasticity index less than 20% shows the soil needs stabilisation with cement or environmentally-friendly substitute like oil shale ash. The compaction test shows that the increase of oil shale ash content in mixtures leads to a dry density decrease due to the oil shale ash reduced specific gravity. The addition of oil shale ash results in a maximum dry unit weight decrease (γdmax) and an increase of the optimum moisture content (OMC) of mixtures. That occurs because the oil shale ash extensive surface absorbs much water, while its density is less than that of the brown clay. Another reason might be the flocculation of oil shale ash particles and brown clay particles. Table 3 shows that percentages of 15-20% of oil shale ash added in the brown sandy-clay represent the optimum values to minimise the plasticity index and the swelling potential. The compaction test shows that the consistency limits, compaction characteristics and swelling potential of expansive clay–oil shale ash mixtures are significantly modified and improved. A mix of brown clay with 15-20% oil shale ash improves binder plasticity. The oil shale ashes exhibit low dry unit weight compared to the brown clay. The key objective is to reveal the effect of oil shale ashes on physical, compaction and swelling potential of brown clays and encourage its utilisation. The permeability analysis shows a slight increase in the permeability coefficient for low oil shale contents. A noticeable increase in the permeability coefficient occurs for 15% and 20% of oil shale ash content to a maximum value of 5.1 x 10-8 m/s. The permeability index of the brown clay represents only 2.07 x 10-8 m/s.

Fig.101.b. Consolidation curve of clay with 5% Fig.101.c. Consolidation curve of clay with 10% ash ash

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Fig.101.d. Consolidation curve of clay with 15% Fig.101.e. Consolidation curve of clay with 20% ash ash

Table 44. Compression index and swelling index of brown clay with different oil shale ash percentage Sample/ Probă Compression Index (Cc) Swelling Index (Cs) Brown clay 0.233 0.014 Brown clay with 5% oil shale ash 0.171 0.010 Brown clay with 10% oil shale ash 0.142 0.007 Brown clay with 15% oil shale ash 0.131 0.0031 Brown clay with 20% oil shale ash 0.122 0.0014

The samples subjected to the unconfined compression test show quite similar behaviour for distinct percentages of oil shale ash. The compressive strength reaches 146 kPa for specimens with 20% of oil shale ash curred for 7 days and 151 kPa curred for 21 days. Adding the oil shale in specific percentages is proved to decrease the Compression (Cc) and Swelling (Cs) indices. A sharp decrease in the Compression and Swelling indices appears at 10% of clays mixed with oil shales. After that, decreasing is negligible. This behaviour is primarily due to the high calcium content of the oil shale resulting in more cementitious material in clay.

Conclusively, soil stabilisation as a cost-effective method uses to property improvement of weak foundation soils adding binders and by-products. Experimental results confirm the availability of bituminous oil shale ash to enhance the geotechnical properties of brown clay. It reduces the environmental impact of solid waste resulted from the combustion of bituminous oil shale. Extensive experimental work studied the effect of the bituminous oil ash addition on the geotechnical behaviour of silty-sandy brown clay from Jordan. Based on test results and due to the oil shale ash nature and its high lime content, the following conclusions arise: 1. The bituminous oil shale ash is more effective due to the rich lime content compared to other ashes. 2. Various percentages of oil shale ash use to prepare the brown clay-bituminous oil shale ash mixtures. Along with the increase in bituminous oil shale ash percentages in brown clay specimens, the optimum moisture content increases and the maximum dry density decreases. 3. The brown clay mixed with bituminous oil shale ash shows a gradual reduction of the maximum dry density indicating an increased resistance to compaction due to the flocculated structure. The optimum moisture content increasing derives from the water embedded in the flocculated soil structure. 4. The plasticity index of the clay sharply decreased by adding the oil shale ash. 5. The permeability coefficient of the clay increased proportionally with the ash percentage. 6. The highest strength values for the stabilised brown clay with bituminous oil shale ash are associated with the moisture content. Both maximum compressive strength and maximum dry density occurred at specimen compaction with the optimum moisture content. 7. The addition of oil shale can noticeably reduce both compression and swelling indices. 8. The compaction of the brown clay with oil shale ash additive places the mixture in areas of reduced densities and higher moistures than those of the untreated soil. After adding different percentages of oil

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Ancuța Rotaru Habilitation Thesis shale ash, the compaction characteristics are only slightly modified. 9. Adding oil shale ash ranging from 5% to 20%, the maximum dry density of mixtures is smaller than initially. Graphs show that bituminous oil shale ash contents higher than 10% produce an insignificant effect on the maximum dry density. 10. The unconfined compressive strength is proportional to the amount of oil shale ash. Based on these findings, 10-15% of bituminous oil shale ash mixed with bituminous brown clay could act as an effective agent to improve the swelling of the brown clay. It also has the benefit of reducing the negative impact on the environment by reducing the landfill of an industrial by-product like the bituminous oil shale ash.

4.2. Properties of the concrete with waste replacements 4.2.1. Mechanical properties of polymer concrete with waste replacements The study analyses the influence of wastes as component of polymer concrete on the mechanical properties. Five types of wastes were used for preparing epoxy resin concrete: fly ash, sun flower, corn, saw dust, polystyrene granules and chopped plastic bottles. Fly ash was used as filler in all mixes. The other wastes were used as aggregate substitution with a percentage of 25% of the weight. The mechanical properties such as: compressive strength, flexural strength and split tensile strength were experimentally determined and compared with a control mix prepared with epoxy resin and aggregates. Generally the values of compressive strength were smaller than those of the control mix. The flexural strengths developed bigger values than the control mix for all types of wastes. The split strength presented higher values than control mix only for concrete with saw dust. The minimum values of mechanical strengths were obtained for concrete with corn cob as aggregate substitution. The density of polymer concrete with wastes generally corresponded to lightweight concrete. The accumulation of unmanaged wastes from the food industry, particularly in developing countries becomes problematic. New applications for such waste comprise the creation of environmentally friendly concretes and composites in the road-building and construction industries, for instance [30]. In the entire world, the construction industry is rapidly developing and a significant objective for the building industry in the forthcoming years is to use sustainable materials which conserve natural resources. This is particularly pertinent given the rising cost and chronic shortages of conventional materials. Wastes, a problem for the environment, are of great interest in the manufacture of green construction materials [55]; [91]; [103]; [322]. Waste materials such as plastics and glass, which present possible environmental hazards, are landfilled and often used in concrete for different applications. Fly ash, silica fume, ground granulated blast furnace, used tire, plastic bottles, wastes of glass, polystyrene, wood, agro-wastes, sludge, etc. are studied as components of concretes and mortar for ecological reasons but also for improving their properties [10]; [39]; [69]; [145]; [151]; [190]; [197]; [221]; [222]; [356]. It has been shown that the properties of these materials are suitable to produce new concrete up to a certain limit. Using wastes in a high-performance concrete is an accepted practice, yet they are also usable in geopolymers and polymer concrete production. Wastes - such as fly ash, slag, etc. help to replace the cement [324] in geopolymer composition while polymer concrete includes resin and aggregates. Wastes behave as fillers or replace resin or aggregates [33]; [236]. The use of those wastes in specific applications may solve two problems, namely, elimination of an environmental pollutant and provision of an alternative material for the construction industry, namely, the lightweight concrete. In 1971, The One Shell Plaza, Texas, a 52-storey building, broke the record as the world's tallest building made of lightweight concrete. Nowadays, this record has been surpassed by Renzo Piano's The Shard, a 300 metre-high 95-storey supertall tower topped out in London in 2012. Suspended floors have been benefiting from lightweight concrete for years, as it reduces the weight on the structure and increases fire resistance. Because lightweight concrete is typically thinner is made of different ingredients than traditional concrete, floors can be up to 45% lighter than regular concrete floors [359]. However, lightweight concrete costs more to produce. Replacing 25% by volume of its mineral agregates with lightweight waste aggregates could offer benefits to contractors. On this account, this study discusses some properties of the concrete using five types of light wastes as aggregates. The addition of such materials can significantly affect the concrete properties, in some instances altering its strength, density and water resistance. The analysis of the effects of the analysed wastes on polymer concrete reveals differences in physical and mechanical characteristics of the lightweight concrete.

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4.2.1.1. Materials The study uses polymer concrete, fly ash and five types of wastes. Control polymer concrete. The experimental study uses a control polymer concrete composed of epoxy resin and two sorts of aggregates. The polymer concrete uses polymers to replace lime-type of cement as a binder. The epoxy resin is type ROPOXID, made in Romania by POLICOLOR Bucharest. The resin represents 12.4% of the mixture weight for all types of polymer concrete. The hardener is type ROMANID 407, also made by POLICOLOR Bucharest. Natural aggregates consist of 0-4 mm sand and 4-8 mm gravel, with continuous granulometry according to Romanian standard [334]. In the control mix, both aggregates have a 43.8% dosage from the mix weight. The control mix is marked as C0. Fly ash. Fly ash from Iași Power Plant is a cement-like filler having 12.8% dosage from the mix weight [275]; [276]. Fly ash properties are: dark grey, spherical particles of sizes ranging from 0.01 μm to 400 μm, specific area 480-520 m2/kg, density 2400-2550 kg/m3, chemical components Si (18.3%), C (17.15%), Al (13.9%), etc. [275]; [276]. Fly ashes compose all mixes with waste substitution, in the same dosage. The wastes are as follows:  Sunflower wastes substitute 25% of fine mineral aggregate by volume, sand sort 0-4 mm. Sunflower aggregate preparation consists of cutting the stem of the dried plant in pieces with sizes smaller than 4 mm. The small pieces dried out in a natural ventilated room at 25°C. The sunflower waste density experimentally determined is 136 kg/m3. The polymer concrete with sunflower is marked as C1. For compressive strength, specimens were cube moulds with sides of 100 mm, 100x100x500 mm prism moulds for the flexural tensile, and cylinders of 100mm Ø× 200mm for the split tensile strength test, three samples prepared for each test. Tests come after 28 days of curing, as per Romanian standards [332]; [333]; [335]; [336].  Corn wastes use as a substitution by volume of 25% of fine aggregate, sort 0-4 mm. The preparation of the corn cob aggregate consists of cutting the dried cob in pieces with sizes between 0-4 mm. The experimentally determined density of the corn cob waste is 266 kg/m3. The polymer concrete with corn waste is marked as C2.  Sawdust uses as a substitution of 25% by volume of fine aggregate, sort 0-4 mm. It is a residue from the wood industry. The density of sawdust waste experimentally determined is 168 kg/m3. The polymer concrete with sawdust is marked as C3.  Polystyrene (PS) granules substitute 25% by volume of fine aggregates, sort 0-4 mm. The polystyrene granules are wastes from the construction industry. The density of polystyrene waste experimentally determined is 1.6 kg/m3. The polymer concrete with PS is marked as C4.  Chopped plastic bottles (PET) use as substitution of 25% by volume of fine aggregate, sort 0-4 mm. Waste plastics are a threat to the global environment so that recycling may be a solution. Only a quantity of about 25% of plastic waste is recycled around the world, while 75% frequently find the way into rivers, oceans, coast, beaches, and the land. The percentage of recycled plastic can increase by transforming waste plastic into products suitable for construction materials. The plastic waste may consist of mixed organic (food remains) and inorganic (attached paper labels) fractions. Its utilization as an aggregate in concrete for the construction industry could be an efficient solution as long as the contamination of plastic waste has not considerable impact on its properties. Resin-based types of waste plastic like polystyrene (PS) and PET have the highest rate of usage for concrete production [145]. PET is a sub-product got from plastic bottles recycling process. The processing of PET supposes to crush the plastic to a size between 1.18 mm and 4.75 mm, with angular shape. The density of the PET waste experimentally determined is of 433 kg/m3. The polymer concrete with PET is marked as C5.

4.2.1.2. Experimental procedure For preparing polymer concrete, the components were mixed; firstly, the dried components and after that, the epoxy resin combined with hardener was added. Sample types: cubes of 7 mm sizes and prisms of 70x70x210 mm were poured. After 24 hours, samples were demoulded and kept at a temperature of 200 C for 14 days. The density of hardened polymer concrete was determined [336]. The cubes were tested to axial compression for determining the compressive strength [275], the prisms were tested in flexure and splitting for determining the flexural

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Ancuța Rotaru Habilitation Thesis strength and split tensile strength according to standards [322]; [276]. All tested were done on three samples for each type of concrete.

4.2.1.3. Results The experimental results are compared in the graph presented in Fig.102. The experimental results on polymer concrete with wastes are given in Table 45.

Table 45. Experimental results on polymer concrete with different types of wastes Sample fc fti ftd Density, [MPa] [MPa] [MPa] [kg/m3] 0 69.93 12.26 6.82 2116 C1 39.30 16.30 6.63 2027 C2 28.96 13.61 5.15 1973 C3 56.60 16.59 6.98 1919 C4 44.59 14.84 5.28 1861 C5 47.21 16.94 6.14 1946

4.2.1.3.1. Compressive strength Fig.1 shows that the values of compressive strength varied from 56.6 MPa for polymer concrete with corn as aggregate substitution to 28.96 MPa for concrete with saw dust as aggregate substitution. All values of fc were smaller than that of control mix with percentages between 19.1% for C3 and 58.6% for C2. For the same aggregate substitution, the wastes influenced differently the compressive strength. All values of fc indicate that the studied polymer concrete with wastes can be used for structural applications.

4.2.1.3.2. Flexural strength Experimental results shows that the values of flexural strengths for all mixes with wastes were bigger than that of the control mix with percentages between 38.2% and 11.1%. The maximum flexural strength was obtained for concrete C5 and the minimum value for C2.

4.2.1.3.3. Split tensile strength Fig.1 shows that the values of split tensile strength for mixes with wastes were smaller than that of the control mix, except for the C3 mix for which a small increase of the strength was obtained. The values of fti varied between 6.98 MPa for C3 and 5.15 MPa for the C2 mix, that means an increase of 2.3% for C3 and a maximum decrease of 24.5% for C2.

Conclusively, the density for hardened concrete is given in Table 1. The type of waste influenced differently the density. All densities of polymer concrete with waste were lower than those of the control mix. For C2, C3, C4 and C5 mixes, the densities were lower than 2,000 kg/m3. That indicates that these are lightweight concretes. The minimum density was obtained for the C4 mix, for which mechanical strengths presented relatively higher values. C4 can be considered as a lightweight concrete that can be used for structural applications. Generally, the polymer concrete with aggregate substitution of agro-wastes presented smaller values of mechanical strengths in comparison to that for other types of wastes, for the same dosage of substitution. Densities in case of agro-wastes were bigger than those got with other types of wastes. For each mechanical strength, the maximum value was obtained for different mix. The type of waste influenced differently each mechanical property. Only in the case of mix C3, the maximum value was obtained for fc and ftd. In the case of minimum value of mechanical strengths, these were obtained for the same mix prepared with corn cob. For the same aggregate substitution, wastes influenced differently mechanical strengths [358]. The density was smaller than that of the control mix for all types of wastes. Concretes with corn waste, sawdust, polystyrene granules and chopped PET are lightweight polymer concretes [127]. The values of compressive strength of the concrete reported a decrease compared to those of the control mix for all types of wastes. The higher value of compressive strength was obtained for the mix with sawdust aggregate substitution. For all mixes, the flexural strengths were bigger than those of the control mix. The higher value of flexural strength was obtained for the mix with chopped PET aggregate

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Eco-friendly Materials for Sustainable Rehabilitation of Substructure Works Affected by Hazards substitution. The split tensile strengths were generally smaller than those of control mix; only the mix with sawdust presented a higher value than that of the control mix.

80 69.93 70 60 56.6 50 47.21 44.59 39.3 40 fc, MPa 28.96 30 fti, MPa 14.84 20 16.3 16.59 16.94 ftd, MPa 12.26 13.61

Strengths variation,MPa 6.14 10 6.82 6.63 5.15 6.98 5.28 0 C0 C1 C2 C3 C4 C5 Polymer Concrete Mixes

Fig.102. Variation of mechanical properties of fly ash polymer concrete with different wastes

Mechanical strengths of polymer concrete with different types of wastes as aggregate substitution are not very much diminished in comparison to those of polymer concrete without wastes, especially in case of tensile strengths, where wastes improve the flexure behaviour. The polymer concrete presentes some special characteristics [31]:  mechanical properties are comparable to those of structural concretes;  higher flexural strength can control polymer concrete;  densities were closed to those of the lightweight concrete. Different types of wastes can be used in the mix of polymer concrete contributing to waste consuming and applying new eco-materials in the construction industry.

4.2.2. Mechanical features of lightweight concretes by aggregate replacement The study presents experimental results on lightweight concrete prepared by replacing the aggregates with waste of sawdust in different dosages. The concrete was prepared with cement, fly ash and aggregates in three sorts and sawdust waste. The aggregates 0-4 mm were replaced by waste in dosages between 40% and 100%. The density of hardened concrete and mechanical properties such as compressive strength, flexural strength and split tensile strength were experimentally determined and discussed. The densities of all mixes were under 2000 kg/m3. The density and mechanical properties are decreasing when the waste dosage is increasing. In the last years, researchers are interested in obtaining sustainable products to protect the environment and take care of natural resources. In this direction, to consume wastes of any type and replace the raw material usage with sub/by-products from industry is required [55]; [106]; [378]. In the construction industry, the waste usage leads to modern concretes and mortars, precast elements, infrastructure, bridges, repairs and consolidations [122]; [139]; [151]. In the concrete industry, modern concrete types like high-strength concrete, polymer concrete, lightweight concrete, self-compacted concrete developed [5]; [152]; [221]; [350]. Using lightweight aggregates (natural or industrial products) or replacing the natural aggregates with different materials (polystyrene grains, sawdust) the lightweight concrete is obtained [320]; [363]; [377].

4.2.2.1. Materials The dosages of component materials of the lightweight concrete were the composite cement type CEM II 42.5 in a dosage of 324 kg/m3, aggregate sort I (sand) in a dosage of 803 kg/m3, aggregate sort II of 4-8 mm in a dosage of 384 kg/m3 and sort III of 8-16 mm in a dosage of 559 kg/m3. The water was in a

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Ancuța Rotaru Habilitation Thesis dosage of 172 l/m3, and the superplasticizer type GLENIUM-BASF was 1% from the cement dosage. The fly ash in a quantity of 10% from the cement adds to the mix. Replacing the aggregate sort I in dosages of 40%, 60%, 80%, 100% with sawdust (marked S1 to S4) prepares the experimental mixes. Sawdust graded 0-4 mm in sizes is a waste from the wood industry. Initially, the compositions were prepared by moistening the sawdust in water for a few minutes. After lacking the dry components, the sawdust adds and mixes for 1 minute for homogeneity. After 2 minutes of mixing the water and added superplasticiser, the concrete poured in moulds. The determination of the density and mechanical characteristics (fc, fti and ftd) [332]; [333]; [335] uses the following moulds: cubes of 150 mm sizes and prisms of 100 mm x 100 mm x 550 mm. The samples were kept according to standard conditions until testing in 28 days [336].

4.2.2.2. Results 4.2.2.2.1. Density For all the mixes, standard densities were determined (Fig.103). Fig.103 shows that all concretes are lightweight concrete (the density is smaller than 2000 kg/mc). The density decreases by increasing the dosage aggregate replacement with sawdust. The slightest value of density occurred for an aggregate size of 0-4 mm replaced 100% with sawdust.

4.2.2.2.2. Compressive strength Results presented in Fig.103 show that fc decreased with the increasing of the aggregate Fig.103. Density of the lightweight concrete with replacement by sawdust. For a 40% dosage saw dust replacement, the value of fc is all right for lightweight concrete, but for the total replacement of aggregate sort 0-4 mm, the value of fc diminishes. Consequently, this concrete does not use as a construction material. Fig.104 presents the variation of compressive strength of the lightweight concrete.

Fig.104. Variation of compressive strength of the Fig.105. Variation of compressive strength with lightweight concrete the density

4.2.2.2.3. Flexural strength Fig.106 presents the values of fti. The fti values decreased with aggregate replacement dosage increasing. For 100% replacement of the aggregate 0-4 mm, the value of fti is too low to utilize the concrete as a building material even with reduced density.

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4.2.2.2.4. Split tensile strength Fig.107 presents experimental results for ftd. The ftd values decrease with aggregate replacement dosage increasing. For 100% replacement of the aggregate 0-4 mm, the value of fti is too low to use the concrete as a building material even with a reduced density.

In conclusion, replacing the aggregate of 0-4 mm by the waste of sawdust of same particle sizes results in a lightweight concrete of a lower density than 2000 kg/m3 for all the experimental mixes. For the replacement of aggregates under 50%, the concrete uses as a non-structural material. For an aggregate Fig.106. Variation of the flexural strength replacement over 80%, the mechanical properties like compressive strength, flexural strength and split tensile strength decrease very much so the concrete can be used in specific cases only (e.g. architectonic elements). Other characteristics of the concrete with sawdust, like thermal conductivity, noise protection, durability match the properties of the lightweight concrete.

4.2.3. Tensile properties of the green polymer concrete This study uses local materials to substitute Fig.107. Variation of the split tensile strength fine aggregates with sawdust and shredded plastic bottle wastes obtaining green concrete. The wastes of sawdust come from the wood industry while the chopped plastic bottles are sub-products of the re-using plastic waste process. The other materials were epoxy resin and fly ash from the Romanian industry and natural aggregates. A control mix of polymer concrete uses for comparison. The experimental mixtures were prepared by substituting the fine aggregate with wastes in percentages from 25% to 100%. The tensile tests were carried out to obtain flexural strength and splitting strength. The values of flexural strengths were higher for the polymer concrete with sawdust in comparison to chopped PET. For both wastes, the splitting strengths were higher than those of the control-mixture. The building materials industry is developing more and more and the sustainability requirements of new materials demand products cheaper and eco-friendly. Polymer concrete uses as a repair material for overlays of bridges, highways building and repair, as precast panels in buildings, waterproofing of pools or tanks [97]; [128]; [237]. Polymer concrete gathers using a resin of various types as a binder and natural aggregates of different sorts. Depending on the resin type, the polymer concrete recipe prepares with or without water. Usually, the binder represents a polymer that reacts with the hardener and binds the aggregates into an artificial conglomerate. In the mixture, different types of filler such as fly ash, silica fume, tire powder can use to properly improving [6]; [109]; [114]. For obtaining green polymer concrete, various wastes can be used as an addition or mix component substitution [379]. The fly ash, silica fume, slag, rice husk or rubber powder can replace the fine aggregates [29]; [32]; [70]; [167]; [363]. Natural aggregates can be replaced partially or totally by wastes such as chopped or grained tires, chopped plastic bottles, polystyrene grains, glass waste, re-cycled aggregate, agricultural waste, etc. [86]; [115]; [131]; [151]; [221]; [310]; [325]. Wastes can improve some properties of concrete, but generally, a decrease in mechanical properties is obtainable. Addition of fibres or nano- materials in concrete mixtures results in an improvement of tensile properties or durability

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Ancuța Rotaru Habilitation Thesis characteristics [97]; [237]. As the polymer concrete uses in many construction fields, the substitution of aggregates with wastes would help environmental pollution decrease and would save natural resources. Experimental results obtained on polymer concrete with two types of wastes used as a substitution of aggregates present effects on the flexural strength and split strength. The sawdust and chopped PET bottles in dosages between 26% and 100% substitute the sand.

4.2.3.1. Experimental programme The experimental research runs for a control-mixture and two mixtures of fine aggregate as substitutions. The control-mixture of the polymer concrete (CPC) was prepared based on the following components: epoxy resin 12.4 wt%, fly ash, as a filler, 12.8 wt% and two sorts of natural aggregates: 0- 4 mm sand (the sort I) and 4-8 mm gravel (the sort II) in the same percentage, i.e. 37.4% wt. All components express as percentages from the total weight of the mixture. The epoxy resin was a Romanian product from POLICOLOR S.A. București activated by a hardener type ROPOXID P401. The fly ash from Iași Electric Power Plant presents the following properties: grey with spherical particles of diameters ranging between 0.01 and 400µm, a specific area of 480-520 m2/kg, the density of 2400-2550 kg/m3, and a chemical content of Si (18.3%), C (17.15%) and Al (13.9%). The PET waste was obtainable as a sub-product of plastic bottle re-use processes. The chopped PET sizes range between 0 and 4 mm, and the unit weight is 433 kg/m3. The sawdust is a residue from the wood industry selected by sieving and replacing the 0-4 mm aggregates. The sawdust unit weight was 168 kg/m3. The green polymer concrete was prepared with the same dosage of epoxy resin, fly ash and 4-8 mm sort as the control-mixture, the sand only being replaced by saw dust and chopped plastic bottle (PET). In the first mixture, the sand was replaced with saw dust in dosages of 25%, 50%, 75% and 100% by volume (noted SDPC1 for a substitution of 25% to SDPC4 for a substitution of 100%, respectively). In the second mixture, the sand was replaced with PET in the same dosage of 25%, 50%, 75% and 100% by volume (noted PETPC1 for a substitution of 25% to PETPC4 for a substitution of 100%, respectively). For preparing polymer concrete, the aggregates, fly ash and waste were mixed together; the epoxy resin was combined with the hardener and introduced in the mixture. According to the European standard, the mixture was poured in 70x70x210 mm prismatic moulds and the samples were demoulded after 24 hours. At the age of 14 days, the samples were measured and tested in tension. The flexural strength (fti) and splitting tensile strength (ftd) were determined on three samples for each test according to standard prescription.

4.2.3.2. Results 4.2.3.2.1. Flexural strength The values of flexural strength for all mixes are presented in Fig.108. The polymer concrete with sawdust substitution of aggregates (SDPC2) with an increase of 12.6% compared to that of the control-mixture (Fig.109), attained the highest value of flexural strength, fti=18.25 MPa. The sawdust dosage influenced the flexural strength of the polymer concrete. The values of flexural strength for all mixes are presented in Fig.108. Just a single value of fti was lower than that of the control-mixture. For 75% substitution, decrease is about 8.8%. The maximum value of flexural strength of polymer concrete with PET substitution was 16.94 MPa (for PETPC1). It is 4.6% higher than that of the control-mixture. PET dosage as a replacement of aggregate influenced Fig.108. Variation of flexural strength of polymer concrete flexural strength of polymer concrete. Three values of fti were lower than that of the control-mixture, i.e. in case of 50%, 75% and 100% substitution. The decrease is about 6.3%, 1.97% and 19.3%, respectively.

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For both types of wastes as aggregate substitution, the mixtures with 50% and 75% sawdust have a better behaviour. For 25% and 100% chopped PET as substitution, mixes presented higher values of fti, as Fig.109 shows. Values of fti for both types of wastes as aggregate substitution were remarkably close.

4.2.3.2.2. Splitting strength Fig.109. Variation of flexural strength with the substitution Fig.110 represents the values of splitting strength for all mixtures. All split tensile strengths of mixtures with both types of aggregate substitution were higher than those of the control-mixture with 36.8% - 53.4%. The highest value of splitting strength ftd=7.38 MPa was scored for polymer concrete with sawdust substitution of aggregate (SDPC4), Fig.110. The maximum value of splitting strength polymer concrete with PET substitution was 6.68 MPa Fig.110. Variation of split tensile strength of the (for PETPC2), higher than that of the polymer concrete control-mixture with 4.6%. The PET dosage as replacement of aggregate influenced the splitting strength of polymer concrete by increasing the mechanical properties between 38.9% and 22.2%. Comparing the two types of wastes used as an aggregate substitution, the mixtures with sawdust as a substitution for all replacement dosages (Fig.111) had a better behaviour. The values of ftd for both types of wastes as aggregatesubstitution were very close. Researchers are studying modern concretes embodying local materials or wastes to achieve cheaper products and also environmental protection. In the experimental programme, the wastes used as a substitution of the sand in the polymer concrete were the sawdust and chopped PET. The replacement of sort I aggregate was between 25% and 100%. Both types of wastes influenced the tensile strength of polymer concrete. Generally, for Fig.111. Variation of split tensile strength function the both types of substitution, the tensile substitution dosage strength was smaller increasing the substitution dosage. The influence of substitution type on the flexural strength and splitting strength indicated higher values for mixtures with sawdust. The polymer concrete with both sawdust substitution presented the most significant flexural strength for a 50% replacement of fine aggregates. For PET waste, the highest value of flexural strength was at 25% aggregate substitution. For the splitting strength, all values were higher than that of the control-mixture for both types of substitution. The highest value is obtainable for 100% aggregate substitution with sawdust and 50% PET substitution.

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5. OBJECTIVES OF SCIENTIFIC RESEARCH, CONTRIBUTIONS TO THE FIELD OF CIVIL ENGINEERING

The habilitation thesis presents the results of scientific research activity accumulated after the doctoral thesis defense (November 1997 - end of 2020). Thesis contributions address to the Civil Engineering domain. They are focused towards the geotechnical and geoenvironmental areas of study as well as to the topic related to material sustainability and durability for infrastructure maintenance and rehabilitation. In summary, the master research objectives and the contributions to the field of Civil Engineering are the following:  Bringing off a geotechnical database based on available documentation.  Database processing and interpretation to highlight the influence of natural risk and anthropogenic factors on the lithology and variability of the properties of the foundation soils;  Practical approaches to mitigate the built environment danger in areas with high geotechnical risk due to natural disasters (earthquakes, landslides, floods, etc.)  The analysis of areas with high geotechnical risk from a geological, hydrological and historical point of view, understanding and motivating the behaviour of constructions from a geotechnical point of view;  The evaluation of geotechnical performance of the foundation soil to mitigate the associated risks analysing the soil properties and variability as lithological entities, with the formation and evolution conditioned by natural processes and events.  Development of experimental programmes for detailed determination of difficult foundation soils properties in certain areas of Romania for the efficiency of foundation system solutions to ensure stability and safety to the built environment.  Detailed experimental investigations on the behaviour of specific wastes to identify their relevant parameters in order to use them as cement/aggregate substitutes in concrete infrastructure works. The cement industry contributes to the increase of CO2 emissions, both through the production process and the consumption of electricity generated by fossil fuels. This fact encouraged the use of locally available wastes used as binders in the manufacture of concrete.  As an objective from the perspective of environmental protection, the development of concrete was analyzed following two directions: 1) partial replacement of cement with ash wastes, 2) partial/total replacement of mineral aggregates with sustainable and easily renewable wastes that reduce pollution.

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III. DEVELOPMENT DIRECTIONS

Teaching activity The strategic objective will ensure a thorough educational act able to form the competencies the study programmes provide, meeting the requirements of the labour market in Romania and the European Union.  I shall renew the discipline content following European standards.  I shall further motivate and stimulate students by organizing meetings to improve their interest in the programme they selected. Also, I shall get them interested in the Erasmus+ KA103 and KA107 mobility programmes. Those programmes allow them to access new sources of information and learn new approaches. Along with new colleagues from EU or non-EU countries, they will share cultures and manners.  I shall emphasize the applicative character of laboratory works and shall vary the methods of checking the knowledge acquired through these practical activities.  I shall use in the teaching process the modern equipment of the department and specialized software, blending the theory with practical elements.  I shall stimulate students' individual and team study allowing them to create and collaborate through projects and essays; I shall organize debates on announced topics stimulating students' ability to communicate.  I shall establish topics for undergraduate, dissertation and doctoral works following the departmental research directions and an orientation towards innovative subjects, which offers efficient solutions ready to be implemented.  I shall stimulate the scientific research activity of master students proposing them by the end of their studies to disseminate team’s scientific results through at least one scientific paper published in a journal or presented in a conference.  Through the Erasmus + programs I coordinate, I shall encourage and guide students to apply for study and training mobility and introduce students to renowned specialists from various European universities and around the world who will give interesting lectures and maintain feedback as well as a useful and high interest for novelty and diversity.  Through the bilateral Erasmus+ agreements I coordinate, I shall contribute to the academic experience exchange through knowledge transfer inviting foreign teachers from partner Erasmus universities to give Erasmus+ lectures in our classrooms.  I shall organize visits to relevant economic objectives.  As before, there will be a partnership based on dialogue with students encouraging new, creative proposals and storms of ideas.

Scientific activity The results carried out from the interdisciplinary research lead to new horizons. Among the presumable research directions addressed shortly, I can mention:  Capitalizing on research results by publishing scientific articles in ISI and BDI indexed publications;  Maintaining connections with researchers and specialists from other partner universities with similar research topics and continuing to participate in international conferences to disseminate the results obtained by our joint teams of researchers;  Involvement in project proposal by identifying calls for national and international research grants, registering the department or research teams on the portals of research programs in partnership with European funding and participation in national or international projects;  Joining multidisciplinary research teams, the key to the success of future research projects;  Acquiring new skills in terms of research activity by participating in training courses;  Studying the researches and achievements of other research teams to establish new partnerships;  Expanding the collaboration with the entrepreneurial environment and establishing research topics following previous concerns, but also with relevance for the economic circumstances;

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 Accessing funds for the purchase of laboratory equipment and specialized software, as well as modernizing existing facilities;  Involving students in research activities, co-opting them (especially master and doctoral students) in research projects carried out within the department and encouraging them to participate in national and international scientific events.

Developing the directions presented in the thesis In terms of developing the scientific research presented in the current habilitation thesis, I strongly believe that future contributions have to focus on the following directions:  Increasing the safety and security in construction operation through a thorough analysis, knowledge, and minimization of natural risk factors that could affect the foundation soils. - Development of integrated methods for identification, analysis and assessment of the risk impact on the built environment; - Improving techniques for investigating landslides and slopes prone to landslides and increasing the accuracy of stability studies by considering new variables in the analysis models; - Case studies meant to identify the areas with a potential risk of landslides, causes and factors which triggered landslides and to design solutions to stabilize or maintain them; - Carrying out projects for identification, analysis and assessment of the environmental risk for various built objectives to constitute guides of good practices in the field.  To increase the predictability of soil behaviour as support for foundations. - Optimizing the current techniques to improve the problematic soils, respectively applying modern solutions and techniques in constructions, with emphasis on less aggressive technologies towards the environment; - Using geotechnical parameters in infrastructure design; Both directions of research converge on the following objectives: - Optimization of infrastructure rehabilitation solutions in various contexts of built environment risk; - The influence of the construction-foundation interaction in specific risk contexts, on the selection of soil behaviour patterns;  Development of eco-sustainable solutions for infrastructures through: - Optimizing the use of materials resulting from various waste recycling techniques in soil mixtures to improve the load-bearing capacity of difficult foundation soils; - Identification and analysis of the physical-mechanical properties of some categories of waste with the binder role to use them in the ecological concrete (studies in progress are done by the author on jute fibres as well, working in an international team along with Moroccan partners from the University Mohammed V from Rabat); - Rehabilitation of infrastructure works by replacing a part of natural concrete aggregates with some industrial waste. - Integration of sustainable rehabilitation concept in local strategies of built environment conservation; - Elaboration of practical guides to identify the possibilities of sustainable rehabilitation/reconstruction and the directions of its integrated approach. - The global approach to the issue concerning the ecological reconstruction of soils affected by natural disasters and the choice of optimal options.

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243 Robu I., 1986, Binder Compositions Based on Fly Ash from the Power Plant, PhD thesis, Civil Engineering Institute of Bucharest (in romanian). 244 Rodriguez C.E., Bommer J.J., Chandler R.J., 1999, Earthquake-induced Landslides: 1980-1997, Soil Dynamics and Earthquake Engineering, 18, 325-346. 245 Rogbeck J, Knutz A, Coal Bottom Ash as Light Fill Material in Construction, Waste Management, 16(13), 1996, 125-128. 246 Rogozhin E.A., Kharazovamm V.Y, Gorbatikov A.V., Shanov S., Stepanova M.Y., Mitev A., The Structure and Contemporary Activity of the Intramoesian Fault in Northeastern Bulgaria Obtained through a Complex of New Geological-geophysical Methods, Izvestiya Phy. Sol. Earth, 45(9), 2009, 794-80. 247 Rosen M., 2009, Energy and Environmental Advantages of Cogeneration with Nuclear and Coal Electrical Utilities, Proc. 4th IASME / WSEAS Int. Conf. on Energy & Environment (EE'09), Cambridge, 175-182. 248 Rotaru A., 2004, Încercări la tensiune pe probe de argilă saturată normal consolidată anizotrop supusă la încercări de încărcare-descărcare asupra rezistenţei şi deformaţiilor în timp ale pământurilor, Sesiunea ştiinţifică Construcții – Instalații CIB 2004, Braşov, Vol.2, Editura Universităţii Transilvania-Braşov, 219- 222. 249 Rotaru A., 2004, Knowing the Complex of Consequences Produced by Earthquakes in Order to Increase the Safety of Buildings, International Symposium ”New Solutions for Essential Requirements in Buildings”, Iaşi, Editura Societăţii Academice „Matei-Teiu Botez”, 160-165. 250 Rotaru A., 2004, Stabilirea unor relaţii între tensiunea efectivă şi umiditate la argilele saturate, A X-a Conferinţă Naţională de Geotehnică şi Fundaţii, Bucureşti, Vol.1, Editura Conspress, 141-148. 251 Rotaru A., 2004, Systems for the Remediation of the Quality of the Contaminated Groundwater, International Symposium ”New Solutions for Essential Requirements in Buildings” (SIEC), Iaşi, Editura Societăţii Academice „Matei-Teiu Botez”, 174-182. 252 Rotaru A., 2005, Procedee şi tehnologii de îmbunătăţire a proprietăţilor terenurilor dificile de fundare în vederea creşterii sigurantei şi durabilităţii infrastructurii construcţiilor inginereşti, Revista de Politica Științei şi Scientometrie, Număr special 2005, Editată CNCSIS, 1-19. 253 Rotaru A., 2007, Some Consideration upon Landslide Repair and Correction, International PIARC Seminar „Adapting Road Earthworks to the Local Environment”, Iaşi. 254 Rotaru A., 2007, Some Consideration upon Lanslide Risk Mitigation, Adapting Road Earthworks to the Local Environment, International PIARC Seminar, Iași - Romania, Editura Impakt, 235-254. 255 Rotaru A., 2008, Quality Control and Remediation of Contaminated Soils in Urban Areas–Some Examples from Romania, Australian Journal of Basic and Applied Sciences, 2(4), 929-938. 256 Rotaru A., 2008, Starea de tesiuni în masivele de pământ ce suportă construcţii, Editura Societăţii Academice “Matei-Teiu Botez” Iaşi. 257 Rotaru A., 2008, Swelling-Shrinking Phenomena Recorded on Bahlui Clay Iași, Development of Urban Areas and Geotechnical Engineering, International Geotechnical Conference, Saint Petersburg, vol.2, NPO „Geoconstruction-Fundamentproject”, 443-448. 258 Rotaru A., 2009, Some Consideration upon Lanslide Risk Mitigation, Proceedings of International Seminar on Managing Operational Risk on Roads, Iași, Romania, Editura Impakt. 259 Rotaru A., 2010, Causes and Mechanisms of Landslides Triggered on Foundation Soil Areas, Geophysical Research Abstracts, 12, EGU2010-13952, 2010EGU General Assembly. 260 Rotaru A., 2010, Geoenvironmental Issues Concerning the Black Sea Basin, International Journal of Energy and Environment Published by NAUN, 4(4), 131-138. 261 Rotaru A., 2010, Landslides in Romania, Proceedings of the International Conference on Geotechnical Engineering, Lahore, Pakistan, 229-236, Pakistan Geotechnical Engineering Society (PGES), Sohail Kibria, Hamid Masood, Qureshi Arooj, Mahmood Rana (eds.). 262 Rotaru A., 2010, Some Geo-aspects of the Black Sea Basin, Advances in Environmental and Geological Science and Engineering, WSEAS Press, 169-174. 263 Rotaru A., 2010, Some Processes Responsible for Difficult Foundation Soils in Iași, Romania, Proceedings of the XIVth Danube-European Conference on Geotechnical Engineering „From Research to Design in European Practice“, Bratislava, Slovakia, Slovak University of Technology, Jana Frankovská, Jozef Hulla, Martin Ondrášik, Peter Turček (eds.). 264 Rotaru A., 2011, Landslides Triggered in Hard Soils and Soft Rocks in Romania, The 15th European Conference on Soil Mechanics and Geotechnical Engineering - Geotechnics of Hard Soils – Weak Rocks, Andreas Anagnostopoulos, Michael Pachakis, Christos Tsatsanifos (eds.), IOS Press, 1383-1387, Athens.

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265 Rotaru A., Babor T.D., 2004, Basic Concepts and Methods of Probability in Geotechnical Engineering, International Conference “Performance Based Engineering for 21st Century”, Multidisciplinary Center for Education, Research and Quality Management, Iaşi, Romania, Editura Cermi, 342-348. 266 Rotaru A., Babor T.D., 2004, Calculul deformaţiilor pentru probe de argilă saturată consolidată anizotrop supusă la încercări de încărcare – descărcare. Condiţii de normalitate si Ko, Buletinul Institutului Politehnic din Iaşi, secţia VI, Construcţii. Arhitectură, Tomul L(LIV), Fasc.5, 285-290. 267 Rotaru A., Babor T.D., 2004, Some Criteria for Liquefaction and the Influence of the Geologic Time in Liquefaction Process, International Conference VSU 2004, Sofia, Bulgaria, Vol.2, University of Structural Engineering and Architecture "Lyuben Karavelov" Publishing House, IV-67 – IV-71. 268 Rotaru A., Babor T.D., 2004, Stability Coefficients versus Stability Evaluation using Finite Element-Neural Network Hybrid Algorithms for Earth Slopes Analysis, “Computational Civil Engineering. 2004”, International Symposium, Iaşi, Romania, Editura Societăţii Academice „Matei-Teiu Botez”, 236-242. 269 Rotaru A., Babor T.D., Deformability Analysis of Rock for Homogenous and Discontinuous Multi-Crack Masses, “Computational Civil Engineering. 2004”, Editura Societăţii Academice „Matei-Teiu Botez”, International Symposium, Iaşi, Romania, 2004, 229-235. 270 Rotaru A., Babor T.D., Răileanu P., Rotaru P., 2004, Influenţa particularităţilor stării de tensiuni asupra rezistenţei şi deformaţiilor în timp ale pământurilor, Sesiunea ştiinţifică Construcții – Instalații CIB 2004, Braşov, Vol.2, Editura Universităţii Transilvania-Braşov, 161-166. 271 Rotaru A., Bhandari G., 2017, Bridging New Solutions for Sustainable Rehabilitation of Structures Damaged Due to Difficult Soils or Foundation Design, Advanced Engineering Forum, Proceedings of EBUILT International Conference, November 16-19, 2016, Iași, Romania, 21, 346-351. 272 Rotaru A., Bhandari G., 2020, The Impact of Environmental Degradation: Atmospheric and Geological Issues in Built Areas, Rotaru A. (ed.), Critical Thinking in the Sustainable Rehabilitation and Risk Management of the Built Environment. CRIT-RE-BUILT 2019, Springer Series in Geomechanics and Geoengineering, 35- 46. 273 Rotaru A., Boboc V., 2008, Calculul tensiunilor de forfecare dintr-un masiv de pământ, determinate de o suprafaţă încărcată, utilizând metoda sectorului, „Probleme actuale ale urbanismului şi amenajării teritoriului”, Culegere de articole Conferinţa Tehnico-ştiinţifică internaţională IV, Vol.I, Secţia Drumuri, materiale şi mecanizarea construcţiilor, Chişinău, Editura CEP a Universității de Stat din Moldova, 197-200. 274 Rotaru A., Boboc V., 2008, Calculul tensiunilor verticale şi totale dintr-un masiv de pământ, determinate de o suprafaţă încărcată, utilizând metoda sectorului, Sesiunea ştiinţifică Construcţii - Instalaţii CIB 2008, Braşov, Vol.1, Editura Universităţii Transilvania din Braşov, 315-318. 275 Rotaru A., Boboc V., 2010, A Material Used in Substructure and Road Works: Physical Characteristics of Pozzolana Fly Ash from Thermal Power Plant of Iași, Romania, WSEAS Transactions on Environment and Development, 6(6), 427. 276 Rotaru A., Boboc V., Physical Properties of Pozzolana Fly Ash from Thermal Power Plant of Iasi, Romania – A Cement-like Material for Substructure Works, 2010, Recent Advances in Electrical Engineering, WSEAS Press, 187-193. 277 Rotaru A., Boboc V., Țăranu N., Abdelhadi M., Boboc A., Banu O.M., 2019, The Compressive Behaviour of Aggregates Cemented with Fly Ash Collected from Coal-fired Power Plants, Romanian Journal of Materials, 49(1), 141-147. 278 Rotaru A., Kolev Ch., 2010, Addressing Issues of Geoenvironmental Risks in Dobruja, Romania/Bulgaria, Environmental Engineering and Management Journal 9(7), 961-969. 279 Rotaru A., Kolev Ch., 2010, Geological and Geotechnical Specificity in Dobruja Region of Bulgaria and Romania, 10th International Scientific Conference VSU' 2010, Sofia, Bulgaria, vol. II, University of Structural Engineering and Architecture "Lyuben Karavelov" Publishing House, 81-87. 280 Rotaru A., Nicuţă A., 2008, Some Aspects of Landslide Risk Evaluation Taking into Account their Distribution and Properties, Journal Materials, Methods and Technologies, International Scientific Publications, 2(1), Published by Info Invest, Bulgaria, 47-57. 281 Rotaru A., Nicuță A., 2008, Some Aspects of Landslide Risk Evaluation Taking into Account Their Distribution and Properties, Journal of Materials, Methods and Technologies, International Scientific Publications, 2(1), 47-57. 282 Rotaru A., Nicuţă A., 2008, Some Processes Responsible for Landslides, Jubilee International Scientific Conference VSU 2008, Sofia, Bulgaria, Vo.2, University of Structural Engineering and Architecture "Lyuben Karavelov" Publishing House, VII-65 – VII-70.

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283 Rotaru A., Oajdea D., Răileanu P., 2007, Analysis of the Landslide Movements, International Journal of Geology, 1(3). 284 Rotaru A., Oajdea D., Răileanu P., 2008, Dynamics of a Landslide Surface, Environmental Problems and Development, Energy and Environmental Engineering Series, 22-27. 285 Rotaru A., Pescaru R.A., Olteanu-Donţov I., Nicuţă A.M., Mihai P., Ciocan V., Marius-Costel Balan, 2020, Hazard Risk Mitigation for a Sustainable Built Environment, Rotaru A. (ed.), Critical Thinking in the Sustainable Rehabilitation and Risk Management of the Built Environment. CRIT-RE-BUILT, Springer Series in Geomechanics and Geoengineering, 3-34. 286 Rotaru A., Pohrib D.M., 2020, Stabilization of Roads Located on Banks of Mountain Flowing Waters, Rotaru A. (ed.) Critical Thinking in the Sustainable Rehabilitation and Risk Management of the Built Environment. CRIT-RE-BUILT, Springer Series in Geomechanics and Geoengineering, 130-141. 287 Rotaru A., Răileanu P., 2004, Alunecările de teren – catastrofe majore, „Disaster and Pollution Monitoring”, 1st International Conference, Iaşi, Pollution Section, Editura Performantica, 357-362. 288 Rotaru A., Răileanu P., 2004, Comportarea argilelor la încărcare ciclică, A X-a Conferinţă Naţională de Geotehnică şi Fundaţii, Bucureşti, Vol.1, Editura Conspress,153-158. 289 Rotaru A., Răileanu P., 2004, De ce este necesară cunoaşterea stării de tensiuni în masivele de pământ acţionate de construcţii inginereşti, „Ştiinţa şi învăţământul – fundamente ale secolului al XXI-lea”, A IX-a Sesiune de comunicări ştiinţifice cu participare internaţională, Sibiu, Vol.IV, Editura Academiei Forţelor Terestre „Nicolae Bălcescu”. 139-144.

290 Rotaru A., Răileanu P., 2004, Deformaţiile axiale şi Ko determinate pe probe de argilă saturată normal consolidată anizotrop supusă la încercări de încărcare-descărcare, „Ştiinţa şi învăţământul – fundamente ale secolului al XXI-lea”, A IX-a Sesiune de comunicări ştiinţifice cu participare internaţională, Sibiu, Vol.IV, Editura Academiei Forţelor Terestre „Nicolae Bălcescu”, 139-144. 291 Rotaru A., Răileanu P., 2004, Elements of Geology, Academic Publishing Company “Matei-Teiu Botez”, Iași. 292 Rotaru A., Răileanu P., 2004, Influenţa anizotropiei terenurilor de fundare asupra stării de tensiuni, A X-a Conferinţă Naţională de Geotehnică şi Fundaţii, Bucureşti, Vol.1, 149-152. 293 Rotaru A., Răileanu P., 2004, Seismic Waves Propagation in Soil Deposits Taking into Account of Soil Stratification, Proceedings of International Conference VSU 2004, Sofia, Bulgaria, Vol.1, University of Structural Engineering and Architecture "Lyuben Karavelov" Publishing House, I-90 - I-99. 294 Rotaru A., Răileanu P., 2004, The Importance of Hydrogeolgical Analyses of Groundwater Behaviour in the Slope Stability Analyses, „Ovidius” University Annals, Constanţa, Construcţii VI, International Symposium ”Civil Engineering 2004”, section VIII ”Water Resurces Management, Environmental Engineering”, Ovidius University Press, 309-314. 295 Rotaru A., Răileanu P., 2008, Groundwater Contamination from Waste Storage Works, Environmental Engineering and Management Journal, 7, Editura EcoZONE, 732-736. 296 Rotaru A., Răileanu P., 2009, Landslide in Pârcovaci, Iași County, International PIARC Seminar on "Managing Operational Risks on Roads", Iaşi. 297 Rotaru A., Răileanu P., 2009, Some Models of Soil Behaviour for Evaluation of Consolidation Settlement in Clays, Proceedings of the 17th International Conference on Soil Mechanics and Geotechnical Engineering, Alexandria, Egypt, IOS Press under the imprint Millpress. 298 Rotaru A., Răileanu P., Groundwater Resources Management, „Ovidius” University Annals, Constanţa, International Symposium ”Civil Engineering 2004”, section ”Water Resources Management, Environmental Engineering”, Ovidius University Press, 303-308. 299 Rotaru A., Răileanu P., Nicuţă A., 2008, Alunecările de teren din judeţul Iaşi în perioada 1995-2005, A XI-a Conferinţă Naţională de Geotehnică şi Fundaţii, Timişoara, Editura Politehnica, 692-697. 300 Rotaru A., Răileanu P., Petru Rotaru, 2005, How to Build on Difficult Foundation Soils in Iași County Area, „Intersecţii/Intersections”, 2 (9), „Transportation Infrastructure Engineering”, Editura Societăţii Academice “Matei-Teiu Botez”, 62-72. 301 Rotaru A., Răileanu P., Rotaru P., 2001, Asupra posibilităţilor de protecţie a apei subterane şi folosirea ei în scopuri ecologice, Tehnomil Sibiu, Subsecţiunea 1.4.b Chimie. Ecologie. Geniu. Construcţii, Editura Academiei Forţelor Terestre „Nicolae Bălcescu”, 55-62. 302 Rotaru A., Răileanu P., Rotaru P., 2001, Depozite geotehnice de adâncime pentru stocarea deşeurilor nucleare, Tehnomil Sibiu, Subsecţiunea 1.4.b Chimie. Ecologie. Geniu. Construcţii. Editura Academiei Forţelor Terestre „Nicolae Bălcescu”, 63-70.

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303 Rotaru A., Răileanu P., Rotaru P., 2001, Folosirea deşeurilor la realizarea fundaţiilor lucrărilor de infrastructuri pentru transporturi rutiere, Zilele academice timişene, Ediţia a VII-a, Timişoara, Romania, „Infrastructuri eficiente pentru transporturile terestre”, Vol.II, Editura SOLNESS Timişoara, 487-493. 304 Rotaru A., Răileanu P., Rotaru P., 2004, Expresiile funcţiilor tensiune-deformaţie-timp ce caracterizează curgerea lentă la pământuri, „Probleme actuale ale urbanismului şi amenajării teritoriului”, Conferinţa Tehnico-ştiinţifică internaţională, Chişinău, Vol.3, Secţia Drumuri, materiale şi mecanizarea construcţiilor, Editura CEP a Universității de Stat din Moldova, 250-255. 305 Rotaru A., Răileanu P., Rotaru P., 2004, Particularităţi ale curgerii lente la argile, „Probleme actuale ale urbanismului şi amenajării teritoriului”, Conferinţa Tehnico-ştiinţifică internaţională II(3), Drumuri, materiale şi mecanizarea construcţiilor, Chişinău, Editura CEP a Universității de Stat din Moldova, 244-249. 306 Rotaru A., Răileanu P., Rotaru P., 2008, Research Concerning the Water Seepage in the Basement of the Orthodox Cathedral of Bacău, Romania, IP Iași Bulletin, XIV(LXIII)(4), Construction. Architecture. 307 Rotaru A., Răileanu P., Talhouni A., 2000, Aspecte teoretice şi de calcul privind starea de tensiune a pământurilor supuse la încercări dinamice, A IX-a Conferinţă Naţională de Geotehnică şi Fundaţii, Cluj- Napoca, Vol.I, 247-256, Editura U.T. PRES. 308 Rotaru A., Rotaru P., 2001, Consideraţii asupra influenţei anizotropiei în determinarea stării de tensiuni în masivele de pământ, Realizări şi perspective în activitatea de construcţii şi în învăţământul de specialitate, Iaşi, V.I, Secţiune Geotehnică, topografie, căi de comunicaţii, Edit. Societăţii Academice „Matei-Teiu Botez”, 93- 98. 309 Rotaru A., Babor T.D., 2004, Aplicarea relaţiilor unice dintre umiditate şi tensiunile efective la argilele saturate, Buletinul Institutului Politehnic din Iaşi, secţia VI, Construcţii. Arhitectură, L(LIV), 5, 279-284. 310 Saikia N., De Brito J., 2014, Mechanical Properties and Abrasion Behaviour of Concrete Containing Shredded PET Bottle Waste as a Partial Substitution of Natural Aggregate, Construction and Building Materials, 52, 236-244. 311 Săndulescu M., 1984, Geotectonics of Romania, Ed.Tehnică, 334. 312 Sato A., Hirakawa Y., Sugawara K., 2000, Homogenized Multi-crack Model for Deformability Analysis of Rock Mass, International Conference of Geotechnics and Foundations, Melbourne, Australia. 313 Scheetz B.E., Earle R., 1998, Utilization of Fly Ash, Current Opinion in Solid State & Materials Science, 3(5). 314 Schmidt-Thomé, P. (ed.), 2006, Natural and Technological Hazards and Risks Affecting the Spatial Development of European Regions, Geological Survey of Finland, 42, Special Paper, 167. 315 Sear L., 2008, Research and Practical Applications Using Sustainable Construction Materials and Technology in Asphalt and Pavement Engineering, in Proceedings of LJMU 2008 Annual International Conference, Liverpool, UK, 20th - 21st, 12. 316 Seghedi A., 2005, Geological and Stuctural Frame of the Lands around the Black Sea, Special Remark on Northwestern Margin, Natural Hazard: Tsunami Events into the Black Sea, 11-26. 317 Seghedi A., Berza T., Iancu V., Mărunțiu M., Oaie G., 2005, Neoproterozoic Terranes in the Moesian Basement and in the Alpine Danubian Nappes of the South Carpathians, Geologica Belgica, 8(4). 318 Șerbănoiu A.A., Bărbuță M., Burlacu A., Grădinaru C.M., 2017, Fly Ash Cement Concrete with Steel Fibers - Comparative Study, Environmental Engineering and Management Journal, 16(5), 1123. 319 Shanov St., 2005, Post-Cretaceous to Recent Stress Fields in the SE Moesian Platform (Bulgaria), Tectonophysics, 410(1-4), 217-233. 320 Shi C., Zhang, Y., Li, W., Chong, L., Xie, Z., 2016, Performance Enhancement of Recycled Concrete Aggregate - A Review, Journal of Cleaner Production, 112, 466-472. 321 Shimkus K.M., 1997, Fluxes of Sediments and Pollutants in the Black Sea, Proc. IOWBSRC Workshop on Black Sea Fluxes, Namik Cagatay Univ., Instit. of Marine Sci. and Management, 628. 322 Siddique R., 2008, Waste Materials and By-products in Concrete, Springer-Verlag, Berlin Heidelberg. 323 Silion T., Răileanu P., 1990, Geology, Edited by Institutul Politehnic Iași. 324 Singh B., Ishwarya G., Gupta M., Bhattacharyya S.K., 2015, Geopolymer Concrete: A Review of Some Recent Developments, Construction and Building Materials, 85, 78-90. 325 Skariah T.B., Chandra G.R., 2016, Properties of High Strength Concrete Containing Scrap Tire Rubber, Journal of Cleaner Production, 113, 86-92. 326 Skodras G., Karangelos D., Anagnostakis M., Hinis E., Grammelis P., Kakaras E., 2005, Coal FlyAsh Utilisation in Greece, Int. Ash Utilization Symposia and the World f Coal Ash Conference.

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327 Sladen J.A., D'Hollander R.D.D., Krahn J., 2011, The Liquefaction of Sands, a Collapse Surface Approach, Canadian Geotechnical Journal, 22(4), 564-578. 328 Spatary A.N., 1990, Breakwaters for the Paratactic of Romanian Beaches, Coastal Engineering, 14. 329 SR 13298 / 95, Natural and Man-made Pozzolana Materials (in Romanian). 330 SR EN 1097-2:2010, Tests for Mechanical and Physical Properties of Aggregates. Methods for the Determination of Resistance to Fragmentation, Romanian Standard Association (in Romanian). 331 SR EN 1097-3:2002, Tests for Mechanical and Physical Properties of Aggregates - Part 3: Determination of Loose Bulk Density and Voids, Romanian Standard Association (in Romanian). 332 SR EN 12390-3:2005, 2011, Testing Hardened Concrete, Part 3: Compressive Strength of Test Specimens (in Romanian). 333 SR EN 12390-5:2005, 2009, Testing Hardened Concrete, Part 5: Flexural Strength of Test Specimens (in Romanian). 334 SR EN 12390-5:2005, Tests for Geometrical Properties of Aggregates. Part 1.Determination of Particle-size Distribution - Sieving Method (in Romanian). 335 SR EN 12390-6:2010, Testing Hardened Concrete, Part 6: Split Tensile Strength of Test Specimen (in Romanian). 336 SR EN 12390-7:2005, Testing Hardened Concrete. Part 7: Density of Hardened Concrete. 337 SR EN 12697-6:2012, Bituminous Mixtures. Test Methods for Hot Mix Asphalt. Determination of Bulk Density of Bituminous Specimens, Romanian Standard Association (in Romanian). 338 SR EN 13286-2:2011, Unbound and Hydraulically Bound Mixtures - Part 2: Test Methods for Laboratory Reference Density and Water Content - Proctor Compaction, Romanian Standard Association (in Romanian). 339 SR EN 196-1:2016, Methods of Testing Cement - Part 1: Determination of Strength, Romanian Standard Association (in Romanian). 340 SR EN 196-6:2010, Methods of Testing Cement. Determination of Fineness, Romanian Standard Association (in Romanian). 341 SR EN 197-1:2011, Cement. Part 1: Composition, Specifications and Conformity Criteria for Common Cements, Romanian Standard Association (in Romanian). 342 SR EN 933-1:2012, Tests for Geometrical Properties of Aggregates. Determination of Particle Size Distribution. Sieving Method, Romanian Standard Association (in Romanian). 343 SR EN 933-4:2008, Tests for Geometrical Properties of Aggregates. Determination of Particle Shape. Shape Index, Romanian Standard Association (in Romanian). 344 SR EN 933-8+A1:2015 Tests for Geometrical Properties of Aggregates. Assessment of Fines. Sand Equivalent Test, Romanian Standard Association (in Romanian). 345 SR EN ISO 14688/2-2018, Geotechnical Investigation and Testing - Identification and Classification of Soil - Part 2: Principles for a Classification, Romanian Standard Association (in Romanian). 346 Stanciu A., Lungu I., 2006, Foundations I, Ed. Tehnică, Bucharest. 347 STAS 10473/2-1986, Straturi rutiere din agregate naturale sau pământuri stabilizate cu lianți hidarulici sau puzzolanici/ Road Layers of Natural Aggregates or Stabilized Soils with Hydraulic or Puzzolanic Binders (in Romanian). 348 STAS 1913/13-83, Determinarea caracteristicilor de compactare. Încercarea Proctor/ Determination of Compaction Characteristics. Proctor Test (in Romanian). 349 Ștefan (Oancea) I., Bărbuță M., Budescu M., Mihai P., Banu O.M., Țăranu N., Particularities Regarding the Mechanical Behaviour of Some Types of Sustainable Concrete Mixes with Waste Materials, 2018, Romanian Journal of Materials, 48(2), 236. 350 Tang W.C., Cui H.Z., Wu M., 2014, Creep and Creep Recovery Properties of Polystyrene Aggregate Concrete, Construction and Building Materials, 51, 338-343. 351 Tanislav D., Costache A., Murătoreanu G., 2009, Vulnerability to Natural Hazards in Romania, Forum Geografic. Studii şi cercetări de geografie şi protecţia mediului, 8(8), 131-138. 352 Tanislav M., Dinu I., Mafteiu M., 2009, Landslides in the Danube–Black Sea Canal Area, Geo-Eco-Marina, 15, 53-62. 353 Temiz A., 2008, GIS Based Landslide Susceptibility Mapping: Karabük Province Case in Turkey, Proceedings of the 1st WSEAS International Conference on Environmental and Geological Science and Engineering (EG'08), Malta, Published by WSEAS Press, 43-51.

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