Assessment of Rock Mass Instability of Es-Sileitat Quarries, Eastern Khartoum State, Sudan

AL NEELAIN UNIVERSITY Graduate Collage

By: Eltayeb Bashir Hassan Hamid B. Sc. (Hons.) 2014, Al Neelain University

A Dissertation submitted to the Graduate Collage, Al Neelain University for the partial fulfilment of the Master Degree of Geology (Engineering Geology)

Jan.2020

AL NEELAIN UNIVERSITY Graduate Collage

Assessment of Rock Mass Instability of Es-Sileitat Quarries, Eastern Khartoum State, Sudan

By: Eltayeb Bashir Hassan Hamid B. Sc. (Hons.) 2014, Al Neelain University

A Dissertation submitted to the Graduate Collage, Al Neelain University for the partial fulfilment of the Master Degree of Geology (Engineering Geology)

Supervisor: Dr. Esamaldeen Ali M. Ahmed Signature:…...... External Examiner: Dr. Mohammd Aljack Signature:………... Internal Examiner: Dr. Ibrahim Abdelgadir Signature:………....

قال تعالى:

) َوا ْذ ُك ُروا إِ ْذ َج َعلَ ُك ْم ُخلَفَا َء ِم ْن بَ ْع ِد َعا ٍد َوبَ َّوأَ ُك ْم فِي ا ْْلَ ْر ِض تَتَّ ِخ ُذو َن ِم ْن ُسهُولِهَا قُ ُصو ًرا َوت َ ْن ِحتُو َن ا ْل ِجبَا َل بُيُوتًا ۖ فَا ْذ ُك ُروا آ ََل َء ََّّللاِ َو ََل تَ ْعثَ ْوا فِي ا ْْلَ ْر ِض ُم ْف ِس ِدي َن (

صدق هللا العظيم سورة اْلعراف- آية رقم )74(

Dedication I dedicate this humble work to: My father My mother My brothers (Hassan and Omer) My sisters My wife My daughter My friends To every one helped me To everyone love Knowledge.

ACKNOWLEDGEMENTS

Praise Allah for helping me to finish this work.

I would like to express my deepest gratitude and thanks to Dr. Esamaldeen Ali for his supervision, limitless help, scientific Guidance, continuous encouragement and fruitful comments, helped and supported during the research.

Special and deepest thankful and grateful to my family for their patience and support. Also I would like to thanks my friends for support and help; EL Khider Rahamt Allah, Ezeldeen Mohamed, Abuobida Abdalkarim, Khattab Abdelrazig, and all my friends in the program of M.Sc. of engineering geology. My thank continue to reach everyone help me to finish this work.

List of Contents

Dedication………………………………………………………………...………I Acknowledgement………………………………………………...... II Abstract……………………………………………………………………...... III IV.…..…………….………………………………………………………المستخلص List of contents……………………………………………………………….….V List of tables…………………………………………………………………....IX List of figures…………………………………………………………………....X List of plates ………………………………………………………………..…..IX CHAPTER І: Introduction 1.1 Research Significance ……………………………………………………….1 1.2 Statements of Problem ………………….…………………...……………....1 1.3 Location and Accessibility……………………………………...………...... 1 1.4 Objectives of the Study……………………………………..………….….....2 1.5 Physiography……………………………………………….…...……………2 1.5.1 Topography……...……………………………...... …...2 1.5.2 Climate and Vegetation…...……………………...…………...……….3 1.5.3 Drainage Pattern……………...……………….……………………….3 1.6 Material & Methods……………………………………...……………..……4 1.7 Previous Work………………………………………...…..…………………5

CHAPTER ІІ: Tectonic Setting and Geology of the Area 2.1 Tectonic Setting of Khartoum Region………………………………….……6 2.2 Geology of the Area…………………………………………...... 8 2.2.1 Grey gneiss…………………………………………….....……………8 2.2.2 Microdiorite……………………………………….....…………….…..9 2.2.3 Riebeckite granite………………………..…………..……………….10 2.2.4 Felsite…………………………………………….....……………..….11

2.2.5 Quartz-syenite………………………………..……………….………11 2.2.6 Granitic pegmatite……………………..…………….………..…...…11 2.2.7 Rhyolite…………………………..……………………..…………….11 2.2.8 Nubian sediments………………..………………..………………..…12 CHAPTER ІІІ: Overview of Rock Slope Stability 3.1 Introduction……………………………………………………...... ….13 3.2 Required Data for Slope Stability Analyses……………………………...…14 3.3 Kinematical Analysis……………………………………………………….15 3.3.1 Planar Failure ………..…………….…...…………………………….15 3.3.2 Wedge Failure………………………………………………………...16 3.3.3 Toppling Failure ……………..…………………………………...….16 3.3.4 Circular Failure……………………………………………………….17 3.4 Rock Mass Failure Mechanisms …………………………………….……..17 3.5 Rock Slope Design Methods………………………………………………..18 3.6 Characterizations of Discontinuities………………………………………..18 3.6.1 Orientation…………………………………………………………...18 3.6.2 Persistence…………………………………………………………...18 3.6.3 Aperture……………………………………………………….……..18 3.6.4 Infilling materials………………………………………………....…19 3.6.5 Roughness…………………………………………………………...19 3.6.6 Frequency…………………………………………………………....20 3.6.7 Spacing and Block size……………………………………………...20 3.6.8 Discontinuity sets……………………………………………………20 3.6.9 Degree of weathering………………………………………………..20 3.7 Shear strength and deformability…………………………………………..20 3.8 Permeability and conductivity……………………………………………..20

3.9 Methods of excavation……………………………………………………...21

CHAPTER ІV: Geotechnical Investigation and interpretation 4.1 Introduction………………………………..…………….………………….22 4.2 Pre-Site Investigation (desk study) ………….…………..…………………22 4.3 Site Investigation (field work)……………………………………………...23

4.3.1 Rock Mass and Discontinuities Measurements ……...……………...... 23 4.3.2 Structure Measurements……………………………………..…………24 4.3.3 Schmidt Hummer Reading (test)……………………………………....24

4.3.4 Sample Collection……………………………….……………….……24

4.4 Laboratory Testing……………………………………………………....…24

4.4.1 Thin Section Preparation from Rock Samples……………………..….24

4.4.2 Uniaxial Compressive Strength…………………………………..……25

4.5 Geotechnical Results…………………………………………………….….26

4.5.1 Results of Field Test……………………………………………..….....26

4.5.1.1 Rock Mass Discontinuities…………………………………..…….26

4.5.1.2 Structure Measurements Tables…………………………...... …..29

4.5.2 Laboratory Test Results………………………………………...…...…30

4.5.2.1 Rock Type…………………………………………………...…….33

4.6 Tectonic Setting…………………………………………………...……..…33

VII

CHAPTER V: Data Analysis Using Kinematic Technique 5.1 Introduction…………………………………………………...... 35 5.2 Data Analysis for Sites Localities……………………...………………..….35 5.2.1 Site I: Hazrat al-sham quarry ……….……………..…………………36 5.2.2 Site II: Tana-I quarry ……………………………..………………….44 5.2.3 Site III: Tana-2 quarry ……………………………..……………...…50 CHAPTER VІ: Conclusion and Recommendations 6.1 Conclusion…………………………………………….………………...….56 6.2 Recommendations……………...... ……………………….57 References…………………………………………………….....……………..58 Appendix……………...………………………………………….…………….61

VIII

LIST OF TABLES

Table 2.1: The geological succession of the study area………………….…..…10 Table 4.1: Geological information of the three quarries………………………..24 Table 4.2: The average of dip & dip direction of joint sets...…...…………...…29 Table 4.3: Schimdt hummer reading……………………………………………30 Table 4.4: Result of uni-axial compressive strength (UCS) test…….………….32 Table 5.1: Discontinuities information in Hazrat al-sham quarry………………37 Table 5.2: Discontinuities information in Tana-1 quarry……………………….45 Table 5.3: Discontinuities information in Tana-2 quarry…………………….....51

LIST OF FIGURES

Fig. 1.1: Location map of quarries sites…………………………………..…..….2 Fig. 1.2: Physiographic map of the study area………………………………..….4 Fig. 2.1: Location map of the Sabaloka and Sileitat Es-sufur inliers in relation to Khartoum………………………………………………………...…..…8 Fig. 2.2: Geological map of Excursion 12, the Sileitat Es-sufur complexes ………………………………………………………………………..…9 Fig. 2.3: Regional geological map around the quarries site……..………….…..12 Fig. 3.1: Types of failures………………………………………..………….….17 Fig. 3.2: Illustrate the roughness profiles and corresponding JRC values...... 19 Fig. 4.1: Geological map around Es-sileitat quarries …...…………………...... 34 Fig. 5.1a: Stereographic projection at western wall…………….…………....…38 Fig. 5.1b: Stereographic projection at western wall…………….…………....…39 Fig. 5.2a: Stereographic projection at southern wall………………………...... 40 Fig. 5.2b: Stereographic projection at southern wall………………………...... 41 Fig. 5.3a: Stereographic projection at northern wall……………..…..……..….42 Fig. 5.3b: Stereographic projection at northern wall……………..…..……..….43 Fig. 5.4a: Stereographic projection at northern wall…………..…….……...….46 Fig. 5.4b: Stereographic projection at northern wall…………..……….…...….47 Fig. 5.5a: Stereographic projection at southern wall……………..………...…..48 Fig. 5.5b: Stereographic projection at southern wall……………..………..…..49 Fig. 5.6a: Stereographic projection at western wall………………..………..…52 Fig. 5.5b: Stereographic projection at southern wall……………..…….……...53 Fig. 5.7a: Stereographic projection at northeast wall………………...... 54 Fig. 5.7b: Stereographic projection at northeast wall………………...... 55

LIST OF PLATES

Plate 4.1: Aperture of joints……………………………………………….……27 Plate 4.2: Joint infilling materials………………………..……………….…….27 Plate 4.3: Roughness of joints…………………………………………….….…28 Plate4.4: Spacing of joints…………………………………….…………….….28 Plate 4.5: Schmidt hummer “L-type” ……………………………………….….29 Pate 4.6: Scan line technique……………………………………………….…..30 Plate 4.7: Photomicrogragh of rhyolite rocks…...…………….……………...... 30 Plate 4.8 Photomicrograph of olivine basalt………………...………………….31 Plate 4.9: Photomicrograph of quartz microdiorite……….…………………….31 Plate 4.10: Photomicrograph of granite……………………...…………...….....31 Plate 4.11: Examples of samples after and before Uni-axial Compressive Strength (UCS) test for the whole sites………………………...……………….32 Plate 5.1: Hazrat al-sham quarry………………………………………………..36 Plate5.2: Tana-1 quarry………………………………………………….….…..44 Plate 5.3: Tana-2 quarry………………………………………………….……..50

Abstract

Es-Sileitat area east of Khartoum State represents the main source of building materials where many companies have worked in this area to exploit and extract building materials by opening quarries. These quarries may represent a risk of unstable rock masses due to rock discontinuities. However, the properties of rock mass discontinuities play an important role in the behaviour of rock slope stability. Therefore, this study focuses on assessment of the geological hazards in Es-Sileitat quarries.

In this study the properties of rock discontinuities using Scan line technique and kinematic analysis method were used. This study is mainly based on geological observations and structural measurements. Each quarry was divided into three sites (walls) for easy study. The rock masses are characterized by three major joint sets (vertical, horizontal and diagonal). A total of 212 fractures were measured on the primary rock slopes along the discontinuity cut face and block bodies. Also, two representative intact rock samples were taken for Uni-axial compressive strength “UCS” test. DIP software had been used in this study for data analysis. The results indicate that three types of failures (plane, wedge and toppling failure) may probably occur at the three sites.

This study is recommended that for future operation the waste around quarries must be removed as well as the quarries can expand horizontally so that the heavy machines can work properly. Final recommendation is to avoid blasting technique due to the occurrence agricultural and residential lands and oil pipeline which passes through quarries.

III

المستخلص

تمثل منطقة السليتات شرق والية الخرطوم المصدر الرئيسي لمواد البناء حيث عملت العديد من الشركات في هذا المجال إلستغالل وإستخراج مواد البناء عن طريق فتح المحاجر. قد تمثل هذه المحاجر خطر ظهور كتل صخرية غير مستقرة بسبب الصخورذات الفواصل التركيبية, ومع ذلك، فإن خصائص إنقطاع الكتلة الصخرية تلعب دوراً مهماً في سلوك إستقرار منحدر الصخور. لذلك، تركز هذه الدراسة على تقييم المخاطر الجيولوجية في محاجر السليتات.

في هذه الدراسة، تم إستخدام خصائص أسطح عدم اإلستمرارية بإستخدام تقنية المسح الخطي )Scan Line( وطريقة التحليل الحركي )Kinematic(. وتستند هذه الدراسة أساساً على المالحظات الجيولوجية وقياسات التراكيب. تم تقسيم كل محجر إلي ثالثة مواقع )حوائط( لسهولة الدراسة. تتميز كتل الصخور بثالث مجموعات مشتركة رئيسية )رأسية، وأفقية وقطرية(. تم قياس 212 كسراً على المنحدرات الصخرية األولية على إمتداد واجهات الكتل الصخرية. أيضاً، تم أخذ عينتين ممثلتين للصخر السليم إلختبار قوة الضغط أحادي المحور )UCS(. تم إستخدام برنامج DIP في هذه الدراسة لتحليل البيانات. تشير النتائج إلي أن ثالثة أنواع من اإلنهيارات )سطحية، إسفينية وإنقالبية( قد تحدث على األرجح في المواقع الثالثة.

توصي هذه الدراسة بضرورة إزالة النفايات المحيطة بالمحاجر للتشغيل في المستقبل، كما يمكن أن تتوسع المحاجر أفقياً حتى تعمل اآلالت الثقيلة بشكل صحيح. التوصية النهائية هي تجنب تقنية التفجير بسبب وقوع األراضي الزراعية والسكنية وخط أنابيب النفط الذي يمر عبر المحاجر.

Chapter I Introduction

Chapter I Introduction 1.1 Research Significance The slope stability analysis is performed to assess the safety of economic design of human-made or natural slopes (e.g. embankments, road cuts, open- pit mining, excavations, landfill) and the equilibrium conditions. The term slope stability may be defined as the resistance of inclined surface to failure by sliding or collapsing. The main objectives of slope stability analysis are finding endangered areas, investigate the potential failure mechanism, determine the slope sensitivity to different triggering mechanism, design optimal slopes with regard to safety, reliability and economics, design possible remedial measures, e.g. barriers and stabilization mechanism.

1.2 Statements of Problem Es-Sileitat area east of Khartoum State, Sudan considered as oldest quarry in Khartoum state, which represents a source of high quality building materials (e.g. fine and coarse aggregate). Many companies have opened quarries in this area to exploit and extract building materials. These materials are used for several engineering constructions such as Al Tahadi Road and Jabel Oliya Dam in south of Khartoum. Some of these quarries reached deep depths which may represent a risk of unstable rocks due to the rock discontinuities. In addition oil and gas pipelines pass near these quarries which may pose to natural hazard such as earthquakes and floods.

1.3 Location and Accessibility The Es-Sileitat area is located north east of Khartoum city, Sudan. It is about 30 Km from Khartoum railway station between longitudes 32.690024ᵒ & 32.69830ᵒE, and latitudes 15.910105ᵒ & 15.905948ᵒN. The area can be

Chapter I Introduction reached by Ring Road and access to quarries with 4.5km near to Es-Sileitat area (Fig.1.1).

Fig. 1.1. Location map of quarries sites 1.4 Objectives of the Study This study focuses on assessment the probability of geological hazards of some selected quarries around Es-Sileitat area. The main objective is to determine the influence of geological and geotechnical properties of hazardous unstable zones by identifying the nature and characteristics of discontinuity surfaces.

1.5 Physiography 1.5.1 Topography The study area is mostly flat which is predominated the entire area with few isolated sedimentary and basement outcrops (Es-Sileitat and Sufur) at the north eastern part of the area. The average elevation varies between 384 and 415 meters above sea level. The surface plain rising is gradually slope to the Blue River Nile (Fig.1.2).

Chapter I Introduction

1.5.2 Climate and Vegetation Khartoum region extend from latitude 15° 10’ N to 16° 30’ N placing it in climatic terms on the southern edge of the Sahara climatic zone. There are four seasons during the year. The winter season is covering the period mid- November to March. By the end of March daily mean maximum temperature is 40° C and the hot dry season. By the quintile (5-day period) beginning 23 may the temperatures reach 44.1° C and odd days with temperature over 45° C might be expected. The weather stays dry until the end of June, throughout the period from March to June relative humidity remains, below 30%. On relatively infrequent occasions showers occur as early as April or May, but in many years it is in June before precipitation is noted. The sun passes overhead at Khartoum on May. The beginning of this process is further encouraged by increasing cloud, high humidity’s, and occasional rainstorms. The change of rain decreases markedly after mid-September. Average rainfall reaches 100–200 mm in the north- eastern areas and 200–300 mm in the north western areas. The savanna vegetation type covered the study area which its intensity increased after the flooding periods. Savanna vegetation type such as acacias, shrubs recognized seven principle type of vegetation in Sudan (Andrew 1948). The types of acacia trees are sidir, tundub, oshar, and ark. Most of them grow along seasonal wadi and khors.

1.5.3 Drainage Pattern The main wadi in the study area is represented by Blue Nile with many second and third order perennial streams connected to the River Nile. The Blue Nile is the major natural drainage features in the study area. Moreover, Wadi and khor mainly trend east-west. The Wadi appear to be structurally controlled by east west Lineaments. These wadies are seasonal water courses. They drain into the Blue Nile with a regional parallel pattern, such as Wadi Soba and Wadi El Selite. These Wadies supply a great deal of

Chapter I Introduction water during autumn. Most of these Wadies are filled by clay silt and sand during the flooding period (Fig.1.2).

Fig .1.2. Physiographic map of the study area 1.6 Material & Methods In this study the geotechnical site investigation divided into three stages: Office Work: Satellite images for geological site investigation were prepared using landsat-8 and Digital Elevation Model (DEM). Different digital image processing techniques were applied to get more information about the study area. Field Work: was accomplished in one field trip which spends about four days. The field data include lithological information, structural measurements and samples collection. Laboratory Experiments and Data Analysis: six samples were collected for Petrographic studies (thin sections) to help in understanding the geology of study area, and laboratory experiments to help in knowing the geotechnical

Chapter I Introduction properties of rocks. The processing techniques, laboratory experiments and data analysis will be discussed in details in chapter four.

1.7 Previous Work A numerous published and unpublished reports, researches and paper were carried out to evaluate the ground water in east of the Nile at Khartoum state. They focused mainly about water sources and water quality and description of the rock units as well as on the structural features. They have described various aspects of geology, hydrogeology, and hydrochemistry of the aquifer system. The first comprehensive studies in the above-mentioned aspects were conducted by Delany (1953). She was compiled a geological map of eastern Khartoum province on scale 1:250, 000. Ahmed (1968) carried out study on some of igneous complexes notable jebel Qeili and jebel Slitat–Es-sufur and built upon the earlier work of Delany. El Bushi (1972) was studied the hydrology of the area east of the Blue Nile between Khartoum and Takalat. In (1970) Dawaud made geologically and geophysical studied of the area south east Qerri station. Haggaz and khirealla (1987) studied the aspect of recharge to the Nubian aquifer system near the confluence of Blue Nile and withe Nile using isotopes and water chemistry techniques. El dawi (1997) gave detailed geophysical work in east of the river on which she divided the area into two basins and named Harira and Kabashi basins. Ahmed et al. (2000) describe the water quality in Khartoum area for several ground water samples in the east of the Nile and Blue Nile. Saad (2001) studied the geology, structure and geometry of the Khartoum basin in the north eastern periphery using remote sensing and geophysical methods. Abdellatife Elsayed (2005) provided a simulation of groundwater potential in the area east of the Nile of Khartoum State. Eltayeb (2015) studied the ground water occurrence and water quality characteristics in the eastern Blue Nile area. In engineering geology field there are a limited studies carried out in the area.

Chapter II Tectonic Setting and Geology of the Area

Chapter II

Tectonic Setting and Geology of the Area

2.1 Tectonic Setting of Khartoum Region: The Es-Sileitat Es-Sufur igneous complex lays on the eastern side of the River Nile approximately 30km of Khartoum and half-way between to the Sabaloka complex. From figure (2.1), Es-Sileitat Es-Sufur lies outside to southern margin of the main Sabaloka inlier and comprises two isolated complexes, each within its own small inlier, surrounded by Nubian sediments. This outcrop pattern indicates that the resistant rocks of the two complexes already formed low hills before the Nubian rivers of the late Cretaceous washed sediments around. As elsewhere at Sabaloka, we see an advanced stage on the exhumation of a pre-Nubian landscape which was evidently similar in many ways to that of the present day. 2 The two inliers together cover a total area of about 60 km . The more southerly is almost entirely occupied by riebeckite granite of the Sileitat pluton. The oval outcrop of which measures 9 x 6 km. The northerly outcrop, around Jebel Es-sufur, measures 6 x 4 km and exposes syenite, rhyolite, diorite and granite pegmatite. In both inliers, patches of Basement grey gneiss define parts of the outer limits of the igneous intrusions, but in general, contacts are poorly exposed both within and bordering the complexes. Most of them are being covered by either Nubian sandstones or recent superficial deposits. Because of their alkaline affinities and the nature relationships towards the basement gneisses and Nubian sandstones, it has never been doubted, since the work of Delany (1952, 1958), that the Es-Sileitat Es-Sufur complexes were members of the family of granites and syenites which we nowadays call the younger granite association. Consequently, Es-Sileitat Es-Sufur has been

Chapter II Tectonic Setting and Geology of the Area generally regarded as a close relation of the two Sabaloka igneous complexes. Nevertheless, recent geochronological work in several regions of Sudan has revealed surprisingly large age spreads of the Younger granites, even between complexes close together and of apparently similar petrogenesis. At Es- Sileitat Es-Sufur, the K-Ar determinations of Brook and Rundle (1974) and Rb-Sr data of Klemenic (1987) together suggest a middle Jurassic age for these rocks, which are thus about 200 million years younger than the Cauldron complex at Sabaloka and 300 million years younger than the Tuleih complex. There remains some doubt as to the relative age of the Es-Sileitat and Es-Sufur plutons. Mutual contact relations are nowhere clearly seen, although Ahmed (1977) considered the Es-Sufur complex to be the younger on the grounds that it was nowhere transected by the kind of felsite dykes found in places cutting the Es-Sileitat granite. However, there are only a few of these dykes, so the evidence is not strong. More precise isotope dating may eventually provide the answer. The two complexes outcrop in a series of low jebels and rock slabs rising above a dusty plain eroded across Nubian sediments and carrying a superficial skimming of sand, gravel and Nile silt (Table.2.1). The best exposures of the Es-Sileitat granite are in quarries, since this rock has been exploited as a source of building stone and crushed aggregate.

Chapter II Tectonic Setting and Geology of the Area

Fig. 2.1 Location map of the Sabaloka and Sileitat Es-sufur inliers in relation to Khartoum by David C. Almond & Farouk Ahmed 1993

2.2 Geology of the Area: The main rock types encountered in the area are described below in general order from older to younger.

2.2.1 Grey gneiss These rocks generally display a weak foliation striking about N-S, and are composed of microcline, a little plagioclase, quartz and biotite. Garnet is found locally. They are thus similar to the unmigmatized gneisses of the main inlier.

Chapter II Tectonic Setting and Geology of the Area

2.2.2 Microdiorite This highly-jointed, dark-grey, porphyritic rock contains phenocrysts of plagioclase, orthoclase and orthopyroxene. The fine-grained groundmass is a granular aggregate of feldspar, pyroxene and a little hornblende.

Fig. 2.2: Geological map of the Sileitat Es-sufur complexes by David C. Almond & Farouk Ahmed 1993

Chapter II Tectonic Setting and Geology of the Area

Table 2.1: The geological succession of the study area

2.2.3 Riebeckite granite This rock has a quite variable petrography but the commonest type is a pale- grey, medium-grained rock composed of perthite, interstitial quartz and sparse sodic amphibole and pyroxene. Pegmatitic segregation from patches is containing sodic amphiboles up to 4 cm long. Locally the granite contains a weak foliation, though to be inherited from dioritic xenoliths.

Chapter II Tectonic Setting and Geology of the Area

2.2.4 Felsite Dykes of felsite cut the grey gneisses and Sileitat granite and are exposed as low, boulder-strewn ridges. They are in places brecciated by post-Nubian faulting. The rocks contain phenocrysts of quartz and feldspar, and matrix is often weakly flow-banded.

2.2.5 Quartz-syenite This rather variable rock is one of the major components of the Es-Sufur pluton, and forms massive exposures rising above the adjacent rhyolite outcrops. Pink to buff in colour, the rocks are very similar in general appearance to the Sileitat granite but contain a lower content of quartz. Nevertheless, some varieties contain enough quartz to be classified as granites. Although both sodic amphibole and aegirine are present, the latter mineral is more common in the syenitic varieties.

2.2.6 Granitic pegmatite The granite pegmatite forms boulder outcrops similar in composition to alkaline granitic rocks, but they are coarse-grain. Dark minerals include a brown hornblende, clinopyroxene and riebeckite.

2.2.7 Rhyolite There are two distinct ages of rhyolite in the Es-Sufur complex, but these are distinguished mainly by their field relations, and both are dark-coloured, flow-banded, porphyritic rocks which contain aegirine as their chief dark mineral. The early rhyolite appears to have been extensive and once covered most of the area now occupied by later intrusions. The late rhyolite occurs within fracture zones and was probably erupted along fissures. Subsequent gaseous activity locally fractured the rhyolites and their wall-rocks to produce explosion breccia.

Chapter II Tectonic Setting and Geology of the Area

2.2.8 Nubian sediments The Nubian sediments rest unconformably upon the Basement gneisses and igneous complexes, surrounding and in places preserved as small patches overlying the igneous rocks. Evidently, then, the usual pebble conglomerate and poorly sorted sandstone, with siliceous and ferruginous cement.

Fig. 2.3. Regional geological map around the quarries site modifying (GRAS, 2008)

Chapter ІІІ Overview of Rock Slope Stability

Chapter III Overview of Rock Slope Instability

3.1 Introduction Due to the increasing demand for engineered cut and fill slopes on engineering construction projects, the need to understanding analytical methods, investigative tools, and stabilization methods to solve slope instability problem has also increased. Applying Slope instability principles requires comprehending the geology, hydrology, and rock properties, this involves constructing models that accurately represents sites subsurface conditions, ground behaviour and applied loads. Mostly, the main purpose of slope instability analysis is creating safe and economic design of excavation, embankments, earth dams, landfills and spoil heaps. Slope instability assessment is concerned with identifying critical geological, material, environmental and economic parameters that affect the project along with understanding the nature, magnitude and frequency of potential slope problems. Consequently, assessing the analysis results requires acceptable risk or safety factors judgment must be made (Abramson et al. 2002). Changes in topography seismicity, groundwater flows, loss of strength, stress changes and weathering can cause naturally slopes to suddenly fail, so understanding them is must (Abramson et al. 2002). In the other hand, engineering slopes may be considered in three main categories; embankments, cut slopes and retaining wall. In civil engineering project deep and shallow cuts are essential, so slope design is performed in order to determine a height and inclination, which is economical and that will remain stable for a reasonable life span (Abramson et al. 2002). So the factors such as the purpose of the cut, geological conditions, insitu material properties, seepages pressures, construction methods and potential occurrence of natural phenomena such as heavy precipitation, flooding erosion, freezing and earthquakes should be considered (Abramson et al. 2002). Slope failures are

Chapter ІІІ Overview of Rock Slope Stability often caused by processes that increase shear stresses or decrease shear strength of the rock mass pre-existing discontinuities can weaken residual soil and weathered bed rock, however, faults, bedding surface, cleavages and foliations are the most influence pre-existing discontinuities (Abramson et al. 2002).

Open pit quarry can be defined as the process of excavating any near-surface ore deposit by means of an excavation or cut made at surface, using one or more horizontal benches to extract the ore while dumping overburden and tailings at a dedicated disposal site outside the final pit boundary (Hartman, 1992). Open pits account for the major part of the world’s mineral production due to being large scale, high productivity and high effectiveness. Along with an increase in mining operations, the depth of open pit mines is getting deeper causing slope stability problems and safety issues.

3.2 Required Data for Slope Stability Analyses The data required for performing slope stability analyses includes geological conditions, site topography, material properties (soil), shear strength, ground water conditions and seismicity (Abramson et al. 2002).

Basic geological features that could affect the stability of slopes include:

Slope material fabric, Mineral orientations and stratification, Discontinuities and bedding planes, Geological anomalies, Degree of weathering, Groundwater, and History of previous landslides, and in situ stresses. Site topography is an over clue to past landslides and potential instability (Abramson et al. 2002). Soils particulate hold liquids (water), or gas (air), or both so understanding it is a fundamental part for slope stability analysis. There are two types of shear strength used in stability analyses those are: the undrained shear strength, and the drained shear strength. Undrained shear strength is used in total stress analyses, whereas drained shear strength is used in effective stress analyses. Besides gravity, groundwater is the most

Chapter ІІІ Overview of Rock Slope Stability important factor in slope stability (Abramson et al. 2002). Groundwater can affect slope stability in five ways; it reduces strength, changes the mineral constituents through chemical alteration and solution, changes the bulk density, generates pore pressures and causes erosion (Abramson et al. 2002). Seismicity creates a type of transient dynamic loading which instantaneously increases the shear stresses in a slope and decreases the volume of voids within the materials of the slope, leading to an increase in the pressure of fluids (water) in pores and fractures. Factors affect the response of slopes during earthquakes include: Magnitude of the seismic accelerations, Earthquake duration, Dynamic strength characteristics of the materials affected, and Dimensions of the slope. After an earthquake a slope may be stronger, weaker, or the same as before (Abramson et al. 2002).

3.3 Kinematical Analysis Kinematic analysis is a useful method to investigate the possible structurally controlled slope failure modes examining the sliding direction by stereographic projection. Kinematic is described as the motion of bodies without reference to the forces that cause them to move (Goodman, 1989). Maximum safe slope angle can be estimated based on the basic failure modes such as planar failure, wedge failure and toppling failure. The analysis is conducted by using the orientation of discontinuities and the slope generally in terms of dip and dip direction (Goodman, 1989).

Failures primarily rely on the orientation, shear strength and water pressure conditions of the discontinuities in the mass and can be accurately determined by means of proper site investigations and relevant field data. Planar failure, wedge failure and toppling failure are the most widely observed structural failure modes (Simmons & Simpson, 2006).

3.3.1 Planar Failure Planar Failure occurs when a rock block slides along a discontinuity plane which dips out of the slope face. Most of the failure takes place by tension

Chapter ІІІ Overview of Rock Slope Stability crack formed at the slope crest (Fig.3.1a). General conditions for plane failure are;

1) Dip of the planar discontinuity must be within 20 degrees of the dip direction of the slope face, 2) Dip of the planar discontinuity must be within 20 degrees of the dip direction of the slope face, 3) Dip of the planar discontinuity must be within 20 degrees of the dip direction of the slope face, 4) Lateral extent of the potential failure mass must be isolated by lateral release surfaces which free a block for sliding. Because under these conditions there will be an increasing thickness of intact rock at one end of the block which will have sufficient strength to resist failure.

3.3.2 Wedge Failure Wedge failure occurs in which at least two discontinuities intersecting each other and daylights in slope face. Due to the geological and geometrical aspects, wedge failure is more frequently seen than planar failures in rock slopes (Fig.3.1b). Kinematic conditions for the occurrence of wedge failure are:

1) Trend of the line of intersection must be similar to the dip direction of the slope face, Plunge of the line of intersection must be less than the dip angle of the slope face, and 2) Plunge of the line of intersection greater than the angle of friction of the failure plane. 3.3.3 Toppling Failure: The dip direction of the discontinuities dipping into the face must be within about 10º of the dip direction of the face so that a series of slabs are formed parallel to the face (Fig.3.1c). There are conditions causing this type of failure:

Chapter ІІІ Overview of Rock Slope Stability

1) Strike of the layers must be approximately parallel to the slope face, differences in these orientations of 20 degrees or less, 2) Dip of the layers must be steeply into the slope face, and 3) Discontinuity condition must satisfy the following equation: (90º – Ψp (dip of angle) + фp (friction angle along plane)] ≤ Ψf (dip of slope face) (Goodman and Bray, 1976). 3.3.4 Circular Failure:

Circular failure occurs when rock masses are associated with highly fractured, highly weathered, decomposed of very weak material along circular slip paths, vertical tension crack occurs in the upper surface or in the face of the slope; and fully saturated or dry rock mass (Fig.3.1d).

Fig.3.1: Types of failures; (a) Plane failure, (b) wedge failure, (c) Toppling failure, and (d) Circular failure(Wyllie and Mah, 2004).

3.4 Rock Mass Failure Mechanisms Circular failure generally occurs in highly weathered or closely jointed rock masses. The failure surface is mostly in the form of circular shape by developing the line of least resistance path through the slope. This type of failure is not controlled by structural geology for stability and takes place when the individual particles in a rock mass are very small compared with the size of the slope (Wyllie and Mah, 2004). Moreover, formation of tension

Chapter ІІІ Overview of Rock Slope Stability crack behind the slope crest is commonly possible in which the sliding surface extends to the toe of the slope.

3.5 Rock Slope Design Methods The purpose of design methods for rock slopes is basically to determine and predict whether or not failure occurs. In fact, they are intended to determine when the acting stress on a slope exceeds the strength of the rock mass. Various methods were proposed for the design analyses, including kinematic analysis and empirical design methodology, limit equilibrium methods and numerical modelling analysis.

3.6 Characterizations of Discontinuities The following characterizations of discontinuities are mainly based on

International Society of Rock Mechanic (ISRM) procedure which are consist of orientation, persistence, aperture, infilling materials, roughness, frequency, spacing and block size, discontinuity sets, degree of weathering, shear strength and deformability, Permeability and conductivity.

3.6.1 Orientation: It is measured by outcrop mapping by geological compass which gives amount of dip angle and direction or trend and plunge. Also could be measured by core and borehole logging.

3.6.2 Persistence: the extent of the discontinuity in its own plane, and classified to: very low (<1m), low (1-3m), medium (3-10m), high (10-20m), and very high (>20m).

3.6.3 Aperture: The perpendicular distance between the adjacent rock surfaces of the discontinuity that is classified to: very tight (<0.1mm), tight (0.1-0.25 mm), partly open (0.25-0.5 mm), open (0.5-2.5 mm), widely open (2.5-10 mm), very widely open (1-10cm), extremely widely open (10-100cm), and cavernous (>1 m).

Chapter ІІІ Overview of Rock Slope Stability

3.6.4 Infilling materials: weathered materials which fill the opening between discontinuity surfaces. It may consist of calcite, epidote, quartz, gypsum, chlorite, talc, graphite, serpentine, in-active clay, swelling clay, and sand. Sometimes they are clean without filling materials or coatings.

3.6.5 Roughness: joint is an interface of two contacting surfaces and may be defined either by reference to standard charts or mathematically. Depend on ISRM standard the roughness of discontinuities is firstly described in meter scale (step, undulating, and planar) and then in centimeter scale (rough, smooth, and slickensides). Another famous classification is proposed by (Barton and Choubey 1977), which termed as Joint Roughness Coefficient (JRC) that is ranging from smooth surface (0) to very rough surface (20) (Fig.3.2).

Fig. 3.2: Illustrate the roughness profiles and corresponding JRC values (Barton and Choubey 1977).

Chapter ІІІ Overview of Rock Slope Stability

3.6.6 Frequency: It is the number of discontinuity occurring within a base length or core run (per m or f). Therefore, simply the inverse of joint spacing (Sj) is: λ = I/Sj.

3.6.7 Spacing and Block size: It is the distance between adjacent discontinuities Intersections with the measuring scan line. Generally, they are classified to: extremely close spacing (<0.02m), very close spacing (0.02- 0.06m), close spacing (0.06-0.2m), moderate spacing (0.2-0.6m), wide spacing (0.6-2m), very wide spacing (2-6m), and extremely wide spacing (> 6m). When a rock mass contains more joints numbers, the joints have lower average spacing and smaller block size and vice versa. Block size can be classified by the volumetric joint count (Jv), (number of joint/ m3 volume of rock mass): very large (<1), large (1-3), medium (3-10), small (10-30), very small, (>30), and crushed rock (> 60).

3.6.8 Discontinuity sets: Discontinuities may orient in a random or preferred direction and may occur in one or more sets.

3.6.9 Degree of weathering: The susceptibility of rock to weathering depends on: mineralogical contents, permeability, cohesion, fracture spacing, ground water, and climatic condition. In general, if the temperature and rain fall decreased the weathering also decreased from strong to very slight and the weathering type follow it. Depend on the weathering grade classified the rocks into: fresh rock, slightly, moderately, highly, completely weathered, and residual soil.

3.7 Shear strength and deformability: This depend on the size of aperture and type or properties of filling materials, for example: Open or filled joints with large apertures have low shear strength, if the filling materials are talc make discontinuities very slippery.

3.8 Permeability and conductivity: the flow of fluid through a fractured rock mass is no exception, as it will depend on: fractures aperture, normal

Chapter ІІІ Overview of Rock Slope Stability stress and depth below the ground surface this affected onto fractures and rock mass and thus effected in mechanical behaviour of rocks.

3.9 Methods of excavation: used to cut the slope, and lead to the irregularity face as a result of poor blasting technique.

Chapter IV Geotechnical Investigation and Interpretation

Chapter IV Geotechnical Investigation and interpretation

4.1 Introduction

Geotechnical site investigation is an understanding to the surface & subsurface conditions and properties of soils and rocks that are required for the proper location, planning, foundation design, construction, operation and maintenance of engineering structures. The objectives of site investigation are: to evaluate those geologic, seismologic, and soils conditions that affect the safety, cost effectiveness and design of a proposed engineering structure during the various stages of development (Davis 2001).

The selection methods of geotechnical investigations are based on many factors such as nature of subsurface materials and groundwater conditions, size of structure, purpose of the investigation “e.g., evaluate stability of existing structure, design a new structure”, topographic constraints, difficulty of application, degree to which method disturbs the samples or surrounding grounds, budget, time and political constraints, environment requirements/ consequences.

According to general strategy of site investigation this study followed the well- known sequence to achieve the objective of this research. These stages include pre site investigation (desk study), site investigation (field data collection), and post site investigation (data analyses & interpretation).

4.2 Pre-Site Investigation (desk study)

Recently, the techniques of remote sensing and GIS represent very important tool in such engineering geological problems, evidence of previous slope failure and potential hazards (volcanoes, landslides and earthquakes), geological

Chapter IV Geotechnical Investigation and Interpretation structure, groundwater conditions, types of soils and rocks and slope stability (Gupta 2003).

In this study Landsat-8 were used as a geological base map. On the other hand, digital elevation model (DEM) was used to explain the topographical variations along the quarries.

In this study ENVI 4.8 software was used for the processing of Landsat images data and produce suitable images for geological information, While, ArcMap10.3 was used to digitize the lithological units, lineaments and create the final regional geological map, lineament map and drainage map. Finally, all available factors are entire in a geo-database and later use one of the geological engineering software’s such as: dip, phase2, and rock fall simulation program for the impact of falling rocks on the quarries. 4.3 Site Investigation (field work)

Site investigation aimed to understand the geological and geotechnical properties of rock masses and their discontinuities that are controlling the slope instability in the study area. Site investigation include geological mapping of the quarries sites, collection of hand specimen samples for petrographic studies, structural measurements “dips/dip directions for joints and trend and plunge of faults” to prepare a detailed structural map and general characteristic of discontinuity surfaces. Field investigation was done to understand the geotechnical properties of rock masses and their discontinuities that are controlling the slope stability in the study area. This work was accomplished in one field trip, which spent four days during November 2017.

4.3.1 Rock Mass and Discontinuities Measurements

The work was started by geological mapping for the quarry area. Afterwards study area of quarries has been divided into three sites (walls) for easy work as

Chapter IV Geotechnical Investigation and Interpretation shown in (Table.4.1). Three sits were selected for investigation, namely the Hazrat al-Sham quarry (site-1), the Tana-1 quarry (site-2), and the Tana-2 quarry (site-3). In order to map the discontinuities along the cut faces (walls) the technique of scanline was adopted (Plate.4.6).

Table 4.1: Geological information of the three quarries Sites Lat/Long Type of rock Cut face Wall Intersecti length on angle (dº/ddº) (º) (m)

Hazrat al-Sham 15º54ʹ 18.0ʺN Granite 75/250 9 70 32º 45ʹ53.3ʺE

Tana -1 15º54ʹ 35.3ʺN Rhyolite 75/250 8 80 32º41ʹ47.4ʺE Tana -2 15º54ʹ 33.1ʺN Quartz micro- 75/250 9 75 32º41ʹ 45.2ʺE diorite

4.3.2 Structure Measurements

A total of 212 fractures were measured on the primary rock slopes.

4.3.3 Schmidt Hummer Reading (test)

Schmidt hummer readings to determine the strength of the rock (Plate4.5), (Table4.3). 4.3.4 Sample Collection

Nineteen representative rock samples were taken from the main lithological units for thin-sections and laboratory experiments.

4.4 Laboratory Testing

4.4.1 Thin Section Preparation from Rock Samples

Thin sections were prepared from various rock samples, at the laboratories of Al Neelain University in Khartoum. They have been studied under the polarizing microscope.

Chapter IV Geotechnical Investigation and Interpretation

4.4.2 Uniaxial Compressive Strength

Six representative rock samples were taken from the different rock masses from three sites quarries for uni-axial compressive strength (UCS) (cubic 5*5) test to determine the mechanical behavior of the rocks, identify the strength of the rocks, deformability and to understanding which type of failure can be occur. However, the uniaxial compressive strength is available and unexpansive mechanical test for such research. identify the deformability and strength of the rocks, also to calculate friction angle values of different rocks. The friction angle is used to understand which type of failure can be occurred.

i. Test Procedures and Methods

The procedure and methods for the analyzed was done follow the ASTM standard (D 2938). A rock cube sample was cut to length and the ends are machined flat. The specimen was placed in a loading frame and heated to the desired test temperature. Axial load was continuously increasing on the specimen until peak load and failure are obtained. The lower platen was placed on the base or actuator rod of the loading device. The bearing faces were cleaned of the upper and lower platens and of the test specimen, and place the test specimen on the lower platen. 100 N load was applied to the specimen Placed by means of the loading device to seated the bearing parts of the apparatus. Axial load was applied continuously and without shock until the load became constant, reduced, or a predetermined amount of strain is achieved. Applied the load to produce either a stress rate or a strain rate as constant as feasible throughout the test. Do not permit the stress rate or strain rate at any given time to deviate by more than 10 percent from that selected. The stress rate or strain rate selected should be that would produce failure in a test time between 2 and 15 min (Plate.4.11), (Table.4.4).

Chapter IV Geotechnical Investigation and Interpretation

4.5 Geotechnical Results

4.5.1 Results of Field Test

4.5.1.1 Rock Mass Discontinuities

Determine the properties of the discontinuities for outcrops and existing cuts that might affect the strength of the rock mass. These properties are:

i. Orientation: (dip angle / dip direction or trend / plunge) (dip (d) / dip direction (dd.) of joints): These joints represent the all joint sets (set-1, & set-2 vertical/diagonal, and horizontal respectively) (Table.4.2).

ii. Aperture: The average of the aperture for different joint sets of the rock masses are ranging from open to very widely open and extremely widely open in Hazrat al-Sham sites and Tana-1 sites, in Tana-2 sites aperture is widely open (Table.4.2), (Plate.4.1).

iii. Infilling materials: the interface can also be filled with intrusive or different weathered materials, and there are many types of materials in Hazrat al-Sham sites there are many types of materials such as: rock fragment, clay, iron oxide, basic dyke (basalt), cement, and clean. Tana-1 sites the material is: epidote, iron oxide, cement, and rock fragment. In Tana-2 filling by: iron oxide, clay, epidote, basic dyke (basalt), and silica (Plate.4.2).

Chapter IV Geotechnical Investigation and Interpretation

Plate. 4.1. Aperture of joints, (a) open and very widely open, (b) widely open, and (c) very widely open

Plate. 4.2: Joint infilling materials, (a) clean joint, (b) clay filling, (c) rock fragment, (d) rock fragment and clay filling, and (e) basalt filling.

Chapter IV Geotechnical Investigation and Interpretation

iv. Roughness: The surface of the most discontinuities is characterized by different forms of roughness in Hazrat al-Sham, Tana-1, and Tana-2 sites (undulating, planner, rough, and smooth) (Plate.4.3).

Plate. 4.3: Roughness of joints, (a) planner smooth, (b) undulating-rough

v. Joint Spacing and Block size:

The average joint spacing of the rock masses for Hazrat al-Sham sites is moderate spacing (0.2-0.6m). Tana-1 sites are ranging from close (0.06-0.2m), moderate (0.2-0.6m), and wide spacing (0.6-2m). Tana-2 is ranging from moderate (0.2-0.6m) to wide spacing (0.6-2m) in different joint sets (Table.4.2), (Plate.4.4).

Plate. 4.4. Spacing of joints, (a) vertical joints, horizontal joints, (b) diagonal joints

Chapter IV Geotechnical Investigation and Interpretation

vi. Rock Strength: Usually, all above factors affect the strength of the rock mass. In situ hardness test of rock masses were conducted by using

Schmidt hummer “L-type” (Plate.4.5) which collected from the whole sites and the all hits are perpendicular (horizontal) to the wall and the average measurements are recorded in the following (Table.4.3).

4.5.1.2 Structure Measurements Tables

Table 4.2. The average of dip & dip directions of joint sets

Sites Hazrat al-Sham Tana -1 Tana -2

No of Walls 1 2 3 4 5 6 7 8 9 10

Orientation Set1(dº/ddº) 73/250 80/260 70/250 50/230 81/260 82/262 13/193 83/263 81/261 70/250

Set2(dº/ddº) - 22/200 20/200 - 43/223 20/198 - 05/185 48/228 18/198

Aperture(mm) 92 4 8 2 27 2 7 26 3 4

Joint Set-1( m) 0.83 0.83 0.54 0.59 0.93 0.76 0.22 2.82 0.54 0.74 spacing Set-2 (m) - 0.45 0.59 0.24 0.58 0.15 - 0.92 0.48 -

Hardness(MPa) 36 28 42 33 34 31 35 38 24 19

Plate. 4.5. Schmidt hummer “L-type”

Chapter IV Geotechnical Investigation and Interpretation

Table 4.3. Schimdt hummer reading Sites Hazrat al-sham Tana-1 Tana-2 Hardness (Mpa) 36 28 42 33 34 31 35 38 24 19

Plate 4.6: Scan line technique; horizontal scan (vertical joints).

4.5.2 Laboratory Test Results

Plate.4.7: Photomicrograghs of rhyolite rocks (A “ppl” and B “xpl”)

Chapter IV Geotechnical Investigation and Interpretation

Plate.4.8: Photomicrographs of olivine basalt (A “ppl” and B “xpl”)

Plate.4.9: Photomicrograph of quartz microdiorite (A “ppl” and B “xpl”)

Plate.4.10: Photomicrographs of granite (A “ppl” and B “xpl”)

Chapter IV Geotechnical Investigation and Interpretation

Plate. 4.11. Examples of Uni-axial Compressive Strength (UCS) test for the whole sites “after and before test”

Table 4.4: Result of uni-axial compressive strength (UCS) test Code Area Load Correction Load * Correction UCS UCS (cm2) Factor (Ton) Factor (g/ cm3) MPa (g)

1 25 850 1.045 888.25 35.53 3.48 2 25 14000 1.045 14630 585.2 57.39 3 25 31200 1.045 32604 1304.16 127.89 4 25 31000 1.045 32395 1295.8 127.07 5 25 31000 1.045 32395 1295.8 127.07 6 25 41000 1.045 42845 1713.8 168.66

Chapter IV Geotechnical Investigation and Interpretation

4.5.2.1 Rock Type

The rocks secession of the study area is composed of (from older to younger): i. Volcanic Rocks

The extrusive rocks of Es-Sileitat are mainly consisting of acid volcanic rocks such as rhyolite, trachyte and ignimbrite.

Rhyolite occupying limited area. Petrographicaly, it is dark color, flow banded, porphyritic which contains aegirine as chief dark mineral (Plate.4.7).

Olivine basalt founds as dykes in Jebel Es-Sileitat surrounded by younger granite. The rock is dark color, porphyritic and consists of plagioclase, titanaugite pyroxene and olivine. Olivine is mainly altered to iddingsite and quartz crystals obtain fracture filled by oxide minerals (Plate.4.8).

ii. Granite Intrusion The quartz microdiorites are situated towards northeast of Es-Sileitat, and they were crossed by felsic dykes. Petrographicaly, they are porphyritic which contains phenocrysts of plagioclase, orthoslase and orthopyroxene. The fine grained groundmass is a granular aggregate of feldspar, pyroxene and alittle hornblende, and allotriomorphic texture (Plate.4.9).

Es-Sileitat granite shows boulder outcrops of post-orogenic intrusion similar in composition to alkaline granite. Microscopically it is a quite variable petrography but the commonest type is a pale grey, medium grained rock composed of perthite, interstitial quartz and sparse sodic a mphibole and pyroxene (Plate.4.10).

4.6 Tectonic Setting

A number of small faults of post-Nubian age affect the igneous complexes and trend E-W and N-S. They often follow felsite dykes which are marked by felsite breccia, slickensides and shattering, with silicification of the adjacent sandstones

Chapter IV Geotechnical Investigation and Interpretation

(Fig.4.1). The structure of the quarries is highly jointed with an irregular and very steeper vertical and horizontal that can cause rock fall.

Fig.4.1: Geological map around Es-sileitat quarries