Determination of Lateral Stresses in Boom Clay Using a Lateral Stress Oedometer

DETERMINATION OF LATERAL STRESS IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Determination of Lateral Stresses in Boom Clay using a Lateral Stress Oedometer

Mendoza, Ruena Cordero March, 2004

I DETERMINATION OF LATERAL STRESS IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Determination of Lateral Stresses in Boom Clay using a Lateral Stress Oedometer

Ruena Cordero Mendoza

Thesis submitted to the International Institute for Geo-information Science and Earth Obser- vation in partial fulfilment of the requirements for the degree of Master of Science in Earth Resources and Environmental Geosciences with specialisation on Geological Engineering

Thesis Assessment Board

Dr. H.R.G.K. Hack (Chair) (ITC) L.F. Gareau , M.Sc. (supervisor1) (TUD) Ir. W Zigterman (supervisor 2)(ITC) Dr. ir. D.J.M. Ngan-Tillard (TUD) Ir. M. Huisman (ITC) Ir. H.L. Jansen (Fugro)

INTERNATIONAL INSTITUTE FOR GEO-INFORMATION SCIENCE AND EARTH OBSERVATION ENSCHEDE, THE NETHERLANDS

II DETERMINATION OF LATERAL STRESS IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

I certify that although I may have conferred with others in preparing for this assignment, and drawn upon a range of sources cited in this work, the content of this thesis report is my original work. Signed …………………….

Disclaimer

This document describes work undertaken as part of a programme of study at the International Institute for Geo-information Science and Earth Observation. All views and opinions expressed therein remain the sole responsibility of the author, and do not necessarily represent those of the institute.

III DETERMINATION OF LATERAL STRESS IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Acknowledgement

My study in ITC has been molding my professional life, it has not only molded my academic interest but as well as my total being. It is interesting to be in Geological Engineering group in Earth Resources and Environmental Sciences. It was nice staying in ITC Enschede for five months, with such a very short stay there, it had been so fruitful and worthwhile. I learned and broaden my knowledge about GIS and Remote Sensing. I was able to learn other cultures that are very different from the culture that I grow up with. For my stay here in ITC Delft, it had been so rewarding to learned many things and tighten up the ties among us here in ITC (Delft) as well as with TUDelft staffs and students. This opportunity to study and broaden my knowledge about life could not be materialize if not for the people who supported me all throughout this life changing experience. For the people who have been supportive to for this study, my heartfelt gratitude to all of you: To the University of San Carlos (Cebu, Phils) most especially to my Civil Engineering Fam- ily for giving me this opportunity as well as to the WaterPlus Project who is funding my studies. I appreciate the people of the Earth Resources and Environmental Geosciences (EREG) of ITC for knowledge they imparted to their students. I also give my heartfelt thanks to the Geo- logical Engineering group of ITC (Dr. Hack, Zigterman, Slob and Huisman, Z. Sicai) as well as the Engineering Geology group of TUDelft (Maurenbrecher, W. Verwaal, Rupke, A. Mulder, Gareau; Dr. Ngan-Tillard) who pass on their knowledge to their students. For my supervisors Laurent Gareau, for conceptualising this research and full time support and guidance, and to Walter Zigterman for his comments and knowledge. For the technical support of Arno Mulder and Whim Verwaal , thank you so much. For my USC family here in Delft as well as other Filipinos, thank you for letting me feel at home even if we are miles away from the people we care. To Andrea (Dang) whom I get to know better and establish good friendship with, salamat kaayo. To my friends in ITC, Enschede&Delft, I am so grateful to all of you. To all the Filipino in Enschede, thank you for your friendship. To Lynne and her family, your friendship means a lot to me. Thanks so much for the company during the social gatherings, for making me feel special during the important days in my life while I am here in the Netherlands, for the con- cern you have for me and for the advices you gave me. To all my good friends back home, thank you for your moral support. To Xenia; Thony Mar- tinez and Rosalita Kong, thanks for the friendship, I appreciate all the support you have for me. To my college friends and friends in the college of Law, I am grateful to all of you. To Ate Perla and Ate Elvie who are here in Europe, thanks for the warm welcome during my visit in each of your home and for showing me around. To my parents, thank you for all your moral as well as financial support. To my mom for her love and prayers as well as to my father for his advice, care and understanding, I appreciate all of these things. To my brothers: John, Rey, Junjun and Romel, thanks for all of your care and support. To Mariza, I am glad you became a part of our family and bringing Niez and MJ to our family. As a gratitude to my parents for all the wonderful things and the support they gave me, this thesis is dedicated to both of you.

IV DETERMINATION OF LATERAL STRESS IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Abstract

The Boom Clay formation is a well-studied deposit in terms of its geotechnical and geological properties. These studies are in line with the projects such as the WesternScheldt tunnel, the nuclear disposal site in Mol, Belgium, Western Scheldt barrier and other related projects in Belgium as well as in the Netherlands. It is a tertiary deposit that is outcropping in the Northeastern part of Belgium. This clay is a deposit that is known of not being overrun by glaciers as contrary to the Pot Clay that are being pushed by the glaciers during the ice age. At the beginning of this research project, it was assumed that such formation is cross- anisotropic due to its stress history that is primarily compose of deposition and erosion. In the present research study, the lateral stress oedometer used to determine the anisotropy of the Pot clay is used in Boom Clay to test the isotropy/anisotropy of its lateral stresses. There have been few modifications on this lateral stress oedometer, so together with the testing of Boom Clay, assessment of these modifications is also considered. The soil specimen used in conducting the test using the lateral stress oedometer is Boom Clay that is extracted from the WesternScheldt area. Four samples tube are being used in the laboratory test and each of the test displays anisotropy with respect to the three points that are 120L apart from each other. The anisotropic lateral stress oedometer was designed (Hegterman, 2003) such that it will be able to keep track of the lateral stresses of these three points in response to the vertical load applied to the soil. Such lateral stress oedometer functions the same as the standard oedometer with additional feature of being able to determine the isotropy/anisotropy of the soil specimen. Assessment of the stress history of the Boom Clay will be determined from the result of the lateral stress oedometer. The tests results suggest that the Boom Clay has some degree of anisotropy with respect to its response to the applied vertical load and it seems there is anisotropic stiffness of the deposit in its horizontal plane. As compared to the Potclay, the degree of anisotropy in Boom Clay is less than that of the Potclay (Hegtermans, 2003). The values suggest that the magnitude of the anisotropy of the Boom Clay is lesser than that of the deposits overrun by glaciers. According to Schokking et. al. (1995), the Boom Clay in the Western Scheldt has fissures that are due to stress relief during tectonic uplift and subsequent erosion while Dehandschut- ter et al.(in press) concluded that these fractures of the Boom Clay at Mol and Antwerp is of regional importance and these fractures are results of the combination of compaction and consolidation as well as uplift and bending. The anisotropic stiffness in its horizontal plane of the Boom Clay in Western Scheldt can probably be due to the uplift and flexure or bending of the deposit in such area which seems to agree with the results of Dehandschutter.

V DETERMINATION OF LATERAL STRESS IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Table of Contents

1. Introduction------1 1.1. Motivation------1 1.2. Project Description ------1 1.2.1. Steps/Procedure ------2 2. Geological History of The Netherlands and Belgium during the Tertiary------5 2.1. Introduction ------5 2.1.1. Climate------6 2.1.2. Terms------6 2.2. Tertiary------7 2.2.1. Paleocene------7 2.2.2. Eocene ------7 2.2.3. Oligocene------7 2.2.4. Miocene & Pliocene------8 2.3. Stratigraphy of Oligocene Deposits ------8 2.3.1. Tongeren Formation------8 2.3.2. Rupel Formation of The Netherlands and Belgium------11 2.3.2.1 Vessem Member ------12 2.3.2.2 Rupel Clay Member------12 2.3.2.3 Steensel Member------13 2.3.3. Veldhoven Formation------14 2.4. Roer Valley Rift System(RVRS, part of the Lower Rhine Embayment) ------14 2.5. Geological Setting of Boom Clay------14 2.6. Western Scheldt ------14 3. Environment of Deposition------16 3.1. Introduction ------16 3.2. Sedimentary Environments ------16 3.2.1. Continental (above tidal reach) ------16 3.2.2. Mixed Continental and Marine ------17 3.2.3. Marine (below tidal limits) ------17 3.3. Mode of Transportation and Deposition of Sediments ------17 3.3.1. Marine Sediments ------18 3.4. Postdepositional Changes in Sediments ------18 3.4.1. Consolidation and Densification ------18 3.4.2. Jointing and Fissuring of clay soils ------18 3.4.3. Dessication------18 3.4.4. Weathering------19 3.4.5. Diagenesis, Cementation, Authigenesis and Recrystallization ------19 3.4.6. Leaching, Ion Exchange and Differential Solution ------19 3.5. Milankovitch cyclicity ------19 3.6. Environment of Deposition of Boom Clay------21 4. Geotechnical Properties of Boom Clay ------23

VI DETERMINATION OF LATERAL STRESS IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

4.1. Introduction ------23 4.2. Geotechnical Properties ------24 4.3. Subdivision of Boom Clay ------24 4.4. Summarized Properties of Boom Clay------26 4.5. Fracture Characteristics of Boom Clay ------29 5. Theory of Consolidation and Oedometer Test------31 5.1. Introduction ------31 5.2. Theory of Consolidation------31 5.2.1. Soil Model ------32 5.2.2. Soils Weight Relationship ------33 5.2.3. Pre-consolidation Pressure------33 5.2.4. Casagrande Method and Butterfield Method------34 5.2.5. One-Dimensional Laboratory Test ------36 5.3. Standard Oedometer Test------36 5.4. Consolidation System Used in the Laboratory Experiment ------37 5.4.1. Data interpretation------39 5.5. Review of Related Literature(Analysis of oedometer Test)------39 6. Bender Element Test------41 6.1. Introduction ------41 6.2. Literature Review ------42 6.3. GDS/GeoDelft Bender Element System------42 6.4. Anisotropy and Stiffness Moduli ------43 7. Preparation of Laboratory Tests and Index Tests------45 7.1. Terms used ------45 7.2. Calibration of the Automatic Consolidation System (ACONS) ------45 7.2.1. Calculation of the Calibration Factors------45 7.3. Sample Preparation ------48 7.4. Sample Disturbance ------51 7.5. Soil Sample and Index Testing------51 8. Laboratory Test Results and Analysis ------54 8.1. Difference between the Old and New Oedometer ring------54 8.2. Lateral Stress Oedometer used in the Calculation of the minimum and maximum stress of the soil------55 8.3. Test Results of the Lateral Stress Oedometer ------56 8.3.1. Consolidation Test on Boom Clay and Analysis of its Anisotropy------56 Boom3369 ------56 Boom4591A ------57 Boom1641A ------57 Boom348B------57 8.3.2. Discussion of the Test Results ------58 8.3.3. Lateral Stress Plot vs. Settlement Curve ------59 8.4. Preconsolidation Pressure ------60 9. Conclusion and Recommendations ------61 9.1. Conclusion------61

VII DETERMINATION OF LATERAL STRESS IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

9.2. Recommendations:------62 REFERENCES------63 APPENDICES------66

Appendix A: CONSOLIDATION SYTEM USED FOR THE CONSOLIDATION TEST ...... 66 Appendix B: A-LINE PLOT ...... 70 Appendix C: CALCULATION FOR CALIBRATION ...... 70 Appendix D: CALCULATION OF RATIO MOHR CIRCLES ...... 71 Appendix E: MOHR’S CIRLE: ...... 77 Appendix F: LOG_TIME – SETTLEMENT CURVE...... 89 Appendix G: LATERAL STRESSES AT P0, P1 AND P2 ...... 98 Appendix H: PARTICLE DENSITY ...... 103 Appendix I: HYDROMETER TEST ...... 105

VIII DETERMINATION OF LATERAL STRESS IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Table of Figures

Figure 1: Work Flow of the Research Project ...... 3 Figure 2: WesternScheldt is on the southwestern part of the Netherlands...... 4 Figure 3:Geological Time scale of Tertiary ...... 5 Figure 4: Generalized correlation chart for the Tertiary of the southern and central Netherlands and neighbouring countries...... 10 Figure 5: Outcropping Boom Clay in Belgium (Figure from Laenen, B. and De Craen, M., 2003) ...... 12 Figure 6: Oligocene and early Miocene litho-chronostratigraphic chart for southern Netherlands...... 13 Figure 7: Tectonic Features in the southern part of the Netherlands (from Houtgast et al., 2003)...... 15 Figure 8: Structural sketch of NorthWestern Europe in the outcrop area of the Boom Clay...... 15 Figure 9: Orbital eccentricity: eccentricity = 0 (left) and eccentricity = 0.5 (right)...... 20 Figure 10: Precession (left) and Axial Obliquity (right)...... 20 Figure 11: Milankovitch Mathematical model ...... 21 Figure 12: Clayey, silty and septaria layers of Boom Clay (Vandenberghe, 1978) ...... 25 Figure 13: Stereographic projection of the joint frequency distribution of joint strike...... 30 Figure 14: Soil in natural state (left) and soil model (right) (Figure from Das, 1979)...... 32 Figure 15: Sedimentation compression curve ...... 34 Figure 16: Casagrande method of determining Preconsolidation Pressure...... 35 Figure 17: Butterfield method of determining Preconsolidation Pressure...... 35 Figure 18: One-dimensional consolidation testing...... 36 Figure 19: The anisotropic lateral stress oedometer ring ...... 38 Figure 20: The whole Testing system (Hegtermans, 2003) ...... 38 Figure 21: Mohr’s circle for stress with the formulas for calculating angle and minimum and maximum horizontal stress. After Dalton and Hawkins (1982). – (Figure from Hegtermans, 2003) ...... 39 Figure 22: Example of a Bender Element ...... 41 Figure 23: Stress model of a material ...... 43 Figure 24: Possible direction of shear waves in ...... 43 Figure 25: Vertical load applied (ACONS) vs. Pump Pressure (P0) ...... 46 Figure 26: Vertical Load applied (ACONS) vs. Pump Pressure (P1) ...... 46 Figure 27: Vertical Load applied (ACONS) vs. Pump Pressure (P2) ...... 47 Figure 28: Sample extruder for the Hooke Test...... 50 Figure 29. Grainsize distribution of BM348B, BM4591,BM1641A, BM3369, BM3369 and BM1641A ...... 53 Figure 30. Pump Pressure from the old oedometer ring ...... 54 Figure 31. Pump Pressure from the new oedometer ring ...... 55 Figure 32: strain gauge thickness difference of the old and new ring ...... 55 Figure 33: Total Stress, Effective stress and Pore pressure during load application ...... 55 Figure 34: Time needed for water to dissipate after a vertical load is applied. (From the settlement curve and lateral stress graph) ...... 59 Figure 35: Time needed for water to dissipate after a vertical load is applied...... 60

IX DETERMINATION OF LATERAL STRESS IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Tables

Table 1: Summarized Geotechnical Properties of Boom Clay ( Table from Rijkers et. al. 2002; F. Schokking, 1995; Schittekat et al. 1983) ...... 28 Table 2: Correction for the new lateral oedometer ring...... 47 Table 3: Correction for the old lateral oedometer ring (table from Hegtermans, 2003) ...... 48 Table 4: Depth of the Soil Sample...... 51 Table 5: Moisture content of soil sample ...... 51 Table 6: Liquid Limit, Plastic Limit and Plasticity Index...... 52 Table 7: Bulk and Dry Density of Soil Samples ...... 52 Table 8: Particle Density and Specific Gravity of the soil samples...... 52 Table 9: Ratio Maximum and Minimus Stress and Imaginary Azimuth of BM3369...... 57 Table 10: Ratio Maximum and Minimus Stress and Imaginary Azimuth of BM4591A ...... 57 Table 11: Ratio Maximum and Minimus Stress and Imaginary Azimuth of BM 1641A ...... 57 Table 12: Ratio Maximum and Minimus Stress and Imaginary Azimuth of BM 348B ...... 58 Table 13: Boom Clay Oedometer Test Results...... 58 Table 14: Preconsolidation Pressure of Boom Clay samples ...... 60

X DETERMINATION OF LATERAL STRESS IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

1. Introduction

1.1. Motivation In Geotechnical Engineering, general knowledge of the stress and strain in a soil plays a vital role; therefore it is important to know the soil’s stress history. The stress history of the soil will help to explain its present and past state of stress. Mode of formation of the deposit as well as its subsequent history will help to give an explanation of the soil’s homogeneity or anisotropy. Engineering geotechnical properties of soil are not really fully understood. In order to understand some of the geotechnical properties of soil, laboratory and in-situ tests have been conducted on Pot Clay, a deposit that is overrun by glaciers. Hegtermans (2003) determined the degree of anisotropy of the Pot Clay that is found in the Northern part of the Netherlands with the use of the newly developed lateral stress oedometer. A similar on-going project is being carried out on the glacial tills in Canada. The main objective of these research projects is to determine what type and magnitude of anisotropy results from the glacial action. In order to prove that this anisotropy is developed as a result of glaciation, it was recommended by Hegtermans (2003) to test an overconsolidated clay deposit whose sress history consists primarily of geologic deposition and erosion. This present research project on Boom Clay is a realization of such recommendation. In line with this research project on unglaciated deposits, it is proposed that the Boom Clay is used as a laboratory specimen. This Rupelian Boom Clay is a deposit that has not been overrun by glaciers. At the start of this research on Boom Clay, it was assumed that the soil would be cross-anisotropic therefore it was proposed to perform Bender Elements Testing. Bender Elements will be able to determine the small shear strain on the planes of symmetry and will prove the soils cross-anisotropy. But the Rupelian Boom Clay turned out to be anisotropic after the first few laboratory tests using the newly developed lateral stress oedometer. In order to understand the anisotropy of the overconsolidated Boom Clay being portrayed in the laboratory tests, the geologic aspect of the deposit will be considered. The laboratory test results of such soil will be link to the geological processes that such deposit has undergone.

1.2. Project Description It is known that natural clay has an anisotropic behaviour in terms of its strength and stiffness. This behaviour of naturally occurring geological materials such as clay and sand are greatly affected by many factors such as stresses, strains, stress history, mineralogy, its environment, ageing and etc. One way to look at the anisotropic behaviour of the clay is through its stress history. With regards to Boom Clay its stress history is not so well understood, this is because the measured preconsolidation pressures are higher than geological unloading and ageing. Major fac-

1 DETERMINATION OF LATERAL STRESS IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

tors that contibute to ageing effect are chemical bonding and secondary compression (Han- zawa, 1995; Bjerrum, 1967); secondary compression is very small for overconsolidated inor- ganic clays (Das, 1979). In order to understand the stress history of this marine Boom Clay, laboratory tests will be conducted. From the laboratory tests results and published data, the stress history of the Boom Clay will be reassessed. The primary objective of this research project is to assess lateral stresses in the overconsolidated Boom Clay as well as to compare it with the research of Hegtermans (2003), who conducted a research about deposits overrun by glaciers (Potclay). In order to attain the primary objective of this research the following things are need to be done: S Review published data on stress history of the Boom Clay S Test samples of Boom Clay in the lateral stress oedometer in order to determine the distribution of lateral stresses in response to vertical loading. S Reassess the stress history of Boom Clay in line with the test results obtained. S Explain why the supposed laboratory test using Bender Element test is not used on the Boom Clay

1.2.1. Steps/Procedure These are the procedures undertaken in order to obtain the main objective of this research: (Fig 1.) Step 1: Review of literature on stress history of the Boom Clay. There have been a lot of existing publications on Boom Clay. This literature will be used in order to gather information about the stress history of the Boom Clay. Some properties, most especially the geotechnical properties as well as the geological properties of the Boom Clay will be taken into account in the literature review Step 2: Soil Sample Selection. The Boom Clay to be used as a specimen in the laboratory test to be conducted is the Boom Clay from the Western Scheldt. Borehole samples of Boom Clay from the Western Scheldt are already available in GeoDelft. The clayey Boom Clay borehole samples were selected for the laboratory tests. The criteria used in the selection are the shape, length and by physical determination of the soil samples. The soil sample’s is approximately circular (not oblongated), with enough length for tests repetitions and clayey (visual observation and touching the soil). Step 3: Index Testing. Hydrometer Test, liquid limit, plastic limit and density test will be conducted on the specimen used in the lateral stress oedometer.. From this index testing, some properties of the clay used in the laboratory test will be quantified in order to character- ize the Boom Clay. Step 4: Oedometer Test. A modified oedometer apparatus will be used in determining lateral stress of the Boom Clay. During the test, the lateral stress of three points of the soil sample will be measure using the strain gauge attached in the oedometer ring. The isotropy/anisotropy of the stiffness of the Boom Clay will be determined using this oedometer laboratory test. Step 5: Bender Element Test. The small shear strain modulus of the Boom Clay was supposed to be determined using a bender element. Based from existing publications and results

2 DETERMINATION OF LATERAL STRESS IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

of lateral stress oedometer testing, it will be discussed why a Bender Element Test gives odd result if used to test the stiffness of Boom Clay. Step 6 Results and Analysis. The Index testing and oedometer test results will be analyzed. From the analysis of the laboratory tests, the stress history of the Boom Clay will be reassessed. The modifications of the lateral stress oedometer ring proposed by Hegtermans (2003) being used in the tests and discussions on such difference with the old one which was replaced will also be taken into account.

WORK FLOW/METHODOLOGY: (Fig 1.)

REALIZATION OF THE RECOMMENDATION OF HEGTERMANS(2003) –TEST UNGLACIATED DEPOSIT

BOOM CLAY TO BE TESTED IN NEW OEDOMETER TESTING APPARATUS (MEASURE LATERAL STRESSES OF SOIL SAMPLE IN THREE POINTS USING STRAIN GAUGES THAT ARE AT 120L APART) -WITH FEW IMPROVEMENT FROM THE OLD RING

LITERATURE REVIEW FOR LITERATURE REVIEW OE- BOOM CLAY ‘S DOMETER TEST AND STRESS HISTORY BENDER ELEMENTS

SOIL SAMPLE SELECTION AND PREPARATION

NEW-OEDOMETER TEST INDEX TESTING (GRAIN SIZE (ANISOTROPY OF BOOM CLAY) DISTRIBUTION, DENSITY, LL, PL)

RESULT ANALYSIS AND CONCLUSION

Figure 1: Work Flow of the Research Project

3 DETERMINATION OF LATERAL STRESS IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Location of the Borehole: There are four soil sample tube that is used in the laboratory experiment and this sample tube is from a borehole from the WesternScheldt. WesternScheldt is located in the southwestern part of the Netherlands. Though originally two boreholes were considered but it turned out that the test done on the other borehole is not a good test due to the erroneous old lateral stress oedometer.

Figure 2: WesternScheldt is on the southwestern part of the Netherlands. (WesternScheldt in star; map from http://www.europeetravel.com/maps/holland)

4 DETERMINATION OF LATERAL STRESS IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

2. Geological History of The Netherlands and Belgium during the Tertiary

2.1. Introduction There are four Eras in the Geologic Time Scale namely Precambrian, Paleozoic, Mesozoic and Cenozoic. Each of the Era is divided into different Periods where the latter is divided into Tertiary and Quaternary. The different Periods are then subdivided into Epochs. The discussion in this chapter will be mainly on the Tertiary Period (two subperiods: Paleogene and Neogene) in the Netherlands as well as a short background of the Boom Clay outcropping in Belgium and will be focusing on the Oligocene Epoch. This chapter will also discuss the stratigraphy of the Oligocene Sedimentary Rocks.

Sub Pe riod Epoch Age Period 02 mya Reuverian Pliocene Brunssumian 05 mya

ne Messinian

Tortonian

oge Serravalian Miocene e Langhian N Burdigalian Aquitanian 24 mya Chattian Oligocene Rupelian

ne 37 mya

Tertiary Priabonian Bartonian oge Eocene Lutetian

le 58 mya Ypresian Pa Thanetian Paleocene Danian 66 mya Figure 3:Geological Time scale of Tertiary

A large portion of the Cenozoic Era belongs to the Tertiary Period or in some literature it is called the Paleogene and Neogene. The Tertiary period is from 2 million years ago to 66 million years ago. The Tertiary Period is divided into five epochs namely the Paleocene (66 mya to 58 mya), Eocene (58 mya to 37 mya), Oligocene (37 mya to 24 mya), Miocene (24 mya to 5 mya), Pliocene (5 mya to 2 mya). The Epochs are subdivided into different ages.

5 DETERMINATION OF LATERAL STRESS IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

2.1.1. Climate

(This portion is referenced from: http://www.paleos.com/Cenozoic/Eocene/Eocene.htm; http://www.paleos.com/Cenozoic/Oligocene/Oligocene.htm; http://www.paleos.com/Cenozoic/Moicene/Moicene.htm )

During the Eocene, climates were generally warm or mild worldwide. There flourished tropical palms in the north as far as the London Basin. There had been unusual mixture of subtropical and tropical elements in the northern latitudes and this suggests that the region’s mean annual temperature was not as high as in the present tropics. During this time in the northern latitudes, there occurs greater rainfall with no pronounced seasonality and there was no winter frost. Generalized cooling started during the Oligocene. For the first time during the Cenozoic, the glaciers formed in Antarctica and the increase in ice sheets led to falling sea level. The tropics diminished, giving way to cooler woodlands and grasslands and even though there was slight warming period in the late Oligocene, the overall cooling trend continued and culmi- nated later during Ice Ages of the Pleistocene. Globallly, the climate is warmer during the Miocene epoch compared to its preceding Oligocene, or the succeeding Pliocene epochs. During this time modern patterns of atmospheric and ocean circulation formed. The Pliocene saw the continuation of the climatic cooling that had began in the Miocene, with subtropical regions retreating equatorially, the beginning of the large ice caps, especially in Antarctica, and the northern hemisphere lands and ocean cooling.

2.1.2. Terms The following terms are being used in this chapter: Stratigraphy – subdivision of deposit taking into consideration the time of deposition, it also means the study of the history, composition, relative ages and distribution of strata, and the interpretation of strata to elucidate Earth history. The comparison, or correlation, of separated strata can include study of their lithology, fossil content, and relative or absolute age, or lithostratigraphy, biostratigraphy, and chronostratigraphy. Transgression – this is the migration of shoreline out of a basin and on to land during retrogradation(accumulation of sequences by deposition where beds are deposited succes- sively landward because sediment supply is limited and cannot fill the available space). A transgression can result in sediments characteristic of shallow water being overlain by deeper water sediments. Regression - The migration of shoreline into a basin during progradation due to a fall in relative sea level. Deposition during a regression can juxtapose shallow-water sediments on top of deep-water sediments. Fault – it is a fracture in the earth's crust in which the rock on one side of the fracture has measurable movement in relation to the rock on the other side. Rift Valley – these are elongated depression, trough, or graben in the earth's crust, bounded on both sides by normal faults and occurring on the continents or under the oceans Lithology – means the study of rock; a rock formation/deposit having a particular set of characteristics.

6 DETERMINATION OF LATERAL STRESS IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

2.2. Tertiary

(Tertiary referenced from: Burck et. al., 1956; Van Staalduinen et. al., 1979; Stratigraphic nomenclature: Section I – Tertiary – Mededelingen Rijks Geologische Dienst Nr50 1997)

A large portion of the Tertiary deposits in The Netherlands is of marine origin and has a thickness of few to more than 1000 meters. The older Tertiary is composed mainly of marine clays and clayey glauconitic sands. The Netherlands is part of the subsiding basins that extend towards the north of Germany, England and Belgium. During the Tertiary, the subsiding basin shifted and the areas with major uplift or minor subsidence later turned out to be zones with smallest uplift or major subsidence. In the southern and central parts of the Netherlands, the Tertiary strata are not folded but in the southeastern part of the country some dislocations as a result of faulting tectonics have occurred. During the older Tertiary several salt tectonics took place that could have re- sulted from the folding in the northeast portion of The Netherlands. Few exposures of Terti- ary beds are located in the eastern, southeastern and southwestern part of the Netherlands. In the west-east trending zone and southern part of the Netherlands, the Eocene beds are absent and this is ascribed to the subsequent erosion and uplift during the early Oligocene.

2.2.1. Paleocene This Epoch is being characterized by transgression and subsequent deposition of Paleocene sediments. During the early Paleocene (Danian-Montian), the sea entered from the west into the southern part of The Netherlands and transgressed originally eastward (Keizer & Letsch, 1963). The transgression extended northward and southward during the Heersian and it is presumed that the whole country was covered by Paleocene sediments during the Landenian. In some areas of The Netherlands, the Paleocene deposits were removed due to subsequent erosion.

2.2.2. Eocene During the Eocene deposition, it is assumed that subsidence also took place during this time. At the onset of the Eocene, the volcanic activity in the Skagerrak area explains the occurrence of tuffites. In the southern portion of the Netherlands and in the West-East trending zone the Eocene is not present due to the uplift and subsequent erosion that happened in the Early Oligocene.

2.2.3. Oligocene During this epoch, volcanic activities and plate tectonic movements increased. This period of time extends from about 37 million to 24 million years ago but there have been slight uncertainties on the exact dates of the start and end of this epoch. The boundary between the Oligocene-Miocene is not being identified globally but instead at regional boundaries between the warmer Oligocene and the relatively cooler Miocene. The start of the Oligocene is marked by a major extinction event that may be related to the impact of a large extraterrestrial object in Siberia and/or near Chesapeake Bay. During the Oligocene, the climates remained warm but eventually at the end of this epoch, there was slow global cooling that led to the Pleistocene glaciations. There had been continuation of the forming of mountains in Western North America while in Europe, the Alps started to rise as

7 DETERMINATION OF LATERAL STRESS IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

well as brief marine incursion marks the Early Oligocene. (Referenced from: http://en.wikipedia.org/wiki/Oligocene) In The Netherlands during the Early Oligocene it is assumed that major uplift and subsequent erosion took place. The trend of such uplift is WNW – ESE where it is coincidental with the absence of the Pliocene and Eocene on such a zone. In this area, completely preserved Mid- dle Oligocene deposits are overlain by Upper Oligocene beds. The Middle Oligocene Sea transgressed in the presumed erosional surface in the Netherlands except its extreme southeastern part, where continuous sedimentation since Early Oligocene is present (Keizer & Letsch, 1963; Van Staalduinen et. al., 1979). In the SouthEastern portion of the country, the Lower Oligocene deposits lie on top of the Paleocene and older strata. During the deposition faster subsidence occurred in the eastern part of the country (Peel area) compared to the coastal areas (The Hague). In the Late Oligocene, subsidence and tilting towards the southeast continued as being depicted by thicker Upper Oligocene deposits in the southeast than that of the coastal area (Keizer & Letsch, 1963; Van Staalduinen et. al., 1979). The development of the Peel boundary fault is a result of the movement and sedimentation along the zone of dislocation during the late Oligocene. In the northeastern and southwestern part of the Netherlands, there is absence of the Upper Oligocene deposits and some portion of the Middle Oligocene deposits have been removed which is due to later erosion (Keizer & Letsch, 1963; Van Staalduinen et. al, 1979). The smallest uplift as presumed to occur during the Early Miocene coincides with the major uplift during the Early Oligocene.

2.2.4. Miocene & Pliocene In the Southeastern part of the Netherlands extending to the Lower Rhine Embayment, a SE- NW fault system was developed which is believed to be a result of the tectonic movements that started on the late Oligocene and continue to be active into the Quaternary. Along the fault system, there are some dislocations that are related to the Upper Rhine Rift Valley Sys- tem during the Oligocene. The Peel Horst in the Peel Area is flanked by the deep Central Graben in the southwest and the shallower Venlo Graben in the northeast Accumulation of sediments took place in the near shore marine environment in front of the former deltas in subsiding areas.

2.3. Stratigraphy of Oligocene Deposits

(Stratigraphy referenced from: Burck et. al.,1956; Van Staalduinen et. al., 1979; Stratigraphic nomenclature: Section I – Tertiary – Sep. 1997)

The Oligocene sedimentary rocks are being grouped together as the Middle North Sea Group. The Tongeren, Rupel and Veldhoven Formation are the three formations distuingished from the said group.

2.3.1. Tongeren Formation The Tongeren Formation is considered to be of Early Oligocene age and it occurs in the southern part of the province of South-Limburg. Its beds are overlying unconformably in the strata of Paleocene or older. This formation has a varying lithology and its contact with the top Rupel Formation is locally assumed to be conformable. In the Tongeren formation, there

8 DETERMINATION OF LATERAL STRESS IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

have been two named members namely the Klimmen member that is being overlain by the Goudsberg member. The boundary between the two is sharp and conformable. The Klimmen member is deposited in a Shallow-marine environment and it predominantly consists of fine- grained micaceous sand with low glauconite content. The Goudsberg member is grey, blue grey to green grey clay with thin intercalated clayey sand, lignite beds and carbonaceous clay. This clay is deposited in a lagoonal environment.

9 DETERMINATION OF LATERAL STRESS IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Figure 4: Generalized correlation chart for the Tertiary of the southern and central Netherlands and neighbouring countries. (Fig. from Nr50 1997)

10 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

2.3.2. Rupel Formation of The Netherlands and Belgium The Rupel Formation deposit is assumed to be of Middle Oligocene (Rupelian) age. This Formation is unconformably overlying the Tongeren Formation, Dongen Formation or on older strata except in the southern part of the province of Limburg, where the contact is at present considered to be locally conformable. This formation is mainly composed of dark clay that contains septaria and the clay is more sandy towards the southern and southeastern part of the Netherlands. In these areas, the lower part of the formation is predominantly composed of glauconitic sand while in the eastern part of the country, there are phosphoritic concretions at the base of this formation. The clays were deposited in middle to outer neritic setting while the sands are of shallow origin with intercalated lagoonal sediment. This formation is overlain by the sand or silty clay of the younger Veldhoven Formation. There have been subdivisions of the Rupel Formation into three members and this are the following: Steensel Member Rupel Clay Member Vessem Member In the Eastern part of The Netherlands (Twente & Achterhoek area) following is a local subdivision (Van den Bosch et al, 1975; Van den Bosch, 1984; Van den Berg & Graemers, 1993; Nr50 1997) of the Rupel Clay Member. Rupel Formation: Winterswijk Member Brinkheurne Member C Woold Clay C Kotten Clay The division of the Rupel Clay Member correspond to the two clays in the Brinkheurne Member and the Winterswijk Member. The Winterswijk Member is composed of silty clay with intercalated very fine-grained sand. The Rupel Clay Member/Boom Clay member is widely distributed and consists of dark brown grey and greenish clay with calcareous concretions (septaria). There have been local subdivisions in use for the lower part of the Rupel Formation. In the southern part of Limburg the following subdivision (Kuyl, 1975; Kuyl, 1980; NAM & RGD, 1980; RGD, 1984b; Nr50 1997) is made: (From top to bottom): Boom Clay Member (or Boom Member) Waterval Member (formerly “Unnamed Local Sand Member”) Kleine Spouwen Member (Nucula Clay Member) Berg Sand Member (or Berg Member) Waterval, Kleine Spouwen and Berg Sand Member belong to the Vessem Member. The Kleine Spouwen Clay is a brownish to bluish-grey, sandy clay and no glaconite intercalations in sands. The Tertiary deposits in Belgium are divided into Paleogene and Neogene lithostratigraphic units. The Rupel Group is part of the Paleogene where it is divided into three formations, The Bilzen Formation, Boom Formation and the Eigenbilzen Formation (Older to younger deposit). The Boom Formation is divided into BelseleWaas Member, The Terhagen Member and the Putte Member. The Boom Formation is a marine unit that is deposited in an open

11 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

shelf sea that consist of essentially grey, silty clay or clayey silt. The silty horizons have pyrite and glauconite. The formation is outcropping in the northeastern part of East-Flanders and north of the Rupel and Nete rivers. This has a thickness of few meters in East-Flanders to 150 m in North Belgium.

Figure 5: Outcropping Boom Clay in Belgium (Figure from Laenen, B. and De Craen, M., 2003)

2.3.2.1 Vessem Member The lower part of the Rupel formation is known as the Vessem member which replaces the term Berg Sand member though the concept of these two are different. The Vessem member unlike the Berg Sand member does not only denote the transgressive unit of the Rupel Forma- tion but it also includes the several coarsening-upwards units that developed locally below the main transgressive surface. The Vessem member corresponds to the Ratum member while the Rupel Clay member is correlated with the Brinkheurne and Winterwijk member. The lower part of Ratum Member, in Twente known as the Ootmarsum Sand is highly glaconifer- ous. It is a coarsening-upward sand unit that is overlain by the other part of the Ratum Mem- ber that consists of fining-upward successions of very fine-grained sands.

2.3.2.2 Rupel Clay Member In order to avoid confusion, Boom Clay Member (NAM&RGD, 1980; Nr50 1997) is being renamed to Rupel Clay Member. In the Belgian nomenclature (Marechal & Laga, 1988; Nr50 1997) the Boom Formation covers only some portion of the Rupel Clay Member that is on top of the transgressive part of the Vessem Member. The Rupel Clay Member is present in on- and offshore area of the Netherlands and it is absent in the extreme southwestern and southeastern part of the country and locally in the northeast and small parts of the western offshore. This member consists of clay that becomes silty towards its base & top and there is metre-scale alteration of silts and clays (Vandenberghe, 1978). It rarely contains glauconite and calcium carbonate (concentrated in the septaria layers) but it is rich in pyrite. The clay can be divided into three parts on areas relatively close to the basin margin. The lower part is

12 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

blue-grey in colour and is silty while the next part has a great number of intercalated bitumi- nous bands. The colour of the middle part changes from dark green-grey to dark-brown or even black. The top of the dark clay is slightly more silty and more marly and its colour is green-grey to green clays. In the southeastern part of the Netherlands, this member conformably overlies the sandy Vessem Member and is being overlain conformably by the sandy Steensel Member. During the Tertiary, this marine clay was formed due to successive transgression and regression that occurred which is believed to be the result of tectonic movements during this time. In the Southern and Eastern Netherlands it is assumed that the total thickness of the deposit is 100 m.

Figure 6: Oligocene and early Miocene litho-chronostratigraphic chart for southern Netherlands (Figure from Nr50 1997)

2.3.2.3 Steensel Member In Belgium, the equivalent of the Steensel member is the Eigenbilzen Formation (Marechal & Laga, 1988; Nr50 1997). In the Rupel Formation this member is a sandy part that has alter- nating clays and silty clays with thin sand layers that grades upwards into fine-grained sands with high glauconite content. The Steensel member conformably overlies the Rupel Clay Member.

13 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

2.3.3. Veldhoven Formation The Veldhoven Formation overlies the clayey part of the Rupel Formation. This formation consists of sand and silty clay and the bed of the Breda Formation is overlying it. The two members of the Veldhoven Formation are the Voort Sand member and the Veldhoven Clay member. In the southeastern part of the Netherlands, the Voort Sand member overlies the Boom Clay and it wedges out to the North. The Veldhoven Clay member limits the Voort Sand laterally and is also overlain by it. This bottom of the Veldhoven Formation (Veldhoven Clay) is a greenish-grey silty clay that overlain the darker grey Boom Clay in the absence of the Voort Sand. Paleontological evidences are used to distinguish the lower and upper boundaries of the formation in cases of lithologic similarities.

2.4. Roer Valley Rift System(RVRS, part of the Lower Rhine Embayment) The Venlo block, Peel block, Roer Valley Graben, Campine block and South Limburg block comprise the Roer Valley Rift System (RVRS). In the RVRS the most active fault zones are the Peel Boundary Fault zone and Feldbiss Fault Zone that bounded of Roer Valley Gra- ben(Ahorner, 1962; Paulissen et al., 1985; Houtgast & Van Balen, 2000; Houtgast,Van Balen, Kasse & Vandenberghe, 2003). The Feldbiss Fault zone is the boundary between the strongly subsiding Roer Valley Graben (north portion) and the uplifted South Limburg Block (south portion). It was noted that the last rifting episode of the RVRS started in the Late Oli- gocene and is still ongoing (Zijerveld et al., 1992; Geluk et al., 1994; Houtgast et al., 2003). The most active region in NW Europe currently is the Roer Valley Graben at the southwestern border of the Lower Rhine Embayment (Dirkzwager et. Al., 2000) and main tectonic subsidence of this zone due to border fault activity started in the late Oligocene and peaking since the Miocene (Sintubin et. Al.,2002; Michon et al.,2003)

2.5. Geological Setting of Boom Clay The Boom Clay dips gently (~2L/4%) towards the northeast and increases in thickness from a few decametres in the outcrop area to more than 150 meters in the deeper parts (Dehand- schutter et. al. in press; Schittekat et. al., 1983). In the Outcrop zone, the upper part of the Boom Clay has been eroded. During this Chattian erosion event, it reflects the Late Oligo- cene uplift of the London-Brabant and Ardenne-Rhenish massifs which is before the deposition of the Neogene glauconitic marine sands (Berchem Formation) that uncomformably onlaps the Boom Clay in the outcrop area (Dehandschutter et. al., in press).

2.6. Western Scheldt In the Western Scheldt, the Boom Clays thickness is at a maximum of 40 m and is buried at depths ranging from 40 and 60m below Datum (NAP). Schokking et. al.(1995) also suggested that geotechnical properties such as compressibility, shear strength and permeability are less affected by the geological history after consolidation. The top 50-70 m of the Boom Clay were eroded during the Pliocene and such erosional surface coincides with the base of the Oosterwijk sands. The saline porewater of the marine deposit had been replaced by freshwa- ter after the occurrence of uplift and subsequent erosion but eventually on the succeeding

14 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

transgressional phases the saline seawater intruded the clay through the fissures developed during the uplift. The Boom Clay in this area has fissures that are due to stress relief during tectonic uplift and subsequent erosion and generally the clay in the Western Scheldt has higher sand and silt content than elsewhere (Schokking et. al, 1995).

Figure 7: Tectonic Features in the southern part of the Netherlands (from Houtgast et al., 2003)

Figure 8: Structural sketch of NorthWestern Europe in the outcrop area of the Boom Clay. ( Dehanschutter, in press): LRE – Lower Rhine Embayment; RVG – Roer Valley Graben; URG – Upper Rhine Graben.

15 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

3. Environment of Deposition

3.1. Introduction It is important to determine the properties of the soil/sediments and one way to look at it is to have an idea of the environment in which it was deposited. The environment during the deposition of the sediments will make it possible to explain the physical, chemical and biological complexity of the sediments as it accumulates and consolidates over time. These are some terms used in this chapter: Clay – soil that are smaller than 2µm and is formed by small crystalline particles with one or more members of small group of minerals. Terrigenous deposits – sediments that come from land Pelagic sediments – sediments with shells and skeletal remains of tiny marine organisms and plants Calcareous Oozes – compose of easily crushed sand-to-silt size particles, nonplastic material with empty shells which covers around 35% of the sea floor Siliceous oozes – sediments with plant remains Eustasy - Global sea level and its variations where the changes in sea level are due to the movement of tectonic plates altering the volume of ocean basins, or when changes in climate affect the volume of water stored in glaciers and in polar icecaps. Eustasy affects positions of shorelines and processes of sedimentation, so interpretation of eustasy is an important aspect of sequence stratigraphy. This can be divided into transgression and regression. Erosion – it is the process by which the surface of the earth is constantly being worn away and the principal agents of erosion are gravity, running water, near-shore waves, ice (mostly glaciers), and wind. Sediments –these are mineral or organic particles that are deposited by the action of wind, water, or glacial ice and later on will form sedimentary rocks

3.2. Sedimentary Environments There are many classifications of soil/sediments, below is one of the geographic classifica- tion and soil type characterization: (Referenced from Mitchell, 1976)

3.2.1. Continental (above tidal reach) A. Terrestrial – Glacial; Aeolian (desert areas. Cobbles and pebbles on base of steep slopes; sand dunes and fines in basins); Alluvial (pluvial – high rain area; fluvial – river) B. Paludal – swampy areas (silts, muds, clays with high water content and organic matter) C. Lacustrine – in lakes (fresh water – fine-grained, quiet water deposits except for narrow shore zone of sand; saline – precipitated salt beds)

16 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

3.2.2. Mixed Continental and Marine A. Littoral – between tides (tidal lagoon – fine sand and silt in channels, organic-rich silt and clay in quiet areas, abundant organic matter and carbonates; beach – sands; tidal flats – fine- grained dark muds with lenses/stringers of sand or gravel and intermediate sizes) B. Delta – coarse and fine material, organic matter and marl; alternations between coarse and fine deposits due to shifting of stream; suspended silt and clay in the main stream that is floc- culated by salts in sea water forming marine mud on the seaward delta face which is covered by alluvial, lacustrine and beach deposits as the delta grows C. Estuarine – muds with coarser materials in channels

3.2.3. Marine (below tidal limits) A. Continental Shelf (neritic) – extends from low tide to a water depth of about 200 m; slope is very gentle (0.1 degree); sediment distribution may be irregular; sandstone, shale and limestone are abundant B. Continental slope and continental rise (bathyal) – steeper slope leads down to a gentler slope known as the continental rise; quiet bottom conditions with fine sand, silt and mud C. Deep Ocean (abyssal) – water depth averages 3600 m; muds and oozes are the main deposits

3.3. Mode of Transportation and Deposition of Sediments Another way of classifying soil is through determination of the mode at which the soil/sediments is transported. The following are the modes of deposition and transportation of sediments/soils. (Referenced from Mitchell, 1976)

1. Glacial Deposits – ice is the mode of transportation; glaciers are competent transportation agent for sediment movement. 2. Alluvial Deposits – Running water is the mode of transportation and the deposits are deposited along a stream 3. Lacustrine Deposits – this deposits are formed by deposition in quiet lakes 4. Marine Deposits – deposits are formed and being deposited in the seas 5. Aeolean soils – deposits are transported and deposited by wind; wind as an agent of erosion is restricted to deserted areas, beaches, plowed fields and inland dune areas 6. Colluvial Deposits – deposits are formed because of the movement of soil due to gravity such as landslides 7. Chemical Deposits – no transportation or are in-situ formed deposits, Evaporites deposits are example of this which are precipitates of the evaporation of salt lakes and seas; due to cyclic wetting and drying fine-grained clastics are formed 8. Biological Deposits – it is also an in-situ formed deposits and are formed by remain- ders of plants (peat) or animals (limestone)

17 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

3.3.1. Marine Sediments Marine Sediments are deposited in shallow water when the intensity of the wave action turbulence diminishes because of periods of calm waters or the sediments are carried towards the sea by returning currents. Sands and gravels are deposited on beach shorelines while finer materials in tidal flats and lagoons. Clays, silt and sand deposited on the continental shelves are generally derived from the continents and the distribution of the sediments are affected by the local geology. Calcareous & Siliceous oozes and brown clays with thickness of 300 to 600m mainly covers the deep sea floor

3.4. Postdepositional Changes in Sediments Information on the Postdepositional changes of the sediments will help us understand the soil properties and its profile data interpretation as well as in reconstructing its geological history. The sediments are unstable after deposition and this is due to its new environment’s temperature, pressure and chemistry. Eventually this will result to one or more postdepositional processes. These processes can either be physical, chemical, or biological in nature. Some of the Postdepostional processes discussed by Mitchell (1976) are consolidation & densification, weathering, Leaching, ion exchange and differential solution, Authigenesis, diagenesis, cementation and recrystallization, Jointing & Fissuring and dessication of clay soils. 3.4.1. Consolidation and Densification Increase in overburden, drying and changes in ground water table that increases in the effective stress of the soil results in consolidation of the fine-grained sediments. Consolidation decreases compressibility & permeability and increases the strength and swell potential of sediments (soil). 3.4.2. Jointing and Fissuring of clay soils Joints and Fissures in preconsolidated clays can occur due to unloading or shrinkage cracking during drying. After unloading, some joints will open which allow water to enter and soften the clay. The joints in flood plain clay can be results of deposition followed by cyclic expan- sion and contraction from wetting and drying. Skempton & Northey(1952) said that Fissures are found normally in consolidated clays at water contents well above the shrinkage limit and it is not due to unloading & drying while Rosenqvist (1955) said that for clay chunks that are stored at a constant water content for sometime, increase brittleness may develop. Trees induced fissuring and shrinkage of some clays (Barbers, 1958) that can be explained by the sucking of water of its root system that causes large capillary pressures in the ground. Weathering and release of potassium may also result in fissuring. 3.4.3. Dessication Dessication is the process of extracting moisture. Fine-grained sediments are subjected to drying that is oftent accompanied by shrinkage and cracking. In practice, it is observed that upper portions of the clay layers are pre-compressed due to drying, as a result of capillary action. Clays with a high liquid limit are most sensitive for dessication.

18 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

3.4.4. Weathering The sedimentary deposits are subjected to weathering and soil forming processes after its exposure of to the atmosphere. Weathering can result to gradual compositional changes. Unloading is a driving force of weathering. It is being characterized by decrease in effective confining pressure due to uplift, erosion or changes in fluid pressures that may result in the formation of cracks and joints on depths of thousands of meter below ground surface. 3.4.5. Diagenesis, Cementation, Authigenesis and Recrystallization Diagenesis is the process of chemical and physical change in deposited sediment. This process refers to conversion of minerals from one type to another, changes in particle surface tex- ture and formation of inter-particle bonds as a result of temperature, pressure and time. Ce- mentation contributes to clay sensitivity and has an effect on the properties and stability of many soil materials. It may also result in apparent preconsolidation pressure. After deposition, new minerals can be formed and this process is called Authigenesis. The effect of Authigenesis on the sediments are decrease in void ratio & permeability, grains become more angular and small crystals & fragments becomes coarser particles. 3.4.6. Leaching, Ion Exchange and Differential Solution Leaching is the removal of soluble or other constituents by percolating liquid. After an uplift of marine clay above sea level it is subjected to leaching action of percolating fresh water that results in removal of dissolved salts or ion exchange. Leaching and differential solutions remove some materials from the sediments.

3.5. Milankovitch cyclicity

(Milankovitch cyclicity is referenced from: http://earthobservatory.nasa.gov/cgibin/texis/webinator/printall?/Library/Giants/Milankovitch/milankovitch_3.html)

The Milankovitch theory explains the long-term change in climate. It considers the orbital variations of the earth that take into account the eccentricity, obliquity and precession cycle of the earth. Eccentricity is being used to describe the shape of the earth’s orbit around the sun where it ranges from 0.0005 – 0.0607(Thomas, 2002). The time frame for the cycle is approximately 98,000 years (Davis, 2002). Thomas (2002) states, "The eccentricity influences seasonal differences: when the Earth is closest to the sun, it gets more solar radiation, so if it occurs during the winter, the winter is less severe. If a hemisphere has its summer while closest to the sun, summers are relatively warm." The difference in the eccentricity of the earth’s orbit is being portrayed in the figure below, where the left figure has an eccentricity of 0.00 where the earth’s orbit around the sun is a circle while in the right figure the eccentricity is equal to 0.5 where earth’s orbit is elliptical in shape.

19 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Figure 9: Orbital eccentricity: eccentricity = 0 (left) and eccentricity = 0.5 (right)

Obliquity or the change in axial tilt. When the axial tilt increases the seasonal contrast increases that results to colder winters and warmer summers in both hemispheres. A cycle is around 40,000 years where the tilt of the axis varies from 22.1L to 24.5L. The present tilt of the Earth’s axis is 23.5L from the plane of its orbit around the sun. Precession is the changes in axial precession alter the dates of perihelion and aphelion, and therefore increase the seasonal contrast in one hemisphere and decrease the seasonal contrast in the other hemisphere.

Figure 10: Precession (left) and Axial Obliquity (right)

From the three orbital variations, Milankovitch formulated a comprehensive mathematical model that will be able to calculate the latitudinal differences in insolation and the corresponding surface temperature for 600,000 years prior to the year 1800. He then attempted to correlate these changes with the growth and retreat of the Ice Ages. To do this, Milankovitch assumed that radiation changes in some latitudes and seasons are more important to ice sheet growth and decay than those in others. Then, with the suggestion of German Climatologist Vladimir Koppen, he chose summer insolation at 65 degrees North as

20 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Vladimir Koppen, he chose summer insolation at 65 degrees North as the most important latitude and season to model, reasoning that great ice sheets grew near this latitude and that cooler summers might reduce summer snowmelt, leading to a positive annual snow budget and ice sheet growth.

Figure 11: Milankovitch Mathematical model

But, for about 50 years, Milankovitch's theory was largely ignored. Then, in 1976, a study published in the journal Science examined deep-sea sediment cores and found that Milank- ovitch's theory did in fact correspond to periods of climate change (Hays et al. 1976). Spe- cifically, the authors were able to extract the record of temperature change going back 450,000 years and found that major variations in climate were closely associated with changes in the geometry (eccentricity, obliquity, and precession) of Earth's orbit. Indeed, ice ages had occurred when the Earth was going through different stages of orbital variation.

3.6. Environment of Deposition of Boom Clay The Marine Boom Clays were formed under sub-tropical conditions (Van den Bosch et al., 1975; Vandenberghe, 1978; Schokking, 1995). These clays were deposited in middle to outer neritic setting wherein its foraminiferal content suggests that anaerobic conditions intermit- tently prevailed in the sea bottom. The organic matter present in the Boom Clay is considered to be land-derived (Vandenberghe, 1978) and the rhythmic alteration of silts and clays has been interpreted as an expression of Milankovitch cyclicity(Van Echelpoel & Weedon, 1990; Vandenberghe et. al., 1997). The variations in grain size and organic matter in half meter scale of the Boom Clay as observed in the field is one of the most prominent cyclicity that represents orbital fluctuation of obliquity and dominant eccentricity (Vandenberghe et al., 1997). Vandenberghe et. al.(1997) also concluded that the paleoclimatological evidence from the Early Oligocene strongly suggests that waxing and waning of ice is the driving force of these sea level fluctuations. The rhythmical alternation of these clay-rich and silt-rich layers reflects the changes in sea level and climatic (turbulence) changes Boom Clay is of marine origin but its porewater is being dominated by sodium bicarbonate.

21 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

The BCF (Boom Clay Formation) was deposited in an open marine environment during the mid-Oligocene (Wouters and Vandenberghe, 1994). The BCF fauna is clearly marine, but the depositional environment was near-shore (Laenen, 1997). From a sample from 230 m depth in the underground laboratory in Mol, Belgium Baetsle et. al.(1985) concluded that the BCF is chiefly composed of clay minerals and quartz, it also contains organic matter, pyrite and calcite. The thickness of the layers decreases towards the shoreline especially the stiff-clay layers become thin and eventually disappears (Van Echelpoel, 1991).

The clay minerals found in Boom Clay are the following (Vandenberghe, 1978): 1. Kaolinite – the kaolinite present in the Boom Clay is not of diagenetic origin but instead it is pedogenetic 2. Illite – illite in Boom Clay is detrital in origin 3. Smectite –There are two important environments of smectite genesis that exist: pe- dological conditions and the neoformation in lacustrine and marine environments. Smectites may also be derived from the erosion of smectite-containing strata on the continent. 4. Chlorite – Chlorite is not mostly present in Boom Clay; coarser chlorite flakes are detrital in origin

22 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

4. Geotechnical Properties of Boom Clay

4.1. Introduction

The Boom Formation is a marine formation that is composed mostly of clay and it is deposited in relatively deep water. This overconsolidated marine Boom Clay (Oligocene) is found almost in the entire on- and offshore area of the Netherlands. In the South-West of the country, near the type locality in the region of Antwerp (Belgium) and in the East near the Ger- man border (Achterhoek region), the clays are situated near and at the surface or it is outcropping in the northeastern part of Belgium (Vandenberghe, 1978; Schokking, 1995). The clay is divided into many layers where some shark remains can be found in some of its layers and sometimes phosphoratic concretions are present in its base. The Rupelian Boom Clay Formation is characterized by a metre-scale alteration of silts and clays that were deposited in an open marine environment (Vandenberghe, 1978).

The rhythmical alternation of these clay-rich and silt-rich layers reflects the changes in sea level and climatic (turbulence) changes. The contacts between silty clay and stiff clay layers are fairly sharp in the field and are characterized by a rapid change in grain-size content (Vandenberghe et al., 1997). Although the Boom Clay is of marine origin, its porewater is dominated by sodium bicarbonate (Bernier et. al., 1997). At Mol, the burial depth of the Boom Clay layer is 180 m and its thickness is about 100 m. It is compose of kaolinite, illite and smectite and minor compounds of chlorite. From a hydrological point of view the Boom Clay is an aquitard with very low hydraulic conductivity and, from a geomechanical view- point, it is an overconsolidated plastic clay (Bernier et. al., 1997).

There have been a lot of laboratory and in-situ test conducted on Boom Clay. These tests were carried out in line with the construction of the bored tunnel below Western Scheldt (The Netherlands), the suitability of the formation to be utilized as a shallow-land burial for the disposal of low-level radioactive waste (Mol, Belgium) and studies of such clay in the Ant- werp region. Information about the properties of the Boom Clay can be extracted from the laboratory and in-situ tests. Tests such as Standard Penetration Test (SPT), Pressure Meter Test (PMT), Cone Penetration Tests (CPT), Seismic Analysis of Surface Waves (SASW), shallow high-resolution seismic reflection survey, triaxial test, oedometer test, pocket penetrometer, torvane test etc. from the boreholes of the above mentioned projects. In line with the in-situ and laboratory test results, a better understanding and characterization of the geotechnical and geological properties of Boom Clay can be obtained.

23 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

4.2. Geotechnical Properties At Mol, the cohesion is 0.4 MPa and the effective friction angle is approximately 10L (Arts, 2000; Dehanschutter et al., 2002). The effective stess ratio K (’h/’v) is 0.8 and the vertical stress is 2.4 MPa. The overconsolidation ratios of some Boom Clay samples range between 1.6 –2.4 while the yielding points lie between 1.5 MPa and 6.0 MPa , its in-situ effective stress in Groenlo is 300 kPa (Schokking, 1995). The Young’s modulus of Boom Clay in Mol is 200-400MPa while that in Western Scheldt is only 8-50 MPa (NITG, 1996 & 1998) and this can probably be explain by its sampling depth (Mol – 223 m; Western Scheldt – 50 m NAP). The outcropping part (clay pits) of the Boom Clay has average water content of 25% while its physical porosity of 35%. The Poisson’s ratio [determined from ratio of vertical P- wave velocity and S(shear) wave velocity] is 0.480-0.468 and Young’s Modulus(determined from shear modulus and Poisson’s ratio) is 680 – 735 MPa (Schittekat, 1983). It was also sited by Schittekat(1983) that from the interpretation (using Casagrande) of the consolidation test, some samples yield burial depths of at least 88 m, 69 m and 52 m. Boom Clay may be easily classified as weak rock but the unconsolidated undrained triaxial test estimate the undrained shear strength for Boom Clay at outcrop around 175 kPa, thus classifying it as stiff to very stiff clay (Schittekat et al., 1983; Van Impe, W.F., 1997 Dehandschutter, in press).

4.3. Subdivision of Boom Clay There have been many subdivision of the Boom Clay Deposit that are based on its geotechnical properties, time of deposition (stratigraphy – discussed in another chapter) and lithology. Schittekat et. al (1983) had proposed a subdivision of the Boom Clay in Oosterweel, Antwerp that is based on the geotechnical and lithology of the deposit and this subdivision is being used nowadays. The same units were identified in Mol while Schokking et al. (1995) had identified some of the lithological and geotechnical units in Western Scheldt and Groenlo area. The Boom Clay had been subdivided into five lithological and geotechnical zones namely BK0, BK1, BK2, BK3, BK4 (Schittekat et al., 1983). Each of these units are being characterized as follows:

1. BK0 – the clay is more light colour red and it is characterized by some degree of deg- radation in geomechanical properties (Schittekat et. al, 1983). The clay content of this zone increases with depth, its colour is light grey to green and it is sandy clay (Schokking, 1995) 2. BK1 – It is a banded sequence that is composed of silty and clayey horizons, has more favourable geomechanical properties than its underlying unit 3. BK2 - A more clayey deposit with less favourable geomechanical properties than its top unit 4. BK3 – This zone includes the lower part of the (grey and black clay) Putte Clay and Waasland Clay and it is a banded sequence with silty and clayey horizons 5. BK4 – This unit is composed of silty and clayey fine sands and is a transition unit of the underlying deposit

24 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Vandenberghe (1978) has also given a subdivision of the Boom Clay based on its sedimentology, where it is divided into clayey layers, silty layers and septaria layers. The most striking feature of the Boom Clay is its layered nature where the layers have different hues of grey and and its different characteristics while drying. Besides the differences in the grainsize among the beds, black beds with a peaty outlook are present in the Boom Clay where it normally occurs in a silty bed. In Boom Clay, several horizons are originally marly sedimentation horizons and most of these are preserved as septaria beds. Septaria is defined as loaf shaped carbonate concretions that show internally nearly vertical open cracks, closing towards the rim and sometimes water bearing. The septaria layers are being numbered as S1, S2…S80. The most silty beds (base of the clay with bed nr 39 and 41) have worm tracks and they are also found in S5 and S6. The characteristics of some of the most important septaria beds (Land van Waas and the Boom area) are as follows:

1. S1 – large septaria; internal cracks are coated with calcite; between the septaria the clay is calcareous and white where the white calcareous bed has the same thickness as the septaria 2. S2 – internal cracks coated with calcite; occurs in a clayey bed; between the septaria, halfway their height; very calcareous thin layer is present. 3. S3 – small septaria; only a few septaria occur in this bed; the internal cracks are coated with calcite and this bed occurs in a silty bed 4. S4 – large septaria; the internal cracks are coated by calcite as well as by pyrite and this layer occurs in a clayey bed.

Figure 12: Clayey, silty and septaria layers of Boom Clay (Vandenberghe, 1978)

5. S5 – it is a typical flattened septaria and the internal cracks are coated by pyrite and the Septari occur in a silty bed 6. S6 – it has a spherical shape compared to the other septaria beds and the internal cracks are coated by pyrite and calcite; envelope of interlaced worm tracks surrounding the septaria and the network of cemented worm tracks has a rusty colour.

25 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

4.4. Summarized Properties of Boom Clay A summarized table of the geomechanical properties of Boom Clay from the Western Scheldt, Groenlo, Antwerp, Mol and Oosterweel is available in the table in the next page. The subdivision (BK0-BK4) of Boom Clay as proposed by Schittekat (1983) was being utilized in characterizing the soil.

DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

BK0 BK1 BK2 BK3 WS G M A O WS G M A O WS G M A O WS G M A O

190- 20- 33- 210- 40- 223- 53- Depth (m) - - - - - 22-33 ------210 40 48 223 53 260 110

Particles < 2µm - 44 44 - - 81 - 53 50 50 62 64 62 57 57 45 - 50 54 - (%)

Moisture - 22 22 - - - - 23 27 27 29 24 29 28 27 22 29 - content (%)

Liquid limit (%) - 50 71 - - 91 - 80 66 66 76 67 81 73 73 72 53 77 60 60

Plastic limit - - - - - 30 28 26 26 25 28 29 26 25 30

Plasticity index - 36 47 - - 61 - 52 40 40 56 48 53 44 53 40 51 35 30 (%)

Wet unit weight - 20 20 19 - 19.4 - 19.8 19 19.4 19.3 19 19.8 19 19.4 20 19 20.1 19 19.3 (KN/m3)

Dry unit weight ------16.1 - 15.3 - - 15.7 - 14.6 - - 16.5 - 14.7 c’ (KN/m2) - - - - - 58 - 250 - - 58 - 250 - - - - 100 - - Ø (°) - - - - - 21.5 - 19 - 25 21.5 - 17 - 17 - - 21 - 20

WS – Western Scheldt; G – Groenlo; M – Mol; A – Antwerp; O – Oosterweel

Table 1: Summarized Geotechnical Properties of Boom Clay (Table from Rijkers et. al. 2002; F. Schokking, 1995; Schittekat et al. 1983)

28 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

4.5. Fracture Characteristics of Boom Clay Dehandschutter et. al. (in press; 2002) assessed the fracturing mechanism in the Boom Clay at Mol and at Antwerp, and concluded that its intraformational fractures are result from a combination of consolidation-related volume reduction & the build-up of a specific stress path resulting from burial and subsequent uplift. After substantial uplift, horizontal stress often even exceeds vertical stress, resulting in K0-values (horizontal effective stress/vertical effective stress) above unity (Dehandschutter et. al., in press). The fracture orientation has a distinct anisotropy that indicates the influence of the regional tectonic stress and since it has moderate subsidence and uplift histories, dilatancy is restricted on shallower structural level while in deeper structural levels it undergoes ductile, compactive deformation (Dehandschut- ter et. al., in press). The systematic fractures that occur in the outcrops of the Boom Clay were also characterized. There are three different types of systematic fractures in clay pits namely the Kruibeke fault zone (meso planes), second fracture type (micro planes) and the third fracture type (regionally recognized). According to Dehandschutter et. al.(in press) that the fractures in Boom Clay are results of the combination of compaction and consolidation as well as the uplift and bending.

1. Kruibeke fault zone (shear planes – meso-planes) – it is a meter-scale fault zone; series of sub-parallel normal faults composed of a fault zone of several meters wide; macro-scale fault zone is about 5 meters in height and comprises at least 5 individual sub-parallel normal faults spaced at about 5 meters each; maximal offset along an individual fault is about 1 meter; normal fault – composed of several sub-parallel centimetre-scale slickensides composing a secondary fault zone – varying in width from 0 (only one slip surface) to several decimetres wide; slickensides called meso-planes; average strike of the fault is N120LE and it dips on average 50L to the NE. 2. second fracture type (centimetre scale shear planes – mirco-planes) - planes are smaller – order of magnitude 3-6cm; occur randomly distributed over the outcropping parts of the Boom Clay – more abundantly in the clay rich layers and not observed in most silty layers; displacement along the micro-planes is predominantly dip-slip (normal) – normal pitch variations of about 15L ; its surface is smooth (shiny and pol- ished) and striated, linear slickenlines oriented parallel, sometimes conically; slickensides – generally spaced several decimetres apart although some layers are more intensely fractured, with slickensides spaced at 10cm or less; although striae on the planes indicate a certain amount of displacement, fault throw could not be determined macroscopically and is supposed to be of micrometer order of magnitude; slickensides occur both in freshly excavated fronts and in weathered zones of old ex- cavations fronts therefore no relation with excavated wall orientation; orientation seems random at first sight – anisotropy in the attitude of micro-planes (statistical analysis) ; whole outcrop region – dominant strike of the small-scale slickensides is clearly N120LE (or between N110LE-N130LE); secondary dominant strike lies around N040LE; dip of slickensides –dominantly around 50L to 60L – although very flat and very steep planes occur occasionally

29 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

3. third fracture type – is considered regionally recognized sub-vertical planar joints; mode I vertical fractures – abundant in the whole section of all outcropping clay-pit faces; occurs as regular set and get particularly pronounce after weathering; very per- sistent in trend (Strike) and always sub-vertical; previous study (Mertens et al., 2002) -showed that they are independent from excavation from orientation therefore have to be considered natural and of regional importance; joint spacing – ranges from 1 meter in some clay-rich layers to several meters in the silt-rich layers; mean orientation of the joints shows a prevailing trend striking N130LE (J1); secondary trend striking N30LE (J2)(Figure 13); two dominating main joint trends are recognized all over the outcrop area ( more than 100 km in east-west direction – also observed in Ypresian clay (outcropping 100 km to the West) –therefore it can be considered of regional importance; two main joint sets – mutually (sub) perpendicular – a situation that seems to be common in many jointed rock formations (Caputo, 1995)

Figure 13: Stereographic projection of the joint frequency distribution of joint strike (from Dehanschutter et. al., in press) (third fracture type)

30 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

5. Theory of Consolidation and Oedometer Test

5.1. Introduction Prediction of the rate of settlement after the application of loads is very common in Geotech- nical Engineering applications. Soil layers undergo a certain amount of compression after loading and this is due to, relocation of soil particles and the dissipation of water and air from the void spaces and soil particle’s deformation. The total settlement is generally calculated using the immediate settlement, settlement due to primary consolidation and the settlement due to creep/secondary settlement. Settlement does not occur instantaneously but due to distortion of the soil where the volume is constant, immediate settlement occurs. Since immediate settlement occurs so quick, the flow of water out of the soil mass is negligible making the volume constant unless the soil is saturated or extremely permeable. The calculation of this settlement is derived from the theory of elasticity Primary settlement/Consolidation settlement of the soil mass occurs due to the flowing out of the pore water that results in a time-dependent decrease in its volume. The water dissipation from the soil mass is dependent on the pore pressure, permeability and compressibility of the soil. In saturated compressible clays, primary settlement continues long after the completion of immediate settlement due to clay’s low permeability. In clays, primary/consolidation settlement may be several times higher than immediate settlement. Creep settlement or secondary settlement in soil occurs during a long time and it is also called post-primary consolidation period. The reason for secondary settlement is not certain, but creep or deformation under constant stress is a phenomenon also observed for other materials. Final settlement can then be calculated as the sum of the three settlements that can be calculated as:

St = Si + Sc + Ss

Where: St = immediate settlement

Sc = primary consolidation settlement

Ss = creep settlement/secondary settlement In some cases (stiff clays), creep settlement is considered to be negligible. The total settlement will be the equal to the sum of the immediate settlement and primary consolidation settlement, which is the settlement after the dissipation of the excess pore pressures. (Reference: Lee et. al, 1983)

5.2. Theory of Consolidation

(Theory of Consolidation reference: Lee et. al., 1983, Das, 1979; Skempton, 1970)

Consolidation is the gradual decrease of the water content at constant load. The compression of clay due to increase in load is very slow due to the low permeability resulting in a gradual

31 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

adjustment of the position of the grains to the increase in pressure. It requires a long time to drain out the excess pore water. Skempton (1970) defined consolidation as “the result of all processes causing the progressive transformation of an argillaceous sediment from a soft mud (as originally deposited) to a clay and finally to a mudstone or shale”.

5.2.1. Soil Model A natural soil has three-phase systems that consist of soil solids, water and air.

Vv W V Ww Vw V W V Ws s

Soil in natural state Soil element in three phases Figure 14: Soil in natural state (left) and soil model (right) (Figure from Das, 1979)

The total volume and total weight of the soil sample are then equal to the following equation:

V = Vs + Vv = Va + Vw + Vs (eq. 1)

W = Ws + Ww (eq. 2) Where: V = the total volume of the soil W = total weight where the weight of the air is assumed to be negligible

Vv = volume of voids

Va = volume of air in the voids

Vw = volume of water in the voids

Vs = volume of soil solids

Ww = weight of water

Ws = weight of solid n = porosity S = degree of saturation

Soil Volume Relationship Considering the three phases of a soil element, the commonly used volume relationship are the void ratio, porosity and the degree of saturation. The void ratio (e) is the ratio of the vol-

ume of voids (Vv) to the volume of solids (Vs) and is define by the equation:

e = Vv/Vs (eq. 3)

The porosity (n) of the soil is the ratio of the volume of voids (Vv) to the total volume (V)

while the degree of saturation (S) is the ratio of the volume of water (Vw) to the volume of voids (Vv).

n = Vv/V (eq. 4)

S = Vw/Vv (eq. 5) The porosity of the soil can also be derived from its void ratio (eq. 3) and volume (eq. 1). The relationship between the porosity and void ratio of the soil is as follows

32 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

e = Vv/Vs = Vv/(V-Vv) = (Vv/V)/(1-(Vv/V)) = n/(1-n) (eq. 6) n = e/(1+e) (eq. 7) The void ratio can also be determined using the following equations:

e = Gsw/d – 1 (eq. 8)

e = wGs/S (eq. 9)

where: Gs = specific gravity of soil 3 w = density of water (kg/m ) 3 d = dry density of the soil (kg/m ) and is defined as the ratio of the dry mass of the soil with its volume w = moisture content at 100% saturation

5.2.2. Soils Weight Relationship In considering the weight relationship in the soil the moisture content and the unit weight are being used. The moisture content (w) is equal to the ratio of the weight of water to the weight of solids in a given volume of soil while its unit weight () is equal to the soil’s weight per unit volume. W = Ww/Ws (eq. 10) = W/V (eq. 11)

In the field, a soil at a certain depth has been subjected to maximum effective overburden pressure in its geologic history. The existing overburden pressure at the time of sampling is either equal to or less than the maximum effective overburden pressure that occurred in the past.

5.2.3. Pre-consolidation Pressure In Geotechnical Engineering, determination of pre-consolidation pressure will lead to understanding the behavior of cohesive soil and describing the soil’s stress history. A lesser overburden pressure in the field is due to human interference or geological processes such as erosion of heavier overburden, tectonic movements, fluctuation of water table, glacial ice melt- ing, precipitation of cement agents, delayed compression. There are two basic clay definition based on its stress history: 1. Normally consolidated – the clay’s present effective overburden pressure is equal to the maximum pressure to which it was subjected to in the past. 2. Overconsolidated – the clay’s present effective overburden pressure is lesser than the maximum pressure to which it was subjected to in the past. The maximum pressure is called as the preconsolidation pressure. Generally preconsolidation pressure of the soil is being determined by a graphical procedure on its experiment results. Some of the known procedures are those that are suggested by Casagrande, Butterfield, Becker and etc.

33 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Sedimentation Compression Curves Skempton (1970) presented a representative sedimentation compression curve of an argillaceous deposit. Through this curve, the normally consolidated and overconsoldated deposit is being explained through the deposition and erosion of the sediments being deposited

Sedimentation compression curve E r

a o tio on s i t i i o n

Normally consolidated pos e t/Void ra D n b d r Conte

te c

Wa Over-consolidated

pc’ Vertical effective stress a b c d

Figure 15: Sedimentation compression curve

5.2.4. Casagrande Method and Butterfield Method In determining the preconsolidation pressure of the Boom clay Casagrande and Butterfields method are used. Casagrande is commonly used while the method proposed by Butterfield has advantages as compared to the other methods (refer to 5.5). The procedure that Casagrande suggested in the construction of the graph in determining the preconsolidation pressure Pc from the laboratory e-log p plot is the following: 1. Establishment of a point a where the e-log p plot has a minimum radius of curvature through visual observation 2. Drawing of a horizontal line ab 3. Drawing a line ac that is tangent to point a 4. Drawing of a line ad that bisects the angle bac 5. Projecting the straight line portion of gh of the e-log p plot back to intersect ad at f. 6. The abscissa of the point f is the preconsolidation pressure.

34 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Casagrande BM1641-Test3

0.62 a ff b 0.6

0.58 d 0.56 e g 0.54 c

0.52

0.5 h 0.48 100 1000 10000 Log p (kPa)

Figure 16: Casagrande method of determining Preconsolidation Pressure

Butterfield Butterfield (1979) uses the ln(1+e)-lnp curve where the preconsolidation pressure is determined by getting the point of intersection of the extended straight from the linear portions on both ends of the ln(1+e)- lnp compression curve.

Butterfield

0.51

0.49

0.47 ) e +

1 0.45 Series1 ( ln 0.43

0.41

0.39 100 1000 10000 Log p (kPa)

Point of intersection of the two lines is the preconsolidation pres-

Figure 17: Butterfield method of determining Preconsolidation Pressure

35 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

5.2.5. One-Dimensional Laboratory Test Terzaghi first suggested the one-dimensional consolidation testing with the use of an oedometer (consolidometer). The soil sample is placed inside a metal ring with porous stone on top and on the bottom. Generally the soil sample is 63.5mm(2.5 in) in diameter and 25.4 mm (1.0 in) thick.

d metal ring

Figure 18: One-dimensional consolidation testing

Terzaghi(1925) proposed the theory that considers time rate of the one-dimensional consolidation for saturated clay soils. The following assumptions are made in the mathematical deri- vation: (1) The saturated clay-water system is homogeneous (2) Flow of water is in one direction (direction of compression) (3) Darcy’s Law is valid (v = ki; v = velocity; k=coefficient of permeability; i = hydraulic gradient) When a compressive stress is applied on a laterally confined layer of saturated soil with a certain thickness there will be a reduction of its thickness in the direction of the load. The volume change in the soil will initially occur quickly and then it gradually decreases. This volume change as a result of the application of the load will result in a decrease in pore volume so there’s a need for the porewater to dissipate. Upon the application of the vertical load it will be initially transferred to the water phase or supported by the pore water and will result into excess pore pressure. With the porous stone on top and bottom of the soil, this porewater will dissipate out from the soil and will eventually result to dissipation of the excess porewater pressure. The change in thickness of the soil will depend on the gradual dissipation of the porewater pressure from the soil. The rate of porewater pressure dissipation depends on the permeability of the soil. Using the continuity equation, the amount of consolidation can be calculated (Terzaghi, 1925).

RRVh.22RhR2h k k k /dxdydz (eq. 12) RRtx xy22RyzRz20

5.3. Standard Oedometer Test In a laboratory oedometer test, one-dimensional compression and the swelling of the soil is being measured. A soil in cylindrical shape is enclosed in a metal ring that is subjected to series of increasing static loads and the changes in thickness are recorded against time. The compressibility of the soil can be determined from the changes in thickness of the soil through the calculation of the Compression index (Cc) and coefficient of volume compressi-

36 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

bility (Mv). During a load stage the rate of consolidation can be obtained and the coefficient of consolidation can be calculated from the recorded changes in thickness against time. Usu- ally the log-time method is used (BS 1377).

Procedure The vertical static load increments are applied at regular time intervals (e.g. 12, 24, 48 hr.) and the load is doubled in every increment up to the required maximum load (e.g. 25, 50, 100, 200, 400, 800 kPa). In every load stage, the thickness changes are recorded against time. After reaching a full consolidation under the final load, the loads are removed (in one or several stages - to a low nominal value close to zero) and the soil is allowed to swell. After the specimen is removed, the soil’s thickness and water content is determined. With a porous stone both above and below the soil specimen the drainage is two-way (i.e. an open layer in which the drainage path length, d = H/2).

5.4. Consolidation System Used in the Laboratory Experiment Hegtermans (2003) used a consolidation system that is composed of an Automatic Consolida- tion System (ACONS), new lateral stress oedometer and pumps to test the Pot clay. An ACONS is a computer controlled pneumatic oedometer loading frame. The lateral stress oedometer has the same result with the standard oedometer test and at the same time it will be able to measure lateral stresses in three points equally spaced around the soil specimen thus it is suitable to measure anisotropic lateral stresses. In this current research project, the same consolidation system will be used to test of the Boom Clay samples. The consolidation system used in the experiment is composed of an Automatic Consolidation System (ACONS), new lateral stress oedometer ring. The description of the ACONS and the design of the anisotropic lateral stress oedometer ring as well as its description as to how the whole system works during a test is in the appendix (from Hegtermans, 2003). The lateral stress oedometer ring has a thick-walled steel ring with three openings where strain gauges are attached and each of three openings has an offset of 120° (Hegtermans, 2003).

37 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

In the top view, the two ways of numbering are shown: the pressure controllers have numbers p0 to p2. These correspond with the membrane numbers 1 to 3(Hegtermans, 2003).

Figure 19: The anisotropic lateral stress oedometer ring

Figure 20: The whole Testing system (Hegtermans, 2003)

38 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

5.4.1. Data interpretation A detailed description for the data interpretation of the consolidation system is provided by Hegtermans (2003) and is available in the appendix. The same analyses as the standard oedometer is used in making the Log_Time-Settlement curve and the e-Log P plot. A Mohr’s circle is used in order to analyse the data of the consolidation system having the three known independent horizontal stresses of the soil specimen. The magnitude of the minimum and maximum horizontal stresses is determined through Mohr circle. With these two known horizontal stresses, its ratio can be determined as well as the location of these three points in the circle. By calculating the value of 2θ that is the angle of the point P0 from the horizontal axis, the azimuth of the three points can be known. Below is the formula for the minimum and maximum point of the Mohr circle and the orientation of the point P0.

12 appp pp22pp2 ppppp τ 33012 0 1 2 011220

12 222 120˚ b p01pp2 ppp01 2p0p1p1p2p2p0 2θ 33 a p2 p1 p0 b σ 1 pp12 3 sin 2 2 p22p p2pp pp pp 3 01 2011220

Figure 21: Mohr’s circle for stress with the formulas for calculating angle and minimum and maximum horizontal stress. After Dalton and Hawkins (1982). – (Figure from Hegtermans, 2003)

5.5. Review of Related Literature(Analysis of oedometer Test)

There are many methods in the determination of the preconsolidation pressure of the soil. Cortellazzo(2002) examined four of these methods namely: (1&2) methods of Taylor and Casagrande(commonly used); (3) the log (H2/t)-U method (H – length of drainage path of the consolidating layer or specimen; U – average degree of consolidation) and (4) log - log t method (Sridharan and Prakash, 1997)( - observed total compression at any time, t) and concluded that that the values obtained using Casagrande’s method may be not usable in some cases because of their variability compared with values obtained using other methods. Onitsuka et al. (1995) compared the two alternative approaches to determine the yield stress from oedometer test data (1)work per unit volume approach (Becker et al., 1987) and (2) bilogarithmic approach – ln(1+e) – lnp plot (Butterfield, 1979) or log(1+e)-logp plot(Oikawa, 1987). Some advantages of the bilogarithmic approach compared to the work approach are the following (1) it is not necessary to calculate the work – linear approximation assumption in the stress-strain relation is not implicated (2) easy to obtain the compression index (3)

39 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

since the bilogarithmic plot is similar to the current e-logp plot, it can be convenient to use the available data with the bilogarithmic method. Another advantage of the ln(1+e)-logp approach is that it can eliminate the well-known problems in determining the yield stress from the e-logp plot using Casagrande’s method.

40 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

6. Bender Element Test

6.1. Introduction In determining the soil’s small strain shear modulus a bender element test maybe used. This is a laboratory technique that incorporates shear wave theory in measuring the shear stiffness of the soil at small strains. Bender Elements (BE) generate and receive seismic body waves and measure the shear wave velocities that investigate the small strain shear modulus of the clay. This is being influenced by current magnitudes of the clay’s void ratio and acting effective stress, overconsolidation due to unloading & aging, plane of polarization of the propagated seismic body waves & related magnitude and orientation of the principal stresses. The Bender Elements are normally attached to triaxial apparatus, oedometer apparatus and others where the transducers comprise of two piezo-ceramic plates, these are placed on the opposite end of the sample, one is a source and other is a receiver element. When the source element is deflected using a voltage signal it produces a shear wave that travels through the sample and produces a voltage at the receiver end. An oscilloscope is used to continually monitor the signal, which allow the travel time of the shear wave to be measured; this can then be used to determine the G0 (small shear strain modulus). The shear wave velocity can

be calculated from the sample length and travel time. To determine G0 the following formula is used: 2 G0 = ρV s where ρ = total mass density of the soil; or t = travel time 2 2 G0 = ρL /t VS = Shear-wave velocity; L = distance between tips of elements (Viggiani &Atkinson, 1995)

Figure 22: Example of a Bender Element

41 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

6.2. Literature Review Jamiolkowski et. al.(1995) uses Bender Elements (BE) in order to determine influence of the current magnitudes of current void ratio and acting effective stress of the soil, overconsolidation due to unloading and to aging and the plane of polarization of the propagated seismic body waves and the related magnitude and orientation of the principal stresses in the Go of the soil. He used an oedometer where these Bender Elements are being attached and concluded that small strain shear modulus measured in the field are only slightly higher than those results from laboratory tests. Salgado et. al.(2000) attached the Bender Elements (BE) on a triaxial apparatus while Zeng et. al.(1999) attached it on an oedometer to measure the shear modulus in the horizontal, vertical, and two inclined shear planes. P. Simonini & S. Cola(2000) used an embedded Bender Element(BE) system in a triaxial apparatus where the shear wave velocity measurements were recorded at increasing KO stress levels during the consolidation stage both on sand and clayey silt samples. Viggiani and Atkinson (1995a,b) and Arulnathan et. al. (1998) discussed that in extreme cases that errors in the Go values are in the order of 15%. Errors on the determination of Go are due to the deviations from 1D wave propagation, which is assumed in the calculations; wave interference at the caps; the different time delays between the generation of the electrical signal and its transformation into a mechanical impulse at the source bender element and the reverse process at the receiving bender element; and near field effects according to Arul- nathan et. al. (1998). Salgado et al. (2000) used a Bender Element that was embedded in a triaxial apparatus and found out that the actual G0 values may differ from those measured in the testing program by as much as 15%, although the actual difference is probably smaller due to self-compensating effects Pennington et. al.(1997) developed a bender element that makes use of a bender belt. There are four sets of Bender Elements that are incorporated in a triaxial apparatus. The soil specimen the Gault clay that is an overconsolidated late Cretacious clay which has been folded and eroded since deposition.

6.3. GDS/GeoDelft Bender Element System The Bender Element system that should have been used for the supposed Bender Element Testing of the Boom Clay is the GeoDelft Bender Element System. The Bender Element system is composed of Bender Element inserts, adapted pedestal and topcap, external and a high-speed data acquisition and control card (PCI) resident in the PC. GDS have developed a cost-effective bender element system that is attached to a triaxial testing apparatus thus making the measurement of Gmax and maximum modulus simple. Ge- oDelft have three element pairs namely the combined S and P wave as well as the high power P-wave only. These element pairs are composed of source and receiver element that are being encapsulated and mounted into inserts which are either a pedestal or topcap. The replacement of bender element can be done by removing the insert and replacing it with a new one. There is a bender element software in the system that will be able to generate signals for the source element and received data for the receiver which make the data available right after the test.

42 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

In a bender element system in order to have a good result for determining the shear wave velocity, three components are to be considered namely a digital oscilloscope, function genera- tors and Bender Elements. It was suggested by Brignoli et al.(1996) that minimum sampling rate should be 20 x 106 samples per second. The resolution of the oscilloscope or detection of smallest voltage signal that is approximately 0.1 and 5 mV is also important. The oscilloscope must also be able to store and download received signals. (Referenced from: http://www.gdsinstruments.com/group_SP/bender.htm)

6.4. Anisotropy and Stiffness Moduli

σ1 σ1 σ1

2 σ2 σ3 σ3 σ3 σ3 σ2

≠ ≠ ≠ σ1 = σ2 = σ 3 σ1 σ3 σ1 σ2 σ3 a) isotropic b) cross-anisotropic c) anisotropic d.) anisotropic (rotated)

Figure 23: Stress model of a material

Length used for calculating moduli

Propagation direction

Figure 24: Possible direction of shear waves in anisotropic material (unknown azimuth)

The stress model of the soil is illustrated in Figure 23, where vertical and horizontal stresses are named as 1, 2 and 3. Small strain stiffness of soils are oftentimes modeled as elastic and that it is already widely accepted that both static and dynamic measurement techniques will be able to recover similar values of small strain moduli. The small strain stiffness of the soil may be anisotropic (Pennington et. al., 1997; Arroyo et. al., 2003) and there are many authors who studied such anisotropy.

43 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

According to Arroyo et. al.(2003), in determining the elastic moduli of a material the measured data (velocity) should be determined along the axes of elastic symmetry. Therefore, the material (soil) must have such feature and the orientation of its axis with respect to the measuring direction should also be known. Pennington et. al.,(1997) determined the azimuth of the Gault clay(specimen) and attached the Bender belt along such azimuth. The phase velocity of the bender element is directly measured but in reality it is propagating in oblique directions of anisotropic materials (Arroyo et. al., 2003). Since the azimuth of the maximum stress of the Boom Clay is not known it suggest that during a Bender Element test the axes of elastic symmetry of such specimen could not be determined thus, the propagating wave will have unknown oblique direction (Figure 24).

44 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

7. Preparation of Laboratory Tests and Index Tests

7.1. Terms used Two terms are used in this chapter, in order to put a distinction between the two anisotropic lateral stress oedometers used in the discussion here are some description of the oedometer rings: Old (Lateral Stress) Oedometer – the lateral stress oedometer used by Hegtermans (2003) in doing some laboratory test on Pot Clay. New (Lateral Stress) Oedometer – the newly-acquired lateral stress oedometer where there are few small changes in the design (chapter 8) from the old lateral stress oedometer.

7.2. Calibration of the Automatic Consolidation System (ACONS) A new lateral stress oedometer ring is used in most of the consolidation test done on Boom Clay. Since the ring is new and has few modifications from the old lateral stress oedometer then a new calibration is done in order to correct the data carried out in the consolidation system. During calibration, the pumps, ACONS and the oedometer ring is taken as one whole system. A latex cylinder was used to calibrate the apparatus. It simulates the loading process of the soil specimen/sample. The Poisson ratio of the latex cylinder used in the calibration is 0.5, so this means that the horizontal stresses of the pump should correspond to the vertical load applied to the latex cylinder. Another correction that is applied on the pressures on the strain gauges is the correction for the insert values. These insert values are the pressure of the pumps acting on the strain gauges before the application of the vertical load on the specimen (pump pressure when the soil is stabilized for overnight). During the calibration of the latex cylinder, the load steps used the range from 100 – 2000 kPa, the first step is ommitted due to the fact that the contact between the sample and the strain gauges as well as ACONS is not yet well establish.

7.2.1. Calculation of the Calibration Factors

There are three calibration tests considered in the calculation of the factors to be applied for the strain gauges of the new lateral stress oedometer ring. These three calibration tests are used for the calculation were running at different time duration. One calibration test run for 1 minute for every load step (10 mins for the entire calibration test) while the other calibration test run for 3 minutes (30 mins for the entire calibration test) and the last one last for 1 hour for one load step (calibration test run overnight). The load steps (vertical load) of each calibration test are around 100, 200, 400, 800, 1600, and 2000 kPa and 1200, 500 and 100 KPa for the unloading. The following steps are used in calculating the calibration factors:

45 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

1. The pump pressures of each calibration test are corrected from its zero values (value before insert). This is due to the fact that the pump pressures normally has small pressures at the beginning of the test, it is quite hard to have a non-zero value (values are normally set just almost zero) 2. The points of each load step for the three calibration tests are plotted in the graph 3. The equation of the regression line is being determined for each pump (there are 3 pumps in the system) 4. The value of the R2 is also determined. The calibration graphs of each of the Pump are as follows:

channel 04(corrected-insert values)

2000 Series1 1500 Linear (Series1)

1000 y = 1,0975x + 34,412 R2 = 0,9986 500

Pump Pressures

0 0 500 1000 1500 2000 ACONS

Calibration for Pump 1 (P0 - Channel 04)

Figure 25: Vertical load applied (ACONS) vs. Pump Pressure (P0)

CHANNEL O5(corrected-insert values)

2000 Series1 E R 1500 Linear (Series1)

ESSU 1000

PR P

M 500 y = 1,126x - 35,789

PU R2 = 0,999 0 0 500 1000 1500 2000 ACONS

Calibration for Pump 2 (P1 – Channel 05)

Figure 26: Vertical Load applied (ACONS) vs. Pump Pressure (P1)

46 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Channel 06(corrected from insert values)

2000

1500 channel 06 Linear (channel 06)

essure r 1000 y = 1,1359x - 43,904 2 mp P 500 R = 0,9987 u

P 0 0 500 1000 1500 2000 ACONS

Calibration for Pump 3 (Channel 06)

Figure 27: Vertical Load applied (ACONS) vs. Pump Pressure (P2)

The R2 for pump 1(P0 – channel 04), 2(P1 – channel 05), and 3(P2 - channel 06) are 0.9986, 0.999 and 0.9987 respectively which means that the line correlates well with each of the calibration points for each of the pumps during loading. The calibration of the three pumps is coinciding with each other especially when the vertical load increases. This slight difference for the first pump (P0) with the other pumps can be due to the gauge better sensitivity to smaller load as compared to the other two strain gauges. The errors will be eliminated by applying the calibration factors. The unloading also coincides with the loading lines (i.e. there is no hysteresis).

Calibration Factors: During the calibration, the pump pressure’s response is a bit higher compared to the vertical load applied. Ideally, the pump pressure should be equal to the vertical load applied. To eliminate the error in the system, calibration factors are determined. Due to pump pressure higher response compare to the vertical load being applied, the calibration factors should be divided to the value of the pump pressure that corresponds to a certain vertical load. These are the correction formulas for the pumps:

p p()corrected Pressure controller 1 1.0975

p Pressure controller 2 p(corrected ) 1.126

p Pressure controller 3 p()corrected 1.1359

Table 2: Correction for the new lateral oedometer ring.

47 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Difference in the calibration of the Old & New Lateral Stress Oedometer ring There is a slight difference on the calculation of the calibration factors for the two rings. Hegtermans (2003) determined the calibration factors of the old lateral stress oedometer by calculating the slope of line from one load to the next load. The average of this slopes were used to determine the correction factors for each of the pumps. The correction factor determined during the calibration has to compensate the defect of the one of the strain gauges [pump 3(P2)]. In the old ring, the correction factor of pump 3(P2) is 1.347 as compared to 1.1359 in the new ring. With the new lateral stress oedometer, no such defect was detected. The pump values were coinciding each other as the applied vertical load becomes higher. The values of the correction factors for the new lateral oedometer ring are closer compared to the correction factor of the old one.

p Pressure controller 1 p()corrected 1.08 2.026*10-6 * p p Pressure controller 2 p()corrected 1.004 8.84*10-5 * p p Pressure controller 3 p()corrected 1.347 8.148*10-5 * p

Table 3: Correction for the old lateral oedometer ring (table from Hegtermans, 2003)

Intercepts of the correction due to calibration: The intercepts of the equation for the correction due to calibration are 34.412, -35.78, -43.904 (see Figure…) for P0, P1 and P2 respectively. During the correction, these values are not considered since these are errors due to non-perfect contact of the latex specimen and strain gauges. This occurs because the latex specimen is slightly smaller than the test ring. Thus, at low vertical load applied, the sample deforms until it contacts the sides of the ring. At higher loads, the response is truly linear, and the slope at these higher loads is indicative of the true horizontal stress.

7.3. Sample Preparation Hegtermans (2003) made a distinction between a soil sample and a soil specimen in order to avoid some confusion on these two terms. A sample was defined as the material that was removed from the ground, for example from a borehole, and taken up to the surface while a specimen is part of a sample that is prepared for a specific test. Every new laboratory test in the lateral stress oedometer, the soil specimen needs to be prepared in order to load it to the apparatus (ACONS). Hegtermans(2003) proposed the steps in preparing a soil specimen where an in-situ ring (called preparation ring) is used to trim it. Issues such as wall friction, orientation of specimen, tilt in the preparation direction and diameter of the preparation ring compared to the lateral stress oedometer ring are being considered in the soil specimen preparation. There are only few variations in the procedures that is being used in preparing the soil specimen due to few reasons such as the sample tube for the

48 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Boom Clay is made of metal (potclay has a plastic sample tube), diameter of the Boom Clay soil sample is 75 mm while the pot clay is 100 mm. These are the steps used in preparing the soil specimen of the Boom Clay for the lateral stress oedometer: 1. The soil sample is taken out from the metal sample tube. An imaginary reference line is made in the entire soil sample and the top and bottom portion of the sample is being noted. 2. A slice of around 50 mm thick of soil specimen is cut out from the soil sample. It is made sure that an axial line is drawn in the preparation ring and that the weight of the ring is recorded. The preparation ring is then placed in the sliced soil and it was made sure that the center point of the soil sample is approximately the center point of the preparation ring. The cutting edge of the ring is made sure to be pointing the top of the sliced specimen (soil on the cutting edge of preparation ring – top portion of the soil specimen to be place on the top portion of the oedometer ring which will be in contact with the ACONS) 3. The sample extruder for the Californian Bearing ratio test (CBR) was used to push the preparation ring into the sample slice. Upon pushing the preparation ring using the extruder, it should be observed that there would be no overpushing as it would result to coMPaction of the soil specimen inside the ring. This can be observed from the trimmed portion of the slice specimen outside the preparation ring. 4. Since the soil specimen has no plastic tube, the wire saw is used to trim down the outer portion of the specimen (soil outside the preparation ring). It should be carefully cut out so as no to disturb the soil specimen inside the preparation ring. 5. A certain length (around 1 cm) on the top portion of the specimen pushed out and is trimmed out using a palette knife taking some consideration a certain length of the soil specimen that is disturbed. After trimming, the surface is levelled off. 6. The prepared top surface is placed onto the clean ‘plug’. This is a device that exactly fits the preparation ring and is exactly 30 mm high, the required height of the specimen. 7. Carefully the specimen is pushed over the plug.

49 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

8. The bottom of the specimen is prepared as described in step5. The weight of the preparation ring and the soil specimen is recorded.

Figure 28: Sample extruder for the Hooke Test 9. To install the specimen into the lateral oedometer ring, the preparation ring is placed onto the top of the oedometer ring and lined up as required. The top porous stone is placed onto the specimen while the bottom porous stone on the bottom of the oedometer ring. 10. With the used of the sample extruder for the Hooke test, the specimen is pushed into the oedometer ring. This sample extruder is used to ensure the specimen is pushed in parallel to the inside wall of the oedometer ring. It should be noted that the soil specimen will not be overpushed by the extruder, this can be observed when the top porous stone in just on level with the top portion of the oedometer ring 11. The oedometer ring with the specimen will then be put inside a circular plastic container. Distilled water is placed inside the container at such height that the water can pass through the small channels in the oedometer ring.

14 12. The recording of the lateral stresses that acts on the strain gauges in the oedometer should be started. The soil specimen inside the oedometer ring is allowed to stabilize for overnight. 13. After stabilizing it for overnight, the container with the oedometer ring (with soil specimen) is placed in the ACONS. 14. In putting the the oedometer ring in the ACONS (oedometer) it should be observed that the frame is levelled and that most probable good contact with the ACONS frame and the specimen will be established. 15. The loading and unloading will then start. The loading time will be decided such that for each loading/unloading step the primary consolidation is attained. This can be checked using the log_time-deformation plot for each loading/reloading steps. In the case of the Boom Clay 12 hours for each loading/reloading step is enough time for the soil specimen to consolidate.

50 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

16. When the loading and reloading is finished, the soil specimen is taken out from the oedometer ring with the help of the extruder from the Hooke’s Test then weighed and oven-dried.

7.4. Sample Disturbance There are two major factors that cause sample disturbance namely stress relief and strain/ destructuring. Stress relief is the result from reduction of in-situ total stresses to zero. De- structuring/tube sampling strains is the erosion of that component of resistance that is related to the bonding and fabric of the soil/the result from the displacements caused by pushing a tube into the soil (Hight 1985; Graham et al. 1987), the soil as a result of the adhesion between the outside of the sample and the inside of the tube as it passes up into the sampler. Siddique et al.(1999) conducted a test on a reconstituted normally consolidated London clay and over-consolidated London clay. It was concluded from the test results that the most pronounced effects due to imposed tube-sampling strains in reconstituted normally consolidated London clay are significant reductions of mean effective stress and undrained small-strain stiffness, which are accompanied by reductions in the excess pore pressure generated during shearing. In the laboratory test conducted on the over-consolidated reconstituted London clay, it was found out that the laboratory simulation of tube sampling strains together with deviatoric stress relief (i.e., “ideal” sampling) causes little change in its effective stress, stiffness, and strength. In some cases, the soil may be disturbed more in the field than it is during sampling (Olson, 1998). The disturbance in the field occurs when the drainage wicks are driven into the soil and when shallow soils are so soft that construction of a working platform leads to mud waves.

7.5. Soil Sample and Index Testing There are four soil sample tubes used for the oedometer test. These sample tubes are from one borehole. The moisture content, liquid limit & plastic limit (Atterberg’s Limit), particle density, bulk density, dry density and hydrometer test are the testing done in the Boom Clay Depth (m) No. of ID No. From To BH No. Oedometer test BM 4591A 24.3 24.65 HE-03 3 BM348B 25.7 26.05 HE-03 4 BM 3369 28.15 28.5 HE-03 2 BM 1641A 29.2 29.55 HE-03 3 Table 4: Depth of the Soil Sample Moisture Content The moisture content is determined for every soil sample (each sample tube) by overnight oven drying. The average of the duplicate of the moisture content of the soil sample is taken as the value of the moisture content for each sample.

SOIL SAMPLE MOISTURECONTENT (%) BM4591A 28.218 BM348B 27.167 BM3369 23.591 BM1641A 24.740 Table 5: Moisture content of soil sample

51 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Atterberg’s Limit The Atterberg’s limit is conducted on each of the soil sample. The soil length for every soil sample is just limited so the trimmed soil while preparing the soil specimen is used for the index test. This soil is believed to be in its natural moisture content or natural state. The liquid limit is determined using the cone penetrometer method. The soil paste is prepared by adding distilled water to the soil and mixing it using two palette knives until it is homogeneous. The Liquid limit and Plastic limit values obtained from the tests are consistent with the values found in the literature. The Liquid Limit and the Plasticity Index was plotted on the A- line plot (A-line plot on the Appendix).

ID No. LL PL PI BM 4591A 65 28 37 BM348B 69 28 41 BM 3369 55 25 30 BM 1641A 59 30.6 28.4

Table 6: Liquid Limit, Plastic Limit and Plasticity Index

Bulk and Dry Density The Bulk and Dry Density of the soil specimen are determined from the weight of the soil sample that is trimmed in a cylindrical shape with dimensions equal to the dimension of the oedometer ring. The weight of the soil specimen is determined as well as its volume. The average bulk density and dry density is determined for every soil sample.

Test Bulk Density (Mg/m^3) Dry Density (Mg/m^3) BM4591A 1.973 1.545 BM348B 1.964 1.546 BM3369 2.002 1.620 BM1641A 2.003 1.599

Table 7: Bulk and Dry Density of Soil Samples

Particle Density A gas pyknometer is used to determine the particle density of each of the soil sample (each sample tube). The gas pyknometer make use of helium gas that will be able to mix up and enter the pores of the soil. The mixing up of the helium gas and a certain weight of oven- dried powdered soil takes place at approximately 10 minutes and the particle density is determined at certain time interval. The last value recorded is believed to be the particle density of the soil since it is believed the helium gas is already well mixed up with the soil. The soils specific gravity can be calculated by dividing the particle density of the soil by the density of 3 water (H2O density = 1 g/cc or 1Mg/m ).

Sample Density (Mg/m3) Specific Gravity BM3369 2,63 2,63 BM1641A 2,65 2,65 BM4591A 2,66 2,66 BM348 2,65 2,65

Table 8: Particle Density and Specific Gravity of the soil samples

52 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Grain Size Distributiion In determining the grain size distribution of the Boom Clay that is used as a specimen in the consolidation test, hydrometer test are carried out on the soil samples. The hydrometer test result of Boom Clay is shown in the figure. (calculation on Appendix I)

Grain size distribution Grain size distribution in situ

100 90

) 100 ) % 80 90 ( % ( g 80 n 70 g n 60 70 assi 60 assi p 50 p e 50 e g

g a 40 40 t a t 30 30 cen cen r

r 20 e

20 e P

P 10 10 0 0 0,0001 0,001 0,01 0,1 1 10 0,0001 0,001 0,01 0,1 1 Gra in size (mm ) Grain size (mm)

Grain size distribution Grain size distribution in situ

100,000 100,000 ) ) 90,000

90,000 % % ( (

80,000 80,000 g g n n 70,000 i 70,000 60,000 60,000 ass assi p p 50,000

50,000 e e

g g 40,000 40,000 a a t t 30,000 30,000 cen cen

r 20,000

r 20,000 e e

P 10,000 P 10,000 0,000 0,000 0,0001 0,001 0,01 0,1 1 10 0,0001 0,001 0,01 0,1 1 10 Grain size (mm) Grain size (mm)

Grain size distribution Grain size distribution in situ

100,000 100 90,000 90 ) )

80,000 % 80 (% (

g g 70 n 70,000 n i i s

s 60,000 60 a ass p 50,000 p 50 e e g g

40,000 a 40 ta t n

e 30,000 30 c cen r r e 20,000 e 20 P P 10,000 10 0,000 0 0,0001 0,001 0,01 0,1 1 10 0,0001 0,001 0,01 0,1 1 Grain size (mm) Grain size (mm) Figure 29. Grainsize distribution of BM348B, BM4591,BM1641A, BM3369, BM3369 and BM1641A

53 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

8. Laboratory Test Results and Analysis

8.1. Difference between the Old and New Oedometer ring One of the strain gauges of the old lateral stress oedometer ring (Hegtermans, 2003) was damaged during its fabrication; some corrections have to be applied to compensate for this damage. During the insertion of the soil specimen in the lateral stress oedometer ring, the pump pressure in the deformed strain gauge is higher compared to the other strain gauges. In the new lateral stress oedometer ring, all three strain gauges are in good condition. Another difference in the two lateral stress oedometer rings is that the connection of the wirings for the strain gauges (P0, P1 and P2) was placed at a higher elevation compared to the first lateral oedometer ring such that water could not reach it since it would give errors in the three gauges readings. The new ring has a thicker diaphraghm (see figure…) compare to that of the old oedometer ring, one advantage of this thicker gauge is that it can support a higher pressure compared to the thin one. It could also be that such thicker gauge is not that sensitive to small stresses. There are few differences between the old and new oedometer ring. One relevant difference is the fluctuation of the pump pressure on the lateral stress gauge that is embedded in the oedometer ring. The old oedometer ring that was used in the first few laboratory test before the new oedometer ring was made available has a fluctuation of around 50 kPa. Sometimes the fluctuation of the pump pressure reaches 100 kPa and that gives the conclusion that the old oedometer ring needs to be replaced. In the new oedometer ring, the fluctuation of the pump pressures is around 10 kPa. It is more stable in terms of pump pressure that acts on the strain gauges in the new oedometer ring.

Boom 3369A North to P0

1400

1300

1200

1100

1000 (kPa)

e channel 4 corr r channel 5 corr 900 essu channel 6 corr Pr

800

700

600

500 280000 290000 300000 310000 320000 330000 340000 350000 Time

Figure 30. Pump Pressure from the old oedometer ring

54 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Boom 1641A North to P0

1100

1000 900 800

700 Pa)

k 600 channel 4 corr ( e channel 5 corr 500 channel 6 corr essur Pr 400 300 200 100

0 200000 210000 220000 230000 240000 250000 260000 270000 280000 Time Figure 31. Pump Pressure from the new oedometer ring

Diaphragm – from 0.2mm to 0.3mm

Figure 32: strain gauge thickness difference of the old and new ring

8.2. Lateral Stress Oedometer used in the Calculation of the minimum and maximum stress of the soil The Lateral stress used in the calculation of the minimum and maximum stress of the soil being tested is the effective stress. From the graph the stress used in the Mohr calculation is the effective stress. 900

re u s 800 s Pre

) 700 Pore a kP (

ss tal Stress e essur r P

600 To

ective str f 500 Ef

400 170000 180000 190000 200000 210000 220000 Figure 33: Total Stress, EfTimefective stress and Pore pressure during load application

55 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Vertical Effective Stress Effective stress is the sum of the vertical components of the forces developed at the points of contact of the solid particles. At a certain depth z, the vertical effective stress

(σv’)/overburden pressure is equal to the total stress at depth z (σv) minus the water pressure (u) at such depth.

3 σ'v = σv - u Where: γb = the bulk density of the soil (kN/m ) 3 σv = γbz γw = the density of water (kN/m )

u = γwh z = the depth where the overburden pressure is calculated (m) h = the height of the groundwater level above z (m)

8.3. Test Results of the Lateral Stress Oedometer Hegtermans(2003) identified three criteria in determining whether a specimen shows horizontally isotropic or anisotropic behaviour. These three criteria are the stress ratio, Mohr circle’s radius and the values of 2θ. The combination of these three criteria should be used in deciding the isotropy or anisotropy of the specimen. The following criteria are as follows:

1. if stress ratio (stressmax/stressmin) < 1.2 then specimen is probably isotropic, otherwise anisotropic. This is due to the sensitivity of the apparatus. 2. if the mohr circles radii is generally smaller than 50 kPa then it is isotropic but if the radius increases with applied vertical load of about 10 per 100 kPa then anisotropic. 3. If 2θ’s value varies between -90L and +90L then it is isotropic but if 2θ’s variability is less than 30 degrees then anisotropic

8.3.1. Consolidation Test on Boom Clay and Analysis of its Anisotropy One of the main objectives of this research project is to determine the stress history of Boom Clay and together with it, the isotropy or anisotropy of the soil in response to the vertical load will be determined. Tests conducted on the Boom Clay are Index Testing (chapter 7) and oedometer test using the lateral stress oedometer. Each of the soil samples is being analysed individually since each of this sample have an imaginary reference line/imaginary north. The calculation of the Mohr circle is available in the appendix where ratio of maximum and minimum stress is calculated for each specimen for every load step. The value of the radii of the Mohr circle is also determined as well as the value of 2θ.

Lateral Stress Oedometer Test

Boom3369 There are two soil specimen from this soil sample tested in the old lateral stress oedometer (oedometer ring used by Hegtermans). Both test had its imaginary north in line with the strain gauge P0 (Pump 1). The ratio of the minimum and maximum stress in the two test for this soil sample are both greater than 1.2, while mohr circle’s radii are greater than 50 KPa and the radius is increasing as the load increases (calculation in the appendix – mohr circle calcu-

56 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

lation). The three criteria determined will probably suggest an anisotropic lateral stress in response to the vertical loading.

Ratio 2θ Azimuth (max) BM3369-T1 1,432 -70 145 -325 BM3369-T2 1,835 -74 143 -323

Table 9: Ratio Maximum and Minimum Stress and Imaginary Azimuth of BM3369

Boom4591A This soil sample has a depth of 24.3 to 24.65 m and there are 3 specimens tested in the new lateral stress oedometer. The three tests conducted on the lateral stress oedometer had its reference line on the strain gauge 1(P0) that is attached to pump1. The ratio between the maximum and the minimum stress in the sample varies from 1.249 – 1.5508 The ratio between the maximum and minimum stress is greater than 1.2 and the mohr circles radii is greater than 50 KPa while the radius is increasing with the load. Therefore, the three criteria would tend to suggest that the specimen has an anisotropic lateral stress in response to the application of the vertical loads. Considering these three repetitive tests, the standard deviation of the azimuth is 11.96L.

Ratio 2 theta Azimuth (max) BM4591A-T1 1,551 -78 158 -322 BM4591A-T2 1,249 -65 147 -295 BM4591A-T3 1,327 -30 165 -345

Table 10: Ratio Maximum and Minimum Stress and Imaginary Azimuth of BM4591A

Boom1641A This soil sample was extracted from the depth of 29.2 to 29.55 m. There are 3 repetitive tests done on this soil sample. Two of the soil specimen that are tested in the oedometer has its imaginary north in line with the strain gauge that is attached to pump1 (P0) and the other test was in line with the strain gauge that is attached to pump3 (P2). The values of ratio of the specimen’s maximum and minimum stresses are 1.371, 1.3835 and 1.1361. With the three repetitive oedometer tests, the standard deviation of the azimuth its imaginary North relative to the maximum stress is 15.41L.

Ratio 2θ Azimuth (max) BM1641A-T1 1,371 17 8 -188 BM1641A-T2 1,380 -38 161 -341 BM1641A-T3 1,136 14 7 -187

Table 11: Ratio Maximum and Minimum Stress and Imaginary Azimuth of BM 1641A

Boom348B There are 4 specimens from this soil sample. The 1st, 2nd, 3rd and 4th laboratory tests on the lateral stress oedometer has its imaginary north in line with the strain gauge P2, P1, P2 and P0 respectively. The second test has some technical problems in carrying out the automatic change in the vertical load. Before the continuation of such oedometer test, such soil speci-

57 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

men was subjected to series of loading and unloading which probably affect the whole test. This technical problem can be reflected in the value of 2theta that is really very different from the other three tests. From the three repetitive tests of this soil sample, the standard deviation of the azimuth of its imaginary north relative to its maximum stress is 22.80L.

Ratio 2θ Azimuth (max) bm348B-t1 1,147 5 88 -268 bm348B-t3 1,170 2 89 -269 bm348B-t4 1,295 -82 49 -229

Table 12: Ratio Maximum and Minimus Stress and Imaginary Azimuth of BM 348B

8.3.2. Discussion of the Test Results There are 11 laboratory test done in the lateral stress oedometer where Boom Clay as the specimen. Most of these tests have seven (7) load steps and 3 unloading steps. The load steps are 100, 200, 400, 800, 1600, 2000 and 2400 kPa while the unload steps are 1200, 500 and 100 kPa. The ratio of the maximum and minimum stress for each load steps are calculated and the average of such ratios (excluding the first few load steps and unloading steps) can be calculated using these values. The calculated average value is approximately the ratio of the maximum and minimum stress of such test. The azimuth of the assumed north of the soil specimen is calculated from the value of its 2θ.

Name of Test Ratio 2θ (°) Azimuth of maximum horizontal stress Average Azimuth of Horizontal stress Depth relative to imaginary reference line (relative to imaginary north of each sample) (m) BM3369-T1 1,432 -70 145 -325 28,15 -28,5 144 -324 BM3369-T2 1,835 -74 143 -323 28,15 -28,5 bm348B-T1 1,147 5 88 -268 25,7 -26,05 bm348B-T3 1,170 2 89 -269 75 -255 25,7 -26,05 bm348B-T4 1,295 -82 49 -229 25,7 -26,05 BM4591A-T1 1,551 -78 158 -322 24,3 -24,65 BM4591A-T2 1,249 -65 147 -295 157 -321 24,3 -24,65 BM4591A-T3 1,327 -30 165 -345 24,3 -24,65 BM1641A-T1 1,371 17 8 -188 29,2 - 29,55 BM1641A-T2 1,380 -38 161 -341 179 -359 29,2 - 29,55 BM1641A-T3 1,136 14 7 -187 29,2 - 29,55 average 1,354 stdev 0,204

Table 13: Boom Clay Oedometer Test Results

The average value of the ratio of the maximum and minimum stress is 1.354 that probably suggests that the Boom Clay has an anisotropic lateral stess in response to the vertical loads applied, and this demonstrates anisotropic stiffness in the horizontal plane. Thus, it cannot be concluded that the Boom Clay in the Western Scheldt area is cross-anisotropic. Due to limited length of the soil sample, there are only 2-4 laboratory tests done on each soil sample. It was not possible to assess the true azimuth of the stiffness anisotropy, however the duplica- tion of test specimen from each sample suggests that the direction (azimuth) is relatively consistent. Oriented core samples would be required to assess the true azimuth.

58 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

8.3.3. Lateral Stress Plot vs. Settlement Curve In the lateral stress oedometer test, the total lateral stress on the soil sample is measured 140.000 120.000

on 100.000 and recorded. From the graphs of the lateral ti pa i settlement curve

s 80.000 stresses as compared to the time-settlement s lateral_stress di

f 60.000 o curve, it can be clearly observed that the e 40.000 m Ti duration of time where the pore water 20.000 0.000 pressure dissipates from the soil from the 100 200 400 800 1600 2000 2400 time of the application of the vertical load is Load (KPa) 120.000 approximately the same duration of time as 100.000 n o i t

the settlement curve graphically gives a 80.000 p i

s settlement curve s 60.000 information that the primary lateral_stress

of di 40.000 e

consolidation/settlement took place and m i T secondary consolidation is about to start. 20.000 0.000 From the settlement curve and the lateral 100 200 400 800 1600 2000 2400 Load (KPa) stress graph, the time at which the porewater 200 dissipates from the sample was being deter- 180

n 160

io 140

mined. From the different loading steps of the at

ip 120 settlement curve ss

i 100

soil specimen tested on the lateral stress d

lateral_stress f 80 o

e 60

oedometer ring, the time was approximately m i

T 40 equal, so therefore the effective stress was 20 0 used to determine the Mohr circle and other 100 200 400 800 1600 2000 2400 Load (KPa) calculations done in line with the oedometer 200.00 testing. The maximum difference of the two 180.00

n 160.00 o i

t 140.00 is around 11% while for the majority of the a p

i 120.00 s settlement curve s 100.00

loadsteps, its difference is approximately 5%. di lateral_stress f 80.00 o

e 60.00 Aside from attaching a transducer that will be m

Ti 40.00 20.00 able to determine the porewater pressure dur- 0.00 100 200 400 800 1600 2000 2400 ing loadsteps, this graphical solution can be Load (KPa) an alternative method to measure the excess 300.00 pore pressure generated due to loading. 250.00 on i t 200.00 pa i s settlement curve s i 150.00 d lateral_stress of 100.00 e m

Ti 50.00

0.00 100 200 400 800 1600 2000 2400 Load (KPa)

Figure 34: Time needed for water to dissipate after a vertical load is applied. (From the settlement curve and lateral stress graph)

59 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

900

u s 800 s Pre

) 700 Pore a kP (

ss tal Stress e

essur r P

600 To

Time(t) ective str f 500 Ef

400 170000 180000 190000 200000 210000 220000 Time

-1.5 -0.5 0.5 Log-Time 1.5 2.5 0.10000

0.15000

0.20000

0.25000 0.30000 Series1 0.35000

0.40000 Time(t)

0 45000 Figure 35: Time needed for water to dissipate after a vertical load is applied. From these graphs (time-settlement curve and lateral stress graph)

8.4. Preconsolidation Pressure The Pre-consolidation Pressure of the soil specimen was calculated using the method of Casagrande and Butterfield. Some settlement data of the oedometer test carried out to some of the specimen are not available due to technical problems (non-function of the settlement gauge, improper placement of the gauge..etc.). There are only seven calculations for the preconsolidation pressure using the new lateral stress oedometer out of ten oedometer test.

BM4591T1 BM348T1 BM348T3 BM348T4 BM1641T1 BM1641T2 BM1641T3 Casagrande 790 980 860 900 900 850 670 Butterfield 795 980 870 910 900 850 660

Table 14: Preconsolidation Pressure of Boom Clay samples

60 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

9. Conclusion and Recommendations

9.1. Conclusion The issues in this present research project are (1) the assumption that Boom Clay is cross- anisotropic at the beginning of this research (2) the revised objective due to the oedometer test results that tend to suggest that the Boom Clay has anisotropic response to the application of vertical load that also includes the performance of the new lateral stress oedometer;

At the start of this research project, it was assumed that the overconsolidated Boom Clay is cross-anisotropic since its stress history primarily consists of geologic deposition and erosion. With this assumption, it was also proposed to test such clay in a Bender Element so as to measure the small strain shear modulus in the principal directions (vertical and horizontal). From the first few oedometer test using the old and new lateral stress oedometer ring, the Boom Clay displayed anisotropic response to the vertical load application. S Since it cannot be concluded that the Boom Clay is cross-anisotropic and it is not possible to determine the orientation of the maximum and minimum stress of the Boom Clay samples, the Bender Element Testing on such deposit was eliminated. Taking into account the anisotropy of the horizontal stresses after applying a vertical load, the primary objective of this research project is to assess the lateral stresses in the overconsolidated Boom Clay and to compare it with the research of Hegtermans (2003), who conducted a research about deposits overrun by glaciers (Potclay). To assess the performance of the new lateral stress ring: a comparison of the old lateral oedometer & new oedometer ring as well as elaborating some small modifications made in the design of the ring. S One of the diaphragms of the old oedometer ring was deformed while in the new oedometer ring, the three diaphragms are in good condition and the connection of the strain gauge is already secured from the water surrounding the specimen. This seems to improve the performance of the apparatus. S The thickness of the diaphragm of the new oedometer ring is 0.3 mm while the old ring has 0.2mm. The thicker diaphragm will be less susceptible to damage during high vertical loads and at the same time the thicker diaphragm seems to be sensitive to small changes of stress. S Another modification that was recommended for the new oedometer ring was to attach a transducer that will be able to determine the excess pore pressure during the loadsteps. But such recommendation was not materialized in the new oedometer ring used in the tests in this research project (due to time and budget constraints). An alternative method to measure the excess pore pressure generated due to loading is by graphical determination from the time-settlement curve and lateral stress graph (Figure 35).

61 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

To assess the lateral stresses in Boom Clay, oedometer tests were done. S The tests results suggest that the Boom Clay in the Western Scheldt area has some degree of anisotropy with respect to its response to the applied vertical load. It seems there is anisotropic stiffness of the deposit in its horizontal plane. S From the lateral stress oedometer result, the value of the ratio of the maximum and minimum horizontal stress in Boom Clay is 1.354 while that of the Pot clay is 1.65 (Hegtermans, 2003). These values suggest that the magnitude of the anisotropy of the Boom Clay is lesser than that of the Pot clay at Marum which has been overrun by glaciers. S The anisotropic stiffness in the horizontal plane of the Boom Clay in Western Scheldt can probably be due to geological processes such as uplift and flexure or bending of such deposit. Schokking et. al.(1995) said that the Boom Clay in the Western Scheldt has fissures that are due to stress relief during tectonic uplift and subsequent erosion while Dehandschutter et al. concluded that these fractures are results of the combination of compaction and consolidation as well as uplift and bending .The tests results seems to agree with the findings of Dehand- schutter.

9.2. Recommendations: These are the recommended further study on Boom Clay.

S Lateral stress oedometer tests should be carried out on oriented core samples of Boom Clay inorder to determine the true azimuth of the maximum stress and this should be compared to the axis of bending inferred by Dehandschutter et al.,(in press). S It appears that the Boom Clay at this location (Western Scheldt) has a stress history much more complicated than geological sedimentation and erosion and it does not display cross-anisotropy. Testing of Boom Clay from another site location is recommended to determine its cross-anisotropy or anisotropy. S In-situ Testing of the Boom Clay with the use of a Load Cell Pressuremeters, to correlate the results obtained from in-situ and laboratory test. From such test, the direction of the major and minor horizontal stresses of the Clay can probably be determined.

62 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

REFERENCES

Arramon, Y., Mehrabadi, M., Martin, D., Cowin, S., 2000. A multidimensional anisotropic strength criterion based on Kelvin modes. International Journal of Solids and Structures Vol. 37 No. 21, 2915-2935 Arroyo, M. & Muir Wood, D., 2003. Simplifications related to dynamic measurements of anisotropic G0. Deformation Characteristics of Geomaterials, Di Benedetto et. al. (eds) Barnichon, J. –D., 2001. Contribution of the bounding surface plasticity to the simulation of gallery excavation in plastic clays. Engineering Geology 64, 217-231 Bernier, F., Volckaert, G., Alonso, E., Villar, M., 1997: Suction-controlled experiments on Boom Clay. Engineering Geology vol. 47, 325 – 338 Blewett, J., Blewett, I.J. & Woodward, P.K., 2000: Phase and amplitude responses associated with the measurement of shear-wave velocity in sand by Bender Elements. Canada Geo- tech. J. 37: 1348-1357 Bultynck, P. & Dejonghe, L. eds, 2001. Paleogene and Neogene lithostratigraphic units(Belgium). Geologica Belgica, Brussels vol. 4/1-2, 135-152 Butterfield, R., 1980. A natural compression law for soils (an advance on e-logp’). Techni- cal Note Burck, H. D. M.,Van Eerde, L. A., Harsveldt, H.M., Van der Heide, S., De Jong, J.D., Pan- nekoek, A. J., Van Voorthuysen, J.H., Ter Wee, M. W., Zagwijn, W.H. and Zonneveld, J.I.S., 1956: Geological History of The Netherlands – Netherlands, Government Printing and Pub- lishing Office Cortellazzo, G., 2002: Comparison between laboratory and in situ values of the coefficient of primary consolidation. Can Geotech J. 39: 103-110 Das, B., 1979. Introduction to Soil Mechanics. Ames: Iowa State University Press. Dehandschutter, B., Vandycke, S., Sintubin, M., Vandenberghe, N. and Wouters, L. (in press): Towards an Understanding of brittle fractures and ductile shear bands in argillaceous sediments: inference from Oligocene Boom Clay in its outcrop area (Belgium) Delage, P., Sultan, N. and Cui, Y. J., 2000: On the thermal consolidation of Boom Clay. Can. Geotech. J. 37: 343-354 Deniau, Derenne, Beaucaire, Pitsch and Largeau, 2001. Morphological and chemical features of a kerogen from the underground Mol laboratory (Boom Clay Formation, Oligocene, Belgium): structure, source organisms and formation pathways Dyvik, R., Lacasse, S., Martin, R., Coefficient of lateral stress from oedometer cell Edited by: Degryse and Sintubin, 2002. Contributions to the Geology of Belgium and North- West Europe – Proceedings Gareau, L., Molenkamp, F., Sharma, J., Hegtermans B.H.M., in press. Engineering Geology of Glaciated Soils. Hanzawa, H., 1995. In Situ shear strength of marine clay related to aging effect. DGF Bulle- tin 11. Proceedings XI ECSMFE pp. 1.141-1.146 Hegtermans, B.M. H., 2003: The Measurement of anisotropic horizontal stresses in the Pot Clay. Faculty of Applied Earth Sciences, TU Delft, Delft

63 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Houtgast, R.F., van Balen, R. T., Kasse, C. & Vandenberghe,J., 2003: Late Quaternary tectonic evolution and postseismic near surface fault displacements along the Geleen Fault (Feldbiss Fault Zone – Roer Valley Rift System, the Netherlands), based on trenching. Netherlands Journal of Geosciences/Geologi en Mijnbouw 82(2): 177-196 Huybrechts, N., Maertens, J. & Mengé, P., 2002. Resultaten van een uitgebreide Grondon- derzoekscampagne in de Boomse Klei te Sint-Katelijne-waver. Geotechneik no.4 18-29 Jamiolkowski, M., Lancellotta, R. & Lo Presti, D.C.F.,1995. Remarks on the stiffness at small strains of six Italian clays. Developments in Deep Foundations and Ground Improve- ment Schemes, Balasubramaniam et. al.(eds) Laenen, B., De Craen, M., 2003: Eogenetic siderite as an indicator for fluctuations in sedimentation rate in the Oligocene Boom Clay Formation. Sedimentary Geology. Sedimentary Geology. Elsevier B.V. Lee, I. K., White, W. & Ingles, O. G.; 1983. Geotechnical Engineering – Marshfield, Massa- chusetts, Pitman Publsihing Inc. Mitchell, J. K., 1976. Fundamentals of Soil Behavior. Copyright by John Wiley & Sons, Inc., printed in the United States of America. NASA Website: [(Milankovitch Cycles—Changes in Earth-sun Interaction Alaska Science Forum: The Earth's Changing Orbit ) ;J.D Hays, John Imbrie, and N.J. Shackleton, "Varia- tions in the Earth's Orbit: Pacemaker of the Ice Ages," Science, 194, no. 4270 (1976), 1121- 1132.; Hays, James D., 1996: Encyclopedia of Weather and Climate, Oxford University Press, Stephen H. Schneider, ed. pp 507-508; Lutgens, Frederick K. and Edward J. Tarbuck, 1998: The Atmosphere, Prentice-Hall, Inc., 434pp. ;National Research Council, Solar Vari- ability, Weather, and Climate, Washington, D.C.: National Academy Press, 1982, p. 7. ] http://earthobservatory.nasa.gov/cgibin/texis/webinator/printall?/Library/Giants/Milankovitc h/milankovitch_3.html Olson, R. E., 1998: Settlement of embankments on Soft Clays. Journal of Geotechnical and Geoenvironmental Engineering, Vol. 124 paper no. 17354. Onitsuka, K., Hong, Z.,Hara, Y. and Yoshitake, S., 1995. Interpretation of oedometer test data for natural clays. Soils and Foundation (Japanese Geotechnical Society) vol. 35, no.3 61- 70

Pennington, D. S., Nash, D. F. T., and Lings, M. L., 1997. Anisotropy of G0 shear stiffness in Gault Clay. Geotechnique 47, No. 3, 391-398 Pennington, D. S., Nash, D. F. T., and Lings, M. L., 2001. Horizontally Mounted Bender Elements for Measuring Anisotropic Shear Moduli in Triaxial Clay Specimens. Geotechnical Testing Journal, GTJODJ, Vol. 24, No. 2, 133–144. Ramiah, B. K., Chickanagappa, L.S., 1986 : Soil Mechanics and Foundation Engineering. A.A. Balkema/Rotterdam Rijkers, R., Hemmen, B., Naaktgeboren, M. & Weigl, H., 2002. In situ frost heave loads in artificially frozen ground for tunnelling. In: Proceedings International Tunnel Association, Sydney, Australia. Robinet, J-C., Rahbaoui, A., Plas, F., Lebon , P., 1996. A constitutive thermomechanical model for saturated clays. Engineering Geology 41, 145-169

64 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Romero, E., Gens, A., and Lloret, A., 1999. Water permeability, water retention and micro- structure of unsaturated compacted Boom clay. Engineering Geology Vol. 54 No. 1-2, 117- 127 Salgado, R., Bandini, P. and Karim, A., 2000: Shear Strength and stiffness of silty sand Jour- nal of Geotechnical and Geoenvironmental Engineering, Vol. 126, No. 5, 451-462. Schittekat. J., Henriet, J.P. & Vandenberghe, N., 1983. Geology and geotechnique of the Scheldt Surge Barrier, characteristics of an overconsolidated clay. In: Proceedings 8th Itern. Harbour Congress. KNV Antwerp Schokking, F and Nooy van der Kolff, 1995: History and Geotechnical Properties of the marine Boom Clay. DGF-Bulletin 11 vol. 7 Schokking, F.; 1998. Anisotropic strength behaviour of fissured overconsolidated clay in relation to Saalian Glacial directions. Engineering Geology 49 31-51 Simonini, P. and Simonetta, C., 2000. Use of Piezocone to predict maximum stiffness of Ve- netian Soils Cola Journal of Geotechnical and Geoenvironmental Engineering,Vol. 126, No. 4, April, 2000. Skempton, A.W., 1970: The consolidation of clays by gravitational compaction. Geol. Soc. Lond. Vol. 125 pp. 373-411. printed in Northern Ireland Stratigraphic nomenclature: Section I – Tertiary – Sep. 1997 – Mededelingen Rijks Geolo- gische Dienst Nr50 1997 Sridharan, A., Abraham, B. M. & Jose B. T., 1991. Improve technique for estimation of preconsolidation pressure. Geotechnique 41, No. 2, 263 - 268 Sultan, N., Delage, P. Cui Y.J., 2002 : Temperature effects on the volume change behavior of Boom Clay. Engineering Geology 64 135-145 Tan, T.S.,Lee, F. H., Chong P.T. and Tanaka H., 2002. Effect of Sampling Disturbance on Properties of Singapore Clay. Journal of Geotechnical and Geoenvironmental Engineering, vol. 8 898-906 Vandenberghe, N., Laenen, B., Van Echelpoel, E. & Lagrou, D., 1997. Cyclostratigraphy and climatic Eustasy. Example of the Rupelian Stratotype. Earth and Planetary Sciences 325, 305-315 Van Impe, W. F., 1997. Boom Clay for storage of nuclear waste. Geotechnical Engineering of Hard Soils-Soft Rocks, Anagnostopoulos et. al.(eds.) 1997 Balkema, Rotterdam 1885-1895 Van Staalduinen, C.J., Van Adraichem Boogaert, H.A., Bless, M.J.M., Chr. Doppert, J.W., Harsveldt, H.M., Van Montfrans, H.M., Oele E., Wermuth, R.A. and Zagwijn, W.H., 1979. The Geology of the Netherlands. Mededelingen rijks geologische dienst vol. 31-2 Viggiani, G. & Atkinson, J. H., 1995. Stiffness of fine-grained soil at very small strains. Geo- technique, 45, No. 2, 249 – 265 Viggiani, G. & Atkinson, J. H., 1995. Interpretation of bender element tests. Geotechnique, 45, No. 2, 149 - 154

Zeng, X., Ni, B.,1999. Stress-Induced Anisotropic Gmax of Sands and its measurements. Jour- nal of Geotechnical and Geoenvironmental Engineering vol. 125, No. 9, 741-749

65 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

APPENDICES

Appendix A: CONSOLIDATION SYTEM USED FOR THE CONSOLIDATION TEST (From Hegtermans, 2003)

Literature review of lateral stress oedometers

Several researches have developed oedometer apparatuses that measure vertical as well as horizontal stresses. Dyvik et al. (1985) presented a new oedometer ring developed especially for measuring lateral stresses during a consolidation test. A central portion of the oedometer ring contains a teflon membrane behind which is a chamber surrounding the specimen filled with de-aired water. The lateral stress exerted on the membrane by the specimen during testing, pressurises the water and is monitored by a transducer. Zentar et al. (1998) designed a similar oedometer ring with an oil-filled chamber inside the ring, separated from the specimen by a membrane. Strain gauges are stuck onto this membrane. Song et al. (1985) designed a new oedometer ring specifically for measuring lateral stress and pore pressure during consolidation tests. A triaxial cell was remodelled as an oedometer. Two pressure transducers were installed in the ring wall to measure horizontal stress. These three oedometer rings were not suitable for this thesis because they all measure an average horizontal stress and can therefore not result in an anisotropic lateral stress field. Kolymbas and Bauer (1993) developed the soft oedometer as an alternative to triaxial testing; with this apparatus it is possible to measure horizontal as well as vertical stress and strain. The lateral pressure is indirectly measured by means of an elastic lateral supporting ring with strain gauges attached to it. This soft oedometer is designed for tests with cohesionless granu- lar material, so it was not suitable for this thesis, because the research material is clay. The authors also state that the results obtained with the soft oedometer cannot be compared to conventional oedometer test results. Senneset (1989) developed the split ring oedometer that allows for tests with a controlled lateral deformation. The purpose is to measure and evaluate the in situ coefficient of earth pressure at rest (K0). The supporting ring of the new oedometer is splitted into three parts. The mounting of an undisturbed specimen into the ring is easy because the ring is clamped around the sample. In each part of the ring the contact pressure between specimen and ring can be measured, also allowing the application of an initial horizontal stress situation. The lateral stress can be measured during the consolidation process. This apparatus seems suitable for this thesis, though the lateral stresses are not measured in 3 points, but along the whole length of all three parts of the ring. The data obtained with this ring would give enough information to calculate the minimum and maximum lateral stress axis. However, the test is controlled by lateral deformation: The lateral stresses cannot be measured without allowing the specimen to deform. That is the reason why this system was not used for this thesis.

66 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Colmenares (2001) developed an oedometer ring with four diaphragms machined into the side at 90˚ angles. The diaphragms are equipped with strain gauges. As lateral stresses increase in response to vertical loading of the specimen, oil pressure is applied to the diaphragms until the average strain gauge reading returns to zero. The oil pressure required to counteract the strain gauge reading is the average lateral stress acting on the specimen. This apparatus cannot measure anisotropic lateral stresses.

Anisotropic lateral stress oedometer A new oedometer ring was developed for this research, based on the principle of the design by Colmenares (2001). The main difference is that the new apparatus has three independent diaphragms, so that anisotropic stress response can be measured. It is a thick-walled steel ring with three openings offset 120°. These openings were machined into the steel ring, leaving a 0.2 mm membrane on the inner side of the ring. Strain gauges are attached to these mem- branes. The ring will hold a sample of 50mm diameter and 30mm height.

Figure A.1: The developed lateral stress oedometer ring. In the top view, the two ways of numbering are shown: the pressure controllers have numbers p0 to p2. These correspond with the membrane numbers 1 to 3.

Testing system A soil specimen is inserted in the ring such that the centroid of the specimen bears against the diaphragms. Porous stones above and below the specimen permit drainage during loading. As vertical loads are applied to the specimen deflections are measured and recorded, as in a standard oedometer test. A displacement meter with an accuracy of 0.001mm rests on the bottom plate of the ACONS. It is connected to an mpx3000 datalogger and a computer. The

67 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

computer runs winclisp under windows; this specialised software controls the test and col- lects the data of the vertical displacement meter. It can also be programmed to automatically add load increments at a specified time interval.

Figure A.2: The testing system. As vertical loads are applied to the specimen, an increment of total stress is transferred to the walls of the oedometer and thus to the thin wall diaphragms. In response to this stress, the diaphragms try to deflect outwards, generating an electrical signal across the strain gauges. The computer responds to this signal by increasing pump pressure until the strain gauge signal reduces to zero, i.e. until there is no deflection on the diaphragm. The pump pressure is then taken to equal the lateral stress at that location. As excess pore pressures dissipate, the measured lateral stress will likewise decrease to a steady value. This stabilised pressure is the lateral effective stress that results for the applied vertical stress. Pump pressure for a typical load step follows the pattern in Figure A.3.

Figure A.3: Part of an output graph for pump pressure against time.

68 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Data interpretation Vertical time-settlement and e-log p data is analysed using the same procedure as for the standard oedometer test. For a detailed description see BS: 1377: part 5: 1990. The horizontal set up supplies a table of the time and pressures measured by the pressure controllers. This data is imported into excel from where it can be corrected and then processed. The necessary corrections will be described in the next section. S A graph of time versus measured pump pressure is drawn. Every step in the graph is a load step. Figure A.3 is a detail of one of these graphs. S This graph shows when the pressures of the three pressure controllers have stabilised. These pressures are recorded as the horizontal stresses resulting from the particular vertical applied load. S The three independent horizontal stresses are resolved using Mohr’s circles to determine the magnitude and orientation of the maximum and minimum horizontal stresses. The formulas shown in Figure A.4 are used for these calculations.

12 appp pp22pp2 ppppp τ 33012 0 1 2 011220

12 222 120˚ b p01pp2 ppp01 2p0p1p1p2p2p0 2θ 33 a p2 p1 p0 b σ 1 pp12 3 sin 2 2 222 p01p p2pp01p1p2pp20 3 Figure A.4: Mohr’s circle for stress with the formulas for calculating angle and minimum and maximum horizontal stress. After Dalton and Hawkins (1982).

69 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Appendix B: A-LINE PLOT

Appendix C: CALCULATION FOR CALIBRATION

Table 1: Calibration no. 1

ACTUAL P0 P1 P2 INSERT(ZERO VALUE) -22 36 -7 100 115 64 40 200 235 198 178 400 459 432 409 600 697 677 654 1000 1134 1124 1111 1200 1358 1353 1344 1600 1806 1809 1812 1000 1094 1109 1055 600 673 680 624 100 99 91 28

70 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Table 2: Calibration no. 2 ACTUAL P0 P1 P2 INSERT( ZERO V A LUE) 41-1 200 236 174 154 400 458 403 391 600 701 653 643 1000 1130 1090 1081 1200 1356 1311 1309 2000 1979 2029 1908 1000 1080 1029 1029 600 660 593 594 100 63 -4 -20

Table 3: Calibratiion no. 3 ACTUAL P0 P1 P2 INSERT(ZERO V A LUE) -45 -50 -56 1009030 0 200 190 149 111 400 415 378 340 600 652 624 591 1200 1295 1272 1252 1600 1716 1705 1693 2000 1979 2029 1908 1200 1251 1227 1217 600 614 588 564 100 18 -6 -36

Appendix D: CALCULATION OF RATIO MOHR CIRCLES MAXIMUM AND MINIMUM STRESS, 2 , RADIUS

Table no. 4 Boom 3369 –Test 1(using old lateral stress oedometer) Mohr Circle Calculations

Test: Sample of Boomclay, BM3369A-Test 1 * = Data corrected by subtracting "Insert" value and applying formulas. North to P0 Tested in lateral stress oedometer.

Vertical nitial - Peak Stable Corrected Stable* Mohr Circle Calculations Stress P1 P0 P1 P2 P0 P1 P2 min max ratio 2 Theta Radius

Before Insert 1111883030000.0 0.0 0.0 100 139 160 373 28 -28 52 -30.1 64.8 -2.15198 -77.2827 47.4 200 205 266 499 93 77 147 63.5 148.3 2.335143 -72.6759 42.4 400 320 360 691 207 169 295 149.1 298.4 2.001892 -77.3978 74.7 800 518 596 937 404 392 489 367.4 489.8 1.333257 -66.3993 61.2 1200 753 813 1244 638 590 741 567.2 745.1 1.313626 -78.0311 88.9 1600 960 1105 1527 844 845 981 798.8 981.3 1.228593 -59.4888 91.3 2000 1197 1331 1846 1080 1034 1263 985.8 1265.9 1.284173 -70.7828 140.1 1000 885 973 1348 769 731 828 719.8 832.5 1.156572 -82.7396 56.4 500 617 684 914 502 473 471 462.0 502.5 1.087679 3.829384 20.3 100 289 374 481 177 182 134 133.4 194.9 1.461089 66.05926 30.8

BM3369-T1 1.432308 -70.42

71 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Table no. 5 Boom 3369 –Test 2(using old lateral stress oedometer) Mohr Circle Calculations

Test: Sample of boomclay, BM3369A - Test 2 * = Data corrected by subtracting "Insert" value and applying formulas. North to P0 Tested in lateral stress oedometer.

Vertical nitial - Peak Stable Corrected Stable* Mohr Circle Calculations Stress P1 P0 P1 P2 P0 P1 P2 min max ratio 2 Theta Radius

Before -33 -36 -66 Insert 88 133 192 0 0 0 0.0 0.0 0.0

100 166 141 631 72 8 328 -59.4 331.6 -5.57887 -70.9402 195.5 200 202 148 641 106 15 336 -38.9 343.0 -8.82108 -75.9079 191.0 400 317 240 830 212 106 483 42.3 491.2 11.60011 -75.9088 224.4 800 532 428 1099 411 286 698 221.7 708.6 3.195841 -77.2547 243.4 1200 774 676 1437 636 516 978 433.2 987.1 2.278628 -74.4674 277.0 1600 1026 937 1778 870 748 1274 646.0 1282.1 1.98469 -72.8161 318.0 2000 1284 1198 2003 1110 970 1477 883.2 1487.7 1.684311 -75.5226 302.2 1200 1073 971 1758 914 777 1256 697.5 1267.5 1.817347 -76.0409 285.0 400 548 554 1044 426 404 653 335.6 653.6 1.94781 -64.5728 159.0 100 313 317 668 208 180 356 139.1 357.7 2.570896 -68.5299 109.3

1.8345 -74.2687

New Lateral Stress Oedometer

Table no. 6 Boom 1641A –Test 1 Mohr Circle Calculations

Test: Sample of Boom Clay - BM1641A-Test 1 * = Data corrected by subtracting "Insert" value and applying formulas. North to P0 Tested in lateral stress oedometer.

Vertical nitial - Peak Stable Corrected Stable* Mohr Circle Calculations Stress P1 P0 P1 P2 P0 P1 P2 min max ratio 2 Theta Radius

Before Insert 292 250 -155 0 0 0 0.0 0.0 0.0

300 295 241 -166 97 126 40 37.7 138.4 3.669306 79.1647 50.3 500 397 310 -71 190 187 124 124.1 210.5 1.696605 57.66982 43.2 800 536 403 32 317 270 215 208.2 326.4 1.567879 32.60913 59.1 1200 777 594 222 537 440 382 362.6 543.0 1.497708 21.60199 90.2 1600 1022 816 442 760 637 576 549.2 765.8 1.394494 18.9777 108.3 2000 1274 1052 680 990 846 785 752.7 994.8 1.32166 16.93645 121.1 2400 1535 1301 934 1227 1067 1009 970.7 1231.8 1.268995 15.02042 130.6 1600 1280 1096 727 995 885 827 803.7 1001.0 1.245483 20.12089 98.6 1200 1105 933 579 836 741 696 675.4 839.6 1.2431 18.15646 82.1 500 688 550 210 456 401 372 359.9 458.5 1.274001 19.86597 49.3 100 335 248 -104 134 132 95 95.1 145.8 1.534119 57.89652 25.4

BM1641A-T1 1.370714 16.97819

72 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Table no. 7 Boom 1641A –Test 2 Mohr Circle Calculations

Test: Sample of Boom Clay - BM1641A-Test 2 * = Data corrected by subtracting "Insert" value and applying formulas. North to P2 Tested in lateral stress oedometer.

Vertical nitial - Peak Stable Corrected Stable* Mohr Circle Calculations Stress P1 P0 P1 P2 P0 P1 P2 min max ratio 2 Theta Radius

Before Insert 78961360000.0 0.0 0.0 100 92 121 167 13 22 27 12.2 29.3 2.392327 -20.1799 8.5 200 112 170 236 31 66 88 28.4 94.8 3.339943 -22.8349 33.2 400 162 276 391 77 160 224 68.0 239.3 3.519768 -25.8294 85.6 800 273 486 612 273 486 612 259.1 654.9 2.527031 -21.5718 197.9 1600 678 930 1097 547 741 846 535.8 886.5 1.654428 -20.2992 175.3 2000 905 1161 1339 754 946 1059 969.6 1097.8 1.132282 -21.5045 64.1 2400 1155 1409 1583 981 1166 1274 969.6 1311.3 1.352411 -21.3654 170.8 1200 860 1107 1163 713 898 904 712.5 963.9 1.35285 -1.64774 125.7 500 555 653 711 435 495 506 434.1 522.9 1.204455 -8.63077 44.4 100 305 307 335 207 187 175 171.4 208.2 1.215054 22.46725 18.4

1.379707 -22.1141

Table no. 8 Boom 1641A –Test 3 Mohr Circle Calculations

Test: Sample of Boom Clay - BM1641A - Test 3 * = Data corrected by subtracting "Insert" value and applying formulas. North to P0 Tested in lateral stress oedometer.

Vertical nitial - Peak Stable Corrected Stable* Mohr Circle Calculations Stress P1 P0 P1 P2 P0 P1 P2 min max ratio 2 Theta Radius

Before Insert 211 153 171 0000.0 0.0 0.0 100 263 189 225 47 32 48 32.0 52.6 1.645954 -60.5093 10.3 200 306 228 266 87 67 84 66.5 91.4 1.374232 -52.1957 12.4 400 435 343 380 204 169 184 165.1 206.1 1.248042 -25.4733 20.5 800 645 560 563 395 361 345 337.7 397.0 1.175634 18.56846 29.7 1600 1072 1003 992 785 755 723 718.4 789.7 1.099255 31.33074 35.7 2000 1292 1216 1215 985 944 919 911.0 987.8 1.084308 22.03604 38.4 2400 1518 1446 1444 1191 1148 1121 1112.5 1194.1 1.073405 22.98472 40.8 1200 1156 1048 1127 861 795 842 793.2 871.8 1.099071 -43.4161 39.3 500 743 637 757 485 430 516 426.5 527.1 1.235901 -80.9478 50.3 100 403 312 390 175 141 193 139.4 199.9 1.43405 -79.9233 30.3

1.136129 13.88933

73 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Table no. 9 Boom 4591 –Test 1 Mohr Circle Calculations

Test: Sample of Boom 4591A-Test 1 * = Data corrected by subtracting "Insert" value and applying formulas. North to P0reference line at P0 Tested in lateral stress oedometer.

Vertical nitial - Peak Stable Corrected Stable* Mohr Circle Calculations Stress P1 P0 P1 P2 P0 P1 P2 min max ratio 2 Theta Radius

Before Insert 11691 2030000.0 0.0 0.0 100 155 115 267 36 21 56 17.4 57.9 3.331794 -85.285 20.3 200 188 134 337 66 38 118 27.1 120.9 4.456366 -80.1736 46.9 400 320 233 491 186 126 254 114.9 262.1 2.281594 -87.9503 73.6 800 545 394 744 391 269 476 258.5 498.8 1.929491 -84.1081 120.1 1600 1075 842 1288 874 667 955 660.4 1003.6 1.519628 -75.8936 171.6 2000 1348 1090 1551 1123 887 1187 883.4 1247.6 1.412255 -71.7399 182.1 2400 1634 1359 1836 1383 1126 1438 1123.5 1507.7 1.341978 -69.424 192.1 1200 1206 1010 1416 993 816 1068 809.6 1108.4 1.369107 -76.8466 149.4 500 748 609 902 576 460 615 457.2 643.4 1.407218 -73.9964 93.1

BM4591A-T1 1.696989 -77.8232

Table no. 10 Boom 4591 –Test 2 Mohr Circle Calculations

Test: Sample of Boom Clay - 4591Test2 * = Data corrected by subtracting "Insert" value and applying formulas. North to P0 Tested in lateral stress oedometer.

Vertical nitial - Peak Stable Corrected Stable* Mohr Circle Calculations Stress P1 P0 P1 P2 P0 P1 P2 min max ratio 2 Theta Radius

Before Insert 62 113 70 0 0 0 0.0 0.0 0.0 100 85 145 109 21 28 34 20.2 35.6 1.767812 -26.1786 7.7 200 115 182 162 48 61 81 44.5 82.5 1.854353 -36.773 19.0 400 210 282 277 135 150 182 127.8 183.7 1.437122 -41.6418 27.9 800 430 497 517 335 341 394 319.6 393.7 1.231866 -54.8836 37.0 1600 967 955 1059 825 748 871 742.7 886.0 1.193063 -81.7805 71.7 2000 1249 1208 1354 1082 972 1130 968.1 1154.8 1.192863 -77.5776 93.4 2400 1534 1454 1632 1341 1191 1375 1189.2 1415.6 1.190363 -69.9543 113.2 1200 1110 1093 1219 955 870 1012 863.5 1027.6 1.190029 -83.4859 82.0 500 710 682 786 590 505 630 501.6 649.1 1.293956 -78.2086 73.7 100 309 278 417 225 147 305 133.9 317.5 2.370518 -89.6031 91.8

1.249055 -65.1675

74 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Table no. 11 Boom 4591 –Test 3 Mohr Circle Calculations

Test: Sample of Boom Clay - 4591-test3 * = Data corrected by subtracting "Insert" value and applying formulas. North to P0 Tested in lateral stress oedometer.

Vertical nitial - Peak Stable Corrected Stable* Mohr Circle Calculations Stress P1 P0 P1 P2 P0 P1 P2 min max ratio 2 Theta Radius

Before Insert 1303357 0 0 00.0 0.0 0.0 100 150 56 100 18 20 38 13.1 37.9 2.898573 -54.1216 12.4 200 195 86 165 59 47 95 38.3 95.9 2.504952 -74.0938 28.8 400 349 182 296 200 132 210 131.9 229.6 1.740381 -67.3774 48.8 800 590 382 498 419 310 388 307.5 437.4 1.422761 -44.0693 65.0 1600 1135 912 995 916 781 826 761.3 920.1 1.208600 -19.1593 79.4 2000 1384 1180 1244 1143 1019 1045 993.3 1144.1 1.151813 -11.6339 75.4 2400 1655 1462 1501 1390 1269 1271 1230.4 1389.5 1.129359 -0.89147 79.6 1200 1200 1099 1170 975 947 980 946.5 987.8 1.043625 -67.8704 20.6 500 744 682 770 559 576 628 546.8 628.9 1.150087 -46.225 41.0 100 363 288 428 212 226 327 183.2 327.1 1.785628 -53.4738 72.0

1.330583 -28.6263

Table no. 11 Boom 348B –Test1 Mohr Circle Calculations

Test: Sample of Boom Clay - 348B Test 1 * = Data corrected by subtracting "Insert" value and applying formulas. North to P2 Tested in lateral stress oedometer.

Vertical Initial - Peak Stable Corrected Stable* Mohr Circle Calculations Stress P1 P0 P1 P2 P0 P1 P2 min max ratio 2 Theta Radius

Before Insert 0000.0 0.0 0.0 100 235 97 571 56 54 50 49.9 57.3 1.147671 38.71441 3.7 200 308 151 621 123 102 94 89.3 123.6 1.384997 15.45912 17.2 400 435 260 737 239 199 196 183.9 238.8 1.298441 3.153104 27.4 800 623 465 912 410 381 350 346.0 414.9 1.199041 30.87829 34.4 1600 1060 961 1378 808 821 761 759.8 833.7 1.097258 71.98673 36.9 2000 1287 1211 1631 1015 1044 983 979.2 1048.7 1.070969 88.24622 34.7 2400 1528 1477 1884 1235 1280 1206 1197.3 1283.0 1.071639 82.58888 42.9 1200 1153 1049 1517 893 900 883 882.2 901.5 1.021922 83.6034 9.7 500 750 616 1142 526 515 553 508.7 553.7 1.088401 -75.8578 22.5 100 441 261 822 244 200 271 196.8 280.0 1.422645 -81.9788 41.6

1.14747 55.37065

75 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Table no. 12 Boom 348B –Test2 Mohr Circle Calculations Test: Sample of Boom Clay - 348B Test 2 * = Data corrected by subtracting "Insert" value and applying formulas. North to P1 Tested in lateral stress oedometer.

Vertical Initial - Peak Stable Corrected Stable* Mohr Circle Calculations Stress P1 P0 P1 P2 P0 P1 P2 min max ratio 2 Theta Radius

Before Insert 0 0 0 0.0 0.0 0.0 100 220 141 104 63 28 51 27.2 67.7 2.48453 -40.2891 20.2 200 268 192 162 107 74 102 73.5 114.7 1.560109 -52.7792 20.6 400 358 269 258 189 142 187 142.1 202.8 1.427564 -57.8492 30.4 800 532 483 431 347 332 339 330.7 348.1 1.05246 -26.8607 8.7 1600 973 977 899 749 771 751 742.9 770.9 1.037651 55.33203 14.0 2000 1215 1228 1160 969 994 981 967.3 995.4 1.029044 32.4741 14.0 2400 1465 1488 1434 1197 1225 1222 1197.2 1232.1 1.02913 5.225323 17.4 1200 1154 1103 1073 914 883 904 881.9 918.6 1.041684 -42.1352 18.4 500 780 677 696 573 504 572 504.4 595.4 1.180375 -59.3548 45.5 100 405 279 374 231 151 289 143.8 303.6 2.111535 -84.4627 79.9

1.11517 1.664299

Table no. 13 Boom 348B –Test3 Mohr Circle Calculations

Test: Sample of Boom Clay - 348b-test3 * = Data corrected by subtracting "Insert" value and applying formulas. North to P2 Tested in lateral stress oedometer.

Vertical nitial - Peak Stable Corrected Stable* Mohr Circle Calculations Stress P1 P0 P1 P2 P0 P1 P2 min max ratio 2 Theta Radius

Before Insert 0000.0 0.0 0.0 100 195 106 125 27 33 41 25.7 42.0 1.635942 -37.0141 8.2 200 248 142 192 76 65 100 59.2 101.3 1.710084 -77.2372 21.0 400 380 272 299 196 180 195 180.3 200.2 1.110883 -55.5587 10.0 800 596 500 474 393 383 349 348.0 401.4 1.153466 47.58969 26.7 1600 1136 1082 958 885 900 775 774.2 931.8 1.203523 66.27118 78.8 2000 1398 1355 1212 1123 1142 998 997.7 1178.2 1.180975 66.84398 90.3 2400 1665 1628 1491 1367 1385 1244 1243.3 1420.1 1.142193 66.67779 88.4 1200 1244 1150 1124 983 960 921 918.3 991.0 1.079185 38.4731 36.4 500 781 676 726 561 539 570 538.3 575.6 1.069246 -76.5532 18.6 100 403 289 400 217 195 283 178.9 284.9 1.593080 -73.5181 53.0

1.170039 61.84566

76 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Table no. 14 Boom 348B –Test4 Mohr Circle Calculations

Test: Sample of Boom Clay - 348B-Test 4 * = Data corrected by subtracting "Insert" value and applying formulas. North to P0 Tested in lateral stress oedometer.

Vertical nitial - Peak Stable Corrected Stable* Mohr Circle Calculations Stress P1 P0 P1 P2 P0 P1 P2 min max ratio 2 Theta Radius

Before Insert 116 91 203 0 0 0 0.0 0.0 0.0 100 318 117 204 56 52 29 29.0 62.4 2.155504 53.69222 16.7 200 375 174 279 108 103 95 94.6 109.1 1.153751 39.08042 7.3 400 490 285 452 212 202 247 192.8 248.1 1.2869 -72.9112 27.7 800 730 505 741 431 397 502 381.5 505.0 1.323734 -78.5342 61.8 1600 1285 1009 1373 937 845 1058 822.8 1070.2 1.300734 -85.4527 123.7 2000 1555 1266 1677 1183 1073 1326 1047.3 1340.3 1.279747 -85.6583 146.5 2400 1847 1526 2008 1449 1304 1617 1275.4 1637.7 1.284086 -87.5265 181.2 1200 1415 1147 1523 1055 967 1190 941.1 1200.6 1.27578 -83.0456 129.8 500 915 675 962 600 548 696 527.6 701.6 1.329778 -80.0199 87.0 100 515 302 497 235 217 287 204.2 288.4 1.412418 -74.6025 42.1

1.29504 -82.0166

Appendix E: MOHR’S CIRLE:

120

70 P2 P1 P0 P1 P2 20

250 350 450 550 650 2 -30

-80

P0 -130

77 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

BM3369-Test 1(Loading)

450

350

250

150

-100-50 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600

-150

-250

-350

-450

BM3369-Test 1(Unloading)

300

200

100

0 0 100 200 300 400 500 600 700 800 900 1000

-100

-200

-300

78 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

BM3369-Test 2 (Loading)

650

450

250

50 -30 -20 -10 01020 30 40 50 60 70 80 90 10 11 12 13 14 15 16 17 18 19 20 21 22 23 0 0 -1050 0 0 0 0 0 0 0 0 0 00 00 00 00 00 00 00 00 00 00 00 00 00 00

-350

-550

-750

BM3369-Test 2 (Unloading)

650

450

250

50 01020 30 40 50 60 70 80 90 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 -150 0 0 0 0 0 0 0 0 0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

-350

-550

-750

79 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

BM1641A-Test 1(Loading)

570

370

170

-30 0 500 1000 1500 2000

-230

-430

-630

BM1641A-Test 1 (Unloading)

570

370

170

-30 0 500 1000 1500 2000

-230

-430

-630

80 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

BM1641A – Test 2 (Loading)

570

370

170

-30 0 500 1000 1500 2000

-230

-430

-630

BM1641A – Test 2 (Unloading)

570

370

170

-30 0 500 1000 1500 2000

-230

-430

-630

81 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

BM1641A- Test3 (Loading)

300

200

100

0 0 100 200 300 400 500 600 700 800 900 1000

-100

-200

-300

BM1641A –Test3 (Unloading)

250

200

150

100

0 0 100 200 300 400 500 600 700 800 -50

-100

-150

-200

-250

82 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

BM4591A-Test1 (Loading)

450

350

250

150

50 -50 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500

-150

-250

-350

-450

BM4591-Test1 (Unloading)

450

350

250

150

50 -50 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600

-150

-250

-350

-450

83 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

BM4591-Test 2 (Loading)

450

350

250

150

50 -50 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600

-150

-250

-350

-450

BM4591-Test2 (Unloading)

450

350

250

150

50 -50 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500

-150

-250

-350

-450

84 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

BM4591 –Test3 (Loading)

450

350

250

150

50 -50 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600

-150

-250

-350

-450

BM4591 –Test3 (Unloading)

350

250

150

50 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 -50

-150

-250

-350

85 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

BM348B – Test1 (Loading)

350

250

150

50 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 -50

-150

-250

-350

BM348B – Test 1 (Unloading)

250

200

150

100

0 0 100 200 300 400 500 600 700 800 900 -50

-100

-150

-200

-250

86 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

BM348B – Test 3 (Loading)

400

300

200

100

0 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400

-100

-200

-300

-400

BM348B-Test3 (Unloading)

300

200

100

0 0 100 200 300 400 500 600 700 800 900 1000

-100

-200

-300

87 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

BM 348B – Test 4 (Loading)

500

400

300

200

100

0 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 -100

-200

-300

-400

-500

BM348B- Test 4 (Unloading)

450

350

250

150

50 -50 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500

-150

-250

-350

-450

88 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Appendix F: LOG_TIME – SETTLEMENT CURVE

BM3369 – Test1LOADING

LogT_Settlement 100 KPa

Log-Time -1.8 -0.8 0.2 1.2 2.2 0.205 0.305

0.405

n 0.505 e m

e 0.605

t Series1 t 0.705 Se 0.805 0.905 2.124775737

LogT_Settlement 800 KPa

Log-Time -1.85 -0.85 0.15 1.15 2.15 2.3 2.4 2.5 2.6 t n 2.7 e m

e 2.8 Series1 ttl

e 2.9 S 3 3.1 1.82358292 3.2 3.3

UNLOADING

LogT_Settlement 100 Kpa-Unloading Log-Time -1.9 -0.9 0.1 1.1 2.1 3.75 3.8 3.85

t 3.9

en 3.95 em

l t 4

t Series1 e S 4.05 4.1 4.15 4.2

89 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

BM3369 – TEST2

LOADING:

LogT_Settlement 100 KPa

-1.5 -0.5 0.5 Log-Time 1.5 2.5 0.28

0.33

0.38

0.43 t

e 0.48 m e

t 0.53 Series1 t

Se 0.58

0.63 0.68 1.82358292 0.73

LogT_Settlement 200 KPa

Log-Time -1.5 -0.5 0.5 1.5 2.5 0.772

0.822

0.872 t 0.922 emen

l t

t Series1 e 0.972 S

1.022

1.072 1.82358292

90 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

UNLOADING:

LogT_Settlement 100 Kpa - unloading

-1.9 -0.9 0L.og-1 Time 1.1 2.1 3.1 2.2

2.3

2.4

en 2.5 em

t Series1 t e S 2.6

2.7

2.8

BM 1641A – TEST 1

LogT_Settlement 100 KPa

-1.5 -0.5 0.5 Log-Time 1.5 2.5 0.10000

0.15000

0.20000

t en 0.25000 em l

t Series1 t 0.30000 e S 0.35000

0.40000

0.45000

91 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

LogT_Settlement 100 KPa

Log-Time -1.5 -0.5 0.5 1.5 2.5

1.80000

2.00000

2.20000 t en 2.40000 em l t

t e S 2.60000

2.80000

3.00000

BM1641A – TEST 2

LogT_Settlement 100 KPa

Log-Time -1.5 -0.5 0.5 1.5 2.5 0.2

0.3

0.4 t n e

e 0.5 l

t Series1

Se 0.6

0.7

0.8

92 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

LogT_Settlement

500 Kpa-Unloading

Log-Time -1.5 -0.5 0.5 1.5 2.5 3.3

3.35

3.4

n e 3.45

m e

ttl 3.5 Series1 e S 3.55

3.6

3.65

BM1641A- TEST3

LogT_Settlement

100 KPa

Log-Time -1.5 -0.5 0.5 1.5 2.5 0.2

0.3

t 0.4

n e

e 0.5 l t

t Series1

Se 0.6

0.7 2.124938628 0.8

93 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

LogT_Settlement 100 Kpa-unloading

Log-Time -1.5 -0.5 0.5 1.5 2.5 1.4 1.5 1.6

t 1.7 n

e 1.8 m

e l

t 1.9 t

Se 2

2.1 2.2 2.3

BM4591 – TEST 1

LogT_Settlement 800 KPa

Log-Time -1.5 -0.5 0.5 1.5 2.5 1.7 1.8

1.9

n 2 e m e 2.1

ttl Series1

Se 2.2 2.124938628

2.3 2.4

94 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

BM348B – TEST1

LogT_Settlement 100 KPa

Log-Time -1.5 -0.5 0.5 1.5 2.5

0.10000

0.15000

0.20000 t

e 0.25000

m le

t Series1 t 0.30000

Se 0.35000

0.40000 2.124938628 0.45000

LogT_Settlement 100 KPa

Log-Time -1.5 -0.5 0.5 1.5 2.5 1.80000

2.00000

2.124938628 2.20000

t en 2.40000 em l

t Series1

t e

S 2.60000

2.80000

3.00000

95 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

BM348B – TEST2

LogT_Settlement 100 KPa Log-Time -1.5 -0.5 0.5 1.5 2.5 0.2

0.3

0.4 t

n e

e 0.5 l

Se 0.6

0.7

0.8

BM348B – TEST 3

LogT_Settlement 400 KPa

Log-Time -1.5 -0.5 0.5 1.5 2.5 1.25

1.35 1.45

en 1.55

em l t

t 1.65 e

S 1.75

1.85

1.95

96 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

LogT_Settlement 500 Kpa-unloading

Log-Time -1.5 -0.5 0.5 1.5 2.5 3.4

3.5

t 3.6

em l

t 3.7 t e

S 3.8

3.9 BM348B – TEST 4

LogT_Settlement 1600 KPa

Log-Time -1.5 -0.5 0.5 1.5 2.5 3.8

4.2

t n e

m 4.4 e l

t t

Se 4.6

4.8

97 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

LogT_Settlement 1200 Kpa-unloading

Log-Time -1.5 -0.5 0.5 1.5 2.5 5.45 5.5

5.55

5.6 t n e 5.65 m e l

t 5.7 t

Se 5.75

5.8

5.85

5.9

Appendix G: LATERAL STRESSES AT P0, P1 AND P2

Boom 1641A- loaded for 300KPa (left overnight with such load) North to P0

2000

1500

1000 channel 4 corr channel 5 corr channel 6 corr

Pressure (kPa) 500

0 0 100000 200000 300000 400000 500000 600000

-500 Time

98 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Boom 1641A-TEST2 North to P2

2000

1500

1000 Pa) k channel 4 corr channel 5 corr channel 6 corr

Pressure ( 500

0 0 100000 200000 300000 400000 500000 600000

-500 Time

Boom 1641A-Test 3 North to P0

1800

1300 ) a channel 4 corr

re (kP channel 5 corr 800 channel 6 corr essu r P

300

0 100000 200000 300000 400000 500000 600000 -200 Time

99 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Boom 4591A-Test1 North to P0

2000

1500

) 1000 a P

k channel 4 corr ( e channel 5 corr channel 6 corr essur r

P 500

0 0 100000 200000 300000 400000 500000 600000

-500 Time

Boom 4591-Test2 North to P0

2000

1500

) 1000 a P

k channel 4 corr ( e r channel 5 corr channel 6 corr essu r

P 500

0 0 100000 200000 300000 400000 500000 600000

-500 Time

100 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Boom 4591-Test 3 North to P0

2000

1500

) 1000 a channel 04

re (kP channel 05 channel 06 essu r

P 500

0 0 100000 200000 300000 400000 500000 600000

-500 Time

Boom 348B-Test 2 North to P1

2000

1500

) 1000 a P

k channel 04 ( e r channel 05 channel 06 essu r

P 500

0 0 100000 200000 300000 400000 500000 600000

-500 Time

101 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Boom 348B -Test 3 North to P2

1900

1400 ) a channel 04

re (kP channel 05 900 channel 06 essu r P

400

-100 0 100000 200000 300000 400000 500000 600000 Time

Boom 348B - TEST4 North to P0

2000

1500

) 1000 a channel 04

re (kP channel 05 channel 06 essu r

P 500

0 0 100000 200000 300000 400000 500000 600000

-500 Time

102 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Appendix H: PARTICLE DENSITY

BM3369 version Accu Pyc 1330 V2.01 serial no. 1053 report typeAnal ysis start 22/1 0/03 "10:17:48" stop 22/1 0/03 "10:30:07" temp. 25.272724deg. C sample ID 1111 weight 48.806999gram purges 3 equi. rate 0.1psig/min cell vol. 109.352966cc exp. vol. 115.612846cc average V 18.463623cc V dev 0.1048cc average d 2.643482kg/m3 d dev. 0.01507kg/m3 number runs 5 run precisi 0 % full scal 0,01

number pressure 1 pressureincludedtime (s volume V dev. density d dev. 1 19.5945668.633142 1 294 18,29710 -0,166530 2,667472 0,023990 2 19.6136098.634562 1 401 18,42830 -0,035320 2,648481 0,004998 3 19.6618758.651887 1 511 18,50189 0,038263 2,637947 -0,005540 4 19.6681278.652713 1 621 18,53797 0,074350 2,632812 -0,010670 5 19.6772738.655942 1 731 18,55285 0,089230 2,630701 -0,012780

BM1641A version AccuPyc 1330 V2.01 serial no. 1053 report type Analysis start 18-02-04 "15:32:57" stop 18-02-04 "15:45:26" temp. 26 deg. C sample ID 22121 weight 61 gram purges 3 equi. rate 0,1 psig/min cell vol. 109 cc exp. vol. 116 cc average V 23 cc V dev 0,241768 cc average d 3 kg/m3 d dev. 0,028519 kg/m3 number runs 5 run precision 0 % full scale 0,01 number pressure 1 pressure 2 included time (s) volume V dev. density d dev. 1 19,51833700 8,37531 1,00000 310,00000 22,45610 -0,38242 2,7183 0,045276 2 19,49848000 8,35022 1,00000 418,00000 22,75724 -0,08128 2,6824 0,009305 3 19,49350900 8,33908 1,00000 525,00000 22,92060 0,082077 2,6632 -0,00981 4 19,53271300 8,35129 1,00000 634,00000 23,00287 0,164352 2,6537 -0,01934 5 19,48975900 8,33000 1,00000 741,00000 23,05579 0,217268 2,6476 -0,02543

103 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

BM4591A

version AccuPyc 1330 V2.01 serial no. 1053 report type Analysis start 18/02/04 "15:02:48" stop 18/02/04 "15:15:46" temp. 25,74947 deg. C sample ID 1121 weight 44,947 gram purges 3 equi. rate 0,1 psig/min cell vol. 109,353 cc exp. vol. 115,6128 cc average V 16,6958 cc V dev 0,200345 cc average d 2,692427 kg/m3 d dev. 0,032614 kg/m3 number run 5 run precisio 0 % full scale 0,01

number pressure 1 pressure 2 included time (s) volume V dev. density d dev. 1 19,54495 8,712054 1 315 16,37455 -0,321255 2,744931 0,052504 2 19,53729 8,694847 1 430 16,63993 -0,055872 2,701153 0,008726 3 19,53243 8,686468 1 544 16,75934 0,063541 2,681907 -0,01052 4 19,52692 8,680337 1 659 16,83 0,134193 2,670648 -0,021779 5 19,49578 8,664142 1 770 16,87519 0,179388 2,663496 -0,028931

BM348B version AccuPyc 1330 V2.01 serial no. 1053 report type Analysis start 18-02-04 "16:58:27" stop 18-02-04 "17:11:20" temp. 26,176888 deg. C sample ID 2222 weight 47,386002 gram purges 3 equi. rate 0,1 psig/min cell vol. 109,352966 cc exp. vol. 115,612846 cc average V 17,720171 cc V dev 0,175629 cc average d 2,67434 kg/m3 d dev. 0,026718 kg/m3 number runs 5 run precision 0 % full scale 0,01 number pressure 1 pressure 2 included time (s) volume V dev. density d dev. 1 19,531429 8,650567 1 312 17,43776 -0,28241 2,717436 0,043097 2 19,493238 8,621536 1 424 17,66904 -0,05113 2,681866 0,007527 3 19,527439 8,630325 1 538 17,7896 0,069424 2,663692 -0,01065 4 19,527637 8,628466 1 651 17,82661 0,10644 2,658161 -0,01618 5 19,525774 8,624946 1 765 17,87785 0,157682 2,650542 -0,0238

104 DETERMINATION OF LATERAL STRESSES IN BOOM CLAY USING A LATERAL STRESS OEDOMETER

Appendix I: HYDROMETER TEST BM3369 BM3369 BM1641A grainsize (mm) passing % gr ainsize (mm) passing % grainsize (mm) passing % 2,00000 100,000 2,00000 100 2,00000 100

0,60000 100,000 0,60000 100,000 0,60000 100,000 0,30000 100,000 0,30000 100,000 0,30000 100,000 0,15000 99,821 0,15000 100,000 0,15000 100,000 0,06300 93,639 0,06300 93,364 0,06300 93,364 0,05683 71,594 0,05683 81,803 0,05441 87,423 0,04301 61,768 0,04301 70,875 0,04018 81,179 0,03229 51,941 0,03229 59,947 0,03003 72,436 0,02391 43,518 0,02391 50,580 0,02224 64,318 0,01733 38,745 0,01550 45,273 0,01612 59,635 0,01578 35,095 0,00911 41,214 0,00379 30,884 0,00409 36,530 0,00856 54,015 0,00318 29,480 0,00312 34,969 0,00421 51,517 0,00253 26,672 0,00253 31,847 0,00246 46,834 0,00138 44,024 0,00153 12,634 0,00153 16,236 0,00147 7,300 0,00146 10,303 0,00131 42,775 0,00108 1,965 0,00108 4,371 0,00112 40,901 0,00096 26,851 0,00087 8,118 BM4591A BM348B BM1641A grainsize (mm) passing % grainsize (mm) passing % grainsize (mm) passing % 2,00000 100,000 2,00000 100 2,00000 100,000 0,60000 100,000 0,60000 100,000 0,60000 100,000 0,30000 100,000 0,30000 100,000 0,30000 100,000 0,15000 100,000 0,15000 100,000 0,15000 100,000 0,06300 99,580 0,06300 99,719 0,06300 99,783 0,02533 83,196 0,02351 93,393 0,02864 74,355 0,01864 78,802 0,01741 88,874 0,02086 69,925 0,01351 75,873 0,01267 85,861 0,01362 64,863 0,00728 70,600 0,00661 79,234 0,00738 60,117 0,00374 65,327 0,00418 73,811 0,00459 57,269 0,00235 52,206 0,00210 60,347 0,00374 72,304 0,00119 54,781 0,00197 65,074 0,00128 47,460 0,00112 53,609 0,00115 59,350 0,00120 46,511 0,00108 52,730 0,00109 58,145 0,00115 45,878 0,00105 57,241

105