Consolidation and Other Geotechnical Properties of Shales with Respect to Age and Composition
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Durham E-Theses Consolidation and other geotechnical properties of shales with respect to age and composition Smith, Trevor, J. How to cite: Smith, Trevor, J. (1978) Consolidation and other geotechnical properties of shales with respect to age and composition, Durham theses, Durham University. Available at Durham E-Theses Online: http://etheses.dur.ac.uk/8520/ Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in Durham E-Theses • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders. Please consult the full Durham E-Theses policy for further details. Academic Support Oce, Durham University, University Oce, Old Elvet, Durham DH1 3HP e-mail: [email protected] Tel: +44 0191 334 6107 http://etheses.dur.ac.uk 2 CONSOLIIATION AND OTHER GEOTECHNICAL PROPERTIES OF SHALES mm RESPECT TO AGE AND COMPOSITION by Trevor J. Smith, B.Sc. being a thesis presented in fulfilment of requirements for the degree of Doctor of Philosophy at the Department of Geological Sciences in Faculty of Science of the University of Durham. The copyright of this thesis rests with the author. No quotation from it should be published without his prior written consent and information derived from it should be acknowledged. k'OV1978 ) L/BRARl. ABSTRACT Studies of a wide selection of overconsolidated, weak . argillaceous rocks from major formations in the United Kingdom and North America have shown that the compaction history, coupled with the mineralogical composition have a decisive bearing on the natxire of the material, both at depth and in the near surface zone. Current evidence indicates that maximum depths of burial of North American sediments are generally much greater than their British counterparts, infeaing that overburden does not increase systematically with age. Furthermore major differences have also been observed in the mineralogy and geochemistry of these two groups. In particular,, recalculated smectite formulae i-ndicate the onset of the montmorillonite to illite transformation in the former sediments. Preferred orientation studies and electron microscopy have been used to "(iljtucidate the clay microstrxicture, whereas exchangeable cations and pore water chemistry indicate possible interactions between clay, minerals. Consolidation studies to a pressure of 35000kN/ra on both tindisturbed and remoTilded materials have led to a new interpretation of the stress-stredn response, and in addition these tests have indicated the presence of diagenetic bonding in unweathered materieils the strength of which is dependent upon the maximum depth of b\irial and minercil species present. Furthermore, since slaking and suction experinents frequently only detect this bonding in the Carboniferous materials, it has been inferred that mineral-mineral welding is present in these and that cationic bonding predominates in younger sediments, Consecfuently to avoid unfo^een engineering complications in the field caused by the subsequent destruction of the latter bond type by weathering agents it has been suggested that a combination of suction and consolidation tests should be performed on the shales in question. LIST OF CONTENTS Page No. Chapter 1 - Introduction 1.1 GenereiL Aims of the Investigation 1 1.2 Types of Consolidated Clays and Shales 2 1.3 Definition and Nomenclature of Shales 2 1.4 Classification of Shales 5 1.4.1 Geological Classification 5 1.4.2 Engineering Classification 7 1.5 Compaction Studies • 10 1.5.1 Models for Natural Compaction 10 1.5.2 Compaction Models based upon Mineralogical and Geochemical Transformations 15 1.5.3 Laboratory Compaction Studies 18 1.5.3.1 Laboratory Studies of Natural Materials 19 1.5.4. I'licrostructure of Clays and Shales 27 1.5.5 The Development of Preferred Orientation 29 1.5.6 Bond Formation in Shales and the Strain Energy Concept 31 1.6 Soil Water Phenomena • 39 1.6.1 The Movement and Distribution of Water in Soils in Relation to Soil Suction 39 1.6.2 The Variation of Soil Suction in Compacted Sedimentary Rocks 43 1.6,3 The Relationship between SiACtion and the Mineralogy of Artificially Prepared Soils 51 1.6.4 Determination of the Specific Surface Area 52 1.7 Slaking Behaviour 53 1.7.1 Slaking Mechanisms • 53 1.7.2 Slaking Behaviour of Pure Clays • 54 1.7.3 Slaking Behaviour of Natural Clays and Shales 66 Chapter 2 - Geological Nature and Characteristics of Samples Studied 2.1 General Information 72 2.2 Stratigraphy and Lithology • 72 2.2.1 British Materials 72 2.2.1.1 Carboniferous Deposits 72 2.2.1.2 Triassic Deposits 76 2. 2.1.3 Jxarassic Deposits 76 2.2.1.4 Cretaceous Deposits 78 2.2.1.5 Tertiary Deposits 78 2.2.2 . North American Materials 79 2.2.2.1 Cretaceous Deposits - Western Interior 79 2.2.2.2 Tertiary Deposits - Eastern Rockies 80 2.2.2.3 Tertiary Deposits - Mississippi Embayment 85 2.3 Estimation of the Maximum Overburden Thicknesses of Strata 85 2.3.1 Summation of Thicknesses from the Literature 88 2.3.2 Casagrande ConstrtK:tion 88 2.3.3 Rebound Characteristics using Undisturbed Samples 91 2.4 Assessment of the Accuracy of Estimated Maximum Depths of Burial 94 2.4.1 British Materials 94 2.4.2 North American Materials 97 2.5 Concl\isions • 99 Chapter 3 - Mineralogy and Geochemistry Page No. 3.1 Mineralogy • 104 3.1.1 Clay Minerals 109 3.1.1.1 Illite and Mixed-layer Clay 109 3.1.1.2 Kaolinite 113 3.1.1.3 Smectite 117 3.1.1.4 Chlorite 124 - 3.1.1.5 VermicTolite 125 3.1.2 Relative Abundances of Clay Minerals 125 3.1.2.1 British Materials 127 3.1.2.2 North American Shales 130 3.1.3 Other Detrital Minerals 131 3.1.3.1 Quartz 131 3.1.3.2 Feldspar • r 132 3.1.4 Non Detrital Minerals 133 3.1.4.1 Carbonates 133 3.1.4.2 Pyrite 135 3.1.5 Carbonaceous Material .••......•.......•......«•....•. 135 3.1.6 Mineral Relationships 136 3.2. Geochemistry • 139 3.2.1 Method of Analysis 139 3.2.2 . Geochemical Relationships .k.. 140 3.3. Cation Exchange Capacity 148 3.3.1 Method of Analysis 148 3.3.2 Exchangeable Cation Relationships 148 3.3.3 Water-Soli;ible Cations 153 3.4 The Effect of Age and Depth of Burial upon the Mineralogy and Geochemistry 156 3.5 The Relationship between Mineralogy, Atterberg Limits and Clay-sized Fraction 158 3.6 Conclusions Chapter 4 - Clay Microstrtcture and Preferred Orientation 4.1 Introduction 166 4.2 Preferred Orientation Studies 166 4.2.1 Method of Analysis 166 4.2.1.1 An Optical Method for the Determination of Preferred Orientation 168 4.2.1.2 X-ray Diffraction Methods for the Determination of Preferred Orientation , 173 4.2.2 The Relationship of Preferred Orientation to Mineralogy and Depth of Burial 176 178 4.3 Clay Microstructure 178 4. 3.1 Method of Analysis 4.3.2 Microstructure of the Samples Studied 179 4.4 The Relationship between Microstructure and 181 Preferred Orientation • Chapter 5 - Consolidation 5.1 195 5.2 Introduction ••• 195 5.3 The One-Dimensional Theory of Consolidation A Review of Research into the Validity of the 196 200 5.4 Terzaghi Theory • Concept of Effective Stress 5.5 Consolidation Tests - Methods of Analysis 201 5.5*1 Apparatus • •• 201 5. 5. 2 Experimental Procedures 202 5.6 Comparison of the Performance of the High Pressure Cell with a Standard Oedometer 202 5.6.1 Voids Ratio - Presstire Relationships 202 5.6.2 Stress-strain Response ,. 203 5*6.3 Consolidation Parameters ., 207 5.7 Experiments with a Teflon Oedometer Cell .*.•••.*•*••.*. 207 5.8 Voids Ratio Correction for the Remotilded Consolidation Curve ....* 208 5.9 Consolidation Test Results 209 5.9.1 Voids Ratio - Presstire Relationships 209 5.9.2 Coefficient of Consolidation (c^) 226 5*9*3 Compression Index (C ) 230 5.9.4 Swell Index (C ) 235 5*9.5 Permeability (I) 240 '5.9.6 Coefficient of Volume Compressibility (m ) 243 5.9,7 Swell Pressure 248 5.10 An Investigation into the Presence of Diagenetic Bonding • 251 5.11 Strain Energy-and Stress-strain Relationships 256 5.12 Conclusions 282 Chapter 6 - Soil Suction Characteristics 6.1 Introduction 285 6.2 The Relationship between Suction and Effective Presstire 285 6.3 Experimental Methods for the Determination of the Relationship between Suction and Moisture Content 286 6.4 The Relationship of Sx^ction to the Mineralogy and Present State of Overconsolidated Shales 287 6.5 Surface Area Determinations 300 6.6 Conclusions • • 306 Chapter 7 - Slaking Behaviotar of Overconsolidated Shales 7.1 Introduction 307 7.2 Slaking Tests 307 7.2.1 A Review of Previous Testing Procedures 307 7.2.2 Present Test Procedures 309 7.3 Rate and Amount of Breakdown in Water 310 7.4 Uptake of Water upon Immersion 326 7.5 Slaking under Vacuum 332 7.6 The Relationship between Exchangeable Cations, Water- Soluble Cations and the Possibility of Erosion 332 7.7 Conclusions 338 Chapter 8 - Summary and General Conclusions • 339 References 360 Appendix A.l Mineralogy and Geochemistry 377 A.2 Microstructtire and Preferred Orientation 399 A. 3 Consolidation 403 A.4 Soil Suction 442 A. 5 Slaking Tests 450 LIST OF FIGURES FigTire No.