Soil Mechanics Fundamentals

An accessible, clear, concise, and contemporary course in geotechnical engineering, this key text: strikes a balance between theory and practical applications for an introductory course in soil mechanics keeps mechanics to a minimum for the students to appreciate the background, assumptions and limitations of the theories discusses implications of the key ideas to provide students with an understanding of the context for their application gives a modern explanation of soil behaviour is presented particularly in soil settlement and soil strength offers substantial on-line resources to support teaching and learning

Table of Contents:
About the Author xi Other Books by this Author xiii Preface xv Acknowledgments xix Notes for Students and Instructors xxi Notation, Abbreviations, Unit Notation, and Conversion Factors xxv 1 Composition and Particle Sizes of Soils 1 1.1 Introduction 1 1.2 Definitions of Key Terms 1 1.3 Composition of Soils 2 1.3.1 Soil formation 2 1.3.2 Soil types 2 1.3.3 Soil minerals 3 1.3.4 Surface forces and adsorbed water 5 1.3.5 Soil fabric 6 1.4 Determination of Particle Size 7 1.4.1 Particle size of coarse-grained soils 7 1.4.2 Particle size of fine-grained soils 9 1.5 Characterization of Soils Based on Particle Size 10 1.6 Comparison of Coarse-Grained and Fine-Grained Soils for Engineering Use 19 1.7 Summary 20 Exercises 20 2 Phase Relationships, Physical Soil States, and Soil Classification 23 2.1 Introduction 23 2.2 Definitions of Key Terms 23 2.3 Phase Relationships 24 2.4 Physical States and Index Parameters of Fine-Grained Soils 36 2.5 Determination of the Liquid, Plastic, and Shrinkage Limits 40 2.5.1 Casagrande’s cup method 40 2.5.2 Plastic limit test 41 2.5.3 Fall Cone Method to Determine Liquid and Plastic Limits 42 2.5.4 Shrinkage limit 43 2.6 Soil Classification Schemes 47 2.6.1 The Unified Soil Classification System (USCS) 47 2.6.2 Plasticity chart 48 2.7 Engineering Use Chart 50 2.8 Summary 53 2.8.1 Practical examples 53 Exercises 56 3 Soils Investigation 61 3.1 Introduction 61 3.2 Definitions of Key Terms 62 3.3 Purposes of a Soils Investigation 62 3.4 Phases of a Soils Investigation 63 3.5 Soils Exploration Program 64 3.5.1 Soils exploration methods 65 3.5.1.1 Geophysical methods 65 3.5.1.2 Destructive methods 69 3.5.2 Soil identification in the field 70 3.5.3 Number and depths of boreholes 73 3.5.4 Soil sampling 74 3.5.5 Groundwater conditions 76 3.5.6 Types of in situ or field tests 77 3.5.6.1 Vane shear test (VST) 78 3.5.6.2 Standard penetration test (SPT) 79 3.5.6.3 Cone penetrometer test (CPT) 85 3.5.6.4 Pressuremeter 88 3.5.6.5 Flat plate dilatometer (DMT) 88 3.5.7 Soils laboratory tests 90 3.5.8 Types of laboratory tests 90 3.6 Soils Report 91 3.7 Summary 93 Exercises 94 4 One- and Two-Dimensional Flows of Water Through Soils 97 4.1 Introduction 97 4.2 Definitions of Key Terms 97 4.3 One-Dimensional Flow of Water Through Saturated Soils 98 4.4 Flow of Water Through Unsaturated Soils 101 4.5 Empirical Relationship for kz 101 4.6 Flow Parallel to Soil Layers 103 4.7 Flow Normal to Soil Layers 104 4.8 Equivalent Hydraulic Conductivity 104 4.9 Laboratory Determination of Hydraulic Conductivity 106 4.9.1 Constant-head test 106 4.9.2 Falling-head test 107 4.10 Two-Dimensional Flow of Water Through Soils 110 4.11 Flownet Sketching 112 4.11.1 Criteria for sketching flownets 113 4.11.2 Flownet for isotropic soils 114 4.12 Interpretation of Flownet 114 4.12.1 Flow rate 114 4.12.2 Hydraulic gradient 115 4.12.3 Critical hydraulic gradient 115 4.12.4 Porewater pressure distribution 116 4.12.5 Uplift forces 116 4.13 Summary 117 4.13.1 Practical examples 117 Exercises 121 5 Soil Compaction 125 5.1 Introduction 125 5.2 Definition of Key Terms 125 5.3 Benefits of Soil Compaction 126 5.4 Theoretical Maximum Dry Unit Weight 126 5.5 Proctor Compaction Test 126 5.6 Interpretation of Proctor Test Results 129 5.7 Field Compaction 135 5.8 Compaction Quality Control 137 5.8.1 Sand cone 137 5.8.2 Balloon test 139 5.8.3 Nuclear density meter 140 5.8.4 Comparisons among the three popular compaction quality control tests 140 5.9 Summary 141 5.9.1 Practical example 141 Exercises 143 6 Stresses from Surface Loads and the Principle of Effective Stress 147 6.1 Introduction 147 6.2 Definition of Key Terms 147 6.3 Vertical Stress Increase in Soils from Surface Loads 148 6.3.1 Regular shaped surface loads on a semi-infinite half-space 148 6.3.2 How to use the charts 153 6.3.3 Infinite loads 154 6.3.4 Vertical stress below arbitrarily shaped areas 155 6.4 Total and Effective Stresses 164 6.4.1 The principle of effective stress 164 6.4.2 Total and effective stresses due to geostatic stress fields 165 6.4.3 Effects of capillarity 166 6.4.4 Effects of seepage 167 6.5 Lateral Earth Pressure at Rest 175 6.6 Field Monitoring of Soil Stresses 176 6.7 Summary 177 6.7.1 Practical example 177 Exercises 179 7 Soil Settlement 185 7.1 Introduction 185 7.2 Definitions of Key Terms 185 7.3 Basic Concept 186 7.4 Settlement of Free-Draining Coarse-Grained Soils 189 7.5 Settlement of Non–Free-Draining Soils 190 7.6 The One-Dimensional Consolidation Test 191 7.6.1 Drainage path 193 7.6.2 Instantaneous load 193 7.6.3 Consolidation under a constant load: primary consolidation 194 7.6.4 Effective stress changes 194 7.6.5 Effects of loading history 196 7.6.6 Effects of soil unit weight or soil density 196 7.6.7 Determination of void ratio at the end of a loading step 198 7.6.8 Determination of compression and recompression indexes 198 7.6.9 Determination of the modulus of volume change 199 7.6.10 Determination of the coefficient of consolidation 200 7.6.10.1 Root time method (square root time method) 201 7.6.10.2 Log time method 202 7.6.11 Determination of the past maximum vertical effective stress 203 7.6.11.1 Casagrande’s method 203 7.6.11.2 Brazilian method 204 7.6.11.3 Strain energy method 204 7.6.12 Determination of the secondary compression index 206 7.7 Relationship between Laboratory and Field Consolidation 214 7.8 Calculation of Primary Consolidation Settlement 216 7.8.1 Effects of unloading/reloading of a soil sample taken from the field 216 7.8.2 Primary consolidation settlement of normally consolidated fine-grained soils 217 7.8.3 Primary consolidation settlement of overconsolidated fine-grained soils 217 7.8.4 Procedure to calculate primary consolidation settlement 218 7.9 Secondary Compression 219 7.10 Settlement of Thick Soil Layers 219 7.11 One-Dimensional Consolidation Theory 222 7.12 Typical Values of Consolidation Settlement Parameters and Empirical Relationships 224 7.13 Monitoring Soil Settlement 225 7.14 Summary 226 7.14.1 Practical example 226 Exercises 230 8 Soil Strength 237 8.1 Introduction 237 8.2 Definitions of Key Terms 237 8.3 Basic Concept 238 8.4 Typical Response of Soils to Shearing Forces 238 8.4.1 Effects of increasing the normal effective stress 240 8.4.2 Effects of overconsolidation ratio, relative density, and unit weight ratio 241 8.4.3 Effects of drainage of excess porewater pressure 243 8.4.4 Effects of cohesion 244 8.4.5 Effects of soil tension and saturation 245 8.4.6 Effects of cementation 246 8.5 Three Models for Interpreting the Shear Strength of Soils 247 8.5.1 Coulomb’s failure criterion 248 8.5.2 Mohr–Coulomb failure criterion 249 8.5.2.1 Saturated or clean, dry uncemented soils at critical state 250 8.5.2.2 Saturated or clean, dry uncemented soils at peak state 250 8.5.2.3 Unsaturated, cemented, cohesive soils 250 8.5.3 Tresca’s failure criterion 252 8.6 Factors Affecting the Shear Strength Parameters 254 8.7 Laboratory Tests to Determine Shear Strength Parameters 256 8.7.1 A simple test to determine the critical state friction angle of clean coarse-grained soils 256 8.7.2 Shear box or direct shear test 256 8.7.3 Conventional triaxial apparatus 266 8.7.4 Direct simple shear 276 8.8 Specifying Laboratory Strength Tests 277 8.9 Estimating Soil Parameters from in Situ (Field) Tests 278 8.9.1 Vane shear test (VST) 278 8.9.2 Standard penetration test (SPT) 279 8.9.3 Cone penetrometer test (CPT) 280 8.10 Some Empirical and Theoretical Relationships for Shear Strength Parameters 281 8.11 Summary 282 8.11.1 Practical examples 282 Exercises 287 Appendix A: Derivation of the One-Dimensional Consolidation Theory 291 Appendix B: Mohr’s Circle for Finding Stress States 295 Appendix C: Frequently Used Tables of Soil Parameters and Correlations 296 Appendix D: Collection of Equations 307 References 319 Index 323

About the Author :
MUNIRAM (MUNI) BUDHU is Professor of Civil Engineering & Engineering Mechanics at the University of Arizona, Tucson, Arizona. He received his BSc (First Class Honors) in Civil Engineering from the University of the West Indies and his PhD in Soil Mechanics from Cambridge University, England. Prior to joining the University of Arizona, Dr. Budhu served on the faculty at the University of Guyana; McMaster University, Canada and the State University of New York at Buffalo. He spent sabbaticals as visiting Professor at St. Catherine's College, Oxford University; Eidgenössische Technische Hochschule Zürich(Swiss Federal Institute of Technology, Zurich), and theUniversity of Western Australia.