Soil Mechanics Fundamentals

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.

• About the Author xiOther Books by this Author xiiiPreface xvAcknowledgments xixNotes for Students and Instructors xxiNotation, Abbreviations, Unit Notation, and Conversion Factors xxv1 Composition and Particle Sizes of Soils 11.1 Introduction 11.2 Definitions of Key Terms 11.3 Composition of Soils 21.3.1 Soil formation 21.3.2 Soil types 21.3.3 Soil minerals 31.3.4 Surface forces and adsorbed water 51.3.5 Soil fabric 61.4 Determination of Particle Size 71.4.1 Particle size of coarse-grained soils 71.4.2 Particle size of fine-grained soils 91.5 Characterization of Soils Based on Particle Size 101.6 Comparison of Coarse-Grained and Fine-Grained Soils for Engineering Use 191.7 Summary 20Exercises 202 Phase Relationships, Physical Soil States, and Soil Classification 232.1 Introduction 232.2 Definitions of Key Terms 232.3 Phase Relationships 242.4 Physical States and Index Parameters of Fine-Grained Soils 362.5 Determination of the Liquid, Plastic, and Shrinkage Limits 402.5.1 Casagrande’s cup method 402.5.2 Plastic limit test 412.5.3 Fall Cone Method to Determine Liquid and Plastic Limits 422.5.4 Shrinkage limit 432.6 Soil Classification Schemes 472.6.1 The Unified Soil Classification System (USCS) 472.6.2 Plasticity chart 482.7 Engineering Use Chart 502.8 Summary 532.8.1 Practical examples 53Exercises 563 Soils Investigation 613.1 Introduction 613.2 Definitions of Key Terms 623.3 Purposes of a Soils Investigation 623.4 Phases of a Soils Investigation 633.5 Soils Exploration Program 643.5.1 Soils exploration methods 653.5.1.1 Geophysical methods 653.5.1.2 Destructive methods 693.5.2 Soil identification in the field 703.5.3 Number and depths of boreholes 733.5.4 Soil sampling 743.5.5 Groundwater conditions 763.5.6 Types of in situ or field tests 773.5.6.1 Vane shear test (VST) 783.5.6.2 Standard penetration test (SPT) 793.5.6.3 Cone penetrometer test (CPT) 853.5.6.4 Pressuremeter 883.5.6.5 Flat plate dilatometer (DMT) 883.5.7 Soils laboratory tests 903.5.8 Types of laboratory tests 903.6 Soils Report 913.7 Summary 93Exercises 944 One- and Two-Dimensional Flows of Water Through Soils 974.1 Introduction 974.2 Definitions of Key Terms 974.3 One-Dimensional Flow of Water Through Saturated Soils 984.4 Flow of Water Through Unsaturated Soils 1014.5 Empirical Relationship for kz 1014.6 Flow Parallel to Soil Layers 1034.7 Flow Normal to Soil Layers 1044.8 Equivalent Hydraulic Conductivity 1044.9 Laboratory Determination of Hydraulic Conductivity 1064.9.1 Constant-head test 1064.9.2 Falling-head test 1074.10 Two-Dimensional Flow of Water Through Soils 1104.11 Flownet Sketching 1124.11.1 Criteria for sketching flownets 1134.11.2 Flownet for isotropic soils 1144.12 Interpretation of Flownet 1144.12.1 Flow rate 1144.12.2 Hydraulic gradient 1154.12.3 Critical hydraulic gradient 1154.12.4 Porewater pressure distribution 1164.12.5 Uplift forces 1164.13 Summary 1174.13.1 Practical examples 117Exercises 1215 Soil Compaction 1255.1 Introduction 1255.2 Definition of Key Terms 1255.3 Benefits of Soil Compaction 1265.4 Theoretical Maximum Dry Unit Weight 1265.5 Proctor Compaction Test 1265.6 Interpretation of Proctor Test Results 1295.7 Field Compaction 1355.8 Compaction Quality Control 1375.8.1 Sand cone 1375.8.2 Balloon test 1395.8.3 Nuclear density meter 1405.8.4 Comparisons among the three popular compaction quality control tests 1405.9 Summary 1415.9.1 Practical example 141Exercises 1436 Stresses from Surface Loads and the Principle of Effective Stress 1476.1 Introduction 1476.2 Definition of Key Terms 1476.3 Vertical Stress Increase in Soils from Surface Loads 1486.3.1 Regular shaped surface loads on a semi-infinite half-space 1486.3.2 How to use the charts 1536.3.3 Infinite loads 1546.3.4 Vertical stress below arbitrarily shaped areas 1556.4 Total and Effective Stresses 1646.4.1 The principle of effective stress 1646.4.2 Total and effective stresses due to geostatic stress fields 1656.4.3 Effects of capillarity 1666.4.4 Effects of seepage 1676.5 Lateral Earth Pressure at Rest 1756.6 Field Monitoring of Soil Stresses 1766.7 Summary 1776.7.1 Practical example 177Exercises 1797 Soil Settlement 1857.1 Introduction 1857.2 Definitions of Key Terms 1857.3 Basic Concept 1867.4 Settlement of Free-Draining Coarse-Grained Soils 1897.5 Settlement of Non–Free-Draining Soils 1907.6 The One-Dimensional Consolidation Test 1917.6.1 Drainage path 1937.6.2 Instantaneous load 1937.6.3 Consolidation under a constant load: primary consolidation 1947.6.4 Effective stress changes 1947.6.5 Effects of loading history 1967.6.6 Effects of soil unit weight or soil density 1967.6.7 Determination of void ratio at the end of a loading step 1987.6.8 Determination of compression and recompression indexes 1987.6.9 Determination of the modulus of volume change 1997.6.10 Determination of the coefficient of consolidation 2007.6.10.1 Root time method (square root time method) 2017.6.10.2 Log time method 2027.6.11 Determination of the past maximum vertical effective stress 2037.6.11.1 Casagrande’s method 2037.6.11.2 Brazilian method 2047.6.11.3 Strain energy method 2047.6.12 Determination of the secondary compression index 2067.7 Relationship between Laboratory and Field Consolidation 2147.8 Calculation of Primary Consolidation Settlement 2167.8.1 Effects of unloading/reloading of a soil sample taken from the field 2167.8.2 Primary consolidation settlement of normally consolidated fine-grained soils 2177.8.3 Primary consolidation settlement of overconsolidated fine-grained soils 2177.8.4 Procedure to calculate primary consolidation settlement 2187.9 Secondary Compression 2197.10 Settlement of Thick Soil Layers 2197.11 One-Dimensional Consolidation Theory 2227.12 Typical Values of Consolidation Settlement Parameters and Empirical Relationships 2247.13 Monitoring Soil Settlement 2257.14 Summary 2267.14.1 Practical example 226Exercises 2308 Soil Strength 2378.1 Introduction 2378.2 Definitions of Key Terms 2378.3 Basic Concept 2388.4 Typical Response of Soils to Shearing Forces 2388.4.1 Effects of increasing the normal effective stress 2408.4.2 Effects of overconsolidation ratio, relative density, and unit weight ratio 2418.4.3 Effects of drainage of excess porewater pressure 2438.4.4 Effects of cohesion 2448.4.5 Effects of soil tension and saturation 2458.4.6 Effects of cementation 2468.5 Three Models for Interpreting the Shear Strength of Soils 2478.5.1 Coulomb’s failure criterion 2488.5.2 Mohr–Coulomb failure criterion 2498.5.2.1 Saturated or clean, dry uncemented soils at critical state 2508.5.2.2 Saturated or clean, dry uncemented soils at peak state 2508.5.2.3 Unsaturated, cemented, cohesive soils 2508.5.3 Tresca’s failure criterion 2528.6 Factors Affecting the Shear Strength Parameters 2548.7 Laboratory Tests to Determine Shear Strength Parameters 2568.7.1 A simple test to determine the critical state friction angle of clean coarse-grained soils 2568.7.2 Shear box or direct shear test 2568.7.3 Conventional triaxial apparatus 2668.7.4 Direct simple shear 2768.8 Specifying Laboratory Strength Tests 2778.9 Estimating Soil Parameters from in Situ (Field) Tests 2788.9.1 Vane shear test (VST) 2788.9.2 Standard penetration test (SPT) 2798.9.3 Cone penetrometer test (CPT) 2808.10 Some Empirical and Theoretical Relationships for Shear Strength Parameters 2818.11 Summary 2828.11.1 Practical examples 282Exercises 287Appendix A: Derivation of the One-Dimensional Consolidation Theory 291Appendix B: Mohr’s Circle for Finding Stress States 295Appendix C: Frequently Used Tables of Soil Parameters and Correlations 296Appendix D: Collection of Equations 307References 319Index 323