Principles of geotechnical engineering/ Braja M. Das

Contents
Geotechnical Engineering—A Historical Perspective 1
1.1 Geotechnical Engineering Prior to the 18^** Century 1
1.2 Pre-Ciassical Period of Soil Mechanics(1700-1776) 4
1.3 Classical Soil Mechanics—Phase I(1776-1856) 5
1.4 Classical Soil Mechanics—Phase II(1856-1910) 5
1.5 Modern Soil Mechanics 6
1.6 Geotechnical Engineering After 1927 6
References 11
Origin of Soil and Grain Size 13
2.1 Rock Cycle and the Origin ofSoil 13
2.2 Soil-Particle Size 20
2.3 Clay Minerals 21
2.4 Specific Gravity(G^) 28
2.5 Mechanical Analysis ofSoil 29
2.6 Particle-Size Distribution Curve 36
2.7 Particle Shape 40
2.8 Summary 42
Problems 42
References 44
Weight-Volume Relationships, Plasticity,
and Structure of Soil 45
3.1 Weight-Volume Relationships 45
3.2 Relationships Among Unit Weight,Void Ratio,Moisture Content,
and Specific Gravity 48
3.3 Relationships Among Unit Weight,Porosity,and Moisture Content 51vi Contents
3.4 Various Unit-Weight Relationships 53
3.5 Relative Density 58
3.6 Consistency ofSoil— Atterberg Limits 61
3.7 Liquid Limit(LL) 61
3.8 Plastic Limit(PL) 65
3.9 Shrinkage Limit(SL) 68
3.10 Liquidity Index and Consistency Index 70
3.11 Activity 71
3.12 Plasticity Chart 72
3.13 Soil Structure 73"
3.14 Summary 78
Problems 78
References 81
Engineering Classification of Soil 83
4.1 AASHTO Classification System 83
4.2 Unified Soil Classification System 87
4.3 Summary and Comparison Between the AASHTO
and Unified Systems 95
Problems 98
References 99
Soil Compaction 100
5.1 Compaction — General Principles ICQ
5.2 Standard Proctor Test 101
5.3 Factors Affecting Compaction 104
5.4 Modified Proctor Test 107
5.5 Structure of Compacted Clay Soil 110
5.6 Field Compaction 113
5.7 Specifications for Field Compaction 116
5.8 Determination ofField Unit Weight of Compaction 120
5.9 Compaction of Organic Soil and Waste Materials 125
5.10 Special Compaction Techniques 129
5.11 Summary and General Comments 135
Problems 135
References 137
Permeability 139
6.1 Bernoulli's Equation 139
6.2 Darcy's Law 141
6.3 Hydraulic Conductivity 143
6.4 Laboratory Determination of Hydraulic Conductivity 145
.6.5 EmpiricalRelationsforHydraulicConductivity 150Contents vii
6.6 Directional Variation ofPermeability 155
6.7 Equivalent Hydraulic Conductivity in Stratified Soil 157
6.8 Hydraulic Conductivity of Compacted Clayey Soils 160
6.9 Considerations for Hydraulic Conductivity of Clayey Soils
in Field Compaction 162
6.10 Moisture Content— Unit Weight Criteria for Clay Liner Construction 164
6.11 Permeability Test in the Field by Pumping from Wells 164
6.12 In Situ Hydraulic Conductivity of Compacted Clay Soils 168
6.13 Summary and General Comments .172
Problems 172
References 176
Seepage 178
7.1 Laplace's Equation of Continuity 178
7.2 Continuity Equation for Solution ofSimple Flow Problems 180
7.3 Flow Nets 183
7.4 Seepage Calculation from a Flow Net 185
7.5 Flow Nets in Anisotropic Soil 189
7.6 Mathematical Solution for Seepage 191
7.7 Uplift Pressure Under Hydraulic Structures 191
7.8 Seepage Through an Earth Dam on an Impervious Base 193
7.9 L.Casagrande's Solution for Seepage Through an Earth Dam 195
7.10 Summary 197
Problems 197
References 198
® In Situ Stresses 199
8.1 Stresses in Saturated Soil without Seepage 199
8.2 Stresses in Saturated Soil with Upward Seepage 204
8.3 Stresses in Saturated Soil with Downward Seepage 206
8.4 Seepage Force 208
8.5 Use of Filters to Increase the Factor ofSafety Against Heave 213
8.6 Selection ofFilter Material 214
8.7 Capillary Rise in Soils 215
8.8 Effective Stress in the Zone of Capillary Rise 218
8.9 Summary and General Comments 219
Problems 220
References 223
Stresses in a Soil Mass 224
9.1 Normal and Shear Stresses on a Plane 224
9.2 Stress Caused by a Point Load 229
9.3 Vertical Stress Caused by a Line Load 231viii Contents
9.4 Vertical Stress Caused by a Strip Load (Finite Width and
Infinite Length) 234
9.5 Vertical Stress Due to Embankment Loading 237
9.6 Vertical Stress Below the Center of a Uniformly Loaded
Circular Area 241
9.7 Vertical Stress at Any Point below a Uniformly Loaded Circular-Area 242
9.8 Vertical Stress Caused by a Rectangularly Loaded Area 242
9.9 Influence Chart for Vertical Pressure 251
9.10 Summary and General Comments 254
Problenis 254
References 258
to Compressibility of Soil 259
10.1 Contact Pressure and Settlement Profile 259
10.2 Relations for Immediate Settlement Calculation 261
10.3 Improved Relationship for Immediate Settlement 263
10.4 Fundamentals of Consolidation 268
10.5 One-Dimensional Laboratory Consolidation Test 271
10.6 Void Ratio-Pressure Plots 273-
10.7 Normally Consolidated and Overconsolidated Clays 274
10.8 Effect of disturbance on-Void Ratio-Pressure Relationship 277
10.9 Calculation of settlement from One-Dimensional
Primary Consolidation 280
10.10 Compression Index(CJ and Swell Index(C,) 281
10.11 Secondary Consolidation Settlement 285
10.12 Time Rate of Consolidation 287
10.13 Coefficient of Consolidation 292
10.14 Calculation of Consolidation Settlement Under a Foundation 300
10.15 Method of Accelerating Consolidation Settlement 302
10.16 Summary and General Comments 304
Problems 305
References 309
tt Shear Strength of Soil 311
11.1 Mohr-Coulomb Failure Criterion 311
11.2 Inclination of the Plane failure Caused by Shear 313
11.3 Laboratory Tests for Determination of Shear Strength Parameters 314
11.4 Direct Shear Test 315
11.5 Drained Direct Shear Test on Saturated Sand and Clay 318
11.6 General Comments on Direct Shear Test 320
11.7 Triaxial Shear Test— General 323
11.8 Consolidated-Drained Triaxial Test 324
11.9 Consolidated-Undrained Triaxial Test 332
.11.10 Unconsolidated-Undrained TriaxialTest 337Contents ix
11.11 Unconfined Compression Test on Saturated Clay 339
11.12 Stress Path 340
11.13 Vane Shear Test 346
11.14 Other Methods for Determining Undrained Shear Strength 350
11.15 Sensitivity and Thixotropy of Clay 350
11.16 Empirical Relationships Between Undrained Cohesion(c„)and Effective
Overburden Pressure {cr'o) 354
11.17 Shear Strength of Unsaturated Cohesive Soils 356
11.18 Summary and General Comments 357
Problems 358
References 363
Lateral Earth Pressure: At-Rest,Rankine,and Coulomb 364
12.1 At-Rest,Active,and Passive Pressures 364
12.2 Earth Pressure at Rest 366
12.3 Earth Pressure at Rest for Partially Submerged Soil 368
12.4 Lateral Pressure on Retaining Walls from Surcharges—
Based on Theory of Elasticity 371
12.5 Rankine's Theory of Active Pressure 374
12.6 Theory of Rankine's Passive Pressure 377
12.7 Yielding of Wall of Limited Height 378
12.8 Diagrams for Lateral Earth Pressure Distribution Against
Retaining Walls 380
12.9 Rankine Active and Passive Pressure with Sloping Backfill 392
12.10 Coulomb's Active Pressure 396
12.11 Graphic Solution for Coulomb's Active Earth Pressure 398
12.12 Active Force on Retaining Walls with Earthquake Forces 402
12.13 Pae for Soil Backfill 407
12.14 Coulomb's Passive Pressure 411
12.15 Passive Force on Retaining Walls with Earthquake Forces 413
12.16 Summary and General Comments 414
Problems 415
References 419
Lateral Earth Fressure—Curved Failure Surface 420
13.1 Retaining Walls with Friction 420
13.2 Properties of a Logarithmic Spiral 422
13.3 Procedure for Determination ofPassive Earth Pressure,
(Cohesionless Backfill) 424
13.4 Coefficient ofPassive Earth Pressure,Kp 426
13.5 Passive Force on Walls with Earthquake Forces 428
13.6 Braced Cuts— General 430
13.7 Determination of Active Thrust on Bracing Systems ofOpen Cuts
in Granular Soil 434
contents
13.8 Determination of Active Thrust on Bracing Systems for Cuts
in Cohesive Soil 437
13.9 Pressure Variation for Design of Sheetings,Struts,and Wales 438
13.10 Dynamic Earth Pressure Distribution Behind a Wall Rotating
About the Top 441
13.11 Summary 442
Problems 442
References 444
Slope Stability 445
14.1 Factor of Safety 447
14.2 Stability ofInfinite Slopes 448
14.3 Finite Slopes — General 453
14.4 Analysis of Finite Slopes with Plane Failure Surfaces
(Culmann's Method) 454
14.5 Analysis of Finite Slopes with Circular Failure Surfaces — General 457
14.6 Mass Procedure — Slopes in Homogeneous Clay Soil with <^ =0 458
14.7 Mass Procedure for Stability of saturated Clay Slopes {<}> =0condition)
with Earthquake Forces 463
14.8 Mass Procedure — Slopes in Homogeneous Soil 466
14.9 Ordinary Method ofSlices 472
14.10-Bishop's Simplified Method ofSlices 476
14.11 Stability Analysis by Method of Slices for Steady State Seepage 477
14.12 Morgenstern's Method ofSlicesfor Rapid Drawdown Condition 485
14.13 Cousin's Charts 488
14.14 Fluctuation factor of safety ofSlopes in Clay Embankment
on Saturated Clay 492
14.15 Summary and General Comments 495
Problems 497
References 502
15 Soil-Bearing Capacity for Shallow Foundations 503
15.1 Ultimate Soil-Bearing Capacity for Shallow Foundations 504
15.2 Terzaghi's Ultimate Bearing Capacity Equation 506
15.3 General Bearing Capacity Equation 512
ISA Effect of ground Water Table 516
15.5 Factor of Safety 517
15.6 Ultimate Load for Shallow Foundations Under Eccentric Load 523
15.7 Bearing Capacity ofSand Based on Settlement 526
15.8 Plate Load Test 528
15.9 Ultimate Bearing Capacity on Layered Soil 530
15.10 Summary and General Comments 538
Problems 538
• References 542Contents xi
Landfill Liners and Geosynthetics 544
16.1 Landfill Liners — Overview 544
16.2 Geosynthetics 545
16.3 Geotextiles . 545
16.4 Geomembranes 548
16.5 Geonets 550
16.6 Single Clay Liner and Single Geomembrane Liner Systems 551
16.7 Recent Advances in the Liner Systems for Landfills 552
16.8 Leachate Removal Systems 553
16.9 Closure of Landfills 555
16.10 Summary and General Comments 556
References 557
^7 Subsoil Exploration 558
17.1 Planning for Soil Exploration 558
17.2 Boring Methods 560
17.3 Common Sampling Methods 563
17.4 Sample Disturbance 566
17.5 Correlations for Standard Penetration Test 566
17.6 OtherIn Situ Tests 570
17.7 Rock Coring 573
17.8- Soil Exploration Report 575
Problems 577