Unsaturated Soil Mechanics

Table of Contents......Page 0
Front Matter......Page 2
Foreword......Page 5
Preface......Page 7
Symbols......Page 9
Table of Contents......Page 16
1.1.1 Definition of Unsaturated Soil Mechanics......Page 25
1.1.2 Interdisciplinary Nature of Unsaturated Soil Mechanics......Page 26
1.1.3 Classification of Unsaturated Soil Phenomena......Page 28
1.2.1 Chapter Structure......Page 30
1.2.2 Geomechanics and Geo-Environmental Tracks......Page 33
1.3.2 Global Extent of Climatic Factors......Page 34
1.3.3 Unsaturated Zone and Soil Formation......Page 35
1.3.4 Unsaturated Soil in Engineering Practice......Page 40
1.4.1 Stress in the Unsaturated State......Page 42
1.4.2 Saturated Moisture and Stress Profiles: Conceptual Illustration......Page 43
1.4.3 Unsaturated Moisture and Stress Profiles: Conceptual Illustration......Page 44
1.4.4 Illustrative Stress Analysis......Page 45
1.5.1 Phenomena Prediction......Page 48
1.5.2 Head as a State Variable......Page 50
1.5.3 Effective Stress as a State Variable......Page 52
1.5.4 Net Normal Stresses as State Variables......Page 55
1.6.1 Total Soil Suction......Page 56
1.6.2 Pore Water Potential......Page 57
1.6.3 Units of Soil Suction......Page 60
1.6.4 Suction Regimes and the Soil-Water Characteristic Curve......Page 61
Problems......Page 65
2.1.1 Unsaturated Soil as a Multiphase System......Page 68
2.1.2 Density of Dry Air......Page 69
2.1.3 Density of Water......Page 71
2.1.4 Viscosity of Air and Water......Page 74
2.1.5 Flow Regimes......Page 76
2.2.2 Composition and Partial Pressure of Air......Page 78
2.2.3 Equilibrium between Free Water and Air......Page 80
2.2.4 Equilibrium between Pore Water and Air......Page 83
2.2.5 Relative Humidity......Page 84
2.2.6 Dew Point......Page 85
2.3.1 Effect of Water Vapor on Density of Air......Page 86
2.3.2 Formulation for Moist Air Density......Page 87
2.4.1 Origin of Surface Tension......Page 94
2.4.2 Pressure Drop across an Air-Water Interface......Page 97
2.5.1 Cavitation and Boiling......Page 101
2.5.2 Hydrostatic Atmospheric Pressure......Page 103
2.5.3 Cavitation Pressure......Page 105
Problems......Page 107
3.1.1 Henry\'s Law......Page 110
3.1.2 Temperature Dependence......Page 112
3.1.3 Volumetric Coefficient of Solubility......Page 113
3.1.4 Henry\'s Law Constant and Volumetric Coefficient of Solubility......Page 114
3.1.5 Vapor Component Correction......Page 115
3.1.6 Mass Coefficient of Solubility......Page 116
3.2.1 Equilibrium between Two Water Drops......Page 117
3.2.2 Equilibrium at an Air-Water-Solid Interface......Page 118
3.2.3 Contact Angle......Page 120
3.2.4 Air-Water-Solid Interface in Unsaturated Soil......Page 122
3.3.1 Implications of Kelvin\'s Equation......Page 125
3.3.2 Derivation of Kelvin\'s Equation......Page 127
3.3.3 Capillary Condensation......Page 132
3.4.1 Soil Suction and Soil Water......Page 135
3.4.2 Capillary Tube Model......Page 136
3.4.3 Contacting Sphere Model......Page 139
Problems......Page 145
4.1.1 Three-Dimensional Meniscus......Page 149
4.1.2 Hydrostatic Equilibrium in a Capillary Tube......Page 152
4.2.1 Capillary Rise in a Tube......Page 154
4.2.2 Capillary Finger Model......Page 157
4.2.3 Capillary Rise in Idealized Soil......Page 158
4.2.4 Capillary Rise in Soil......Page 160
4.3.1 Saturated Hydraulic Conductivity Formulation......Page 161
4.3.2 Unsaturated Hydraulic Conductivity Formulation......Page 163
4.3.3 Experimental Verification......Page 166
4.4.1 Theoretical Basis......Page 168
4.4.2 Pore Geometry......Page 171
4.4.3 Computational Procedures......Page 174
4.5.1 Forces between Two Spherical Particles......Page 181
4.5.2 Pressure in the Water Lens......Page 183
4.5.3 Effective Stress Due to Capillarity......Page 184
4.5.4 Effective Stress Parameter and Water Content......Page 186
Problems......Page 189
5.1.1 Macromechanical Conceptualization......Page 192
5.1.2 Micromechanical Conceptualization......Page 193
5.1.3 Stress between Two Spherical Particles with Nonzero Contact Angle......Page 194
5.1.4 Pore Pressure Regimes......Page 200
5.2.1 Hysteresis Mechanisms......Page 201
5.2.2 Ink-Bottle Hysteresis......Page 203
5.2.3 Contact Angle Hysteresis......Page 205
5.2.5 Hysteresis in the Effective Stress Parameter......Page 206
5.3.1 Net Normal Stress, Matric Suction, and Suction Stress Tensors......Page 210
5.3.2 Stress Tensors in Unsaturated Soil: Conceptual Illustration......Page 214
5.4.1 Rationale for Axis Translation......Page 220
5.4.2 Equilibrium for an Air-Water-HAE System......Page 221
5.4.3 Equilibrium for an Air-Water-HAE-Soil System......Page 222
5.4.5 Controlled Stress Variable Testing......Page 223
5.5.1 Net Normal Stress and Matric Suction Representation......Page 226
5.5.2 Effective Stress Representation......Page 232
Problems......Page 237
6.1.1 M-C for Saturated Soil......Page 239
6.1.2 Experimental Observations of Unsaturated Shear Strength......Page 240
6.1.3 Extended M-C Criterion......Page 248
6.1.4 Extended M-C Criterion in Terms of Principal Stresses......Page 251
6.2.1 Interpretation of Triaxial Testing Results......Page 252
6.2.2 Interpretation of Direct Shear Testing Results......Page 255
6.3.1 Nonlinearity in the Extended M-C Envelope......Page 257
6.3.2 Effective Stress Approach......Page 260
6.3.3 Measurements of chi at Failure......Page 261
6.3.4 Reconciliation between Phi^b and chi_f......Page 263
6.3.5 Validity of Effective Stress as a State Variable for Strength......Page 266
6.4.1 Interpretation of Direct Shear Testing Results......Page 267
6.4.2 Interpretation of Triaxial Testing Results......Page 269
6.5.1 Capillary Cohesion as a Characteristic Function for Unsaturated Soil......Page 271
6.5.2 Determining the Magnitude of Capillary Cohesion......Page 275
6.5.3 Concluding Remarks......Page 280
Problems......Page 284
7.1.1 Suction Regimes in Unsaturated Soil......Page 286
7.1.2 Analytical Solutions for Profiles of Matric Suction......Page 289
7.1.3 Hydrologic Parameters for Representative Soil Types......Page 291
7.1.4 Profiles of Matric Suction for Representative Soil Types......Page 292
7.1.5 Profiles of Water Content for Representative Soil Types......Page 294
7.2.1 Profiles of the Effective Stress Parameter chi......Page 299
7.2.2 Profiles of Suction Stress and Their Solution Regimes......Page 301
7.2.3 Profiles of Suction Stress for Representative Soil Types......Page 308
7.2.4 Concluding Remarks......Page 311
7.3.1 Extended Hooke\'s Law......Page 313
7.3.2 Profiles of Coefficient of Earth Pressure at Rest......Page 315
7.3.3 Depth of Cracking......Page 316
7.4.1 Mohr-Coulomb Failure Criteria for Unsaturated Soil......Page 320
7.4.2 Rankine\'s Active State of Failure......Page 321
7.4.3 Active Earth Pressure Profiles for Constant Suction Stress......Page 325
7.4.4 Active Earth Pressure Profiles for Variable Suction Stress......Page 327
7.4.5 Active Earth Pressure Profiles with Tension Cracks......Page 329
7.5.1 Rankine\'s Passive State of Failure......Page 331
7.5.2 Passive Earth Pressure Profiles for Constant Suction Stress......Page 334
7.5.3 Passive Earth Pressure Profiles for Variable Suction Stress......Page 337
7.5.4 Concluding Remarks......Page 339
Problems......Page 341
8.1.1 Potential for Water Flow......Page 343
8.1.3 Regimes for Pore Water Flow and Pore Airflow......Page 344
8.1.4 Steady-State Flow Law for Water......Page 346
8.2.1 Permeability versus Conductivity......Page 347
8.2.2 Magnitude, Variability, and Scaling Effects......Page 349
8.3.1 Conceptual Model for the Hydraulic Conductivity Function......Page 351
8.3.3 Relative Conductivity......Page 354
8.3.4 Effects of Soil Type......Page 356
8.4.1 Natural and Engineered Capillary Barriers......Page 359
8.4.2 Flat Capillary Barriers......Page 360
8.4.3 Dipping Capillary Barriers......Page 363
8.5.1 Horizontal Infiltration......Page 367
8.5.2 Vertical Infiltration and Evaporation......Page 370
8.6.2 Temperature and Vapor Pressure Variation......Page 377
8.6.3 Vapor Density Gradient......Page 379
8.7.1 Theoretical Basis......Page 381
8.7.2 Air Diffusion in an Axis Translation System......Page 384
Problems......Page 385
9.1.1 Principle of Mass Conservation......Page 387
9.1.2 Transient Saturated Flow......Page 389
9.1.3 Transient Unsaturated Flow......Page 390
9.2.1 Transient Horizontal Infiltration......Page 394
9.2.2 Transient Vertical Infiltration......Page 398
9.2.3 Transient Moisture Profile for Vertical Infiltration......Page 402
9.3.2 Analytical Solution of Transient Unsaturated Flow......Page 404
9.3.3 Numerical Modeling of Transient Unsaturated Flow......Page 407
9.4.1 Principle of Mass Conservation for Compressible Gas......Page 414
9.4.2 Governing Equation for Pore Airflow......Page 415
9.4.3 Linearization of the Airflow Equation......Page 416
9.4.4 Sinusoidal Barometric Pressure Fluctuation......Page 418
9.5.1 Barometric Pumping......Page 420
9.5.2 Theoretical Framework......Page 421
9.5.3 Time Series Analysis......Page 422
9.5.4 Determining Air Permeability......Page 425
Problems......Page 430
10.1 Overview of Measurement Techniques......Page 433
10.2.1 Properties of High-Air-Entry Materials......Page 436
10.2.2 Tensiometer Measurement Principles......Page 437
10.3.1 Null Tests and Pore Water Extraction Tests......Page 440
10.3.2 Pressure Plates......Page 441
10.3.3 Tempe Pressure Cells......Page 443
10.4 Electrical/Thermal Conductivity Sensors......Page 445
10.5.1 Total Suction and Relative Humidity......Page 447
10.5.2 Thermocouple Psychrometers......Page 448
10.5.3 Chilled-Mirror Hygrometers......Page 454
10.5.4 Polymer Resistance/Capacitance Sensors......Page 457
10.6 Humidity Control Techniques......Page 459
10.6.1 Isopiestic Humidity Control......Page 460
10.6.2 Two-Pressure Humidity Control......Page 461
10.7.1 Filter Paper Measurement Principles......Page 465
10.7.2 Calibration and Testing Procedures......Page 467
10.7.3 Accuracy, Precision, and Performance......Page 468
Problems......Page 475
11.1 Overview of Measurement Techniques......Page 478
11.2.1 Constant-Head Method......Page 479
11.2.2 Constant-Flow Method......Page 482
11.2.3 Centrifuge Method......Page 488
11.3.1 Hydraulic Diffusivity......Page 492
11.3.2 Horizontal Infiltration Method......Page 493
11.3.3 Outflow Methods......Page 496
11.3.4 Instantaneous Profile Methods......Page 500
Problems......Page 509
12.1 Soil-Water Characteristic Curve Models......Page 510
12.1.1 SWCC Modeling Parameters......Page 511
12.1.2 Brooks and Corey (BC) Model......Page 513
12.1.3 van Genuchten (VG) Model......Page 515
12.1.4 Fredlund and Xing (FX) Model......Page 521
12.2 Hydraulic Conductivity Models......Page 522
12.2.1 Empirical and Macroscopic Models......Page 525
12.2.2 Statistical Models......Page 532
Problems......Page 543
References......Page 546
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