CONTENTS
1.2 Origin, composition and structure of soils and rocks 4
1.2.1 Rock 5
1.2.2 Weathered rock and residual soil 5
1.2.3 Sedimentary weak rock and soil 6
1.2.4 Pedogenic soil 6
1.2.5 Variability 7
1.3 Soil strength and effective stress 7
1.4 Dilatancy and the critical state 12
1.5 Strength on preexisting failure planes 13
1.6 Soil stiffness and ground movements 13
1.7 Consolidation and swelling— ‘short- term’ and ‘long-term’ conditions 16
1.8 Consequences for engineering design 21
1.9 Structured soils 21
2.1.1 Rigid-plastic soil models 26
2.1.2 Winkler spring models 28
2.1.3 Elastic models 29
2.1.4 Plasticity and failure 31
2.2 Site investigation and acquisition of soil parameters 32
2.2.1 Key parameters 33
2.2.2 Methods of investigation 34
2.2.3 Desk studies and walk-over surveys 36
2.2.4 Depths and spacing of boreholes or probe holes 37
2.2.5 In situ testing 40
2.2.6 Sampling and laboratory testing 43
2.2.7 Groundwater conditions 48
2.3 Obtaining required soil parameters from site investigation data 49
2.3.1 Bulk unit weight 50
2.3.2 Peak effective strength parameters, c΄ and ϕ΄ 502.3.3 Effective wall friction and adhesion 54
2.3.4 Critical state and CamClay parameters 57
2.3.5 Residual effective strength parameters 58
2.3.6 Undrained shear strength, cu 59
3 Factors affecting earth pressure 633.1 Wall construction 63
3.1.1 Types of wall and their support 65
3.1.2 Construction of gravity walls 68
3.1.3 Construction of embedded walls 68
3.1.4 Construction of composite/hybrid walls 69
3.2 Wall and ground movements 71
3.2.1 Causes of wall and ground movements 71
3.2.2 Rigid body movements 72
3.2.3 Wall flexibility 73
3.2.4 Associated ground movements 75
3.3 Earth pressure principles 75
3.3.1 Components of earth pressure 76
3.3.2 Earth pressure at rest 77
3.3.3 Active and passive states 79
3.3.4 Earth pressure coefficients 81
3.3.5 Wall movements required for active and passive conditions 88
3.3.6 Strain softening and progressive failure 89
3.3.7 Influence of type of wall movement on earth pressure 92
3.3.8 Effect of wall flexibility on bending moments applied to embedded walls 94
3.3.9 Stress relief during in situ embedded wall construction 99
3.3.10 Pressure increases due to external loads 104
3.3.11 Compaction pressures—granular backfill 107
3.3.12 Compaction pressures—cohesive backfill 117
3.3.13 Swelling of backfill 119
3.3.14 Shrinkage and thermal effects in propped walls and integral abutments 124
4 Water and retaining structures 1314.1 Typical ground water conditions 131
4.1.1 Definition of water table 132
4.1.2 Hydrostatic groundwater 133
4.1.3 Artesian groundwater 133
4.1.4 Perched groundwater 134
4.1.5 Underdrainage 135
4.1.6 Rising groundwater 135
4.1.7 Conditions above the groundwater table 136
4.1.8 Groundwater and soil attack on structural components 138
4.1.9 Groundwater contamination 138
4.2 Seepage and water pressure calculations 138
4.2.1 Wall loading from water 142
4.2.2 Tidal lag effects 148
4.3 Water-induced instability 149
4.3.1 Reduction in passive resistance 150
4.3.2 Hydraulic uplift (base heave) 151
4.3.3 Piping 152
4.3.4 Hydraulic fracture 157
4.3.5 Internal erosion 157
4.4 Groundwater control 159
4.4.1 Wall drainage 160
4.4.2 Soil dewatering 161
5 Global and local instability 163
5.1 Types of instability affecting retaining structures 163
5.2 Classification of instability and selection of parameters 166
5.2.1 Short-term or long-term parameters? 167
5.2.2 Peak, residual or critical state parameters? 168
5.3 Base heave and local failure calculations 169
5.4 Limit equilibrium analysis of overall instability 170
5.4.1 The method of slices 170
5.4.2 Methods of limit equilibrium slope stability analysis 172
5.4.3 Computer analysis of slope stability 173
5.4.4 Hand calculations and design charts 174
5.5 Detecting and stabilising preexisting instability 182
5.6 Stabilisation of slopes using retaining structures 183
2.1.4 Plasticity and failure 31
2.2 Site investigation and acquisition of soil parameters 32
2.2.1 Key parameters 33
2.2.2 Methods of investigation 34
2.2.3 Desk studies and walk-over surveys 36
2.2.4 Depths and spacing of boreholes or probe holes 37
2.2.5 In situ testing 40
2.2.6 Sampling and laboratory testing 43
2.2.7 Groundwater conditions 48
2.3 Obtaining required soil parameters from site investigation data 49
2.3.1 Bulk unit weight 50
2.3.2 Peak effective strength parameters, c΄ and ϕ΄ 502.3.3 Effective wall friction and adhesion 54
2.3.4 Critical state and CamClay parameters 57
2.3.5 Residual effective strength parameters 58
2.3.6 Undrained shear strength, cu 59
2.3.7 Soil stiffness 60
3.1.1 Types of wall and their support 65
3.1.2 Construction of gravity walls 68
3.1.3 Construction of embedded walls 68
3.1.4 Construction of composite/hybrid walls 69
3.2 Wall and ground movements 71
3.2.1 Causes of wall and ground movements 71
3.2.2 Rigid body movements 72
3.2.3 Wall flexibility 73
3.2.4 Associated ground movements 75
3.3 Earth pressure principles 75
3.3.1 Components of earth pressure 76
3.3.2 Earth pressure at rest 77
3.3.3 Active and passive states 79
3.3.4 Earth pressure coefficients 81
3.3.5 Wall movements required for active and passive conditions 88
3.3.6 Strain softening and progressive failure 89
3.3.7 Influence of type of wall movement on earth pressure 92
3.3.8 Effect of wall flexibility on bending moments applied to embedded walls 94
3.3.9 Stress relief during in situ embedded wall construction 99
3.3.10 Pressure increases due to external loads 104
3.3.11 Compaction pressures—granular backfill 107
3.3.12 Compaction pressures—cohesive backfill 117
3.3.13 Swelling of backfill 119
3.3.14 Shrinkage and thermal effects in propped walls and integral abutments 124
3.4 Summary 130
4.1.1 Definition of water table 132
4.1.2 Hydrostatic groundwater 133
4.1.3 Artesian groundwater 133
4.1.4 Perched groundwater 134
4.1.5 Underdrainage 135
4.1.6 Rising groundwater 135
4.1.7 Conditions above the groundwater table 136
4.1.8 Groundwater and soil attack on structural components 138
4.1.9 Groundwater contamination 138
4.2 Seepage and water pressure calculations 138
4.2.1 Wall loading from water 142
4.2.2 Tidal lag effects 148
4.3 Water-induced instability 149
4.3.1 Reduction in passive resistance 150
4.3.2 Hydraulic uplift (base heave) 151
4.3.3 Piping 152
4.3.4 Hydraulic fracture 157
4.3.5 Internal erosion 157
4.4 Groundwater control 159
4.4.1 Wall drainage 160
4.4.2 Soil dewatering 161
5 Global and local instability 163
5.2 Classification of instability and selection of parameters 166
5.2.1 Short-term or long-term parameters? 167
5.2.2 Peak, residual or critical state parameters? 168
5.3 Base heave and local failure calculations 169
5.4 Limit equilibrium analysis of overall instability 170
5.4.1 The method of slices 170
5.4.2 Methods of limit equilibrium slope stability analysis 172
5.4.3 Computer analysis of slope stability 173
5.4.4 Hand calculations and design charts 174
5.5 Detecting and stabilising preexisting instability 182
5.6 Stabilisation of slopes using retaining structures 183
Part II
Design 187
6 Wall selection 1896.1 Reasons for selecting a particular form of retaining wall 189
6.2 Gravity walls 191
6.2.1 Mass concrete gravity walls 191
6.2.2 Gabions 191
6.2.3 Crib walling 193
6.2.4 Interlocking block walls 193
6.2.5 Masonry walls 194
6.2.6 ‘Semi-gravity’ concrete walls 196
6.2.7 Reinforced concrete cantilever walls 197
6.2.8 Counterfort walls 198
6.2.9 Buttressed walls 199
6.3 Embedded walls 199
6.3.1 Trenching systems 200
6.3.2 Sheet-pile walls 200
6.3.2.1 Steel 203
6.3.2.2 Wood 205
6.3.2.3 Concrete 205
6.3.3 Bored pile walls 207
6.3.4 Diaphragm walls 208
6.3.5 King post (‘soldier pile’ or ‘Berlin’) walls 212
6.3.6 Jet-grouted walls 213
6.4 Composite walls and other support systems 214
6.4.1 Cofferdams 216
6.4.2 Reinforced soil (MSE) structures 216
6.4.3 Anchored earth 220
6.4.4 Support using ground anchors 221
6.4.5 Soil nailing 222
6.5 Preliminary selection of wall type 224
6.2 Gravity walls 191
6.2.1 Mass concrete gravity walls 191
6.2.2 Gabions 191
6.2.3 Crib walling 193
6.2.4 Interlocking block walls 193
6.2.5 Masonry walls 194
6.2.6 ‘Semi-gravity’ concrete walls 196
6.2.7 Reinforced concrete cantilever walls 197
6.2.8 Counterfort walls 198
6.2.9 Buttressed walls 199
6.3 Embedded walls 199
6.3.1 Trenching systems 200
6.3.2 Sheet-pile walls 200
6.3.2.1 Steel 203
6.3.2.2 Wood 205
6.3.2.3 Concrete 205
6.3.3 Bored pile walls 207
6.3.4 Diaphragm walls 208
6.3.5 King post (‘soldier pile’ or ‘Berlin’) walls 212
6.3.6 Jet-grouted walls 213
6.4 Composite walls and other support systems 214
6.4.1 Cofferdams 216
6.4.2 Reinforced soil (MSE) structures 216
6.4.3 Anchored earth 220
6.4.4 Support using ground anchors 221
6.4.5 Soil nailing 222
6.5 Preliminary selection of wall type 224
7 Avoiding failure 2277.1 Defining failure 227
7.2 Uncertainties in design 231
7.2.1 Uncertainties in the ground model 232
7.2.2 Calculation uncertainties 236
7.2.3 Parameter uncertainties 237
7.3 Providing for uncertainty—introducing safety and reliability 240
7.3.1 Lumped ‘factors of safety’ 241
7.3.2 Partial factors of safety 249
7.3.3 Geotechnical limit state design using partial factors 250
7.3.3.1 Actions, effects of actions and resistances 250
7.3.3.2 Design approaches 252
7.3.3.3 Material properties 254
7.3.3.4 Geometric input 254
7.3.3.5 Design calculations to EC7 255
7.4 Summary of practice 1951–2011 255
7.2 Uncertainties in design 231
7.2.1 Uncertainties in the ground model 232
7.2.2 Calculation uncertainties 236
7.2.3 Parameter uncertainties 237
7.3 Providing for uncertainty—introducing safety and reliability 240
7.3.1 Lumped ‘factors of safety’ 241
7.3.2 Partial factors of safety 249
7.3.3 Geotechnical limit state design using partial factors 250
7.3.3.1 Actions, effects of actions and resistances 250
7.3.3.2 Design approaches 252
7.3.3.3 Material properties 254
7.3.3.4 Geometric input 254
7.3.3.5 Design calculations to EC7 255
7.4 Summary of practice 1951–2011 255
8 Introduction to analysis 2578.1 Rules of thumb 257
8.2 Evidential methods 259
8.2.1 Envelopes for prop loads 259
8.2.2 Displacement correlations 262
8.2.3 Moment reduction factors for sheet-pile walls 264
8.3 Closed-form solutions 264
8.3.1 Solutions based on elasticity theory 265
8.3.1.1 Excavation heave 266
8.3.1.2 Wall bending 267
8.3.2 Solutions based on plasticity theory 269
8.3.2.1 Active and passive stress states (Rankine) 270
8.4 Limit analysis 271
8.4.1 Upper bound solutions 271
8.4.2 Lower bound solutions 272
8.4.3 Refinement 273
8.5 Limit equilibrium analyses 274
8.5.1 Free earth support method 275
8.5.2 Fixed earth support method 276
8.6 Discrete spring models 277
8.6.1 Winkler spring model 278
8.6.2 Intelligent spring models 280
8.6.3 Discretization 281
8.6.4 Procedure 281
8.6.5 Solution 282
8.7 Continuum models 282
8.7.1 Available methods 283
8.7.1.1 Finite element method 283
8.7.1.2 Finite difference method 284
8.7.1.3 Boundary element method 285
8.7.2 Geometric representation 286
8.7.2.1 Discretization 286
8.7.2.2 Boundary conditions 287
8.7.2.3 Types of element 287
8.7.3 Constitutive models 288
8.7.3.1 Linear elasticity 288
8.7.3.2 Non-homogeneity 289
8.7.3.3 Anisotropy 289
8.7.3.4 Non-linearity 289
8.7.3.5 Plasticity 289
8.7.4 Water and effective stress 290
8.7.5 Construction modelling 290
8.7.5.1 Wall installation 291
8.7.5.2 Excavation 291
8.7.5.3 Support system 291
8.2 Evidential methods 259
8.2.1 Envelopes for prop loads 259
8.2.2 Displacement correlations 262
8.2.3 Moment reduction factors for sheet-pile walls 264
8.3 Closed-form solutions 264
8.3.1 Solutions based on elasticity theory 265
8.3.1.1 Excavation heave 266
8.3.1.2 Wall bending 267
8.3.2 Solutions based on plasticity theory 269
8.3.2.1 Active and passive stress states (Rankine) 270
8.4 Limit analysis 271
8.4.1 Upper bound solutions 271
8.4.2 Lower bound solutions 272
8.4.3 Refinement 273
8.5 Limit equilibrium analyses 274
8.5.1 Free earth support method 275
8.5.2 Fixed earth support method 276
8.6 Discrete spring models 277
8.6.1 Winkler spring model 278
8.6.2 Intelligent spring models 280
8.6.3 Discretization 281
8.6.4 Procedure 281
8.6.5 Solution 282
8.7 Continuum models 282
8.7.1 Available methods 283
8.7.1.1 Finite element method 283
8.7.1.2 Finite difference method 284
8.7.1.3 Boundary element method 285
8.7.2 Geometric representation 286
8.7.2.1 Discretization 286
8.7.2.2 Boundary conditions 287
8.7.2.3 Types of element 287
8.7.3 Constitutive models 288
8.7.3.1 Linear elasticity 288
8.7.3.2 Non-homogeneity 289
8.7.3.3 Anisotropy 289
8.7.3.4 Non-linearity 289
8.7.3.5 Plasticity 289
8.7.4 Water and effective stress 290
8.7.5 Construction modelling 290
8.7.5.1 Wall installation 291
8.7.5.2 Excavation 291
8.7.5.3 Support system 291
9 Gravity walls 2939.1 Preliminary design 293
9.1.1 Drainage and water control 294
9.1.2 Initial sizing of gravity walls 295
9.1.3 Design charts 296
9.2 Detailed design—limit states for external stability 300
9.2.1 Calculation models 301
9.2.2 Wall geometry and its effect on earth pressures 303
9.2.3 Earth pressures from undisturbed ground 306
9.2.4 Calculation of compaction pressures 307
9.2.5 Sliding—horizontal equilibrium 309
9.2.6 Overturning and toppling 315
9.2.7 Bearing capacity 318
9.2.8 Overall stability 323
9.2.9 Settlement and tilt 325
9.3 Internal stability 325
9.3.1 Masonry, gravity block and gabion walls 326
9.3.2 Crib walls 328
9.3.3 Reinforced concrete cantilever walls 330
9.4 Calculations to Eurocode 7 for a gravity wall 331
9.4.1 Partial factors 332
9.4.2 Overturning or toppling 333
9.4.3 Sliding 334
9.4.4 Bearing capacity 334
9.1.1 Drainage and water control 294
9.1.2 Initial sizing of gravity walls 295
9.1.3 Design charts 296
9.2 Detailed design—limit states for external stability 300
9.2.1 Calculation models 301
9.2.2 Wall geometry and its effect on earth pressures 303
9.2.3 Earth pressures from undisturbed ground 306
9.2.4 Calculation of compaction pressures 307
9.2.5 Sliding—horizontal equilibrium 309
9.2.6 Overturning and toppling 315
9.2.7 Bearing capacity 318
9.2.8 Overall stability 323
9.2.9 Settlement and tilt 325
9.3 Internal stability 325
9.3.1 Masonry, gravity block and gabion walls 326
9.3.2 Crib walls 328
9.3.3 Reinforced concrete cantilever walls 330
9.4 Calculations to Eurocode 7 for a gravity wall 331
9.4.1 Partial factors 332
9.4.2 Overturning or toppling 333
9.4.3 Sliding 334
9.4.4 Bearing capacity 334
10 Embedded walls 34510.1 Selection of soil parameters 345
10.1.1 In situ soil parameters 345
10.1.2 Wall friction 346
10.1.3 Wall adhesion 347
10.2 Preliminary design 347
10.2.1 Drainage and control of water 347
10.2.2 Design charts for waterfront structures 348
10.2.2.1 Cantilever sheet-pile walls 348
10.2.2.2 Singly anchored sheet-pile walls 354
10.2.3 Sheet-pile drivability 355
10.3 Design of sheet-pile walls using limit equilibrium calculations 356
10.3.1 Limit states and definitions of factor of safety 357
10.3.2 Effect of groundwater 357
10.3.3 Cantilever sheet-pile walls 359
10.3.4 Singly-anchored sheet-pile walls 365
10.3.4.1 Free-earth support method 366
10.3.4.2 Fixed-earth support method 370
10.3.5 Design of anchor systems 378
10.4 Propped and braced excavations 383
10.4.1 Calculation of prop loads 383
10.4.2 Base stability 388
10.4.3 Ground movements 392
10.4.4 Overall instability 394
10.5 Bored pile and diaphragm walls 396
10.5.1 Analysis for embedment, bending moments and prop loads 397
10.5.2 Wall deflections and ground movements 398
10.5.3 Analysis for wall and ground movements 399
10.5.4 Use of berms to control wall displacements 399
10.6 King post and soldier pile walls 404
10.1.1 In situ soil parameters 345
10.1.2 Wall friction 346
10.1.3 Wall adhesion 347
10.2 Preliminary design 347
10.2.1 Drainage and control of water 347
10.2.2 Design charts for waterfront structures 348
10.2.2.1 Cantilever sheet-pile walls 348
10.2.2.2 Singly anchored sheet-pile walls 354
10.2.3 Sheet-pile drivability 355
10.3 Design of sheet-pile walls using limit equilibrium calculations 356
10.3.1 Limit states and definitions of factor of safety 357
10.3.2 Effect of groundwater 357
10.3.3 Cantilever sheet-pile walls 359
10.3.4 Singly-anchored sheet-pile walls 365
10.3.4.1 Free-earth support method 366
10.3.4.2 Fixed-earth support method 370
10.3.5 Design of anchor systems 378
10.4 Propped and braced excavations 383
10.4.1 Calculation of prop loads 383
10.4.2 Base stability 388
10.4.3 Ground movements 392
10.4.4 Overall instability 394
10.5 Bored pile and diaphragm walls 396
10.5.1 Analysis for embedment, bending moments and prop loads 397
10.5.2 Wall deflections and ground movements 398
10.5.3 Analysis for wall and ground movements 399
10.5.4 Use of berms to control wall displacements 399
10.6 King post and soldier pile walls 404
11 Composite walls and other support systems 40711.1 Reinforced soil 407
11.1.1 Mechanics of reinforced soil 408
11.1.2 Detailed design of reinforced fill walls 409
11.1.3 External stability 411
11.1.3.1 Outward sliding on base 411
11.1.3.2 Toppling or limiting eccentricity 413
11.1.3.3 Bearing failure 413
11.1.3.4 Deep-seated failure 414
11.1.4 Internal stability 414
11.1.5 Pull-out capacity of different forms of earth reinforcement 430
11.1.5.1 Steel strip reinforcement 430
11.1.5.2 Synthetic strip reinforcement 431
11.1.5.3 Steel bar reinforcement 431
11.1.5.4 Woven and non-woven geotextiles 432
11.1.5.5 Wire mesh reinforcement 432
11.1.5.6 Polymer grid reinforcement 433
11.1.6 Factors for avoiding limit states in reinforced fill 434
11.2 Multi-anchored earth retaining structures 435
11.2.1 Grouted ground anchors 438
11.2.2 Mechanical ground anchors 441
11.3 Soil nailing 443
11.3.1 FHWA recommendations 444
11.3.1.1 ‘Global’ failure 445
11.3.1.2 Internal failure—nail-soil pull-out 447
11.3.1.3 Factors of safety 449
11.3.2 BS 8006-2 Recommendations 449
11.4 Design of bridge abutments for earth pressure 453
11.5 Cofferdams 458
11.5.1 Interlock strength of sheet-piles 465
11.5.2 Internal shear failure within the cell 466
11.5.2.1 Failure on a vertical plane at the centre of the cell 466
11.5.2.2 Failure on horizontal planes at the base of the cofferdam 469
11.5.3 Pull-out of outboard piles/Failure of inboard piles 471
11.5.4 External failure 472
11.5.4.1 Sliding failure 472
11.5.4.2 Bearing capacity failure 472
11.5.4.3 Overturning failure 473
11.5.4.4 Seepage failure 475
11.5.5 Numerical modelling 475
11.1.1 Mechanics of reinforced soil 408
11.1.2 Detailed design of reinforced fill walls 409
11.1.3 External stability 411
11.1.3.1 Outward sliding on base 411
11.1.3.2 Toppling or limiting eccentricity 413
11.1.3.3 Bearing failure 413
11.1.3.4 Deep-seated failure 414
11.1.4 Internal stability 414
11.1.5 Pull-out capacity of different forms of earth reinforcement 430
11.1.5.1 Steel strip reinforcement 430
11.1.5.2 Synthetic strip reinforcement 431
11.1.5.3 Steel bar reinforcement 431
11.1.5.4 Woven and non-woven geotextiles 432
11.1.5.5 Wire mesh reinforcement 432
11.1.5.6 Polymer grid reinforcement 433
11.1.6 Factors for avoiding limit states in reinforced fill 434
11.2 Multi-anchored earth retaining structures 435
11.2.1 Grouted ground anchors 438
11.2.2 Mechanical ground anchors 441
11.3 Soil nailing 443
11.3.1 FHWA recommendations 444
11.3.1.1 ‘Global’ failure 445
11.3.1.2 Internal failure—nail-soil pull-out 447
11.3.1.3 Factors of safety 449
11.3.2 BS 8006-2 Recommendations 449
11.4 Design of bridge abutments for earth pressure 453
11.5 Cofferdams 458
11.5.1 Interlock strength of sheet-piles 465
11.5.2 Internal shear failure within the cell 466
11.5.2.1 Failure on a vertical plane at the centre of the cell 466
11.5.2.2 Failure on horizontal planes at the base of the cofferdam 469
11.5.3 Pull-out of outboard piles/Failure of inboard piles 471
11.5.4 External failure 472
11.5.4.1 Sliding failure 472
11.5.4.2 Bearing capacity failure 472
11.5.4.3 Overturning failure 473
11.5.4.4 Seepage failure 475
11.5.5 Numerical modelling 475
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