List of Figures ............................................. xv
Preface ................................................. xxxiii
Author .................................................. xxxvii
List of Symbols .......................................... xxxix
1 Strength and stiffness from in situ tests .................... 1
1.1 Standard penetration tests (SPT) ........................ 1
1.1.1 Modification of raw SPT values ................... 1
1.1.1.1 Method A ................................ 2
1.1.1.2 Method В ................................ 3
1.1.2 Relative density ................................. 3
1.1.3 Undrained soil strength vs. SPT N ................ 5
1.1.4 Friction angle vs. SPT N, Dr, and Ip ............. 6
1.1.5 Parameters affecting strength .................... 8
1.2 Cone penetration tests ................................. 10
1.2.1 Undrained shear strength ........................ 11
1.2.2 SPT blow counts using qc ........................ 11
1.3 Soil stiffness ......................................... 11
1.4 Stiffness and strength of rock ......................... 13
1.4.1 Strength of rock ................................ 13
1.4.2 Shear modulus of rock ........................... 15
2 Capacity of vertically loaded piles ......................... 19
2.1 Introduction ........................................... 19
2.2 Capacity of single piles ............................... 19
2.2.1 Total stress approach: Piles in clay ............ 19
2.2.1.1 α Method (τs = αsu and qb) ............. 19
2.2.1.2 λ Method: Offshore piles ............... 22
2.2.2 Effective stress approach ....................... 23
2.2.2.1 β Method for clay (τs = βσ'vs) ......... 23
2.2.2.2 β Method for piles in sand (τs =
βσ'vs) ................................. 23
2.2.2.3 Base resistance qb (= Nq σ'vb) ......... 27
2.2.3 Empirical methods ............................... 29
2.2.4 Comments ........................................ 30
2.2.5 Capacity from loading tests ..................... 32
2.3 Capacity of single piles in rock ....................... 34
2.4 Negative skin friction ................................. 35
2.5 Capacity of pile groups ................................ 38
2.5.1 Piles in clay ................................... 39
2.5.2 Spacing ......................................... 39
2.5.3 Group interaction (free-standing groups) ........ 40
2.5.4 Group capacity and block failure ................ 41
2.5.4.1 Free-standing groups ................... 41
2.5.4.2 Capped pile groups versus free-
standing pile groups ................... 42
2.5.5 Comments on group capacity ...................... 44
2.5.6 Weak underlying layer ........................... 44
3 Mechanism and models for pile-soil interaction .............. 47
3.1 Concentric cylinder model (CCM) ........................ 47
3.1.1 Shaft and base models ........................... 47
3.1.2 Calibration against numerical solutions ......... 49
3.1.2.1 Base load transfer factor .............. 51
3.1.2.2 Shaft load transfer factor ............. 52
3.1.2.3 Accuracy of load transfer approach ..... 55
3.2 Nonlinear concentric cylinder model .................... 59
3.2.1 Nonlinear load transfer model ................... 59
3.2.2 Nonlinear load transfer analysis ................ 64
3.2.2.1 Shaft stress-strain nonlinearity
effect ................................. 64
3.2.2.2 Base stress-strain nonlinearity
effect ................................. 65
3.3 Time-dependent CCM ..................................... 65
3.3.1 Nonlinear visco-elastic stress-strain model ..... 67
3.3.2 Shaft displacement estimation ................... 69
3.3.2.1 Visco-elastic shaft model .............. 69
3.3.2.2 Nonlinear creep displacement ........... 72
3.3.2.3 Shaft model versus model loading
tests .................................. 74
3.3.3 Base pile-soil interaction model ................ 77
3.3.4 GASPILE for vertically loaded piles ............. 78
3.3.5 Visco-elastic model for reconsolidation ......... 78
3.4 Torque-rotation transfer model ......................... 78
3.4.1 Nonhomogeneous soil profile ..................... 79
3.4.2 Nonlinear stress-strain response ................ 79
3.4.3 Shaft torque-rotation response .................. 80
3.5 Coupled elastic model for lateral piles ................ 81
3.5.1 Nonaxisymmetric displacement and stress field ... 82
3.5.2 Short and long piles and load transfer factor ... 83
3.5.3 Subgrade modulus ................................ 87
3.5.4 Modulus k for rigid piles in sand ............... 90
3.6 Elastic-plastic model for lateral piles ................ 93
3.6.1 Features of laterally loaded rigid piles ........ 94
3.6.1.1 Critical states ........................ 94
3.6.1.2 Loading capacity ....................... 96
3.6.2 Generic net limiting force profiles (LFP)
(plastic state) ................................. 98
4 Vertically loaded single piles ............................. 105
4.1 Introduction .......................................... 105
4.2 Load transfer models .................................. 106
4.2.1 Expressions of nonhomogeneity .................. 106
4.2.2 Load transfer models ........................... 106
4.3 Overall pile-soil interaction ......................... 108
4.3.1 Elastic solution ............................... 109
4.3.2 Verification of the elastic theory ............. 110
4.3.3 Elastic-plastic solution ....................... 113
4.4 Paramatric study ...................................... 119
4.4.1 Pile-head stiffness and settlement ratio (Guo
and Randolph 1997a) ............................ 119
4.4.2 Comparison with existing solutions (Guo and
Randolph 1998) ................................. 119
4.4.3 Effect of soil profile below pile base (Guo
and Randolph 1998) ............................. 122
4.5 Load settlement ....................................... 122
4.5.1 Homogeneous case (Guo and Randolph 1997a) ...... 125
4.5.2 Nonhomogeneous case (Guo and Randolph 1997a) ... 126
4.6 Settlement influence factor ........................... 127
4.7 Summary ............................................... 131
4.8 Capacity for strain-softening soil .................... 132
4.8.1 Elastic solution ............................... 132
4.8.2 Plastic solution ............................... 134
4.8.3 Load and settlement response ................... 135
4.9 Capacity and cyclic amplitude ......................... 142
5 Time-dependent response of vertically loaded piles ......... 147
5.1 Visco-elastic load transfer behavior .................. 147
5.1.1 Model and solutions ............................ 148
5.1.1.1 Time-dependent load transfer model .... 148
5.1.1.2 Closed-form solutions ................. 149
5.1.1.3 Validation ............................ 151
5.1.2 Effect of loading rate on pile response ........ 152
5.1.3 Applications ................................... 152
5.1.4 Summary ........................................ 156
5.2 Visco-elastic consolidation ........................... 158
5.2.1 Governing equation for reconsolidations ........ 159
5.2.1.1 Visco-elastic stress-strain model ..... 159
5.2.1.2 Volumetric stress-strain relation of
soil skeleton ......................... 160
5.2.1.3 Flow of pore water and continuity of
volume strain rate .................... 162
5.2.1.4 Comments and diffusion equation ....... 163
5.2.1.5 Boundary conditions ................... 163
5.2.2 General solution to the governing equation ..... 163
5.2.3 Consolidation for logarithmic variation of u0 .. 165
5.2.4 Shaft capacity ................................. 168
5.2.5 Visco-elastic behavior ......................... 169
5.2.6 Case study ..................................... 171
5.2.6.1 Comments on the current predictions .... 175
5.2.7 Summary ........................................ 175
6 Settlement of pile groups .................................. 177
6.1 Introduction .......................................... 177
6.2 Empirical methods ..................................... 178
6.3 Shallow footing analogy ............................... 178
6.4 Numerical methods ..................................... 180
6.4.1 Boundary element (integral) approach ........... 180
6.4.2 Infinite layer approach ........................ 181
6.4.3 Nonlinear elastic analysis ..................... 182
6.4.4 Influence of nonhomogeneity .................... 182
6.4.5 Analysis based on interaction factors and
superposition principle ........................ 183
6.5 Boundary element approach: GASGROUP ................... 184
6.5.1 Response of a pile in a group .................. 184
6.5.1.1 Load transfer for a pile .............. 184
6.5.1.2 Pile-head stiffness ................... 185
6.5.1.3 Interaction factor .................... 186
6.5.1.4 Pile group analysis ................... 187
6.5.2 Methods of analysis ............................ 187
6.5.3 Case studies ................................... 192
6.6 Comments and conclusions .............................. 199
7 Elastic solutions for laterally loaded piles ............... 201
7.1 Introduction .......................................... 201
7.2 Overall pile response ................................. 202
7.2.1 Nonaxisymmetric displacement and stress field .. 202
7.2.2 Solutions for laterally loaded piles
underpinned by k and Np ........................ 205
7.2.3 Pile response under various boundary
conditions ..................................... 208
7.2.4 Load transfer factor γb ........................ 209
7.2.5 Modulus of subgrade reaction and fictitious
tension ........................................ 211
7.3 Validation ............................................ 212
7.4 Parametric study ...................................... 212
7.4.1 Critical pile length ........................... 212
7.4.2 Short and long piles ........................... 213
7.4.3 Maximum bending moment and the critical depth .. 213
7.4.3.1 Free-head piles ....................... 213
7.4.3.2 Fixed-head piles ...................... 216
7.4.4 Effect of various head and base conditions ..... 216
7.4.5 Moment-induced pile response ................... 218
7.4.6 Rotation of pile-head .......................... 218
7.5 Subgrade modulus and design charts .................... 218
7.6 Pile group response ................................... 220
7.6.1 Interaction factor ............................. 220
7.7 Conclusion ............................................ 227
8 Laterally loaded rigid piles ............................... 229
8.1 Introduction .......................................... 229
8.2 Elastic plastic solutions ............................. 230
8.2.1 Features of laterally loaded rigid piles ....... 230
8.2.2 Solutions for pre-tip yield state (Gibson pu,
either k) ...................................... 232
8.2.2.1 H, ug, ω, and zr for Gibson pu and
Gibson к .............................. 232
8.2.2.2 H, ug, ω, and zr for Gibson pu and
constant к ............................ 236
8.2.3 Solutions for pre-tip yield state (constant
pu and constant k) ............................ 237
8.2.4 Solutions for post-tip yield state (Gibson pu
either k) ...................................... 238
8.2.4.1 H, us and z for Gibson pu and
Gibson k .............................. 238
8.2.4.2 H, us and z for Gibson pu and
constant к ............................ 239
8.2.5 Solutions for post-tip yield state (constant pu
and constant k) ................................ 241
8.2.6 Ug, ω, and p profiles (Gibson pu, tip-yield
state) ......................................... 241
8.2.7 ug, ω, and p profiles (constant pu,
tip-yield state) ............................... 244
8.2.8 Yield at rotation point (YRP, either pu ........ 245
8.2.9 Maximum bending moment and its depth
(Gibson pu ..................................... 245
8.2.9.1 Pre-tip yield (z0 < z*) and
tip-yield (z0 - z*) states ............ 245
8.2.9.2 Yield at rotation point (Gibson pu) ... 248
8.2.10 Maximum bending moment and its depth (constant
pu ............................................. 248
8.2.10.1 Pre-tip yield (z0 < z*) and tip-yield
(z0 = z*) states ...................... 248
8.2.10.2 Yield at rotation point (constant
pu) ............................................ 249
8.2.11 Calculation of nonlinear response .............. 250
8.3 Capacity and lateral-moment loading loci .............. 253
8.3.1 Lateral load-moment loci at tip-yield and YRP
state .......................................... 253
8.3.2 Ultimate lateral load H0 against existing
solutions ...................................... 255
8.3.3 Lateral-moment loading locus ................... 257
8.3.3.1 Impact of pu profile (YRP state) on M0
and Mm ................................ 257
8.3.3.2 Elastic, tip-yield, and YRP loci for
constant pu ........................... 261
8.3.3.3 Impact of size and base (pile-tip)
resistance ............................ 264
8.4 Comparison with existing solutions ............... 266
8.5 Illustrative examples ............................ 268
8.6 Summary .......................................... 275
9 Laterally loaded free-head piles ........................... 277
9.1 Introduction .......................................... 277
9.2 Solutions for pile-soil system ........................ 279
9.2.1 Elastic-plastic solutions ...................... 280
9.2.1.1 Highlights for elastic-plastic
response profiles ..................... 280
9.2.1.2 Critical pile response ................ 284
9.2.2 Some extreme cases ............................. 286
9.2.3 Numerical calculation and back-estimation of
LFP ............................................ 292
9.3 Slip depth versus nonlinear response .................. 296
9.4 Calculations for typical piles ........................ 296
9.4.1 Input parameters and use of GASLFP ............. 296
9.5 Comments on use of current solutions .................. 308
9.5.1 32 Piles in clay ............................... 308
9.5.2 20 Piles in sand ............................... 313
9.5.3 Justification of assumptions ................... 322
9.6 Response of piles under cyclic loading ................ 325
9.6.1 Comparison of p-y(w) curves .................... 325
9.6.2 Difference in predicted pile response .......... 327
9.6.3 Static and cyclic response of piles in
calcareous sand ................................ 328
9.7 Response of free-head groups .......................... 334
9.7.1 Prediction of response of pile groups
(GASLGROUP) .................................... 335
9.8 Summary ............................................... 339
10 Structural nonlinearity and response of rock-socket
piles ...................................................... 341
10.1 Introduction .......................................... 341
10.2 Solutions for laterally loaded shafts ................. 343
10.2.1 Effect of loading eccentricity on shaft
response ...................................... 343
10.3 Nonlinear structural behavior of shafts ............... 346
10.3.1 Cracking moment Mcr and effective flexural
rigidity EcIc .................................. 346
10.3.2 Mult and Icr for rectangular and circular
cross-sections ................................. 347
10.3.3 Procedure for analyzing nonlinear shafts ....... 350
10.3.4 Modeling structure nonlinearity ................ 350
10.4 Nonlinear piles in sand/clay .......................... 352
10.4.1 Taiwan tests: Cases SN1 and SN2 ................ 352
10.4.2 Hong Kong tests: Cases SN3 and SN4 ............. 356
10.4.3 Japan tests: CN1 and CN2 ....................... 359
10.5 Rock-socketed shafts .................................. 361
10.5.1 Comments on nonlinear piles and rock-socketed
shafts ......................................... 371
10.6 Conclusion ............................................ 372
11 Laterally loaded pile groups ............................... 375
11.1 Introduction .......................................... 375
11.2 Overall solutions for a single pile ................... 376
11.3 Nonlinear response of single piles and pile groups .... 379
11.3.1 Single piles ................................... 379
11.3.2 Group piles .................................... 381
11.4 Examples .............................................. 386
11.5 Conclusions ........................................... 401
12 Design of passive piles .................................... 405
12.1 Introduction .......................................... 405
12.1.1 Flexible piles ................................. 406
12.1.2 Rigid piles .................................... 407
12.1.3 Modes of interaction ........................... 408
12.2 Mechanism for passive pile-soil interaction ........... 409
12.2.1 Load transfer model ............................ 409
12.2.2 Development of on-pile force p profile ......... 410
12.2.3 Deformation features ........................... 412
12.3 Elastic-plastic (EP) solutions ........................ 414
12.3.1 Normal sliding (upper rigid-lower flexible) .... 414
12.3.2 Plastic (sliding layer)-elastic-plastic
(stable layer) (P-EP) solution ................. 415
12.3.3 EP solutions for stable layer .................. 417
12.4 pa-based solutions (rigid piles) ...................... 421
12.5 E-E, EP-EP solutions (deep sliding-flexible piles) .... 430
12.5.1 EP-EP solutions (deep sliding) ................. 430
12.5.2 Elastic (sliding layer)-elastic (stable
layer) (E-E) solution .......................... 430
12.6 Design charts ......................................... 433
12.7 Case study ............................................ 435
12.7.1 Summary of example study ....................... 444
12.8 Conclusion ............................................ 444
13 Physical modeling on passive piles ......................... 447
13.1 Introduction .......................................... 447
13.2 Apparatus and test procedures ......................... 448
13.2.1 Salient features of shear tests ................ 448
13.2.2 Test program ................................... 450
13.2.3 Test procedure ................................. 451
13.2.4 Determining pile response ...................... 455
13.2.5 Impact of loading distance on test results ..... 455
13.3 Test results .......................................... 456
13.3.1 Driving resistance and lateral force on
frames ......................................... 456
13.3.2 Response of Mmax, y0, to versus wi (wf) ........ 460
13.3.3 Mmax raises (T block) .......................... 465
13.4 Simple solutions ...................................... 467
13.4.1 Theoretical relationship between Mmax and
Tmax ........................................... 467
13.4.2 Measured Mmax and Tmax and restraining moment
Moi ............................................ 468
13.4.3 Equivalent elastic solutions for passive
piles .......................................... 470
13.4.4 Group interaction factors Fm Fk and pm ......... 472
13.4.5 Soil movement profile versus bending moments ... 473
13.4.6 Prediction of Tmaxi and Mmaxi ................... 474
13.4.6.1 Soil movement profile versus
bending moments ....................... 474
13.4.7 Examples of calculations of Mmax ............... 475
13.4.8 Calibration against in situ test piles ......... 478
13.5 Conclusion ............................................ 482
Acknowledgment ................................................ 484
References .................................................... 485
Index ......................................................... 509
|
