Table Of ContentAnalysis and design of
geotechnical structures
Analysis and design of
geotechnical structures
Manuel Matos Fernandes
First edition published 2020
by CRC Press
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Library of Congress Cataloging-in-Publication Data
Names: Fernandes, Manuel Matos, author.
Title: Analysis and design of geotechnical structures / Manuel Matos
Fernandes.
Description: First edition. | Abingdon, Oxon ; Boca Raton, FL : CRC Press,
2020. | Includes bibliographical references and index.
Identifiers: LCCN 2020009402 (print) | LCCN 2020009403 (ebook) | ISBN
9780367026639 (pbk) | ISBN 9780367026622 (hbk) | ISBN 9780429398452
(ebk) | ISBN 9780429676161 (adobe pdf) | ISBN 9780429676147 (mobi) |
ISBN 9780429676154 (epub)
Subjects: LCSH: Geotechnical engineering--Textbooks.
Classification: LCC TA705 .F428 2020 (print) | LCC TA705 (ebook) | DDC
624.1/51--dc23
LC record available at https://lccn.loc.gov/2020009402
LC ebook record available at https://lccn.loc.gov/2020009403
Typeset in Sabon
by Deanta Global Publishing Services, Chennai, India
Contents
Preface xix
Author xxi
1 Geotechnical characterization: In situ testing 1
1.1 Introduction 1
1.2 Geotechnical investigation 2
1.2.1 Preliminary surface survey 2
1.2.2 Geophysical investigation 2
1.2.2.1 Introduction 2
1.2.2.2 Electrical resistivity method 3
1.2.2.3 Seismic refraction method 4
1.2.2.4 Spectral-analysis-of-surface-waves (SASW) method 5
1.2.2.5 Ground-penetrating radar (GPR) 6
1.2.3 Geomechanical investigation 7
1.2.3.1 Introduction 7
1.2.3.2 Trial pits and shafts 8
1.2.3.3 Borehole drilling 8
1.2.3.4 Rotary coring 9
1.2.4 Note on undisturbed soil sampling 11
1.2.4.1 Introduction 11
1.2.4.2 Direct sampling 12
1.2.4.3 Indirect sampling 12
1.2.4.4 Sampling of sands 14
1.3 In situ testing 16
1.3.1 Introduction 16
1.3.2 Standard penetration test (SPT) 17
1.3.2.1 Essential aspects of the equipment and test procedure 17
1.3.2.2 SPT corrections 19
1.3.2.3 Equipment calibration 21
1.3.2.4 Correlations of (N ) with soil properties and parameters 21
1 60
1.3.3 Cone penetrometer test (CPT/CPTu) 23
1.3.3.1 Essential aspects of the equipment and
test procedure: measured parameters 23
1.3.3.2 Interpretation of results: soil classification charts 25
1.3.3.3 Correlations with soil characteristics and parameters 31
v
vi Contents
1.3.4 Dynamic probing test (DP) 35
1.3.4.1 Essential aspects of the equipment and test procedure 35
1.3.4.2 Comment regarding the use of dynamic
probing tests: interpretation of results 37
1.3.5 Vane shear test (VST) 38
1.3.5.1 Essential aspects of the equipment and test procedure 38
1.3.5.2 Interpretation of test results for deriving c 38
u
1.3.6 Plate load test (PLT) 41
1.3.6.1 Essential aspects of the equipment and test procedure 41
1.3.6.2 Interpretation of results 42
1.3.6.3 Final remark 45
1.3.7 Cross-hole seismic test (CHT) 45
1.3.7.1 Essential aspects of the equipment and test procedure 45
1.3.7.2 Interpretation of results 46
1.3.7.3 Final remark 47
1.3.8 Down-hole seismic tests 48
1.3.9 Self-boring pressuremeter test (SBPT) 49
1.3.9.1 Essential aspects of the equipment and test procedure 49
1.3.9.2 Interpretation of results 51
1.3.10 Ménard pressuremeter test (PMT) 53
1.3.10.1 Essential aspects of the equipment and test procedure 53
1.3.10.2 Interpretation of results 54
1.3.11 Flat dilatometer test (DMT) 56
1.3.11.1 Essential aspects of the equipment and test procedure 56
1.3.11.2 Interpretation of results 58
1.3.12 Tests for permeability characterization 59
1.3.12.1 Pumping tests 59
1.3.12.2 Borehole or Lefranc tests 60
1.4 Global overview on site characterization 63
1.4.1 Summary of in situ tests 63
1.4.2 In situ versus laboratory tests 66
1.4.2.1 Introduction 66
1.4.2.2 Advantages and limitations of laboratory tests 66
1.4.2.3 Advantages and limitations of in situ tests 66
1.5 Stiffness characterization by means of in situ and laboratory tests 67
1.5.1 General overview: definitions 67
1.5.2 Small is beautiful 68
1.5.3 Relation of the tests to the strain level in the soil 71
1.5.4 Methodology for characterization of soil stiffness for all
strain levels 72
2 Overall stability of soil masses 77
2.1 Introduction 77
2.2 Introduction to limit analysis theory 78
2.2.1 Formulation: upper and lower bound theorems 78
Contents vii
2.2.2 Example of application – excavation with
vertical face under undrained conditions 79
2.3 Limit equilibrium methods 81
2.3.1 Introduction 81
2.3.2 Method of slices: general formulation 82
2.3.3 Fellenius method 83
2.3.4 Simplified Bishop method 84
2.3.5 Spencer method 85
2.3.6 Comment 87
2.4 Stability of embankments on soft clayey soil 88
2.4.1 Introduction 88
2.4.2 Application of the method of slices in total stress analyses 90
2.4.3 Methods to improve stability conditions 91
2.4.3.1 Lateral stabilizing berms 91
2.4.3.2 Staged construction 92
2.4.3.3 Foundation soil reinforcement with stone columns 94
2.4.3.4 Reinforcement of the base of the
embankment with geosynthetics 95
2.4.3.5 Use of lightweight aggregates as fill material 96
2.4.4 Comment 97
2.5 Unsupported cuts in clayey soil 97
2.5.1 Introduction: basic features 97
2.5.2 The question of safety and its evolution with time 99
2.5.3 Note about the maximum depth of tension
cracks on the ground surface 101
2.5.4 Cuts under undrained conditions 102
2.5.4.1 Vertical cuts 102
2.5.4.2 Inclined face excavations 106
2.5.5 Excavations in drained conditions: effective
stress analyses: Hoek and Bray charts 108
Annex A2.1 Stability analysis of embankments during staged construction 115
Annex A2.2 Stone column reinforcement of the
foundation of embankments on soft soil 116
Annex A2.3 Method of Leroueil and Rowe (2001) for the stability analysis of
embankments on soft soil with base reinforcement with geosynthetic 117
Annex E2 Exercises (resolutions are included in the Final Annex) 119
3 Basis of geotechnical design 123
3.1 Introduction 123
3.2 Variables and uncertainties in geotechnical design 123
3.3 Global safety factor method 126
3.3.1 Definition of global safety factor: typical values 126
3.3.2 Limitations of the global safety factor method 127
3.4 Limit state method and partial safety factors 129
3.4.1 General considerations 129
3.4.2 Distinct forms of application of the limit state method 131
viii Contents
3.5 Probabilistic methods 132
3.5.1 Safety margin, reliability index, and probability of failure 132
3.5.2 Application of probabilistic methods in geotechnical design 135
3.6 Introduction to Eurocode 7 – geotechnical design 136
3.6.1 The Structural Eurocodes: generalities 136
3.6.2 Design values of the actions, material
properties, and geometric data 138
3.6.3 The question of the characteristic value
of a geotechnical parameter 138
3.6.3.1 The concept of characteristic values of
a structural and a geotechnical material
parameter: Eurocode 0 versus Eurocode 7 138
3.6.3.2 The dependence on the structure and on
the limit state under consideration 140
3.6.3.3 The dependence on the size of the ground
region that affects a given limit state 141
3.6.4 Types of limit states 143
3.6.5 Verification of safety for STR and GEO limit states 144
3.6.6 The three design approaches 146
3.6.7 Comment about the justification for adopting a
unit safety factor for the permanent actions 149
3.6.8 Final comment and perspectives 150
3.7 Application of LRFD: AASHTO Code (2012) 150
3.8 Note about Eurocode 8: definition of seismic action 152
Annex A3.1 Summary of some probabilistic concepts 156
Annex A3.2 Partial safety factors for the EQU, UPL AND
HYD limit states, according to Eurocode 7 159
Annex A3.3 Design Approaches 1, 2 and 3 of Eurocode
7 for limit state types STR and GEO 161
A3.3.1 Partial safety factors on actions and the effect of actions 161
A3.3.2 Partial safety factors on material strengths and resistances 162
Annex A3.4 Resistance factors from LRFD bridge
design specifications (AASHTO, 2012) 163
4 Consolidation theories and delayed settlements in clay 167
4.1 Introduction 167
4.2 Stress–strain relations in soils loaded under constrained
conditions 167
4.2.1 Constrained loading: oedometer tests 167
4.2.2 Time effect: hydromechanical analogy 169
4.2.3 Load diagrams obtained in the oedometer test 170
4.2.4 Treatment of the compressibility curve 173
4.2.5 Parameters for the definition of the stress–strain relationships 174
4.2.6 Expressions for calculation of the consolidation settlement 176
4.2.7 Some practical issues 178
Contents ix
4.3 The Terzaghi consolidation theory 179
4.3.1 Base hypotheses: consolidation equation 179
4.3.2 Consolidation equation solutions 181
4.3.2.1 Layer with two draining boundaries 181
4.3.2.2 Layer with only one draining boundary 183
4.3.3 Consolidation settlement change over time 183
4.3.4 Estimation of c from oedometer tests 186
v
4.3.5 Settlement change taking into account construction time 187
4.4 Loading in general (non-constrained) conditions 188
4.4.1 Introduction: generalization of the hydromechanical analogy 188
4.4.2 Consolidation settlement calculation: classical
method of Skempton and Bjerrum 190
4.4.3 Two- and three-dimensional consolidation 193
4.4.3.1 Biot theory results 193
4.4.3.2 Solutions of Terzaghi’s theory for any
distributions of the initial excess pore pressure 196
4.5 Secondary consolidation 197
4.5.1 Introduction 197
4.5.2 Overconsolidation by secondary consolidation 197
4.5.3 Secondary consolidation settlement:
conventional and Brazilian approaches 198
4.6 Acceleration of consolidation 201
4.6.1 Introduction 201
4.6.2 Preloading 201
4.6.2.1 Base scheme 201
4.6.2.2 Calculation of the temporary surcharge 203
4.6.2.3 Comment: control of secondary
consolidation settlements 203
4.6.3 Vertical drains 205
4.6.3.1 General scheme: types of drains – installation 205
4.6.3.2 Radial consolidation 207
4.6.3.3 Smear effect 210
4.6.3.4 Calculation of the vertical drain network 211
4.6.4 Vacuum preloading 212
4.6.5 Note on the use of stone columns 213
4.7 Observation of embankments on soft soil 215
4.7.1 Installation points, equipment, and parameters to monitor 215
4.7.2 The Asaoka method 217
Annex A4.1 Deduction of Equations 218
A4.1.1 Equation 4.1 218
A4.1.2 Constancy of the ratio h/(1 + e) 218
Annex A4.2 Evaluation of s¢ by the Casagrande construction 219
p
Annex A4.3 Treatment of log s¢–e curves by the Schmertmann construction 219
v
Annex A4.4 Evaluation of the vertical consolidation coefficient, c 220
v
A4.4.1 The Taylor method 220
