Applied Geotechnics for Construction Projects, Volume 4 Retaining Structures, Soil Reinforcement and Improvement

Geotechnical engineering is now a fundamental component of construction projects. The fourth and final volume of this book presents a range of retaining structures, alongside soil reinforcement and improvement techniques and processes.

Applied Geotechnics for Construction Projects 4 first presents the concept of thrust-fall, then goes on to examine the behavior of retaining structures and their design and justification methods. A variety of practical applications for retaining structures are then considered, covering gravity walls, sheet pile curtains, in advance shoring excavations and retaining diaphragm walls. The book goes on to study soil reinforcement and improvement techniques, a subject that the author has dedicated thirty-five years to researching and teaching: from reinforced earth, in situ soil nailing, micropiles, in situ soil compaction, stone columns and rigid inclusions to "soil-cement" and "lime cement" columns. This book ends with a comprehensive and practical discussion of the behavior of underground structures; covering the concepts of convergence-confinement, stress evolution and subsidence estimation.

Each chapter of this fourth volume is illustrated with concrete examples and measurements of retaining structures, soil reinforcement and soil improvement from construction sites. The result is a combination of geotechnical expertise and lessons learned from experience, both of which are highly valuable in the field of applied geotechnics for construction projects.

Ammar Dhouib, doctor of civil engineering specializing in soil mechanics, is a lecturer and professor of geotechnics at Polytech Sorbonne University, Paris, France. He is also a geotechnical expert at the VINCI construction group and a justice expert at the Court of Appeal in Versailles. His research interests focus on geotechnics, and he has authored or co authored five books on this topic.

Foreword xi

Philippe GUILLERMAIN and François SCHLOSSER

Entrepreneur’s Tribune: Geotechnics is at the Heart of Our Projects xiii

Pascal LEMOINE and Eric DURAND

Preface xv

Acknowledgments xxi

Symbols and Notations xxiii

Introduction lvii

Chapter 1 Active and Passive Earth Pressures: Earth Retaining Structures 1

1.1 Active and passive earth pressures 1

1.1.1 Introduction 1

1.1.2 State of soils at rest 2

1.1.3 Active earth pressure in the soil 4

1.1.4 Passive earth pressure in the soil 8

1.1.5 Active and passive earth pressure forces 10

1.1.6 Active–passive pressure and back passive pressure: choice of incline 13

1.1.7 Active–passive earth pressures: specific cases 16

1.1.8 Effect of overloads 19

1.1.9 French practice 23

1.2 Behavior and sizing of earth retaining structures 25

1.2.1 Introduction: designing retaining structures 25

1.2.2 Classes of earth retaining structures 25

1.2.3 Limit conditions 27

1.2.4 History and path of the stresses 28

1.2.5 Behavior of rigid and flexible walls 31

1.3 Designing approaches 32

1.3.1 Classic failure analysis 33

1.3.2 Reaction coefficient method 34

1.3.3 Finite elements calculations 34

1.4 Method based on the reaction coefficient 35

1.4.1 Principle of the method 35

1.4.2 Soil/retaining structure reaction curve 36

1.4.3 Resolution method 39

1.4.4 Approaches for evaluating the reaction coefficient 40

1.5 The specific case of reinforced excavations 43

1.5.1 The principle of reinforcement 43

1.5.2 Horizontal stresses distribution diagrams 44

1.6 Subgrade stability 46

1.6.1 “Solid piping” 46

1.6.2 “Boiling” phenomenon 48

1.7 Applications 49

1.7.1 “Gravity” earth-retaining wall in a homogeneous soil mass 49

1.7.2 Study of a sheet piling using a classic failure analysis 61

1.7.3 Study of an advance shoring excavation 70

1.7.4 Project for a retaining diaphragm anchored by active tie rods 78

1.8 Incidents: they can happen quickly! 103

1.8.1 Case of a sheet piling fixed in chalk 103

1.8.2 Retaining diaphragm walls with tie rods and anchored in a substratum 104

1.8.3 Alternate pass shell technique 105

1.9 Appendices 107

1.9.1 Appendix 1: Ground friction/strut sealing 107

1.9.2 Appendix 2: Steel reinforcement of continuous walls 113

1.9.3 Appendix 3: Stability of the tie rod mass (Kranz approach) 115

1.9.4 Appendix 4: Stability and comparison of approaches in earthquake calculation for retaining gravity walls 116

1.10 References 119

Chapter 2 Soil Reinforcement and Improvement 123

2.1 Overview 123

2.1.1 Introduction 123

2.1.2 Historical and geographic context of the development of soil improvement techniques 125

2.1.3 The field and limits of the application of the different techniques 128

2.2 Reinforced Earth 131

2.2.1 Process 131

2.2.2 Construction method and displacement field 131

2.2.3 Displacement field 132

2.2.4 The surface of potential failure and tensile stresses in the reinforcement 133

2.2.5 Location and distribution of maximum tension in an RE wall 135

2.2.6 Friction between the soil and the RE reinforcement 136

2.2.7 Designing RE structures 137

2.2.8 The behavior of Reinforced Earth under triaxial shear testing 140

2.3 In situ soil nailing 141

2.3.1 The principles of nailing 141

2.3.2 The behavior of nailed walls 143

2.3.3 The interaction between the soil and the rod: the forces occurring around the rigid rod 145

2.3.4 The dimensions of the structures made from nailed earth 147

2.4 Soil reinforcement with micropiles 156

2.4.1 The principle of micropiles 156

2.4.2 Types of forces on micropiles and an assessment of possible actions 156

2.4.3 Theoretical study of an isolated micropile under centered axial load 158

2.4.4 An isolated micropile that causes a lateral reaction in the soil 160

2.4.5 Buckling of a micropile embedded into the soil 162

2.4.6 The effect of a group or a network: efficiency coefficient (k_ef) 163

2.4.7 Designing structures reinforced by micropiles 165

2.4.8 The justification of Eurocode micropile 168

2.5 Applications 170

2.5.1 The mixed structure: Reinforced Earth and nailed walls 170

2.5.2 Construction crane on top of a group of micropiles 182

2.5.3 Comparing some French guidelines 189

2.6 Other techniques of in situ soil improvement 194

2.6.1 Compaction through vibration 194

2.6.2 Dynamic compaction 198

2.6.3 Soil–cement mortar columns carried out by jet grouting 200

2.6.4 Stone columns 203

2.6.5 In situ soil improvement through the use of rigid inclusions 210

2.6.6 Deep compaction/solid injection 213

2.6.7 Mixing the soil with a binder: the lime–cement column 216

2.6.8 Consolidation by pre-loading 218

2.6.9 Vacuum consolidation 222

2.6.10 Other techniques 223

2.6.11 Classical injections 224

2.6.12 Soil freezing 226

2.6.13 Some economic data 228

2.7 Approaches to design 231

2.8 Applications 232

2.8.1 The study of embankment on stone columns 232

2.8.2 Study of an industrial paving on vertical rigid inclusions topped by stone columns 237

2.8.3 Reduction of the risk of liquefication with the vibro stone columns 242

2.8.4 The behavior of rigid inclusions under general rafts 246

2.9 A what not to do! 249

2.9.1 Case 1: building on stone columns 249

2.9.2 Data relative to the soil in case 1 249

2.9.3 Improving soils with stone columns (case 1) 250

2.9.4 Case 2: store with semi-rigid inclusions 253

2.9.5 Others (“school case”) 253

2.10 Appendices 253

2.10.1 Appendix 1: Sizing chart of the lateral limit friction between the soil/nail (Clouterre 1991) 253

2.10.2 Appendix 2: Practical sizing charts of stone columns 255

2.10.3 Appendix 3: Sizing charts for the global safety coefficient of embankments on soil treated with stone columns 258

2.10.4 Appendix 4: Structural verification of the support plate and the tie rod beams 262

2.11 References 265

Chapter 3 Underground Works: Convergence–Confinement Method 273

3.1 Introduction 273

3.1.1 Underground cavities 274

3.1.2 Definition of a tunnel and its supporting structures 275

3.2 Failure area at the vault of the tunnel and forces 276

3.2.1 Failure area at the vault of the tunnel 276

3.2.2 Forces on the supporting structures 277

3.3 Displacement of the receiving terrains 278

3.3.1 Convergence of tunnels and extrusion 278

3.3.2 Surface displacement (“subsidence”) 279

3.4 Mechanic behavior of tunnels 280

3.4.1 “Convergence–confinement” method 281

3.4.2 Simple methodology for estimating settlement 283

3.5 Dig methods and retaining structure types 286

3.5.1 Dig methods 286

3.5.2 Requirements and support types 286

3.6 Practical applications 288

3.6.1 Estimating the settlements empirically 288

3.6.2 Some practical results relating to surface settlement 295

3.6.3 Modeling with plane deformations 297

3.7 References 299

French, European and ISO Standards in the Field of Geotechnics 303

Index 335

Summaries of Other Volumes 337

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