Engineering Design in Geotechnics

The new edition contains a thorough revision of the 1st edition's content, which has been expanded appreciably, even though the number of chapters has been reduced to make room for the new material. The reader may find the new 1st chapter of the book most useful, as it gives an insight to the extent of problems with which a geotechnical engineer has to deal on an almost routine basis. It also provides some guidance as to how some problems can be tackled and solved in practice. In this respect, the chapter includes values of physical parameters most used in design, with the view to making the reader appreciate the difficulties related to having reliable representative experimental data, manifested by the wide limits of these parameters. Chapter 3, relating to the design of shallow foundations, has been revised in depth to include a wide range of foundation types, subjected to a variety of combined loading conditions. The chapter's content allows for the analysis of some of the most unusual types of structures such as a shallow foundation with a tilted base, founded on a sloping ground surface, and subjected to an inclined eccentric load, for which the inclination angle can be in any direction of space and the eccentricity can be of a two-way type. Furthermore, a new section is added at the end to deal with the design of combined foundations. Naturally, several worked examples are provided throughout the chapter to enhance the understanding of the design process. Equally, chapter 6 (the largest in size), relating to lateral pressure problems, has been thoroughly modified, with an emphasis on Boussinesq theory on lateral pressure. A comprehensive set of tables covering different types of soils, wall geometries, ground surface inclines, and external loading conditions are provided, with a clear guide on how they are used in design. Numerous detailed worked examples, providing clearer explanations of the design process, are also added. The content of the new chapter 5, devoted to the numerical modelling of laterally loaded piles is unique in nature, since it includes not only the computational molecules and the numerical form of different boundary conditions, but also their step by step implementation, culminating in the derivation of the system of simultaneous equations and their numerical solutions. Furthermore, both active and passive lateral loading conditions of piles are covered separately, so that the reader can master the difference in behaviour of such structures under different loading conditions. All remaing chapters have also been revised, and new material has been added where appropriate; the emphasis being on providing clearer explanations and a direct link to practice. Furthermore, a paragraph stating the general context at the beginning, as well as a summary at the end have been added to each chapter. Finally, it is perhaps appropriate to remind the reader that this book is published concurrently with the 2nd edition of its sister publication Physical Behaviour in Geotechnics.

Table of Contents:
Preface List of main symbols Conversion factors Acknowledgements 1- Design considerations 1 1-1 General aspects relating to site evaluation 1 1-2 Practical aspects & specific engineering solutions 3 1-3 Collapsible and expansive soils 19 1-4 Scour potential 21 1-5 Earthquake design 22 1-6 Frozen soils, frost heave & ice loading 24 1-7 Engineering properties of soils & rock masses 28 References 33 2- The stability of slopes 34 2-1 General context 34 2-2 Slope instability 35 2-3 Stability of infinite slopes 38 General case of flow 38 Flow parallel to the slope 40 2-4 Effect of cohesion on the stability of infinite slopes 42 2-5 Undrained analysis of infinite slopes 44 2-6 Stability of slopes with a circular failure surface 44 Total stress analysis 44 Effective stress analysis: the Bishop's method 47 Effect of porewater pressure on the long term stability of a slope 54 Effect of seepage forces on the stability of slopes 57 2-7 Location of the critical failure surface 61 2-8 Non-circular failure surfaces 62 2-9 Improvement of the stability of unsafe slopes 64 Use of geotextile reinforcement 64 Use of soil nails & rock bolts 69 Use of micropiles 77 Chapter 2 summary 82 Problems 84 References 88 3- Limit analysis applied to the bearing capacity of shallow foundations 89 3-1 General context 89 3-2 Introduction 90 3-3 Upper & lower bounds theorems 91 3-4 Kinematically admissible collapse mechanisms: undrained behaviour 92 3-5 Statically admissible stress fields: undrained behaviour 96 3-6 Kinematically admissible collapse mechanisms: drained behaviour 101 3-7 Statically admissible stress fields: drained behaviour 104 3-8 Effects of soil weight & cohesion: the bearing capacity equation 110 3-9 Bearing capacity under undrained conditions 113 3-10 Correction factors due to foundation shape & load eccentricity 114 3-11 Correction factors due to load inclination 122 3-12 Correction factors due to foundation depth 123 3-13 Correction factors due to a sloping soil edge & foundation base tilt 124 3-14 Allowable (safe) design pressure 128 3-15 Combined foundation design 164 Chapter 3 summary 177 Problems 179 References 185 4- Design of pile foundations 186 4-1 General context 186 4-2 Type of piles 187 4-3 Pile testing 195 4-4 Ultimate loading capacity of axially loaded single piles: the static method 201 General considerations 201 Undrained carrying capacity of single piles embedded in clays 205 Drained carrying capacity of single piles embedded in clays 209 Carrying capacity of single piles embedded in sand 216 4-5 Negative skin friction 220 4-6 Ultimate carrying capacity of pile groups 225 Group effect 225 Carrying capacity of piled foundations embedded in clays: undrained analysis 228 Design of free standing pile groups embedded in clays 234 Design of pile groups embedded in sand: drained analysis 235 Negative skin friction on pile groups 248 4-7 Settlement of single piles & pile groups 255 Chapter 4 summary 265 Problems 268 References 273 5- Numerical modelling of laterally loaded piles 275 5-1 General context 275 5-2 General aspects of the behaviour of laterally loaded piles 276 5-3 Piles subjected to active lateral loading 278 5-4 Effects of pile rigidity 279 5-5 Centered Finite Difference formulae 282 General concept 282 Centered Finite Difference approximation with second order error 283 Centered Finite Difference approximation with fourth order error 283 Non symmetrical centered difference approximation applied to points just inside a boundary 284 5-6 Finite Difference formulation of laterally loaded piles: second order error formulation 284 Computational molecules 284 Boundary conditions at the pile's head 287 Boundary conditions at the pile's tip 289 Numerical implementation of a prescribed displacement 291 Effects of mesh size on the numerical solution 300 Effects of multi-layered soils 303 5-7 Finite Difference formulation of laterally loaded piles: fourth order error formulation 310 5-8 Piles subjected to passive lateral loading 323 Chapter 5 summary 336 Problems 339 References 340 6- Lateral earth pressure exerted on retaining structures 341 6-1 General context 341 6-2 Coefficients of earth pressure 342 6-3 At rest stress conditions: coefficient 344 6-4 Active and passive stress conditions: Rankine theory 345 6-5 Coulomb theory 350 6-6 Coulomb graphical solution adapted to multi-layered soils with uneven surface 360 6-7 Coulomb special analytical solutions to lateral thusts 374 6-8 Boussinesq theory 387 Introduction 387 Pressure due to the weight of a frictional cohesionless soil 388 Pressure due to a uniform surcharge on a weightless cohesionless soil 399 Pressure due to the cohesion of a weightless soil 408 6-9 Lateral thrust due to different types of ground loading 410 6-10 Effect of water pressure on the lateral thrust exerted on retaining structures 414 6-11 Boussinesq solution adapted to isotropic homogeneous backfill, with uneven surface 431 6-12 Boussinesq or Coulomb? 437 6-13 Practical aspects of the design of retaining walls 444 6-14 Stability criteria relating to the design of retaining walls 446 Chapter 6 summary 456 Problems 458 References 462 7- Design of sheet-pile and diaphragm walls 463 7-1 General context 463 7-2 Introduction 464 7-3 Design methods 466 7-4 Design of anchored sheet piles using the modified free earth support method 467 7-5 Design of anchored sheet piles using the fixed earth support method 491 The elastic line method 491 Blum's equivalent beam method 493 7-6 Design of cantilever sheet piles & diaphragm walls 507 Chapter 7 summary 514 Problems 516 References 519 8- Design of tunnels 520 8-1 General context 520 8-2 The stability of cylindrical cavities: equilibrium equations 521 8-3 Stress analysis related to circular tunnels in clays and in sand 523 Circular tunnels in fine-grained soils 523 Circular tunnels in granular soils 527 8-4 Tunnelling in rocks 529 8-5 Calculation of settlements induced by tunnelling 535 3-D settlements 535 2-D surface and sub-surface settlements 544 Surface and sub-surface settlements induced by microtunnelling 548 8-6 Tunnelling methods in soft grounds 549 The sprayed concrete lining design method 549 Tunnel boring machines 552 The Channel Tunnel: case study 559 Chapter 8 summary 566 Problems 568 References 571 Index 572

About the Author :
Fethi Azizi has a rich and unique professional background, based on more than 30 years experience in research and teaching in geotechnical engineering, acquired at the Laboratoire Central des Ponts et Chaussees in Paris, the University of Manitoba in Canada, the Queen's University of Belfast and the University of Plymouth. He is a Chartered Engineer, European Engineer, Member of the Institution of Civil Engineers, a Chartered Mathematician and Fellow of the Institute of Mathematics & its Applications, London.