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INTRODUCTION TO SOFT SOIL

GEOTECHNIQUE

Content, Context and Application

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INTRODUCTION TO SOFT SOIL

GEOTECHNIQUE

Content, Context and Application

Frans B. J. BarendsTechnical University Delft / Deltares

May 2011

IOS Press

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Deltares provided financial sponsorship for this publication

2011 The author and IOS Press. All rights reserved

ISBN 978-1-60750-788-8 (print)

ISBN 987-1-60750-789-5 (online)

PublisherIOS Press BV

Nieuwe Hemweg 6b

1013 BG Amsterdam

The NetherlandsTel: +31-20-688 3355

Fax: +31-20-687 0019

Email: info@iospress.nl

www.iospress.nl

LEGAL NOTE

The author and the publisher are not responsible for the use that might be made of

the information in this book.

PRINTED IN THE NETHERLANDS

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FOREWORD

All over the world, habitable space in deltas and river basins is under increasing

pressure from economic expansion, growing populations, subsidence and the

impacts of climate change. It is expected that, within 40 years from now, about 80percent of all people will live in deltaic regions. The Netherlands is a typical

example of such an area. The geological stratification consists of typical soft to

very soft soils, especially in the western part of the country. More than half of the

country is located below sea level, the surface of the land is flat, and the

groundwater table is extremely high. In these areas particularly it is important to

understand the complex behaviour of the subsoil, consisting of soft soils, like

organic clays, loose sand deposits and peat. Keeping the water separated from the

land is a continuous challenge. It is important to search for solutions that draw on

the potential of the coastal system, that enhance safety in densely populated coastalareas, and that minimise the ecological impact. Building and maintaining

infrastructure in these areas is quite challenging. Expert knowledge of soil

mechanics and geotechnical engineering is essential to reduce the risks inherent to

construction on and in deltaic areas.

Soil mechanics and geotechnical engineering. Theory and practice. Both are

equally important in order to create a safe and sustainable living environment for

us and our (grand)children. Both theory and practice can be found in this

publication. In the first part, starting from the fundamental side, the ins and outs ofthe complicated multi-phase material which we call soil, are explained and

summarised. In the second and third part this theoretical knowledge is further

developed and used to analyse a large number of specific soil-related problems,

like slope stability, earth retaining structures, foundations, ground improvement,

environmental impact, underground construction, coastal engineering, dike

technology and so on.

The author has been active in this field for the past 40 years, well connected on

the one hand to the scientific world of soil mechanics and on the other hand to the(geotechnical) engineering practice. With this book, the author has left a legacy of

his wide knowledge and expertise to the younger professionals. It is particularly

valuable for the geotechnical engineer of the 21st century, living and working in

deltaic areas.

Peter van den Berg

Deltares, Director Geo-Engineering

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CONTENTS

VII

CONTENTS PAGE

Introduction 1

PART I FUNDAMENTALS AND CONCEPTS1 A history of geotechnical achievements 5

2 Characteristics of soils

a Geological data 25

b Gravimetric-volumetric data 26

c Atterberg limits 28

d Structure of granular soils 30

e Strength and stiffness aspects 32

Applications 323 Soil investigation

a Site investigation 37

b Laboratory testing 42

c Physical model testing strategy 46

Applications 50

4 Soil and groundwater

a Vertical soil stress 51

b Groundwater flow 52c Boiling, heave and piping 59

Applications 62

5 Uniaxial stress and strain

a Stress and strain 69

b Strain concept 70

c Uniaxial compressibility 72

Applications 73

6 Creep and consolidationa Time-dependency 77

b Creep 78

c One-dimensional consolidation 80

d Multi-dimensional consolidation 84

e Method of the transient leakage factor 86

Applications 88

7 Triaxial stress and strain

a Continuum mechanics 93

b Mohr-Coulomb model 96c Coefficient of earth pressure 97

d Triaxial cell 99

e Undrained strength 101

f TheA andB factor 102

Applications 104

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CONTENTS

VIII

PART II METHODOLOGY AND TOOLS

8 Uncertainty and reliabilitya Uncertainty in geotechnical engineering 109

b Partial safety factors 116

c Eurocode 7 and the observational method 119

d Risk approach and visualising the unseen 121

e Risk management process: GeoQ 124

f Expertise and experience: GeoBrain 126

Applications 129

9 Observation and prediction

a Physical simulation 133b Constitutive models 135

c Aspects of numerical simulation 143

d A visco-plastic analytical element method 149

Applications 157

PART III DESIGN AND CONSTRUCTION

10 Stability of slopes

a Limit analysis 163b Slide on long slopes (micro-stability) 164

c Slide on short slopes (macro-stability) 167

Applications 171

11 Stability of earth-retaining structures

a Gravity walls 176

b Embedded walls 179

c Slurry walls 182

d Reinforced walls 183

Applications 184

12 Footings and pile foundations

a Bearing capacity of footings 189

b Bearing capacity of pile foundations 193

c Deformation of foundations 199

d Dynamic soil response 201

Applications 207

13 Methods of ground improvement

a Gravity displacement methods 211b Replacement methods 212

c Mass improvement 213

d Stiff inclusions 218

e Bio-chemical treatment 223

Applications 224

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CONTENTS

IX

14 Environmental engineering

a Physical-chemical characteristics of soil 227

b Physical-chemical processes in soil 230

c Bio-chemical processes in soil 233

d Heat / cold transport in soil 234

e Land subsidence 239

Applications 247

15 Underground engineering

a Deep building pits 249

b Soft ground tunnel-boring techniques 252

c A cylindrical cavity in a uniform infinite soil 254d A horizontal cylindrical cavity in a uniform semi-infinite soil 258

e Tunnel boring design and construction 260

f Unseen leakage 263

Applications 264

16 Coastal engineering

a Hydro-geodynamics 267

b Waves on seabed 271

c Waves on breakwaters 281d A liquefaction model 286

e Squeezing 290

Applications 290

17 Dike engineering

a Deltas in the world 295

b History of Dutch dike engineering 297

c Philosophy of water defence 301

d State of the art 309

e Latest developments 312

ANNEX

I Answers to the applications 321

II Recommended literature 337

III About the author 339

IV Symbols, standards, units, keywords 345

V Name index 347

VI Subject index 351