CIRIA C580
London 2003
Embedded retaining walls –
guidance for economic
design
A R Gaba Ove Arup and Partners
B Simpson Ove Arup and Partners
W Powrie University of Southampton
D R Beadman Ove Arup and Partners
6 Storey's Gate, Westminster, London SW1P 3AU
TELEPHONE 020 7222 8891 FAX 020 7222 1708
EMAIL enquiries@ciria.org
WEBSITE www.ciria.org
Summary
This book provides best practice guidance on the selection and design of vertical
embedded retaining walls. It covers temporary and permanent cantilever, anchored,
single and multi-propped retaining walls that are supported by embedment in stiff clay
and other competent soils.
The content addresses the technical and construction issues relating to the selection of
appropriate wall type and construction sequence to achieve overall economy. It clarifies
areas of design ambiguity and presents a clear, unambiguous method for the design of
such walls.
Embedded retaining walls – guidance for economic design
Gaba, A R; Simpson, B; Powrie, W; Beadman, D R
Construction Industry Research and Information Association
CIRIA C580
© CIRIA 2003
RP629
ISBN 0 86017 580 4
Keywords
Ground engineering, ground investigation and characterisation, piling, soil-structure
interaction
Reader interest
Classification
Design, specification, construction,
managers, clients and supervising
engineers involved in civil and
geotechnical works
AVAILABILITY
Unrestricted
CONTENT
Subject area review
STATUS
Committee-guided
USER
Civil, geotechnical and
structural engineers,
engineering geologists
British Library Cataloguing in Publication Data
A catalogue record is available for this book from the British Library.
Published by CIRIA, 6 Storey’s Gate, Westminster, London SW1P 3AU.
All rights reserved. No part of this publication may be reproduced or transmitted in any
form or by any means, including photocopying and recording, without the written
permission of the copyright-holder, application for which should be addressed to the
publisher. Such written permission must also be obtained before any part of this
publication is stored in a retrieval system of any nature.
This publication is designed to provide accurate and authoritative information in regard
to the subject matter covered. It is sold and/or distributed with the understanding that
neither the authors nor the publisher is thereby engaged in rendering a specific legal or
any other professional service. While every effort has been made to ensure the accuracy
and completeness of the publication, no warranty or fitness is provided or implied, and
the authors and publisher shall have neither liability nor responsibility to any person or
entity with respect to any loss or damage arising from its use.
2
CIRIA C580
Acknowledgements
Research contractor This book is the main output from CIRIA Research Project 629. It was prepared by Ove
Arup and Partners Limited in conjunction with the University of Southampton and
Bachy Soletanche Limited.
Authors
Asim Gaba is a director of Ove Arup & Partners Ltd. He was lead author of this book,
and co-ordinated and managed inputs from the various contributors and advisers. He
has extensive experience of embedded retaining wall design and construction, as well as
of soil-structure interaction in relation to deep excavations and underground structures,
particularly for deep basements and mass rapid transit projects in the UK, Hong Kong
Singapore, Taiwan and Thailand.
Brian Simpson is a director of Ove Arup & Partners Ltd, editor of Géotechnique
(2000–2002) and a visiting professor at City University, London. He has long-term
interests in the design of retaining walls, investigation of failures, numerical analysis
and the development of Eurocode 7. He is a former Rankine lecturer and is the skills
leader for geotechnics throughout the global Arup practice
William Powrie is Professor of Geotechnical Engineering and head of the Department
of Civil and Environmental Engineering at the University of Southampton. He works
closely with industry on research encompassing retaining walls, groundwater control
and landfill engineering. He is the author of a number of journal papers and a textbook
on soil mechanics, and was awarded the ICE Telford Medal in 2001 for research on
loads in temporary props used to support the deep excavation for the Jubilee Line
Extension station at Canary Wharf.
David Beadman collated the Bachy Soletanche Ltd contribution to the book,
concentrating on the constructability and wall selection issues. He is an associate of
Ove Arup & Partners Ltd, and is experienced in developing economic, buildable
solutions for deep basement excavations, combining knowledge of retaining wall
design, structural design and construction.
Following CIRIA’s usual practice, the research project was guided by a steering group,
which comprised:
Steering group chair Mr J Findlay of Stent Foundations
Steering group
CIRIA C580
Dr D Bush
Highways Agency
Dr D Carder
Transport Research Laboratory
Mr S Everton
Gibb
Mr R Fernie
Skanska
Prof R Mair
Cambridge University
Mr B McGinnity
London Underground Limited
Mr D McNicholl
Wardell Armstrong
Mr A O’Brien
Mott MacDonald Limited
Prof D Potts
Imperial College
Mr D Rowbottom
Corus
Dr H St John
Geotechnical Consulting Group
Dr J Wilson
WS Atkins
Mr R Yenn
TPS Consult
3
Corresponding
member
Dr N O’Riordan
Rail Link Engineering
CIRIA manager
CIRIA’s research manager for this project was Dr A J Pitchford.
Project funders
This project was funded by:
Department of Trade and Industry (DTI) under the Partners in Innovation scheme
Highways Agency
Corus
CIRIA’s Core Programme sponsors.
Technical
contributors
CIRIA and the authors gratefully acknowledge the support of these funding
organisations, the technical advice and help given by the members of the steering group
and, in particular, the following individuals:
Mr A Pickles
Ove Arup and Partners Limited
Mr J Smethurst
Southampton University
Professor J H Atkinson
City University
Dr D Borin
Geosolve Limited
Mr D Twine
Rail Link Engineering
Mr M J Puller
Malcolm Puller Associates
Mrs J Senior
Ove Arup and Partners Limited
Mr J Taylor
Ove Arup and Partners Limited
Note
Recent UK Government reorganisation has meant that DETR responsibilities have been
moved variously to the Department of Trade and Industry (DTI), the Office of the
Deputy Prime Minister (ODPM), the Department for Environment, Food and Rural
Affairs (DEFRA) and the Department for Transport (DfT). References made to
government agencies in this publication should be read in this context.
For clarification, readers should contact the Department of Trade and Industry.
4
CIRIA C580
Contents
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
List of figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
List of tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
List of boxes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
1
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
1.1 Background to project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
1.2 Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
1.3 Readership . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
1.4 Applicability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
1.5 Economic design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
1.6 Book layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
2
DESIGN CONSIDERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
2.1 Health and safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
2.2 Design concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
2.3 Design requirements and performance criteria . . . . . . . . . . . . . . . . . . . . .38
2.4 Limit states . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39
2.5 Ground movements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42
2.6 Key points and recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65
3
CONSTRUCTION CONSIDERATIONS AND WALL SELECTION . . . .67
3.1 Construction methods for soil support . . . . . . . . . . . . . . . . . . . . . . . . . . .68
3.2 Types of embedded retaining walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83
3.3 Wall selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .87
3.4 Key points and recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .90
4
ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .91
4.1 Earth pressures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .91
4.2 Methods of analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .107
4.3 Effect of method of analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .127
4.4 Key points and recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .130
5
DETERMINATION AND SELECTION OF PARAMETERS . . . . . . . . .133
5.1 Design parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .134
5.2 Investigation of ground and groundwater conditions . . . . . . . . . . . . . . .136
5.3 Assessment of drained/undrained soil conditions . . . . . . . . . . . . . . . . . .141
5.4 Determination of soil parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .142
5.5 Determination of groundwater pressures . . . . . . . . . . . . . . . . . . . . . . . . .161
5.6 Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .166
5.7 Unplanned excavation of formation . . . . . . . . . . . . . . . . . . . . . . . . . . . .168
CIRIA C580
5
5.8 Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .169
5.9 Selection of design parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .170
5.10 Key points and recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .177
6
DESIGN OF WALL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .183
6.1 Design philosophy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .185
6.2 Design method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .185
6.3 ULS calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .188
6.4 SLS calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .194
6.5 Progressive failure check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .197
6.6 Structural design of wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .197
6.7 Worked example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .205
6.8 Key points and recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .205
7
DESIGN OF SUPPORT SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .207
7.1 Propping systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .207
7.2 Berms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .213
7.3 Anchors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .220
7.4 Key points and recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .221
8
AREAS OF FURTHER WORK AND RESEARCH . . . . . . . . . . . . . . . . .223
9
REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .225
APPENDICES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .247
A1 EXAMPLE CDM RISK ASSESSMENT FORMS . . . . . . . . . . . . . . .249
A2 GROUND MOVEMENTS AND CASE HISTORY DATA . . . . . . . .253
A2.1 Ground movements due to wall installation . . . . . . . . . . . . . . . .253
A2.2 Ground heave . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .260
A2.3 Ground movements due to wall deflection . . . . . . . . . . . . . . . . .261
A2.4 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .282
A3 WALL TYPES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .285
A3.1 Sheet piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .285
A3.2 Combi wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .288
A3.3 King post wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .288
A3.4 Contiguous pile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .288
A3.5 Hard/soft secant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .290
A3.6 Hard/firm secant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .291
A3.7 Hard/hard secant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .292
A3.8 Diaphragm walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293
A3.9 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .295
A4 SOIL MECHANICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .297
A4.1 Stress analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .297
A4.2 Drained and undrained conditions . . . . . . . . . . . . . . . . . . . . . . . .300
A4.3 Stress history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .302
A4.4 Soil shear strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .303
A4.5 Soil stiffness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .310
A4.6 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .311
6
CIRIA C580
A5 EFFECTS OF WALL INSTALLATION . . . . . . . . . . . . . . . . . . . . . . .313
A5.1 Concrete diaphragm and bored pile walls . . . . . . . . . . . . . . . . . .313
A5.2 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .315
A6 EARTH PRESSURE COEFFICIENTS . . . . . . . . . . . . . . . . . . . . . . .317
A6.1 Numerical procedure for calculating earth pressure
coefficients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .317
A6.2 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .326
A7 COMPARISON OF LUMPED MOMENT FACTORS WITH
FACTOR ON STRENGTH METHOD IN LIMIT EQUILIBRIUM
CALCULATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .327
A7.1 Traditional design methods for embedded walls . . . . . . . . . . . . .327
A7.2 Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .328
A7.3 Comparison of methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .329
A7.4 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .334
A8 REVIEW OF DESIGN METHODS TO BS 8002 (1994), EC7 (1995)
AND BD42 (DMRB 2.1.2) (2000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .335
A8.1 UK codes of practice and design standards . . . . . . . . . . . . . . . . .335
A8.2 BS 8002 (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .335
A8.3 Eurocode EC7 (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .339
A8.4 BD 42/00 (DMRB 2.1.2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .344
A8.5 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .352
A9 ANALYSIS OF BERMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .355
A9.1 Multiple Coulomb wedge limit equilibrium analysis . . . . . . . . .355
A9.2 General finite element analysis of an earth berm removed in
sections from in front of a long retaining wall . . . . . . . . . . . . . .357
A9.3 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .358
A10 EFFECT OF METHOD OF ANALYSIS . . . . . . . . . . . . . . . . . . . . . . .359
A10.1 Methods of analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .359
A10.2 Software packages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .359
A10.3 Problems analysed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .359
A10.4 Assumptions and analysis procedure . . . . . . . . . . . . . . . . . . . . . .362
A10.5 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .364
A10.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .378
A11 WORKED EXAMPLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .379
CIRIA C580
7
List of figures
8
Figure 1.1
Wall types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
Figure 1.2
Principal design stages and book layout . . . . . . . . . . . . . . . . . . . . . .23
Figure 1.3
Key issues considered in the book . . . . . . . . . . . . . . . . . . . . . . . . . .24
Figure 2.1
Decision paths for selection of appropriate wall type and
construction sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
Figure 2.2
Conditions of contract in use in UK construction . . . . . . . . . . . . . . .29
Figure 2.3
CDM risk assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
Figure 2.4
Geotechnical categorisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
Figure 2.5
Elements of geotechnical design . . . . . . . . . . . . . . . . . . . . . . . . . . . .36
Figure 2.6
Ultimate limit state examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
Figure 2.7
Movements due to water flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46
Figure 2.8
Ground surface movements due to bored pile wall installation in
stiff clay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48
Figure 2.9
Ground surface movements due to diaphragm wall installation in
stiff clay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49
Figure 2.10
Typical ground movement pattern associated with excavation stress
relief . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51
Figure 2.11
Ground surface movements due to excavation in front of wall in
stiff clay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55
Figure 2.12
Ground surface settlement due to excavation in front of wall in sand 56
Figure 2.13
Maximum lateral wall movement versus system stiffness . . . . . . . .56
Figure 2.14
Procedure for prediction of wall deflections and ground surface
movements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57
Figure 2.15
Simple field of plastic deformation . . . . . . . . . . . . . . . . . . . . . . . . . .59
Figure 2.16
Relation between analysed lateral (propped) wall deflections and
predicted ground surface settlements in stiff soil . . . . . . . . . . . . . . .60
Figure 2.17
Procedure for building damage assessment . . . . . . . . . . . . . . . . . . .62
Figure 2.18
Relationship between damage category, deflection ratio and
horizontal tensile strain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64
Figure 3.1
Decision paths for selection of appropriate wall type and
construction sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67
Figure 3.2
Temporary and permanent works: Bristol underground car park.
An example of the use of a sheet pile wall as the permanent wall,
exposed and painted . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69
Figure 3.3
Cantilever wall construction sequence . . . . . . . . . . . . . . . . . . . . . . .70
Figure 3.4
Top-down construction sequence . . . . . . . . . . . . . . . . . . . . . . . . . . .71
Figure 3.5
Top-down construction sequence at underground car park, Bristol .71
Figure 3.6
Bottom-up construction sequence . . . . . . . . . . . . . . . . . . . . . . . . . . .73
Figure 3.7
Bottom-up construction sequence, Copenhagen Metro . . . . . . . . . .74
Figure 3.8
Circular shaft under construction at Blackpool, Lancashire . . . . . . .75
Figure 3.9
Various support systems to sheet pile walls at Thelwall Viaduct,
Merseyside . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .75
Figure 3.10
Temporary props spanning full width of excavation for the
Mayfair car park, London . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .76
CIRIA C580
CIRIA C580
Figure 3.11
The use of a berm and raking props . . . . . . . . . . . . . . . . . . . . . . . . .77
Figure 3.12
Berm with raking props at Canary Wharf, London . . . . . . . . . . . . .77
Figure 3.13
The use of a berm and a prop to the permanent structure . . . . . . . .77
Figure 3.14
Berm with low-level permanent propping at Batheaston Bypass . . .78
Figure 3.15
Anchored contiguous bored pile wall . . . . . . . . . . . . . . . . . . . . . . . .78
Figure 3.16
Typical connection detail at sheet pile wall/concrete slab . . . . . . . .80
Figure 3.17
Sheet pile wall/concrete slab connection at Bristol underground
car park . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .81
Figure 3.18
Typical detail for couplers cast within a diaphragm wall panel . . . .81
Figure 3.19
Typical details of bent-out bars in diaphragm wall panel . . . . . . . . .81
Figure 3.20
Hinged slab: A406 North Circular Road, London . . . . . . . . . . . . . .82
Figure 3.21
Hinged joint: A406 North Circular Road, London . . . . . . . . . . . . . .82
Figure 4.1
Schematic stress history of an overconsolidated clay deposit
(σ′v against σ′h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .92
Figure 4.2
Rankine plastic equilibrium for a frictionless wall/soil interface
translating horizontally . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .94
Figure 4.3
Coulomb’s method to calculate limiting active force for a
frictionless wall/soil interface translating horizontally . . . . . . . . . . .95
Figure 4.4
Effect of wall friction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .96
Figure 4.5
Tension cracks: minimum total horizontal stress . . . . . . . . . . . . . .101
Figure 4.6
Additional lateral effective stress acting on the back of a wall
due to a strip load running parallel to it . . . . . . . . . . . . . . . . . . . . .102
Figure 4.7
Pressure diagram for a line load . . . . . . . . . . . . . . . . . . . . . . . . . . .103
Figure 4.8
Concentrated and line load surcharges . . . . . . . . . . . . . . . . . . . . . .104
Figure 4.9
Enhancement factor on passive earth pressure coefficient for
rough walls in close proximity . . . . . . . . . . . . . . . . . . . . . . . . . . . .105
Figure 4.10
Idealised stress distribution for an unpropped embedded cantilever
wall at failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .110
Figure 4.11
Approximate stress analysis for unpropped walls . . . . . . . . . . . . . .112
Figure 4.12
Normalised depths of embedment at failure . . . . . . . . . . . . . . . . . .113
Figure 4.13
Idealised stress distribution at failure for a stiff wall propped
rigidly at the top . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .114
Figure 4.14
“Fixed earth support” effective stress distributions and deformations
for an embedded wall propped at the top . . . . . . . . . . . . . . . . . . . .115
Figure 4.15
Stress analysis for an embedded wall propped at formation level .116
Figure 4.16
Forces acting on a stabilising base retaining wall . . . . . . . . . . . . . .117
Figure 4.17
King post wall design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .118
Figure 4.18
Reduction of lateral stress in the retained soil due to arching on
to a rigid prop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .120
Figure 4.19
Components of wall displacements and definition of a stiff wall . .121
Figure 4.20
Stress distributions behind and in front of stiff and flexible
embedded walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .122
Figure 4.21
Comparison of types of analyses: effective stress . . . . . . . . . . . . .128
Figure 4.22
Comparison of types of analyses: total stress . . . . . . . . . . . . . . . . .129
Figure 5.1
Determination and selection of parameters for use in design
calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .133
Figure 5.2
Decision-making process in site investigation . . . . . . . . . . . . . . . .139
9
10
Figure 5.3
Permeability and drainage characteristics of soils . . . . . . . . . . . . .145
Figure 5.4
Correlation between the in-situ coefficient of earth pressure and
overconsolidation ratio for clays of various plasticity indices . . . .148
Figure 5.5
Influence of stress history on Ko and σh′ in a heavily
overconsoldiated clay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .149
Figure 5.6
Influence of the ratio of sample size to the fissure spacing on the
strength measured in laboratory tests . . . . . . . . . . . . . . . . . . . . . . .152
Figure 5.7
Correlation between undrained shear strength and liquidity index 153
Figure 5.8
Correlation between N60 value and undrained shear strength and
plasticity index for insensitive clays . . . . . . . . . . . . . . . . . . . . . . . .154
Figure 5.9
Strength envelope for a given pre-consolidation . . . . . . . . . . . . . .155
Figure 5.10
Effect of overconsolidation on the relationship between (N1)60
and peak angle of friction φ′peak . . . . . . . . . . . . . . . . . . . . . . . . . . .157
Figure 5.11
Derivation of N′ from SPT blowcount N60 . . . . . . . . . . . . . . . . . . .158
Figure 5.12
Stiffness-strain behaviour of soil with typical strain ranges for
laboratory tests and structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . .159
Figure 5.13
Various steady-state seepage flownets . . . . . . . . . . . . . . . . . . . . . .163
Figure 5.14
Linear steady-state seepage in uniform ground and the effect of
excavation width . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .164
Figure 5.15
Design parameters – definition of terms . . . . . . . . . . . . . . . . . . . . .170
Figure 5.16
Temporary works design assumptions . . . . . . . . . . . . . . . . . . . . . .174
Figure 6.1
Design method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .184
Figure 6.2
Postulated failure mechanisms used to check toe stability . . . . . . .193
Figure 6.3
Determination of wall bending moments in SLS conditions from
limit equilibrium calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . .196
Figure 6.4
Design of sheet pile walls to EC3, Part 5 . . . . . . . . . . . . . . . . . . . .200
Figure 6.5
Pile cross-section showing crack width calculation principles to
BS 8110 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .204
Figure 6.6
Pile cross-section showing crack width calculation principles to
EC2 as applied on the Copenhagen Metro project . . . . . . . . . . . . .204
Figure 7.1
Propped steel sheet piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .207
Figure 7.2
Definition of berm geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .214
Figure 7.3
Representation of a berm as an equivalent surcharge . . . . . . . . . . .215
Figure 7.4
Representation of a berm by means of a raised effective
formation level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .215
Figure 7.5
Normalised wall top displacement at the centre of the
unsupported section against degree of discontinuity β for
different excavated bay lengths B . . . . . . . . . . . . . . . . . . . . . . . . . .217
Figure 7.6
Three-dimensional finite element mesh, wall and excavation
geometry and assumed soil parameters . . . . . . . . . . . . . . . . . . . . . .218
Figure 7.7
Relationship between berm height and effective uniform ground
level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .219
Figure 7.8
Passive anchor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .220
Figure 7.9
Sketch of a typical ground anchorage . . . . . . . . . . . . . . . . . . . . . . .220
Figure A1.1
Risk assessment – decision justification form . . . . . . . . . . . . . . . .250
Figure A1.2
Risk assessment – record of selection . . . . . . . . . . . . . . . . . . . . . . .251
Figure A1.3
Risk register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .252
CIRIA C580
CIRIA C580
Figure A2.1
Observed maximum lateral wall deflections for excavations in
London Clay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .263
Figure A2.2
Normalised maximum wall deflection versus system stiffness . . .264
Figure A2.3
Ground surface settlement contours at New Palace Yard, London .281
Figure A2.4
Plan of the Hai-Hua building . . . . . . . . . . . . . . . . . . . . . . . . . . . . .282
Figure A3.1
Frodingham sheet pile sections and properties . . . . . . . . . . . . . . . .285
Figure A3.2
Larssen sheet pile sections and properties . . . . . . . . . . . . . . . . . . .286
Figure A3.3
Sheet pile wall installation, Portsmouth Harbour . . . . . . . . . . . . . .287
Figure A3.4
High-modulus sheet piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .288
Figure A3.5
Contiguous pile wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .289
Figure A3.6
Contiguous bored pile wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .289
Figure A3.7
Hard/soft secant pile wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .290
Figure A3.8
Hard/soft secant pile wall as temporary works at North Greenwich
station, London . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .291
Figure A3.9
Hard/firm secant pile wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .291
Figure A3.10
Hard/hard secant pile wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .292
Figure A3.11
Hard/hard secant pile wall and an example of top-down
construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293
Figure A3.12
Diaphragm wall panel and joint . . . . . . . . . . . . . . . . . . . . . . . . . . .293
Figure A3.13
Diaphragm wall construction at Canary Wharf station, London . .294
Figure A4.1
Normal and shear stresses acting on an imaginary plane within
the cross-section plane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .299
Figure A4.2
Mohr circles of stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .299
Figure A4.3
Schematic stress history of an overconsolidated clay . . . . . . . . . . .302
Figure A4.4
Typical stress-strain data for a loose (lightly overconsolidated
or normally consolidated) soil and for dense (heavily
overconsolidated) soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .304
Figure A4.5
Critical state line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .305
Figure A4.6
Undrained state paths for clay samples having the same specific
volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .305
Figure A4.7
Ring shear test data for undisturbed London Clay . . . . . . . . . . . . .306
Figure A4.8
Normalised peak and critical state . . . . . . . . . . . . . . . . . . . . . . . . .307
Figure A4.9
Mohr circles representation of undrained shear strength failure
criterion in terms of total stresses for shearing at a constant specific
volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .308
Figure A4.10
Failure after dissipation of negative excess pore water pressures
induced on excavation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .309
Figure A4.11
Soil stiffness definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .310
Figure A5.1
Earth pressure coefficient profiles 1 m behind the centre of the
primary panel during construction of the wall: three-dimensional
analysis with 5 m panels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .314
Figure A5.2
Earth pressure coefficient profiles normal to the centre of the
primary panel following completion of the wall: three-dimensional
analysis with 5 m panels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .314
Figure A6.1
Active and passive earth pressure coefficients, (β / φ′) = -1 . . . . .318
Figure A6.2
Active and passive earth pressure coefficients, (β / φ′) = -0.75 . . .319
Figure A6.3
Active and passive earth pressure coefficients, (β / φ′) = -0.5 . . . .320
Figure A6.4
Active and passive earth pressure coefficients, (β / φ′) = -0.25 . . .321
11
12
Figure A6.5
Active and passive earth pressure coefficients, (β / φ′) = 0 . . . . . .322
Figure A6.6
Active and passive earth pressure coefficients, (β / φ′) = 0.25 . . . .323
Figure A6.7
Active and passive earth pressure coefficients, (β / φ′) = 0.5 . . . . .324
Figure A6.8
Active and passive earth pressure coefficients, (β / φ′) = 0.75 . . . .325
Figure A6.9
Active and passive earth pressure coefficients, (β / φ′) = 1 . . . . . .326
Figure A7.1
Methods of assessing the ratio of restoring moments to
overturning moments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .327
Figure A7.2
Wall geometry for general analysis case and range of variables . .329
Figure A7.3
Equivalent Fr, values for Fs = 1.2 . . . . . . . . . . . . . . . . . . . . . . . . . .331
Figure A7.4
Equivalent Fnp, values for Fs = 1.2 . . . . . . . . . . . . . . . . . . . . . . . . .332
Figure A7.5
Equivalent Fp, values for Fs = 1.2 . . . . . . . . . . . . . . . . . . . . . . . . . .333
Figure A9.1
Modified equilibrium analysis approach: multiple Coulomb
wedge analysis (undrained) in terms of total stresses for a
retaining wall supported by an earth berm . . . . . . . . . . . . . . . . . . .356
Figure A10.1
Example 1 – cantilever wall: effective stress analysis . . . . . . . . . .360
Figure A10.2
Example 2 – propped wall: effective stress analysis . . . . . . . . . . . .360
Figure A10.3
Example 3 – cantilever wall: total stress analysis . . . . . . . . . . . . . .361
Figure A10.4
Example 4 – propped wall: total stress analysis . . . . . . . . . . . . . . .361
Figure A10.5
Results for Example 1 – cantilever wall: effective stress analysis,
ULS calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .365
Figure A10.6
Results for Example 1 – cantilever wall: effective stress analysis,
SLS calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .366
Figure A10.7
Results for Example 2 – propped wall: effective stress analysis,
ULS calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .367
Figure A10.8
Results for Example 2 – propped wall: effective stress analysis,
SLS calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .368
Figure A10.9
Results for Example 3 – cantilever wall: total stress analysis,
ULS calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .369
Figure A10.10
Results for Example 3 – cantilever wall: total stress analysis,
SLS calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .370
Figure A10.11
Results for Example 4 – propped wall: total stress analysis,
ULS calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .371
Figure A10.12
Results for Example 4 – propped wall: total stress analysis,
SLS calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .372
Figure A10.13
Example 2 – singly propped wall: effective stress, ULS
calculations. Effects of groundwater pressures . . . . . . . . . . . . . . . .375
Figure A10.14
Example 2 – singly propped wall: effective stress, SLS
calculations. Effects of groundwater pressures . . . . . . . . . . . . . . . .376
Figure A11.1
Worked example geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .379
Figure A11.2
Top-down construction sequence . . . . . . . . . . . . . . . . . . . . . . . . . .381
Figure A11.3
Limiting wall friction and adhesion: wall supporting large
vertical loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .384
Figure A11.4
Calculated ULS and SLS wall bending moment envelopes . . . . . .385
Figure A11.5
Estimated ground surface settlement from computed SLS
FREW wall deflection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .387
Figure A11.6
Estimated ground surface settlement due to wall installation and
deflection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .388
CIRIA C580
List of tables
CIRIA C580
Table 2.1
Key performance considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38
Table 2.2
Ground surface movements due to bored pile and diaphragm wall
installation in stiff clay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50
Table 2.3
Support stiffness categories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54
Table 2.4
Ground surface movements due to excavation in front of bored pile,
diaphragm wall and sheet pile walls wholly embedded in stiff clays . . .54
Table 2.5
Classification of visible damage to walls . . . . . . . . . . . . . . . . . . . . . . . .63
Table 3.1
Cantilever wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70
Table 3.2
Top-down construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72
Table 3.3
Tolerances for top-down piles and plunged columns . . . . . . . . . . . . . . .73
Table 3.4
Bottom-up construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .74
Table 3.5
Ground anchorages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79
Table 3.6
Wall/slab connection types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .80
Table 3.7
Wall types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .84
Table 3.8
Typical applications of embedded retaining walls . . . . . . . . . . . . . . . . .85
Table 3.9
Relative costs to assist choice of wall . . . . . . . . . . . . . . . . . . . . . . . . . . .86
Table 3.10
Measures for dealing with obstructions . . . . . . . . . . . . . . . . . . . . . . . . .88
Table 3.11
Environmental issues throughout the life-cycle of the wall . . . . . . . . . .89
Table 4.1
Advantages and limitations of common methods of retaining wall
analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .109
Table 4.2
Values of Young’s modulus E and second moment of cross-sectional
area I for various embedded retaining wall types . . . . . . . . . . . . . . . . .125
Table 5.1
Soil parameters required for various calculation/analysis methods . . .135
Table 5.2
Typical ground investigation techniques used in stiff
overconsolidated soils to establish stratigraphy . . . . . . . . . . . . . . . . . .140
Table 5.3
Effect of fabric on soil properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . .141
Table 5.4
Publications giving typical properties for stiff clays commonly
encountered in the UK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .144
Table 5.5
Index properties to be determined . . . . . . . . . . . . . . . . . . . . . . . . . . . . .144
Table 5.6
Typical unit weight of soils and fills . . . . . . . . . . . . . . . . . . . . . . . . . . .145
Table 5.7
Comparison of common methods of permeability determination . . . .147
Table 5.8
Undrained shear strength of clays . . . . . . . . . . . . . . . . . . . . . . . . . . . . .154
Table 5.9
φ′crit for clay soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .156
Table 5.10
Values of A, B and C for siliceous sands and gravels . . . . . . . . . . . . . .158
Table 5.11
Highway live loading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .167
Table 5.12
Railway live loading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .167
Table 6.1
Fs factors appropriate for use in design calculations . . . . . . . . . . . . . . .185
Table 6.2
Corrosion rates for steel piling in natural environments . . . . . . . . . . . .198
Table 6.3
Allowable bending stresses for steel sheet piling . . . . . . . . . . . . . . . . .199
Table A2.1
Wall installation effects – case history data: Clough and
O’Rourke (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .255
Table A2.2
Wall installation effects – case history data: Thompson (1991) . . . . . .256
13
Table A2.3
Wall installation effects – case history data: Carder (1995) . . . . . . . . .258
Table A2.4
Wall installation effects – case history data: Carder et al (1997) . . . . .259
Table A2.5
Ground heave case studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .262
Table A2.6
Average δhmax values due to excavation in front of walls embedded
in stiff soil for data where δhmax < 0.3 per cent H . . . . . . . . . . . . . . . . .265
Table A2.7
Wall deflection effects – case history data: Clough and O’Rourke
(1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .266
Table A2.8
Wall deflection effects – case history data: Carder (1995) . . . . . . . . . .268
Table A2.9
Wall deflection effects – case history data: Fernie and Suckling (1996) 270
Table A2.10 Wall deflection effects – case history data: Carder et al (1997) . . . . . .272
Table A2.11 Wall deflection effects – case history data: Long (2001) . . . . . . . . . . .273
Table A3.1
Contiguous pile wall – typical diameters and spacing . . . . . . . . . . . . .289
Table A3.2
Hard/soft secant pile wall – typical diameters and spacing . . . . . . . . .290
Table A3.3
Hard/firm secant pile wall – typical diameters and spacing . . . . . . . . .292
Table A3.4
Hard/hard secant pile wall – typical diameters and spacing . . . . . . . . .292
Table A3.5
Diaphragm wall – typical panel widths . . . . . . . . . . . . . . . . . . . . . . . . .294
Table A7.1
Commonly adopted ULS factor values . . . . . . . . . . . . . . . . . . . . . . . . .328
Table A7.2
Summary of equivalent factors of safety . . . . . . . . . . . . . . . . . . . . . . .330
Table A8.1
Partial factors (γf and γm) – ultimate limit states in persistent and
transient situations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .341
Table A8.2
BD 42/00 (DMRB 2.1.2) recommended methods for determining a
stable wall geometry in stiff clays . . . . . . . . . . . . . . . . . . . . . . . . . . . . .346
Table A8.3
Partial factors γfl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .349
Table A8.4
Comparison of retaining wall design assumptioms and factors . . . . . .351
Table A10.1 Principal assumptions made in calculations . . . . . . . . . . . . . . . . . . . . .363
Table A11.1 Summary of ground parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .380
Table A11.2 Soil design parameters – ULS calculations . . . . . . . . . . . . . . . . . . . . . .382
Table A11.3 Soil design parameters – SLS calculations . . . . . . . . . . . . . . . . . . . . . .386
Table A11.4 ULS values of maximum wall bending moment and shear force . . . . .389
Table A11.5 SLS prop forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .390
Table A11.6 ULS prop forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .390
14
CIRIA C580
List of boxes
CIRIA C580
Box 2.1
Typical roles in embedded retaining wall design . . . . . . . . . . . . . . . . . . . .30
Box 2.2
Stress paths for soil elements near an excavation retained by a castin-situ embedded wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44
Box 2.3
Typical movement profiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52
Box 2.4
System stiffness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58
Box 2.5
Procedure for stage 2 damage category assessment . . . . . . . . . . . . . . . . . .64
Box 4.1
Theoretical depths of tension cracks by the Rankine and Coulomb
analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100
Box 4.2
Steps involved in a typical limit equilibrium analysis . . . . . . . . . . . . . . . .111
Box 4.3
Changing wall EI to allow for cracking, creep and relaxation of
concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .125
Box 5.1
Effect of groundwater pressure on retaining wall design . . . . . . . . . . . . .165
Box 5.2
Moderately conservative profile of undrained shear strength . . . . . . . . . .172
Box 6.1
The design method: sequential steps . . . . . . . . . . . . . . . . . . . . . . . . . . . . .186
Box 7.1
The distributed prop load design method . . . . . . . . . . . . . . . . . . . . . . . . .211
Box 7.2
Construction sequence analysed by Easton et al . . . . . . . . . . . . . . . . . . . .219
15
Glossary
16
analysis
The process of breaking down a design into its constituent
parts and of calculating the behaviour of each part.
client
An organisation or individual using the services of
construction professionals in order to invest in new
building or construction work.
conceptual design
The identification of an appropriate design solution by
qualitatively assessing the strengths and weaknesses of a
range of possible design variants, without recourse to
detailed analyses.
desk study
An examination of all existing information concerning a
site (eg geological maps, previous borehole records, aerial
photographs) to determine ground conditions and previous
land use.
engineering judgement
A feel for the appropriateness of a situation, from the
narrowest technical details to the broadest concepts of
planning.
geotechnical adviser
A chartered engineer or a chartered geologist with five
years of practice as a geotechnical specialist (Site
Investigation Steering Group, 1993).
geotechnical engineer
A chartered engineer with at least one year of postgraduate experience in geotechnics and a post-graduate
qualification in geotechnical engineering or engineering
geology, equivalent at least to an MSc, or a chartered
engineer with at least three years of post-graduate
experience in geotechnics (Site Investigation Steering
Group, 1993).
geotechnical risk
The risk posed to construction by the ground or
groundwater conditions at a site.
ground investigation
The sub-surface field investigation, with the associated
sampling, testing and factual reporting. See site
investigation.
ground model
A conceptual model based on the geology and
morphology of the site, and used to speculate on likely
ground and groundwater conditions and their variability.
hazard
An event, process or mechanism that could affect the
performance of an embedded retaining wall and prevent
performance objectives from being met.
likelihood
The probability that an event will occur.
CIRIA C580
mitigation
The limitation of the undesirable effects of a particular
event.
moderately conservative
A cautious estimate of soil parameters, loads and
geometry – worse than the probabilisitic mean but not as
severe as a worst credible parameter value. Sometimes
termed a conservative best estimate.
project manager
The individual or organisation responsible for managing a
project.
risk
The combination of the probability and consequences of a
hazard occurring.
risk assessment
A structured process of identifying hazards, their
probability and consequence of occurring, and their likely
impact on the performance of the retaining wall.
risk mitigation
Measures taken to either remove a hazard or to minimise
the likelihood or consequences of it occurring to an
acceptable level, including monitoring, and remedial action.
risk register
A list of risks arising from relevant hazards and the
benefits of mitigating them.
rupture surface
The detachment surface on which differential movement
occurs.
serviceability limit state
State of deformation of a retaining wall such that its use is
affected, its durability is impaired or its maintenance
requirements are substantially increased. Alternatively,
such movement that may affect any supported or adjacent
infrastructure, eg track, road or canal. See ultimate limit
state.
site investigation
The assessment of the site, including desk study, planning
and directing the ground investigation, and interpretation
of the factual report.
ultimate limit state
State of collapse, instability or forms of failure that may
endanger property or people or cause major economic
loss. See serviceability limit state.
worst credible
The worst value of soil parameters, loads and geometry
that the designer realistically believes might occur.
For further definitions and information, the reader is referred to technical dictionaries
including the Penguin dictionary of civil engineering (Scott, 1991) and the Dictionary
of geotechnical engineering (Somerville and Paul, 1983).
CIRIA C580
17
Abbreviations
18
CDM
Construction (Design and Management) Regulations 1994
DETR
Department of the Environment, Transport and Regions
DMRB
Design Manual for Roads and Bridges
FPS
Federation of Piling Specialists
HA
Highways Agency
ICE
Institution of Civil Engineers
LUL
London Underground Limited
DPL
distributed prop load
SISG
Site Investigation Steering Group
SLS
serviceability limit state
SPT
Standard Penetration Test
ULS
ultimate limit state
U100
102 mm-diameter driven tube sample
CIRIA C580
1
Introduction
An earth retaining wall is required to withstand forces exerted by a vertical or nearvertical ground surface. An embedded retaining wall is one that penetrates the ground at
its base and obtains some lateral support from it. The wall may also be supported by
structural members such as props, berms, ground anchors and slabs. It may be
freestanding or it may provide support to a superstructure.
This book provides guidance on the selection and design of vertical embedded retaining
walls. It covers all types of embedded walls; see Figure 1.1.
Figure 1.1
Wall types
It is possible to make economies in embedded retaining walls by selecting an appropriate
wall type and support system for the envisaged construction sequence and long-term
use. It is important to adopt a clear, unambiguous design method and to follow best
practice in ground investigation, laboratory and field-testing, design analysis and the
use of good-quality case history data. This book provides guidance on all these points.
1.1
BACKGROUND TO PROJECT
CIRIA Report 104 (Padfield and Mair, 1984) Design of retaining walls embedded in
stiff clay has been hugely influential. Although strictly applicable to the design of
single-propped or cantilever walls embedded in stiff overconsolidated clay, the
principles presented in the book have been applied to a wide range of wall types and
soils in the UK and overseas, including multi-propped embedded walls and even nonembedded walls. It has also formed the model for other documents providing design
guidance such as the recently published BD 42/00 Design of embedded retaining walls
and bridge abutments (Design Manual for Roads and Bridges, DMRB 2.1.2).
CIRIA C580
19
Since CIRIA Report 104 was published, several retaining wall design guidance
documents and codes of practice relevant to embedded walls have been issued, most
notably:
z
BS 8002 (1994) Code of practice for earth retaining structures. The latest
amendment to this code was issued in September 2001
z
DD ENV 1997-1 Eurocode 7 (1995) Geotechnical design. Part 1 General rules.
This document is being revised
z
BD 42/00 (Design Manual for Roads and Bridges, DMRB 2.1.2) Design of
embedded retaining walls and bridge abutments
z
British Steel (1997) Piling handbook 7th edition
z
Hong Kong Government (1994) Geoguide 1, Guide to retaining wall design
z
Nicholson et al (1999) The Observational Method in ground engineering –
principles and applications (CIRIA R185)
z
Twine and Roscoe (1999) Temporary propping of deep excavations – guidance on
design (CIRIA C517)
z
Williams and Waite (1993) The design and construction of sheet piled cofferdams
(CIRIA SP95).
In addition to the above, many technical papers and textbooks have been published.
The above documents do not provide consistent and harmonious design advice, and
many omit detailed treatment of modern numerical analysis methods. The multiplicity
of documents, and the varied guidance they offer, results in confusion (which is costly
to designers) and poor economy in construction (which is costly to constructors and
clients). There is therefore a need for a coherent and authoritative publication that
collates the best ideas and experiences available in British practice and provides a clear
path through the many alternative design approaches. That is the aim of this book.
CIRIA commissioned the research in November 2000. Ove Arup & Partners Ltd
undertook the project with assistance from the University of Southampton and Bachy
Soletanche Limited. The steering group that guided the work represented clients,
consultants, contractors and academic institutions. The authors consulted widely via a
questionnaire, consultation workshop and literature searches.
1.2
OBJECTIVES
This book provides guidance on the design of embedded retaining walls. Following the
guidance should enable users to achieve economy in the resulting retaining structure
and its support system while maintaining simplicity, so far as possible, but also
facilitating more complex approaches where they give an advantage.
The book:
z
offers best practice guidance for the design of embedded retaining walls consistent
with recent research and current analytical techniques
z
describes and compares existing design methods for such walls
z
discusses available wall types and construction methods
z
provides construction costs data to guide the reader in selecting wall types
appropriate to particular requirements.
This publication supersedes CIRIA Report 104 (Padfield and Mair, 1984).
20
CIRIA C580
1.3
READERSHIP
CIRIA C580 is intended for use by those concerned with the selection, design and
construction of embedded retaining walls. In addition to providing guidance to
designers, the book also:
1.4
z
gives background information on wall selection, construction methods and
associated ground movements for clients and owners and their technical advisers
z
presents geotechnical principles and guidance to structural and geotechnical
engineers and to students who wish to gain an appreciation of the issues relevant to
the selection, design and construction of an embedded retaining wall
z
acts as a reference for more experienced geotechnical engineers.
APPLICABILITY
See also
2.2.2
Geotechnical
characterisation of
retaining walls
CIRIA C580 covers the design of temporary and permanent cantilever, anchored,
single- and multi-propped retaining walls supported by embedment in stiff clay and
other competent soils. The book’s principles are applicable to a wide range of finegrained and coarse-grained soils in the UK and overseas. The design of walls embedded
in soft clay and those socketed into rock is beyond the scope of this publication.
Typical British soils to which this book is applicable include London Clay, Oxford
Clay, Gault Clay, Lias Clay, Atherfield Clay, Weald Clay, Barton Clay, Kimmeridge
Clay, Lambeth Beds, Mercia Mudstone, and glacial tills. These soils have experienced
high overburden pressures in their geological history, which have caused them to
consolidate to a dense state. Subsequent erosion of the upper soil horizons, or the removal
of Quaternary ice cover, has resulted in significant unloading and swelling. These soils
typically exhibit in situ moisture contents that are lower than they would have been if
no overconsolidation had occurred. This geological history results in soils that:
z
may be fissured
z
have an in situ earth pressure coefficient, Ko, that is greater than unity
z
have an undrained shear strength that is significantly greater than that of a normally
consolidated soil at similar depth
z
exhibit a peak shear strength at low strains and reduced shear strength at high strains.
Few walls are constructed entirely in stiff overconsolidated fine-grained soils. Although
the wall may be embedded in such soils, it is likely that it will also retain other soils,
such as made ground, river gravels and other alluvial deposits. The principles presented
in this book also apply to this common situation.
The authors have adopted the geotechnical categorisation proposed by EC7 (1995). It
applies to the design of embedded retaining walls for geotechnical categories 1 (small
and relatively simple structures) and 2 (conventional types of structures with no
abnormal risks or unusual or exceptionally difficult ground or loading conditions). It
does not specifically address the design requirements of walls for geotechnical category
3 (very large or unusual structures, structures involving abnormal risks, or unusual or
exceptionally difficult ground or loading conditions and structures in highly seismic
areas), although the general principles presented in this book will also apply to these
structures. Geotechnical categories are defined and discussed in Section 2.2.2.
Ground engineering requires a thorough knowledge and understanding of basic
principles and the application of sound engineering judgement based on
experience. This book is not a substitute for professional knowledge. If in doubt,
seek appropriate advice.
CIRIA C580
21
1.5
ECONOMIC DESIGN
See also
A10
Effect of method of
analysis
2.1.3
Risk assessment
and management
2.2.2
Geotechnical
categorisation of
retaining walls
3
Construction
considerations and
wall selection
4.3
Effect of method of
analysis
5.9.1
Temporary works
design
6
Design of wall
6.6.3
Steel sheet pile walls
Economy can be achieved by:
z
ensuring ease of construction and minimising construction duration
z
optimising the use of materials
z
applying appropriate design effort.
The biggest economies will be available at the outset of a project during the
selection of an appropriate method and sequence of construction, wall type and
the optimisation of the temporary and permanent use of the retaining structure.
Achieving economy requires commitment and adherence to an approach that
necessitates a holistic view to be taken of project requirements. Whole-life costs
should be considered. A robust design that minimises long-term maintenance
requirements may be appropriate in some circumstances. A design that minimises wall
dimensions and material use but increases construction duration because it is difficult to
build may not result in overall economy. The designer alone cannot achieve the most
cost-effective solution in isolation from the client and the constructor.
The client, designer and constructor and, where appropriate, the architect and the
quantity surveyor, should be involved as early as possible to:
z
optimise the temporary and permanent use of the retaining structure (such as
adopting one wall instead of two to serve both the temporary and permanent
requirements) that is also compatible with long-term maintenance requirements
z
establish appropriate design and performance criteria for the retaining structure,
such as acceptable limits for wall deflection and associated ground movements,
crack width criteria
z
consider appropriate wall type
z
consider appropriate method and sequence of construction to ensure buildability
with minimum construction duration.
Initial ideas should be reviewed and alternatives explored before agreeing the preferred
solution. It is important to involve individuals with appropriate qualifications and
experience at all stages of the project and to maintain adequate continuity and
communication between the personnel involved in data collection, design and
construction. The involvement of the constructor at an early stage should minimise
wasteful abortive work arising from design changes.
Where the design of a wall is governed by temporary works considerations, a riskbased approach to design may lead to significant savings. Using the Observational
Method may result in the most cost effective design solution for temporary and
permanent works (Section 5.9.1). However, in this circumstance, appropriate
contractual arrangements should be in place to permit the necessary integrated
interactive approach to be taken on site between design and construction.
A clear, unambiguous design method that eliminates confusion will avoid
unnecessary design effort. The choice of analysis method can result in significant
savings in the wall structure. For example, propped or anchored walls designed using
soil-structure interaction methods will be shorter, and computed wall bending moments
will be smaller, than those designed using limit equilibrium methods (Section 4.3).
Also, savings in material use of about 25–30 per cent are possible if plastic design is
applied to sheet pile walls (Section 6.6.3). In the UK, it may not be possible to realise
such savings, as it is often necessary to adopt sheet pile sections that are of greater
thickness than those determined from the analysis of the section in service in order to
22
CIRIA C580
withstand the driving forces. Procedures for higher wall categories can be used to
justify more economic design. For example, the design of walls to geotechnical
category 2 can be used to justify a more economic design for structures that would
otherwise be classified as category 1. The higher investigation and design costs of a
geotechnical category 2 wall should be balanced against the potential savings in
materials and construction over a category 1 design.
1.6
BOOK LAYOUT
Figure 1.2 shows the principal design stages and the corresponding sections of this
book. For readers needing guidance on specific issues, Figure 1.3 provides a map of the
sections discussing key issues.
Figure 1.2
CIRIA C580
Principal design stages and book layout
23
Figure 1.3
24
Key issues considered in the book
CIRIA C580
Cross-references guide users between related subjects in different sections. Details are
presented in boxes, separately from the main text. Appendices provide background
information, a commentary on current practices and a list of case history data.
The book is organised into eight largely self-contained chapters. In view of the
anticipated wide readership (Section 1.3), the beginning of each chapter outlines the
target readership likely to gain most from the content of that chapter. Key points of
guidance and recommendations are highlighted in bold within the main text and appear
again at the end of the relevant chapter.
Chapter 1 sets out the objectives of the book and its applicability.
Chapters 2 and 3 help the reader select the appropriate wall type and construction
sequence. Some of the issues covered in these chapters are interrelated.
Chapter 2 provides guidance on the determination of the key wall design criteria, health
and safety issues, risk assessment and management, site-specific constraints and
project-specific requirements. Guidance is also provided on the estimation and effects
of ground movements associated with wall installation and performance.
Chapter 3 reviews wall types and available construction sequences. The advantages and
limitations of different construction sequences and wall types are compared and
guidance is provided on the selection of the most appropriate sequence and wall type to
satisfy particular site and project requirements. This chapter also presents construction
cost data relating to wall types and construction methods.
Chapter 4 presents key principles of soil behaviour relevant to embedded retaining
walls and the determination of earth pressures. Soil-structure interaction and methods
for its analytical modelling are also discussed.
Chapter 5 provides guidance on the determination and selection of parameters for use in
design calculations. Advice on the assessment of drained or undrained ground
behaviour is given together with guidance on the selection of parameters appropriate for
temporary works and permanent works design.
Chapter 6 offers best practice guidance on the geotechnical and structural design of the
wall.
Chapter 7 presents best practice guidance on the design of propping systems, berms and
anchors for lateral support to the wall.
Chapter 8 identifies areas of further work and research.
CIRIA C580
25
26
CIRIA C580