Allan Hodgkinson M.Eng., C.Eng., F.I.C.E., F.I.Strud.E., M.Cons.E.

Foundation Design

The Architectural Press: London

First publishcd in 1986 by the Architectural Press Ltd, 9 Queen Annes Gate, London S W l H 9 BY

Allan Hodgkinson, 1986

All rights reserved. No part of this book may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, for publication purposes, without the prior permission of the publisher. Such permission, if granted, is subject to a fee, depending on the nature of the use.

BRITISH LIBRARY CATALOGUING I N PUBLICATION DATA

Hodgkinson, Allan Foundation design. 1 .Foundations - Handbooks, manuals, etc. I.Title 624.15 TA775

ISBN 0-85 139-837-5

Typeset by Stratatype in Baskerville on Linotron 202

Printed and bound in Great Britain by Biddles Ltd, Guildford and Kings Lynn

Preface 7

1 Introduction to Rocks and Soils 9

2 15

3 Foundation Types 33

4 Foundation Hazards and Construction Problems 53

5 Underpinning 81

6 Examples of Foundation Design 87

7 Specifications 115

8 Site Supervision 121

Preferred Reading 123

Index 125

Site investigation, Soil and the Principal of Foundation Design

Contents

Structural engineering design is aided by appropriate sampling of materials of construction both before and after completion of the structure. The development of soil mechanics in the last fifty years has added greatly to the knowledge of the behaviour of soils, particularly clay. Soils are not so regular as construction materials and sampling is less frequent, so that greater judgement and experience are required of the designer of foundations. As with the author's previous work, the AJ Handbook of Building Structure, the emphasis is on practical matters and, while every architect may not aspire to more complicated designs, with the aid of this book he will be able to talk with more authority to his engineer. At the time of writing the book there was considerable controversy in the philosophy of design, the trend being from allowable stress to limit state. It is the author's belief that any method of design which satisfies the Building Regulations should be acceptable and that to decide by law that there should be only one method of design is a totally unwarranted and retrograde step. Fortunately, no method has yet been devised by which partial factors for material can be applied in foundation or retaining wall design. The book is therefore based on the accepted practices of the last eighty years.

I am grateful to the following for permission to reproduce illustrations and tables: Bartholomew, Fig. 1.1; Building Research Establishment, Tables 4.1, 4.2, Fig. 4.6; GKN-Keller, Fig. 4.31, 4.32, 4.37, 4.39; Piggot Foundations - Ground Engineering, Fig. 3.33; Wembley Laboratories, Figs. 2.3, 2.4, 2.5, 2.8, 2.10, 2.12; Henry Boot Civil Engineering, Fig. 1.4; British Standards Institu- tion, Tables 1.1, 1.2, 1.3; Institution of Structural Engineers, Fig. 2.5; Fairbriar Homes Ltd, Fig. 3.3. I am particularly grateful to my wife, who patiently typed the manuscript, and to Terry Roberts, who drew all the line illustrations.

Preface