Table Of ContentGroundwater Lowering in
Construction
A practical guide
P. M. Cashman and M. Preene
London and New York
First published 2001 by Spon Press
11 New Fetter Lane,London EC4P 4EE
Simultaneously published in the USA and Canada
by Spon Press
29 West 35th Street,New York,NY 10001
This edition published in the Taylor & Francis e-Library, 2002.
Spon Press is an imprint of the Taylor & Francis Group
© 2001 Spon Press
The right of Spon Press to be identified as the Author of this Work has been
asserted by them in accordance with the Copyright,Designs and Patents Act
1988
All rights reserved.No part of this book may be reprinted or reproduced or
utilised in any form or by any electronic,mechanical,or other means,now
known or hereafter invented,including photocopying and recording,or in
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The publisher makes no representation,express or implied,with regard to
the accuracy of the information contained in this book and cannot accept any
legal responsibility or liability for any errors or omissions that may be made.
British Library Cataloguing in Publication Data
A catalogue record for this book is available from the British Library
Library of Congress Cataloging in Publication Data
Cashman,P.M.(Pat M.)
Groundwater lowering in construction:a practical guide/P.M.
Cashman and M.Preene
p.cm.
Includes bibliographical references and index.
ISBN 0-419-21110-1 (alk.paper)
1. Earthwork.2. Drainage.3. Building sites.4. Groundwater flow.
I.Preene,M.(Martin) II.Title.
TA715.C35 2001
624.1’5–dc21 2001032252
ISBN 0-419-21110-1(Print edition)
ISBN 0-203-47632-8 Master e-book ISBN
ISBN 0-203-78456-1 (Adobe eReader Format)
Copyright © 2001 Spon Press
This book is dedicated to the memory of Pat Cashman and Mick
Falkingham,men who put groundwater lowering into practice
Copyright © 2001 Spon Press
Patrick Michael Cashman
Pat Cashman, the leading British exponent of groundwater control of his
generation, died on 25th June 1996. For more than forty years, during the
growth of soil mechanics into the practice of geotechnical engineering, Pat
was responsible, through the organizations he ran and later as a consultant,
for maintaining a practical and straightforward approach to the art of
groundwater control. This book, the manuscript of which was well
advanced at the time of his death, sets out that approach.
Following war service with the Royal Engineers, Pat Cashman graduated
from the University of Birmingham, and joined Soil Mechanics Limited,
soon transferring to the Groundwater Lowering Department, so beginning
his lifelong interest in this field. He became head of the department in 1961
and later became responsible for the joint venture with Soletanche which
introduced French techniques into the United Kingdom (UK). In 1969 he
became contracts director for Soletanche (UK) Limited.
In 1972 Pat joined Groundwater Services Limited (later Sykes
Construction Services Limited) as Managing Director. Over a ten year
period he designed and managed a huge number and range of groundwater
lowering projects. Commercial and financial success was achieved alongside
technical innovation and practical advancements. In the 1980s he joined
Stang Wimpey Dewatering Limited as Managing Director. Again he
achieved commercial success as well as introducing American ideas into
British practice. During this period Pat made a major contribution to the
production of CIRIA Report 113 Control of Groundwater for Temporary
Works– the first comprehensive dewatering guide produced in the UK in the
modern era.
In 1986 he ‘retired’ and commenced an active role as a consultant, often
working closely with Ground Water Control Limited, a contracting com-
pany formed by men who had worked for Pat during the Sykes years. His
practical approach to problems meant that he was always in demand, par-
ticularly by contractors when they were in trouble. Although a practical
man with a healthy suspicion of arcane theory and in particular computer
modelling of problems, he took to the computer to document his own expe-
rience. This book is record of a singular approach to a challenging business.
Copyright © 2001 Spon Press Martin Preene
Contents
List of figures
List of tables
Acknowledgements
1 Groundwater lowering: A personal view and
introduction by P. M. Cashman
2 The history of groundwater theory and practice
2.0 Introduction
2.1 The earliest times to the sixteenth century
2.2 The renaissance period to the nineteenth century
2.3 Progress from a qualitative to a quantitative
science
2.4 Later theoretical developments
2.5 Groundwater modelling
2.6 Early dewatering tec nology in Britain
2.7 Practical publication
References
3 Groundwater and permeability
3.0Introduction
3.1Hydrology and hydrogeology
3.2Permeability and groundwater flo
3.3Aquifers, aquitards and aquicludes
3.4Flow to wells
3.5Aquifers and geological structure
3.6Aquifer boundaries
3.7Using geological structure to advantage
3.8Groundwater chemistry
References
Copyright © 2001 Spon Press
viii Contents
4Groundwater effects on the stability of excavations
4.0Introduction
4.1Groundwater control – the objectives
4.2Groundwater, effective stress and instability
4.3Large-scale instability caused by groundwater
4.4Localized groundwater problems
4.5Excavations in rock
4.6Surface water problems
4.7Effect of climate and weather
References
5 Methods for control of surface water
and groundwater
5.0Introduction
5.1Control of surface water
5.2Methods of groundwater control
5.3Exclusion methods
5.4Dewatering methods
5.5Groundwater control for tunnels and shafts
References
Further reading – exclusion methods
6Site investigation for groundwater lowering
6.0Introduction
6.1The purpose of site investigation
6.2Planning of site investigations
6.3Stages of site investigation
6.4Determination of ground profile
6.5Determination of groundwater conditions
6.6Determination of permeability
Appendix 6A
Appendix 6B
Appendix 6C
References
7Design of groundwater lowering systems
7.0Introduction
7.1Design approach
7.2Development of conceptual model
Copyright © 2001 Spon Press
Contents ix
7.3Selection of method and geo
7.4Estimation of steady-state dische flow rate
7.5Specification of well yield and spacing
7.6Other considerations
7.7Numerical modelling
7.8Design examples
Appendix 7A
References
8Sump pumping
8.0Introduction
8.1Applications of sump pumping
8.2Surface water run-off
8.3Pumping sumps
8.4Drainage of side slopes of an excavation
8.5Sump pumping of small excavations
8.6Sump pumping problems
8.7Case history: sump pumping of large excavation
References
9Wellpoint systems
9.0Introduction
9.1Which system: wellpoints or deep wells?
9.2What is a wellpoint system?
9.3Wellpoint installation techniques
9.4Spacing of wellpoints and drawdown times
9.5Sealed vacuum wellpoint system
9.6Wellpoint pumping equipment
9.7Wellpoint installations for trench excavations
9.8Wellpointing for wide excavations
9.9Wellpointing for deeper excavations
9.10 Case history: Derwent outlet channel,
Northumberland
References
10Deep well systems
10.0Introduction
10.1Deep well installations
10.2Design of wells for groundwater lowering
10.3Constructing deep wells
Copyright © 2001 Spon Press
x Contents
10.4Drilling of well borehole
10.5Installation of well materials
10.6Well development
10.7 Installation and operation of deep
well pumps
10.8Vacuum deep well installations
10.9Shallow well installations
10.10 Case history: Tees Barrage,
Stockton-on-Tees
References
11Other dewatering systems
11.0Introduction
11.1Ejectors
11.2Horizontal wellpoints
11.3Pressure relief wells
11.4Collector wells
11.5Electro-osmosis
11.6 Use of dewatering and exclusion
in combination
References
12Pumps for groundwater lowering duties
12.0Introduction
12.1Units for wellpoint pumping
12.2Jetting pumps
12.3Units for sump pumping
12.4Pumps for deep wells
12.5Sizing of pumps and pipework
References
13Side effects of groundwater lowering
13.0Introduction
13.1Settlement due to groundwater lowering
13.2Effect on groundwater supplies
13.3Effect on groundwater quality
13.4 The impact of discharge flows on the surface
water environment
13.5Other effects
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Contents xi
13.6Artificial recharge systems
References
14 Monitoring and maintenance of groundwater
lowering systems
14.0Introduction
14.1The need for monitoring
14.2Monitoring of water levels
14.3Monitoring of discharge flow rate
14.4Other parameters that may be monitored
14.5Datalogging systems
14.6Mechanical factors and automation
14.7Backfilling and sealing of wells on completion
14.8Encrustation, biofouling and corrosion
14.9Fault finding and problem solving
Appendix 14A
References
15Safety, contracts and the environment
15.0Introduction
15.1Health and safety
15.2Contracts for groundwater control works
15.3Environmental regulation of groundwater control
References
16The future by T. O. L. Roberts
16.0Introduction
16.1Techniques
16.2Impact of information technology systems
16.3Regulation
16.4Conclusion
References
Notation
Glossary
Conversion factors
Copyright © 2001 Spon Press
Figures
2.1 Rag and chain pump, manually operated
2.2 Pumps for draining the Kilsby tunnel
2.3 Sewer diversion under gas main using wellpoints
and chemical injections
2.4 Early application of deep wells in Britain
3.1 The hydrological cycle
3.2 Darcy’s experiment
3.3 Definition of hydraulic head
3.4 Soil structure and permeability
3.5 Particle size distribution
3.6 Unconfined aquifer
3.7 Groundwater conditions above the water table
3.8 Confined aquifer
3.9 Flowing artesian conditions
3.10 Leaky aquifer system
3.11 Principal components of a groundwater
lowering well
3.12 Zone of influence
3.13 Well losses
3.14 Superposition of drawdown
3.15 Chalk aquifer beneath London
3.16 Groundwater control in multiple aquifers
3.17 Use of simple relief wells to maintain base stability
3.18 Interaction between rivers and aquifers
3.19 Interaction between aquifers
3.20 Potential aquifer recharge boundaries
3.21 Potential aquifer barrier boundaries
3.22 Potential aquifer discharge boundaries
4.1 Instability due to seepage into an excavation in an
unconfined aquifer
Copyright © 2001 Spon Press
