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Pile Design and Construction

Practice

Pile Design and Construction

Practice

Fifth edition

Michael Tomlinson and

John Woodward

First published 1977, reprinted with amendments 1981, third edition 1987 by Palladian, reprinted 1991, fourth edition 1994, reprinted 1994, 1995, 1998 by E & FN Spon Fifth Edition published 2008 by Taylor & Francis 2 Park Square, Milton Park, Abingdon, Oxon OX14 4RN Simultaneously published in the USA and Canada by Taylor & Francis 270 Madison Ave, New York, NY 10016

Taylor & Francis is an imprint of the Taylor & Francis Group, an informa business © 1977, 1987, 1994, 2008 Michael Tomlinson and John Woodward 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 any information storage or retrieval system, without permission in writing from the publishers. 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 efforts 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 Tomlinson, M. J. (Michael John) Pile design and construction practice / Michael Tomlinson and John Woodward. – 5th ed. p. cm. Includes bibliographical references and index.

1. Piling (Civil engineering) I. Woodward, John, 1936– II. Title. TA780.T65 2007 624.1'54–dc22 2006019427

ISBN10: 0–415–38582–2 (hbk) ISBN10: 0–203–96429–2 (ebk) ISBN13: 978–0–415–38582–4 (hbk) ISBN13: 978–0–203–96429–3 (ebk)

This edition published in the Taylor & Francis e-Library, 2007.

“To purchase your own copy of this or any of Taylor & Francis or Routledge’s collection of thousands of eBooks please go to www.eBookstore.tandf.co.uk.”

ISBN 0-203-96429-2 Master e-book ISBN

Piling rigs are a commonplace feature on building sites in cities and towns today. The continuing introduction of new, more powerful, and self-erecting machines for installing piled foundations has transformed the economics of this form of construction in ground conditions where, in the past, first consideration would have been given to conventional spread or raft foundations, with piling being adopted only as a last resort in difficult ground. The increased adoption of piling is not only due to the availability of more efficient mechanical equipment. Developments in analytical methods of calculating bearing capacity and dynamic methods for load and integrity testing have resulted in greater assurance of sound long-term performance. Further economies in foundation and superstructure design are now possible because of the increased ability to predict movements of piles under load, thus allowing engineers to adopt with confidence the concept of redistribution of load between piles with consequent savings in overall pile lengths and cross-sectional dimensions, as described in this new edition. Since the publication of the fourth edition of this book, Eurocode 7, Geotechnical Design, has been issued. As the name implies this code does not deal with all aspects of foundation design; there are extensive cross-references to other Eurocodes dealing with such matters as the general basis of design and the properties of constructional materials. The Code does not cover foundation design and particularly construction as comprehensively as the present British Standard 8004 Foundations, and the British National Annex to Eurocode 7 is yet to be published. The authors have endeavoured to co-ordinate the principles of both codes in this new book. The authors are grateful to Professor Richard Jardine and his colleagues at Imperial College and Thomas Telford Limited for permission to quote from their book on the ICP method of designing piles driven into clays and sands based on extensive laboratory research and practical field testing of instrumented piles. Their work represents a considerable advance on previous design methods. The authors also gratefully acknowledge the help of Mr Ian Higginbottom in checking the proofs and Mr Tony Bracegirdle of the Geotechnical Consulting Group for his helpful comments on the application of Eurocode 7 to the design of piles and pile groups. Many specialist piling companies and manufacturers of piling equipment have kindly supplied technical information and illustrations of their processes and products. Where appropriate the source of this information is given in the text.

Preface to fifth edition

In addition, the authors wish to thank the following for the supply of and permission to

Building Research Establishment Figure 10.2a and b Institution of Civil Engineers / Thomas Figures 4.28, 5.26, 5.27, 5.33,

• 1 General principles and practices Preface to first edition xiii
  • 1.1 Function of piles
  • 1.2 Historical
  • 1.3 Calculations of load-carrying capacity
  • 1.4 Dynamic piling formulae
  • 1.5 Code of practice requirements
  • 1.6 Responsibilities of engineer and contractor
  • 1.7 References
• 2 Types of pile
  • 2.1 Classification of piles
  • 2.2 Driven displacement piles
  • 2.3 Driven and cast-in-place displacement piles
  • 2.4 Replacement piles
  • 2.5 Composite piles
  • 2.6 Minipiles and micropiles
  • 2.7 Factors governing choice of type of pile
  • 2.8 Reuse of existing piled foundations
  • 2.9 References
• 3 Piling equipment and methods
  • 3.1 Equipment for driven piles
    • 3.2 Equipment for installing driven and cast-in-place piles
    • 3.3 Equipment for installing bored and cast-in-place piles
    • 3.4 Procedure in pile installation
    • 3.5 Constructing piles in groups
    • 3.6 References
• 4 Calculating the resistance of piles to compressive loads
  • 4.1 General considerations
  • 4.2 Calculations for piles in fine-grained soils
  • 4.3 Piles in coarse-grained soils
  • 4.4 Piles in soils intermediate between sands and clays
  • 4.5 Piles in layered fine- and coarse-grained soils - for piles in soil 4.6 The settlement of the single pile at the working load
  • 4.7 Piles bearing on rock
  • 4.8 Piles in fill – negative skin friction
  • 4.9 References
  • 4.10 Worked examples
• 5 Pile groups under compressive loading
  • 5.1 Group action in piled foundations
  • 5.2 Pile groups in fine-grained soils
  • 5.3 Pile groups in coarse-grained soils
  • 5.4 Eurocode 7 recommendations for pile groups
  • 5.5 Pile groups terminating in rock
  • 5.6 Pile groups in filled ground
  • 5.7 Effects on pile groups of installation methods
  • 5.8 Precautions against heave effects in pile groups
  • 5.9 Pile groups beneath basements - differential settlements in clay 5.10 The optimization of pile groups to reduce
  • 5.11 References
  • 5.12 Worked examples
    • uplift and lateral loading 6 The design of piled foundations to resist
  • 6.1 The occurrence of uplift and lateral loading
  • 6.2 Uplift resistance of piles
  • 6.3 Single vertical piles subjected to lateral loads
  • 6.4 Lateral loads on raking piles
  • 6.5 Lateral loads on groups of piles
  • 6.6 References
  • 6.7 Worked examples
    • piles and pile groups 7 Some aspects of the structural design of
  • 7.1 General design requirements
  • 7.2 Designing reinforced concrete piles for lifting after fabrication
    • 7.3 Designing piles to resist driving stresses
    • 7.4 The effects on bending of piles below ground level
    • 7.5 The design of axially loaded piles as columns
    • 7.6 Lengthening piles
    • 7.7 Bonding piles with caps and ground beams
    • 7.8 The design of pile caps
    • 7.9 The design of pile capping beams and connecting ground beams
    • 7.10 References
  • 8 Piling for marine structures - 8.1 Berthing structures and jetties
    • 8.2 Fixed offshore platforms
    • 8.3 Pile installations for marine structures
    • 8.4 References
    • 8.5 Worked examples
  • 9 Miscellaneous piling problems
    • 9.1 Piling for machinery foundations
    • 9.2 Piling for underpinning
    • 9.3 Piling in mining subsidence areas
    • 9.4 Piling in frozen ground
    • 9.5 Piled foundations for bridges on land
    • 9.6 Piled foundations for over-water bridges
    • 9.7 Piled foundations in karst
    • 9.8 Energy piles
    • 9.9 References
    • 9.10 Worked example
• 10 The durability of piled foundations - 10.1 General - 10.2 Durability and protection of timber piles - 10.3 Durability and protection of concrete piles - 10.4 Durability and protection of steel piles - 10.5 References
• 11 Ground investigations, piling contracts, pile testing - 11.1 Ground investigations - 11.2 Piling contracts and specifications - 11.3 Control of pile installation - 11.4 Load testing of piles - 11.5 Tests for the structural integrity of piles - 11.6 References
• Appendix: properties of materials
  • A.1 Coarse-grained soils
  • A.2 Fine-grained and organic soils
  • A.3 Rocks and other materials
  • A.4 Engineering classification of chalk
    • Name index
    • Subject index
• Abbey Pynford Foundation Systems Limited Figure 2. use photographs and illustrations from technical publications and brochures.
• ABI GmbH Figures 3.1 and 3. - 5.17, 5.30 and 6. American Society of Civil Engineers Figures 4.6, 4.11, 4.12, 4.29, 4.39,
• Austrian Member Society, SMGE Figure 6.
• Ballast Nedam Groep N.V. Figures 9.22 and 9. Bachy-Soletanche Figure 2.29a and b
• Bauer Maschinen GmbH Figure 3.
• The British Petroleum Company Limited Figure 8.
• BSP International Foundations Limited Figures 3.12 and 3. - 5.38 and 6. Canadian Geotechnical Journal Figures 4.34, 4.36, 4.37, 5.20,
• A. Carter Figure 9.
• Cement and Concrete Association Figure 7.
• Cementation Foundations Skanska Limited Figures 3.30, 3.33, 9.31 and 11.
• Central Electricity Generating Board Figure 2.
• CIRIA/Butterworth Figures 4.11 and 5.
• Comité Français SMGE Figure 6.
• Construction Industry Research and Figure 4.
• Danish Geotechnical Institute Figures 5.6–5.10, 6.21 and 6. Information Association (CIRIA)
• Dar-al-Handasah Consultants Figure 9.
• Dawson Construction Plant Limited Figure 3.
• Department of the Environment Figure 10.
• DFP Foundation Products Figure 2.
• Fondedile Foundations Limited Figure 9.
• Frank’s Casing Crew and Rental Inc Figure 2.
• Fugro Limited Figure 5.
• GeoDelft Figure 5.
• The Geological Society Figure 8.
• U G de Gijt Figure 4.
• International Construction Equipment Figure 3.
  • and Foundation Engineering 6.30 and 9. International Society for Soil Mechanics Figures 3.38, 5.24, 5.25, 6.18,
    • 9.26 and 9. Telford Limited 5.34, 5.35, 5.41, 5.42, 9.21, 9.24,
• Land and Water, Den Haag Figure 4.
• Liebherr Great Britain Limited Figure 3.
• Menck GmbH Figure 3.
• National Coal Board Figures 2.18, 4.26 and 8.
• Numa Hammers Figure 3.
• Offshore Technology Conference Figures 4.16, 5.29 and 8.

Piling is both an art and a science. The art lies in selecting the most suitable type of pile and method of installation for the ground conditions and the form of the loading. Science enables the engineer to predict the behaviour of the piles once they are in the ground and subject to loading. This behaviour is influenced profoundly by the method used to install the piles and it cannot be predicted solely from the physical properties of the pile and of the undisturbed soil. A knowledge of the available types of piling and methods of constructing piled foundations is essential for a thorough understanding of the science of their behaviour. For this reason the author has preceded the chapters dealing with the calculation of allowable loads on piles and deformation behaviour by descriptions of the many types of proprietary and non-proprietary piles and the equipment used to install them. In recent years substantial progress has been made in developing methods of predicting the behaviour of piles under lateral loading. This is important in the design of foundations for deep-water terminals for oil tankers and oil carriers and for offshore platforms for gas and petroleum production. The problems concerning the lateral loading of piles have there- fore been given detailed treatment in this book. The author has been fortunate in being able to draw on the world-wide experience of George Wimpey and Company Limited, his employers for nearly 30 years, in the design and construction of piled foundations. He is grateful to the management of Wimpey Laboratories Ltd. and their parent company for permission to include many examples of their work. In particular, thanks are due to P. F. Winfield, FIStruct E, for his assistance with the calculations and his help in checking the text and worked examples.

Burton-on-Stather, 1977

M. J. T

Preface to first edition

Chapter 1

General principles and practices

1.1 Function of piles

Piles are columnar elements in a foundation which have the function of transferring load from the superstructure through weak compressible strata or through water, onto stiffer or more compact and less compressible soils or onto rock. They may be required to carry uplift loads when used to support tall structures subjected to overturning forces from winds or waves. Piles used in marine structures are subjected to lateral loads from the impact of berthing ships and from waves. Combinations of vertical and horizontal loads are carried where piles are used to support retaining walls, bridge piers and abutments, and machinery foundations.

1.2 Historical

The driving of bearing piles to support structures is one of the earliest examples of the art and science of a civil engineer. In Britain, there are numerous examples of timber piling in bridge works and riverside settlements constructed by the Romans. In mediaeval times, piles of oak and alder were used in the foundations of the great monasteries constructed in the fenlands of East Anglia. In China, timber piling was used by the bridge builders of the Han Dynasty (200 BC to AD 200). The carrying capacity of timber piles is limited by the girth of the natural timbers and the ability of the material to withstand driving by hammer without suffering damage due to splitting or splintering. Thus primitive rules must have been estab- lished in the earliest days of piling by which the allowable load on a pile was determined from its resistance to driving by a hammer of known weight and with a known height of drop. Knowledge was also accumulated regarding the durability of piles of different species of wood, and measures taken to prevent decay by charring the timber or by building masonry rafts on pile heads cut off below water level. Timber, because of its strength combined with lightness, durability and ease of cutting and handling, remained the only material used for piling until comparatively recent times. It was replaced by concrete and steel only because these newer materials could be fabricated into units that were capable of sustaining compressive, bending and tensile forces far beyond the capacity of a timber pile of like dimensions. Concrete, in particular, was adaptable to in-situ forms of construction which facilitated the installation of piled foundations in drilled holes in situations where noise, vibration and ground heave had to be avoided. Reinforced concrete, which was developed as a structural medium in the late nineteenth and early twentieth centuries, largely replaced timber for high-capacity piling for works on land. It could be precast in various structural forms to suit the imposed loading and ground

conditions, and its durability was satisfactory for most soil and immersion conditions. The partial replacement of driven precast concrete piles by numerous forms of cast in-situ piles has been due more to the development of highly efficient machines for drilling pile bore- holes of large diameter and great depth in a wide range of soil and rock conditions, than to any deficiency in the performance of the precast concrete element. Steel has been used to an increasing extent for piling due to its ease of fabrication and handling and its ability to withstand hard driving. Problems of corrosion in marine struc- tures have been overcome by the introduction of durable coatings and cathodic protection.

1.3 Calculations of load-carrying capacity

While materials for piles can be precisely specified, and their fabrication and installation can be controlled to conform to strict specification and code of practice requirements, the calculation of their load-carrying capacity is a complex matter which at the present time is based partly on theoretical concepts derived from the sciences of soil and rock mechanics, but mainly on empirical methods based on experience. Practice in calculating the ultimate carrying capacity of piles based on the principles of soil mechanics differs greatly from the application of these principles to shallow spread foundations. In the latter case the entire area of soil supporting the foundation is exposed and can be inspected and sampled to ensure that its bearing characteristics conform to those deduced from the results of exploratory boreholes and soil tests. Provided that the correct constructional techniques are used the disturbance to the soil is limited to a depth of only a few centimetres below the excavation level for a spread foundation. Virtually the whole mass of soil influenced by the bearing pressure remains undisturbed and unaffected by the constructional operations (Figure 1.1a). Thus the safety factor against general shear failure of the spread foundation and its settlement under the design working load can be predicted from a knowledge of the physical characteristics of the undisturbed soil with a degree of certainty which depends only on the complexity of the soil stratification. The conditions which govern the supporting capacity of the piled foundation are quite different. No matter how the pile is installed, whether by driving with a hammer, by jetting, by vibration, by jacking, screwing or drilling, the soil in contact with the pile face, from which the pile derives its support by shaft friction, and its resistance to lateral loads, is com- pletely disturbed by the method of installation. Similarly, the soil or rock beneath the toe of a pile is compressed (or sometimes loosened) to an extent which may affect significantly its end-bearing resistance (Figure 1.1b). Changes take place in the conditions at the pile–soil interface over periods of days, months or years which materially affect the skin-friction resistance of a pile. These changes may be due to the dissipation of excess pore pressure set up by installing the pile, to the relative effects of friction and cohesion which in turn depend on the relative pile-to-soil movement and to chemical or electro-chemical effects caused by the hardening of the concrete or the corrosion of the steel in contact with the soil. Where piles are installed in groups to carry heavy foundation loads, the operation of driving or drilling for adjacent piles can cause changes in the carrying capacity and load/settlement characteristics of the piles in the group that have already been driven. In the present state of knowledge, the effects of the various methods of pile installation on the carrying capacity and deformation characteristics cannot be calculated by the strict application of soil or rock mechanics theory. The general procedure is to apply simple empirical factors to the strength, density and compressibility properties of the undisturbed

2 General principles and practices

construction, yet the ability of a pile to carry its load is judged on its behaviour under a comparatively rapid loading test made only a few days after installation. Because of the importance of such time effects both in fine- and coarse-grained soils the only practicable way of determining the load-carrying capacity of a piled foundation is to confirm the design calculations by short-term tests on isolated single piles, and then to allow in the safety factor for any reduction in the carrying capacity with time. The effects of grouping piles can be taken into account by considering the pile group to act as a block foundation, as described in Chapter 5.

1.4 Dynamic piling formulae

The soil mechanics approach to calculating allowable working loads on piles is that of determining the resistance of static loads applied at the test-loading stage or during the working life of the structure. Methods of calculation based on the measurement of the resist- ance encountered when driving a pile were briefly mentioned in the context of history. Historically all piles were installed by driving them with a simple falling ram or drop hammer. Since there is a relationship between the downward movement of a pile under a blow of given energy and its ultimate resistance to static loading, when all piles were driven by a falling ram a considerable body of experience was built up and simple empirical formulae established from which the ultimate resistance of the pile could be calculated from the ‘set’ of the pile due to each hammer blow at the final stages of driving. However, there are many drawbacks to the use of these formulae with modern pile-driving equipment par- ticularly when used in conjunction with diesel hammers. The energy of blow delivered to the pile by these types increases as the resistance of the ground increases. The energy can also vary with the mechanical condition of the hammer and its operating temperature. Simple dynamic formulae are now largely discredited as a means of predicting the resistance of piles to static loading unless the driving tests are performed on piles instrumented to meas- ure the energy transferred to the pile head. If this is done the dynamic analyser (see Section 7.3) provides the actual rather than the assumed energy of blow enabling the dynamic formula to be used as a means of site control when driving the working piles. Dynamic pile formulae

4 General principles and practices

(a) (b)

Soil progressively increasing in stiffness or relative density with increasing depth

Rock or hard relatively incompressible soil

Soft highly compressible soil

Figure 1.2 Types of bearing pile (a) Friction pile (b) End-bearing pile.

are allowed to be used by Eurocode EC7 provided that their validity has been demonstrated by experience in similar ground conditions or verified by static loading tests. Steady progress has been made in developing analytical methods for calculating pile capacity. With increasing experience of their use backed by research, the soil mechanics approach can be applied to all forms of piling in all ground conditions, whereas even if a reliable dynamic formula could be established its use would be limited to driven piles only. However, dynamic formulae still have their uses in predicting the stresses within the material forming the pile during driving and hence in assessing the risk of pile breakage, and their relevance to this problem is discussed in Chapter 7.

1.5 Code of practice requirements

The uncertainties in the methods of predicting allowable or ultimate loads on piles are reflected in the numerous ways of defining these loads in the many codes of practice which cover piling. The British Standard Code of Practice BS 8004: 1986 (Foundations) defines the ultimate bearing capacity of a pile as ‘The load at which the resistance of the soil becomes fully mobilized’ and goes on to state that this is generally taken as the load causing the head of the pile to settle a depth of 10% of the pile width or diameter. BS 8004 does not define ultimate loads for uplift or lateral loading. Specific design information is limited to stating the working stresses on the pile material and the cover required to the reinforcement, the require- ments for positional tolerance and verticality also being stated. No quantitative information is given on shaft friction or end-bearing values in soils or rocks, but many countries place limits on these values or on maximum pile loads in order to ensure that piles are not driven very heav- ily so as to achieve the maximum working load that can be permitted by the allowable stress on the cross-sectional area of the pile shaft. A conflict can arise in British practice where structures, including foundation substructures, are designed to the requirements of BS 8110 and their foundations to those of BS 8004. In the former document partial safety factors are employed to increase the characteristic dead and imposed loads to amounts which are defined as the ultimate load. The ultimate resistance of the structure is calculated on the basis of the characteristic strength of the material used for its construction which again is multiplied by a partial safety factor to take into account the possibility of the strength of the material used being less than the designed characteristic strength. Then, if the ultimate load on the structure does not exceed its ultimate resistance to load, the ultimate or collapse limit state is not reached and the structure is safe. Deflections of the structure are also calculated to ensure that these do not exceed the maximum values that can be tolerated by the structure or user, and thus to ensure that the serviceability limit state is not reached. When foundations are designed in accordance with BS 8004, the maximum working load is calculated. This is comparable to the characteristic loading specified in BS 8110, i.e. the most unfavourable combination of the dead and imposed loading. The resistance offered by the ground to this loading is calculated. This is based on representative shearing strength parameters of the soils or rocks concerned. These are not necessarily minimum or average values but are parameters selected by the engineer using his experience and judgement and taking into account the variability in the geological conditions, the number of test results available, the care used in taking samples and selecting them for test, and experience of other site investigations and of the behaviour of existing structures in the locality. The maximum load imposed by the sub-structure on the ground must not exceed the calculated

General principles and practices 5