47315_fm

7/29/2019 47315_fm

1/7

UNSATURATEDSOIL MECHANICS

NING LU

Colorado School of Mines

and

WILLIAM J. LIKOS

University of MissouriColumbia

JOHN WILEY & SONS, INC.

Copyright 2004 John Wiley & Sons Retrieved from: www.knovel.com

7/29/2019 47315_fm

2/7

This book is printed on acid-free paper.

Copyright 2004 by John Wiley & Sons, Inc. All rights reserved.

Published by John Wiley & Sons, Inc., Hoboken, New Jersey

Published simultaneously in Canada.

No part of this publication may be reproduced, stored in a retrieval system, or transmitted in

any form or by any means, electronic, mechanical, photocopying, recording, scanning, or

otherwise, except as permitted under Section 107 or 108 of the 1976 United States CopyrightAct, without either the prior written permission of the Publisher, or authorization through

payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222

Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 750-4470, or on the web at

www.copyright.com. Requests to the Publisher for permission should be addressed to the

Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201)

748-6011, fax (201) 748-6008, e-mail: [email protected].

Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best

efforts in preparing this book, they make no representations or warranties with respect to the

accuracy or completeness of the contents of this book and specifically disclaim any implied

warranties of merchantability or fitness for a particular purpose. No warranty may be created orextended by sales representatives or written sales materials. The advice and strategies contained

herein may not be suitable for your situation. You should consult with a professional where

appropriate. Neither the publisher nor author shall be liable for any loss of profit or any other

commercial damages, including but not limited to special, incidental, consequential, or other

damages.

For general information on our other products and services or for technical support, please

contact our Customer Care Department within the United States at (800) 762-2974, outside the

United States at (317) 572-3993 or fax (317) 572-4002.

Wiley also publishes its books in a variety of electronic formats. Some content that appears in

print may not be available in electronic books. For more information about Wiley products,

visit our web site at www.wiley.com.

Library of Congress Cataloging-in-Publication Data:

Lu, Ning, 1960

Unsaturated soil mechanics / by Ning Lu and William J. Likos.

p. cm.

Includes bibliographical references and index.

ISBN 0-471-44731-5 (cloth)

1. Soil mechanics. 2. Soil moisture. I. Likos, William J. II. Title.

TA710.L74 2004624.15136dc22

2004004218

Printed in the United States of America

10 9 8 7 6 5 4 3 2 1


7/29/2019 47315_fm

3/7

To

Vivian, Connie, Benton, Jonas, Holly, and Shemin


7/29/2019 47315_fm

4/7

xvii

FOREWORD

Although a significant portion, if not the majority, of conditions encountered

in geotechnical engineering practice involves unsaturated soils, the traditionalanalysis and design approach has been to assume the limiting conditions rep-

resented by either completely dry or completely saturated soils. The primary

motivation for this assumption is that measuring the properties of soils con-

taining only one fluid phase (i.e., either air or water) is vastly easier than that

of soils containing two fluid phases (i.e., both air and water). The primary

justification for the assumption is that the approach usually is conservative.

For example, the shear strength of a water-saturated soil is lower than the

shear strength of the same soil at the same void ratio under unsaturated con-

ditions. However, several considerations within the past decade or so warranta reassessment of this approach.

First, the assumption of saturated soil conditions is simply not appropriate

in some applications, such as in evaluating the heave of foundations on swell-

ing or expansive soils. Second, advances in technology continue to improve

our ability to measure, characterize, and predict the properties, behavior, and

performance of unsaturated soils. Third, the ever-increasing costs associated

with construction make the continued reliance on conservatism less econom-

ically appealing. As a result, the motivation for applying the principles of

unsaturated soil mechanics to geotechnical engineering problems where un-

saturated soil conditions prevail is increasing.

Unfortunately, education and training of practitioners in the area of unsat-

urated soil mechanics currently is limited. This limitation is due, in part, to

the lack of instructors educated in the area of unsaturated soil mechanics, the

paucity of formal courses that are being offered in the area of unsaturated


7/29/2019 47315_fm

5/7

xviii FOREWORD

soil mechanics, and the dearth of formal textbooks emphasizing the principlesof unsaturated soil mechanics.

Unsaturated Soil Mechanics has been written largely in response to boththe increasing demand for geotechnical engineers who are knowledgeable inunsaturated soil mechanics and the current limitations in research and edu-cation in unsaturated soil mechanics. In writing Unsaturated Soil Mechanics,the authors have focused the presentation of the material on principles ratherthan applications because a fundamental knowledge based on principles ismore likely to be retained and is more useful in terms of the depth and breadthof applications that subsequently can be addressed. The book offers a criticalassessment of the state of the art with respect to the stress in and strength ofunsaturated soils. Both the microscopic physical basis and the macroscopicthermodynamic framework for water retention and the state of stress in un-saturated soils are covered. The authors comprehensive treatment of mea-surement and modeling techniques not only enhances an understanding of theprinciples but also represents a valuable resource for future consultation. Theoverall result is that Unsaturated Soil Mechanics represents a thorough andcomprehensive treatment of the subject that is written clearly and effectivelyand should remain a valuable textbook and reference source for many yearsto come.

CHARLES D. SHACKELFORD

Professor, Department of Civil Engineering

Colorado State University

Fort Collins, Colorado


7/29/2019 47315_fm

6/7

xix

PREFACE

The principal aim of this book is to provide a thorough grounding in unsat-

urated soil mechanics principles from three fundamental perspectives: ther-modynamics, mechanics, and hydrology. The book is written to guide a firstcourse on the subject and is primarily intended for undergraduate seniors,graduate students, and researchers with backgrounds in the more general fieldsof geotechnical engineering, soil science, environmental engineering, andgroundwater hydrology.

In formulating this book, we have maintained the opinion that a first coursein any branch of mechanics should emphasize the fundamental principles thatgovern the phenomena of interest. A principles-based approach to learning is

most benefi

cial to the general reader and is particularly appropriate for thesubject of unsaturated soil mechanics as it remains a young, dynamic, andrapidly emerging field of research and practice. Our general viewpoint to-wards the pursuit of understanding is reflected by Thomas Henry Huxleys(18251895) statement: The known is finite, the unknown infinite; intellec-tually we stand on an islet in the midst of an illimitable ocean of inexplica-bility. Our business in every generation is to reclaim a little more land. Wehope that this book will provide the necessary background and motivation forthose who desire to explore and reclaim the ocean of unsaturated soil me-

chanics problems that nature and society continue to present.A comprehensive introductory account of unsaturated soil mechanics ispresented in Chapter 1 to provide readers with a road map for the remainderof the book. This includes a general introduction to unsaturated soil phenom-ena (Section 1.1), a formulation for the scope of the book (Section 1.2), adiscussion of the role of unsaturated soil mechanics in nature and engineeringpractice (Section 1.3), a discussion of some essential differences between


7/29/2019 47315_fm

7/7

xx PREFACE

unsaturated soil mechanics and classical (saturated) soil mechanics (Section1.4), an introduction to the state and material variables and constitutive lawsforming the language of unsaturated soil mechanics (Section 1.5), and anintroduction to suction and pore water potential concepts for unsaturated soil(Section 1.6).

The remainder of the book is presented as four progressive and interrelatedparts. Part I examines the fundamental principles applicable to unsaturatedsoil mechanics. Parts II and III illustrate application of these principles tostress and flow phenomena in unsaturated soil, respectively. Finally, Part IVdescribes, illustrates, and evaluates the major measurement and modelingtechniques used to quantify the state and material variables required to de-scribe these stress and flow phenomena.

In formulating the first three parts of the text, we offer a perspective thatunites the microscopic physical basis and the macroscopic thermodynamicframework for pore water retention and the state of stress in unsaturated soil.Two constitutive relationships are needed to describe unsaturated flow phe-nomena, namely, the soil-water characteristic curve and the hydraulic con-ductivity characteristic curve. For unsaturated stress phenomena, we contendthat an additional relationship referred to as the suction stress characteristiccurve is required.

The materials covered in this book have been an outgrowth of unsaturatedsoil mechanics courses taught at the Colorado School of Mines and Universityof MissouriColumbia for graduating seniors and graduate students overthe past four years. The book contains sufficient material for a one-semester,laboratory-supplemented course tailored along either a geomechanics or geo-environmental track. Problems are provided at the end of each chapter withsolutions available from the publishers web site at www.wiley.com.

While many colleagues have been helpful in making the book possible inits present form, any error, bias, or inaccuracy remains ours. We are gratefulto the following people who generously provided insightful reviews for atleast one chapter: Jiny Carrera, Mandar M. Dewoolkar, Susan Eustes, SheminGe, Jonathan W. Godt, D. Vaughan Griffiths, Laureano R. Hoyos, Jr., NasserKhalili, K.K. (Muralee) Muraleetharan, Harold W. Olsen, Paul M. Santi,Charles D. Shackelford, Radhey S. Sharma, Alexandra Wayllace, andChangfu Wei.

NING LU

WILLIAM J. LIKOS

47315_fm

Documents

Transcript of 47315_fm