Soil Mechanics in Engineering Practice, 3rd Ed

Book Preface

In 1948 Karl Terzaghi, in the preface to the First Edition, wrote:

Unfortunately the research activities in soil mechanics . . . diverted the attention of many investigators and teachers from the manifold limitations imposed by nature on the application of mathematics to problems in earthwork engineering. As a consequence, more and more emphasis has been placed on refinements in sampling and testing and on those very few problems that can be solved with accuracy. Yet, accurate solutions can be obtained only if the soil strata are practically homogeneous and continuous in horizontal directions. Furthermore, since the investigations leading to accurate solutions involve highly specialized methods of sampling and testing, they are justified only in exceptional cases. On the overwhelming majority of jobs no more than an approximate forecast is needed, and if such a forecast cannot be made by simple means it cannot be made at all. If it is not possible
to make an approximate forecast, the behavior of the soil must be observed during construction, and the design may subsequently have to be modified in accordance with the findings. These facts cannot be ignored without defying the purpose of soil mechanics. They govern the treatment of the subject in this book.

In the half-century since these words were written, research in sampling and testing has continued unabated, and a vast literature has accumulated about the properties of soils, much of it directed toward advancing one or another school of thought concerning idealized conceptions of soil behavior. During the same time, remarkable advances in electronic calculation have made theoretical forecasts possible for problems involving complex boundary and stratigraphic conditions. Thus it may no longer be true that if a forecast cannot be made by simple means it cannot be made at all. In exchange for this progress, however, it has become increasingly important that the choice of soil properties used in the analyses be based on a fundamentally correct knowledge of soil behavior.

Part I of this edition is essentially a digest of the findings of research workers concerning the properties of soil that are of interest to engineers. The digest presents the findings from a fundamental point of view rather than as representing any one school of thought. Because of the many contributions of the research workers, this part of the book has been expanded markedly over that of the previous editions.

Part 11, on the other hand, has been increased only slightly, because the essential theoretical tools were already available 50 years ago. The development of finiteelement and similar procedures, although changing the mode of many calculations, has not altered this fact. Moreover, the closed-form solutions of the classical theories of elasticity and plasticity permit the simple, rapid approximate calculations that should always be made to provide a “back of the envelope” estimate to permit judging the need for or the reasonableness of the results of any more elaborate calculational procedure.

As in previous editions, Part I11 deals with the art of getting satisfactory results in earthwork and foundation engineering at a reasonable cost, in spite of the complexity of the structure of natural soil formations and in spite of the inevitable gaps in our knowledge of the soil conditions. The semi-empirical approach described and advocated in this Part has stood the test of time. It has become the hallmark of the practice of geotechnical engineering.

The authors are indebted to Dr. M. T. Davisson, Mr. R. M. Armstrong, and Prof. J. H. Long for their constructive reviews of the chapters on pile and pier foundations. The patient and expert typing of the many successive versions of the text by Mrs. Paul C. Jesse and Mrs. Joyce M. Snider are gratefully acknowledged. The new illustrations for this edition were drawn by Mr. Ron Winburn. Mr. Marawan Shahien provided invaluable assistance in checking the manuscript and in preparing, revising, and solving the problems. Figures and tables from journals, proceedings, and books are reproduced with permission from the respective publishers.

RALPH B. PECK
GHOLAMREZMAE SRI