The Penetrometer and Soil Exploration: Interpretation of penetration diagrams – theory and practice

469 Pages·1972·8.954 MB·1-464\469

by  G. SANGLERAT (Eds.)

Translated
by
G. Gendarme, Β. Sc., M. Sc., CE.
Chief Soil and Foundation Engineer
Fugro N.V.
Leidschendam, The Netherlands
Developments in Geotechnical Engineering, 1
THE PENETROMETER AND SOIL
EXPLORATION
Interpretation of penetration diagrams-
theory and practice
by
G. SANGLERAT
Professor of Soil Mechanics and Foundations
Ecole Centrale Lyonnaise and Conservatoire National des Arts et Mιtiers
Chief Engineer of SOCO TEC
Lyons, France
ELSEVIER PUBLISHING COMPANY Amsterdam London New York 1972
ELSEVIER PUBLISHING COMPANY
335 Jan van Galenstraat
P.O. Box 211, Amsterdam, The Netherlands
AMERICAN ELSEVIER PUBLISHING COMPANY, INC.
52 Vanderbilt Avenue
New York, New York 10017
Library of Congress Card Number: 73-180007
ISBN 0-444-40976-9
With 217 illustrations and 48 tables.
Copyright © 1972 by Elsevier Publishing Company, Amsterdam
All rights reserved. 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,
or otherwise, without the prior written permission of the publisher, Elsevier Publishing Com-
pany, Jan van Galenstraat 335, Amsterdam
Printed in The Netherlands
To Miette
PREFACE
Static penetration tests have not been widely used in English speaking countries,
particularly in America, in spite of their great versatility and reliability. This situa-
tion does not indicate any reluctance on the part of the engineers in these countries
to use penetration tests as such; the wide acceptance of the comparatively crude
Standard Penetration Test demonstrates an appreciation of the benefits of in-situ
tests of this type. Failure to take advantage of the more refined static tests has no
doubt been a consequence of unfamiliarity, not only with the procedures them-
selves, but also with the background of theory and experience accumulated in
connection with them elsewhere.
Engineers acquainted only with the literature in English may be surprised to
discover in this book the great extent and quality of practical experience and the
amount of research supporting the use of static penetrometers as routine tools for
design investigation. Hence, the English translation of Professor Sanglerat's book is
more than a welcome addition to the literature in applied soil mechanics. It can be
expected to open the door to widespread use of penetration techniques of great
merit, previously not used to full advantage. It is to be hoped that, as a conse-
quence of Professor Sanglerat's efforts, the most appropriate types of penetration
tests will take their place in the broad spectrum of techniques of subsurface explo-
ration.
The exploration of subsurface conditions cannot be stereotyped. The require-
ments of each job differ from those of most others. The geology of the site, the
magnitude and complexity of the structure, financial considerations - all enter into
the choice of the method or methods of subsurface exploration. Rarely is one single
procedure adequate. If nothing is known about the subsurface conditions at or near
a new site, it would be unwise to depend on penetration testing alone. Judging the
type of subsurface materials on the basis of the results of such tests without visual
examination or without the performance of other index tests could easily lead to
error. Once the general nature of the material is determined, however, and particu-
larly if the deposit has an erratic structure, penetration tests come into their own.
In many instances they are inherently more satisfactory than laboratory tests on
samples, particularly if sampling without disturbance is difficult or impracticable.
No matter how refined or how crude a method of field investigation may be, the
engineer who has used it extensively, and who has compared the results with
subsequent behavior during and after construction on many projects, learns its
VIII PREFACE
subtleties, its pitfalls and limitations, and the benefits to be derived from its use. It
becomes part of his thinking and, in time, a valuable aid. Penetration tests have
become such an aid to hundreds, perhaps thousands, of engineers. The more widely
used of the static tests are now part of the fabric of engineering practice in much of
the world. Thanks to this book, a veritable storehouse of information assembled
with great patience and thoroughness, English speaking engineers can now incorpo-
rate the accumulated experience of their colleagues around the world into their
own practice and can take full benefit of these powerful and economical procedures
for investigating subsurface conditions.
RALPH B. PECK
Professor of Civil Engineering, University of Illinois, Urbana, 111. (U.S.A.)
President of the International Society for Soil Mechanics and Foundation Engineering
INTRODUCTION
Engineers and builders have always had to face the problem of choosing the
most suitable type of foundation for a specific structure and of determining the
allowable bearing capacity of the soil supporting the foundation. For centuries,
important works of art, such as cathedrals, were constructed using rough empirical
methods, most of which were successful. Failures, however, were numerous and
sometimes catastrophic.
In the last few decades, construction activity has had to cope with a tremendous
boom. Strict reliance on past experience is no longer as practicable as it used to be
because developments have had to be made over land areas, in and around large
cities, which had previously been avoided because of their insuitability for construc-
tion. In addition, modern industry cannot afford the delays and costs of old meth-
ods.
The choices for highway alignments are restricted and it is often necessary to
locate a new road over poor sites. The necessity of building ever faster, often on less
than favorable locations, has prompted engineers all over the world to continuously
develop the science which K.Terzaghi called "soil mechanics". Nowadays, it is
possible to determine the properties of a soil for engineering purposes by the use of
well-established criteria.
The origins of soil mechanics go back to Coulomb, Poisson, Poncelet, Prony and
Darcy. Recent French researchers, such as Levy, Boussinesq, Resal, Caquot, Kerisel,
Mayer, L'Herminier, Mandel, Tcheng, Habib, Cambefort, Absi, and Biarez were
particularly successful in developing the mathematics of the new science. In the
meantime, and especially since 1910, research has been carried out in numerous
other countries, usually with the specific aim of studying localized soil problems.
Extensive knowledge was rapidly acquired of bad soil conditions existing in The
Netherlands, in the valley of the Danube River, the soil of Mexico City and
Chicago, and the glacial clays of the Scandinavian countries. Valuable contributions
were thus made by Buisman and Geuze in Holland, De Beer and Verdeyen in
Belgium, Meyerhof and Legget in Canada, Bjerrum in Norway, Brinch Hansen in
Denmark, Skempton, Bishop and Henkel in Great Britain, Carillo and Zeeveart in
Mexico, Da Costa Nunes and V. de Mello in Brazil, Salas in Spain, Fellenius in
Sweden and Terzaghi in Austria and later in the United States where he created the
world's most important school for soil mechanics, with D.W.Taylor, A.Casagrande,
and R.B.Peck. This large amount of experimental and theoretical research has often
exceeded the efforts made in France.
XVIII INTRODUCTION
It is unfortunately still too common to see architects and engineers neglect the
benefits that can be derived from specialists in soil mechanics. Often, serious prob-
lems arise during construction which require major revisions, at great delays and
great costs, which could have been avoided had the knowledge of soil conditions
been known in advance.
Statistics gathered in various countries show that 80% of the cases where con-
struction costs exceed bid prices were due to unforeseen conditions encountered
during the construction of foundations. Of the remaining 20%, 15% were due to plan
changes during construction and 5% to errors of construction. Most of the excessive
construction cost can therefore be blamed on the lack of knowledge of soil condi-
tions during the design stage.
A recent study has shown that in France, failures of highway and road embank-
ments, which for the most part were constructed without prior knowledge of the
foundation conditions, have amounted to a cost of 5 millions U.S. dollars over a
period of 5 years.
It is always desirable to investigate soil conditions before the purchase of a piece
of land and certainly before construction plans are finalized. This procedure should
help in arriving at a good estimate of the cost of the foundation.
What should a preliminary study comprise? At least it is conditioned by:
(1) knowledge of the site; (2) determination of the depth of foundation, whether
shallow or deep; (3) allowable bearing capacities; (4) anticipated settlements, either
total or differential.
The purpose of this book then is to present the many uses of the penetrometer
for the purpose of investigating soil conditions.
Any comprehensive soil investigation must first determine the overall aspect of
the sub-strata so that a brief geological history may be deduced. In addition, the
distinct layers of various soil types must be reasonably located. Then, the mechani-
cal properties of the soil of each distinct layer must be determined with accuracy.
Three methods of testing may be used:
(7) In situ load tests on full-scale foundations.
(2) Laboratory testing of undisturbed samples.
(3) In situ testing of soils.
The first method, commonly used to determine the bearing capacity of piles,
requires almost one week of testing and is expensive (about 3,000 dollars per test).
Pile load tests are rarely performed in France and are more commonly employed in
the U.S.A.
The testing of shallow foundations is often difficult if not impossible when
dealing with raft foundations. Tests of this nature have been performed on small-
size footings for research purposes, but these tests are expensive and are not always
easily to interpret.
Laboratory testing of undisturbed samples, although very sophisticated, requires
INTRODUCTION XIX
great care to avoid disturbance during handling, or systematical disturbance during
testing, and it may be difficult to relate the laboratory test results to the in situ
properties of the soil. There is always a certain degree of disturbance to the samples
because the confining pressures which exist in the ground are forcibly changed
when the sample is collected. By and large, the length of a sample is 3—4 times its
diameter. The upper end must be carefully trimmed to eliminate any fall-in material
which is often encountered at the bottom of a boring. The type of sampling gear
used may cause some laboratory data to vary as much as 35%. Caquot (1956) stated
that the use of sampling spoons is an antiquated method of obtaining samples for
the purpose of determining mechanical properties.
Usually it is economically not possible to recover continuous samples from a
boring, and normally incomplete records of the soil stratification are obtained. The
samples which are tested give design data such as soil cohesion and angles of
internal friction which are the basic coefficients of the bearing-capacity formulas.
These, however, give only approximate estimates of the bearing capacity of soils,
especially in the case of deep foundations.
Deep borings, advanced with continuous flight augers or with percussion-type
drill rigs, give very valuable information because they afford a visual classification
of all the soils penetrated. There are three drawbacks to the use of this type of
drilling:
(7) Difficulty in the identification and analysis of sub-strata of great hetero-
geneity.
(2) Considerable reliance on the human factor. The conclusions may rely too
heavily on the qualifications of the driller.
(3) Difficulty of obtaining samples for visual identification in sandy soils, and
the large amount of disturbance caused to the material being brought out of the
hole, all of which is increased when drilling below the water table.
The penetrometer is a handy tool to avoid many of the drawbacks of drilling and
sampling, and it has become a widely accepted means for investigations of sub-
surface soil conditions.
An investigation program always depends on the type of structure for which it is
made, and on the type of foundation soils investigated. There is, however, one
principle which should always be adhered to, and that is never to rely entirely on
the analogy or the extrapolation of information pertaining to a nearby site. Soil
properties may vary consideiably, even in well-known, well-defined, and so-called
homogeneous layers. In situ tests are best suited for a quick determination of the
presence of abnormal conditions in "homogeneous" layers. The in situ tests of this
type are classified into two categories: (7) electric or seismic surveys; (2) accurate
determination of properties with the use of the S.P.T. (Standard Penetration Test),
pressuremeter or rheotest - all of which give a discontinuous log - or the contin-
uous data as may be obtained by penetrometer tests.
XX INTRODUCTION
The advantages as well as the limitations of the use of the static and dynamic
penetrometers are presented in this book. It is the author's conviction that the use
of the penetrometer in a well thought out investigation program which includes
samples recovery and laboratory testing of undisturbed samples, leads to very eco-
nomical and comprehensive engineering data for the design of foundations.
ACKNOWLEDGEMENTS
Numerous articles and references are available in the engineering literature con-
cerning static or dynamic penetrometers, their use and applications. In general, each
article deals with some detailed and particular aspects of the use of the instrument or
the interpretation of data. Therefore it is a laborious task for the interested engineer to
obtain an overall and comprehensive review of the available information. Additional
difficulties are encountered from the fact that good references are found not only
in English, but also in German, Danish, Spanish, Bulgarian, French, Dutch, Norwe-
gian, Portuguese, Swedish, Russian, Greek, Turkish, Jugoslav and other languages.
So far, no comprehensive text is available which reviews the state of the art of
the penetrometer tests, and it appears appropriate to present such a text containing
a review of the various types of penetrometers presently in use and of the theories
which have been developed to interpret the data for application in engineering
practice. This is the main purpose of this book.
The book reflects the personal experience of the author with the use of pene-
trometers gained since 1951 both in the Belgian Congo and in France. It is hoped
that this text will serve as an easy reference for the interpretation of test data and
to gain a better understanding of the uses and limitations of the equipment.
Many prominent engineers and researchers have contributed with their personal
experiences and have advised the author during his numerous travels in Belgium,
Brazil, Canada, Germany, Great Britain, the United States, The Netherlands, Spain
and Venezuela. Particular thanks are due to many wellknown specialists: in Bel-
gium: Prof. De Beer, Director of the Institut Geo technique de l'Etat in Ghent, and
his assistant, Mr. Raedschelders; Prof. Verdeyen and his co-worker Mr. Nuyens of
the Brussels University; in Brazil: Prof. M. Vargas in Sao Paulo, President of the
International Commission for the dynamic and static penetrometer tests; Prof. Da
Costa Nunes, Director of Tecnosolo of Rio de Janeiro; Mr. V. De Mello, director of
Geoconsult of Sao Paulo; in Canada: Prof. G.G. Meyerhof, dean of the University
of New Scotia in Halifax; in the United States: Prof. M.A. Casagrande of Harvard
University; Prof. R.B. Peck and Prof. H.O. Ireland of the University of Illinois; Mr.
M.Y. Lacroix, of Woodward and Associates, and Prof, of Soil Mechanics at the
University of Montreal; Mr. W.G. Holtz and H.J. Gibbs, of the United States Bureau
of Reclamation, Denver, Colo.; Prof. H.B. Seed, of the University of California,