Multiscale Geomechanics E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 532

Veröffentlichungsjahr: 2013

Beschreibung

This book addresses the latest issues in multiscale geomechanics. Written by leading experts in the field as a tribute to Jean Biarez (1927-2006), it can be of great use and interest to researchers and engineers alike. A brief introduction describes how a major school of soil mechanics came into being through the exemplary teaching by one man. Biarez's life-long work consisted of explaining the elementary mechanisms governing soil constituents in order to enhance understanding of the underlying scientific laws which control the behavior of constructible sites and to incorporate these scientific advancements into engineering practices. He innovated a multiscale approach of passing from the discontinuous medium formed by individual grains to an equivalent continuous medium. The first part of the book examines the behavior of soils at the level of their different constituents and at the level of their interaction. Behavior is then treated at the scale of the soil sample. The second part deals with soil mechanics from the vantage point of the construction project. It highlights Biarez's insightful adoption of the Finite Element Codes and illustrates, through numerous construction examples, his methodology and approach based on the general framework he constructed for soil behavior, constantly enriched by comparing in situ measurements with calculated responses of geostructures.

Leseprobe

Contents

Preface

Acknowledgments

Chapter 1 Jean Biarez: His Life and Work

1.1. Early years and arrival in Grenoble

1.2. From Grenoble to Paris

1.3. The major research interests of Jean Biarez

1.4. Research and teaching

1.5. Conclusion

Chapter 2 From Particle to Material Behavior: the Paths Chartered by Jean Biarez

2.1. Introduction

2.2. The available tools, the variables analyzed and limits of the proposed analyses

2.3. Analysis of geometric anisotropy

2.4. Analysis of the distribution of contact forces in a granular material

2.5. Analysis of local arrays

2.6. Particle breakage

2.7. Conclusion

2.8. Bibliography

Chapter 3 Granular Materials in Civil Engineering: Recent Advances in the Physics of Their Mechanical Behavior and Applications to Engineering Works

3.1. Behavior resulting from energy dissipation by friction

3.2. Influence of grain breakage on the behavior of granular materials

3.3. Practical applications to construction design

3.4. Conclusions

3.5. Bibliography

Chapter 4 Waste Rock Behavior at High Pressures: Dimensioning High Waste Rock Dumps

4.1. Introduction

4.2. Development of new laboratory equipment for testing coarse materials

4.3. Mining rock waste

4.4. Characterization of mechanical behavior of the waste rock

4.5. Evolution of density

4.6. Stability analysis and design considerations

4.7. Operation considerations

4.8. Conclusions

4.9. Acknowledgements

4.10. Bibliography

Chapter 5 Models by Jean Biarez for the Behavior of Clean Sands and Remolded Clays at Large Strains

5.1. Introduction

5.2. Biarez’s model for the oedometer test

5.3. Perfect plasticity state and critical void ratio

5.4. Normally and overconsolidated isotropic loading

5.5. The drained triaxial path for sands and clays

5.6. The undrained triaxial path for sands

5.7. Standard behavior for undrained sands

5.8. The triaxial behavior of “lumpy” sands

5.9. A new model to analyze the oedometer’s path

5.10. “De structuration” of clayey sediments

5.11. Conclusion

5.12. Examples of manuscript notes

5.13. Bibliography

Chapter 6 The Concept of Effective Stress in Unsaturated Soils

6.1. Introduction

6.2. Microstructural model for unsaturated porous media

6.3. Material and methods

6.4. Experimental results

6.5. Interpretation of results using the effective stress concept

6.6. Conclusions

6.7. Acknowledgements

6.8. Bibliography

Chapter 7 A Microstructural Model for Soils and Granular Materials

7.1. Introduction

7.2. The micro-structural model

7.3. Results of numerical simulation on Hostun sand

7.4. Model extension to clayey materials

7.5. Unsaturated granular materials

7.6. Summary and conclusion

7.7. Bibliography

Chapter 8 Modeling Landslides with a Material Instability Criterion

8.1. Introduction

8.2. Study of the second-order work criterion

8.3. Petacciato landslide modeling

8.4. Conclusion

8.5. Bibliography

Chapter 9 Numerical Modeling: An Efficient Tool for Analyzing the Behavior of Constructions

9.1. Notations

9.2. Introduction

9.3. Modeling soil behavior

9.4. Parameter identification strategy for the ECP model

9.5. Influence of constitutive behavior on structural response

9.6. Conclusions

9.7. Acknowledgments

9.8. Appendix

9.9. Bibliography

Chapter 10 Evaluating Seismic Stability of Embankment Dams

10.1. Introduction

10.2. Observed seismic performance

10.3. Method for analyzing seismic risk

10.4. Evaluation of seismic hazard

10.5. Re-evaluation of seismic stability

10.6. Semi-coupled modeling of liquefaction

10.7. Bibliography

List of Authors

Index

Jean Biarez (1927-2006), Professor at the University of Grenoble and at the Ecole Centrale in Paris, is considered to be one of the principal founders of modern soil mechanics in France. His pedagogy, scientific researchs, and engineering expertise have created a unique school of thought which has become highly influential and widely recognized by academics and engineers in the field of geotechnics.

First published 2012 in Great Britain and the United States by ISTE Ltd and John Wiley & Sons, Inc.

Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms and licenses issued by the CLA. Enquiries concerning reproduction outside these terms should be sent to the publishers at the undermentioned address:

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© ISTE Ltd 2012

The rights of Author’s name to be identified as the author of this work have been asserted by them/her/him in accordance with the Copyright, Designs and Patents Act 1988.

Library of Congress Cataloging-in-Publication Data

Multiscale geomechanics : from soil to engineering projects / edited by Pierre-Yves Hicher.

p. cm.

Includes bibliographical references and index.

ISBN 978-1-84821-246-6

1. Biarez, Jean. 2. Engineering geology--Mathematical models. 3. Soil mechanics--Mathematical models. I. Hicher, Pierre-Yves.

TA705.M84 2011

624.1′5--dc23

2011037492

British Library Cataloguing-in-Publication Data

A CIP record for this book is available from the British Library

ISBN: 978-1-84821-246-6

Cover photo: created by Grand′Maison Dam, France ; courtesy of EDF

Preface

Readers of one of our previous works, Constitutive Modeling of Soils and Rocks, may recall a fleeting reference to Professor Jean Biarez.

The present book, adapted and updated from the original French edition, pays tribute to the man and his work. It faithfully reproduces the spirit in which the 10 chapters were conceived although the content of the introductory chapter has been modified for the sake of explaining, as fully as possible, the historical context of Jean Biarez’s status in modern soil mechanics.

We are aware that, on the international stage of geomechanics, Jean Biarez’s role as a pioneer may not be fully appreciated because he does not occupy a large place in the literature. Unfortunately, his characteristic perfectionism and anxiety about committing tentative results and ideas to paper prevented him from publishing more.

Hence, to set the record straight for now and for posterity, we have decided to risk what Jean Biarez himself was so wary of doing throughout his long career − that is, to publish our work in progress in his honor, conscious that one day this work may be enriched or contradicted by further research.

Professor Jean Biarez (1927-2006) played an important role in creating a school of soil mechanics in France, a fact that has never been specifically acknowledged. Shortly after his death, a group of his students from France and around the world gathered for a day in Paris for what was to be a lively scientific colloquium. Out of this event, a book was published in 2010 by the majority of the participants who in their capacities as academic researchers and engineering experts aspire to transmit Professor Biarez’s vision of soil mechanics. The originality of Biarez’s approach consisted of a double objective:

− to understand the basic mechanisms that govern the interactions among soil constituents in order to improve the engineer’s scientific knowledge of terrain behavior;

− to introduce scientific discoveries into the field of engineering by introducing rational methods into civil and mechanical engineering.

The scope and organization of the original book, and its version in English, faithfully adhere to the spirit of Biarez’s vision of soil mechanics.

The first half of the book treats the behavior of soils at the scale of their different constituents and analyzes the organization of these constituents as if they were the motor of the material’s mechanical behavior. In the second half, soil behavior is studied at the scale of the representative elementary volume, that is, at the level of the soil sample. Here we encounter the approach introduced by Biarez that was to link the discontinuous medium formed by grains to an equivalent continuous medium. He demonstrated that this linkage could be conceived by connecting the representative parameters of the grains to the parameters of the constitutive laws of the equivalent continuous medium. These representative parameters can then be categorized into two groups:

− first, the mechanical properties of the grains and the contact laws;

− second, the geometrical conditions of the arrangement and the confinement of the grains.

This methodological approach has met with good results within the framework of quantifying the large deformation behavior in sands and remolded clays, a quantification that has permitted us to define a standard or reference behavior from the parameters of the nature of the soils.

Several mechanisms belonging to granular materials have been studied at different scales: geometric anisotropy from contact orientations and the orientation of contact forces as well as the equilibrium of local assemblies that are the cause of plastic mechanisms within granular materials. These mechanisms, which were studied experimentally by Biarez, are approached in this book by analytical and numerical means, the latter drawing from recent developments in discrete element mechanics. Several chapters also refer to grain breakage, a very prevalent phenomenon in granular materials, where we find another scale effect linked to the size of the constituents and to their evolution during the course of mechanical loading. As shown by Biarez, this phenomenon tends to modify the properties of the grain assembly. Grain breakage is discussed and taken into account in the calculation of construction projects, particularly in large rockfill dams.

Another phenomenon under discussion concerns the effect of water presence in soils. With water effect, the behavior of the equivalent continuous medium becomes dependent upon both the solid grain behavior and the behavior of the fluid and the solid−fluid interaction at the interfaces. This aspect is broached by studying the interactions and by discussing the notion of effective stress in non-saturated soils. An analysis of capillary forces at the grain scale shows that it is possible to devise a concept of effective stress that allows the behaviors of dry and partially saturated materials in the elastic domain at small deformation amplitudes to be joined and for a criterion of maximal resistance to be defined, whatever the degree of saturation may be. Another example of water effect can be found in coarse granular materials where compressibility increases during the saturation phase.

Based on Biarez’s conceptual framework, referred to as the passage from the discontinuous to the continuous medium, we have found it possible to construct constitutive models for the equivalent continuous medium from the intergranular properties and the geometry of the grain assemblies. The approaches that homogenize granular assembly behaviors generally consider the granular medium as an ensemble of tangential planes consisting of contact points between particles all in interaction with each other. Therefore, the moment has come to describe a contact law along these planes and to develop the homogenization operators that permit all the contacts at the scale of the continuous medium to be integrated. The homogenization approaches to granular assembly behaviors were developed in the first place to evaluate the elastic characteristics. An extended version of plastic behavior is presented in this book. The benefit of this type of approach is that it enables us to integrate the different physical mechanisms that appear at the scale of intergranular contacts naturally enough.

Landslides were of particular interest to Biarez and for this reason he developed calculation methods based on the plastic equilibrium. Recent studies have shown that material instability can emerge within a soil mass before the plastic criterion is reached. The phenomenon of material instabilities arises when the second-order work vanishes by annulling itself, in accordance with Hill’s studies on this subject. An analysis of the conditions of how second-order work annuls itself is made with the help of incremental non-linear or piecewise-linear laws. This analysis shows the existence of an instability cone gathering within itself all the unstable directions. An application has been made concerning the numerical simulation of a natural landslide with the help of a hydro-mechanical model for non-saturated soil. The results obtained show how potentially unstable zones develop during soil saturation.

Biarez’s work was a precursor concerning the use of the finite element codes for modeling construction projects. Spurred on by his enthusiasm, his co-workers at the Ecole Centrale de Paris developed the numerical code GEFDyn. The capacities of this calculation code are quite evident in the modeling of such projects as retaining walls, deep foundations and embankment dams. What this code manifested was the quality of the numerical predictions through the capacity of the particular constitutive model chosen to reproduce the rheology of the soil as well as the choice of parameters retained for any given soil. The latter was always seen as primordial in the eyes of Biarez, which led him in the last years of his life to collate a considerable collection of data from laboratory and in situ tests on a stock of very diverse soils. The results from these tests allowed him to propose a methodology in which the reference behaviors could construct a general framework, enriched thereafter by a comprehension of the geological history of the soil layers studied. This strategy of identifying the soil is discussed and illustrated by the impact it has on the calculation results of construction projects.

The principal preoccupation of Jean Biarez was always to place the comprehension of soil behavior at the service of engineers and to develop operational methods for facilitating and improving the quality of engineering constructions. As a staunch advocate of the observational method, he urged others to believe in the necessity of sounding out or “auscultating” existing constructions. In France, he was one of the first to work on dynamic soil behavior, to be applied primarily to testing the stability of nuclear power plants and dams under seismic loading, a subject of crucial concern for EDF (Electricité de France), a major public utilities firm for which Biarez not only worked as an engineering expert but remained attached to throughout his entire career.

The last chapter of this book evokes Biarez’s approach at both the fundamental level concerning soil behavior and at the applied level concerning his attempt to diagnose the reasons for accidents and collapses. One of his tasks as an engineering expert was to evaluate the seismic stability of embankment dams. Given the types of accidents studied, a methodology is presented here for evaluating seismic risk, particularly the most dangerous one among them, known as liquefaction.

The chapter that opens the book contains a brief biography of Jean Biarez’s professional career and recalls the contribution he made as a pioneer to the field of geomechanics in France as researcher and teacher just after the Second World War up to a more contemporary era, where the scientific contribution of his students started to become recognized internationally. The reader is invited to discover the role of a man whose vision has so far informed and inspired two generations of researchers, teachers and engineers. The progress obtained in geomechanical research can be attributed in no small part to his influence, especially since the creation of new research organizations in Europe, such as GRECO Géomatériaux and ALERT Geomaterials.

Pierre-Yves HICHER and Etienne FLAVIGNYOctober 2011

Acknowledgments

Without the active collaboration of my wife, Pearl-Angelika Lee, this book would have not seen the light of day. The countless hours she has spent editing it has vastly improved my work as well as the work of others. I wish to acknowledge, with gratitude, her generous contribution in making our writing more intelligible and pleasant to read.

Chapter 1

Jean Biarez: His Life and Work

Jean Biarez dedicated his work and life to the scientific advancement of soil mechanics. This introductory profile recalls his career within the context of the pioneering days in Grenoble to the years when he directed a thriving research laboratory at the Ecole Centrale de Paris.

Inevitably, many of the names cited in the following pages will not be familiar to readers outside of France, but evoking these names will hopefully give a better appreciation of the collective dimension that helped soil mechanics become an indispensable branch of civil engineering.

To characterize the highly complex personality of Jean Biarez and encompass his many extraordinary − though unsung − intellectual achievements would be nearly impossible if we did not single out certain aspects. We therefore highlight two traits that, as colleagues and students, we were able to witness: Jean Biarez’s tireless actions in fostering the ties between research and industry and his creative teaching methods inspiring generations of students.

1.1. Early years and arrival in Grenoble

Jean Biarez was born on September 8, 1927, in the northern French city of Lille into a family of building contractors.

After his secondary education, he came to the capital to attend a two-year preparatory school (Versailles-Sainte-Geneviève) in order to pass the competitive concours in 1949 to enter the prestigious Ecole Centrale des Arts et Manufactures (henceforth referred to as Ecole Centrale; the institution is now referred to as ECP: Ecole Centrale de Paris). After graduating in 1952 with a major in construction, he completed his military service in the French Navy. For a brief time, he worked for a newly created building inspection firm, the SOCOTEC.

At the end of 1954, he responded to a double offer of employment by the University of Grenoble’s Facultédes sciences, which was just introducing a course in soil mechanics, and the newly created SOGREAH (Sociétégrenobloise d’études et d’applications hydrauliques), which was planning to build a laboratory of soil mechanics. Nowadays, the ties between university and industry are regularly contested in France, but in the 1950s and especially in the Dauphiné region of Grenoble, this type of cooperation was considered perfectly natural. This was in part because in 1907 a major figure in civil engineering, Georges Routin, established both an experimental laboratory at the Neyret-Beylier firm in Grenoble and academic courses in hydraulics at the Institut national polytechnique de Grenoble (INPG).

A bit of historical information will help the reader grasp what was at stake in French society in the 1950s when Jean Biarez, as a young man, began his professional career.

The Second World War reduced France to a state of shambles; hence, the most vital need of the day was to produce energy. The state-owned public enterprise EDF (Electricitéde France) was given the ambitious task of building hydroelectric dams. The competence of French engineers, evident in successful projects before and even during the war, was not so extensive when it came to building earth dams. Their experience was limited to a few projects successfully completed in Algeria in the 1930s. Even this not so extensive experience was useful in building the dam in Serre-Ponçon. EDF played a crucial role in organizing and coordinating a veritable transfer of technology from engineering consulting firms, contractors and clients − especially from the United States − to the newly created soil mechanics laboratories in France.