Erosion of Geomaterials E-Book

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

Seitenzahl: 599

Veröffentlichungsjahr: 2012

Beschreibung

This book aims to deliver significant scientific progress on the problem of the erosion of geomaterials, focusing on the mechanical/physical aspect. The chapters oscillate between a phenomenological outlook that is well grounded in experiments, and an approach that can offer a modeling framework.
The basic mechanisms of internal and surface erosion are tackled one-by-one: filtration, suffusion, contact erosion, concentrated leak erosion, sediment and wind transport, bedload transport. These erosion mechanisms comprise both hydraulic structures (dams, dikes) and natural environments (wind, river, coastal).

In this book, physicists and mechanicians share with the reader their most recent findings in their field work and study, while at the same time maintaining an accessible format. This compendium provides a well-documented information resource, and above all, a tool for approaching the issue of erosion of geomaterials in an up-to-date fashion for students, researchers and practitioners alike.

Leseprobe

Table of Contents

Foreword

Introduction

Chapter 1. Introduction to the Process of Internal Erosion in Hydraulic Structures: Embankment Dams and Dikes

1.1. Introduction

1.2. The significance of internal erosion for hydraulic structures

1.3. The impact of incidents on embankment dams and dikes

1.4. Main results of erosion trials

1.5. Remarks on the applicability of erosion trials

1.6. Conclusion

1.7. Bibliography

Chapter 2. Suffusion, Transport and Filtration of Fine Particles in Granular Soil

2.1. Introduction

2.2. Dominant parameters that influence suffusion

2.3. Main initiation criteria for suffusion

2.4. An initiation criterion formulated using a geohydromechanical approach

2.5. The scaling effect and the energetic approach

2.6. Coupling the phenomena of suffusion and filtration-clogging

2.7. Processes causing filtration

2.8. Filtration modeling

2.9. Confrontation between the laboratory filtration tests and the modeling

2.10. Filtration and clogging

2.11. Conclusion

2.12. Bibliography

Chapter 3. The Process of Filtration in Granular Materials

3.1. Introduction

3.2. Fundamental characteristics of the filtering granular media

3.3. The distribution of constriction size

3.4. A probabilistic approach of constriction sizes

3.5. Diameter of control constrictions

3.6. A continuous approach of the process of filtration

3.7. Conclusion

3.8. Bibliography

Chapter 4. Contact Erosion between Two Soils

4.1. Introduction

4.2. Areas prone to CE in hydraulic structures

4.3. Description of CE mechanisms on a local scale

4.4. CE of a fine soil under a coarse soil

4.5. CE of a fine soil on a coarse soil

4.6. Possible scenarios that may lead to failure of a hydraulic structure

4.7. Conclusion and perspectives

4.8. Bibliography

Chapter 5. Concentrated Leak Erosion

5.1. Introduction

5.2. General points

5.3. The device and the protocol of the HET

5.4. Methods of interpretation

5.5. Effect of different soil parameters on erosion

5.6. Importance of the erosion index for hydraulic structures

5.7. Conclusion

5.8. Bibliography

Chapter 6. Modeling of Interfacial Erosion

6.1. Introduction

6.2. Modeling of a two-phase medium

6.3. Modeling of the soil/fluid interface

6.4. Modeling of flow with erosion

6.5. Numerical modeling

6.6. Validation of numerical models

6.7. Illustrative examples

6.8. Conclusion

6.9. Bibliography

Chapter 7. Physics of Sediment and Aeolian Transport

7.1. Introduction

7.2. Static transport threshold

7.3. Aeolian transport

7.4. Quantitative description of transport

7.5. Linear stability analysis of a flat erodible bed

7.6. Conclusion

7.7. Acknowledgments

7.8. Bibliography

Chapter 8. Two-Phase Modeling of Bedload Transport

8.1. Introduction

8.2. Incipient motion

8.3. Bedload transport

8.4. Conclusion and outlook

8.5. Acknowledgments

8.6. Bibliography

Chapter 9. Characterization of Natural Cohesive Sediments and Water Quality of Rivers

9.1. Introduction

9.2. Behavior of pollutants in rivers

9.3. Erosion of fine cohesive sediments

9.4. Experimental characterization

9.5. Example of operational application

9.6. Conclusion

9.7. Bibliography

Chapter 10. Sediment Transport and Morphodynamics in Nearshore Areas

10.1. Introduction

10.2. Marine sediments

10.3. Sediment transport

10.4. Sediment structures and morphodynamic structures

10.5. Local effects: scouring around the structures

10.6. Long-term morphodynamics of beaches

10.7. Conclusion

10.8. Bibliography

List of Authors

Index

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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The rights of Stéphane Bonelli to be identified as the author of this work have been asserted by him in accordance with the Copyright, Designs and Patents Act 1988.

Library of Congress Cataloging-in-Publication Data

Erosion of Geomaterials / edited by Stéphane Bonelli.

p. cm.

Includes bibliographical references and index.

ISBN 978-1-84821-351-7

  1. Sediment transport. 2. Soil erosion. 3. Levees--Protection. 4. Dam failures--Prevention. I. Bonelli, Stéphane.

TC175.2.E76 2012

  627′.8--dc23

2012016138

British Library Cataloguing-in-Publication Data A CIP record for this book is available from the British Library

Foreword

Soil erosion, be it internal erosion or surface erosion, is the main mechanism responsible for disorders or failures of civil engineering structures. These failures usually take place as soon as the soil, which constitutes either the entire engineering structure or only its foundation, comes into contact with water flows. The affected engineering structures are usually reservoir dams, canals, flood-protection dikes (structures that we will be referring to under the umbrella term “hydraulic structures”); as well as bridges, flood-protection dams, and engineering works carried out with the purpose of stabilizing coastlines.

This is the broad scope of this present compendium. Furthermore, this compendium is part of a twofold context: on the one hand, the need for improving the safety concerns regarding these engineering structures, and on the other hand, the significant research programs performed on erosion, whether these were recently carried out or are currently underway.

The regulations applied to hydraulic structures have been recently reinforced in France and they have been adapted according to the stakes involved in case of failure. These regulations insist on the necessity of assessing the safety level of these structures, particularly through risk analyses, as well as on strengthening their supervision. These regulations will apply in France from now on to 700 “large” dams, tens of thousands of small dams, approximately 8,000 km of canal dikes, and around 10,000 km of dikes and levees meant to protect against flooding or marine submergence.

The consequences that climate change is likely to have on the sea level as well as on continental hydrology will lead to increasing demands on coastline and fluvial dikes and levees. This, in turn, brings about the need for evaluating their safety and, should they fail that evaluation, the need to reinforce safety measures.

In recent years, these issues that are at stake have justified a strong mobilization on the part of the scientific community, which structured itself around several research projects, both on national and international levels. In France, we should mention the GdR MiDi and MeGe and the projects ERINOH, Dunes, and Carpeinter, to name only the most important projects.

This compendium is mainly concerned with the results of such research works; it aims to answer the queries of those responsible with the management of the civil engineering works that we have mentioned above.

Paul ROYET

June 2012

Introduction

The question of the natural risks involved in soil erosion remains a very active subject. The complexity of this issue is linked to multi-scale and multi-physics couplings, to the time durations involved, and to the highest quality required. This research is linked to the multidisciplinary character of many of the remaining questions. These subjects are dominated by safety and environmental protection concerns.

While an old issue, soil erosion remains so far an “open” problem. A great number of research works that deal with soil erosion are published regularly. This question is most often approached either on large spatial scales, from a hydrological and geomorphological viewpoint, or on a smaller scale, from a hydraulic perspective. On the contrary, the mechanical/physical approach of this subject, though it has been developed in scientific journals, has not yet motivated a reference work.

This compendium aims to deliver a significant part of the current French scientific progress on the problem of the erosion of geomaterials, with a focus on the mechanical/physical aspect, while targeting a twofold objective – coherence and pedagogy. This work does not pretend to be thorough on such an age-old, multidisciplinary, and highly debated subject. In this respect, the contributions oscillate between a phenomenological outlook that is well grounded in experiments and a mechanical/physical approach that can offer a modeling framework.

The outline of this work is structured as follows: the first five chapters, are dedicated to the phenomenon of internal erosion. Once the internal erosion has been introduced within the framework of hydraulic structures (embankment dams and dikes), the basic mechanisms of internal erosion will be tackled one-by-one. The last five chapters, deal with surface erosion. Interfacial surface erosion and sediment transport as well as bedload transport are examined from different perspectives and in different situations (aeolian, fluvial, coastline). Each chapter is concerned with two crucial aspects: the motion threshold, in connection with the critical stress force, and the flow of the eroded and transported matter, that sometimes includes a coefficient of erosion. This is the common thread that underpins this work.

The geomaterials we will be concerned with are mainly soils and sediments. The interactions are especially of mechanical origin, but several complex interactions, of physical-chemical origin are also considered. Throughout the chapters, the authors will highlight the different kinds of geomaterial erosion we may experience, at the same time trying to extract the practical consequences that are of interest to a practitioner.

Chapter 1, written by Jean-Jacques Fry, is an introduction to internal erosion as it presents itself in hydraulic structures: dams and dikes. The importance of this issue is proven by the feedback gathered from various incidents. The main results of erosion tests and their applicability are summarized and they set the tone for the next chapters.

In the second chapter, Didier Marot and Ahmed Benamar tackle a difficult problem that is likely to come up in hydraulic structures: suffusion, i.e. the transport and the filtration of fine particles in a granular soil. The significant parameters and the suffusion initiation criteria are analyzed and discussed. Subsequently, the migration of fine particles and their filtration is examined.

Eric Vincens, Nadège Reboul and Bernard Cambou are the authors of Chapter 3. They too deal with the process of filtration in granular materials, but this time from a micro-mechanical perspective, using a fine modeling scheme that is both theoretical and numerical, by means of the discrete element method. At the end of the chapter, by returning to the scale of a continuous medium, new perspectives are opened for the modeling of hydraulic structures.

In Chapter 4, Rémi Béguin, Pierre Philippe, Yves-Henri Faure and Cyril Guidoux devote their attention to a still under-researched mechanism of erosion, but which can be found in numerous dikes: contact erosion between two types of soil. The description of the mechanisms that take place at grain level allows for a better understanding of the conditions under which they occur as well as of the kinetics of erosion. Finally, several possible scenarios that might lead to a failure of hydraulic structures are suggested.

Chapter 5, written by Nadia Benahmed, Christophe Chevalier and Stéphane Bonelli, is concerned with flow erosion as it takes place in a pipe. In fact, this chapter thoroughly analyzes the “Hole Erosion Test”, which was carried out for hydraulic structures in the United States and Australia, and recently in France. Several laboratory tests show the influence on erosion parameters of the clay nature, of the soil water content, and of its density. Finally, this chapter emphasizes the importance of the coefficient of erosion needed to evaluate the safety of hydraulic structures in relation to the risks of failure caused by pipe flow with erosion.

In Chapter 6, Stéphane Bonelli, Frédéric Golay and Fabienne Mercier present an original modeling of interfacial surface erosion. The modeling of a two-phase flow with erosion and transport is simplified, and two numerical models are proposed: one of them is based on the fictitious domain method and the level-set method, while the other is based on remeshing. Several examples of validation and illustration are presented, with wide applicability to laboratory tests.

In Chapter 7, we enter the field of sediment transport physics. Using a fundamental approach, Bruno Andreotti and Philippe Claudin open up new perspectives regarding the erosion law. The authors show us what are the scaling laws that govern transport thresholds, sand flux saturation length, and what is the wavelength at which an erodible bed is destabilized. It becomes apparent that, contrary to naturalistic classifications, we must take aquatic sand ripples, aeolian dunes and the giant Martian dunes to be of the same type.

In Chapter 8, Pascale Aussillous, Elisabeth Guazzelli and Yannick Peysson prefer a continuous two-phase medium approach for the modeling of bedload transport. Two essential aspects are examined: the setting into motion threshold and the transported sediment flow. The closure laws proposed in a laminary situation allow us to obtain a smooth agreement between modeling and experimentation. In particular, it is demonstrated that the motion threshold that corresponds to the critical number of Shields mainly depends on a friction coefficient of the granular medium and its compactness.

Chapter 9 is dedicated to natural cohesive sediments within the context of the quality of water streams. This chapter is written by Fabien Ternat, Patrick Boyer, Fabien Anselmet and Muriel Amielh. Having introduced the behavior of pollutants in water streams, the authors have carefully analyzed the erosion of fine cohesive sediments both theoretically and experimentally. Finally, for illustrative purposes, the authors provide us with the example of radioactive contamination of the river Techa in Russia.

The tenth and final chapter branches out to the crucial matter of sedimentary and morphodynamic transport in coastal areas and along the shoreline. In this chapter, Vincent Rey and Damien Sous write successively about marine sediments, sedimentary transport, sedimentary and morphodynamic structures, as well as the scouring around these structures. This chapter ends with a presentation of the modeling of beach and coastline morphodynamics in the long-term range.

More than half of these chapters are a result of the research carried out over several years within the ERINOH Project – French Research Agency (ANR) Project and National Project – coordinated by the Institute for Applied Research and Experimentation in Civil Engineering (IREX). This compendium equally integrates the results from several other research projects: Dunes and Carpeinter, Zephyr (both financed by the ANR), PEA ECORS (SHOM) and MICROLIT (INSU-RELIEFS), Project Scale of GRR SER from the Haute Normandie Region of France. Finally, throughout the years, the two GdR CNRS MiDi and MeGe have brought together the majority of the present authors.

To conclude, I wish to express my gratitude to M. François Nicot, editor, for the confidence he has given me. I also wish to warmly thank the authors of these chapters, who have generously offered their time and shared their expertise in writing up this compendium.

Our aim in this book has been to provide a means for physicists and engineers to share with the reader their most recent findings in their field, while at the same time maintaining an accessible format. We hope that the reader finds in this compendium a well-documented information resource, and above all, a key for approaching the issue of erosion of geomaterials in an up-to-date manner.

Chapter 1

Introduction to the Process of Internal Erosion in Hydraulic Structures: Embankment Dams and Dikes1

1.1. Introduction

The first part of this book presents the initial results of the National Project ERINOH (the acronym for Erosion Interne des Ouvrages Hydrauliques, i.e. Internal Erosion of Hydraulic Structures) and this chapter provides a general introduction to the problem. What is this lesser known pathology that can seriously damage the safety of such hydraulic structures as embankment dams, dikes, and canals? So far, there has been a strong imbalance in the way academics have presented the physical phenomena that govern the maintenance of hydraulic structures.

Relevant textbooks place the emphasis on the mechanical analysis of general stability, although stability is only marginally involved in the majority of incidents and failures. Consequently, this chapter aims to provide several basic elements that are necessary to understand and analyze the complex hydraulic phenomena that, under changeable circumstances, bring into play the interactions between water and porous media. The main objective of this chapter is to render familiar the knowledge we have obtained so far, thus offering a more global and easier reading of the chapters that follow.

1.2. The significance of internal erosion for hydraulic structures

1.2.1. The set of hydraulic structures in France

France disposes of a significant stock of hydraulic structures. The linear lengths of dikes are roughly equivalent to 13 times the largest dimension of its territory, with more than 9,000 km of protection against flooding, 8,000 km of dikes for navigation canals, and 1,000 km of hydroelectric canals. The number of small embankment dams, whose height does not surpass 15 m, is around several tens of thousands, while the number of large dams approaches 600.

While the first characteristic of French hydraulic assets is their amplitude, the second characteristic is their age: most dikes are more than 100 years old and most dams are older than half a century. Finally, the predominance of natural materials used in the backfilling of these dams is the third characteristic.

The maintenance of such a wide patrimony, both old and built with local materials, requires a costly and decentralized upkeep, which is difficult to achieve in an economically restrictive context. This, in turn, poses a problem for exploitation safety, and hence the need for innovative and economical solutions.

Hydraulic structures are civil engineering structures whose function is to retain or transport water. Apart from being a natural resource, water is also a kind of fluid energy. Because it stands in the way of the water, a hydraulic structure must constantly fight against this energy, which can take advantage of the slightest fault in order to break loose. Consequently, following the example of the International Commission On Large Dams (ICOLD), we have regarded the loss of this main function of the hydraulic work as a failure.

1.2.2. The vulnerability of hydraulic structures

The dams are either built of natural materials without using any binder (backfill) or of materials that are reinforced using hydraulic binders (i.e. lime in the first gravity dams that were built using masonry, and then cement, fly ash, or slag cement in the case of concrete dams). The statistical data gathered by the International Commission on Large Dams (1995), presented in Table 1.1, emphasizes the fact that backfill dams make for more vulnerable structures than concrete or masonry dams. However, this table does not include the more fragile backfill dams that make up the flood-protection dikes whose failures hit the headlines during large floods.

Table 1.1.Number of failures/year/dam in the world (excluding China) from 1970 to 1990 according to ICOLD (1995)