This thesis documents the development of a simulation strategy to model the behavior of geomembranes at large deformations using the explicit finite difference code FLAC3D. The geomembrane is represented by special shell elements and interfaces at both sides of the geomembrane duplicating the interaction with the overlying and underlying materials. Chapter 1 provides an introduction to geotextiles and geomembranes, and their use in geotechnical engineering. Special attention is paid to pull-out tests because of their importance to describe the behavior at large deformations. Chapter 2 describes the proposed ‘liner’ model concept to simulate the interaction of a geomembrane with the over- and underlying material. Furthermore, this chapter documents in detail the simulation of uniaxial pull-out tests for validation of the proposed ‘liner’ model concept and compares it with the FLAC3D built-in geogrid element. To clarify more clearly the potential failure (crack propagation and rupture process) of the geomembrane, the ‘liner’ model under biaxial loading was investigated in Chapter 3. Chapter 4 documents a detailed parameter study with a special focus on the stiffness and frictional behavior of the ‘liner’ element using a simplified waste dump. In chapter 5 a new constitutive model (“Femesalz”) is proposed to describe the visco-elasto-plastic behavior of crushed salt and waste rock salt, respectively. The “Femesalz” constitutive model together with the ‘liner’ model is applied to simulate the behavior of a rock salt waste dump (2.5-dimensional) to validate both, the new constitutive model “Femesalz” as well as the ‘liner’ model. Chapter 6 documents the use of the ‘liner’ element and the “Femesalz” constitutive model to simulate salt dump models in 2D and 3D on different terrain types (mountain, valley, plain) for a time of 100 years to generate large deformations.
Chapter 7 contains the main conclusions and recommendations.:ABSTRACT AND STRUCTURE OF THESIS 2
ACKNOWLEDGMENTS 4
CONTENTS 5
LIST OF TABLES 7
LIST OF FIGURES 10
NOMENCLATURE 16
CHAPTER 1: INTRODUCTION AND STATE-OF-THE-ART 22
1.1 Geosynthetic for geoengineering projects (overview) 22
1.2 Pull-out tests (overview) 29
CHAPTER 2: “LINER” CONCEPT AND NUMERICAL SIMULATIONS OF UNIAXIAL PULL-OUT TESTS 39
2.1 Introduction 39
2.2 Numerical calculations 39
2.2.1 General considerations 39
2.2.2 Concept of the 'liner' element 40
2.2.3 'Geogrid' versus 'liner' element 41
2.2.4 Verification of ‘liner’ element 42
2.2.5 Conclusions 58
CHAPTER 3: BIAXIAL LOADING OF “LINER” MODEL 61
3.1 Introduction 61
3.2 Model set-up 61
3.3 Results of biaxial pull-out test simulation 63
3.4 Summary and Conclusions 71
CHAPTER 4: PARAMETER STUDY OF EMBEDDED GEOMEMBRANE 74
4.1 Introduction 74
4.2 Model set-up 74
4.3 Results 77
4.3.1 Influence of interface stiffness 80
4.3.2 Influence of interface friction 87
4.4 Conclusions 93
CHAPTER 5: CONSTITUTIVE MODEL FOR SALT DUMP 95
5.1 Introduction 95
5.1.1 Overview of constitutive models for rock salt 97
5.1.2 Overview of constitutive models for crushed salt 104
5.2 ‘Femesalz’ constitutive model for crushed salt 106
5.2.1 Introduction 106
5.2.2 Compaction test 111
5.2.3 Triaxial test and realistic waste dump simulation 114
5.2.4 Numerical salt dump simulations 115
5.3 Summary 122
CHAPTER 6: SIMULATIONS CONSIDERING TOPOGRAPHY OF UNDERLYING MATERIAL 123
6.1 Introduction 123
6.2 Model set-up 123
6.3 Model parameters and calculation sequence 131
6.4 Calculation results 132
6.5 Discussion of results and conclusions 139
CHAPTER 7: CONCLUSIONS 141
REFERENCE 143
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:87659 |
| Date | 24 January 2024 |
| Creators | Nguyen, Vinh Duc |
| Contributors | Konietzky, Heinz, Katzenbach, Rolf, Nguyen, Van Manh, Technische Universität Bergakademie Freiberg |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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