Concept of suction in expansive soils

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Table of contents

1 Introduction
1.1 Reference backfill and seal concept
1.2 Motivation and objectives
1.3 Thesis layout
2 Literature review
2.1 Scale dependence in expansive soil testing
2.2 Nature of expansive soils
2.2.1 Mineralogy of expansive soils
2.2.2 Structure of expansive soils
2.2.3 Experimental determination
2.2.4 Conclusion
2.3 Interactions in clay particle – solution systems
2.3.1 Effect of pH in clay particle – solution systems
2.3.2 Hydration mechanisms
2.3.3 Crystalline swelling mechanism
2.3.4 Osmotic swelling mechanism
2.3.5 Cation exchange processes
2.3.6 Conclusion
2.4 Solution retention behavior of expansive soils
2.4.1 Concept of suction in expansive soils
2.4.2 Solution retention in expansive soils
2.4.3 Experimental determination
2.4.4 Impact of physical and physico-chemical parameters
2.4.5 Impact of compaction conditions
2.4.6 Conclusion
2.5 Compaction behavior of expansive soils
2.5.1 Experimental determination
2.5.2 Impact of physical and physico-chemical conditions
2.5.3 Relations of the compaction conditions to the structure
2.5.4 Conclusion
2.6 Swelling behavior of expansive soils
2.6.1 Experimental determination
2.6.2 Swelling pressure evolution at experimental different scales
2.6.3 Impact of physical and physico-chemical parameters
2.6.4 Impact of compaction conditions
2.6.5 Impact of environmental conditions and stress history
2.6.6 Conclusion
2.7 Compression behavior of expansive soils
2.7.1 Experimental determination
2.7.2 Impact of physical and physico-chemical parameters
2.7.3 Impact of compaction conditions
2.7.4 Impact of environmental conditions and stress history
2.7.5 Conclusion
2.8 Hydraulic conductivity behaviour of expansive soils
2.8.1 Experimental determination
2.8.2 Impact of the hydraulic gradient
2.8.3 Impact of physical and physico-chemical parameters
2.8.4 Impact of compaction conditions
2.8.5 Impact of environmental conditions and stress history
2.8.6 Conclusion
2.9 Constitutive modelling of expansive soil behavior
2.9.1 Elastic behavior
2.9.2 Loading-collapse (LC) and suction increase (SI) yield curves
2.9.3 Plastic behavior
2.9.4 Comments
2.10 Extended constitutive modelling of expansive soils
2.10.1 Basic preliminary assumptions
2.10.2 Elastic behaviour
2.10.3 Suction increase (SI) and suction decrease (SD) yield curves
2.10.4 Interaction between micro- and macrostructural levels
2.10.5 Plastic behavior
2.10.6 Comments
2.11 Conclusions and anticipated contributions
3 Combined impact of selected material properties and environmental conditions on the swelling pressure of compacted claystone/ bentonite mixtures
3.1 Introduction
3.2 Theoretical background
3.3 Materials
3.4 Methods
3.5 Results
3.6 Discussion
3.6.1 Introduction of expansive mineral dry density (EDD)
3.6.2 Impact of expansive mineral content and grain size distribution
3.6.3 Individual impact of EDD and solution chemistry
3.6.4 Combined impact of solution chemistry and EDD
3.7 Conclusions
4 Hydraulic conductivity, microstructure and texture of compacted claystone/ bentonite mixtures saturated with different solutions
4.1 Introduction and background
4.2 Materials
4.3 Experiments
4.3.1 Sample preparation
4.3.2 Hydraulic conductivity
4.3.3 Microstructural analysis
4.3.4 Textural analysis
4.3.5 Experimental program
4.4 Results
4.4.1 Hydraulic conductivity experiments
4.4.2 Microstructural analysis
4.4.3 Textural analysis
4.5 Discussion
4.5.1 Textural analysis
4.5.2 Microstructural analysis
4.5.3 Hydraulic conductivity experiments
4.6 Conclusions
5 Hydro-mechanical path dependency of claystone/ bentonite mixture samples characterized by different initial dry densities
5.1 Introduction
5.2 Material
5.2.1 General characteristics
5.2.2 Microstructural characteristics
5.2.3 Water retention characteristics
5.3 Oedometer and constant-volume swelling pressure experiments
5.3.1 Approach
5.3.2 Sample preparation
5.3.3 Suction-controlled oedometer experiments
5.3.4 Suction-controlled constant-volume swelling pressure experiments
5.3.5 Hydro-mechanical paths and experimental program
5.4 Results
5.4.1 Suction-controlled oedometer experiments
5.4.2 Suction-controlled constant-volume swelling pressure experiments
5.5 Discussion
5.5.1 Compression behavior
5.5.2 Swelling behavior
5.5.3 Comparison of yield behavior
5.6 Conclusions
6 Conclusions and perspectives
6.1 Approaches
6.2 Synthesizes and conclusions
6.3 Perspectives
A Supplementary material
References