Centrifuge modelling of ground improvement for double porosity clay

Double porosity soil is characterised by a soil continuum containing two distinct porosities. Typically, this consists of macro-grains (lumps) of soil that have an internal porosity defined as the intragranular porosity. The spaces between lumps are identified as intergranular voids that give rise to the intergranular porosity. Human activities such as land reclamation or mining can give rise to large areas of land with subsoil that exhibits double porosity. The need to build in, or on, these areas is increasing, due to demand for land for industrial usage, infrastructure, and residence. However, the engineering properties of such soils are challenging, and often difficult to predict due to their inhomogeneity and a lack of information about the initial or current parameters. Double porosity mining waste landfills in Northern Bohemia in the Czech Republic were studied in this project. There, decades of open-cast mining of brown coal have left vast areas of land affected by the waste overburden that has been removed and dumped in old mining pits. Redevelopment of areas affected by mining sometimes requires construction on old overburden waste spoil heaps, which consist primarily of lumps of overconsolidated clay and are therefore characterised by a double porosity soil structure. The loading response on these clayfills entails large absolute and relative deformations, which means that ground improvement is normally needed before construction begins, to ensure that both stability and service limit state requirements are met. The primary aim of this research was a comparison, through physical modelling, of ground improvement techniques on double porosity clay landfills. A secondary objective was to contribute to the understanding of the material behaviour governing response to loading and other processes on double porosity soil.

Inhalt
1;Centrifuge modelling of ground improvement for double porosity clay;1
2;Imprint;4
3;Foreword;5
4;Acknowledgments;7
5;Contents;9
6;Kurzfassung;15
7;Abstract;17
8;1 Introduction;19
8.1;1.0 Motivation;19
8.2;1.1 Context of research;20
8.3;1.2 Aims, methodology, and structure of the study;21
9;2 Literature review;23
9.1;2.0 The challenge: landfills and ground improvement;23
9.2;2.1 Double porosity soil;29
9.3;2.2 Mining waste landfills in the Czech Republic;37
9.4;2.3 Centrifuge modelling;42
10;3 Laboratory testing;55
10.1;3.0 Material;55
10.2;3.1 Parameter tests;55
10.3;3.2 Mini centrifuge tests;57
10.4;3.3 Material preparation method for large centrifuge tests;63
10.5;3.4 Oedometer testing to establish effect of saturation ratio on onedimensional compression;66
10.6;3.5 Summary;71
11;4 Centrifuge testing;73
11.1;4.0 Introduction;73
11.2;4.1 Series 1: Scoping tests;89
11.3;4.2 Series 2: Embankments;116
11.4;4.3 Series 3: Sand compaction piles (SCPs);134
11.5;4.4 Series 4: Dynamic compaction;169
11.6;4.5 Discussion of centrifuge modelling challenges;195
12;5 Discussion;199
12.1;5.0 Introduction;199
12.2;5.1 Implications for the soil structure;199
12.3;5.2 Foundation tests;207
12.4;5.3 Effect of ground improvement measures;211
12.5;5.4 Performance in practice - recommendations;215
13;6 Conclusions and outlook;217
13.1;6.0 Summary of experimental conclusions;217
13.2;6.1 Outlook and recommendations;220
14;7 References;223
15;8 Appendix 0: Lists of Figures and Symbols;229
15.1;8.0 List of Figures;229
15.2;8.1 List of Symbols;239
16;9 Appendix 1: Data plots;240
16.1;9.0 Series 1;240
16.2;9.1 Series 2;243
16.3;9.2 Series 3;246
16.4;9.3 Series 4;256
16.5;9.4 Chapter 5;261
17;10 Appendix 2: Positions of PPTs after centrifuge tests;264
18;Curriculum Vitae;267