River dyke failure modeling under transient water conditions

Knowledge of the performance of river dykes during flooding is necessary when designing governmental assistance plans aimed to reduce both casualties and material damage. This is especially relevant when floods have increased in their frequency during the last decades, together with the resulting material damage and life costs. Most of previous attempts for analyzing dyke breaching during flooding have neglected to consider the soil mechanics component and the influence of infiltration and saturation changes on the failure mechanisms developed in the river dyke. This research project aimed to fill that gap in knowledge by analyzing, in a comprehensive manner, the effect of transient water conditions, represented by successive flood cycles, on the seepage conditions and subsequent breaching of dykes. Therefore, three key sub-projects were carried out: the analysis of the results from an overflow field test, the physical modeling of small-scaled models under an enhanced gravity field, the numerical modeling of the flow response and the resulting stability of both the air- and water-side slopes. The results from the numerical simulations matched accurately with the results obtained with the centrifuge modeling, including the prediction of local instabilities during the flood cycles for those dykes that did not include a toe filter.

Knowledge of the performance of river dykes during flooding is necessary when designing governmental assistance plans aimed to reduce both casualties and material damage. This is especially relevant when floods have increased in their frequency during the last decades, together with the resulting material damage and life costs.Most of previous attempts for analyzing dyke breaching during flooding have neglected to consider the soil mechanics component and the influence of infiltration and saturation changes on the failure mechanisms developed in the river dyke.This research project aimed to fill that gap in knowledge by analyzing, in a comprehensive manner, the effect of transient water conditions, represented by successive flood cycles, on the seepage conditions and subsequent breaching of dykes. Therefore, three key sub-projects were carried out:the analysis of the results from an overflow field testthe physical modeling of small-scaled models under an enhanced gravity fieldthe numerical modeling of the flow response and the resulting stability of both the air- and water-side slopes.The results from the numerical simulations matched accurately with the results obtained with the centrifuge modeling, including the prediction of local instabilities during the flood cycles for those dykes that did not include a toe filter.

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