Numerical simulations of overflow experiments on a model dike

Witold Tisler,Rafał Ossowski,Wioletta Gorczewska-Langner,Marcin Cudny,Adam Szymkiewicz,K Wilde,M Niedostatkiewicz

doi:10.1051/matecconf/201926201003

Abstract

Dike failure due to overtopping is one of the important factors, which should be considered in the dike designing process. Although the overflow is characterized by the relatively low risk of occurrence, in many cases dikes are totally destroyed or seriously damaged. An interesting phenomenon occurring during overflow is the trapping of air in pores of the unsaturated soil material. As the infiltration progresses from all sides, the air pressure in the unsaturated region increases, which may ultimately lead to damage of the dike structure. It happens when the air is expulsed in form of bursts and forms large macropores. Such a behaviour evidenced in laboratory experiments. In this study we attempt to simulate the evolution of stress field in the model dike subjected to overtopping. The results are in qualitative agreement with observations, showing that formation of the first macropores occurs in the direction perpendicular to the minor principal stress in the soil mass along the dike slope edge.

Highlights

Dikes are usually build along the rivers to protect inhabited areas from floods
Numerical simulations [12] showed that the evolution of air pressure in the model dike can be successfully represented with a two-phase flow model
We expect the actual values of the effective stress to be different from the computed ones, since the numerical model did not take into account the influence of the pore air pressure

Summary

Introduction

Dikes are usually build along the rivers to protect inhabited areas from floods. The existence of the dike retaining water is always connected with the risk of their failure which can be disastrous and cause huge economic losses. In the second case a large unsaturated (i.e. mostly air-filled) area surrounded by the water-saturated material is created Both phenomena are connected with the loss of macroscopic homogeneity which is undesirable in dike structures [8, 9, 10, 11]. One of the interesting findings was the appearance of large voids (macropores) during air entrapment (Fig. 1 and Fig. 2), resulting from an increase of the pore air pressure in the unsaturated zone (up to about 0.65 kPa over the atmospheric pressure) This type of void was observed in earlier experiments, carried out on a slightly different dike configuration [6, 12]. The obtained information on the total and effective stress field can be useful for the analysis of the macropore formation

Experiment

Numerical model

Discretization and boundary conditions

Results

Conclusion

14. Documentation of the Zsoil software