Modelling of suffusion in heterogeneous soils using discrete element method

Suffusion is one of the four mechanisms of internal erosion. The embankments and their foundations can exhibit different forms of heterogeneity which can be a major factor initiating suffusion. Although several experimental studies on the effect of heterogeneities have been performed, numerical studies remain less approached. In this paper, the effect of material heterogeneity is examined using the discrete element method and the computational fluid dynamics model (DEM-CFD). The suffusion process is studied by simulating a soils sample in a column, subjected to downward flow. Heterogeneity is addressed by adding coarse particles at two-layer positions (mid-length or downstream) at three coarse fractions (20%, 40%, 60%). Its effect is investigated in terms of erodible particles, retention efficiency, and contact forces at the particle scale. In particular, the numerical simulation results show that the erosion occurs in a heterogeneous way, and the downstream configuration provides more suffusion than the central one. In addition, the introduction of coarse particles can lead to increase the filtration efficiency. The effect of involved heterogeneities on erosion depends simultaneously on the coarse fraction and configuration heterogeneity. The comparison of the numerical results with those obtained by a suffusion test shows a concordance and validates the numerical approach.