Micromechanical analysis of suffusion in gap-graded granular soils considering soil heterogeneity and non-uniform seepage flow

Abstract

The dams and their foundations can exhibit different forms of heterogeneity and experience non-uniform seepage flow, significantly affecting the suffusion. Although experimental studies on the effect of heterogeneities have been performed, their micro-mechanics remain unclear. For this reason, systematic simulations considering various soil heterogeneity configurations and flow fields are performed using the coupled CFD-DEM approach. Layered samples with different initial fines content and density are generated and analysed. The effect of flow paths is investigated for 3D conditions in conjunction with partially permeable boundary conditions and initially blocked zone in the samples. The obtained macro-responses are presented and interpreted from the micromechanical perspectives. The primary influential factors of the sample's susceptibility to suffusion are identified as the migration distance, flow field characteristics, cutoff wall position, and the number of fine particles in the weak force chain network. The sample is more prone to suffusion when there are more fine particles in the weak force chain or near the flow outlet. The flow rate has a positive effect on the cumulative eroded mass for different flow fields. The cutoff wall downstream is more effective in retaining the fine particles.