Effect of non-erodible particle content on the mechanism of suffusion and the evolution of permeability of sandy soil

Suffusion is a typical type of internal erosion that is an important factor leading to the failure of dams and dikes. In this paper, fine particles are divided into erodible particles and non-erodible particles, and the soil suffusion mechanism is investigated by laboratory tests and CFD_DEM simulations when the content of erodible particles (F_c) and non-erodible particles (F_z) is 15% and 5%, 10% and 10%, and 5% and 15%. The global mean permeability coefficient (k_av) and local permeability coefficient (k_i–j) were calculated by monitoring the water head in the seepage path of the sample. The results show that with increasing non-erodible particle content, the difficulty of soil suffusion increases gradually. When soil suffusion occurs, the loss of fine particles starts from the seepage outlet area and the influent area, and the non-erodible particles have little influence on the particle loss process in these two areas. After the occurrence of suffusion, the number of weak contact chains is obviously reduced, while the strong contact chains are basically stable. When F_z = 5% and F_z = 10%, the average permeability coefficient of the soil after suffusion expands to 2.21–1.60 times that of the initial state, and the corresponding values of the CFD_DEM simulation are 2.14–1.86 times.