Effect of particle shape and bedding angle on suffusion in gap-graded granular soils by coupled CFD-DEM method

The natural deposition of soils results in significant fabric anisotropy, and its influence on suffusion remains unclear. In this study, a series of gap-graded soil samples with different particle shapes and bedding angles are generated and implemented into the coupled computational fluid dynamics-discrete element method (CFD-DEM) simulations to investigate the migration of fine particles within the coarse grain matrix. Macroscopic results, including mass loss, void ratio variation, and soil deformation, as well as microscopic particle trajectory, force chain network, and contact orientation are analyzed. In addition, drained triaxial tests on samples before and after erosion are carried out. All results turn out that the greater the bedding angle, the more severe the loss of fines and the more significant the soil deformation. Three different migration characteristics can be identified according to soil anisotropy degree, that is, when the bedding angle is 0 degrees, the migration of fine particles remains relatively stable; when the bedding angle is 30 degrees and 60 degrees, the particle migration shows a gradual change throughout the erosion; when the bedding angle is 90 degrees, the fine particles migrate significantly in the very early stages of suffusion. Besides, the aspect ratio (AR) of the particle is found to be beneficial for both erosion resistance and soil strength.