Mechanical Consequences of Suffusion on Gap-Graded Soils with Stress Anisotropy: A CFD–DEM Perspective

Natural soil in geotechnical engineering is commonly in the anisotropic stress state, but the effect of stress anisotropy on soil suffusion remains unclear. In this study, the coupled computational fluid dynamics–discrete element method was utilised to simulate the complete suffusion process of gap-graded soils by introducing a vertical seepage flow through the soil assembly. The mechanical consequences of suffusion on gap-graded soils were evaluated by comparing the triaxial shear responses of soil specimens before and after suffusion. The results indicated that the specimens with greater stress anisotropy are more vulnerable to suffusion, particularly those with the principal stress that is coincident with the principal flow direction. Compared with the isotropically consolidated specimens, the specimens with greater stress anisotropy exhibited more pronounced reduction in shear strength and secant stiffness after suffusion. The effects of stress anisotropy on the suffusion and mechanical properties of gap-graded soils were also evaluated from a microcosmic perspective in terms of force chain, coordination number, and fabric tensor.