NUMERICAL ANALYSIS OF SUFFUSION BEHAVIOR UNDER CYCLIC LOADINGWITH COUPLED CFD-DEM SIMULATION

Abstract

Cyclic loading has a significant effect on soil properties and seriously threatens geotechnical engineering. However, it remains unclear how cyclic loading affects the suffusion behavior in gap-graded granular soils. In this study, we performed systematic numerical simulations of suffusion in soil samples subjected to triaxial compression coupled with computational fluid dynamics (CFD) and discrete element method (DEM) approaches, i.e., coupled CFD-DEM. The proposed method is able to simulate the suffusion process in gap-graded soils under cyclic loading and reveal the evolution of the fluid fields. The suffusion of gap-graded soil samples was achieved by imposing a downward seepage flow. The results indicated that cyclic loading induces greater erosion mass and fluid velocity during the suffusion process compared to simulations under fixed external forces. The erosion curve can be divided into two stages. In the first stage, the particle loss rate is high, but only lasts for a very short period of time. Then, the particle loss rate slows down and enters the second stage. In this stage, compared to a non-vibrating sample, the sample subjected to cyclic loading still has a large eroded mass, which persists until the end of the simulation. The sensitivity analysis indicated that the first stage of suffusion is more sensitive to an increase in vibration amplitude, whereas the second stage is more responsive to an increase in frequency.