Numerical analysis of suffusion behavior under cyclic loading with coupled CFD-DEM simulation

Cyclic loading has a significant effect on soil properties and seriously threatens geotechnical engineering. However, the influence of cyclic loading on the suffusion in gap-graded granular soils remains unclear up to now. In this study, systematical numerical simulations of suffusion in soil samples subjected to triaxial compression are performed with the coupled computational fluid dynamics (CFD) and discrete element method (DEM) approach, i.e., the coupled CFD-DEM. The method is able to simulate the suffusion process in gap-graded soils under cyclic loading and reveal the evolution of fluid fields. The suffusion of gap-graded soil sample is achieved by imposing a downward seepage flow. The results indicate that, cyclic loading induces greater erosion mass and fluid velocity during the suffusion process, as 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 it only lasts for a very short of time. Then, the particle loss rate slows down and enters the second stage. In this stage, compared to the non-vibration sample, the sample subjected to cyclic loading still has a large eroded mass, which persists until the end of the simulation. The sensitivity analysis indicates 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.