Study on the Deformation of Loose Sand under Cyclic Loading by DEM Simulation

The extensive use of granular materials as roadbeds accelerates the study of sand behavior under cyclic loading. While several studies have been done on sand deformation under cyclic loading, little information is available on the explanations for this behavior. By discrete element method (DEM) simulation, this paper offered a preliminary insight into particles interaction of loose sand which controls the material's stress-strain behavior. A 2-D `sample' of 896 `quartz' disks, with diameters of 0.20, 0.25 and 0.30mm, was produced by self-gravity sediment. Then it was K₀ loaded to t' = 127 kPa, at which point, the sample started to be cyclically loaded for 5000 cycles when t' kept constant. Cyclic amplitudes varied from 0.02 to0.04 t'. Increasing strain accumulation with increased number of cycles was observed. For smaller cyclic amplitude, strain accumulation increased smoothly, but for larger one, strain accumulation increased erratically after a large number of cycles. The coordination number variation during cycling load was considered to be responsible for this phenomenon. Induced anisotropy was observed, and it could be explained by deviatoric fabric analysis.