DEM Models of Toyoura Sand Under Various Cyclic Loading Paths From Direct Considerations of Shape and Fabric

Accurately matching discrete element model (DEM) simulations with experimental data under various loading paths, including cyclic tests, remains a significant challenge. In this study, two 3D-DEM models with different grain shape descriptions (either irregular polyhedra or spheres) are employed to reproduce the cyclic behavior of Toyoura sand. The DEM samples are prepared using a specific technique to mimic the air-pluviation method used in laboratory tests. Both DEM models were calibrated and validated using various monotonic tests in a previous study before being applied to cyclic tests for further validation. Various cyclic stress paths are tested, including drained cyclic constant-pressure triaxial, undrained cyclic triaxial, and undrained simple shear tests. The results demonstrate that both particle shapes and fabric initial anisotropy are two crucial factors for accurately reproducing the cyclic behavior of soils. The simulation results of different cyclic tests using the polyhedral DEM model show remarkable agreement with the corresponding experimental data for Toyoura sand, not only in terms of the number of cycles required for liquefaction, but also in terms of qualitative evolution at different stages of the tests. However, less efficient prediction is observed for the spherical DEM model.