DEM Investigation into the Effects of Liquefaction History–Induced Anisotropy on Sand Behaviors

Abstract

Many studies have verified that liquefaction histories would change sand mesostructures. However, how much the liquefaction history–induced anisotropy affects sand mechanical properties under different loading conditions remains unknown. In this study, the triaxial behaviors and coefficients of lateral earth pressure (K0) of sand specimens with different liquefaction histories were simulated by a discrete element method (DEM). The triaxial tests included monotonic drained and undrained tests and cyclic undrained tests. The K0 tests included two cases: the K0VH test was conducted using one-dimensional compression in the vertical direction, while the K0HV test was conducted using one-dimensional compression in the horizontal direction. Simulation results showed that the anisotropy induced by the liquefaction history obviously affected the initial stiffness and contraction behavior of reconsolidated sand during monotonic drained and undrained tests. Once the anisotropy degree exceeded a threshold, all the reconsolidated sand was reliquefied after only one cycle, regardless of the void ratio and applied cyclic stress ratio. The K0 test of the reconsolidated sand had a good correlation with the anisotropy degree. Reconsolidated sand with a larger anisotropy degree exhibited a more remarkable discrepancy between K0VH and K0HV. These anisotropic behaviors were intrinsically the responses of the interparticle normal contact force chains to the boundary conditions of a certain test.