Exploring the Undrained Cyclic Behaviour of Sand Using DEM

This paper investigates the influences of confining pressure and cyclic deviatoric stress on the undrained cyclic loading behavior of saturated granular materials using DEM. Cyclic mobility, which is typical for sand under cyclic loading conditions in the absence of initial deviatoric stress, is captured. DEM simulation results show that the number of loading cycles to initial liquefaction increases with increasing confining pressure but decreases as cyclic deviatoric stress increases. Cyclic mobility is characterized by alternating abrupt drops and gains of coordination number accompanied by alternating abrupt decreases and increases of deviatoric fabric. The runaway deformation can be either compressive or extensive depending on whether the instability state under monotonic compression loading conditions or that under monotonic extension loading conditions is reached first during cyclic shearing.