DEM simulation of collapse behaviours of unsaturated granular materials under general stress states

In this study, a numerical simulation of true triaxial tests was conducted using the three-dimensional distinct element method (DEM) in order to examine how unsaturated granular materials collapse under general stress states. The collapse process was simulated by reducing the intergranular adhesive forces corresponding to the effect of the capillary suction during the isotropic compression and the shearing processes under general stress states. Based on the relationship between the void ratio and the mean principal stress after collapsing, it was found that the initially soaked compression line obtained with an inundation test may be used to predict the collapse of granular materials under a general stress state. From the analysis for the fabric tensor in the particle aggregate after collapsing, the skeleton structures became identical to those in which no intergranular adhesive force was applied. Furthermore, even though the collapse process was simulated under a plane strain condition, the shear band inside the sample did not occur clearly, and the slippage between particles was instead induced randomly during collapsing.