DEM analysis of isotropic compression tests on remolded and structured unsaturated loess

The macroscopic and microscopic mechanical responses of remolded and structured unsaturated loess are investigated under isotropic compression using the distinct element method (DEM). A three-dimensional (3D) cementation contact model developed for unsaturated structural loess is employed in the DEM with its parameters calibrated from the true triaxial tests on Chinese loess. After preparing the numerical unsaturated remolded and structured loess specimens, the isotropic compression tests are carried out. The DEM results show that the simulation can reproduce qualitatively the main mechanical behavior of the loess. The void ratio of unsaturated loess decreases slowly at first with the mean stress, and then begins to transit to a rapid reduction near the yield stress. When the mean stress of a certain threshold is reached, the cementing contact begins to break. There is a well correspondence between the threshold that a lot of contacts break down and the yield stress of the structure on the compression curve.