Study on the mechanism of loess collapse induced by clay particle softening based on discrete element method

The mechanism by which loess collapses serves as a critical basis for researching disasters in loess regions. This paper employed the employs element method (DEM) to link the internal mechanisms of collapse with its macroscopic manifestations. We first proposed that the softening of clay particles upon water contact is the direct cause of loess collapse. Additionally, an Enhanced Virtual Clay Method (EVCM) was developed, which integrates the finite element method (FEM) and DEM to construct a numerical model for characterizing macroscopic collapse of loess based on microscopic clay particle behaviours. The results revealed that the collapse settlement of the numerical model was highly consistent with theoretical values. Primarily, the collapse settlement of loess originated from the pore space generated by particle displacement, with secondary contributions from the reduction in the effective volume of loess particles caused by clay softening. The numerical model of loess collapse proposed in this study associates microscopic clay particle behaviours with macroscopic collapse behaviours, opening a new pathway for researching the relationship between the macro–micro-properties of loess.