Discrete element simulation study on the macro- and meso-mechanical properties of rockfill materials under wetting-drying cycles

The physical and mechanical properties of rockfill materials significantly deteriorate when subjected to cyclic wetting-drying. Based on the three-dimensional scanning results of rockfill particles, a comprehensive template library featuring a wide range of particle sizes has been established. Considering the effects of wet-dry cycles on particle strength, effective modulus, and inter-particle friction, a particle crushing simulation scheme has been proposed, taking into account the degradation of rockfill particles caused by wet-dry cycles. On this basis, using the coupled FDM-DEM method, a series of triaxial compression tests have been conducted on rockfill specimens subjected to cyclic wetting and drying. The results reveal that the initial modulus and peak strength of the rockfill materials decrease nonlinearly with an increase in the number of wet-dry cycles (N). Wet-dry cycles exert an inhibitory effect on volumetric strain during the initial stages of shearing and dilation in later stages of loading. However, as N increases to a certain value, the impact of wet-dry cycles on the macroscopic deformation and strength of rockfill materials becomes less significant. As the number of wet-dry cycles increases, both the average coordination number and contact slip ratio within the specimen rise. Additionally, the deviatoric fabric inside the specimen exhibits a nonlinear decrease, indicating a gradual reduction in anisotropy. This suggests that wet-dry cycles have an inhibitory effect on the development of anisotropy within the specimen.