Numerical simulation on the collapse of particle-liquid mixtures by the coupled DEM-LBM

Collapse of particle-liquid mixtures generally occurs during geological hazards, such as debris flows, landslides and dam breaks. Based on the developed three-dimensional coupled DEM-LBM incorporating both the free-surface flows and non-Newtonian fluids, the collapsing process of particle-liquid mixtures is simulated, and the numerical results are compared with experimental tests. Furthermore, the influences of initial column aspect ratio, interstitial liquid type and initial saturation level on the granular collapse are investigated. The results show that the numerical simulation by the three-dimensional coupled DEM-LBM can well reproduce both the motion characteristics of particles and liquid during the collapsing process of particle-liquid mixtures. Compared with the dry granular column collapse, the particles in the particle-liquid mixtures can reach a longer final runout distance. The particle front in particle-water mixtures eventually travels a longer distance than that of the particle-mud mixtures. With a higher initial granular column and a higher initial saturation level, the interstitial liquid has a more significant effect on the particle fluidity. As for a granular column with an initial aspect ratio of 2.46 and a saturation level of 1.0, compared with the dry granular collapse, the particle runout distance of particle-water mixtures increased by 27.7%, and that of particle-mud mixtures increased by 13.3%. The present study provides a scientific basis for understanding the solid-liquid interaction mechanism and assessing the disaster risk.