Coupling of material point method and discrete element method for granular flows impacting simulations

Granular debris flows are composed of coarse solid particles, which may be from disaggregated landslides or well-weathered rocks on a hill surface. The estimation of agitation and the flow process of granular debris flows are of great importance in the prevention of disasters. In this work, we conduct physical experiments of sandpile collapse, impacting 3 packed wooden blocks. The flow profile, run-out distance, and rotation of blocks are measured. To simulate the process, we adopt a material point method (MPM) to model granular flows and a deformable discrete element method (DEM) to model blocks. Each block is treated as comprising 9 material points to couple the MPM and DEM, and the acceleration of grid nodes arising from the contacts between granular material and blocks is projected to the discrete element nodes working as body forces. The contacts between blocks are detected using the shrunken point method. The simulation results agree well with the experimental results. Thus, the coupling method of MPM and DEM developed in this work would be helpful in the damage analysis of buildings under impact from the debris flows.