A combined DEM-SBFEM for particle breakage modelling of rock-fill materials

Both experimental and numerical studies show that particle breakage has significant influence on the macro mechanical response of granular soils. This study presents a novel computational method that combines two numerical techniques viz., the discrete element method (DEM) and the scaled boundary finite element method (SBFEM), with an aim to model the particle breakage phenomenon in granular soils. Individual grains in the soil are modelled by a single star-convex polygon having an arbitrary number of sides. The DEM, which is well-known for its ability in addressing problems involving the response of granular and discontinuous media, is used to determine the motion of- and interaction between the particles. At the end of each time step, the SBFEM is used to determine the stress state in the grains. As the SBFEM can be flexibly formulated on polygons with arbitrary number of sides, only a single polygon is required to replicate the morphology of each grain. This reduces the computational resources necessary for a stress analysis of each grain. The particle breakage condition is determined if the stress state in a polygon satisfies a mechanically driven criterion. Breakage is executed by splitting a polygon into two. The resulting new polygons are directly modelled by the SBFEM without any change to the formulation. The feasibility of the developed technique is demonstrated by a numerical benchmark.