Numerical simulation of direct shear test of rockfill based on particle breaking

In the traditional Mohr–Coulomb criterion, the shear strength is determined by cohesion and friction angle. However, the particle breakage that occurs on the shear failure surface of rockfill makes it difficult to express the shear strength of rockfill using the traditional Mohr–Coulomb criterion. It is assumed that the shear strength is the friction force of the particle contact surface, and the power function relationship between the shear strength of rockfill and the normal stress is derived, where the index is a function of the particle fractal dimension. The discrete element software PFC-2D was used for numerical simulation of rock single particle crushing and rockfill direct shear test. The single particle crushing test simulates the whole process of particle crushing and verifies the size effect of particle crushing strength. In the direct shear test simulation, 8 different test parameter groups are set up to explore the effects of basic particle adhesion, single particle porosity, rockfill porosity on shear strength and body strain and verify the correctness of the derived power law shear strength formula.