A crack theory-based bonded-particle model for rock particles considering size effects

Particle breakage shows significant effect on the macroscopic behaviour of rock materials, and the discrete element method is a powerful tool to investigate the relationship between micro fracture and macro deformation and strength. In this study, the concept of crack is introduced into the bonded-particle model (BPM) to simulate the breakage behaviour of rockfill materials, with randomly placed weak bonds representing cracks. Different from traditional BPM, the number, position and strength of the weak bonds are directly related to the number, position and length of cracks. With a reasonable length distribution of cracks, the proposed model can successfully reflect both the crushing strength variation and size effects. A set of crack parameters including the crack density, minimum crack length, maximum crack length and fractal dimension, are suggested. The crushing characteristics of realistic rockfill particles with two typical shapes are simulated quantitatively and verified with test data. It is found that the proposed model with suggested crack parameters can give reasonable prediction on the Weibull's modulus and size effect of rockfill particles.