Discrete element modelling of fracture in quasi-brittle materials

The fracture of quasi-brittle materials (e.g. concrete, soft rock) has long been a crucial issue in research and engineering. In the past few decades, numerical methods have been applied to investigate the fracture mechanism of these material types. Among others (e.g. FEM, mesh-free), Discrete Element Method is regarded as an efficient numerical method to model the failure of materials owing to its advantages for fracture modelling over the classical continuum-based methods. However, despite its powerful nature, current contact models for DEM are not capable of capturing the local failure mechanisms of cement binder contacts between aggregates in quasi-brittle materials. This research applies a cohesive model into DEM simulation to characterise and investigate the failure responses of quasi-brittle materials. The model couples damage mechanics and plasticity theory, and also can handle fracture under mixed-mode stresses. This modelling approach is then employed to simulate experimental tests of quasibrittle materials. Numerical results are shown to agree with the fracture behaviour of the materials in experiments and better than the result of current most popularly used model in DEM simulation.