Development of a numerical simulator for 3-D dynamic fracture process analysis of rocks based on hybrid FEM-DEM using extrinsic cohesive zone model

The combined finite-discrete element method (FDEM) has attracted significant attention for numerical simulations of complex fracture process of rock-like materials as one of the promising hybrid methods. The mainstream of FDEM simulators developed to date is based on the intrinsic cohesive zone model (ICZM) in which cohesive elements are inserted into all the boundaries of continuum solid elements at the onset of simulations and an artificial elastic behavior must be incorporated to model the intact deformation of rock-like materials. However, the effect of introduction of the artificial elastic behavior on the precision of intact stress wave propagation has not been discussed in previous literatures and this paper discusses this issue. As an alternative for the ICZM-based FDEM, we apply the FDEM based on the extrinsic cohesive zone model (ECZM). An advantage of the ECZM-based FDEM is presented through the 3-dimentional (3-D) numerical modelling of dynamic tension test. In addition, the effect of considering the anisotropy of wave propagation in granite, which has been neglected in all the previous works using FDEM, is investigated through the ECZM-based 3-D FDEM simulation of dynamic Brazilian test with a split Hopkinson pressure bar apparatus. Through the presented numerical simulations, it can be concluded that the ECZM-based FDEM may be an alternative for numerical simulations of complex dynamic fracture process of rock-like materials instead of the ICZM-based FDEM.