Development of a numerical simulator for 3-D dynamic fracture process analysis of rocks based on hybrid FEM-DEM using extrinsic cohesive zone model1

The combined finite-discrete element method (FDEM) is one of the promising hybrid methods that has attracted much interest for the numerical simulations of complex fracture processes of rocks. The mainstream FDEM simulators developed to date are 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 a penalty elastic behavior must be incorporated to model the intact deformation of rocks. However, previous studies have not systematically discussed the effect of the introduction of the penalty elastic behavior on the precision of intact stress wave propagation, and this paper discusses this concern. This paper applies an FDEM based on the extrinsic cohesive zone model (ECZM) as an alternative to the FDEM(ICZM). An advantage of the FDEM(ECZM) is first presented through a three-dimensional (3D) numerical modeling of a 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 the FDEM, is investigated through the 3D FDEM(ECZM) simulation of a dynamic Brazilian test using a split-Hopkinson pressure bar apparatus. Through the presented numerical simulations, we can conclude that the FDEM(ECZM) is a useful alternative to FDEM(ICZM) for numerical simulations of complex dynamic fracture processes of rocks.