3D FDEM modelling of dynamic rock fracture and fragmentation in triaxial Hopkinson bar tests under combined multiaxial static and dynamic loading

Abstract

The responses of rocks to dynamic loading under multiaxial in-situ stress state are of vital significance to many engineering applications such as rock drilling and blasting. In this study, a full-scale three-dimensional (3D) numerical testing system of the triaxial Hopkinson bar is established based on combined finite-discrete element method (FDEM) to investigate the dynamic responses of rocks under combined multiaxial static and dynamic loading conditions. The dynamic progressive fracture and fragmentation processes of rock specimens under uniaxial, biaxial and triaxial confinement conditions in triaxial Hopkinson bar tests are modelled using 3D FDEM. The simulated rock fracture and fragmentation patterns and dynamic stress-time profiles are in good agreement with the experimental observations. Under different pre-stress states followed by dynamic loading, the behaviours of rock exhibit prominent confinement dependence. Increasing lateral confinements from the dynamic uniaxial compression test to the dynamic triaxial compression test results in the substantial reduction in the degree of damage to the rock, as the rock specimen in the uniaxial compression modelling is broken into large quantities of fragments while only macro-fractures and fracture planes are formed inside the rock specimen in the triaxial compression modelling. This study is expected to further contribute to the better understanding of dynamic fracture mechanics of rocks in specific scenarios.