Numerical study on P-wave propagation across the jointed rock masses by the combined finite-discrete element method

Abstract The combined finite-discrete element method (FDEM) is an advanced finite and discrete element coupling method. This study further applies it to the problem of stress wave propagation in the jointed rock mass. Firstly, the fundamental theory of FDEM is briefly described and the methods commonly used in FDEM to characterize structural planes are comprehensively analyzed. Then, based on the viscous boundary condition (VBC), the viscous-spring boundary condition (VSBC) is added to absorb the reflected wave at the artificial boundary and restore the residual displacement to meet the actual engineering. In addition, the application range of the VBC and VSBC is verified, which indicates that the VBC and VSBC in the improved FDEM can be well applied not only to the continuum range but also to the case of the new fracture formed. Finally, several classic models are solved to verify the stress wave propagation across different types of joints by FDEM. The results reveal that results from FDEM agree well with analytical solutions based on the displacement discontinuity model and numerical solutions from universal distinct element code (UDEC), which means that the improved FDEM can capably and accurately simulate wave propagation in the jointed rock mass.