Dynamic mechanical properties and cracking behaviours of persistent fractured granite under impact loading with various loading rates

Abstract

The previous investigation on rock dynamics mainly focused on the intact and non-persistent fractured rocks, rather than the persistent fractured rocks, while understanding the dynamic mechanical properties and instability failure characteristics of persistent fractured rocks under impact loading remains defective. In this study, impact tests are performed to experimentally study the dynamic mechanical properties, failure modes and energy evolution characteristics of persistent fractured granite with a variety of joint configurations using the Split Hopkinson Pressure Bar (SHPB) apparatus. This paper especially concerns the effects of the loading rate on dynamic failure of persistent fractured granite and the energy evolutions in dynamic failure. Experimental results show that the dynamic strength and energy absorption of persistent fractured granite decrease with increasing joint number. Moreover, as the joint inclination angles increase from 30° to 90°, the failure mode gradually transits from shear to tensile, and the dynamic strength of persistent fractured granite first increases and then decreases. Based on the experimental observations and elastodynamics, the influence mechanism of joint configuration on dynamic failure is finally revealed. The findings can fill in the gap of dynamic failure mechanism with the incorporation of persistent fracture at different loading rates.