Dynamic strength and fracturing behavior of persistent fractured granite under dynamic loading

Dynamic impact tests were performed to experimentally study the dynamic mechanical properties, stress wave propagation, energy evolution characteristics, and failure modes of persistent fractured granite with single-bonded and unbonded planar joints at three angles using the split Hopkinson pressure bar (SHPB) method and digital image correlation (DIC) method with an ultrahigh-speed camera. The results showed that the dynamic strength of the persistent fractured granite increased with increasing loading rate and decreased with increasing joint angle or joint lengths, while the wave attenuation is more significant at larger joint angles or longer joints. The variation in energy absorption was similar to the variation in dynamic strength, showing a positive correlation between energy absorption and dynamic strength. Moreover, as the joint angle increased from 20 degrees to 30 degrees, the failure mode gradually transformed from tensile- to shear-dominated failure. Combined with an ultrahigh-speed camera and the DIC method, the influencing mechanism of the joint angle and loading rate on the dynamic strength and failure mode was revealed.