Understanding fracture patterns of fractured rocks after dynamic impact is important for controlling the stability of rockslides and for effective prevention and mitigation. To investigate the effects of connectivity rate and joint angle on non-persistent granite specimens with coplanar rock bridges during dynamic impact, we adopted the central fractured rectangular granite specimens with different connectivity rates and different joint angles and performed the radial dynamic impact experiments on the specimens at the same velocity on the Split-Hopkinson Pressure Bar (SHPB) system with a compression bar diameter of 76 mm. Digital image correlation (DIC) was used to monitor the strain and displacement of the specimen plane. Test results showed that the damage process of fractured granite consisted of two stages: the aggregation of microcracks around the prefabricated cracks and the development of macroscopic cracks. The damage of the specimens is mainly dominated by shear stresses, supplemented by local tensile stresses. Significant stress concentration develops around the prefabricated crack tips under dynamic loading, resulting in localized high shear–stress zones and preferential crack coalescence within the rock-bridge region. Based on the final damage trajectory and crack initiation mechanism of granite containing prefabricated cracks, four typical impact fracture modes of granite were identified.
Xue et al. (Tue,) studied this question.
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