Dynamic Behavior of Rock Joint under Different Impact Loads

In order to investigate the influence of the rock joint to rock mass on dynamic loading, the Split Hopkinson Pressure Bar (SHPB) apparatus is used as an effective instrument. Using three different samples of intact (Series A), unfilled joint (Series B), and filled joint (Series C) interfaces, impact tests were performed under different impact speeds. Results showed that the peak strength of series B and C was 55%–75% that of series A. Series C was 10%–20% lower than series B because the former was filled with gypsum in the interface. The attenuation law of the transmission coefficient and failure mode caused by the rock joint was also obtained. To address the problem of classic rock joint constitutive relations being unsuitable under dynamic loading, a new regular expression is proposed by defining two velocity impact factors at respective impact velocities of 3.6 m/s, 6.6 m/s, and 9.6 m/s. Calculation results of this function are tested and verified, and the data are highly consistent.