Dynamic Mechanical Behavior of Rock Specimens with Varying Joint Roughness and Inclination under Impact Load

The influence of joint roughness and inclination on the dynamic mechanical properties of rocks is a prominent research area. In order to investigate the effects of joint roughness and inclination on the dynamic mechanical properties of jointed rocks, impact tests were conducted using a spilt Hopkinson pressure bar (SHPB) apparatus for prefabricated serrated joint cement mortar specimens with varying joint roughness and inclination. The failure mode, stress wave propagation characteristics, peak stress, and stress wave energy transfer law under impact load were analyzed. The results indicate that both joint inclinations and joint roughness coefficients (JRC) have a strong influence on the failure mode, peak stress, and stress wave energy transfer of jointed specimens. The jointed specimens exhibit three distinct failure modes under impact load, namely splitting tensile failure, shear slip failure, and compound failure of splitting tensile and shear. The peak stress initially decreases then increases with the increase in joint inclination angle, namely a V-shape variation, while it gradually increases with JRC increasing from 0 to 20. Jointed specimens exhibit the lowest peak stress at an inclination angle of 45° and JRC of 0. The variation of transmitted energy coefficient is similar to the peak stress, while the variation of reflected energy coefficient is opposite to the peak stress. At joint inclination angles of 0° or 90°, the reflected energy coefficient increases with the increase of JRC from 0 to 20, while the transmitted energy decreases. However, when the joint inclination angle is in the range of 30° to 60°, the reflected energy coefficient gradually decreases with JRC increasing, while the transmitted energy coefficient gradually increases.