Experimental and Numerical Study on the Failure Behavior of Rock Mass with Openings Under Dynamic Loading

In underground engineering, the dynamic failure mechanisms of rock masses containing openings under impact loading are of vital importance. This study systematically investigates the effects of opening shape, size, and orientation on the dynamic behavior of red sandstone. Dynamic impact tests are first performed using a split Hopkinson pressure bar together with high-speed photography and digital image correlation for full-field strain and crack monitoring. A two-dimensional combined finite–discrete element (FDEM) model is then developed to reproduce the dynamic failure process. It is found that the opening size significantly affects the dynamic compressive strength, while the opening shape dictates crack initiation and propagation. Circular openings induce symmetric cracking, square openings cause corner-dominated cracks, and horseshoe-shaped openings produce asymmetric failure whose dominant side depends on the rotation angle. The FDEM model established in this study successfully reproduces the main crack paths and failure modes observed in experiments, which provides a powerful tool for the analysis of rock dynamic failure. Moreover, the results in this study also provide practical engineering guidance for the reinforcement and support measures for different opening shapes.