Failure Mechanism of Highly Stressed Rock Mass during Unloading Based on the Stress Arch Theory

During excavation unloading, highly stressed rock masses at great depth exhibit failure modes with different scales, for instance, zonal disintegration, rockbursts, and super-low friction. The root cause of the failure mechanisms of highly stressed rock masses differs. In recent years, research on the failure mechanism of highly stressed rock masses during unloading has become a frontier topic in geotechnical engineering. This paper relies on the deep mining process laboratory of the China Hongtoushan Copper Mine, where it has been observed that the deep rock unloading process causes macroscopic deformation and opens microscopic joints in deep rock. Analysis of monitoring data has shown that compressional deformation occurs in the surrounding rock masses subjected to unloading during mining. It has also verified the engineering phenomenon of local compression in rockbolts. Test materials similar to deep rock were used to simulate the unloading process of in situ rock mass and verify the physical phenomenon of shrinkage of the rock mass in the unloading area. Based on this phenomenon, the stress arch theory for rock mass failure mode has been established. Finally, numerical simulation analysis of the influence of different radii of the curvature fissures in surrounding rock and the displacement field distribution of the stress field was used to verify the stress arch theory for the failure mechanism of highly stressed rock mass during unloading.