Numerical simulation of damage failure and supporting time of anchored surrounding rock in a middle roadway of Xincheng Gold Mine

The reasonable choice of supporting time should not only fully develop the control of supporting structure on surrounding rock, but also actively mobilize the self-stability ability of surrounding rock. Rational supporting time is of great significance to guarantee the security and economy of excavation. In this paper, a numerical simulation method for the damage and failure of anchored surrounding rock is established by comprehensively considering the elastic damage model of surrounding rock, the elastoplastic hardening model of bolt and the double exponential shear-slip model of interface. Taking the excavation and support engineering of a middle roadway in Xincheng Gold Mine as an example, the convergence deformation of roadway, the damage of surrounding rock and the state of bolt under different supporting time and different anchored length are compared and analyzed. It is found that the earlier the anchoring bolt support is, the smaller the convergence deformation of roadway is, but the earlier the supporting time will make more anchoring bolts enter the stage of plastic hardening and slip instability of anchored interface, resulting in anchored failure. Because the high strength of surrounding rock in Xincheng Gold Mine limits the damage evolution and deformation development of surrounding rock, the supporting time and anchored length have little influence on the convergence deformation of roadway and the size of excavation damage zone. Through the analysis of the mechanical response of the surrounding rock and the anchoring bolt, which is found that when the anchored length is 1.7 m, the anchoring bolt has less slippage and debonding, and the distance from the palm surface is determined to be 4 m for the anchoring bolt support as the best supporting time. This investigation provides a theoretical analysis method for the study of supporting time of the excavation and support engineering in other mines.