Research on the Failure Mechanism and Control Technology of Surrounding Rock in Deep Large Section Tunnels

To solve the problems of severe deformation, support failure, and excavation support imbalance in deep large section tunnels. Taking the 23105 belt roadway of Xiegou Mine as the engineering background, the deformation instability characteristics and failure mechanism of the surrounding rock of the large section roadway were analyzed through on-site observation. Based on rock damage mechanics analysis, an innovative optimized support system with high bearing capacity flexible anchor rods as the core has been designed. To verify the scientificity of optimizing the support system, a UDEC Trigon discrete element numerical model was used to compare and analyze the surrounding rock control effects of traditional support and optimization systems from three dimensions: tunnel deformation, plastic zone evolution law, and crack development characteristics. The simulation results show that optimizing the support system significantly improves the bearing capacity of the surrounding rock and reduces the deformation and crack density of the roof and floor. Engineering application monitoring data shows that after optimizing the support, the surrounding rock of the tunnel gradually stabilized after 30 days, with a maximum roof subsidence of 196 mm. The cross-sectional profile remained intact, significantly service performance.