Abstract: Large deformations in deep tunnels pose a significant challenge to safe and efficient mining. To control the stability of deep soft surrounding rock, a combined support method and its theoretical analysis model were proposed, based on the evolution of large deformation in deep tunnels. Results indicated that deep soft surrounding rock can be categorized into fracture deformation, damage and expansion deformation, and continuous deformation zones. Following the implementation of combined support measures, the ultimate bearing capacity increased linearly with the equivalent support forces of anchor rods and cables and exponentially with the grouting reinforcement coefficient. The parameters for pre-stressed bolts and cables should be determined based on bearing balance conditions when the grouting reinforcement coefficient is 1.0. Both the grouting reinforcement coefficient and the fracture zone radius of surrounding rock should be considered in the design of grouting support for deep and shallow holes. Collaborative support parameters for various support measures were determined by the ultimate bearing capacity balance conditions of the surrounding rock in the reinforced fracture zone. Numerical simulation and engineering application analysis demonstrated that the large deformation of deep soft surrounding rock can be controlled through the collaborative control of support structures. The combined support method can be widely applied in other tunnel engineering projects.

Key words: deep soft rock, larger deformation, combined support method, bearing capacity balance, collaborative control