Research on Creep Deformation and Control Mechanism of Weak Surrounding Rock in Super Large Section Tunnel

In order to solve the difficulties of creep deformation of surrounding rock in super large section tunnel, taking Letuan tunnel of Binlai expressway, a typical super large cross-section tunnel as research background, the creep mechanical characteristics of surrounding rock are taken into consideration, and the influence of different supporting forms such as bolt reinforcement, rock grouting, high-strength arch and concrete lining on surrounding rock deformation and failure mechanism is comprehensively studied. The creep failure mechanism and high strength control mechanism of surrounding rock are obtained. Research results show that the surrounding rock shows obvious creep mechanical characteristics, the continuous growth of surrounding rock deformation has brought severe challenges to the tunnel support; the surrounding rock of super large cross-section tunnel shows unstable creep deformation failure mechanism with obvious acceleration of creep stage under the condition of no support; the influence mechanism of different support forms on the control effect of surrounding rock creep deformation is systematically studied, and the evaluation indexes of deformation control rate and creep control rate of surrounding rock prove that confined concrete, as a high-strength support type, has significant advantages for surrounding rock creep control. Based on the large-scale mechanical test system of tunnel, the mechanical test of confined concrete arch is carried out, and the bearing mechanism and mechanical characteristics of confined concrete arch are clarified. The field application results show that the confined concrete arch can effectively control the creep deformation. The research results can provide theoretical basis for relevant projects.