Study on Large Deformation Control Technology and Engineering Application of Tunnel with High Ground Stress and Weak Broken Surrounding Rock

Abstract

In order to prevent and control the large deformation of surrounding rock of tunnels, the selection of section type and the determination of excavation method were numerically investigated by using the self-developed code—Realistic Failure Process Analysis (RFPA2D) and taking a specific project as the engineering background—Ruyi tunnel. Then, special measures were employed to deal with the dangerous parts of the section of the tunnel. Finally, the control effect of surrounding rock deformation was checked with displacement monitoring and microseismic monitoring. The results showed that the horseshoe-shaped tunnels with six centers and the bench excavation can prevent the occurrence of large deformation. The “support resistant limiting damper-H230 grid steel frame” and the increased depth of the inverted arch can effectively control the deformation of the vault and the arch bottom. Besides, it was revealed that the propagation and connection of cracks at the top of the tunnel are the most critical cause for the instability failure of the tunnel. Engineering application indicated that the selected section type, excavation method and special support measures for dangerous parts greatly reduce the deformation of surrounding rock and effectively solve the problem of large deformation of the weak broken surrounding rock.