Deformations of surrounding rock and stress characteristics of steel arch of Hanjiang-Weihe River water diversion tunnel

The Hanjiang-Weihe River water diversion tunnel has high in-situ stress, high rock strength, strong excavation disturbance and complex geological conditions. During the excavation process, the supporting structures sometimes become unstable and fail, which seriously threatens the safety of workers, equipments and properties. To better understand the safety state of supporting structures, for the Lingbei project of the Qinling Tunnel, the convergent deformations of surrounding rock and the stress on the inner and outer flanges of the steel arch are monitored to analyze their distribution characteristics and evolution process. The analysis results show that the deformations of the surrounding rock can be divided into three stages, rapid deformation period, deformation period, and slow deformation period. The deformations mainly occur within 60 hours of the excavation, accounting for approximately 45% of the total deformations. The stress characteristics of steel arch are complicated. The stress applied on the steel arch is asymmetric, and the overall performance is mainly compression. By analyzing its axial forces and bending moments, the safety state of the arch frame can be identified.