Study On Stability Of One Tunnel Entrance Surrounding Rock And Supporting Structure

It is said that face excavation construction is difficult and unkennel construction is difficult in tunnel engineering, the reason is that surrounding rock of tunnel entrance shallowly buried and seriously weathered, which is of bad quality and self-stability. Most of the surrounding rock has weak structural surface which is unfavorable to its stability and unfavorable to the rapid efficient construction. It also hinders the engineering progress, causes accident and endangers people's life.Different construction methods have different effects to the stability of tunnel surrounding rock and supporting structure. This paper analyzed the effect of full face construction method and benching tunneling method on the stability of tunnel surrounding rock and supporting structure by finite element numerical simulation of one tunnel's entrance excavation. It is concluded that benching tunneling method is more suitable to the tunnel entrance construction.This tunnel's entrance is a heading slope which covered soil and fully weathered rock, and the slope is easy to lose the stability when perturbed. The slope calculation method in construction is usually two-dimensional limit equilibrium method, and sliding surface needs to be assumed beforehand. However, in fact , all landslides have three-dimensional effects. This paper analyzed the tunnel entrance slope by three-dimensional finite element strength reduction method, and judged its potential sliding surface and its landslide possibility.This paper established the secondary lining load-structure method numerical model considering loose load and residual thrust, and analyzed stability of the tunnel entrance secondary lining. It is concluded that residual thrust is unfavorable to the internal force of the entire lining structure's wall on both sides, but favorable to the internal force of the arch ring and invert...