The Numerical Simulation On Highway Tunnel Stability And Mechanical Mechanism Of Tunnel Single Shell Lining

With the rapid development of the state highway construction, there are more and more highway tunnels. After excavation, the stress in rock mass will redistribute around grotto, and the surrounding rocks around tunnels in different geologic and mechanical conditions show different stabilities. According to the knowledge that the surrounding rocks are both the source of load and supporting body, the meaning of analyzing the stability of surrounding rock is very significant.Single shell lining is the generalization of lining without membrane, and its mechanics tendency is a body. The foreign countries have already applied single shell lining for more than 30 years, and Norway is the earlier country who applied single shell lining. From that time on, the single shell lining supporting technology has been accepted by more and more countries, and it has spread a good deal of countries all over the world. In the country, there has been a little application of single shell lining supporting technology in tunnels, some railway tunnels applied it, but it is applied in highway tunnels very little, so its study on highway runnels is imperative under the situation.This paper based on Guan Changshan tunnel which was in YuBa road of S103 line in Chongqing that is the project of Second road from Chayuan Nanan district to Lidu Fuling district, and analyzed the stability of the surrounding rock based on the stress concentration factor method and the support theory of broken zone, and finally studied the mechanical quality of single shell lining that made up of 2-layer shotcrete through the contact principle. Chapter 2 analyzed the influence factor of the stress concentration factor, at the same time, it discussed the changing rules of the stress concentration factor with side pressure ratio and depth. Chapter 4 analyzed the influence factor of broken rock zone, and studied its changing rule. Chapter 5 studied the mechanical quality of two-layer of shotcrete, under the condition that the 2-layer shotcrete was made early or late. At last, based on the practical testing results, the mechanical mechanism of single shell lining which was applied in Guan Changshan tunnel was studied.The main conclusions were obtained as following: 1) When other conditions remain unchanged, the stress concentration factor of surrounding rock around the tunnel increases with the growing of side pressure ratio; 2) when surrounding rock is in good condition, buried depth has a little influence on the stress concentration of surrounding rock after excavation, when the surrounding rock is bad, buried depth has a greater effect on stress concentration of surrounding rock; 3) With increasing of tunnel span, the stress concentration phenomenon will become more remarkable after the excavation of tunnel; 4) When other conditions remain unchanged, the range and thickness of broken rock zone increases with increasing of buried depth; 5) shearing force can be transmitted well between the two layers of shotcrete of single shell lining, so the mechanism of single shell lining is similar to combination beam model.