Upper Bound Analysis Of Earth Pressure And Surrounding Rock Stability Analysis For Shallow Tunnel

In recent years, with the rapid economic and social development of our country, the projects of tunnel construction enter a fast development period. In this case, the technology for tunnel construction has been great progress on the basis of practical experience. Surrounding rock, generally is a loose accumulation body, has been severely weathered in shallow tunnel. In this case, the stability of the caverns are poor after tunnel excavation. Consequently, the pressure and the stability of surrounding rock had been studied in this paper as follows:1. Based on plasticity limit analysis by upper bound theorem and non-linear Mohr-Coulomb failure criterion, the mufti-tangential method is introduced into the nonlinear upper bound limit analysis. The formula, which is used in calculation the shallow tunnel surrounding rock pressure in the failure modes of this paper, has been derived.2. Based on the formula of mufti-tangential method, the upper-bound solutions under different parameter values are calculated by the Mathlab optimization algorithm. By calculated the surrounding rock pressure of shallow tunnel under different parameters, this paper analyzes the influence of various parameters on the upper-bound surrounding rock pressures solution. By contrast to calculation results of existing methods, it shows that the mufti-tangential method is correct.3. Supported by the E-ling tunnel projects and the safety factor method, this paper use the calculation program to study the stability of shallow tunnels. By drawn the contour map of the tunnel safety factor, the construction schemes have been optimized. The construction parameters of three-step method are optimized by the numerical simulation. Through the comparative analysis of stress distribution, displacement distribution, as well as the safety factor distribution, this paper obtains the best construction program to provide a reference for the E-ling tunnel projects.