Study On Stress And Displacement Of The Bi-arch Tunnel's Mid-partition With Soft And Weak Surrounding Rocks

In the last few years, with the development of highway, the number of tunnels has evidently increased. Bi-arch tunnels, which have the advantage of smooth line type, higher use factor of space, lower land occupancy, and been convenient for the tunnels to connect with the way out of the tunnels, have been adopted in the highway project increasingly. The mid-partition, as the core structure of Bi-arch tunnel, will come through some kind of disturbance and stress redistributing in the process of tunnel's construction. At present, there are still few studies of numerical simulation specialized in the mid-partition. Notwithstanding that some thesis have studied the bi-arch tunnel, they didn't analyzed the mid-partition comprehensively. In order to find out the situation of mid-partition's stress and deformation under each phase of the predetermined excavating technique, the paper used the FEM soft of ANSYS to establish three elastoplastic FEM 2-D plan models based on the Li shi Bi-arch Tunnel Project, which is the first constructed Bi-arch tunnel in loess stratum of China .By the numerical calculation of simulating the tunnel's excavating process, the paper gains the distribution law of mid-partition'stress and deformation corresponding to different section figures, geometrical measures and diverse foundation performance. And the paper also compared the mechanics characteristic of flectional mid-partition with the erect mid-partition, thus brought forward the opinions about the optimization techniques of the mid-partition's geometrical measures. Further more, the paper established a perfect nonlinear elastoplastic FEM 3-D model, and gained the mid-partition's dimensional effect ,distribution law of stress and deformation, interaction of the left and right cavity and stability through the numerical calculation of simulating the tunnel's excavating process. Finally the paper analyzed the factual datum collected from the site of Li shi Bi-arch Tunnel so as to validate the result of the numerical simulation.