Based On Weak Surrounding Rock Excavation Endless Numerical Simulation

Along with the rapid development of highway, high-speed railway, municipal, and hydropower construction, hundreds of kilometers of new tunnels are built in our country every year, Due to the complex engineering geological and hydro geological conditions, many safety accidents appeared in tunnel construction, especially under the condition of soft surrounding rock. How to ensure the safety of tunnel construction has become a technical problem in front of the tunnel technology workers which needs to be solved urgently Circular excavation can stabilize tunnel faces, control the vault and ground surface settlement, and is widely used in V scale two-lane surrounding rock tunnel. But the current design for a specific engineering is given priority to engineering analogy method, and is less often from the perspective of the mechanics analysis. Based on Tiger-hill tunnel of Xiang-Yu (Chongqing-Changsha) highway, circular excavation in weak surrounding rock tunnel is analyzed and main research contents are as follows:The research status both at home and abroad of weak surrounding rock tunnel construction is systematically introduced, and emphasizes the circular excavation process and construction points for attention; Fully elaborated the basic concept of new Austrian method construction, design, construction characteristics and the related theoretical basis; Analyses the feature of FLAC3D, and Moore-coulomb constitutive model is presented and its numerical implementation method; A total of27total vault displacement, horizontal convergence in the cases of and on behalf of the settlement. With comprehensive correlation degree as the criterion standard, studies the core soil height, step length and core soil vertical Angle to vault sedimentation and ground surface subsidence, horizontal convergence effect size.Calculation results show that:for vault subsidence, core soil height> profile Angle step length. Influence on horizontal convergence, core soil height> step length of the profile Angle. Influence on surface subsidence, soil core height>step length of the profile Angle.