Large Cross Section Tunnel Construction Under Complex Conditions, And Load Distribution Mechanisms Of Research

Neighborhood tunnels stand between separated tunnels and double-arch tunnels, which have thin middle rocky column and small clear distance. They can easily satisfy the specific geological, terrain and line, bridge and tunnel cohesion, and they are conducive to the overall line programming and line optimization, they have obvious technology and economic effects, so they are more and more widely used.Yan Gang tunnel is a single-arch four-lane neighborhood tunnel along the Guangzhou-Shenzhen Expressway. In this paper, we have taken it as our engineering background. By numerical simulation and theoretical analysis, the author has done detailed research on the construction methods and mechanical mechanism of the large cross-section neighborhood tunnel. Main tasks are as follows:Firstly, this paper summarizes the status of neighborhood tunnel study, and adopts three-dimensional fast finite difference method to simulate the tunnel model according to Yan Gang tunnel parameters. When it comes to the large cross-section neighborhood tunnel at different surrounding rock grades (Ⅲgrade,Ⅳgrade,Ⅴgrades), at different buried depth (shallow, shallow bias, deep) and under the different construction methods (entire section method, the bench method, CD method, CRD method, both side heading method), the values of its crown settlement, inverted arch uplift, inside convergence, ground settlement, the middle wall stress and displacement, plastic zone of surrounding rock are analyzed separately in order for us to obtain the optimal construction plan for the neighborhood tunnel in different geological features. Besides, corresponding research has been carried out concerning the construction sequence of the shallow bias neighborhood tunnel as well as the variation of its stress and displacement with the gradient changes.Secondly, we've done a brief summary of the research on rock pressure in a single-hole tunnel or double-hole neighborhood tunnel by many domestic scholars in recent years, and summarized the different calculation models and calculation methods of the tunnels at different buried depth (shallow, shallow bias, deep). Based on previous research, we are to find out a new calculation method about rock pressure in a neighborhood tunnel (deep tunnel).