Study On Mechanical Behavior Of The Expansion Of The Existing Tunnel Project

With the fast development of the national economy and the implementation of western development strategy, the volume of road transport is increasing sharply thus the technological transformation of existing expressway line under construction occupies an important position. In the course of the transformation of the existing line tunnel project, as an important part of the existing lines must also be transformed. Owing to the restrictions of geological conditions and terrain conditions, double line can not be built parallel, to meet the increased traffic lane of traffic demand, tunnel should be extended on basis of the existing one. The expansion of the existing tunnel lane and the existing tunnel section clearance, to meet the increased traffic volume, are needed. At present, study of the expansion of the existing tunnels is rarely seen, so it is necessary to study the expansion of the existing tunnel construction.In this paper, numerical analysis is adopted. The mechanical research of the expansion of the Pan-Long Mount tunnel project is carried out, and stress and strain of the tunnel in the process of the construction which have reference value to construction, are achieved. According to the simulation of the tunnel design and construction of the actual situation, the following research work is carried out: First, through three-dimensional elastic-plastic simulation finite difference analysis of the widening of the tunnel ,the results of the force and deformation law of the surrounding rock, supporting system of the expansion of the existing highway tunnel in the terrain and under construction are achieved. Secondly, through two-dimensional and three-dimensional numerical simulation of different levels of general rock in the expansion construction, stress and displacement field of the surrounding rock in the expansion of the existing tunnels under the influence of unsymmetrical pressures are obtained. The results show that under the influence of the unsymmetrical pressure stress and strain of the tunnel are unsymmetrical, the construction of right arch foot and tunnel vault is the main part, so it is necessary to support the tunnel in time and reinforce the support parameters. In addition, because of great dislocation at the interface of the reinforced section of tunnel entrance and the common section of tunnel body, so the mechanical influence is complex, the design and construction great importance should be attached during design and construction.The studies of this paper have reference value and hope that it also has promotion effect to the extension of the design and construction of the existing tunnel.