Study On Primary Support Method For Large Section Railway Station Tunnel With Four-Track

In recent years, as the rapid development of China railway construction, more and more large cross-section tunnel and station tunnel have been built, and whose span are bigger and bigger. The existing specification can not meet the needs of design and construction for the large cross-section tunnel. As to the present engineering practice, the past design method are not applicable, and there has no similar experience to be referenced wich result in the difficult for designer to choose a suitable excavation method, especially to determine the support scheme and parameters for it. On the one hand, to the tunnel security, what kind of supporting schemes can ensure the safety and feasible of large cross-section tunnel. On the other hand, to the project cost, what kind of support scheme can realize economic, and not increase unnecessarily investment, it has become the urgent needs of scientific problem to be solved. Therefore, we must analyze the stability and stress situation of rock mass and the specific properties of large cross-section tunnel, then put forward a reasonable support design principle and method, confirm support scheme and parameters which are both safe and economic.This paper based on the project background of a 4 lines-station of WuMengShan NO.2 tunnel in the LiuPanShui-ZhanYi of the new railway from GuiYang to KunMing, researching the support method for large cross-section tunnel through numerical simulation computation and site test. The main researches are as follows:(1) With the FLAC3D finite difference software, a numerical simulation of the whole construction process for WuMengShan NO.2 tunnel is made, analyzing the rock stability.(2) With the FLAC3D finite difference software, a numerical simulation of the identified construction scheme is made, and the strain situation of anchor and cable bolt support under the current set of conditions are analyzed. Under the premise of tunnel security, optimizing the method of anchor and cable bolt support, some useful conclusions are obtained.(3) Through the site test, monitoring the development of anchor force, cable bolt force and rock deformation caused by tunnel excavation, analyzing the stress and deformation situation in this actual engineering.The field monitoring results are close to the numerical simulation results.