Abstract:

 Under complex geological conditions, the loading on the surrounding rock mass of shallowburied doublearched tunnels is usually asymmetrical and it is particular the case when the surrounding rock mass of the tunnel is very weak. The asymmetrical loading has serious influence on the stability of the surrounding rock mass. In the paper, the advance support effect of the pipe roofs of asymmetricalloaded doublearched tunnels is analyzed by three dimensional elasticplastic finite difference method. The effect of pipe roofs not only depends on their own parameters, but also depends on the parameters of the ground and the tunnel structure. In the paper, analysis is made on the perimeter spacing, diameter, length remaining in the surrounding rock mass and mechanical model of the steel pipes of the pipe roofs, as well as on the excavation advance rate of the tunnel on basis of the geological conditions of the tunnel and the design requirements of the pipe roofs and conclusion is drawn that unbalanced design should be adopted for the pipe roofs of asymmetrical loaded doublearched tunnels.