Simulation Study on the Mechanical Effects of Optimized CD Method for Construction of Shallow Buried Bifurcated Tunnels in Densely Built-up Areas
To reveal the mechanical effect of shallow buried bifurcated tunnel construction in the building-intensive area,a three-dimensional finite element numerical simulation study was carried out to optimize the construction process of the CD method,relying on the Baotaping bifurcated tunnel project,which is close to the tunnel anchor of the Baidicheng Yangtze River bridge.Numerical simulation on the construction mechanics of shallow buried bifurcated tunnel under different cyclic scales,sequential tunnel construction order and secondary lining timing was carried out.The results show that:1)The tunnel excavation scale is positively correlated with the deformation of surrounding rock and the settlement of surface buildings,and the influence on the stress of the surrounding rock is not obvious,so it is more reasonable to choose the cycle scales of 1.0 m～2.0 m for the tunnel.2)The excavation sequences of left and right holes of the bifurcated tunnel,as well as the distance between two tunnel faces have a great influence on the deformation of the surrounding rock,but the impact on the settlement of the building and surrounding rock stress is very small,and the advance tunnel should be more than 40 m construction before the rear tunnel is excavated.3)The timely application of the tunnel lining has a certain influence on the deformation of the surrounding rock and the settlement of the building,but it has almost no influence on the stress of the surrounding rock of the tunnel,and it is feasible to apply lining after 60 m of tunnel excavation.
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