Numerical simulation and field monitoring on a large cross-section pipe-jacking underpass traversing existing metro tunnels
LIU Bo1,2,ZHANG Dingwen1,2,LIU Songyu1,2,QIN Yunjun3
(1. Institute of Geotechnical Engineering,Southeast University,Nanjing,Jiangsu 210096,China;
2. Jiangsu Key Laboratory of Urban Underground Engineering and Environmental Safety,Southeast University,Nanjing,Jiangsu 210096,China;3. China Railway 23rd Bureau Group 1st Engineering Co.,Ltd.,Rizhao,Shandong 276826,China)
Abstract:A pedestrian underpass in Nanjing was constructed using pipe jacking method,which traverses both the existing metro tunnels and an urban main road in short distance. In order to ensure the safety of the tunnels and the road,a 3D FEM model was established before construction to simulate the whole construction process and to predict the possible deformation of tunnels and ground settlement. Based on the simulation results,the targeted measures to reduce the deformation were put forward,and a reasonable field monitoring scheme of tunnels and ground surface deformation was proposed. The monitored items included the vertical displacement,horizontal displacement,diameter convergence of tunnel and the ground settlement. The variation of tunnel and ground deformation was analyzed based on the observed data and three different stages that tunnel and ground surface experienced during construction were proposed. The results indicate that the vertical displacements of tunnel are mainly manifested as heaving induced by the unloading in the underpass. The influence of excavation of working shafts on the vertical displacement of tunnels is almost negligible. In the whole construction process,the vertical displacement of tunnel mainly experiences an initial settlement stage,a quick heaving stage and a steady heaving stage. The ground settlement goes through a heaving enhancing stage,a heaving weakening stage and an absolute settlement stage. In the same monitoring section,the maximum ground settlement occurs on the central line of underpass,and the settlement decreases away from the central line. The slight under-excavation method applied in the construction is effective in reducing the ultimate tunnel heaving and ground settlement.
刘 波1,2,章定文1,2,刘松玉1,2,秦玉军3. 大断面顶管通道近接穿越下覆既有地铁隧道数值模拟与现场试验[J]. 岩石力学与工程学报, 2017, 36(11): 2850-2860.
LIU Bo1,2,ZHANG Dingwen1,2,LIU Songyu1,2,QIN Yunjun3. Numerical simulation and field monitoring on a large cross-section pipe-jacking underpass traversing existing metro tunnels. , 2017, 36(11): 2850-2860.
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