Study On Laws And Control Measures Of Ground Deformation Caused By Shield Tunneling Of Xiamen Metro Jimei Center To Chengyi Square Section

In the construction process of city metro,there will inevitably be soil disturbance to the tunnel surrounding soil,causing surface subsidence which has a serious impact on structures built along the subway,underground pipe network,ground roads and other facilities.The effects range from cracks to houses collapsed,broken pipes,road subsidence,etc.So how to reduce ground subsidence caused by the construction of the tunnel is with practical engineering significance.Based on the collection and reading the relevant literature,the thesis conducts a depth research on the law of surface subsidence caused by shield construction,summarizes and analyzes the current research.The surface settlement mechanism is discussed in detail,and the on-site measurement program of Xiamen Metro Line 1 Jimei central station-Cheng Yi Square Station section is designed.Then the finite element analysis method is used to simulate the ground settlement caused by the tunnel construction and the settlement curve of the ground is obtained.Finally a comprehensive analysis of the measured data and simulation results is conducted,the surface subsidence law is obtained and partial control measures are proposed.The research results are as follows:?When tunneling separately,the difference of the maximum settlement of the earlier tunnel and the later tunnel is about 10%to 20%of the maximum settlement value of the tunnel;? For the longitudinal ground settlement,the surface subsidence is about 10%to 20%of the maximum amount settlement before the shield machine reaches,and that is about 60%to 80%of the maximum amount settlement when the shield machine is passing through.When the shield machine has passed through and is 3D(D is the tunnel excavation diameter)away from the monitoring section,the surface subsidence is about 90%of the maximum amount settlement;? In the cross-sectional analysis,the settlement of the distance ID away from the center of tunnel is about 30%to 40%of the maximum amount settlement,while that of the distance 2D away is about 15%and that of the distance 3D away is about 5%;? The thrust force of Jimei to Chengyi tunnel section should be controlled at around 300kpa;? In the separated tunneling,the largest surface settlement is-17.76mm when the spacing of two tunnels is 1D,and that are-14.153mm and-11.823mm when the spacing is 2D and 3D The maximum surface subsidence decreases with the two tunnels' spacing increasing.The excavation of the later tunnel causes secondary soil disturbance to the earlier tunnel.When the spacing is 1D,the surface settlement of the earlier tunnel increases 18.13%.When the spacing is 2D and 3D,the surface settlement of the earlier tunnel increases 16.12%and 9.24%respectively.The extent of the disturbance decreases with the increasing of the spacing of the two tunnels;? Reducing construction disturbance to the soil is the key to control surface subsidence,mainly doing the following aspects:making good planning,selecting rational line,controlling soil tank pressure reasonably,doing the shield tail grouting work well,controlling various parameters well,ensuring the shield posture and so on.