Analysis on the Ground Deformation of Subway Tunnel Induced by Shield Construction

On the basis of the monitoring data and tunneling parameters of the section tunnel from Xufuxiang to Nanjing railway station in Nanjing No.1 Subway,this paper analyzes the process and distribution of the ground deformation induced by tunneling with the EPB shield machine through the saturated silty clay layer,silty clay and fine sand interbedded strata and the fine sand layer.Considering the factors of shield opening,groundwater level,pressure of soil chamber, grouting effectiveness etc,the ground deformation is simulated by the use of finite difference code FLAC~(3D).The measured results show the characteristics of ground deformation: high settling velocity with the maximum settling velocity-12～-15(mm·d~(-1)),rapid stabilization of disturbed ground with the ground stable in about 2 to 3 days after the pass of shield tail,and small affected area with the longitudinal settlement area ranging from 10 m ahead of the shield clutter to 16～20 m behind of shield tail along the tunnel alignment.The lateral settlement mainly distributes within 5～7 m from the tunnel center line and the ground is almost not disturbed in the area about 20 m beyond the center line.The simulated deformation results agree well with the measured data.