|
In urban subway engineering construction, the construction technique of shield method tunnel with its unique intelligent, safe, efficient, etc characteristics and advantages, get more and more extensive application. Shield method in construction process will inevitably on the surrounding rock mass caused a disturbance surface subsidence. This paper takes Shenzhen subway line one between Xixiang Station～Gushu Station earth pressure balance shield tunneling construction engineering as background, for the surface subsidence caused by the shield construction research, made the following results.Through the destruction of buildings around caused by the open-cut construction survey, lead the necessity of subsequent construction scheme optimization design; Analyzed the shallow tunneling method and shield method’s basic principles, advantages and disadvantages, and Put forward plans to adopt shield tunneling; Using FLAC 3D numerical simulation software, contrast and analysis of the ground surface settlement and physicomechanical plastic damage area case by the shallow tunneling method and shield method evolution rule, provide the basis for the scheme risk assessment, verified the feasibility of shield tunneling.Through shield tunnel project interval of monitoring measurement, analysis of shield summarizes the surface subsidence caused by the construction horizontal and vertical distribution rule and proved the feasibility of shield tunneling. Singleline tunnel surface settling tank along the tunnel axis curve in basic symmetric distribution, transverse main influencing area approximately the centerline side 2D (D for tunnel diameter) range, outside the centerline 5D from regional hardly affected; The influence of longitudinal surface subsidence ahead for the knife dish within about 20～30m to shield tail rear about 30～45m, after the excavation face 2D, after the surface subsidence gradually began to decrease, settlement in stable moved, Shield tail emerge settlement is control key phase of surface subsidence.Using FLAC 3D numerical simulation software, the shield method to simulate the dynamic construction process, and further analyzes the stratum deformation regularity cause by the process of shield tunneling, meanwhile will simulation calculations of the results with the field monitoring data are compared, measured value and simulation value error is smaller, reflect subsiding regularity of roughly the same, explains the numerical simulation of rationality.Analyzed the tunnel buried depth, foundation modulus, soil warehouse pressure and shield of the grouting factors of shield law of surface subsidence caused by the construction influence. Along with the increase of buried deep tunnel, the surface settlement quantity decreases, and transverse settling tank wider; The soil modulus and the parameters of the equivalent circular zone of surface subsidence layer have significant influence on the ground surface settlement, with the increasing of the modulus of surface subsidence and significantly reduced, but when its modulus increased to a certain degree, the surface settlement quantity change range of slow; Soil cabin pressure less than the original static earth pressure, the most massive ground settlement with the decrease of the soil cabin pressure increased gradually; Soil cabin pressure is greater than the original static earth pressure, the most massive ground settlement with increase of soil cabin pressure increased gradually.
|