Effect Of Shield Tunneling On Surface Settlement And Its Prediction

With the acceleration of urbanization in China,the demand for metro construction projects is increasing day by day.Shield tunneling method has many advantages in tunnel excavation process,such as high efficiency,economy,small impact on the surrounding ring,so it has been widely used in tunnel excavation engineering of subway project construction.Tunnel construction always adheres to and implements the principle of "safety first",but the settlement threatened by tunnel construction safety is accompanied by shield excavation.In addition,the frequency of land subsidence monitoring is not high and the feedback information is slow,which leads to many difficulties in land subsidence prediction nowadays.Therefore,it is of great practical significance to strengthen the influence of shield construction on land subsidence and to accurately predict it.Based on the theory of ground subsidence caused by shield tunneling,and combined with the current research situation at home and abroad,the paper summarizes and draws lessons from the previous research results and experiences,then focuses on the numerical simulation of shield tunneling with FLAC method,and takes the shield tunneling excavation project of M city of A Province as an example to discuss the application of FLAC shield method in the subway tunnel excavation project.Then,the construction of long-term settlement prediction model based on hyperbolic model after optimization is analyzed in detail,and the model is used to predict the impact of surface settlement on the construction safety of shield tunneling in M city.Finally,the prediction results,control strategies and control effects are discussed in depth,so as to provide theoretical guidance and experience for shield construction of metro tunnels in China.Use for reference.The main research points are as follows:(1)This paper carefully combs the basic theory of surface subsidence prediction,summarizes the law and mechanism of surface subsidence and deformation caused by shield constructiondisturbance,and then studies the time effect of ground subsidence,the main causes of ground subsidence and ground subsidence caused by shield construction disturbance,and the principle of ground subsidence curve.Face analysis.(2)Based on the principle of FLAC3 D,the numerical theory of shield construction is analyzed in detail by using FLAC method.(3)Taking the metro tunnel construction project in M city of A Province as an example,using FLAC3 D software,the numerical model of shield tunnel construction from HA Station to SL Station in M city is established,and then the numericalsimulation can be carried out after the tunnel construction,and the ground settlement caused by the tunnel construction is analyzed.(4)Using the Improved hyperbolic model to predict the ground subsidence caused by the disturbance of shield tunneling construction in M City Metro Line 2,it is found that the actual measured value is very close to the predicted value curve,which is almost consistent with the requirements of Engineering design,and that the pressure inside the cabin is set up scientifically to make it open.The control strategies of surface subsidence in special strata are put forward in the aspects of maintaining the stability of excavation surface,synchronization and secondary grouting.Finally,the control effect is evaluated.