Study On Dynamic Deformation Law And Soil Disturbance Of Retaining Structure During Shield Tunneling

The 21 st century shield method is widely used in underground tunnels and various underground municipal pipelines.In the construction process,the shield tunnel will inevitably cause disturbance to the adjacent foundation pit and surrounding soil,resulting in the foundation pit surrounding structure and its surrounding areas.Additional deformation and additional internal forces are generated in the soil layer,and shield tunneling is one of the five major risks of shield construction.The dynamic effects of the whole process of the excavation on the foundation pit retaining structure and the surrounding soil are studied to ensure the safety and shield of the pit of the subway station.The smooth exit of the structure is of great significance.At present,there are few studies on the influence of shield tunneling on the disturbance of foundation pit and surrounding soil at home and abroad,so the research of this subject is particularly important.This paper takes the shield section of the Yaqian Station on the No.1 line of Hangzhou-Shaoxing Intercity Railway as the engineering background,and uses the method of numerical simulation and on-site monitoring to study the surrounding structure of the subway pit and the surrounding soil in the shield tunneling process.Full-cycle response.The main findings of the study are as follows:(1)Sorting the reinforcement range and reinforcement mode of the end well soil,combining the theory of plate strength,slip instability theory and soil limit equilibrium,the stability check of the foundation pit engineering is carried out,and the results show that the reinforcement zone is longitudinally strengthened.7m,horizontal reinforcement 3m construction plan,can meet the stability requirements of shield safety out of the hole.(2)Using FLAC3 D finite difference software,the effects of different longitudinal reinforcement dimensions and the origin and time of the shield on the subway station envelope structure and surrounding soil changes are studied.The numerical simulation results show that: 1)After the hole is removed,the soil aroundthe hole shows an elliptical displacement zone,and the main influence range is 1D.The displacement of the soil in all directions gradually decreases with the increase of the size of the reinforcement zone.After the longitudinal reinforcement size is greater than 6m,The displacement of the soil remains basically unchanged,and finally stabilizes at 1mm;the plastic zone of the solidification is mainly distributed on both sides of the hole.With the increase of the longitudinal reinforcement range,the damage zone of the plasticized top of the solidification is gradually reduced,and the reinforcement size reaches 9m or more.The plastic zone gradually disappears;the retaining structure has a large rigidity,the maximum displacement is less than 3mm,and the displacement mainly occurs at the hole and the corner.2)In the shield tunneling stage,the maximum settlement of deep soil occurs at the top of the tunnel,and the largest uplift occurs at the bottom of the tunnel.The variation of the junction between the reinforcement zone and the non-reinforced zone is obvious.The lateral and vertical influence range of the settlement is about 3D;the longitudinal reinforcement is 9m.Above,the settlement of the retaining structure is maintained at1.3mm,and the effect of increasing the longitudinal reinforcement size on the retaining structure is no longer obvious;the displacement of the segment is more obvious at the junction between the reinforced zone and the non-reinforced zone,and the joint of the segments is presented.The wave-like change advances with the shield,and the entire segment exhibits up and down convergence,and the outer sides are broadly deformed.(3)By comparing the numerical simulation with the on-site monitoring data,the maximum displacement of the lateral settlement of the surface is above the tunnel,and the funnel is distributed around the tunnel axis.The simulation trend and the measured value of the measured curve are basically the same,indicating that the model can truly reflect The actual situation at the scene proves the accuracy of the numerical simulation results.