Research On Deformation Monitoring And Deformation Law Of Foundation Pit In A Subway Station In Xi'an

Nowadays,as development of the city,the depth and scope of the excavation is increasing,which will lead to many problems,such as the safety and stability of the foundation pit and the influence for the surrounding environment.However,based on the complexity of the foundation pit,the deformation law of the deep foundation pit still needs to be analyzed.This paper does the deformation analysis of a subway in Xi'an and the guidance to the design and construction of the deep foundation pit engineering enclosure system.With the basis of field monitoring,this paper adopts the theory of the stability of the foundation pit and the FLCA3D finite element simulation software,analyzes the change trend of the horizontal displacement of the retaining pile body,the settlement of the bottom edge of the foundation pit and the axial force of the inner support.By comparing the field monitoring data,this paper draws following conclusions:(1)Through analyzing the filed monitoring data,it can be found that with the increase of the depth of the excavation,the horizontal displacement of the retaining structure gradually increases along the depth direction,and the maximum horizontal displacement gradually moves down,showing a "parabolic" distribution.The surface settlement around the foundation pit is near the direction of the foundation pit along the direction of the foundation pit,which maximum settlement is about 8m away from the foundation pit.The axial force value of the steel support fluctuates and the overall stability is basically maintained.(2)The numerical simulation results are basically the same with the measured results.It is feasible to simulate the actual excavation process by FLAC3D simulation software,and can be used to predict the deformation of the foundation pit that has a certain guiding significance to the actual construction.(3)The long pile will cause the control of the deformation smaller and affect economic.On the contrary,foundation pit will be deformed and the foundation pit safety and analyzing,the length of 23m-25m in the foundation pit is relatively safe,economical and reliable.The increase of the distance between the pile and the pile will increase the horizontal displacement and the surface settlement of the enclosure structure.In a certain degree,the influence area of the surface settlement around the foundation pit becomes larger.Therefore,in order to make sure the safety of the construction,the value of the pile spacing is 1.4m to 1.8m.With the increase of steel support spacing,the horizontal displacement of the retaining structure and the settlement of the ground surface around the foundation pit will increase,and the law of the change is basically the same.The analysis data shows that the support spacing is suitable for 3m~6m.