Research Of Deformation Of Existing Subway Tunnel And Soil Induced By Excavation Engineering

With the rapid development of social economy,urban construction,a nd urbanization process,the increasingly serious shortage of land,and the land using from two-dimensional to three-dimensional,the overall development of over ground and underground space becomes the important mode of urban land using.Because of its depth,construction safety,effects on other buildings,structures,and surrounding pipelines,deep foundation excavation becomes a complex problem in construction.Through the effective controlling of deep foundation excavation deformation,which can guarantee the safety of construction and the surrounding environment.In this paper,the influence of the whole process of the deep foundation pit project on the adjacent subway tunnel is studied.The excavation of the foundation pit is analyzed,and the surro unding environment,especially the influence mechanism of tunnel deformation.On the basis of the measured research,the influence of the excavation on the tunnel under different working conditions in the foundation pit construction is analyzed by using the finite element analysis.The following conclusions are obtained:(1)Unloading effects are enhanced to dig deeply on a wide area,which causes soil outside the excavation moves in the excavation,so it induces the vertical and horizontal displacement of Metro tunnel under the influence of the transfer effect of soil deformation.(2)Tunnel deformation mode is related to foundation excavation depth and the tunnel buried depth,tunnel and embedded depth of foundation excavation at the bottom of the relative relationship of different will lead to the different deformation model,the deflect degree and direction of the tunnel.According to the tunnel and the relative position of foundation excavation different partition of the tunnel,mainly divided into the affected area,severe impact area,mildly affected zone,and the position of the region will change according to the different horizontal displacement of foundation excavation retaining structure.(3)The construction process should make full use of time and space effect,the rapid construction of the foundation excavation,the deformation of the subway structure in the future and fully developed to complete the construction,effectively control the subway structure displacement.(4)Under different burial depths,the increase of the bending moment caused by the excavation of the tunnel is closer.The increase of the tunnel bending moment in the depth of 0.8 times the excavation is close to 2.0~2.3,and the excavation of the foundation will affect the interna l force of the tunnel segment in the depth of 0.8 times the foundation excavation.