Analysis Of The Influence Of Foundation Pit Excavation On Adjacent Subway Tunnel In Beijing

The foundation pit engineering has a great influence on the surrounding environment,which will cause the displacement,deformation and destruction of adjacent buildings,roads,pipelines and so on.When the foundation pit adjacent to the existing subway tunnel,it is necessary to take appropriate measures to strictly control the deformation of the retaining structure and surrounding soil,reduce the influence of the tunnel,and ensure the safe operation of the subway.In this paper,based on the foundation pit engineering of a nearby subway tunnel in Beijing,the influence of foundation pit excavation on the adjacent tunnel deformation is analyzed by means of numerical simulation.The main contents and conclusions are as follows:(1)Introduced the retaining structure of foundation pit deformation,uplift and surface subsidence and deformation mechanism of the pit,and the related theory and calculation method of deformation.This paper analyzes the potential causes of tunnel deformation caused by foundation pit engineering,and introduces the calculation theory and method of tunnel deformation caused by foundation pit excavation.(2)Using Lizheng software to design and calculation the supporting scheme of foundation pit,check the relevant safety coefficient and the stability of foundation pit deformation,and verify the safety of the supporting scheme.Then using FLAC3 D software to establish the numerical model of the side wall of the adjacent subway tunnel,the deformation of the foundation pit during the construction process and the deformation of the adjacent tunnel are simulated and analyzed.(3)Comparison the data of the side wall's horizontal displacement,the ground surface's settlement and the bottom heave from Lizheng software,FLAC3 D software and the monitoring,analyzes the difference between the data from different sources,verify the correctness of the model.(4)Through the simulation calculation,we found,because of adjacent foundation pit excavation,the subway tunnel will have a horizontal displacement towards the foundation pit,the maximum horizontal displacement is 3.31 mm.Meanwhile,the adjacent foundation pit excavation will cause the tunnel uplift towards the ground surface,the maximum vertical displacement is 3.58 mm.Those displacements meet the design requirements of the safe operation of the subway.The research of this paper has certain reference value for the design of similar projects.