Study On The Influence Of Foundation Pit Excavation On The Deformation Of Adjacent Subway Section Structure

With the continuous development of urban construction,land resources are constantly developed and utilized.Restricted by urban planning and environment,more and more deep foundation pits are adjacent to urban rail transit.The excavation process of foundation pit will inevitably affect the balance state of surrounding strata,cause redistribution of internal stress in soil mass,and cause additional stress and deformation of rail transit structure.If the deformation is too large,it will affect The normal operation of subway may damage the results of subway and even cause safety accidents.Therefore,it is very necessary to study the influence of foundation pit excavation on the deformation of adjacent track sections.Based on the summary and analysis of the relevant theories of foundation pit deformation,combined with the construction of a deep foundation pit project in Hefei,this paper uses Midas GTS NX finite element software to establish two-dimensional and three-dimensional finite element models,systematically analyzes and studies the deformation effects of foundation pit excavation process on the adjacent track section,and provides certain reference and reference significance for other similar foundation pit projects.The main research contents and achievements are as follows:(1)From the calculation method of the earth pressure around the foundation pit and the deformation mechanism of the foundation pit,this paper summarizes the relevant theories of the excavation deformation of the foundation pit,introduces various influencing factors of the deformation of the foundation pit and the corresponding control measures,and concludes that the main causes of the deformation of the adjacent track section under the excavation of the foundation pit are the uplift of the pit subsoil and the displacement of the retaining structure.(2)Midas GTS is applied to a deep foundation pit near Hefei Rail Transit Line 1 Nx finite element software establishes two-dimensional and three-dimensional models to simulate and analyze the impact on the adjacent track section during the excavation of foundation pit,analyze the stress and deformation of the track section and its auxiliary facilities under the excavation of foundation pit,evaluate the safety of the tunnel section under the excavation of foundation pit in combination with the corresponding Metro specifications,and make comparative analysis based on the measured data.The results show that the maximum horizontal displacement of the track section structure is 2.05 mm,the vertical displacement is 0.85 mm,the maximum horizontal displacement of the auxiliary facilities substation is 0.57 mm,the maximum vertical displacement is 3.79 mm,which is 5mm lower than the control value,and the bearing capacity and crack width of the structure meet the requirements of the code.(3)Combined with the factors related to the deformation of the adjacent track section summarized above,the displacement deformation of the track section during the excavation of the foundation pit is mainly analyzed from the different horizontal distance between the foundation pit and the tunnel,the buried depth of the tunnel,the initial groundwater level,the diameter of the retaining pile and the pile distance.Figure[40]table[20]reference[56]...