| Rapid development of underground engineering,the area of urban exploitable land is less and less.We should make good use of land resources,foundation pits are often located near subway tunnels.The excavation and unloading process of foundation pit will change the original in-situ stress balance,resulting in additional deformation of track structure.If the deformation is too large,it will endanger the safe operation of rail transit and even cause safety accidents in serious cases.At present,there are few studies on the tunnel Tunnel deformation caused by soil movement near the two strong influence areas.Therefore,the development of relevant research is necessary to ensure the long-term safe operation of the subway tunnel.Combined with the specific situation of Kunming Rail Transit,this paper adopts the method of combining on-site monitoring,theoretical analysis and numerical simulation,takes a foundation pit project adjacent to Metro Line 1 and line 4 as the research object,establishes a three-dimensional finite element model by using MIDAS GTS NX finite element software,and systematically analyzes the influence of foundation Soil excavation will inevitably lead to the deformation of relevant structures,Exploring the influencing factors of subway tunnel deformation also provides a certain reference for other similar foundation pit projects.Work content of the paper:(1)Field monitoring data analysisThe dynamic data monitoring of the construction site is analyzed and compared with the monitoring control standard.The analysis shows that the deformation of each monitoring item is within the allowable range of the control standard,the excavation will not endanger the safety of subway tunnel and surrounding roads,and the supporting structure scheme is safe and reliable.(2)Related deformation caused by foundation pit excavationConsult relevant engineering geological and hydrogeological data,use MIDAS GTS NX to simulate excavation conditions,analyze the simulation results,including foundation pit support structure deformation analysis,tunnel deformation analysis and soil deformation analysis,and compare the simulation results with the actual monitoring data to prove the reliability of numerical simulation in this paper.The research results show that the deformation of structures including tunnel,supporting pile,surface and column are within the allowable range of the control standard,the excavation of foundation pit will not endanger the safe operation of adjacent subway,and the foundation pit support scheme is safe and reliable.(3)Study on Influencing Factors of subway tunnel deformationUsing finite element software MIDAS to simulate multiple working conditions such as different excavation depth,different retaining pile diameter,different cohesion and different internal friction angle.The numerical results are compared with the actual data model results to analyze the influence of different influencing factors on the deformation of subway tunnel.The results show that each influencing factor has an obvious influence on the tunnel deformation,and the largest influencing Friction angle of soil.Increasing the stiffness of the supporting structure or strengthening the soil has a significant effect on controlling the deformation of each structure.Innovation of the paper:(1)The supporting project studied in this paper is relatively special.It is Metro Line 1 and line 4 distributed in the north and south of the foundation pit respectively,and they are all located in the strong influence area of foundation pit excavation.At present,there is little research on such special projects;(2)This paper simulates the deformation influence of foundation pit excavation on adjacent subway tunnels under different influencing factors,so as to explore the deformation law and influencing factors of subway tunnels,and obtain the best reinforcement scheme and avoid the adverse factors of excavation,which has high research value and reference significance. |
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