Study On Safety-Effect Of Existing Subway Station Under The Construction Of Shallow Excavation And Expansion

Along with our country city population growth and the continuous development of city subway network,city rail transit network will face the expansion and continuous adjustment.In the late stage,the new line and the previously operated line often change and connect,and there are more and more metro station expansion projects.The existing station expansion project is often accompanied with the formation of engineering geology and hydrologic geology,near surface environment of buildings,strict requirements and construction conditions,precipitation conditions are restricted,which requires higher unfavorable factors,so as to carry out the station deformation,which has important application value analysis of construction safety to ensure the effect of the station expansion project both the structure and the surrounding station building safety and stability,can provide an important reference for similar projects.This paper takes the underground excavation project of Laojie Station of Shenzhen Metro Line 1 as the engineering background,and uses FLAC^3D finite difference numerical software to calculate and analyze the safety effects of the project on the structure of the existing station and the surrounding buildings.The main research contents and achievements are as follows:?1?Make a thorough investigation on the case of concealed excavation and expansion project of existing station at home and abroad,and summarize the related construction technology and theoretical research in light of the construction methods of underground excavation and extension adopted by the support project.?2?Through the establishment of numerical analysis model,the excavation of each construction process construction numerical simulation,analysis the formation of existing station structures and building of along the shallow tunnel construction,the construction of pile foundation underpinning,foundation pit excavation and extension station construction and conclusions obtained related effects.The final displacement value and location of each structure:the maximum uplift of the existing station is 2.9mm,and the maximum value occurs at the bottom of the station;the maximum horizontal displacement is 0.38mm,and the maximum value occurs at the bottom of the second floor;the maximum uplift of the railway track is2.1mm,which occurs at the track of the third layer far side.The maximum horizontal displacement is 0.38mm,which occurs in the second layer far side track;the maximum settlement of existing buildings is 16.16mm,which occurs at the junction between the underpinning pile and the ground surface.The numerical simulation results are compared with the field monitoring results.According to the comparison results,the numerical analysis results are basically consistent with the field monitoring results,and the results are in good agreement.The correctness of the numerical model is verified.?3?The theoretical research based on the results of the numerical calculation results were analyzed,summed up the excavation expansion project impact on safety of existing buildings surrounding the station structure.The corresponding monitoring and protection measures are put forward for the high stress and large displacement of existing buildings and stations,and practical construction suggestions are put forward for underground excavation and extension projects and related projects.