Research On Structural Deformation Control Of Existing Metro Station Caused By Reconstruction And Extension

With the development of the city,The urban rail transit network has been gradually improved,many new subway lines have to cross some existing stations at close distance due to urban planning.The excavation of these new tunnels will cause the deformation of the existing line structure,which will affect the operation safety of the existing line.Therefore,in the reconstruction of the existing station structure,in addition to its own construction safety,it is particularly important to ensure the safety of the existing structure.In this way,it has become an urgent problem to study the impact of reconstruction on the existing structure and put forward measures to control deformation.In this paper,the Dongsi Shitiao Station of Beijing Metro Line 3 is taken as the research object,and the deformation and control of the station structure of Line 3pre-built during the construction of Line 2 are studied by using the methods and means of the field detection and monitoring,theoretical analysis and numerical simulation.The research results are as follows:1.According to the pre construction inspection results of Dongsi Shitiao station structure of line 3 pre-built during the construction of Beijing Metro Line 2,the residual bearing capacity of Dongsi Shitiao station structure is evaluated by analytic hierarchy process and fuzzy comprehensive evaluation method.The results show that the bearing capacity of the existing Dongsi Shitiao station structure remains 92.61%.2.Adam-BP algorithm is proposed to establish the nonlinear relationship between surface displacement and mechanical parameters of soil.25 groups of test data of orthogonal test are substituted into the neural network for training.The required nonlinear relationship is obtained by adjusting the network accuracy,and the inversion of formation parameters is completed in combination with the field monitoring data.The maximum difference between the final inversion results and the actual values is6.33%.3.The three-dimensional model of Dongsi Shitiao station of Beijing Metro is established to simulate the actual reconstruction process.Combined with the field monitoring data,the deformation law of the existing station structure with the construction is analyzed as follows:(1)When the reconstruction is completed,the settlement deformation value of the existing station structure and track structure exceeds the control value,so the reconstruction process need to be optimized.(2)The excavation and construction of the new main structure caused the uneven settlement of the existing station structure,but the differential settlement value was small and did not exceed the control value.(3)The settlement of the existing station structure caused by the construction of the new main structure is greatly affected by the distance.It is necessary to strengthen monitoring and increase protection measures from the construction of up-lift section.(4)The field monitoring data fluctuates seriously.It might be the impact caused by the vibration caused by the operation of the subway line,or the change of the actual construction scheme,which cause the error in measurement point data.4.According to the deformation distributing principle,the deformation of station structure of existing line 2 and line 3 caused by reconstruction is analyzed by steps,the deformation control measures are studied,and the stepwise deformation control standard is formulated.