Study On Deformation Mechanism Of Tunnel Based On The South Square Of Hefei High Speed Rail Station In Soil Excavation

Currently,Hefei is in the state of rapid development,the size of the city is expanding,anf the original ground traffic has been unable to meet the increasingly crowded urban traffic,the construction of subway can solve the urban traffic problems effectively.At the same time,the development of city ground is quite rapid,this involves the construction of the tunnel above the foundation pit excavation works.The excavation of the foundation pit will affect the stability of the subway tunnel structure.Therefore,it is of great significance to study the deformation mechanism of the existing tunne belowl.The project of south square of Hefei high speed railway station is takes as the background,the method of numerical simulation by finite element software MIDAS/GTS has been taken to analyse and compare the influence of different excavation methods on the deformation of the existing tunnel.The monitoring data are compared with the analog data,and this analyses the influence of excavation on longitudinal deformation of existing tunnel.The main work and conclusions are as follows:(1)Summarize the research on the deformation of the existing tunnel at home and abroad,obtain the deformation law of subway tunnel,The deformation law of subway tunnel is obtained,and put forward of the research methods of this paper.(2)Study the influence of excavation on the deformation of the existing tunnel,and summarize the calculation method of earth pressure,the time and space effect of foundation pit excavation and calculation method of tunnel uplift.Obtain the influence of excavation on the deformation of the existing tunnel,and put forward of the reasonable excavation method.(3)Select the appropriate constitutive model according to the actual construction scheme,simulate the different construction schemes by the finite element software MIDAS/GTS.Analyze and compare the results of tunnel deformation in different construction schemes,study the deformation law of the foundation pit excavation to the tunnel vault,and select the reasonable excavation method.The simulation results shows us that the excavation of foundation pit will cause the longitudinal deformation of subway tunnel,the arch of the tunnel shows a tendency of uplift.Crown upheaval presents the bow of broad in the middle and small both ends.The simulation value of plan three is less than the simulation value of plan two,therefore the excavation scheme of plan three is more favorable to control the longitudinal deformation of tunnel.(4)Analyze and arrange the monitoring data,and compare it with the simulated data,and the rationality of the model is verified.Analyze the influence of excavation on the deformation of the existing tunnel based on the data.The influence of foundation pit excavation on the longitudinal deformation of the existing subway tunnel is related to the distance,the closer the tunnel is,the larger the longitudinal deformation of the tunnel vault is,otherwise the smaller is.