Study On Dynamic And Static Mechanical Effect Of A New Type Of Pipe Curtain In Tunnel Passing Through Railway-station

With the development of China’s economy and the acceleration of urban infrastructure construction,China has made great efforts to develop public transport facilities such as urban public transport,highway and subway.With the development of underground engineering construction technology,the new pipe curtain method is widely used as a new tunnel construction method.The optimization of the section shape and steel pipe parameters of the new pipe curtain structure,which is the integration of the initial support and the permanent structure,needs further study.In this paper,based on Yingze Street tunnel project,through theoretical analysis and numerical simulation method,the structural deformation law and the optimization of geometric parameters of steel tube curtain under the influence of dynamic and static loads are studied systematically.Combined with the field test data,and compared with the numerical simulation results,the main research results are as follows:(1)In view of the problem that the bearing mechanism of the pipe curtain structure is not clear,the bearing mechanism of the new type of pipe curtain structure is analyzed by using the calculation method of steel-concrete composite structure.The results show that the maximum monitoring values of concrete strain and reinforcement stress are far lower than the maximum value of the bearing capacity of the steel-concrete composite structure,which shows that the steel pipe curtain in the pipe arch plate structure plays a great role in improving the bearing capacity of the structure.(2)For the problem that the tunnel passes through the soft plastic loess stratum and the ground settlement is strictly controlled,through the analysis of the ground settlement law of the tunnel construction and the existing railway settlement standard,considering the most unfavorable conditions,the calculation results show that the allowable value of the ground settlement of the railway line is 12 mm.(3)Combined with theoretical analysis and numerical calculation method,the stress and surrounding soil mass of tunnels with different pipe curtain structure types are analyzed.The results show that the surface settlement and deformation of circular cross-section tunnel is the best,and the vertical displacement and horizontal displacement of tunnel vault and arch bottom are the least.In the rectangular section tunnel support system,the axial force of steel support is the largest,but it is not much different from the other three sections.Combined with the demand of highway tunnel section and other factors,the shape of approximate rectangular section is better for the pipe curtain structure tunnel.(4)In order to find out the influence of steel pipe parameters on the supporting effect of the structure,the mechanical properties of different geometric parameters of the steel pipe in the new pipe curtain structure under the static force are analyzed.The calculation results show that increasing the wall thickness and diameter of the steel pipe in a certain range and reducing the spacing of the steel pipe can effectively improve the supporting effect of the pipe curtain structure.(5)In view of the influence of steel pipe parameters on the supporting effect of pipe curtain structure under the action of train dynamic load,through the analysis of the influence of steel pipe geometric parameters on the pipe curtain structure in 2s time under the action of train dynamic load,through the comparative analysis of different values of steel pipe wall thickness,pipe diameter and spacing,it is concluded that the increase of steel pipe wall thickness and pipe diameter can improve the supporting strength of pipe curtain structure,and the increase of steel pipe spacing can reduce the support effect of pipe curtain structure.(6)Based on the analysis of the monitoring data of the ground subgrade and platform during the construction of the tunnel pipe curtain excavation section,and the comparison with the numerical calculation results,the results show that the difference between them is small,and both are less than the construction control standard,which can ensure the normal operation of trains in the railway station.