Research On Influence Of Foundation Pit Excavation On Subway Tunnel Deformation In Silty Area

With the rapid development of urban traffic,the problem of the crossroads of underground traffic lines and existing subway tunnels is gradually highlighted.Especially,the problems of deformation control of underground tunnels are carried out by using underground excavation.The rebound of unloading soil in the excavation will lead to the vertical uplift deformation of the subway tunnel,which threatens the safety and stability of subway operation.Based on the compressive and resilient properties of the silt in Zhengzhou,this paper systematically studies the deformation characteristics of the subway tunnel under excavation by using the three-dimensional numerical simulation method.The main research contents are as follows:(1)The soil for geotechnical tests,and obtains the main parameters of Cam-clay model of Zhengzhou Eastern silt,such as M=1.414,?=0.066 and ?=0.0021.(2)The effect of excavation on the deformation of subway tunnel is studied by numerical simulation.The theoretical calculation data is in good agreement with the numerical simulation results.(3)The deformation of the subway tunnel under the excavation is studied respectively,when the excavation depth,the distance between the tunnel and the pit or the soil parameter changes.And the effect of the two kinds that block excavation and loading timely or applied uplift pile wall of reinforcement measure on the deformation control of the tunnel is analyzed.The research achievement shows that: The maximum vertical displacement of the tunnel increases gradually with the depth of the excavation,but the increase gradually decreases;The maximum vertical displacement of the tunnel decreases gradually with the increase of the distance between the pit and tends to be gentle;The block excavation measures can reduce the maximum vertical displacement of the tunnel by about 10%,and the reduction of the tunnel displacement is linear with the load;The vertical displacement of the tunnel decreases with the increase of the length of the pile wall,and decreases with the increase of the width of the pile;The thickness of the piled wall has little effect on the control of the tunnel displacement;The vertical displacement of the tunnel increases in the horizontal distance of the uplift pile wall,and when the distance is more than 6m,the uplift pile wall is no longer effective.This paper puts forward the comprehensive measures of block excavation timely loading and the application of uplift pile wall to control the displacement and deformation of the tunnel effectively,and provide a reference to similar projects in the future.