Effect Of Different Anchor Pile Factors Of Existing Underlying Subway Tunnel By Excavation

Excavation of a foundation pit above the upper span subway tunnel will inevitably lead to the displacement of the subway tunnel.In severe cases,it will cause cracks,leaks,and even structural damage in subway tunnel segments.It poses a great threat to the stability and operation safety of the subway tunnel structure.Based on the mechanism of tunnel deformation caused by excavation of foundation pit,this paper theoretically analyzes the deformation of tunnel caused by excavation of foundation pit above subway tunnel.Design and analysis of foundation pit support and tunnel protection scheme.With the help of GTS NX software,the process of excavation of foundation pit above subway tunnel is simulated.A reference is made to the foundation pit project of a university's landscape building as an example to analyze the influence of the three factors of the pile spacing,pile radius,and pile length on the deformation and internal force of the underlying subway tunnel.Optimize the design plan,and compare the optimized numerical simulation results with the measured data.The conclusions of the numerical analysis are as follows:(1)The displacement caused by excavation of foundation pit above the upper span subway tunnel is mainly vertical uplift displacement.The maximum value of the total displacement of the tunnel appears at the top of the lining arch,and the minimum value of the total displacement of the tunnel lining appears at the bottom of the lining arch.(2)In a certain range,the horizontal displacement,axial force and bending moment of the tunnel lining increase with the increase of the distance between the anchor piles.The total displacement and vertical displacement increase obviously.(3)In a certain range,with the increase of anchor pile radius,the horizontal displacement,axial force and bending moment of tunnel lining gradually decrease.The total displacement and vertical displacement decrease obviously.(4)In the range of anchor pile length,with the increase of anchor pile length,the horizontal displacement,axial force and bending moment of tunnel lining decrease slowly.The total displacement and vertical displacement decrease slowly.