Study On The Influence Of Foundation Pit Excavation On Deformation Of Existing Tunnels

In the construction of contemporary cities,the construction of existing subway tunnels is often encountered.Therefore,the displacement deformation of the tunnels must be strictly controlled during construction.In this paper,the software Midas/GTS is used to simulate and analyze the influence of foundation pit construction on tunnel deformation.The content and conclusions of this paper are as follows1.Deformation characteristics of foundation pits during foundation pit construction are introduced from the aspects of deformation of foundation pit support structure,uplift of pit bottom and surface settlement of soil around foundation pit;from deformation of retaining structure,time effect,groundwater control etc.The main factors affecting the tunnel deformation during foundation pit excavation are introduced.The calculation method of tunnel deformation caused by foundation pit excavation,settlement settlement around foundation pit and rebound amount of foundation pit is introduced.2.Based on certain assumptions,a three-dimensional model analysis is established to study the influence of foundation pit excavation on the deformation of adjacent tunnels.Mainly consider the relative position of the tunnel and the foundation pit,that is,the side and bottom of the tunnel.3.Through numerical simulation,the following conclusions are drawn:(1)With the construction of the foundation pit,the horizontal displacement of the underground continuous wall increases,and the horizontal displacement and vertical displacement of the tunnel increase.With the construction of the foundation pit,the bending moment of the underground continuous wall increases,resulting in the largest The position of the positive bending moment(205.60kN·m)is near the buried depth of 5m,and the maximum negative bending moment(-186.93kN·m)is located at the buried depth of 13m;the surface subsidence area is mainly between 0～30m from the side of the foundation pit,and is close to The settlement of the foundation pit area is large;the maximum tensile stress of the model tunnel is 0.930MPa,and the maximum compressive stress is 0.871MPa,so the C30 concrete meets the requirements(2)In the case of lying on the side of the tunnel,the horizontal displacement(arched shoulder)is the largest when the tunnel center to the edge of the foundation pit is about 9 m;when the distance is about 9 m,the vertical displacement(arch waist)generated by the tunnel is the largest(3)Under the condition that the distance from the tunnel to the pit is constant,the horizontal displacement and vertical displacement of the tunnel decrease significantly when the tunnel descends;when it is not lowered,the horizontal displacement and vertical displacement of the tunnel are relatively large.(4)The horizontal displacement of the tunnel increases with the construction of the foundation pit and the maximum value is mainly located at the arch waist;the vertical displacement of the tunnel increases with the construction of the foundation pit and the maximum value is located at the vault.(5)Under different buried depths,the horizontal displacement and vertical displacement of the tunnel decrease with the increase of the buried depth,and the maximum horizontal displacement is located at the arch waist,and the maximum vertical displacement is mainly at the arch shoulder.(6)In the case of fixed tunnel depth,when the lateral displacement distance is 0～6m,the horizontal displacement of the tunnel increases with the increase of the lateral displacement distance;when the lateral displacement distance is greater than 7m,the horizontal displacement of the tunnel decreases significantlyAs the tunnel side shift distance increases,the vertical displacement generated by the tunnel is decreasing.Figure[101]Table[17]Reference[57]...