Using The Combination Of Geology And Mechanics To Analyze The Role Of Isolated Pile In Underground Engineering Construction

In recent years,with the development and utilization of urban subways and underground space in our country,the deep foundation pit excavation project adjacent to the existing tunnel has attracted our attention.There are many reports on the case of foundation pit excavation causing damage to its neighboring buildings.Firstly,summarizes the study results on the influence between the pit excavation and its adjacent structures,and summarize the shortcoming of existing research,then two-dimensional and three-dimensional finite element models has been established by using ABAQUS.Based on this,the effect of the position and spacing of the isolation piles on the isolated foundation pit and the existing tunnel has been studied,and some beneficial results has been obtained.1.The isolation pile has obvious effect on reducing the horizontal displacement of the existing tunnel lining,and the effect of the isolation pile is more significant as the isolation pile is closer to the tunnel.However,the influence of the isolation pile on the vertical displacement is not significant2.The position of the isolation pile has a great influence on the tunnel bulge,and the closer the isolation pile is to the foundation pit,the better the isolation effect is.However,the variation of the spacing of the isolation pile is not obvious to the ridge.In addition,the uplift effect of the pile on controlling the foundation pit is obvious.3.The isolation pile has obvious effect on reducing the bending moment of the existing tunnel,and mainly occurs on both sides of the tunnel,and the closer the isolation pile is to the existing tunnel,the better the isolation effect.The position has a certain effect on the axial force of the existing tunnel,but it is not obvious,mainly to reduce the axial force value of the tunnel lining near the foundation pit.In addition,the isolation pile has obvious shearing effect,mainly to the upper left and lower right of the tunnel,and the closer the isolation pile is to the existing tunnel the better the isolation effect.4.The existing tunnel has a great influence on the foundation pit retaining structure,and the isolated pile reduces the deformation effect of the existing tunnel on the foundation pit retaining structure.As the spacing of the piles increases,the horizontal displacement of the deep layer of the pile gradually increases.Large,the smaller the spacing of the isolation piles,the more obvious the effect.5.With the different spacing between the isolation pile and the isolation pile,the horizontal displacement of the lining is basically the same,and the maximum horizontal displacement appears in the middle of the lining.The excavation of the foundation pit has a great influence on the adjacent existing tunnel.After the isolation pile is installed between the two,the horizontal displacement of the existing tunnel can be obviously reduced,and the denser the isolation pile is,the more the isolation effect is.it is good.In actual engineering,the impact of the foundation pit excavation on the existing tunnel should be evaluated in advance according to the safe distance of the tunnel specified by local regulations,and the reasonable isolation pile position and spacing should be determined to ensure the stability of the existing tunnel.Next,save engineering costs.