Study On The Influence And Control Of The Underground Excavation Construction Of The Subway Tunnel On The Pile Foundation Of The Adjacent Bridge

Nowadays,with the rapid development of our society,urbanization continues to move forward,and the number of mega cities is also increasing.Along with it,traffic problems such as traffic congestion,frequent accidents,land scarcity and so on are increasingly prominent.In order to solve all kinds of traffic problems,the development of underground space becomes more and more necessary.The development of underground rail transit can not only alleviate various ground traffic problems,but also provide us with a more convenient and fast way to travel.Shallow tunnel excavation is a widely used excavation method in tunnel engineering.Its excavation accuracy can be strictly controlled according to the requirements.There are many protective measures to choose in the construction process.Therefore,it is of great significance to study the influence of shallow tunnel excavation on the short-distance structure.Based on the research background of Shengli East Road Bridge on the side of subway tunnel between Shikui Road station and Labor Park Station of Dalian Metro Line 5,this paper uses MIDAS / GTS numerical simulation software to carry out numerical analysis on the influence of underground excavation construction of subway tunnel on the pile foundation of adjacent existing bridge and the control measures.The main works are as follows:(1)In this paper,the action mechanism of tunnel excavation to the stratum and existing bridge pile foundation is analyzed theoretically.Tunnel construction will disturb the stratum,make the stratum move,affect its adjacent pile foundation,and then cause additional deformation and internal force of pile foundation.The deformation of pile foundation will be transmitted to the upper structure of bridge to generate additional deformation and internal force,which will affect the safe use of bridge.Therefore,the key to control the influence of tunnel excavation on adjacent bridge piles is to control the stratum deformation caused by tunnel excavation.(2)In the process of tunnel excavation,the variation laws of stratum deformation,pile foundation deformation and pile foundation additional internal force under different construction methods and different excavation footage are studied.It is found that in the same horizontal position,the stratum settlement caused by tunnel excavation is the largest at the tunnel axis,and the closer to the axis,the greater the change rate of stratum settlement;the stratum settlement at the same position increases with the increase of the depth of the ground Moreover,the settlement curve is in a groove shape.The deformation of pile foundation increases with the increase of excavation distance.The closer the excavation surface is to the pile foundation,the greater the deformation rate is.The vertical settlement increases unevenly and slowly along the pile axis.The horizontal displacement of the pile bottom is slightly larger than the pile top.After the tunnel excavation,the bending moment of pile foundation increases in both the vertical direction and the direction along the tunnel excavation,and the bending moment of pile body presents a sinusoidal distribution.This paper analyzes the construction difficulty,construction speed,project cost and the settlement of ground and pile foundation by using the method of comprehensive evaluation and analysis of genetic hierarchy process.In order to control the deformation of the surface and pile foundation,it can be concluded that CD method is the best construction method for this project,and the footage of 3M is the best excavation footage for this project.(3)Taking the relative position of the tunnel and the existing pile foundation as H = 2D(D is the diameter of the tunnel),H = 1D,H = 0d and H =-1D,the influence of the relative position of the tunnel and the existing bridge pile on the formation deformation and the existing pile foundation is studied.It is found that the settlement and deformation rate of the stratum at the same horizontal position increase with the increase of the buried depth of the tunnel;the deformation of the pile foundation mainly occurs in the section where the excavation face is relatively close to the pile foundation;the bending moment of the pile body is distributed in a sinusoidal curve,the bending moment along the excavation direction is smaller,and the bending moment in the vertical excavation direction is larger,and the peak value of the bending moment change is about near the tunnel axis.(4)In this paper,several different pile protection measures are described.Combined with the actual project,grouting reinforcement is selected as the reinforcement measures of this research project,and two conditions of reinforcement radius of 1m and 2m are determined.Taking CD method as construction method and excavation footage as 3M,through calculation and comparative analysis,the grouting reinforcement radius of 1m is selected as the grouting reinforcement measures suitable for the project.