Analysis Of Influence Of Shield Construction On Adjacent Parallel Tunnels

The continuous acceleration of urban processes and the rapid increase in the population of the city will bring tremendous pressure on urban traffic.As the most convenient transportation tool in the city,the subway has been widely used in major cities in recent years.In the limited underground space of the city,subway construction will disturb urban buildings or existing lines,which will seriously affect the safe use of buildings or existing lines.In order to prevent excessive surface settlement and pile top settlement affecting the foundation safety of the ground and surrounding buildings,this paper refers to the engineering example of Hefei Metro Line 5 shield under the completed Line 1 and uses the finite difference software FLAC3 D to explore separately.The disturbance mechanism of the parallel tunnel shield excavation on the surrounding surrounding rock and the surrounding pile foundation.In the numerical model,the built-in command is used to model the soil,the Mohr-Coulomb elastoplastic model is adopted,the lining unit adopts the linear elastic material,and the pile foundation adopts the Pile unit instead of the pile structure.The actual excavation process is simulated by establishing a three-dimensional numerical model.The disturbance of the shield excavation to the surrounding soil,the upper existing line and the adjacent pile foundation was studied.The main research contents and related conclusions of this paper are as follows:(1)Firstly,the movement of the surrounding soil caused by tunnel excavation and the changes of stress and strain of the lining segments were analyzed without considering the existence of the pile foundation.The research shows that the excavation of the lower line has a great influence on the arching and arching of the existing tunnel and the lining stress,and has less influence on the arch bottom of the existing tunnel.(2)Secondly,considering the existence of single piles or group piles in the surrounding environment,the effects of shield excavation on pile foundation and surface settlement are studied.The results show that there are great influences on the surface and existing lines when the pile foundation is around,and the excavation of the construction line will cause great disturbance to the pile foundation.(3)Finally,by changing the length of the single pile and the distance between the pile and the tunnel,the relationship between the settlement of the pile and their relationship is studied.The results show that the settlement of the pile decreases with the increase of the pile length,and decreases with the increase of the distance between the pile and thetunnel.However,the distance between the pile and the tunnel determines the settlement of the pile.