Influence Of Shield Tunneling On The Pile Foundations And Surrounding Soil Masses

Along with the rapid development of urban underground space and rail transportation,especially in the construction of buildings and pipelines,the construction of the new subway tunnel near the crossing is common.With the continuous advance of shield tunneling,the tunnel excavation boundary to a certain range of the depth of the formation of a certain range of stress redistribution,induced deformation and surface subsidence around the tunnel,at the same time to ensure the construction of adjacent buildings,underground pipe network and other structural safety and normal use,the surrounding strata should be controlled within the allowable range.Because of the existing pile foundation is often built before the shield tunnel,the stress and deformation of the pile foundation is not available,and the influence factors of the construction are complex and changeable.Therefore,how to predict the process of shield tunnel construction on the additional impact force and deformation of the existing building pile foundation,and puts forward the reasonable countermeasures,is the process of metro construction urgently needs to solve the problem.This paper combined with the shield of Fuzhou Metro Line 1 through the Xi Ma Bridge,by the construction monitoring and numerical simulation,research and analysis of influencing factors of shield excavation on adjacent piles and soil,the work done in this paper and the conclusion are as follows.(1)By means of field monitoring,the influence of shield tunnel excavation on the surrounding soil is studied under the condition of close to the pile foundation.The influence of shield tunneling on the surrounding soil layer is analyzed,and the variation of the surface soil,the soil horizontal displacement and the earth pressure at different depth is analyzed.(2)The Hardening Soil constitutive model can better respond to the excavation of shield tunnel,this paper analyzes the influence of shield tunnel excavation on the adjacent underground structure.In the process of numerical calculation,the Studio Visual software is used to develop the constitutive model of the Hardening Soil.(3)Taking Fuzhou Rail Transit Line 1 underpassing Xi Ma Bridge engineering as the background,establishing a three-dimensional numerical model of shield crossing existing pile foundation to analyze the internal force and deformation of adjacent pile foundation,internal force of tunnel lining soil,horizontal displacement of soil and surface settlement.(4)Based on the above background,four factors are simulated by changing the depth of the tunnel,the friction angle of the soil,the cohesion of soil,the distance between the tunnel center line and the pile foundation.Through the regression analysis,the change law of the general field condition and the back pile foundation are studied,and the empirical formula of the horizontal displacement of the soil is fitted.