Modelling Investigation Into The Effect Of Shield Tunnel Construction Process On Adjacent Pile Foundation In Guangzhou-Zhuhai Intercity Rail Transit

Since the reform and opening up 40 years ago,China’s urbanization process has been deepened,in order to alleviate the pressure of urban traffic congestion.The urban rail transit network in large and medium-sized cities is increasingly dense,it is inevitable that the underground shield tunnel passes through various buildings and pile foundations of structures,because the shield construction will cause disturbance to the surrounding strata.As a result,too much additional internal force and deformation are produced in adjacent pile foundation.So greatly increasing the safety risk of constructions and structures.Therefore,how to ensure the safety of buildings and structures around shield tunnels is a thorny problem in the design and construction of shield tunnels.The study on the influence of shield tunnel construction on adjacent pile foundations has become a hot direction in underground geotechnical engineering.This paper takes the EPB shield tunnel of Guangzhou-Zhuhai intercity rail transit through the Haiqin bridge pile foundation project as the background,and it makes an in-depth study on the influence of the construction process of shield tunnel on the mechanical behavior of adjacent pile foundation by using the methods of literature investigation,theoretical analysis and numerical simulation.The specific work is as follows:Firstly,this paper systematically investigates domestic and foreign literatures.It mainly summarizes and analyzes the research methods and results of this problem,it also focuses on discussing the existence of irrationalities and optimizing and improving some unreasonable places,and to form the research ideas and methods of this article.Secondly,it’s based on the analysis of construction load control.The mechanical analysis model of this problem is established by Mindlin analytical solution in the elastic theory,the influence of three kinds of construction loads,such as shield shell friction,knife head additional thrust,grouting additional pressure,and the loss of soil mass are mainly considered in this model.The variation law of the additional load generated by the shield tunnel construction on the adjacent pile foundation is obtained by programming the Matlab calculation program.Thirdly,it’s based on the two-stage method of displacement control.Using Loganathan analytic solution and load transfer method as principle,the governing equations of pile mechanics are deduced and established from horizontal and vertical directions respectively.The Matlab calculation program is combined with the finite difference method to solve the mechanical behavior of the pile foundation caused by the tunnel construction,which is used as a comparative verification method for numerical simulation.Finally,it uses numerical simulation to carry out further research.By using Midas/GTS geotechnical finite element software,a three-dimensional simulation model of the project is established,in which a variety of shield tunnel construction loads and parameters are considered,and the calculated results are compared with the two-stage method to obtain the corresponding laws.On the basis of this model,investigation into the effect of five main factors on pile foundation,such as: the vertical length-to-depth ratio and horizontal axial distance to clearance ratio between pile foundation and shield tunnel,soil silo pressure and grouting pressure during shield construction,pile foundation stiffness coefficient.