Research On The Influence Of Double-line Shield Tunneling To Neighboring Pile Foundation

In recent years, with the rapid economic development, the process of Hefei’s urbanization is accelerated, then the available land area decreased dramaticaly. In order to meet the needs of people’s transportation, the utilization of underground space has caught people’s attention, so more and more cities begin to build the subway. Among the various methods of constructing subway, the advantage of shield tunneling method is especially obvious, which has become the main method of excavating subway tunnel.Although the development of the shield method has been gradually advanced, but it still can cause disturbance of soil around the tunnel, and will be the basis of the main buildings or structures around the tunnel. What’s more, when land displacement caused by shield excavation is too large, will make the structure bearing capacity drops greatly, so that buildings could not continue to use.Based on the project of Hefei Metro Line3 between Furong road station and Xiyou station shield tunnel crossing neighboring viaduct bridge piles,this paper using the method of MIDAS/GTS numerical simulation to analyzed the law of surface settlement by shield tunneling, and discusses the deformation of piles induced by twin shield tunneling, and achieves the changes law of deformation and internal force of pile foundation caused by different factors,finally summarized the beneficial excavation method to reduce the deformation and internal force of the pile foundation.This article mainly made the following analysis:(1) In refer to a large number of domestic and foreign research scholars’ research results, the research status of the influence of twin shield tunnel excavation on surrounding soil and pile foundation are summarized; The mechanism of soil deformation and pile foundation deformation caused by shield construction is analyzed.(2)Two stage method were reviewed, and analyzed the stress situation of pile foundation caused by shield construction.(3)Using MIDAS/GTS software to analyzed the settlement and horizontal displacement of the ground surface and the tunnel arch.The pile’s deformation under different working conditions during the process of double-line shield advancing are also analyzed.Then the calculation results were compared with two stage method,and the feasibility of the simulation is verified.(4) Different numerical calculation models are established by MIDAS/GTS software. Numerical analyses changed length and position of the piles,space of the piles and the shield excavation sequence to study the features of pile behaviour(vertical displacement,horizontal displacement, additional axial force,additional bending moment) along the pile shaft caused by double-line shield tunnelling.