Study On Deformation And Stress Characteristics Of Pile Foundation Of Adjacent Bridge Along The Line Caused By Shield Tunneling

With the rapid development of China's economy,the use of space on the ground in big cities is increasingly tense.At the same time,the demand of urban electricity is increasing.In order to ensure the safety of electricity,more and more comprehensive pipe corridors and power tunnels are under construction.However,due to the limitation of underground space,the excavation of power tunnel inevitably has an impact on the adjacent buildings,especially the pile foundation of the buildings.Prediction of the impact of tunnel excavation on the surrounding pile foundation has become one of the key research topics.In this paper,MIDAS / GTS,a finite element software,is used to build a three-dimensional solid model for the calculation and analysis of the power tunnel from Luoyong to Xiaobei in Guangzhou.At the same time,the two-stage analytical method is used.The first stage is based on loganathan formula and its modified formula to calculate the soil displacement caused by tunnel excavation.The second stage is based on Pasternak foundation model to analyze the pile displacement and internal force caused by soil displacement and deformation.Combined with the monitoring data for comparative analysis,this paper mainly includes the following work:(1)This paper summarizes the research status of the influence of tunnel excavation on adjacent pile foundation at home and abroad,and the construction principle of shield tunnel excavation,the development process and influencing factors of tunnel excavation on ground settlement,and the mechanical response principle of passive single pile and group pile under the condition of tunnel excavation.(2)Using MIDAS / GTS software,a three-dimensional solid model is established to simulate and analyze the pile foundation of viaduct crossing along the tunnel excavation.The influence of the tunnel excavation on the vertical displacement of the surface and deep soil,the influence of the distance from the pile to the tunnel on the displacement and internal force of the pile body,and the deformation analysis of the pile body in different excavation stages are discussed.The results show that the vertical displacement of the surface and deep soil caused by the tunnel excavation is similar to the peck settlement groove curve,and the maximum vertical displacement appears directly above the tunnel axis.Due to the blocking effect of the pile,the soil outside the pile is little affected by the tunnel excavation.With the increase of the distance between tunnels,the smaller the influence of the tunnel on the pile foundation,the point where the bending moment value of the pile body is zero moves upward,and the peak value of the bending moment curve appears more.The lateral displacement of pile is mainly concentrated in two construction stages from tunnel excavation to pile section.(3)Analytic method is used to calculate the influence of tunnel excavation on Soil and pile foundation around the tunnel.Loganathan formula and its correction formula are used to calculate the displacement of soil around the tunnel.Based on Pasternak foundation model,the influence of tunnel on pile body is analyzed,and the influence of tunnel excavation on pile foundation considering the three-dimensional effect of lateral soil is analyzed.The influences of friction angle,elastic modulus,loss ratio,distance between pile and tunnel and shear layer thickness on the lateral displacement and moment of single pile are discussed.The results show that the modified loganathan formula is more accurate in the calculation of lateral displacement and bending moment of pile foundation based on Pasternak foundation model.(4)According to the relevant specifications and engineering experience,the control standards of ground settlement and pile foundation deformation are determined,and the protection measures and construction monitoring scheme of bridge pile foundation in shield tunneling are summarized.Through the comparative analysis of numerical simulation calculation results and actual monitoring data,the ground settlement and pile foundation deformation caused by tunnel excavation are within the control range of the specifications,indicating the accuracy and accuracy of the numerical analysis Construction is instructive.