Influence Of Shield Tunnel Crossing Wuhan Guangzhou High-speed Rail Viaduct On Its Pile Foundation

With the rapid development of urban subway and high-speed railway construction,shield tunnel sometimes will inevitably pass through the foundations of high-speed bridge pile,which will have a certain influence on the safety and stability of pile foundations.This article relies on the Wuhan-Guangzhou high-speed rail viaduct tunnel project of the No.11 line of Wuhan Rail Transit Line No.1 line from the Middle Road Station to the Food and Drug Administration station section tunnel.Using on-site monitoring and numerical simulation methods,a systematic study of the deformation and force distribution law of the shield tunnel across the high-speed railway viaduct pile foundation was conducted.The main research contents and results are as follows:(1)Systematic review of the research status of the effect of shield tunnel construction on strata and pile foundations,and points out problems that need to be solved in these studies.(2)The formation deformation caused by tunnel shield construction and the deformation mechanism of pile foundation are summarized,which provides a theoretical basis for the following numerical simulation.The formula for the maximum ground settlement value under Wei Xinjiang’s conical load model was supplemented,and the formula for the maximum ground settlement value under the parabolic and cosine load models was proposed.Through comparison of engineering examples,it was found that the cosine load model proposed in this paper.The maximum ground settlement formula is closer to the measured value.(3)According to the measured data of the shield tunnel crossing the High Rail Viaduct,the surface settlement,the pier and the deformation of the beam body around the pile foundation are statistically analyzed.The results show that the ground subsidence caused by tunnel shield construction mainly occurs in the stage of Shield Crossing,which accounts for about 60% of the total settlement.After the shield has left the monitoring section 45 m,the settlement curve tends to be slow,and the two grouting will make an obvious recovery of the settlement curve.The vertical and horizontal displacement of the pier caused by the shield construction are very small,and the displacement of the shield during the crossing period accounts for about 70% of the total displacement,and the vertical and horizontal displacement of the beam are mainly caused by the shield crossing.(4)The three-dimensional finite element numerical calculation model was established by MIDAS-GTS,and the construction process of the shield tunnel crossing the high iron elevated bridge pile foundation is simulated.The stress and deformation law of the pile foundation,the pier and the beam body of the high iron viaduct are analyzed.The results show that the distance between the pile foundation and the tunnel is different,the deformation and the stress laws of the tunnel are different,the horizontal deformation of the inner pile near the tunnel is obviously larger than the horizontal deformation of the lateral pile,and the change of the pile foundation bending moment of the shield tunnel is far greater than the change of the axial force.The simulated values of ground settlement,pier and beam vertical displacement basically agree with the measured values,and the size and parameters of the models are reasonable.(5)Study on the influence of shield construction control measures of pile foundation by numerical simulation and analysis of soil pressure,the segment Jack pressure and elastic modulus and Pressure Grouting grouting material of these four kinds of construction parameters,variation of axial force,bending moment and vertical displacement and horizontal displacement.The research shows that the soil pressure,the elastic modulus of grouting material has great influence on the pile foundation,when the elastic modulus of grouting material increases to a certain value,the change of pile shaft force and displacement tends to be stable;The increase of internal force of segment Jack pressure,grouting pressure and deformation of pile increases,but little change.