Study On The Influence Of Double-line Shield Tunnelling On Neighboring Pile Foundation

With the rapid development of social economy and the acceleration of urbanization process,major cities are vigorously developing public transportation and the mileage of urban subways is constantly increasing.During the construction of subway,it is inevitable that tunnels will pass through the existing structures in close proximity,and it is particularly important to ensure the safety of existing structures and shield tunnels in the process of passing through existing structures.In view of this,by means of data investigation,theoretical analysis and numerical simulation,this paper studies the deformation law of stratum and neighboring pile foundation,the influence of horizontal deviation of shield on neighboring pile foundation and the protection technology of neighboring pile foundation in the course of double-line shield tunnel passing through neighboring pile foundation.The main research results are as follows:(1)Based on the theory of hole expansion,the principle of virtual image method and Mindlin's elastic solution,the analytical formulas of ground displacement field caused by stratum loss,additional support force,shield shell friction force and cutter head torsion in shield construction are obtained.The three-dimensional ground settlement caused by shield construction is analyzed,and the three-dimensional ground settlement form is revealed.(2)A three-dimensional numerical model of shield tunnel-stratum-neighboring pile foundation is established.The deformation law of stratum during shield tunnel construction is studied.The variation law of horizontal displacement of neighboring pile foundation and the stress characteristics of pile side friction,pile shaft stress and pile tip resistance are analyzed.(3)A three-dimensional numerical model of shield-stratum is established to determine the distribution characteristics of contact pressure under the horizontal deviation attitude of shield,and a load model of shield-stratum is proposed.The effect of shield on stratum is simulated by applying pressure and friction force on the stratum in the numerical model of shield tunnel passing through neighboring pile foundation.The simulation of shield passing through neighboring pile foundation with deviation attitude is realized.The influence of shield tunnelling on neighboring pile foundation under different horizontal deviation directions and deviation angles is studied.(4)A three-dimensional finite element numerical model is established to simulate shield tunnel excavation under different reinforcement areas,depth and thickness.The influence of reinforcement area,depth and thickness on the protection effect of neighboring pile foundation is analyzed,and a reasonable reinforcement range is proposed.