盾构隧道施工对桩基影响的解析理论研究

Analytical Theoretical Study on the Influence of Shield Tunnel Construction on Pile Foundation

研究目的:基于柱体空腔膨胀理论,引入桩侧荷载传递函数前沿成果,深化了地层应力、地层变形和桩侧荷载传递函数的计算表达式,并以此为基础,研究盾构隧道施工影响下桩基的附加轴力、摩阻力、竖向位移的解析理论以及桩基在隧道不同位置处的力学响应规律,同时辅以有限元计算结果进行对比分析。研究结论:(1)在同一工况、不同荷载传递函数λ值下,桩基附加轴力及附加摩阻力随着λ值的增大而减小,桩基竖向位移不受λ值影响;(2)在不同工况、相同的荷载传递函数λ值下,桩基的竖向位移、桩基附加轴力及附加摩阻力均会随着桩基与隧道的水平距离的增加而减小,竖向位移的减小幅度为0.5 mm/m,附加轴力及附加摩阻力的减小幅度为0.16×2^(n/3-1);(3)通过解析计算结果与有限元计算结果对比分析后发现,荷载传递函数λ取值为2可较好地反映盾构隧道施工对桩基的力学和位移影响。

Research purposes:The cutting-edge methods of cylinder cavity expansion and pile analysis were utilized to optimize the mathematical formula of soil stress and displacement and pile surface load transfer function which were then taken to study the analytical theory of additional axial force,frictional resistance and vertical displacement of pile during TBM advancing.And the mechanics response of the pile is also studied at different relative positions with tunnel.Meantime,the finite element and analytical theory results were compared.Research conclusions:(1)Under same case with different value of,additional axial force and frictional resistance of the pile decrease with the increase of the value of λ,normally vertical displacement of the pile is not affected under this situation.(2)Under different case with same value of λ,vertical displacement,additional axial force and friction resistance decrease with the increase of the horizontal distance between the pile and the tunnel,vertical displacement decreases as 0.5 mm/m,additional axial force and frictional resistance of decrease as 0.16×2^(n/3-1).(3)It is found that load transfer function taking λ=2 can better reflect the influence of shield tunnel construction on the mechanics and displacement of pile foundation by comparing the finite element and analytical theory results.