地铁隧道开挖对单桩竖向承载力影响分析

隧道开挖会引起周围土层产生位移,使桩基产生附加内力和位移,降低桩身承载力,因此,分析隧道开挖对邻近桩基影响具有非常重要的意义。分三步进行分析,首先采用剪切位移法代入桩基平衡微分方程计算出原始状态下桩身的位移、轴力和桩周摩阻力;然后利用两阶段分析法求解给出隧道开挖对邻近单桩承载力的影响,第一阶段采用Loganathan等提出的解析解计算隧道开挖后引起的桩周土体自由位移;第二阶段基于剪切位移法原理,将土体自由位移施加到桩身,求出隧道开挖引起的桩身附加位移、轴力和摩阻力变化量;最后,将开挖前与开挖引起的桩身轴力和桩周摩阻力进行叠加得开挖后桩身轴力和摩阻力。验算桩身轴力以及摩阻力改变后桩身承载力以及混凝土强度。

Analysis of pile responses caused by metro tunneling

The surrounding soil displacements caused by tunneling will generate additional displacements and axis force of piles, which may reduce the pile bearing capacity, therefore there is a very important significance to analyze single pile responses caused by tunneling. It is analyzed by three steps in this paper. Firstly, taking shear displacement method in equilibrium equations calculates the pile displacement, axial force and friction at the raw state; then, using two-stage method analyzes the impact on pile bearing capacity by tunneling. The analytical solution proposed by Loganathan et al. (1998) is employed to calculate the displacement, axial force and friction of pile after tunneling at the first stage. Based on shearing displacement method, imposing the soil freedom movement on pile to analyze the variation of pile displacement, axial force and friction. At last, the axis force and friction are gain by superimposing the axis force and friction of pile before tunneling over the one caused by tunneling. The pile bearing capacity and concrete strength are checked after the axial force and the frictional changed.