考虑土体竖向波动效应的静钻根植竹节桩纵向振动阻抗研究

针对静钻根植竹节桩这一新桩型特殊的桩身结构及桩土接触条件,基于考虑土体竖向波动效应的三维轴对称模型研究其纵向振动阻抗。首先,采用虚土桩模型模拟桩底土对桩端的支承作用,根据桩周土的成层性和桩身竹节的分布情况,将桩土体系沿纵向划分成有限个微元段,同时,将桩周土沿径向划分为有限个圈层以考虑其径向非均质性;然后,利用Laplace变换和阻抗函数递推方法,得到桩顶频域响应解析解;在此基础上,将退化解与已有文献的解进行对比,证明退化解的合理性;最后,在桩基设计中比较关心的低频范围内分析桩身竹节、桩周水泥土及桩底土参数对静钻根植竹节桩桩顶纵向振动阻抗的影响。

Longitudinal dynamic impedance of static drill rooted nodular pile considering vertical wave effect of soil

The longitudinal dynamic impedance at the head of the static drill rooted nodular pile is investigated based on the three-dimensional axisymmetric model in which only the vertical displacement of the surrounding soil is considered regarding the complexity of the pile body structure and the pile-soil contact conditions. Firstly，the soil reaction acting on the pile tip is simulated with the fictitious soil pile model，and the pile-soil system is divided into a number of segments according to the stratification of the surrounding soil and the distribution of the nodes of the pile. Meanwhile，the surrounding soil is discretized into several annular vertical zones to consider its radial inhomogeneity. Then，the analytical solution for the dynamic response at the pile head in the frequency domain is derived by means of Laplace transform and the impedance function transfer method. The degenerated solution is compared with other solution to verify its reliability. Finally，the influence of pile-soil parameters of the nodes of pile，the surrounding cement-treated soil and the pile tip soil on the dynamic impedance at pile head is investigated within the low frequency domain concerned in the design of dynamic foundation.