静钻根植竹节桩竖向动力响应研究

基于桩周土径向非均质的平面应变模型,研究静钻根植竹节桩的纵向振动桩顶响应问题。使用剪切复刚度传递方法,得到桩侧剪切复刚度;根据桩身竹节特性,将桩土体系沿纵向划分为有限个微元段,并采用虚土桩模型模拟桩底土对桩端的支承作用;利用拉普拉斯变换和阻抗函数递推方法,同时考虑到桩身的横向惯性效应,利用卷积定理和傅里叶变换,求得瞬态激振力作用下桩顶速度响应的半解析解;在此基础上,对该解进行了合理性验证,与退化解和工程实测曲线进行了对比。最后,分析了竹节半径和间距、桩周水泥土参数及其渗透区域范围、水泥土纵向不均匀性等因素对桩顶动力响应的影响,提出了在静钻根植竹节桩低应变完整性测试中应该注意的相关问题。

Vertical dynamic response of a static drill rooted nodular pile

Based on the planar strain model for radial heterogeneity of soil around a pile, the vertical dynamic response of a static drill rooted nodular pile was investigated. At first, by utilizing the shear complex stiffness transfer method, the shear complex stiffness at the pile side was gained. Then, considering the special structure of the pile, the pile-soil system was divided into finite micro-elements in longitudinal direction, and the pile bottom soil reaction exerted on the pile end was simulated with the fictitious soil pile model. Afterward, using Laplace transformation and the impedance function recursive method, considering the transverse inertia effect of the pile, the semi-analytical solution to the velocity response at the pile top under action of transient excitation was obtained by using the convolution theorem and Fourier transformation. Furthermore, the rationality of the obtained solution was verified, and it was compared with the degenerate solution and the measured curve. Finally, effects of pile pitch radius and spacing, and cement soil around pile’s parameters on the dynamic response at the pile top were analyzed to raise relevant issues paid attention to in low-strain integrity tests of static drill rooted nodular piles.