【作者】 王腾；

【导师】 谢康和；

【作者基本信息】 浙江大学 ， 岩土工程， 2001， 博士

【摘要】 桩的纵向振动理论是桩各种动态测试方法的理论基础，开展桩纵向振动理论的研究对于进一步弄清桩—土间动力相互作用、动力试桩的机理以及正确分析试桩测试曲线是非常重要的。 在总结前人研究成果的基础上，本文采用新的思路和方法对成层土中完整桩、变截面桩和变模量的纵向振动特性进行了研究，主要工作有： 地基土主要的特征之一是成层性，因此有必要研究成层土中桩的纵向振动特性。本文利用拉氏变换的方法并结合阻抗函数的传递性，求得了成层土中桩在任意激振力作用下桩顶阻抗的解析表达式，进而求得半正弦脉冲作用下的速度响应的半解析解，在此基础上讨论了土层模量的变化对桩—土体系的动刚度、动阻尼以及速度导纳曲线和反射波曲线的影响，并分析了土模量变化对响应曲线的影响与桩身缺陷影响的区别，以正确识别响应曲线。 由于工程中桩基质量检测的主要对象是各类缺陷桩，因此本文将重点放在研究各种缺陷桩的振动特性。根据桩身缺陷的分类，缺陷桩可归结为两种：变截面桩和变模量桩。本文分别求得了任意段变截面桩速度响应的半解析解以及任意段变模量桩速度响应的解析解并推广至成层土中任意段缺陷桩速度响应的半解析解。在此基础上，讨论了桩身缺陷程度、缺陷段长度、缺陷段位置、激励频率以及桩材阻尼等对缺陷桩振动特性的影响，比较了变截面桩与变模量桩振动响应的差异。同时还将理论解的导纳曲线和反射波曲线与工程实测曲线相比较，发现两者符合的很好，说明了理论解的正确性。 最后，采用三维有限元方法讨论了桩及土的三维效应对桩振动特性的影响、非轴对称缺陷桩的振动特性以及与轴对称缺陷桩的区别，并与本文的一维理论解进行了比较。更多还原

【Abstract】 Longitudinal vibration theory of pile is the basis of any kind of method in dynamic pile testing, which can be used to explain the dynamic reaction between pile and soil, the mechanics of pile testing, and to illustrate the pile testing curves.In this dissertation, on the basis of the existing work, the longitudinal vibration properties of the pile with defects in layered soils have been studied with a totally new approach. The main original work includes:Firstly, it is necessary to study the vibration behavior of pile in layered soils since layered property is one of the main characteristics of soil stratum. With Laplace transforms, the analytical expression of the impedance function is derived for the pile in layered soils subjected to an exciting force at its top. Then a semi-analytical solution of the velocity response in time-domain under semi-sine exciting force is given. Based on the solutions, the influence of soil modulus on the dynamic stiffness and the dynamic-damping of the system of pile and soil, and that on the curves of mechanical admittance and the reflection wave of pile are analyzed. In order to explain the response curves of pile correctly, the curves corresponding to soil modulus varying are compared with the ones corresponding to defective pile.Secondly, since the main objective of performing dynamic pile testing is to evaluate the integrity of drill shafts definitively, the study is focused on the vibration properties of defective pile. The defective piles fall into two categories according to the causes they formed: one is the pile with variable sections, the other is the pile with variable modulus. In the dissertation, a semi-analytical solution for a pile of arbitrary segments with variable section area and an analytical one for a pile of arbitrary segments with variable modulus are derived respectively. The solutions are then extended in a semi-analytical form to the defective pile with arbitrary segments in layered soils. Using these solutions, the influences on the vibration properties caused by the degree of pile defects, the length and the location of the defects, the exciting frequency and the damping of pile material are studied. Comparison is also made for the vibration properties of the pile with variable section and the’one with variable modulus. Furthermore, to verify the theory developed herein, the fitted curves of analytical solutions are compared with the field measured ones, which shows that they are in a good agreement.Finally, by means of 3D finite element method, the influence of "3D effect" on the vibration properties of the defective pile is studied, and the difference of vibration properties between the pile with un-axial defect and the one with axial defect is compared. Moreover, the result obtained from 3D FEM and the one from ID analytical solution developed in the dissertation are compared.更多还原