【作者】 胡昌斌；

【导师】 谢康和； 王奎华；

【作者基本信息】 浙江大学 ， 岩土工程， 2003， 博士

【摘要】 本文从三维轴对称土模型出发，较系统地对考虑桩周土竖向波动效应、任意桩底支承边界条件下、成层粘弹性土中完整桩及变阻抗桩与土纵向耦合振动理论及其工程应用进行了研究。主要工作包括： 1、在考虑桩周土三维波动条件下，对滞回阻尼、粘性阻尼单层均质土中桩土纵向耦合振动问题进行了解析研究，分别得到桩顶位移、速度频域响应以及复刚度的严格解析表达，以及半正弦脉冲激振力作用下桩顶时域响应半解析解。基于所得解对桩土动力耦合作用的内在机理、粘弹性土层动力反应特性进行了分析，并重点讨论了桩侧土不同形式材料阻尼对桩顶动力响应的影响。研究表明，对于桩顶响应，桩侧土的粘性材料阻尼呈现出与滞回阻尼明显不同的影响特点。 2、对刚性支承、有限厚度土层支承和半无限空间支承三种桩底部支承情况下桩底支承复刚度和桩周土底分布支承复刚度的解析表达及其特性进行了推导论证，通过假定桩底土为与桩等截面的土柱推导求得有限厚土层支承条件下桩底支承复刚度的解析解，并据此分析了不同底部支承边界对桩顶响应的影响。 3、将基于平面应变简化假定和Winkler模型的桩振动理论解与本文严格理论解对比，分析校验了平面应变简化假定和Winkler模型在桩基振动理论应用中的适用性，具体比较范围涉及土层对桩的局部复阻抗、桩顶幅频响应、速度导纳、桩顶复刚度、桩顶时域响应等方面，并得到若干重要结论。 4、从三维轴对称土模型出发，对考虑桩土耦合作用、土层层间联系以及桩周土竖向应力梯度变化条件下的成层粘弹性土中完整桩及变阻抗桩系统纵向振动问题进行了研究，提出了成层土中变阻抗桩系统纵向振动问题的近似解析解法和桩周土层层间相互作用的简化而实用的数学模型，并利用拉氏变换和阻抗函数的传递性，获得了成层土中任意段变阻抗桩桩顶阻抗函数的解析表达式，以及桩顶速度导纳和时域速度响应解析解和半解析解。 5、利用所得解，对成层土中完整桩、变截面、变模量桩的振动特性进行了较系统的分析，并重点讨论了土层模量、桩身缺陷程度、埋身、缺陷段长度、激振频率等对桩项复刚度、桩顶反射波曲线、导纳曲线的影响，得到了许多重要结论。 6、将本文理论解与其它现有理论解及数值解进行了充分对比，讨论分析了各解法求解特点，验证了本文解的正确性和适用性。同时将本文解应用于桩基动测曲线分析工作中，通过与工程实测曲线的反演拟合和正演分析，检验了本文理论解的实用性。结果表明，本文解具有良好的通用性和适用性，并可大大提高反演分析的可靠性。 本文给出的桩土纵向祸合振动理论解较现有其它解理论上更严格先进，应用上更可靠实用。这不仅使桩基振动理论更为完善，也为桩基抗震、防震设计以及桩基动测提供了全新的理论支持。更多还原

【Abstract】 On the basis of three-dimensional axially symmetrical soil model and taking consideration of vertical wave effect of soil layer, the interaction between visco-elastic layered soil and an integral pile or a multi-defective pile with arbitrary bottom boundaries and its engineering application is systematically studied in this dissertation. The main original work includes:1. The interaction between an integral pile and a uniform visco-elastic soil layer with viscous damping or hysteretic damping is theoretically studied, and the pile response to a harmonic load is obtained in a closed form and used to define complex stiffness at the pile head. Semi-analytical solution of the velocity response in time domain subjected to a semi-sine wave exciting force is also given. Based on these solutions, a parametric study is conducted to determine the main features of the soil-pile system vibration, and the special influence of viscous damping of soil layer around pile is discussed. It indicates that viscous damping of soil layer shows a clear different effect on dynamic response at pile head comparing to hysteretic damping.2. The complex stiffness corresponding to three bearing conditions of semi-infinite elastic subgrade, finite elastic soil layer and end bearing at the pile bottom are theoretically investigated, and analytical expression of the complex stiffness corresponding to finite elastic soil layer bearing condition is obtained. The special influence of bearing conditions on dynamic response at pile head is then discussed.3. By comparing the available theories corresponding to plane strain model and Winkler model with the solutions developed in this paper, the applicability of the two models is analyzed and checked. The comparison involves many aspects such as local soil stiffness, dynamic stiffness and time domain response at the pile head, and some important conclusions are made.4. With the consideration of the vertical wave effect of soil and soil-pile interaction, an approximate analytical solution to vertical vibration of pile system with variable impedance in visco-elastic layered soil is developed. A simplified and practicalmathematical model for interaction between soil layers is proposed, and its applicability is theoretically investigated . Based on this model and by using Laplace transforms and the transmit property of impedance function, the analytical expression of the impedance function and solutions of the displacement and velocity response function in frequency domain and in time domain at the pile head are derived.5. Based on the solutions developed herein , the main features of the interaction between visco-elastic layered soil and an integral pile or a multi-defective pile are systematically analyzed. The influence on the vibration properties caused by soil modulus, the degree of pile defects, and the length and location of the defects are discussed, and many important conclusions are drawn.6. By making the comparison of the new theory developed in this dissertation and other theories for pile vertical vibration, the correctness and applicability of the new theory is verified. Meanwhile, the fitted curves of analytical solutions are compared with the field measured ones, and it is proved that the theoretical curves are in good agreement with that obtained from the field measurement.In comparison with other theories, the theoretical solutions presented herein for longitudinal vibration of soil-pile system is more rigorous and reasonable in theory, and more reliable and applicable in use. This not only makes the theory of pile vibration more perfect, but also provides a totally new theoretical support for pile foundation seismic design and pile dynamic testing.更多还原