土塞对管桩视波速与动力特性的影响机理研究

By virtue of field test and theory analysis, a new objective phenomenon has been discovered by the applicant, which shows that the testing velocity of driven pipe pile can not be simply set to the average stress wave velocity of pile material. It can be obviously seen that the testing velocity of driven pipe pile decreases as the increase of soil plug height. In this project, the conception of Apparent Wave Velocity of Pipe Pile (AWVPP) is defined to describe this new objective phenomenon. Meanwhile, the additional mass model is proposed to simulate the dynamic interaction of soil plug and pipe pile. Firstly, based on the additional mass model, the vertical vibration theories and analytical models for integrate and non-integrate pipe pile are proposed when the coupling vibration of the pile surrounding soil, pipe pile and soil plug is taken into account. Then, by using model test and field test, the reliability and validity of the obtained coupled vibration theories and analytical models are evaluated, and the method for obtaining relevant theoretical model parameters is also provided. Finally, the influence of relevant parameters on the AWVPP and dynamic response of pipe pile are analyzed, especially for the influence of soil plug properties, design parameters of pipe pile, impedance change, welding quality, construction effect and size effect and so on. Based on the above results, the empirical formulas, calculation charts and analysis programs will be provided to reflect the influence of soil plug on the AWVPP and dynamic response of pipe pile. The research results of this project can provide a valuable guide for earthquake-resistance design, dynamic foundation design and various dynamic testing methods of pipe pile.

申请人通过工程试验和理论研究均发现，打入后管桩的测试波速不能简单地按未入土时的桩身材料平均应力波速来取值，而是随着土塞高度的增大而逐渐减小。针对这一新发现的客观现象，本项目拟提出管桩视波速这一动力学概念，并提出附加质量模型来模拟土塞与管桩的动力相互作用。基于附加质量模型，建立一维和三维条件下桩侧土-管桩-土塞耦合振动时完整管桩与变阻抗管桩的纵向振动理论，并综合模型试验、现场试验等研究手段，检验上述耦合振动理论的可靠性和有效性，给出相关理论模型参数的获取方法。分析各有关参数特别是土塞性质、管桩设计参数、桩身阻抗变化、焊缝质量、成桩扰动效应和尺寸效应等因素对管桩视波速和动力特性的影响。在此基础上，建立反映土塞对管桩视波速和动力特性影响规律的经验公式、计算图表和分析程序，从而为管桩基础的抗震、减震设计、动力基础设计及基桩动态测试提供更加完善、实用的理论指导。

申请人通过工程试验和理论研究均发现，打入后管桩的测试波速不能简单地按未入土时的桩身材料平均应力波速来取值，而是随着土塞高度的增大而逐渐减小。针对这一新发现的客观现象，本项目拟提出管桩视波速这一动力学概念，并提出附加质量模型来模拟土塞与管桩的动力相互作用。基于附加质量模型，建立一维和三维条件下桩侧土-管桩-土塞耦合振动时完整管桩与变阻抗管桩的纵向振动理论。主要成果有：①管桩纵向振动理论；②管桩扭转振动理论；③楔形桩纵向和扭转振动理论；④基于虚土桩法的桩基纵向和扭转振动理论；⑤围绕桩基工程的其他理论；⑥围绕桩基工程的专利申请。综合模型试验、现场试验等研究手段，检验上述耦合振动理论的可靠性和有效性，给出相关理论模型参数的获取方法。分析各有关参数特别是土塞性质、管桩设计参数、桩身阻抗变化、焊缝质量、成桩扰动效应和尺寸效应等因素对管桩视波速和动力特性的影响。在此基础上，建立反映土塞对管桩视波速和动力特性影响规律的经验公式、计算图表和分析程序，从而为管桩基础的抗震、减震设计、动力基础设计及基桩动态测试提供更加完善、实用的理论指导。