大直径桩—非均质土耦合振动理论研究

发布时间：2018-05-07 11:15

本文选题：大直径桩 + 横向惯性　；参考：《苏州科技学院》2015年硕士论文

【摘要】：大直径桩因其更高的承载力和更小的沉降变形等特性而广泛应用于高层建筑、道路和桥梁等大型工程中。但由于桩身特殊的几何尺寸,其工作性状无法简单地应用和借鉴以往的桩基理论。目前,相比静载作用下大直径的工作性状研究,对于大直径的纵向动力特性的研究比较匮乏。鉴于此,本文一方面在理论上对大直径桩的桩身、桩侧土与桩身的相互关系、桩端土对桩身的支承作用做了简化模型的处理,采用解析方法较系统地研究了均质地基和非均质地基中大直径桩的桩-土耦合纵向振动问题。另一方面采用ANSYS/LS-DYNA对大直径桩-土耦合纵向振动问题进行有限元数值模拟,验证数值分析的可行性。论文的具体研究内容有以下几个方面：(1)基于平面应变模型和Rayleigh-Love杆模型,研究粘弹性支承条件下均质土中大直径桩的纵向振动问题。采用积分变换法,解析推导得到激振脉冲作用下桩顶动力响应的理论解。并基于所得的理论解,研究大直径桩身的特性参数——泊松比、桩径、桩长和纵波波速等对桩顶振动特性(速度时域曲线、速度频域曲线、动刚度和动阻尼曲线)的影响。(2)将桩端土粘弹性支承模型替换为类似于一维杆的扩散虚土桩模型,研究径向非均质士中大直径桩的纵向振动问题。采用积分变换方法和阻抗函数递推法,推导得到激振脉冲作用下桩顶频域响应的解析解和时域响应半解析解。并基于所得的理论解,研究扩散虚土桩的特性参数——划分精度、虚土桩长度、扩散角和虚土桩纵波波速等对桩顶振动特性的影响。(3)结合考虑大直径桩成桩效应引起的桩侧土体施工软(硬)化和桩侧土纵向成层性,基于扩散虚土桩模型和复刚度传递的多圈层平面应变模型建立桩侧土体双向非均质情况下大直径桩纵向振动的定解问题。利用环向剪切复刚度传递法和阻抗函数传递法,推导得到桩顶动力响应的理论解。通过参数分析法,研究径向扰动程度、扰动范围、纵向软(硬)夹层厚度、桩身密度等因素对桩顶振动特性的影响机理。(4)利用ANSYS/LS-DYNA建立桩-土耦合模型,分别建立理论求解时桩径的变化、虚土桩桩长变化、桩侧土纵向存在软(硬)夹层和桩侧土径向施工软(硬)化对应的有限元模型,进行数值计算,并和相同工况下的理论解进行对比分析,验证两种方法的正确性和可行性。(5)总结本文的研究成果和需要改进的地方,并对大直径桩-非均质土纵向耦合振动的后续研究提出展望。
[Abstract]:Large diameter piles are widely used in high-rise buildings, roads and bridges because of their higher bearing capacity and smaller settlement and deformation. However, because of the special geometric size of the pile body, its working characteristics can not be simply applied and used for reference to the previous pile foundation theory. At present, compared with the study of working characteristics of large diameter under static load, the study on longitudinal dynamic characteristics of large diameter is relatively scarce. In view of this, on the one hand, this paper theoretically deals with the relationship between the pile body, the side soil and the pile body of the large diameter pile, and the supporting effect of the pile end soil on the pile body. The pile-soil coupling longitudinal vibration of large diameter piles in homogeneous and heterogeneous foundations is studied systematically by analytical method. On the other hand, the finite element numerical simulation of large diameter pile-soil coupling longitudinal vibration problem is carried out by using ANSYS/LS-DYNA to verify the feasibility of numerical analysis. Based on the plane strain model and the Rayleigh-Love rod model, the longitudinal vibration of large diameter piles in homogeneous soil with viscoelastic support is studied. By using the integral transformation method, the theoretical solution of the dynamic response of the pile top under the action of the exciting pulse is derived analytically. Based on the theoretical solutions obtained, the vibration characteristics of pile top (velocity time domain curve, velocity frequency domain curve), such as Poisson's ratio, pile diameter, pile length and longitudinal wave velocity, are studied. The influence of dynamic stiffness and dynamic damping curve. (2) replacing the viscoelastic support model of pile end with the model of diffusion soil pile similar to one dimensional rod, the longitudinal vibration of medium and large diameter pile with radial heterogeneity is studied. By using the integral transformation method and the impedance function recursive method, the analytical solution and the semi-analytical solution of the pile top response in frequency domain and in time domain are derived. Based on the theoretical solution, the characteristic parameter of diffusion virtual soil pile, the partition precision, the length of virtual soil pile, is studied. The influence of diffusion angle and longitudinal wave velocity of virtual soil pile on the vibration characteristics of pile top. (3) considering the soft (hard) construction of pile side soil and longitudinal stratification of pile side soil caused by pile formation effect of large diameter pile. Based on the diffusion fictitious soil pile model and the multilayer plane strain model of complex stiffness transfer, the solution of longitudinal vibration of large diameter pile under bidirectional heterogeneity of soil on the side of pile is established. The theoretical solution of the dynamic response of the pile top is derived by using the toroidal shear complex stiffness transfer method and the impedance function transfer method. Through parameter analysis, the influence mechanism of radial disturbance degree, disturbance range, longitudinal soft (hard) interlayer thickness and pile density on the vibration characteristics of pile top is studied. (4) the pile-soil coupling model is established by ANSYS/LS-DYNA. The finite element models corresponding to the variation of pile diameter, the length of fictitious soil pile, the longitudinal soft (hard) intercalation of pile side soil and the soft (hard) soft (hard) construction of pile side soil are established respectively, and the numerical calculation is carried out. And compared with the theoretical solution under the same working conditions to verify the correctness and feasibility of the two methods. The future research on longitudinal coupling vibration of large diameter pile-heterogeneous soil is presented.
【学位授予单位】：苏州科技学院
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU473.1

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