饱和土中非完全黏结管桩纵向振动特性研究

基于Biot动力固结方程和Kelvin模型,考虑了土体三维波动效应及土塞与管桩之间的小变形相对滑移,研究了饱和土中非完全黏结管桩的纵向振动特性.首先,引入势函数,结合桩侧土及土塞的初始和边界条件,采用Laplace变换技术、Helmholtz分解法及分离变量法,分别求解出桩侧土和土塞的纵向振动解.结合桩土系统的耦合条件,进一步求解出管桩顶部的复刚度、速度响应频域解析解及速度响应时域半解析解.将本文解分别退化为实心桩解和无相对滑移解,并与已有研究进行对比,验证了本文解的合理性.然后,采用参数分析法初步确定了Kelvin模型参数的合理取值区间.最后,分别分析了管桩桩长和土塞的渗透系数、孔隙率、剪切模量以及黏性阻尼系数对饱和土中非完全黏结管桩纵向振动特性的影响规律.研究结果表明,桩长越短,土塞与管桩之间的黏结程度对饱和土中非完全黏结管桩纵向振动特性的影响越明显;土塞的孔隙率和黏性阻尼系数对饱和土中非完全黏结管桩的纵向振动特性有明显影响,土塞的剪切模量和渗透系数对饱和土中非完全黏结管桩的纵向振动特性的影响较小,可以忽略不计.

Study on Vertical Vibration Characteristics of Incompletely Bonded Pipe Pile in Saturated Soil

Based on the Biot dynamic consolidation equation and the Kelvin model, the vertical vibration characteristics of the incompletely bonded pipe pile in saturated soil are investigated by considering the three dimensional effect of soil and the relative slip between the soil plug and pipe pile. Firstly, by introducing the potential functions and combining with the initial conditions and boundary conditions of the pile surrounding soil and soil plug, the vertical vibration solutions of the pile surrounding soil and soil plug are obtained by the Laplace transform method, Helmholtz decomposition method and separation variable method, respectively. Then, combining with the coupling conditions of pile-soil system, the complex stiffness, the frequency domain solution of the velocity and the semi-analytical solution of the velocity in the time domain of pipe pile top are obtained. Next, the degenerate solutions of this paper are compared with the corresponding existing solution to verify the rationality of the solution of this paper. Similarly, a parametric sensitivity analysis of the Kelvin model is conducted to preliminarily obtain the suitable values of the parameters of Kelvin model. Finally, the influence of the length of pipe pile, the permeability coefficient, porosity, shear modulus and viscous damping coefficient of soil plug on the vertical vibration characteristics of the incompletely bonded pipe pile in saturated soil are studied. The results show that, the shorter length of pipe pile leads to more obvious influence of the degree of bond between the soil plug and pipe pile on the vertical vibration characteristics of pipe pile in the saturated soil. The porosity and viscous damping coefficient of the soil plug have obvious influence on the vertical vibration characteristics of incompletely bonded pipe pile in saturated soil, and the influence of shear modulus and permeability coefficient of soil plug are too small to be neglected.