单相和饱和横观各向同性土中管桩扭转振动研究

发布时间：2018-05-25 07:12

本文选题：横观各向同性 + 单相土　；参考：《信阳师范学院》2017年硕士论文

【摘要】：基于考虑桩-土相互作用的连续介质模型,在频率域内研究了管桩在单相横观各向同性土、饱和横观各向同性土的扭转振动问题,并在考虑部分土塞效应的情况下,研究了单相横观各向同性土中部分外露管桩的扭转振动,最后通过改变主要几何参数、物理参数,分析它们对桩顶复刚度的影响。主要工作如下:首先,将桩周土体和桩芯土体都视为单相横观各向同性土,考虑桩-土耦合扭转振动,得到了土体的振动方程和桩作扭转振动的方程,结合边界条件和分离变量法,结合数学手段得到了土体作扭转振动的解,管桩扭转振动的解析解和桩顶复刚度的表达式。结合数值算例,改变主要的桩土参数,观察分析它们对桩顶扭转复刚度的影响。结果表明:桩周土各向异性参数对桩顶复动刚度影响显著,刚度和阻尼的震荡幅值随其增大而显著减小,桩芯土各向异性参数的影响规律与桩周土类似,但影响程度较桩周土小。其次,考虑部分土塞效应和土的横观各向同性,研究了部分外露管桩的扭转振动。忽略除桩周单相土层和桩芯单相土层径向位移的其他位移,最终求得了管桩桩顶的扭转复刚度。数值算例表明:桩周土各向异性参数对桩顶复动刚度影响显著,桩芯土各向异性参数的影响规律与桩周土类似,但影响程度较桩周土小;从整个频率范围来看,刚度和阻尼的震荡幅值随桩体剪切模量增大而增大。随着内外径的不断增大刚度和阻尼的震荡幅值增大,高频时刚度和阻尼的震荡幅值都较大。由此可知,管桩内壁不宜过薄,管桩桩芯埋入土体部分要保证一定的长度,特别是在高频范围内,才能保证实际工程的安全。最后,以Biot饱和土理论为基础,考虑桩周土和桩芯土的横观各向同性特性和轴对称性,在柱坐标下横观各向同性饱和土动力平衡方程和流体平衡方程的基础上,仅考虑桩周和桩芯横观各向同性饱和土径向位移,得到了管桩桩顶扭转复刚度的解析解。结合数值算例,通过改变主要的桩土参量,观察它们对横观各向同性饱和土中管桩扭转振动的影响。结果表明:饱和横观各向同性土中管桩的扭转振动同样存在有共振现象,桩周饱和土各向异性程度越大,桩顶复刚度越大;频率较大时,管桩越薄越容易发生失稳破坏;管桩长径比、内外半径比等几何因素和土的各向异性程度、剪切模量等因素对横观各向同性饱和土中管桩扭转振动的影响较大。
[Abstract]:Based on the continuum model considering pile-soil interaction, the torsional vibration of pipe pile in single-phase transversely isotropic soil and saturated transversely isotropic soil is studied in frequency domain. The torsional vibration of some exposed pipe piles in single-phase transversely isotropic soil is studied. Finally, by changing the main geometric parameters and physical parameters, the influence of them on the complex stiffness of the pile top is analyzed. The main work is as follows: firstly, the soil around the pile and the soil around the pile are considered as the single-phase transversely isotropic soil. Considering the pile-soil coupling torsional vibration, the vibration equation of the soil and the equation of the torsional vibration of the pile are obtained. Combined with boundary conditions and the method of separating variables, the solution of torsional vibration of soil, the analytical solution of torsional vibration of pipe pile and the expression of complex stiffness of pile top are obtained by mathematical means. Combined with numerical examples, the main parameters of pile and soil are changed, and their effects on the torsional stiffness of pile top are observed and analyzed. The results show that the anisotropic parameters of the soil around the pile have a significant effect on the composite stiffness of the pile top, and the oscillation amplitude of the stiffness and damping decreases with the increase of the anisotropy of the pile, and the influence law of the anisotropic parameters of the pile core soil is similar to that of the soil around the pile. But the influence degree is smaller than the soil around the pile. Secondly, considering partial soil plug effect and transversely isotropy of soil, the torsional vibration of partially exposed pipe pile is studied. Other displacements of radial displacement of the single phase soil layer around the pile and the single phase soil layer of the pile core are ignored and the torsional complex stiffness of the top of the pipe pile is finally obtained. Numerical examples show that the anisotropic parameters of soil around the pile have a significant effect on the composite stiffness of the pile top, and the influence law of the anisotropic parameters of the core soil is similar to that of the soil around the pile, but the influence degree is smaller than that of the soil around the pile. The vibration amplitude of stiffness and damping increases with the increase of shear modulus. With the increasing of internal and external diameters, the oscillation amplitude of stiffness and damping increases, and the oscillation amplitude of stiffness and damping increases at high frequency. It can be seen that the inner wall of pipe pile should not be too thin, and the safety of practical engineering should be ensured only when the core of pipe pile is embedded in soil, especially in the range of high frequency. Finally, on the basis of Biot saturated soil theory, considering the transversely isotropic properties and axisymmetric properties of surrounding soil and pile-core soil, the dynamic equilibrium equation and fluid equilibrium equation of transversely isotropic saturated soil in cylindrical coordinates are discussed. Considering only the radial displacement of the transversely isotropic saturated soil around the pile and the core, the analytical solution of the torsional complex stiffness of the top of the pipe pile is obtained. By changing the main pile-soil parameters, the effects of the parameters on the torsional vibration of pipe piles in transversely isotropic saturated soil are observed by numerical examples. The results show that there is resonance in the torsional vibration of pipe pile in saturated transversely isotropic soil. The larger the anisotropy of saturated soil around the pile is, the greater the complex stiffness of the pile top is, and the thinner the pipe pile is, the more vulnerable it is to the failure of the pile. Geometric factors such as ratio of length to diameter, ratio of internal and external radius, anisotropy of soil and shear modulus have great influence on torsional vibration of pipe pile in transversely isotropic saturated soil.
【学位授予单位】：信阳师范学院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU473.1

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