饱和黏弹性土层中桩扭转耦合振动研究

在频率域内研究了饱和黏弹性土层中端承桩的扭转耦合振动。饱和土的力学行为采用Biot模型来模拟。采用Novak平面应变模型,推导得到了饱和黏弹性土层的环向位移解析表达式。将桩等效为一维EulerBernoulli杆件处理。根据界面连续性条件,给出了端承桩扭转振动的分析方法和桩顶动力复刚度表达式。在此基础上,对比分析了扭转振动与纵向振动结果、三维模型和薄层法结果、边界单元法和薄层法结果、有无水惯性项的结果。考察了桩的长径比、桩土模量比、土骨架和孔隙水相互作用系数等参数对桩顶刚度因子和等效阻尼的影响。结果表明：桩扭转振动与纵向振动的复刚度曲线在形状上基本一致,而在相位和振幅上有一定区别。

Study on Torsional Coupled Vibration of. a Pile in Saturated Viscoelastic Soil

The torsional coupled vibration of an end -bearing pile in saturated viscoelastic soil is investigated in frequency domain. The mechanical behavior of saturated soil is described by the Biot theory. By using the Novak＇s layer method, the analytical expression for ring displacement of the saturated viscoelastic soil is obtained. The pile is treated as a Euler-Bernoulli rod. By utilizing the continuity condi- tions, the analysis method for the torsional vibration of the end-bearing pile in the saturated viscoelastic soil was presented, and the analytical expression of the complex dynamic stiffness at the pile top was ob- tained. On the basis, the comparative analysis between the results of torsional and vertical vibration, three-dimensional model and Novak＇ s layer method, boundary element method and Novak＇ s layer meth- od, with or without the inertial effects of water is carried out. The influences of the length-diameter ratio, modulus ratio of pile and soil, interaction coefficient of the soil skeleton and pore water on the dynamic stiffness factor and equivalent damping of the pile top are analyzed. It is shown that complex stiffness curve is basically the same shape for the torsional and vertical vibration of the pile, while it has greater difference in the phase and amplitude.