成层饱和土中考虑横向惯性的单桩纵向振动

基于饱和多孔介质理论，研究了成层饱和黏弹性土层中端承桩的纵向振动特性。首先利用Novak薄层法，得到了土层对纵向振动桩的动力阻抗。其次，将桩等效为Rayleigh-Love杆，给出了成层饱和黏弹性土中端承桩纵向振动的一般分析方法和桩头动力复刚度的解析表达式。具体分析了两层饱和黏弹性土中端承桩的纵向振动特性，得到了桩头动刚度因子和等效阻尼随频率的响应特征，讨论了物理和几何等参数对动刚度因子和等效阻尼的影响。结果表明：桩长径比、土层模量比以及桩土模量比等对桩头动刚度因子和等效阻尼有显著的影响。相比于均质土层中的桩，上层土越硬或下层为软弱土层，桩的动刚度因子和等效阻尼振动幅值增大，其周期随长径比显著变化，且对于大直径桩，动刚度因子和等效阻尼随频率呈振动变化。同时，土体与孔隙水相互作用系数和桩泊松比等的影响相对较小。其结果可作为桩基动力基础设计和动力检测等基础数据。

Vertical vibration of single pile with transversal inertia effect in stratified saturated soil

Based on the theory of saturated porous media, the dynamic characteristics of vertical vibration of an end-bearing pile in a stratified saturated viscoelastic soil layer was investigated. The dynamic impedance of the soil to vertical vibration of the pile was obtained firstly with the Novak’s layer method. Then, regarding the pile as a Rayleigh-Love rod, the general analysis method for the vertical vibration of the end-bearing pile in the stratified saturated viscoelastic soil was presented; and the analytical expression of the complex dynamic stiffness at the pile top was obtained. The dynamic characteristics of vertical vibration of an end-bearing pile in a two-layer saturated viscoelastic soil were analyzed specifically; and the variations of the dynamic stiffness factor and equivalent damping of the pile top with respect to the frequency were given in figures. The influences of the physical and geometry parameters on the dynamic stiffness factor and equivalent damping were examined in detail. It is revealed that the length-radius ratio of the pile, the modulus ratio of the soil layers and the modulus ratio of the pile-soil have remarkable influences on the dynamic stiffness factor and equivalent damping of the pile top. Compared with pile in a uniform soil layer, the amplitudes of the dynamic stiffness factor and equivalent damping of the pile are increased as the elastic modulus of the upper soil layer is increased or the elastic modulus of the lower soil layer is decreased; and changes of the dynamic stiffness factor and equivalent damping with frequency are in form of the oscillation for large radius pile. Furthermore, the influences of the interaction coefficient between soil and pore water and the pile’s Poisson ratio are trivial relatively. The results can provide data base of pile design for dynamic foundation and dynamic detection of pile.