非饱和土中弹性支承桩的扭转振动响应分析

基于已建立的非饱和土中的波动方程,对均质非饱和滞回阻尼土层中的弹性支承桩扭转振动特性进行了分析.首先利用拉普拉斯变换,在拉氏交换域中求得了土体振动位移形式解,依据桩土接触面处的衔接条件将该解耦合进桩身动力平衡方程,求解桩的动力平衡方程,得到了桩顶速度导纳的频域响应解析解和半正弦脉冲激励作用下桩顶时域响应的半解析解,并分析了主要参数对振动特性的影响.结果表明,桩底支承刚度因子影响较大,土滞回材料阻尼有一定的影响,而土底支承剐度因子基本没有影响.

Torsional vibration of a pile with elastic bottom boundaries embedded in unsaturated soil

Based on the wave equation in unsaturated soil,the dynamic torsional response of a pile was investigated theoretically.The pile was assumed to be vertical,elastic,circular in cross section and with elastic bottom boundaries and the soil was modeled by a linear viscoelastic medium with frequency independent material damping of the hysteretic type.By using Laplace transformation,the vibration displacement solution with undecided constants was derived first.With the boundary condition at the interface between the pile and the soil,this solution was coupled into the dynamic equilibrium equation of the pile.Then by solving the equilibrium equation of the pile,the velocity admittance at the pile top was obtained in a closed form and a semi-analytical solution for the velocity response of the pile subjected to a semi-sine wave exciting force was derived.The influences of major parameters on the response were analyzed.It was shown that the influence of stiffness factor of supported soil underlying the pile base was remarkable and the influences of material damping of soil were minor and stiffness factor of supported soil at the bottom of soil layer had no influence on the response.