中文摘要：

根据Biot饱和多孔连续介质波动方程,基于Bardet对准饱和土的假设,提出了准饱和土二相介质波动方程;运用Helmholtz矢量分解和传递、透射矩阵法（TRM）推导出准饱和土中层状半空间受竖向荷载作用下的动力响应表达式;利用Muki虚拟桩法,在层状半空间建立了桩和准饱和土相互作用的第二类Fredholm积分方程,通过离散的数值积分方法求解积分方程,讨论了准饱和土中单桩竖向动力响应问题。算例分析表明,准饱和土中桩顶竖向阻抗随饱和度的减少而增大,与饱和土地基相比,明显偏大;桩侧孔压随饱和度的减小而增大,并沿着桩长迅速衰减;桩顶位移幅值在频率较小时变化明显,饱和度越小,位移峰值越大,当频率较大时,饱和度的变化对振幅的影响不大。

英文摘要：

A 2-phase medium wave equation of nearly saturated soil is proposed based on Biot＇s wave equation of saturated porous continuous media and Bardet＇s assumption regarding nearly saturated soil. Applying the Helmholtz＇s vector decomposition and transmission and TRM,the dynamic response expressions of layered half-space in nearly saturated soil under vertical load are derived. Based on Muki fictitious pile methodology,the second kind of Fredholm integral equations describing interaction between pile and nearly saturated soil in half-space are established. The integral equations are solved by using discrete numerical integral method,and the vertical dynamic response of a pile embedded in nearly saturated soil is discussed. The numerical result shows that（ 1） the vertical impedance at the top of the pile embedded in nearly saturated soil increases as the saturation degree decreases,and it is quite large compared with that of the saturated soil foundation;（ 2） the pore pressure along the side of the pile increases as the saturation degree decreasing,and attenuates rapidly along the length of the pile;（ 3） the pile top＇s displacement changes significantly when the frequency is small,a smaller saturation degree results in a larger peak displacement,but when the frequency is great,the changing of saturation degree does not have a major effect on the amplitude.