三维轴对称条件下基于虚土桩法的单桩纵向振动分析

Longitudinal vibration of piles in 3D axisymmetric soil based on fictitious soil pile method

虚土桩法是一种处理桩底支撑的新方法,该方法将桩体正下方投影到基岩的土体简化为虚土桩,求解时将其看作桩体。以桩轴心线为Z轴,建立轴对称坐标体系,通过虚土桩与土体的边界条件,求解得到虚土桩桩顶的复刚度。将该复刚度作为实体桩桩底的支撑刚度,结合实体桩与土体的边界条件,利用复阻抗传递法得到单桩桩顶的复刚度和速度响应函数。通过数值计算,分析了桩底土体的虚土桩长度、剪切波速及泊松比等参数对单桩动力响应的影响;对比了虚土桩法与其他不同桩底支承的异同,进一步评价了虚土桩法的优越性和合理性;结果表明,虚土桩法可以模拟弹(黏)性支撑和固定支撑,是一种较为严格的计算模型,具有进一步研究的价值。

A new treatment way for the supporting soil under physical piles,the fictitious soil pile method,is introduced,in which the projection zone of the soil from immediately below the physical pile till the bedrock is simplified as a fictitious soil pile.A three-dimensional axisymmetric coordination is established with the axial line of pile as the Z axis.Firstly the complex stiffness of the fictitious pileblock is obtained by solving the vibration equation with its boundary condition.Further,regarding the complex stiffness of the fictitious pileblock as the supporting stiffness of physical pile,both complex stiffness and velocity response function of the physical pilebolck are obtained using the complex impedance transfer method based on the boundary condition of the physical pile.Effects of length,velocity of shear wave and Poisson ratio of the fictitious soil pile on dynamic responses of the physical pile are also investigated.Finally,compared to some other methods for the pile supporting,the advantages and rationality of the fictitious soil pile method are identified.It is indicated that the fictitious soil pile method is a more precise computational modeling for simulating elastic（viscous） and fixed supporting,and is worth further studing.