悬浮桩侧向振动的非线性动力刚度

Nonlinear Dynamic Stiffness for Lateral Vibration of Floating Pile

该文研究了非线性粘弹性土层中粘弹性悬浮桩侧向振动的动力刚度.通过将悬浮桩端底下部的土介质等效为一虚拟桩——"土桩",将土介质等效为桩附近的非线性粘弹性内层土域和远离桩的线性粘弹性外层土域,利用等效线性化和分离变量法,求得了桩、土桩构成的组合桩在频率域内动力响应的半解析解,得到了悬浮桩桩头动力刚度.在此基础上,数值研究了各种物理和几何参数下悬浮桩刚度随激振频率的响应以及对这些参数的依赖性,结果表明:悬浮桩侧向振动的振幅、土层非线性效应、桩长等参数显著影响着悬浮桩的桩头刚度.一般情况下,土层的非线性效应将明显降低桩刚度,且仅通过增加桩长度并不能显著提高其刚度,而是存在一个最佳桩长,这些结果为工程设计提供了一定的参考.

Dynamic stiffness for lateral vibration of a viscoelastic floating pile in a nonlinear viscoelastic soil layer is investigated. We make the soil portion below the floating pile end equivalent to a virtual soilpile and divide the whole soil layer into a nonlinear viscoelastic inner zone and a linear viscoelastic outer zone. This way, a semi-analytical solution for dynamic behavior in the frequency domain of the composed pile is obtained using the equivalent linearization method and variable separation method. Expressions of dynamic stiffness on top of the floating pile are given. Dynamic stiffness of the pile are then analyzed numerically for different vibration frequencies. Effects of the physical and geometrical parameters are examined. It is revealed that the dynamic lateral stiffness of the floating pile depends heavily on the amplitude of the vibration, nonlinear soil property, pile length, etc. Generally, stiffnesses of the pile are signitlcantly decreased due to soil nonlinearity. Furthermore, the increment of stiffness cannot be achieved only by increasing length of the floating pile. There exists an optimization pile length. The results obtained are useful in pile design.