波流耦合下桩周珊瑚砂冲刷机理研究

Study on scour mechanism of coral sand around pile due to wave and current coupling action

针对我国南海某岛礁珊瑚砂地基上的圆形桩基础,采用N-S方程k-ε模型、双向耦合方式跟踪流场中颗粒运动轨迹的方法,对桩周珊瑚砂的冲刷规律进行了求解,分析了桩体周围流体的速度场以及桩体表面剪应力场的分布规律,同时对桩周珊瑚砂冲刷坑的形成过程进行了模拟。计算结果表明,在桩体周围形成的马蹄形漩涡和桩柱后方的尾涡作用下,桩周土体出现了较为明显的冲刷现象,涡旋的释放显著地影响着珊瑚砂地基上桩基的冲刷坑形状;而且,由于珊瑚砂颗粒密度较石英砂小,水动力作用下桩周冲刷坑更容易形成,所以实际工程中需要考虑有效的防护措施。

According to some circular pile foundation of coral sand foundation in the South China Sea Islands,a numerical method using the k-εmodel of N-S equations with two-way coupling tracking particles in the flow field,was used to study the scour law of coral sand around the circular pile,and the velocity distribution law of the fluid field around the pile and the tangential shear stress field of pile surface were analyzed,and the forming process of coral sand scour hole around pile was simulated simultaneously.The numerical results showed that the main hydraulic reasons for scour mechanism of coral sand were the horseshoe vortex near the pile and the lee-wake vortex behind the pile;as the density of coral sand was less than the river sand,the scour shoe around the pile on the coral sand foundation was easier to occur,therefore,some protective measures need to be considered in the actual project.