基于赫兹接触理论的桥墩局部冲刷防护石块起动简化公式

Simplified Formula of Riprap Initiation for Bridge Pier Local Scour Protection Based on Hertz Contact Theory

为了在理论上研究桥墩局部冲刷防护石块的起动,通过简化三维马蹄形旋涡研究了墩前和墩侧的桥墩局部河床底部流速,采用赫兹接触理论分析石块的运动,提出了冲刷防护石块起动的简化实用公式,并与经验公式和实际工程进行比较。研究结果表明:墩侧河床底部流速远大于墩前;当行近流速小于4m·s-1时,可采用抛石防护,抛石直径不大于0.9m,质量在1t以下;当行近流速大于4m·s-1时,建议采用其他冲刷防护措施;提出的简化公式与经验公式和实际防护工程基本一致。

In order to study the riprap initiation for bridge pier local scour protection in theory, the horseshoe vortex was simplified to analyze the bottom velocities around the bridge, including velocities at the front and both sides of bridge pier. The Hertz contact theory was used to analyze the motion of riprap and a simplified formula of the riprap initiation for bridge pier local scour protection was proposed, which was compared with the empirical equation and practical projects. The results show that bottom velocities at the sides of bridge pier are larger than that at the front of bridge pier. When the approach velocity is smaller than 4 m ·s^-1 , the riprap protection can be used, with the rock diameter less than 0. 9 meter and rock quality less than 1 t. When the approach velocity is larger than 4 m · s^-1, other measures are recommended for local scour protection. The simplified formula is proved to be in accord with the empirical equation and practical projects.