桥墩基础局部冲刷抛石防护性能波流水槽试验研究

Flume Tests for Riprap Countermeasure to Bridge Piers from Local Scour

作为应用最为广泛的桥墩基础局部冲刷防护措施之一,抛石防护受到国内外学者越来越多的关注。通过波流水槽模型试验,研究了抛石粒径、抛石层厚度和抛投范围等主要设计参数对抛石防护效果的影响,并对比分析了中美两国规范关于抛石粒径的选取方法。试验结果表明,合理的抛石配置方式能有效地减小桥墩基础局部冲刷,使冲刷平衡时间延后;抛石层厚度为3~4倍抛石粒径、抛投范围为3倍桩径时,防护效果和经济性较佳;对于抛石粒径的选取,流速较大时,美国规范的计算结果偏大,而中国规范则偏小,流速较小时,建议可以采用工程经验方法确定。

As one of the most widely used protection measures to bridge piers from local scour, the riprap protection has attracted a sustained attention from domestic and foreign scholars. This paper performed on flume model tests about the influence of riprap size, thickness, and lateral extent on effect of riprap protection, and the comparisons and discussions of selection of riprap size in current design codes of China and America were also made. The test results showed that reasonable allocation of riprap can diminish the local scour effectively, and delay the time to reach equilibrium scour state. When the riprap thickness is 3 to 4 times of the length of riprap size and the lateral extent is 3 times of the diameter of bridge piers, the riprap can mostly protect the bridge from local scour and minimize the cost as much as possible. As for the selection of the riprap size, when the velocity is high, the design codes of America suggest a larger size while the design codes of China recommend a smaller one. When the velocity is low, experienced method is recommended.