Abstract: The flow-altering countermeasures can effectively curb the bed sediment erosion by changing the hydrodynamic conditions around the piers, which has a good protective effect and application value. However, there has not been systematic study on its scour protection effects and characteristics yet. Therefore, the classic flow-altering countermeasures such as the horizontal collar, bridge piers slot, footing caisson, sacrificial piles, embedded sill and embedded vanes were systematically studied by means of the indoor variable slope flume test. The influence rule of geometric layout parameters of the flow-altering countermeasures on the reduction efficiency of the equilibrium maximum scour depth was also studied. The protection effect and protection characteristics of these classical flow-altering countermeasures against the clear water scour were deeply analyzed from the mechanism. The research results can offer some references for the choice and optimal design of the flow-altering countermeasures.

Key words: clear water scour, flow-altering countermeasures, protection effect, protection characteristics

摘要： 减速不冲防护技术能够通过改变桥墩周围水流动力条件来有效遏制床面泥沙冲刷，具有较好的防护效果和工程应用价值，但目前还没有关于其冲刷防护效果及特性的系统研究。通过室内变坡水槽试验对水平护圈、墩体开缝、基础沉箱、墩前排桩、埋置式拦沙槛、埋置式导流屏等典型减速不冲防护技术进行了系统的研究。分析了各典型减速不冲防护技术几何布设参数对桥墩周围冲刷深度削减率的影响规律，并从机理上探究了减速不冲防护技术对桥墩清水局部冲刷的防护效果和防护特性。研究成果可为桥墩局部冲刷防护技术的选取及优化设计提供参考依据。

关键词: 清水冲刷, 减速不冲防护技术, 防护效果, 防护特性