In the present study, the effect of peak occurrence time and flood duration on the scour around the bridge pier installed in a sharply bended channel was investigated. For this purpose, several simple single-peaked hydrographs with the same durations and different peak occurrence times were produced in laboratory. In addition, hydrographs having two consecutive peaks with a steady flow discharge at the first peak and an unsteady-flow discharge at the second peak and vice versa were investigated. The flow velocity range began from incipient motion conditions and steeply increased to live bed conditions. In each experiment, the temporal variations of the maximum local scour depth were measured. In single-peaked experiments, by increasing hydrograph duration from 25 to 100 min, the maximum scour depth increased by 20%, and the progression of sediments along the downstream straight path increased by 150%. For hydrographs with two non-equal and the same duration peaks, at a constant discharge for the first peak and a decrease in the second peak discharge from 70 to 60, 50, and 45 (L s −1 ), the volume of the scour hole around the pier was decreasing 15, 40, and 60%. Its area fell by 10, 40, and 55%, respectively. When the rising and falling limb time of hydrographs were equal, the maximum sedimentation height increased by 2.7, 3.5, and 5 times, respectively by increasing test duration from 25 to 50, 75, and 100 min.

中文翻译：

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初始运动和活床条件下水位线持续时间和模式对急弯码头周围冲刷的影响

在本研究中，研究了高峰出现时间和洪水持续时间对安装在急弯通道中的桥墩周围冲刷的影响。为此，在实验室中制作了几个具有相同持续时间和不同峰值出现时间的简单单峰水位线。此外，研究了具有两个连续峰值的水文过程线，其中第一个峰值为稳定流量，第二个峰值为非稳定流量，反之亦然。流速范围从初始运动条件开始，并急剧增加到活动床条件。在每个实验中，测量了最大局部冲刷深度的时间变化。在单峰实验中，通过将水位过程线持续时间从 25 分钟增加到 100 分钟，最大冲刷深度增加了 20%，沿下游直线路径沉积物的进展增加了150％。对于具有两个不相等且持续时间相同的峰值的水文过程线，在第一个峰值的恒定流量和第二个峰值流量从 70 减少到 60、50 和 45 (L s -1 ) 时，冲刷的体积桥墩周围的洞减少了 15%、40% 和 60%。其面积分别下降了 10%、40% 和 55%。当水文过程线的上升和下降沿时间相等时，随着试验时间从25分钟增加到50分钟、75分钟和100分钟，最大沉降高度分别增加了2.7、3.5和5倍。码头周围冲刷孔的体积分别减少了 15%、40% 和 60%。其面积分别下降了 10%、40% 和 55%。当水文过程线的上升和下降沿时间相等时，随着试验时间从25分钟增加到50分钟、75分钟和100分钟，最大沉降高度分别增加了2.7、3.5和5倍。码头周围冲刷孔的体积分别减少了 15%、40% 和 60%。其面积分别下降了 10%、40% 和 55%。当水文过程线的上升和下降沿时间相等时，随着试验时间从25分钟增加到50分钟、75分钟和100分钟，最大沉降高度分别增加了2.7、3.5和5倍。