Study on Retardation and Sudden Stoppage Laws of Single-Particle Sediments with Different Forms of Motion in Hydraulic Jump Region

The mountain torrents triggered by heavy rainfall usually flow into rivers by carrying a large quantity of sediment particles. Under the retardation of local hydraulic jump, which is common in natural river course, the upstream sediments will silt up in the hydraulic jump region, thus blocking the river course, leading to the rise of riverbed water level and causing more serious mountain torrent disasters. In this study, the influences of different forms of motion of single-particle sediments in hydraulic jump region on the retardation and sudden stoppage characteristics in this region were explored through flume experiment. The experimental results revealed that single-particle sediments presented three forms of motion-translation, rolling and saltation-during the retardation and sudden stoppage process in the hydraulic jump region. The forms of motion had a bearing on the speed and acceleration changes, peak acceleration and silting position of single-particle sediments. When the single-particle sediments did translational motion, their speed dropped more quickly, the peak acceleration was greater and they silted up at a nearer position. Under the saltation motion, their speed declined more slowly, the peak acceleration was smaller, and they silted up at a farther position. The situation was between the two when the single-particle sediments made rolling motion.