Laboratory analysis of incipient motion velocity for non-uniform non-cohesive sediments movement in rectangular flumes

The moment when sediment particles start to move is known as incipient motion of sediments. Many studies have been conducted to determine the incipient motion velocity of uniform non-cohesive sediments across open channels with a positive slope, and some equations and diagrams have been proposed in this regard; however, studies carried out on the non-uniform non-cohesive sediments, especially with the reverse slope, are very few. In this study, a lab flume and the dimensional analysis were used to analyze the inception motion condition of non-uniform non-cohesive sediments. In this study, a number of nine samples of non-uniform non-cohesive sediments with different sizes and uniformity coefficients were analyzed through three positive slopes 0.0005, 0.001, and 0.002 and also through three reverse slopes 0.0005, 0.001, and 0.002. The results indicated that particle stability is decreased with increasing the positive slope, whereas it is increased with increasing the reverse slope. The results also showed that particle's stability is decreased with increasing the particle size, whereas it is increased with increasing the uniformity coefficient of sediments.