عنوان مقاله [English]
نویسندگان [English]چکیده [English]
So far, many studies have been carried out to determine the conditions of incipient motion of sediment in open channels with positive slope and many relationships and graphs have been presented. But no any research has been done on incipient motion of the sediments on adverse slope of open channel and therefore, this study was conducted. In the experiments of this study, 9 types of non-cohesive and non-uniform sediments have been tested with different particle sizes and geometric standard deviation, on the bed adverse slopes of 0.0005, 0.001 and 0.002. According to the results, the stability parameter was directly related to the adverse slope of the channel. By increasing the adverse slope of the channel from 0.0005 to 0.002 for different particle sizes of sediments, the stability parameter was increased 52 percent on average. Also the particle size parameters showed inverse relation with the stability parameter. Thus, by increasing the particle size parameter from 0.12 to 0.35 for different adverse slopes, stability parameter was decreased 22 percent on average. According to the result, the stability parameter was directly related to the geometric standard deviation of the sediment particles. Consequently with increasing geometric standard deviation from 2.1 to 3.5 for different particle sizes of the sediment and channel slope, stability parameter was increased 7 percent on average.