Laboratory investigation of incipient motion of non-cohesive and non-uniform sediment in irrigation and drainage Channels

Generally, a moment that sediment particles start moving in stream is called incipient motion. A lot of research has been recently done to determine the conditions of incipient motion velocity of uniform and non-cohesive sediment in open channels and many Relationships or graphs are presented. But studies on non-cohesive and non uniform sediments are very little. With regard to the channel sediments are mostly non-uniform, Determination of the flow rate for prevent of sediment deposition can be an effective role in increasing of transmission efficiency and which reduced costs.
In this study, incipient motion of non-cohesive and non-uniform sediment was investigated by Laboratory modeling and dimensional analysis. In this study 9 non-cohesive and non-uniform sediment has been tested with different dimensions and uniformity coefficient in 0.0005, 0.001 and 0.002 slopes.
Results showed that increasing channel slopes from 0.0005 to 0.002 for sediments with different size, stability parameter on average decreases 45 percent. Also increasing particle size parameter from 0.12 to 0.35 for different slope, stability parameter on average decreases 15 percent. Results showed that with increasing uniformity coefficient from 4.5 to 7.5 for different size of sediment and channel slope, stability parameter on average increases 6 percent.
With increasing the slope and particle size parameters, decrease stability parameter and stability parameter, will increase with increasing uniformity coefficient.