Experimental study on the suspended sediment settlement characteristics and incipient velocity in the straight-line sedimentation basin of the irrigation headworks

To explore the movement characteristics of sediment-laden flow and the basic settlement characteristics of suspended sediment in the sedimentation basins. The prototype observation of the straight-line sedimentation basin for irrigation headworks on the northern slope irrigation area of Tianshan Mountain was carried out, and analyzed the velocity, sediment content, and particle size in different sections. The results showed that the setting of sediment-blocking weirs was the primary factor affecting the settlement of suspended sediment, flow rate was the secondary factor. The overall trend of the suspended sediment content changed along the path was an oscillating trend. Sediment-blocking weirs had a significant effect on the sand particles, followed by silt particles, and clay particles were almost unaffected. The empirical formula of grouped silt deposition rate of sedimentation basin suitable for the northern slope irrigation area of Tianshan Mountain was obtained by using dimensional analysis method. A comparison of different incipient velocity formulas for fine particles revealed that when particle size remains consistent, higher suspended sediment content further reduces incipient velocity, which affected the size of the cohesive force between the fine particles. The findings from this study provide novel insights into the suspended sediment settlement characteristics in sedimentation basins.