Experimental study on the fine sediment flocculation in the Three Gorges Reservoir

Field measurements were carried out at Zhongxian and Fengjie reaches in the Three Gorges Reservoir, and bed sediments were sampled to conduct laboratory experiments on flocculation and non-flocculation settling. The median particle diameters of suspended and bed sediments are all about 0.01 mm, and deposited sediments are fluid mud and floc-like structures, indicating the flocculation is likely to occur. When the flow velocities are small, the comparison between vertical sediment concentration distribution and Rouse equation indicates that the actual settling velocities are larger, and the measured settling velocities are as ten times as the Stokes settling velocities, illustrating that flocculation exists. The settling velocity is 0.033 mm/s in the non-flocculation experiments, while the flocculation structures are observed in the flocculation experiments, and the settling velocity is 0.3 mm/s, which is nine times of the non-flocculation settling velocity. The biggest floc size is deduced to be about 80 μm in the field based on the Stokes equation. © 2015, Editorial Board of Journal of Basic Science and Engineering. All right reserved.