三峡库区细颗粒泥沙絮凝的试验研究

Experimental Study on the Fine Sediment Flocculation in the Three Gorges Reservoir

在三峡库区的忠县和奉节河段实施现场测量,并对床沙取样开展絮凝和非絮沉降的室内试验.库区悬移质和床沙的中值粒径均为0.01mm,且淤积物为浮泥和类似絮凝结构,表明絮凝可能发生.含沙量垂线分布在小流速时比Rouse公式不均匀,说明实际的泥沙沉速较大,且实测的泥沙沉速约是Stokes沉速的10倍,证明库区存在絮凝.非絮凝沉降试验时泥沙沉速约为0.033mm/s,而絮凝沉降试验中观测到絮凝结构,沉速约为0.3mm/s,是非絮凝沉速的9倍左右.由Stokes公式推算三峡库区最大絮团粒径约为80μm.

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 nonflocculation experiments,while the flocculation structures are observed in the flocculation experiments,and the settling velocity is 0. 3mm/s,which is nine times of the non-flocculation settling velocity. The biggest floc size is deduced to be about 80μm in the field based on the Stokes equation.