细颗粒泥沙的絮凝沉降特性

Flocculation and Settling Properties of Fine Sediment

电解质对细颗粒泥沙的絮凝或分散有重要作用 ,而细颗粒泥沙的絮凝沉降特性对土壤表层沉积性结皮的入渗性能有重要影响。在NaCl浓度为 0～ 10mmol/L ,泥沙初始浓度为 5、10、2 0 g/L时 ,本文利用吸管法研究了NaCl对细颗粒泥沙静水絮凝沉降特性的影响。结果表明 :泥沙沉降可分为两个阶段 ,分选沉降段和絮凝沉降段 ;在液面下同一深度 ,泥沙相对浓度随时间呈指数衰减 ;细颗粒泥沙絮凝的临界粒径为 0 .0 2 7mm ;泥沙平均沉速 ω随NaCl浓度以及泥沙初始浓度的增大而增大。在研究浑水入渗时 。

Fine sediment flocculation and dispersion that are dependent on electrolyte concentration, and Flocculation and settling properties of fine sediment have an important effect on water infiltration of the depositional crust. In this paper, sediment suspensions with original concentrations of 5, 10, 20g/L respectively, are prepared in NaCl solutions with concentrations ranging from 0 to 10mmol/L. The relative sediment concentrations are measured with a 20-ml pipette. The results show that there are two stages during sediment settling in still water, i.e., settling by gravity and settling by flocculation. Relative sediment concentrations decrease exponentially with time at the same depth below the suspension surface. Critical particle size for flocculation is 0.027mm, and the mean velocity of sediment increases with the increase of both NaCl and original sediment concentration. The role of electrolyte in the irrigation water should be taken into account when we study the muddy water infiltration.