镫口扬水灌区总干渠悬移质泥沙特性研究

Study of Suspend Load Characteristics in the Main Channel of Dekou Pumping Irrigation District

对总干渠各断面不同灌水周期和流量下悬移质泥沙进行采样,分析了总干渠悬移质泥沙量沿程变化及颗粒级配,计算了不同粒径泥沙的沉速和起动流速。结果表明,总干渠的悬移质泥沙80%以上为粒径小于0.062mm的冲泻质,除第一灌水周期初始开泵外,悬移质泥沙量沿程基本保持不变,且在大流量下略有增加,含沙量大小与流量相关,悬移质泥沙计算起动流速小于实测流速。因此,悬移质泥沙在正常灌水情况下会被水流输移到下游,在总干渠不发生沉积;而防治大颗粒的推移质泥沙在渠道淤积才是解决总干渠泥沙问题的关键所在。

The suspend load samples at different main channel sections were collected under different time and discharge, and the sediment concentration along the channel and grain size distribution were analyzed, the fall velocity and incipient and measure velocity for different grain sizes were calculated. The results showed that over 80% of the suspend load was wash load, which grain size was less than 0. 062 mm, the sediment concentration was related to discharge and did not change too much along the channel, and even turned higher at large discharge, the incipient velocity was lower than the measure velocity at different sampling time except for the first irrigation frequency. So suspend load would transport to the downstream by the flow and did not deposit on bed. The deposition of bed load was the main reason of channel siltingup, and the key to solve main channel deposition problem was the prevention and treatment of bed load.