镫口扬水灌区输水干渠来沙特性解析

Analysis of the Factors Affecting Sedimentation in Canals Ditching Yellow River Water for Irrigation

内蒙古镫口扬水灌区是内蒙古自治区的大型灌区,近年来渠道泥沙淤积严重,严重影响灌区灌溉运行。【目的】探明水沙条件与渠道淤积之间的关系,保障灌区的正常运行,提高灌区灌溉水利用效率。【方法】在取水口,通过对灌水期前后测定水位来确定淤积厚度以及对泵站进水口泥沙野外监测及采样分析,并测定了流速及流量,室内分析了泥沙颗粒级配及特性等,综合分析确定了取水口来沙特性。【结果】由于停泵时间长、水流含沙量高,第1和第4灌水期前,泵站进水口前泥沙淤积厚度最厚;同时,由于泵站运行的抽吸作用,进入总干渠的泥沙量也最多,近80%以上为粒径小于50μm的细砂,只有约20%为泥沙粒径大于50μm的粗砂。泵站运行流量越大,停水时取水口淤积厚度越小,进入渠道的泥沙越多。在来水来沙条件不变的情况下,取水口淤积厚度受停泵时间影响,与停泵时长成正比;随着泵站的运行,在一定的含沙量下,存在一定的渠道不冲不淤临界流量。【结论】因此在缓减干渠淤积方面需要有特定的工程和管理措施。

Dengkou is an irrigation district pumping water from the Yellow River for irrigation. Its performance has deteriorated over the past few years due to sediment deposit. The purpose of this paper is to analyze the factors that affected the sedimentation.【Method】We calculated the depth of the sedimentation at the entry to the canal by measuring the water levels before and after irrigation, as well as the sediment content of the water at the entry to the pumping station. In the meantime, we also measured flow velocity and flow rate and analyzed the size and size-distribution of the sediments.【Result】The sediment at the entry to the pumping station was thickest prior to the first and the fourth irrigation because the pumps had been put at rest for a long period and the sediment content in the water was high. As such, more sediments were pumped into the canal, in which 80% had an average diameter less 50 μm. The amount of sediment pumped into the canal increased with the pumping rate.【Conclusion】Under the same conditions, prolonging the rest time of the pump increases the thickness of the sediments at the entry. At a given sediment content, there is a critical pumping rate at which there is no sedimentation. Therefore, improving engineering management can reduce sediment deposition in the canals.