西柳沟河床泥沙组成分析

Analysis of Riverbed Sediment Composition in Xiliugou River

为研究西柳沟泥沙来源及沿程输移情况,在西柳沟干流河床取样并进行了颗粒分析。结果表明:西柳沟河床组成沿程可分为3段,从上游向下游分别为丘陵区、沙漠区和平原区,相应中值粒径从大向小过渡,其中丘陵区粒径从大到小衰减迅速,经过沙漠区继续细化,到冲积平原区趋于稳定,中值粒径从上游的2 mm以上变化到下游的平均0.157 mm;从不同河段的粒径组成看,粒径大于0.5 mm的泥沙在丘陵区占70%以上,到平原区基本消失;沙漠区河床处于过渡带,粒径变化较大;平原区河床中0.1~0.25 mm的泥沙约占62%,0.1 mm以下的泥沙含量显著增大;洪水携带的泥沙沿程分选细化,大砾石主要落淤在上游丘陵区,部分经过沙漠区进一步调整,到下游平原区河床组成受沙漠沙影响较大。

In order to identify the sources of the sediment of Xiliugou River and research its transporting along the river, the sediments at theriver bed of the mainstream were sampled and the gradation of the grain size of the samples were tested and analyzed. The results show that the sediment gradation of riverbed along the river from upstream to downstream can be divided into three sections, hilly area, desert area and plain area, the median grain size of each section from upstream to downstream changes from coarse to fine. In hilly area the grain size decreases rapidly, then continues to decrease in the desert area and finally remain stable in the alluvial plain with an average median diameter of 2 mm in upstream to 0. 157 mm in downstream. Of the grain size gradation in hilly area, the parts with grain size greater than 0. 5 mm account for more than 70%, but disappear in the plain area. The riverbed in desert area is the transition zone, and the range of grain size is larger. In the plain area, the parts of sediment with grain size of 0. 1-0. 25 mm account for about 62%, and the proportion of sediment with grain size minor than 0. 1 mm increases significantly. Thus, the sediment carried by floods is sorted along the river, and the gravels are mainly deposited in the upper hilly area, and a small part of them further deposited in the desert area. The sediments deposited in the riverbed in the lower plain are mainly from the desert area.