大理盆地隐仙溪河道沉积物粒度分布特征

通过单人系统取样,用筛析法对云南大理盆地隐仙溪河道沉积物进行了粒度分析。结果表明,河流上游以砾石沉积为主,平均质量分数(含量)达57.92%以上,砾石粒径以10～50cm为主,在砂质沉积物中以粗砂为主,其含量达28 35%,中细砂含量只有13.76%;河流中游虽然也以砾石沉积为主,但砾石粒径明显变小,以5～10cm为主;河流下游则以砂质沉积物为主,其中中砂、细砂和粉砂总含量高达77.64%,尤其是细砂和粉砂含量显著升高,分别达到27.96%和32.26%,而粗砂和砾石含量明显降低。不同河段沉积物粒度及其含量的变化主要受水动力条件、地形坡度和搬运距离控制,但搬运距离与沉积物粒度之间不存在简单的线性对应关系。

Distribution features of grain size of Yinxian stream sediments in Dali Basin

By sampling systemically in the channel,the grain size characteristics of Yinxian stream deposition were studied in Dali Basin. The results show that there are gravels with the diameters of 10 to 50 centimeters in the upriver of the main sediments and the average content is more than 57.92%. The content of coarse sand is 28.35%. The content of middle sand and fine sand is 13.76%. Gravels are the main components of the sediments in the middle part with the diameters of 5 to 10 centimeters. In the downriver part, the components are sands mainly. The total content of middle sand, fine sand and silt is 77.64%, especially the content of the fine sand and silt increases distinctly, being 27.96% and 32.26% respectively. The grain size characteristics and the content of the sediments are controlled mainly by the hydrodynamic environment, topographic slope and transportation distance.