湖南武水流域泥沙颗粒特性及分形规律研究

Particle Sizes and Their Fractal Characteristics of Sediments from Wushui Watershed of Hunan Province

流域土壤流失的泥沙颗粒及其分布与流域土壤有关,影响流域土地质量和输沙过程。以武水流域天然河道的53次降雨径流输沙过程实测资料为基础,运用R-R(Rosln-Rammler)粒径分布函数法分析了泥沙颗粒级配特性及其分形规律。结果表明,流域多年均悬移质泥沙颗粒组成为粘粒11%、粉粒51%、细砂粒32%和粗砂粒6%,以粉粒和细砂粒为主体,占83%。1981年以后,悬移质泥沙颗粒中粘粒和粉粒含量相对减少,悬移质泥沙颗粒呈变粗的趋势。悬移质泥沙颗粒组成具有分形特征,分形维数D与小于0.005 mm粉粒及粘粒含量呈较显著相关,与中值粒径相关性较差。流域推移质泥沙颗粒中值粒径平均为0.874 mm,推移质泥沙以砂、石砾为主。推移质泥沙颗粒组成具有分形特征,分形维数D与小于0.3 mm细砂及粉粒含量呈显著相关。流域泥沙级配及其变化,有利于分析泥沙来源,采取相应的治理措施,控制泥沙。

Sedimentation from a watershed and their size distribution are closely related to the soils in the watershed,and influences the land quality and sediment delivery.The particle size of and their fractal characteristics of sediments from Wushui watershed of Hunan province were analyzed with R-R（Rosln-Rammler） particle size distribution functions,based on the suspended and load sediment records of 53 events of rainfall-runoff-sediment processes.The results showed that the size distribution of yearly suspended sediments,as of clay,silt,fine and coarse sands were 11%,51%,32% and 6%,with silts and fine sand particles as the dominants.Since 1981,the contents of clay and silt particles in the suspended sediments have been decreased while the coarse grains increased.There existed notable fractal characteristics of the particle sizes in the suspended and load sediments.And the fractal dimension was regressively correlated with the contents of clay particles and the fine sand particles smaller than 0.005 mm,and not correlated with the average particle size.In the bed load sediments,the sands and gravels were the dominated components with the d50 of 0.847 mm.The fractal dimension was significantly correlated with the content of fine sand and silt particles smaller than 0.3 mm.The change in the particle size distribution from watershed is important to identify the sediments sources and to implement the conservation measures for sedimentation control.