澜沧江流域中下游悬移质泥沙粒度特征及分形研究

Grain size characteristics and fractal dimensions of suspended sediments in the middle and lower reaches of Lancang River

采集澜沧江中下游干支流28个悬移质泥沙样品,运用LISST-100X型激光粒度分析仪进行粒度分析,计算粒度参数及粒度分维值(D)并探究两者关系.结果表明:(1)悬沙以粉砂、砂粒为主,黏粒次之,分别约占48.92%、45.06%、6.02%;(2)梯级电站下,干流悬移质呈现坝上平均粒径高于坝下,分选变差的趋势;(3)分维值介于2.0017~2.5383之间,粒径小于x的范围累积频率与粒径为x的泥沙颗粒数目对数值拟合优度好,R^(2)大于0.92,泥沙粒度具分形性;(4)分维值与黏粒体积分数、平均粒径及分选系数呈极显著线性相关(p<0.01),复相关系数分别为0.8568、-0.7965、0.7513.研究结果揭示了澜沧江流域悬移质泥沙粒度及分形特征,为澜沧江水沙环境管理提供基础数据与科学支撑.

The LISST-100X was employed to analyze 28 suspended sediment samples from the middle and lower reaches of the Lancang River,and the study investigates the correlation between grain size characteristics and fractal dimensions of the sediments.The results show that:①The compositions of sediments rank from silt and sand,followed by clay,respectively accounting for 48.92%,45.06%and 6.02%.②The average particle sizes of suspended sediments decrease against the distance from their sources,meanwhile the average particle sizes of sediments in the reservoirs are bigger than those below the dams,but their sorting coefficients increase.③The fractal dimensions of suspended sediments range from 2.0017 to 2.5383.Meanwhile,the lg(W(r<x)and lg(x))are well fitted(R^(2)>0.92),so they have fractal features.④The fractal dimensions are linearly correlated(p<0.01)significantly with the volume percentages of clay,mean grain sizes,and sorting coefficients,with correlation coefficients being respectively 0.8568,−0.7962 and 0.7513.The results reveal the theoretical characteristics of suspended sediment grain sizes and fractals in Lancang River Basin,providing basic data for the management and control of water and sediment environment of the river.