紫色土集流桶(池)搅拌取样测量含沙量误差试验

Experimental study on sediment measurement errors from sampling-mixing procedures of purple soil

为实现径流小区泥沙监测中集流桶(池)中含沙量的测量的准确计算,采用室内模拟试验,研究搅拌取样测量紫色土含沙量的误差及影响因素。含沙量水平均匀设计为:1、2、5、8、10、20、50、80、100、200、500、800和1 000kg/m^3共13个水平。泥沙水样总体积分别为50和100L,按照设计的含沙量水平制备泥沙水样,进行搅拌取样试验,将测量含沙量与设计含沙量进行对比,分析测量误差。试验结果表明,紫色土用搅拌取样法测得含沙量均小于实际值。当设计含沙量为1~200kg/m^3时,测量含沙量的相对误差在-30%^-50%;当设计含沙量为500、800和1 000kg/m^3时,测量含沙量的相对误差下降到-20%以下,但此时绝对误差最高达-110kg/m^3。泥沙含量和水体体积对含沙量测量结果均有影响。可以通过类似试验方法,建立不同工况下传统取样方法测量的含沙量与实际含沙量的关系,用于校正传统测量方法得到的含沙量。

Runoff plot is a commonly used method for soil and water conservation monitoring.Sampling after mixing from runoff collection bucket （tank） for sediment concentration measurement is a traditiona procedure.In this method,un-evenly sediment distribution in the procedure and quick deposition process of sediment particles may resultinaccurate measured sediment concentration.Laboratory experiments were conducted to investigate the error of sediment measurement and influential factors through mixing-sampling procedure.The experiments involved two sediment-laden water volumes of 50 and 100 L,using 13 sediment concentration levels of 1,2,5,8,10,20,50,80,100,200,500,800 and 1 000 kg/m^3.The sediment-laden water samples were prepared according to the designed sediment concentration.The measured and designed value of the sediment measurement error produced by mixing-sampling procedure was compared from.The experimental results indicated that sediment content measured was less than true value.The distributed value of relative error was mainly ranged from -30% to -50% for sediment concentration of 1-200 kg/m^3.The relative error was reduced to below -20% for sediment concentration of 500,800 and 1 000 kg/m^3,but the difference of sediment concentration reached 110 kg/m^3.And the research revealed that sediment concentration and volume impact on the results of relative sediment measurement.Through similar experimental methods,the research established the relationship between sediment concentration measurement obtained by traditional sampling methods and the actual sediment concentration under different conditions to correct the sediment concentration obtained by traditional measuring method.