非黏性沙级配对浊度法测量含沙量的影响

Influence of non-cohesive sand gradation on the measurement of sediment concentration with turbidity method

利用浊度仪测量水流含沙量时,泥沙颗粒级配和矿物成分是影响浊度仪标定结果的主要泥沙因素。采用黄河原型非黏性沙配制不同粒径、不同含沙量浑水水体,开展固定粒径、粗细沙、混合沙等多组次试验研究,对黄河天然沙粒径及级配对浊度仪输出浊度的影响进行定量分析和机制探讨。结果表明:固定含沙量条件下,非黏性泥沙粒径对水体浊度的影响特征符合Mie散射定律;含沙量变化对浊度仪输出浊度的影响数量级为10~10^(2),泥沙颗粒粒径变化对浊度仪输出浊度的影响数量级为10^(−1)~1;相同含沙量条件下,悬沙比表面积与浊度仪输出浊度符合线性分布。建立了考虑非黏性沙级配影响的含沙量与浊度关系模型,能够较准确地反映非黏性沙粒径及泥沙浓度对水体浊度的影响,可为浊度与含沙量关系的准确率定及测量结果的校准提供可靠依据。

It is the sand particle gradation and the sediment mineral composition which affect most the measurement of the suspended sediment concentration with the turbidity method.The field non-cohesive sediment of the Yellow River was used to prepare sandy water with different particle sizes and suspended sediment concentrations.Based on the group of experiments on fixed-size particles of sediment,coarse and fine particles of sediment,and mixed particles of sediment,the influence of the sediment gradation on the measured turbidity of Optical Back Scatteering(OBS)was quantitatively analyzed,and the influencing mechanism was preliminarily discussed.The results show that under the condition of fixed-size particles of sediment,the influence characteristic of non-cohesive sediment particle size on the water turbidity conforms to the Mie scattering law.The magnitude of the impact of the suspended sediment concentration on OBS output turbidity is in the order of 10-10^(2),while the impact of the sediment particle size is in the order of 10^(−1)-1.The relationship of the specific surface area of the suspended sediment and the measured turbidity of OBS accords with linear distribution in the same sediment concentration condition.A formula between the sediment concentration and the OBS output turbidity is established considering the influence of non-cohesive sediment gradation to accurately reflect the impact of non-cohesive sediment particle size differences and sediment concentration changes on water turbidity.This work can provide reliable evidence not only for the accuracy of the calculation of the sediment concentration and water turbidity,but also for the calibration of the measurement results.