中国和美国的推移质泥沙采样器野外比测试验

Field Comparisons of Bed Load Samplers from USA and China

中国和美国已研制出多种推移质采样器 ,用以在变化范围很大的水流、泥沙条件下采样。由于采样器的设计原理不同和缺乏现场比测资料 ,这些采样器采样结果的可比性不明确。本文给出了五种采样器的输沙率及其它性能的现场比测结果。这五种采样器包括美国地质调查局设计的刚性框架的赫尔—斯密斯采样器 (以下称HS -1型 )和它的加大型 (以下称HS -1a型 )、沱特尔河TR -2型采样器以及中国长江水利委员会 (长江委 )研制的Y78-1型刚性框架采样器和Y80 -2型软底网式采样器。在美国各采样点比测HS -1型采样器的输沙率为Y78-1型的 3.0倍 ,而在中国比测的仅为 1 .2倍。两国比测点上流速和推移质粒度的明显差别可能是导致这一差异的原因 ,两国在采样技术和比测方法方面的差别也稍有影响。在中国的比测 ,HS -1a型测定的输沙率平均为Y80 -2型的 4.4倍 ,TR -2型测定的输沙率平均为Y80 -2型的 2 .2倍。比测过程中取得的经验有助于增加对推移质采样器设计特性的理解 ,并强调了使用不同设计的采样器来测定沙粒或较大的砾卵石泥沙的推移质输沙率是必要的。

A number of bed load samplers have been developed in the United States of America and the People's Republic of China to sample bed load transport under widely varying field conditions. Uncertainties about the comparability of results are due to differences in samples design philosophies and a lack of field experimentation comparing of sampling rates and other characteristics are presented for 5 samplers developed in the two countries. The samplers include the rigid-frame Helley-Smith-1, double-scale Helley-Smith-1a, and Toutle River-2 pressure-difference samplers, designed by the U.S. Geological Survey, and the rigidframe Changjiang-78 pressure-difference sampler and flexible-bottom Changjiang-80 basket sampler, Designed by the Changjiang Water resources Commission. Transport rates determined by the helley-Smith 1 averaged 3.0 times the Rates determined by the Changjiang-78 at sites in the Unites States, whereas that Ratio was only 1.2 at sites in China. Contrasts in flow velocities and particle sizes of bed load sediment sampled at sites in the two countries may contribute to the difference, while variations in field technique and design of sampling strategies within the two countries may contribute to the difference to a lesser degree. In China, transport rates sampled by the double-scale Helley-Smith-1a averaged 4.4 times those of the Changjiang-80. Rates sampled by the Toutle River-2 were 2.2 times those of the Changjiang 80. Experience gained during the comparisons contributes to increased understanding of bed load sampler design characteristics and emphasizes the need to use samplers of different design to define bed load transport of sand-sized and larger-sized and larger-sized sediment.