黄河上游十大孔兑冲积扇泥沙运动和沉积环境研究

Sediment transport mechanism and deposition environment in alluvial fans of ten tributaries in the upper Yellow River

泥沙的颗粒大小影响着泥沙的输移和淤积过程,而沉积物粒径组成反映了沉积环境的水动力条件。通过从十大孔兑下游冲积扇9个钻孔和1个沉积物剖面采集沉积物样品并进行粒级组成分析,采用矩法公式计算粒径参数,结合粒度参数散点图及C-M图解,分析搬运动力和沉积环境。研究结果表明:钻孔中所采集的样品主要沉积于河流环境。平均粒径主要分布在4.32Φ以下;分选主要在较差和差之间;偏度值均大于0;大部分样点的峰度值均大于4.5,样品粒度分布集中。除了哈什拉孔兑以外,十大孔兑下游淤积的泥沙搬运方式主要以滚动为主,滚动组分和悬浮组分相混合,孔兑之间的泥沙搬运方式不存在明显的空间差异。

Sediment particle size affects the sediment transport and deposition processes,and reflects the deposition dynamics conditions. Sediment samples were collected from nine drilling cores and a deposits section on the alluvial fans in the lower reaches of ten tributaries in the upper Yellow River,and grain size composition of the samples were analyzed. Grain size parameters were calculated by the moment formulas,and the transport dynamics were analyzed by Mz-SD,SD-SK and SK-Kg scatter plots,and C-M diagram. Results show that nearly all the samples are fluvial deposits and the most of them have a mean grain size below 4. 32 Φ. The sorting is poor or very poor. The skewness values of all samples are larger than zero. The kurtosis values of most of samples are greater than 4. 5,with a very narrow peak of size distribution. Sediment transport is mainly in rolling and partly in suspension modes except the tributary Hashila. There are no obvious spatial differences of transport and deposition kinetics among the ten tributaries.