渭河临潼河段河床物质层理淤积结构分析

在分析渭河临潼河段渭淤20—27断面河床组成特点的基础上,对典型断面河床物质的层理结构特征、层理淤积结构的成因进行了分析。结果表明:①1960—2009年河段累计淤积泥沙0.728 7亿m3,其中汛期淤积0.838 7亿m3,非汛期冲刷0.110 0亿m3,河槽淤积0.214 0亿m3,滩地淤积0.514 7亿m3;②河槽部分多年平均河床质中值粒径为0.098 1～1.252 8 mm,滩地部分为0.036 8～0.079 7 mm;③渭河高漫滩从上至下呈上粗下细的二元结构特征,按沉积相可分为漫滩相沉积物与主槽沉积物,渭淤24—26断面河床物质主要为粉土、粉质黏土、沙砾石、圆砾,粉质黏土层中0.010 mm以下的细颗粒含量为20.0%～42.5%;④临潼、咸阳、张家山三站悬移质年均中值粒径均呈细化趋势,悬移质0.025、0.010 mm以下沙重百分数明显增大;⑤临潼河段河床物质层理结构是来沙级配差异并产生淤积而形成的,形成粉质黏土层的泥沙可能来源于渭河咸阳或泾河张家山以上的不同区域。

Analysis on Riverbed Material Bedding Siltation Structure in Lintong Reach of Weihe River

By analyzing the riverbed composition characteristics of 20-27 siltation sections in Lintong reach of the Weihe River,bedding structure characteristics of riverbed material were studied and the causes of the bedding siltation structure were revealed in this paper.The results indicate that a) the accumulated siltation volume in Lintong reach is 72.87 millions m3,in which the siltation volume in flood season is 83.87 millions m3,one in non flood season is 11.00 millions m3 during 1960—2009,the according siltation in river channel is 21.40 millions m3 and 51.47 millions m3 in flood-plain;b) the average annual median particle diameter of bed material in river channel is 0.098 1-1.252 8 mm and 0.036 8-0.079 7 mm in flood-plain;c) the Weihe River’s high floodplains have a dual structure characteristic,on thin under thick from up to down.According to sedimentary facies,we may divide the bed material into tidal flat deposit and the main channel deposit.The bed materials on 24-26 cross sections of the Weihe River are mainly composed of the silty,silty clay,sandy gravel and round gravel.In the above silty clay,fine particle below 0.010 mm make up 20.0% to 42.5%;d) the annual average medium particle diameter of the suspended load shows a refining tendency at Lintong,Xianyang and Zhangjiashan stations.But the percentages of suspended load below 0.025 mm and one below 0.010 mm increase obviously;e) the riverbed material structure at the Lintong reach is caused by very poor sediment-grading sand from the upper reach.The river bed material structure is mainly formed by sediment accumulation.By the further analysis,we know the sediment in silty clay layer perhaps originates from different areas upperward Zhangjiashan section at the Jinghe River or Xianyang section at the Weihe River.