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为揭示三峡水库干流消落带的泥沙沉积规律、分析沉积泥沙来源,本研究采用原位观测方法采集沉积泥沙样品,利用激光粒度仪测试泥沙粒径,分析沉积泥沙粒径在水平、垂直和高程3个维度上的变化特征,并与三峡水库入库泥沙的粒径特征相结合,阐述消落带沉积泥沙来源。结果表明:(1)三峡水库干流消落带沉积泥沙粒径在水平方向上存在比较强烈的空间变化,中值粒径沿河流流向方向呈逐渐下降趋势,并在忠县及其下游河段基本保持稳定;(2)泥沙粒径随高程的变化存在较大的空间差异,河流挟沙是消落带下部粗颗粒泥沙的主要来源,而消落带上方的土壤侵蚀强度越高,消落带顶部的沉积颗粒就越容易变粗;(3)在水库尾端,泥沙剖面存在较明显的旋迴分层现象,其中值粒径数值较大、变化幅度较宽,越往下游推进,中值粒径的数值越低、变化幅度越小,泥沙旋迴分层现象逐渐消失;(4)水库尾端的沉积泥沙以库区外来沙为主,越往下游推进,库区内产沙对粗颗粒泥沙的贡献逐渐升高,但库区内外来沙都能够为沉积泥沙提供丰富的细颗粒物源,因此,细沙的来源具有一定的复杂性和多样化特征。
In order to reveal the law of sediment deposition in the hydro-fluctuation belt of the Three Gorges Reservoir and to analyze the source of sediment, sediment samples were collected by in situ observation. The particle size of sediment was measured by laser particle sizer. Horizontal, vertical and elevation characteristics of the three dimensions, and with the Three Gorges Reservoir sediment characteristics of particle size combined to explain the source of sediment sediment deposition. The results show that: (1) There is a strong spatial variation of sediment sediment size in the water level of the Three Gorges Reservoir. The median diameter decreases gradually along the direction of the river flow. In Zhongxian County and its downstream river (2) there is a big spatial difference in sediment particle size with height variation. Sediment flow is the main source of coarse sediment in the lower part of the fluctuation zone, while the soil erosion intensity above the water level is higher , The sedimentary particles on the top of the ebb zone are more likely to become thicker; (3) At the tail end of the reservoir, there is a more obvious cyclone stratification in the sediment profile. The median particle size value is larger and the variation range is wider. (4) The sediment sediment at the end of the reservoir is dominated by exotic sand in the reservoir area, and the more the sediment is pushed to the downstream, the lower the value of median diameter is, the smaller the change range is. The contribution of sediment production to coarse sediment in the area has been gradually increasing. However, both sediment and sediment in the reservoir area can provide a rich source of fine particles for sediment deposition. Therefore, the source of fine sand has certain complexity and diversification characteristics.