移动降雨条件下结皮对坡面产沙的影响机理

Impact of moving rainfall on soil erosion based on crust characteristics

通过室内小尺度坡面(4m×1m)人工降雨物理模型,设计沿坡面上下移动的移动降雨工况进行产沙产流过程比对试验,对产流产沙量时空特性及侵蚀泥沙粒径特性进行分析,探讨不同降雨移动方向条件下结皮对坡面产沙过程的影响机理。结果显示:结皮发育造成产沙显著减少;降雨向上移动时,结皮发育成熟使峰值产沙提前出现,而向下移动时产沙峰值始终随产流峰值一起出现;向上移动降雨工况在雨强3.6×10-5 m/s时达到产沙峰值和等效泥沙浓度的最大值,而向下移动工况则对应更大的降雨强度;结皮发育在降雨初期对产沙成分的影响最明显,总体上产沙成分保持特定比例结构,粉粒最易受侵蚀,粘粒次之。研究表明:结皮发育是影响移动降雨条件下坡面产沙时空特性的重要因素。

： The impact of the crust characteristics on soil erosion for moving rainfall conditions was investigated using comparative rainfall-runoff tests on small slopes （4 m× 1 m）. The spatiotemporal characteristics of the runoff, soil erosion, and grain size distribution show that crust development results in less soil erosion. The peak erosion occurred earlier than the discharge peak for upstream moving rainfall events when the crust was fully developed, while the two peaks happened simultaneously for downstream-moving rainfall events. The maximum erosion and sediment concentration peaks occurred with rainfall intensities of around 3.6 × 10^-5 m/s for upstream-moving events. The grading of the eroded sediment is most strongly affected by the crust at the beginning of the rainfall events with silt as 70% of the total eroded materials. This study indicates that crust development is very iraportant to influence the soil erosion process under moving rainfall conditions.