移动降雨条件下结皮对坡面产沙的影响机理

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。

Impact of moving rainfall on soil erosion based on crust characteristics

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 important to influence the soil erosion process under moving rainfall conditions.