土壤学报2017，Vol.54Issue(1)：60-72,13.DOI:10.11766/trxb201604190106
沙层厚度和粒径组成对覆沙黄土坡面产流产沙的影响
Effects of Thickness and Particle Size Composition of Overlying Sand Layer on Runoff and Sediment Yield on Sand-covered Loess Slopes
摘要
Abstract
Objective]The region of loess slopes covered with sporadic aeolian sand is the most serious erosion-stricken area in the aeolian-water erosion interlaced zone of the Loess Plateau. This project is oriented to study characteristics of the soil erosion in this region in an attempt to provide some principal theory for prediction and control of soil erosion in the aeolian-water erosion interlaced zone. Observations in this special region found that aeolian sand-covered loess slopes were different in runoff production pattern and erosion process from ordinary loess slopes. So far,a little has been reported about studies on soil erosion on this special type of slopes. [Method]An indoor experiment with simulated rainfalls on soil erosion on sand-covered loess slopes was carried out. The experiment was designed to have only one rainfall intensity (90 mm h-1),one slope gradient(15°),three levels of thickness for overlying aeolian sand(2 cm, 5 cm and 10 cm)and five patterns of particle size composition(100%<0.25 mm,75%<0.25 mm + 25%>0.25 mm,50%<0.25 mm + 50%>0.25 mm,original aeolian sand and 100%>0.25 mm). [Result]Results show that overlying aeolian sand layers delayed the initiation of runoff and reduced the generation rate and volume of runoff,but increased the yielding rate and volume of sediment on loess slopes. The initiation of runoff on slopes covered with 2 cm,5 cm and 10 cm thick of aeolian sand was 6~10 times,12~20 times and 16~26 times later than that on the ordinary loess slope,respectively. Thickness of the aeolian sand layer is the main factor affecting delayed runoff and sediment yield. The thicker the overlying sand layer, the later the initiation of runoff,the lower the runoff rate and runoff volume and the higher the yielding rate and volume of sediment yield. During the rainfall process,runoff and sediment fluctuated sharply in rate and volume and the fluctuation intensified with the aeolian sand layer increasing in thickness. The effect of particle size composition of the sand layer on runoff and sediment yield varied with thickness of the sand layer. On slopes covered with a sand layer 2 cm in thickness,runoff and sediment yield tended to increase with the sand layer increasing in particle size during the initial period of rainfall,but no such a tendency was observed during the late period of rainfall. On slopes covered with a sand layer 5 cm in thickness,runoff increased in rate with the sand layer increasing particle size. The slopes covered with coarse sand was higher in erosion rate than the slopes covered with find sand during the initial period of rainfall,and it went reversely in the late period of rainfall. On slopes covered with a sand layer 10 cm in thickness,runoff and sediment yield did not vary much with particle size composition of the sand layer. There might be a reasonable range of aeolian sand thickness in which the influence of particle size composition of the sand layer on runoff and sediment yield existed. In short,thickness,particle size composition and their interaction significantly(p<0.05) influence the initiation of runoff,60 min runoff volume and 60-min sediment yield. [Conclusion] The runoff production process on aeolian sand-covered loess slopes goes as vertical infiltration of rainwater-flow at the interface between sand layer and loess layer-seepage at the toe of the sand layer-overland runoff, while the erosion process goes as seepage erosion at the toe of the sand layer-retrogressive collapse caused by gravity and flow-surface runoff transport,which are completely different from the pattern of runoff yield under excessive infiltration and the erosion development process of splash erosion-sheet erosion-rill erosion on bare loess slopes.关键词
覆沙黄土坡面/覆沙厚度/粒径组成/产流产沙Key words
Aeolian sand-covered loess slope/Aeolian sand thickness/Particle size composition/Runoff and sediment分类
农业科技引用本文复制引用
谢林妤,白玉洁,张风宝,杨明义,李占斌..沙层厚度和粒径组成对覆沙黄土坡面产流产沙的影响[J].土壤学报,2017,54(1):60-72,13.基金项目
国家自然科学基金项目（41371283，41571130082，41330858）资助 Supported by the National Natural Science Foundation of China （）
