模拟降雨下覆沙坡面侵蚀颗粒特征研究

Particle Size Composition of Sediment from Sand-covered Slope under Simulated Rainfall

风水交错侵蚀是风蚀水蚀交错区土壤侵蚀的主要形式,研究风水交错侵蚀对土壤颗粒的影响对于进一步研究风水交错侵蚀耦合机制及其对环境的影响有重要意义。采用人工模拟降雨试验,研究不同雨强和覆沙厚度及长度)条件下覆沙坡面侵蚀泥沙颗粒的变化特征。结果表明:不同降雨条件下侵蚀泥沙颗粒中粉粒和砂粒的含量较高,分别达到了48.86%、42.77%;坡面覆沙后,侵蚀泥沙中以粗颗粒居多,以黄土作为供试土壤,表层覆盖沙物质以后,仅有黏粒的富集率大于1;侵蚀泥沙的分形维数随着覆沙厚度和长度的增大而减小,d50则随着覆沙厚度和长度的增大而增大;覆沙厚度和长度对分形维数和d50的影响大于雨强。

Wind-water alternate erosion was the main form of soil erosion in the regions subjected to wind and water alternate erosion. The knowledge of effects of wind-water alternate erosion on soil particle size composition is very important to further in-depth research on coupling mechanism of the wind-water alternate erosions and its impact on the environment. In this paper,a simulated rainfall experiment was carried out in the State Key Laboratory of Eco-Hydraulic Engineering at the Xi’an University of Technology in China from July to August 2013,and particle size composition of the sediments down the sand-covered slope,as affected by rainfall intensity and thickness and length of the sand cover,was analyzed from September to October 2013,in order to further illustrate sediment yielding process of the erosion on sand-covered slopes. The study on variation of the particle size composition of the sediments down the sand-covered slope,as affected by rainfall intensity and thickness and length of the sand cover,was done with the aid of the statistic indices of the Malvern 2000 calculation samples,including the median particle diameter d50,maximum particle diameter and mean,particle diameter. Enrichment rate and fractal dimension were worked out,and SPSS18.0 was used to analyze relationships of the characteristics of their particle size composition with d50,fractal dimension and enrichment rate. Results show that after the slope was covered with sand,clay and silt decreased by 0~18% and 11%~29% in content,and by 0.7%~17% and 11%~29%,in enrichment rate,respectively,while sand increased by 17%~48% in content and by 17%~51% in enrichment rate. The erosion sediment was dominated with coarse particles.,In the two test soils（loess and sand）,only the clay enrichment rate was higher than 1 and with the sand cover increasing in thickness（length）,fractal dimension of the erosion sediment decreased,but d50 increased;on the sand-covered slope,the initial 0~10 minutes of runoff flow contained a large volume of silt and sand;and thickness（length）of the sand cover on the slope was higher than rainfall intensity in effect on fractal dimension and d50.