工程堆积体坡面侵蚀泥沙分选特性与运移机制研究

Sediment Sorting Characteristics and Transport Mechanism of Slope Erosion of Engineering Deposit

为揭示工程堆积体陡坡坡面在径流驱动下侵蚀泥沙颗粒分选特征及搬运机制,设计了3种上方来水流量(10,20,30 L/min)下的野外模拟径流冲刷试验,对杨凌弃土工程堆积体陡坡坡面(32°)侵蚀泥沙的颗粒分布特征进行分析。结果表明:侵蚀泥沙(分散前)中黏粒、细粉粒较原始土壤明显增加,易产生侵蚀;径流对团粒破碎作用影响侵蚀泥沙黏粒含量,当径流功率<1.71 N/(m·s)时,黏粒含量与径流功率呈负相关,>3.89 N/(m·s)时则呈正相关;侵蚀泥沙中细粉粒、粗粉粒主要以单粒的形式搬运,而黏粒以及砂粒多以团粒的形式搬运;侵蚀泥沙中黏粒表现为富集,砂粒表现为贫化;泥沙颗粒粒径决定其主要搬运形式,<0.11 mm的泥沙颗粒以悬移/跃移搬运为主,>0.11 mm的泥沙颗粒以滚动搬运为主;滚动搬运的贡献率随径流搬运能力的增强呈先增大后减小。研究结果将有助于揭示工程堆积体坡面水蚀过程机理,为提高工程堆积体陡坡坡面水蚀模型预测精度提供科学依据。

In order to reveal the sorting characteristics and transportation mechanism of erosion sediment driven by runoff on the steep slope of engineering deposit,the field simulated runoff scouring test under three upper inflows of 10,20,and 30 L/min were designed,and the particle distribution characteristics of erosion sediment on the steep slope(32°)of the engineering deposit body in Yangling were analyzed.The results showed that the clay and fine silt in the eroded sediment(before dispersion)increased significantly compared with the original soil,which was easy to produce erosion.The fuction of runoff on the fragmentation of aggregates affected the clay content of eroded sediment.The clay content was negatively correlated with the runoff power when the runoff power was less than 1.71 N/(m·s),but it was positively correlated when runoff power was greater than 3.89 N/(m·s).In sediment,fine and coarse silt particles were mainly transported in the form of single grain,while clay and sand particles were mostly transported in the form of aggregates.In eroded sediment,clay particles were enriched and sand particles were depleted.The particle size of sediment determined its main transportation mode,sediment particles less than 0.11 mm were mainly suspension/saltation transport,and sediment particles more than 0.11 mm were mainly rolling transport.The contribution rate of rolling transport increased first and then decreased with the increasing of runoff transport capacity.The conclusion of this study was conductive to reveal the mechanism of slope water erosion process of engineering deposit body,and could provide scientific basis for improving the prediction accuracy of slope water erosion model on the steep slope of engineering accumulation.