不同土质工程堆积体径流产沙差异

依据野外调查结果概化堆积体下垫面,采用室内人工模拟降雨方法,研究不同雨强(1.0、1.5、2.0、2.5 mm/min)条件下4种砾石质量分数(0、10%、20%、30%)的壤土、黏土及砂土工程堆积体径流产沙特征差异。结果表明:1)砂土堆积体坡面产流开始所需时间较壤土及黏土堆积体长。3种土壤质地工程堆积体含砾石的平均流速较纯土体(砾石质量分数为0)小,大小表现为黏土壤土砂土。砂土堆积体平均径流率较壤土和黏土分别减少20.7%和18.8%;2)砂土堆积体平均侵蚀速率分别是壤土和黏土的3.0和2.3倍。3种土壤质地工程堆积体的平均侵蚀速率随雨强增大递增,但随砾石质量分数递增呈显著线性递减(P0.05);3)砂土堆积体平均侵蚀量分别是壤土和黏土的4.5和3.4倍。3种土壤质地工程堆积体的侵蚀量与径流量和雨强均显著相关。研究成果可为建立生产建设项目工程堆积体水土流失量测算模型提供数据基础和理论依据。

Differences in characteristics of runoff and sediment yielding from engineering accumulations with different soil textures

Abstract: It is a hot and difficult issue to study soil and water loss caused by current engineering accumulations in production and construction projects characterized by complex material composition and steep slope. This study experimentally investigated the erosion differences in engineering accumulations with three soil textures. Based on field survey, a laboratory experiment of engineering accumulation underlying surfaces, representing the Northern Shaanxi sand, Central Shaanxi Plain loam, and Jiangxi clay area, was conducted under simulated rainfall condition. Effects of rainfall intensity and gravels content on runoff and sediment yielding and erosion were investigated. The engineering accumulation plot was 5 m×1 m with a slope of 25°. Rainfall intensities were 1.0, 1.5, 2.0 and 2.5 mm/min and mass fractions of gravels were 0, 10%, 20% and 30%, respectively. Soil texture was clay, sand and loam. Runoff generation time, runoff velocity, runoff rate and erosion rate were determined. Each experiment was controlled within 45 min from the initiation of runoff to the end. Sediment concentration was calculated by traditional oven-drying method. Totally, 48 simulated rainfall events were examined in this study. Results showed that runoff generation was earlier in the loam and clay accumulations than in the sandy accumulation. Under the same experimental conditions, the averaged runoff velocity for the accumulations with gravels decreased from 8.3% to 27.3% in comparison with the pure accumulation, in the decreasing order of clay, loam and sandy accumulations. The averaged runoff velocity was significantly correlated with rainfall intensity for the 3 accumulations. Averaged runoff rate on the sandy accumulation was 20.7% and 18.8% lower than the loam and clay accumulations, respectively. The averaged runoff rate increased from 42.9% to 253.4% as rainfall intensity increased from 1.5 to 2.5 mm/min. Averaged runoff rate had a high correlation with rainfall intensity (P<0.01). The average erosion rate of the sandy accumulation was 3.0 times that of the loam accumulation and 2.3 times that of the clay accumulation. The averaged erosion rates for the 3 accumulations increased from 153.1% to 1219.9% while rainfall intensity increased from 1.0 to 2.5 mm/min. However, there was a significantly negative linear relationship between averaged erosion rate and gravel content (P<0.05). As rainfall intensity increased from 1.0 to 2.5 mm/min, runoff volume increased from 42.2% to 253.2% and erosion amount increased from 178.9% to 1589.1%. Averaged erosion amount of the sandy accumulation was 4.5 times that of the loam accumulation and 3.4 times that of the clay accumulation. For the 3 accumulations, erosion amount was significantly correlated with runoff volume and rainfall intensity. Results from our study may provide important data for establishing a model of soil and water loss from engineering accumulations in production and construction projects.