降雨条件下两种土壤类型工程堆积体坡面水沙关系与侵蚀动力特征

Runoff-sediment relationship and erosion dynamic characteristics for two types of engineering deposits under rainfall condition

随着生产建设活动的日益频繁,其产生的工程堆积体逐渐成为人为水土流失的主要来源。本研究选取风沙土和红土堆积体,通过室内模拟降雨试验,研究了不同雨强(1.0、1.5、2.0、2.5 mm·min^-1)和砾石含量(0、10%、20%、30%)条件下,两种土质工程堆积体坡面侵蚀过程中水沙关系和侵蚀水动力特征的变化。结果表明:风沙土堆积体产沙率随时间呈波动式增大趋势;红土堆积体在1.0 mm·min^-1雨强时先增大后逐渐稳定,其他雨强则迅速下降后呈波动变化的趋势,且雨强越大、砾石含量越小,波动越剧烈。风沙土堆积体在0和10%砾石含量时存在坡面细沟侵蚀,细沟侵蚀阶段的产沙率是片蚀阶段的6.74~57.40倍;红土堆积体坡面侵蚀过程可划分为松散颗粒侵蚀阶段和土石侵蚀阶段,松散颗粒侵蚀阶段产沙率是土石侵蚀阶段的1.05~3.49倍。两类堆积体产沙率均随雨强增大而增大,1.0和1.5 mm·min^-1雨强时产沙率随砾石含量增大而波动变化,雨强>1.5 mm·min^-1时则随砾石含量增大而减小,相同条件下,风沙土堆积体产沙率是红土的1.45~4.14倍。风沙土堆积体侵蚀过程中水沙关系由水大沙少向水大沙多转变,而红土堆积体则呈相反变化:水大沙多时期,风沙土堆积体产沙增速是红土堆积体的1.94~37.60倍;水大沙少时期,红土堆积体产沙减速是风沙土的1.40~21.30倍。总体上,径流功率在描述两类堆积体侵蚀动力过程方面优于径流剪切力,临界径流功率均随砾石含量增大而增大,其中,风沙土堆积体在细沟侵蚀阶段的临界径流功率(0.02~0.04 W·m^(-2))是片蚀阶段的2倍,且两阶段临界径流功率均低于红土堆积体。本研究结果可为工程堆积体侵蚀预测模型的建立提供科学参考。

The engineering deposits produced by the increasing frequency of production and construction activities are the main source of man-made soil erosion.In this study,we examined the change of runoff-sediment relationship and erosion hydrodynamic characteristics with the engineering deposits of aeolian sandy soil and red soil,based on simulated rainfall experiments with different gravel contents(0,10%,20%,30%)and rainfall intensities(1.0,1.5,2.0,2.5 mm·min-1).The results showed that the sediment yield rate of the aeolian sandy soil deposits gradually increased with the duration of rainfall.The sediment yield rate of red soil deposits under 1.0 mm·min-1 rainfall intensity increased first and then gradually stabilized.Under other rainfall densities,there was a trend of fluctuation after rapid decline,the greater the rainfall intensity and the smaller the gravel content,the more intense the fluctuation.When the gravel content was 0 and 10%,there were rills erosion on the slope surface of aeolian sandy soil accumulation,and the sediment yield rate of rill development stage was 6.74-57.40 times of that of the sheet erosion stage.The erosion process of red soil deposits could be divided into two stages:the loose particle erosion and the soil-rock erosion stage.The sediment yield rate of the loose particle erosion stage was 1.05-3.49 times that of the soil-rock erosion stage.In general,the sediment yield rate of two soil deposits increased with increasing rainfall intensity.The sediment yield rate fluctuated with the increases of gravel content at 1.0 and 1.5 mm·min-1,with a decreasing trend under>1.5 mm·min-1.The sediment yield rate of aeolian sandy soil deposits was 1.45-4.14 times of that of red soil deposits under the same rainfall and gravel content conditions.During the erosion process of aeolian sandy soil deposits,the runoff-sediment relationship changed from low sediment concentration to high sediment concentration,while there was a reverse relationship for red soil deposits.During the high sediment concentration period,the increasing rate of the sediment yield rate of aeolian sandy soil deposits was 1.94-37.60 times of that of red soil deposits.For low sediment concentration period,the decreasing rate of the sediment yield rate of red soil deposits was 1.40-21.30 times of that of aeolian sandy soil deposits.In general,the runoff power was better than the runoff shear force in describing the erosion dyna-mics of these two types of deposits.The critical runoff power increased with increasing gravel content.The critical runoff power of aeolian sandy soil deposits during the rill erosion stage(0.02-0.04 W·m-2)was two times of that of the sheet erosion stage,while the critical stream power was lower than that of the red soil deposits.These results provide a scientific reference for modelling soil erosion processes for engineering deposits.