稀土元素示踪坡面冲刷侵蚀过程的室内模拟试验研究

Simulation Experimental Study of Soil Erosion Process of Slope Scouring with Rare Earth Elements Tracer

为确定坡面侵蚀产沙的时空演变规律,通过沿坡面垂直分段和分层结合布设不同稀土元素,采用室内放水冲刷试验系统,分析了各坡段侵蚀产沙量和侵蚀率变化过程。结果表明:坡面侵蚀产沙可分为3个阶段:面蚀阶段、沟蚀阶段和沟蚀稳定阶段。试验结束时,上坡段土壤总侵蚀量为17.527 kg,占坡面总侵蚀量的89.2%,其中La和Eu示踪区的侵蚀量各占坡面总侵蚀量的48.1%和23.8%。La,Eu,Yb,Tb,Ce,Nd和Sm 7个示踪区的累积侵蚀量之比为:1∶0.495∶0.184∶0.177∶0.146∶0.030∶0.074,坡面上段、中段和下段累积侵蚀量之比为:1∶0.095∶0.040。试验过程中,上坡段细沟蚀剧烈,中坡段主要以面蚀为主,伴有轻微沟蚀,而下坡段始终以面蚀存在。

In order to definite the temporal and spatial process of soil loss on loess slope surface, the erosion sediment yield and erosion acceleration on different section of sloping land was analysed systematically by placing different rare earth elements into different soil depth and different section across a slope, using the runoff scouring method. The results indicated that the process of sediment yield on slope were divided into three stages： surface erosion stage, interrill erosion stage and rill erosion stability stage. At the end of the experiment, the accumulated erosion of upper slope was 17.527 kg, which accounted 89.2% of total erosion sediment yield of slope, and the total erosion sediment yield of La and Eu tracing areas accounted 41.8% and 23.8% of total erosion sediment yield of slope respectively. The ratios of accumulated erosion of La, Eu, Yb, Tb, Ce, Nd and Sm tracing area were 1：0.495：0. 184：0. 177：0. 146：0.030：0.074. The ratios of accumulated erosion of the upper, middle and lower of slope was 1 ： 0. 095 ： 0. 040. During the whole process of experiment, the rill eroded intensively in the upper part of slope. With slight rill erosion, the surface erosion was a main erosive way in the middle part of slope, and the surface erosion existed during the whole process in the lower part of slope.