人工模拟降雨条件下红壤团聚体流失特征研究

以第四纪红粘土发育红壤为研究对象,通过室内模拟降雨和放水冲刷组合试验,研究了不同降雨强度(0,60,90,120mm/h)和放水流量(5,7.5L/min)下红壤坡面团聚体流失特征,分析了团聚体平均重量直径(MWD)、几何平均直径(GDM)、分形维数(D)和平均重量比表面积(MWSSA)的变化特征。结果表明:侵蚀泥沙中0.05mm微团聚体初始含量在19%~58%之间,随产流时间的延长先降低后趋于稳定;0.25mm大团聚体含量最高,随产流时间的延长先升高后趋于稳定。相同降雨强度下,当放水流量由5L/min增大到7.5L/min时,团聚体MWD和GMD有所增大,D和MWSSA有所减小。无降雨时,泥沙中团聚体的MWD和GMD低于有降雨时的MWD和GMD,而D和MWSSA高于有降雨时的D和MWSSA。相同放水流量下,随着降雨强度增强,团聚体的MWD和GMD呈增大趋势,D和MWSSA呈减小趋势。

Aggregate Loss Characteristics on Red Soil Slope Under the Combination of Rainfall Simulator and Scouring Flow

To understand the characteristics of erosive aggregate loss in tropical and subtropical zones,a combination experiment of two discharge flow (5 L/min and 7.5 L/min) and four simulated rainfall intensities (0 mm/h,60 mm/h,90 mm/h,120 mm/h) was conducted.The variation characteristics of aggregates,such as mean weight diameter (MWD),geometric mean diameter (GMD),fractal dimension (D),mean weight soil specific area (MWSSA),were analyzed.The results showed that:the aggregates of ＜0.05 mm occupied 19％～58％ of the total sediment during the early phase of the event,and the tendency declined first then stabilized with rainfall duration.The content of ＞0.25 mm aggregates in erosive sediment was highest,and the tendency increased first and stabilized later,with the rainfall duration.When the discharge flow increased from 5 L/min to 7.5 L/min under the same rainfall intensity,MWD and GMD of aggregates increased,while D and MWSSA decreased.MWD and GMD of aggregates in the sediments without rainfall were lower than that in the rainfall;however,D and MWSSA of aggregates in the sediments without rainfall were higher than those with rainfall.Under the condition of the same rainfall,MWD and GMD increased as rainfall intensity increased,while D and MWSSA decreased.