黄土丘陵区冻土坡面侵蚀过程特征研究

Study on Erosion Process Characteristics of Frozen Soil Slope in Loess Hilly Region

为了探究黄土丘陵区未冻坡面和冻土坡面在不同径流坡长条件下侵蚀之间的差异,在室内进行模拟冷冻和放水冲刷试验,采用3种径流坡长(2 m,4 m和6 m)和2种坡面类型(未冻坡面和冻土坡面),定量研究了未冻坡面和冻土坡面的产流产沙过程和水沙关系。结果表明:(1)未冻坡面和冻土坡面的初始产流时间均随着径流坡长的延长而缩短,在相同径流坡长条件下,冻土坡面的初始产流时间较未冻坡面减少;(2)未冻坡面的平均产流量与平均产沙量和冻土坡面的平均产沙量均随着径流坡长的延长而增大,而冻土坡面的平均产流量随着径流坡长的变化无显著差异;(3)未冻坡面产流率和产沙率的关系分为缓慢和急速增加两个阶段,而冻土坡面的产沙率则随着产流率的增大而增大;(4)累积产流量与累积产沙量之间呈正相关关系,参数c的绝对值与径流坡长呈正比,并且冻土坡面大于未冻坡面。土壤冻结后使初始产流时间大大缩短,径流量的增加伴随着冻结土壤的不断融化导致冻土坡面侵蚀加剧。

In order to explore the differences in erosion between unfrozen slope and frozen slope under different runoff slope lengths in the Loess Hilly Region,simulated freezing and water discharge scouring tests were carried out indoors.Three runoff slope lengths(2 m,4 m and 6 m)and two slope types(unfrozen slope and frozen slope)were used to quantitatively study the runoff and sediment yield process and water sediment relationship between unfrozen slope and frozen slope.The results show that:(1)The initial flow production time of both unfrozen slopes and permafrost slopes decreases with the extension of runoff slope length,and the initial flow production time of permafrost slopes decreases compared with unfrozen slopes under the same runoff slope length;(2)The average flow production,the average sand production on unfrozen slopes and the average sand production on frozen slopes both increase with the extension of runoff slope length,while the average flow production on frozen slopes does not differ significantly with the change of runoff slope length.(3)The relationship between flow production rate and sand production rate on unfrozen slopes is divided into two stages:slow and rapid increase,while sand production rate on frozen soil slopes increases with the increase of flow production rate.(4)There is a positive correlation between cumulative flow production and cumulative sand production,and the absolute value of parameter c is proportional to the runoff slope length,and is greater on the frozen slope than on the unfrozen slope.The freezing of soil shortens the initial flow production time significantly,and the increase in runoff volume is accompanied by the continuous melting of frozen soil leading to increased erosion on the frozen slope.