工程堆积体坡面细沟形态发育及其与产流产沙量的关系

为揭示工程堆积体坡面细沟形态动态变化规律以及细沟形态指标与侵蚀产流产沙量之间的关系，选取5、9、13和17 L/min 4个放水流量，模拟0.5、1.0、1.5和2.0 mm/min雨强条件，对24°、28°和32°共3个坡度工程堆积体进行冲刷试验，选取沟深、沟宽、宽深比和断面积等指标刻画侵蚀过程中细沟形态变化。结果表明：1）随冲刷历时增加，在前9 min内沟宽和沟深快速发育，沟宽发育宽度占总宽度的57%～90%，沟深发育深度占总深度的38%～73%；2）宽深比随冲刷延长呈先减小后趋于稳定的变化过程，宽深比在0～27 min内快速减小，细沟沿流程纵深方向发育的能力减弱，在27 min之后保持稳定，最终恒定在0.81～1.48，表明细沟断面形态最终大致呈矩形形状；3）沟宽和沟深均随流量的增大而增大，与坡度相比流量对细沟发育的影响更显著；4）沟宽和沟深与放水时间之间存在对数函数关系，断面积与放水时间之间存在线性函数关系，沟宽与径流量之间存在指数函数关系，沟深与径流量、断面积与累计产沙量和累计径流量之间存在幂函数关系。坡面细沟形态的发育过程存在时间差异性，断面积可用来描述侵蚀量的变化过程，宽深比可作为表征工程堆积体坡面细沟发育方向和能力的重要指标。该研究可以为工程堆积体坡面细沟形态指标的动态变化量化提供参考。

Rill morphology development of engineering accumulation and its relationship with runoff and sediment

Recently, infrastructure construction developed rapidly and produced a large amount of engineering accumulation, which becomes a new critical point of soil and water loss. Particularly, rills formed quickly on the slope of engineering accumulation under high rainfall intensity and triggered intense soil erosion. Therefore, it is essential to study on the dynamic process of rill development and its impact on runoff and sediment yield. In this study, scouring-erosion experiments were conducted on steep slopes of engineering accumulation under different slope gradients (24°, 28° and 32°) with different flow discharge (5, 9, 13 and 17 L/min), simulating the surface runoff process under the rainfall intensity of 0.5, 1.0, 1.5 and 2.0 mm/min. The zonal soil type in test area is Heilu soil. The experimental plots were constructed in engineering excavated slope, meanwhile, soil parent material was the Loess of Malan at first and then turned into spoil derived from construction sites. The spoil here was sandy loam, with a soil-stone ratio more than 9:1 and the size of particles <1 mm. Each plot was 20 m long and 5 m wide, with 0.5 m deep soil layer and without vegetation. It was used to simulate the dumping engineering accumulation of gully region in loess plateau. According to the experiment design, runoff plot was divided into 5 one-meter-wide smaller plots by iron sheets, one of which was rebuilt as steps. To ensure the same original background, four rill experiment plots were backfilled and compacted after last experimental events. Because the randomness of the slope rill development may cause much difficulty on continuous observation, the slope surface was slightly concavely shaped to form a single rill. The morphological parameters such as rill width, rill depth, width-depth ratio and sectional area were selected to reveal the dynamic change of rill shape during erosion processes. The results showed: 1) The rill width and the rill depth both rapidly increased within the first 9 mins. The rill width accounted to 57%-90% of the ultimate width and the rill depth accounted to 38%-73% of the final depth.;2) With the scouring time continuing, the width-depth ratio first decreased and then showed a stable trend. Within the starting 27 mins, the width-depth ratio rapidly decreased and indicated the attenuated ability of rill development along the lengthways slope, finally, the ratio was stable between 0.81 and 1.48, with the ultimate rill section presented as a rectangular shape. 3) The rill width and rill depth had a positive correlation with flow intensity and flow intensity had a more significant effect on rill development compared to slope gradients. 4) The rill width and rill depth showed logarithmic relationships with discharge time; the sectional area had a linear relationship with discharge time; the rill width had an exponential relationship with runoff; the rill depth had a power function relationship with runoff; the sectional area had power function relationships with both cumulative sediment yield and cumulative runoff. Temporal variability existed in rill morphological development on slope. As a whole, sectional area described the dynamic process of erosion and the width-depth ratio was an important indicator to reveal the characteristics of rill morphological development and erosive ability. This research may provide some theoretical reference for quantifying dynamic changes of rill morphology index on slopes of engineering accumulation.