降雨和上方来水条件下工程堆积体坡面土壤侵蚀特征

定量分析降雨和上方来水共同作用下堆积体坡面产流产沙过程,对于完善多驱动力条件下堆积体坡面土壤侵蚀特征具有重要意义。该研究运用人工模拟降雨和冲刷试验,在野外径流小区(7 m×1 m×0.5 m,坡度36°)上分别开展5个降雨强度(40、50、70、100、120 mm/h)、4个上方来水强度(10、15、20、25 L/min)单独作用及共同作用下坡面土壤侵蚀过程试验,比较2种驱动力单独作用及共同下堆积体坡面土壤侵蚀与形态特征。结果表明:1)降雨条件下,堆积体坡面侵蚀过程呈现阶段性差异发育,中小雨强(40、50和70mm/h)条件下,产流率和产沙率随历时延续呈现2个不同阶段(波动、平稳),侵蚀形态为不连续跌坎,大雨强(100和120 mm/h)条件下,产流率和产沙率随历时的延续呈现3个不同阶段(波动、平稳、剧烈),坡面侵蚀形态为细沟。2)上方来水条件下,堆积体坡面侵蚀过程呈现相对平稳发育,坡面侵蚀形态均为细沟。3)上方来水与降雨共同作用下,堆积体坡面侵蚀过程呈现剧烈波动发育,产沙率随历时的延续呈现持续"多峰多谷"变化态势,随着时间延续,产沙率波动振幅逐渐增大,堆积体坡面侵蚀形态均为侵蚀沟,且发育剧烈。4)上方来水和降雨共同作用下,坡面径流量和泥沙量均增大,且泥沙量的增大幅度大于径流量,相比单独降雨,径流量和泥沙量分别增大86%~629%和86%~4914%,相比单独上方来水,径流量和泥沙量分别增大12%~175%和15%~505%。上方来水和降雨共同作用下,汇流与降雨之间存在交互作用,两者对径流和泥沙的影响均显著。研究结果对于完善堆积坡面土壤侵蚀特征及揭示复杂水动力条件下的侵蚀机理具有重要意义。

Characteristics of soil erosion on engineering accumulation slope under the rainfall and inflow conditions

The soil and water loss caused by construction activities are increasing rapidly over the past few years. Soil erosion on new engineered landforms severely threatens the ecological security of construction sites and their surrounding areas. On the slope of the engineering accumulation, the soil erosion significantly depends on the platform inflow. It is necessary to quantitative analysis of the process of runoff and sediment production on the slope of engineering accumulation under the rainfall and inflow conditions. This can be helpful to clarify the characteristics of soil erosion on the slope of engineering accumulation under multiple driving forces. The purpose of this study is to examine the effects of three driving forces(rainfall, inflow and their interactions) on the characteristics of soil erosion and morphological on the slope of engineering accumulation. The rainfall and inflow experiments were conducted on a field runoff plot(in 7 m long, 1 m wide and 0.5 m deep, and with the slope gradient of 36°) under five rainfall intensities(40, 50, 70, 100, 120 mm/h) and four inflow intensities(10, 15, 20, 25 L/min) conditions. The results showed that under the rainfall condition, the stage differential development was observed in the process of soil erosion on the slope of engineering accumulation. Specifically, the runoff and sediment yield presented two different stages(fluctuation, stability) with time under the small and moderate rainfall conditions(40、50 and 70 mm/h), and the erosion morphology was discontinuous falling-sill, whereas, three different stages(fluctuation, stability, and violently) were observed under the heavy rainfall conditions(100 and 120 mm/h), and the erosion morphology was the rill. Under the inflow condition, there was a relatively stable development in the process of soil erosion on the slope of engineering accumulation, and the erosion morphology was the rill. In contrast, under the combined effect of rainfall and inflow, a violent development was observed in the process of soil erosion on the slope of engineering accumulation. Specifically, the runoff yield presented "multi-peak and valley" with time, and the fluctuation of sediment yield gradually increased with time. The erosion morphology was all erosion gullies, and developed violently. Furthermore, under the combined effect of rainfall and inflow, both the runoff and sediment volume on the slope increased, and the increment in sediment was greater than that in runoff. Compared with the rainfall condition, the runoff and sediment volume increased by 86%-629% and 86%-4914%, respectively, while compared with the inflow conditions, these two indicators increased by 12%-175% and 15%-505%, respectively. This finding demonstrates that the inflow, rainfall and a coupled effect between them have significant effects on the process of soil erosion on the slope of engineering accumulation. This study can provide insightful implications to understand the characteristics and dynamic mechanism of soil erosion on the slope of engineering accumulation under complex hydrodynamic conditions.