排土场平台-边坡系统沟蚀形态演变与产沙特征

排土场是露天采矿区主要泥沙来源的人造地貌之一，控制排土场土壤侵蚀对矿区高质量发展具有重要意义。该研究采用野外放水冲刷试验，研究排土场平台-边坡系统沟蚀演变及产沙特征。结果表明：1）沟蚀演变中的主导侵蚀方式存在阶段性转变，侵蚀沟形态发育特征也呈阶段性差异，平台侵蚀沟分为沟头形成阶段，溯源-拓宽阶段和稳定阶段3个发育演变阶段；边坡侵蚀沟依次经历覆土层下切阶段，覆土层拓宽阶段，红土层下切阶段和侵蚀减缓阶段。2）边坡是平台-边坡系统主要沙源，其累积产沙量占平台-边坡系统的88.15%～90.16%；覆土层下切阶段和红土层下切阶段是边坡的主要产沙阶段，其累积产沙量分别占边坡的29.72%～53.36%和19.06%～48.88%。3）平台和边坡侵蚀速率均与径流功率的响应关系较优，在平台沟蚀的溯源-拓宽阶段和稳定阶段为线性响应；在边坡沟蚀的覆土层下切阶段和红土层下切阶段为指数响应，拓宽阶段和侵蚀减缓阶段为线性响应。模型建立中需进一步考虑此种响应规律随沟蚀发育演变产生的变化，研究结果可为排土场水土保持措施布设和科学认识沟蚀过程与特征提供参考。

Characteristics of gully topography and sediment on the platform-steep slope system of spoil dump

The spoil dumps are the main sediment source in the open-pit mining area. Its erosion control is of great significance to the high-quality development of the energy zone. On the base of plot construction of platform-steep slope system and field scouring experiments, this article aims to analysis the gully development and sediment process of spoil dumps. The flow rate ranged from 60 L/min to 80 L/min and the time of each run was 45 mins. The results showed that: 1) The gully developed by the combination of different erosion progresses including headcut migration, bed incision, and lateral erosion on the platform-steep slope system. Notably, the gully showed stage differences in topography due to the variation of dominant erosion progress. Gully on platform experienced a three staged development process of headcut formation stage, migration-expansion stage, and stable stage. The gully on steep slope exhibited the four developmental processes of incision of sandy loam layer, expansion of sandy loam layer, incision of clay loam layer, and decelerated stage. No significant differences were found between various flow rates of gully development speed on platform. Whereas, the transformed time increased with flow rate between adjacent gully development stages on steep slope. 2) In terms of sediment process, migration - expansion stage was the main erosion period on the platform. The incision of sandy loam layer and clay loam layer were the main erosion stages on the steep slope with accumulated sediment yields accounting for 29.72%-53.36% and 19.06%-48.88% respectively. Spatially, the runoff shear force and stream power increased by 7.11-120.86 times and 7.59-239.59 times separately, and the erosion rate increased by -0.84-66.20 times after the runoff flowed from the platform into the steep slope. The steep slope was the main sediment source of the platform and steep slope system. Its cumulative sediment yield accounted for 88.15%-90.16% of the total amount of platform and steep slope system. Hence, the separation and control of runoff on platform is a vital way to control gully erosion in the platform-steep slope system of spoil dumps. 3) In terms of flow hydraulics, the platform velocity decreased first and increased then with the gully development. Conversely, the slope velocity decreased gradually. Meanwhile, the runoff shear stress and the runoff stream power increased gradually with the gully development on the platform, and increased first and decreased finally on the steep slope. 4) Comparatively, the erosion rate had a more sensitive response to the stream power than the runoff shear force, and the response regularity differed with gully development stages. The erosion rate linearly responded to the stream power in the migration-expansion stage and stable stage of platform. As for the steep slope, the responses were still linear in the expansion of sandy loam layer and decelerated stage, but were exponential in the incision of sandy loam layer and clay loam layer. Therefore, it is necessary to consider the difference of responses in various gully development stages to improve the applicability of sediment transport model for gully erosion. The results revealed the staged development of gully and sediment process on the platform-steep slope system of spoil dumps. It offers basis for the layout of soil and water conservation measures in spoil dump, and provides reference for scientific understanding of the gully process.