| 题名 | 黄土坡面细沟侵蚀动力学过程组合小区模拟试验研究 |
| 学位类别 | 硕士 |
| 答辩日期 | 2009 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 陕西 |
| 导师 | 王占礼 |
| 学位专业 | 水土保持与荒漠化防治 |
| 中文摘要 | 我国黄土高原严重的水土流失给当地的可持续发展及黄河下游两岸的安全造成了严重影响与威胁，其中，细沟侵蚀起了严重的影响作用。细沟侵蚀是极其重要的坡面侵蚀过程之一，在坡面侵蚀中具有极其重要地位，在我国黄土地区坡面尤为突出，是国际土壤侵蚀研究的重要对象，我国黄土坡面严重侵蚀的主要方式和强烈侵蚀产沙的重要根源。开展黄土坡面细沟侵蚀动力学过程研究，不仅能深入认识和揭示坡面细沟侵蚀过程与机理，为坡面细沟侵蚀动力学过程模型的科学建立奠定基础，促进坡面侵蚀理论进一步发展，而且还可为黄土坡面水土保持措施规划设计及坡面水土流失治理提供重要科学依据。本论文采用具有定流量人工放水的组合小区模拟降雨试验方法，对同坡度不同雨强及同雨强不同坡度件下的黄土坡面细沟侵蚀动力学过程进行了模拟试验研究，分析研究了坡面细沟侵蚀产沙过程、细沟水流水力学特征、细沟侵蚀产沙过程动力学机理，细沟汇入沙对坡面细沟侵蚀的影响及其贡献。主要研究结果如下：1．基于对坡面细沟径流过程、侵蚀过程、水流含沙量变化过程、输沙过程及水沙关系的分析，研究了坡面细沟侵蚀产沙过程。细沟径流、侵蚀、水流含沙量及输沙随径流过程的变化，皆可用幂函数方程描述，随雨度及坡度的变化除细沟径流用二元对数方程描述外，其余皆可用二元幂函数方程描述；各种雨强及坡度下，细沟侵蚀及输沙模数都随细沟径流深的增大而增大，并皆可用指数方程描述。２．基于对坡面细沟水流流速、水流阻力、水流流态的分析，阐明了坡面细沟水流水力学特征。细沟水流流速、水流阻力系数随径流过程的变化，皆可用指数方程描述，随雨强及坡度的变化可分别用二元对数及二元指数方程描述；细沟径流过程中的水流流态，基本一直处于层流，并总是处于急流。不同雨强及不同坡度下，一次降雨径流过程的水流平均雷诺数变化在327～457间，平均佛汝德数变化在6.309-7.336间，平均而言，细沟水流流态处于层流，并皆属于急流。 ３．基于对坡面细沟侵蚀及输沙对细沟水流剪切力、单位水流功率及水流功率响应关系的分析，揭示了坡面细沟侵蚀产沙过程动力学机理。降雨径流侵蚀与输沙过程中，细沟侵蚀率及输沙率对水动力参数响应的相关系数大小顺序分别为水流切应力（R=0.83）>水流功率（R=0.42）>单位水流功率（R=0.22）及水流切应力（R=0.88）>水流功率（R=0.47）>单位水流功率（R=0.22）；试验条件下，水流切应力是与细沟侵蚀及输沙过程关系最密切的水动力指标，是描述细沟侵蚀产沙动力学过程最好的动力参数，细沟侵蚀产沙过程的发生发展根源于细沟水流剪切力的动力作用。４．探讨了细沟汇入沙对坡面细沟侵蚀的影响及其贡献。细沟汇入沙来源于细沟顶部汇入沙及细沟间汇入沙。细沟顶部汇入沙、细沟间汇入沙、细沟水流剪切力及三者之间的交互作用对细沟侵蚀的影响，可用三元对数方程描述，它们对细沟侵蚀影响的贡献率分别为10.84%、0.44%、65.22% 及6.97%。5．全文较为系统地研究了不同雨强、坡度及其组合与汇入沙条件下细沟侵蚀产沙指标及水文水力学参数的变化过程、响应特征、耦合关系，逐一分析了相应的成因，并取得了相应的经验描述方程，实现了黄土坡面细沟侵蚀动力学过程机理的模拟与阐明。在试验方法设计、侵蚀产沙过程动力学机理、细沟汇入沙对细沟侵蚀影响的贡献方面更较创新。 |
| 英文摘要 | Severe soil erosion on the Loess Plateau in China has resulted in great impacts on local sustainable development and great threat to the security on both sides of the lower reach of Yellow River, of which rill erosion plays an important influencing role. Rill erosion is one of the main erosion processes and the major sources of sediment yield on hillslope of loess region. So study of rill erosion is extremely important not only to recognize and reveal rill erosion processes and its mechanism, and to further develop process-based model of rill erosion, but also to provide an important scientific basis for making decisions of soil and water conservation measures and controlling soil and water loss on loess hillslope.With multi-plot-based experiments of simulated rainfall and the addition of a steady in-flow at the top of the multi-plot system, the dynamic processes of rill erosion on loess hillslope are studied under five different rainfall intensities with same slope and five different slopes with same rainfall intensities. The study focus on the processes of rill erosion and sediment yield, the features of rill flow hydraulics, the dynamic mechanism of rill erosion and sediment yield processes, and the impacts of influx of sediment onto rill on rill erosion and its contribution on loess hillslope. The main findings are as follows:1. Prosesses of rill erosion and sediment yield on hillslope,Rill runoff, rill erosion, sediment load in rill flow and sediment transport changing with runoff can be well described with power equation. A dual power equation can be used to describe the changes with rainfall intensities and slopes, except a dual logarithmic equation for the situation of rill runoff. Under different rainfall intensities, different slopes, and different rainfall intensities and slopes, rill erosion modulus increases along with runoff depth and can be described by an exponential equation.2. Features of rill flow hydraulics on hillslope: Rill flow velocity and the Darcy-Weisbach roughness coefficient increases along with time under different rainfall intensities and the relationship can be described well with an exponential equation. their relation to rainfall intensity can be described by a dual logarithmic equation; to slope, by a dual exponential equation; rill flow is laminar and rapids.The average Reynolds number, a measure of fluid turbulence, varies between 327 and 457 and the average Froude number between 6.309 and 7.336, indicating that rill flow is laminar flow and rapids.3. Dynamic mechanism of rill erosion and sediment yield processes on hillslope: In the process of rainfall-runoff erosion, rill erosion rate on the response to flow shear stress shows an overall increase with increased shear stress, and a linear equation can be used to describe the relationship well (R=0.8292); with the increased unit flow power, rill erosion rate increases firstly and then decreases, with a poor correlation for a used parabolic equation (R=0.2170); and rill erosion rate increases with increased flow power and the response relationship can be described by a parabolic equation (R=0.4176). Under the experimental conditions, flow shear stress is the closest hydrodynamic parameter related to rill erosion.4. Impacts of influx of sediment onto rill on rill erosion and its contribution on hillslope: Sediment flows onto rill is from rill top and interrill. Impacts of influx of sediment onto rill from rill top, influx of sediment onto rill from interrill, and rill runoff shear stress on rill erosion under different rainfall intensities with same slope, different slopes with same rainfall intensity, and different rainfall intensities and slopes can be described by a ternary logarithmic equation. The contributions of influx of sediment onto rill from rill top, influx of sediment onto rill from interrill, rill runoff shear stress, and the interaction of the three terms to rill erosion are 10.84%, 0.44%, 65.22%, and 6.97% . 5. This paper has studied the changing process,the reponding characteristics and the correlation of rill erosion and sediment yield and hydrological indicators systematically, under the condition of different rainfall intensity, slope and influx of sediment onto rill,then analyzed the corresponding causes of the problem and got the corresponding experience equations, and simulated and clarified the mechanism of dynamic processes of rill erosion on loess hillslope. It’s an innovation on the test design, the process of erosion and sediment yield kinetic mechanism, and the impacts of influx of sediment onto rill on rill erosion and its contribution on hillslope. |
| 公开日期 | 2011-07-01 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.iswc.ac.cn/handle/361005/4130]  |
| 专题 | 水土保持研究所_水保所知识产出(1956-2013) |
| 推荐引用方式 GB/T 7714 | . 黄土坡面细沟侵蚀动力学过程组合小区模拟试验研究[D]. 陕西. 中国科学院研究生院. 2009. |
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