黄土坡面水蚀相似性模拟及水蚀动力过程试验研究

发布时间：2018-03-18 14:16

本文选题：模拟降雨　切入点：雨滴特性　出处：《西安理工大学》2016年博士论文　论文类型：学位论文

【摘要】：本研究以土壤侵蚀学、泥沙运动学、河床演变学等学科的理论为基础,以具有严格比尺意义的坡面土壤侵蚀实体模型相似律为研究主线,采用室外定位动态监测、室内人工模拟试验和理论分析相结合的研究方法,研究了汛期天然降雨及模拟降雨的降雨特征、雨滴谱特性、不同降雨动力条件下的侵蚀产沙及运动相似条件,并对坡面放水冲刷条件下的坡面水动力特性及其与天然降雨条件下坡面侵蚀产沙进行对比,初步探索不同水动力作用条件下侵蚀产沙差异的形成机制,以期为建立适合黄土高原区域特性的土壤流失预报模型提供理论依据。论文取得的初步研究成果如下:(1)阐明了模拟降雨与天然降雨侵蚀过程的相似条件,指出模拟降雨不但要雨强过程连续模拟相似、均匀性相当,而且要达到雨滴末速相似,否则雨滴末速的差异会引起降雨产流产沙过程的差异,这是实现坡面水蚀过程模拟动力相似的关键。(2)研发了大型可连续变雨强的模拟降雨试验装置,该装置生成的雨强与雨滴末速分布相匹配,可以进行模拟降雨与天然降雨的雨强和雨滴能量过程的相似模拟。(3)发现了汛期天然降雨主要是由粒径为0.125-0.5mm的雨滴组成的规律,雨滴的末速主要集中在1-5m/s之间,且在1.4m/s和3.4m/s处形成两个明显峰值;其中0.125mm粒径的雨滴末速主要集中在1-4.2m/s之间,0.25mm粒径的雨滴末速主要集中在0.8-5m/s之间,0.375mm粒径的雨滴末速主要集中在1-3.4m/s之间,0.5mm粒径的雨滴末速主要集中在1-4.2m/s之间。同时,模拟降雨也主要是由粒径为0.125-0.5mm的雨滴组成,雨滴的末速主要集中在0.4-3.4m/s之间,且在1.4m/s处形成一个明显峰值;其中0.125mm粒径的雨滴末速主要集中在1-3.4m/s之间,0.25mm粒径的雨滴末速主要集中在1-4.2m/s之间,0.375mm粒径的雨滴末速主要集中在0.6-3.4m/s之间,0.5mm粒径的雨滴末速主要集中在0.4-3.4m/s之间。模拟降雨如果要形成双峰值现象可通过模拟降雨器的双喷头联合运用来进行改进。(4)阐述了汛期天然降雨与模拟降雨条件下坡面径流水动力过程的相似性,模拟降雨基本上能较好模拟出天然降雨的变化过程,以及坡面流平均流速、雷诺数、佛汝德数、阻力系数的变化趋势,表明模拟降雨和天然降雨的水动力过程基本相似。(5)在模拟降雨动力、水动力过程相似条件下,坡面水蚀试验的产流产沙过程变化趋势与天然降雨观测过程一致。在此基础上,建立了试验条件下的坡面侵蚀产沙模型,通过检验,此模型误差较小,可用来计算坡面水蚀产沙量。(6)阐述了降雨试验和放水冲刷试验两种不同的侵蚀动力作用方式导致的差异化侵蚀结果,如降雨试验的含沙量远小于冲刷试验,这可能是由于降雨雨滴是均匀分散于坡面,而放水冲刷试验径流较为集中且全程参与对坡面的侵蚀,因此研究降雨试验与冲刷试验的相似体系,将是一个更加深入的模拟领域。以上成果可为黄土高原水土流失数学模型、特别是机理模型部分的建立提供基础数据和科技支撑。
[Abstract]:In this study, soil erosion, sediment dynamics, riverbed evolution theory as a foundation, with strict slope soil erosion rule significance than solid model similarity law as the main line, the outdoor positioning dynamic monitoring, research method of indoor artificial simulation experiment combined with theoretical analysis, studied the characteristics of rainfall in flood season rainfall and the simulated rainfall, raindrop erosion and sediment movement characteristics, and different rainfall under dynamic conditions similar conditions, and the dynamic characteristics of slope runoff and slope scouring conditions and slope and natural rainfall erosion and sediment yield were compared, explore the formation mechanism of erosion and sediment yield of different hydrodynamic conditions. In order to establish the regional characteristics of the loess plateau soil erosion prediction model provides a theoretical basis. The preliminary research results of the thesis are as follows: (1) illustrates the simulation Similar conditions of rainfall and natural rainfall erosion process, pointed out that the simulated rainfall not only rain intensity continuous process simulation, uniformity, and to reach the terminal velocity of raindrops or similar differences will lead to differences in speed at the end of the process of runoff and sediment yield, which is the key of slope erosion process simulation dynamic similarity. (2) the development of large continuous change of rainfall simulation experiment device of rainfall intensity, rainfall intensity and raindrop velocity distribution at the end of the device generated can match the similarity simulation of rainfall intensity and raindrop energy simulation rainfall and natural rainfall. (3) found that the flood of natural rainfall is mainly determined by the size of 0.125-0.5mm drops composition rule, raindrop terminal velocity mainly concentrated in 1-5m/s, and formed two obvious peak in 1.4m/s and 3.4m/s; the 0.125mm particle size of raindrop terminal velocity mainly concentrated in between 1-4.2m/s, the particle size of 0.25mm The terminal velocity of raindrops is mainly concentrated in 0.8-5m/s, 0.375mm particle size of raindrop terminal velocity mainly between 1-3.4m/s, 0.5mm particle size of raindrop terminal velocity mainly concentrated in 1-4.2m/s. At the same time, rainfall is largely composed of particle size of 0.125-0.5mm drops, the terminal velocity of raindrops is mainly concentrated in the 0.4-3.4m/s, and the formation of a a significant peak at 1.4m/s; the 0.125mm particle size of raindrop terminal velocity mainly between 1-3.4m/s, 0.25mm particle size of raindrop terminal velocity mainly between 1-4.2m/s, 0.375mm particle size of raindrop terminal velocity mainly between 0.6-3.4m/s, 0.5mm particle size of raindrop terminal velocity mainly concentrated in the 0.4-3.4m/s. If you want to simulate rainfall the formation of Shuangfeng value phenomenon by double nozzle is used to simulate rainfall combined transport was improved. (4) described the flood of natural rainfall and slope under simulated rainfall surface runoff water dynamic process is similar to that of the Basically, the simulated rainfall can better simulate the variation process of natural rainfall, overland flow and the average flow velocity, Reynolds number, Froude number, the change trend of the drag coefficient, shows that the hydrodynamic process of simulated rainfall and natural rainfall is similar. (5) in the simulated rainfall power, hydrodynamic process under similar conditions. The processes of runoff and sediment variation trend of water erosion test and natural rainfall observation process. On this basis, a sediment model, under the condition of slope erosion test by test, the model error is small, can be used to calculate the slope erosion and sediment yield. (6) describes the differences in rainfall test and scouring experiment two different modes of action of erosion erosion dynamic results, such as the sediment concentration is far less than the rainfall scouring, this may be due to rainfall is evenly dispersed in the slope, and more runoff scouring experiment Concentrated and full participation in the erosion of the slope, so the research and test system similar to the rainfall erosion test, will be a more in-depth simulation. These achievements as the mathematical model of soil erosion in the Loess Plateau, especially to provide basic data and scientific and technological support to establish a mechanism model part.

【学位授予单位】：西安理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S157.1

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