山前洪积扇细沟侵蚀泥沙起动规律试验研究

发布时间：2018-06-09 23:05

本文选题：洪积扇 + 细沟侵蚀　；参考：《兰州大学》2017年硕士论文

【摘要】：细沟侵蚀泥沙起动规律是土壤侵蚀研究的主要内容,国内外学者从细沟侵蚀演变过程、发生机理、临界条件及影响因素等方面进行了大量研究,并取得了丰硕成果,但这些成果大多是基于黄土地区细沟侵蚀的研究,关于山前洪积扇细沟侵蚀泥沙起动规律的研究相对较少。对山前洪积扇细沟侵蚀泥沙起动规律的研究不仅对深化土壤侵蚀规律具有重要意义,研究成果还可应用于地质灾害防治之中。本文通过不同流量(1.5L/s、2.4L/s、3.3L/s)、不同坡度(1°、3°、5°)的土槽冲刷试验,对山前洪积扇细沟侵蚀泥沙起动规律进行研究,主要结论如下:(1)细沟径流平均流速、平均雷诺数随着流量和坡度的增大而增大,流量对平均流速和平均雷诺数的影响大于坡度;瞬时流速自坡顶向下呈现增大的趋势,有一定的波动性;细沟径流雷诺数自坡顶向下有先增大后减小的趋势,其最大值一般发育在坡面中部;流量和坡度的变化对弗洛德数的影响不明显;细沟径流平均流速与流量和坡度的关系可用幂函数很好表示;细沟径流平均剪切力、平均水流功率、平均过水断面单位能量随流量和坡度的增大而呈现增大的趋势;径流剪切力自坡顶向下有减小的趋势,最大值一般出现在坡面顶部;水流功率在坡面不同位置基本保持稳定;过水断面单位能自坡顶向下有增大的趋势,但表现出一定的波动性。(2)细沟径流含沙量在细沟侵蚀过程中呈现先迅速减小再趋于稳定的过程;在试验中期,径流含沙量表现出一定波动性,且随着流量和坡度的增大,波动性逐渐增大;细沟径流平均含沙量随流量和坡度的增大而增大,与平均水流功率的相关性最大;细沟径流平均含沙量与平均径流剪切力、平均水流功率的关系可用指数函数表示,与平均过水断面单位能量的关系可用线性函数表示;细沟土壤侵蚀速率随流量和坡度的增加而增加,与平均水流功率的相关性最大;细沟土壤侵蚀速率与平均径流剪切力、平均水流功率和平均过水断面单位能量的关系可用线性函数很好表示;细沟径流平均含沙量与侵蚀率可表示为流量和坡度的幂函数。(3)少量起动标准下起动粒径与侵蚀物d80关系最为密切,起动粒径与侵蚀物d80的关系可用线性函数很好表示;得出细沟侵蚀非均匀沙起动粒径公式,并根据试验资料得出试验条件下起动粒径关于流量和坡度的经验公式。
[Abstract]:The incipient rule of rill erosion and sediment is the main content of soil erosion research. Scholars at home and abroad have carried out a great deal of research on the evolution process, occurrence mechanism, critical conditions and influencing factors of rill erosion, and have achieved fruitful results. However, most of these results are based on the study of rill erosion in loess area. The study of sediment incipient rule of flood fan in front of mountain is not only of great significance to deepen the law of soil erosion, but also can be applied to the prevention and control of geological hazards. In this paper, by means of soil trough scour tests with different flow rate of 1.5L / s-1 / 2.4L / s-1 / 3.3L / sm and different slope of 1 掳/ 3 掳/ 5 掳), the incipient rule of sediment erosion in front of flood fan rill is studied. The main conclusions are as follows: 1) average flow velocity of rill runoff. The average Reynolds number increases with the increase of flow rate and gradient, the influence of flow rate on average velocity and average Reynolds number is greater than that of slope, and the instantaneous velocity increases from top to bottom and has certain fluctuation. The Reynolds number of rill runoff increases first and then decreases from the top of the slope, and its maximum value is generally developed in the middle of the slope, and the change of flow rate and gradient has no obvious effect on the Frod number. The relationship between average flow velocity and flow rate and slope is well expressed by power function, and the average shear force, average flow power, average cross section energy of rill runoff increase with the increase of flow rate and slope. The runoff shear stress decreases from the top of the slope, and the maximum appears at the top of the slope, the power of the flow is stable in different positions of the slope, and the cross section unit can increase from the top to the bottom of the slope. However, the sediment content of runoff decreases rapidly and then tends to be stable in the process of gully erosion, and in the middle of the experiment, the sediment content of runoff shows a certain fluctuation, and with the increase of flow and slope, the sediment content of runoff decreases rapidly and then tends to be stable in the process of rill erosion, and the sediment content of runoff increases with the increase of flow rate and slope. The average sediment content of rill runoff increases with the increase of flow rate and slope, and the correlation with the average flow power is the greatest, while the mean sediment content of rill runoff and the average runoff shear stress increase gradually, and the mean sediment content of rill runoff increases with the increase of flow and slope. The relationship between the average flow power and the unit energy of the average cross section can be expressed by a linear function, and the soil erosion rate of the rill increases with the increase of the flow rate and the slope, and has the greatest correlation with the average water power. The relationship between soil erosion rate and average runoff shear stress, average flow power and unit energy of cross section can be expressed by linear function. The average sediment content and erosion rate of rill runoff can be expressed as the power function of flow and slope. 3) the starting particle size is most closely related to erosion d80 under a small starting standard, and the relationship between starting particle size and erosion d80 can be well expressed by linear function. The formula of incipient particle size of inhomogeneous sediment in rill erosion is obtained, and the empirical formula of starting particle size on flow rate and slope under test condition is obtained according to the experimental data.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S157;TE88

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