發(fā)布時間：2018-06-09 23:05

  本文選題：洪積扇 + 細溝侵蝕��； 參考：《蘭州大學》2017年碩士論文

【摘要】：細溝侵蝕泥沙起動規(guī)律是土壤侵蝕研究的主要內(nèi)容,國內(nèi)外學者從細溝侵蝕演變過程、發(fā)生機理、臨界條件及影響因素等方面進行了大量研究,并取得了豐碩成果,但這些成果大多是基于黃土地區(qū)細溝侵蝕的研究,關于山前洪積扇細溝侵蝕泥沙起動規(guī)律的研究相對較少。對山前洪積扇細溝侵蝕泥沙起動規(guī)律的研究不僅對深化土壤侵蝕規(guī)律具有重要意義,研究成果還可應用于地質(zhì)災害防治之中。本文通過不同流量(1.5L/s、2.4L/s、3.3L/s)、不同坡度(1°、3°、5°)的土槽沖刷試驗,對山前洪積扇細溝侵蝕泥沙起動規(guī)律進行研究,主要結論如下:(1)細溝徑流平均流速、平均雷諾數(shù)隨著流量和坡度的增大而增大,流量對平均流速和平均雷諾數(shù)的影響大于坡度;瞬時流速自坡頂向下呈現(xiàn)增大的趨勢,有一定的波動性;細溝徑流雷諾數(shù)自坡頂向下有先增大后減小的趨勢,其最大值一般發(fā)育在坡面中部;流量和坡度的變化對弗洛德數(shù)的影響不明顯;細溝徑流平均流速與流量和坡度的關系可用冪函數(shù)很好表示;細溝徑流平均剪切力、平均水流功率、平均過水斷面單位能量隨流量和坡度的增大而呈現(xiàn)增大的趨勢;徑流剪切力自坡頂向下有減小的趨勢,最大值一般出現(xiàn)在坡面頂部;水流功率在坡面不同位置基本保持穩(wěn)定;過水斷面單位能自坡頂向下有增大的趨勢,但表現(xiàn)出一定的波動性。(2)細溝徑流含沙量在細溝侵蝕過程中呈現(xiàn)先迅速減小再趨于穩(wěn)定的過程;在試驗中期,徑流含沙量表現(xiàn)出一定波動性,且隨著流量和坡度的增大,波動性逐漸增大;細溝徑流平均含沙量隨流量和坡度的增大而增大,與平均水流功率的相關性最大;細溝徑流平均含沙量與平均徑流剪切力、平均水流功率的關系可用指數(shù)函數(shù)表示,與平均過水斷面單位能量的關系可用線性函數(shù)表示;細溝土壤侵蝕速率隨流量和坡度的增加而增加,與平均水流功率的相關性最大;細溝土壤侵蝕速率與平均徑流剪切力、平均水流功率和平均過水斷面單位能量的關系可用線性函數(shù)很好表示;細溝徑流平均含沙量與侵蝕率可表示為流量和坡度的冪函數(shù)。(3)少量起動標準下起動粒徑與侵蝕物d80關系最為密切,起動粒徑與侵蝕物d80的關系可用線性函數(shù)很好表示;得出細溝侵蝕非均勻沙起動粒徑公式,并根據(jù)試驗資料得出試驗條件下起動粒徑關于流量和坡度的經(jīng)驗公式。
[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 擄/ 3 擄/ 5 擄), 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.
【學位授予單位】：蘭州大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：S157;TE88

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