本文選題：坡面水流 + 紅壤團(tuán)聚體　； 參考：《華中農(nóng)業(yè)大學(xué)》2017年碩士論文

【摘要】：我國南方紅壤丘陵區(qū)人口密度大,丘陵坡地利用率高,土壤侵蝕退化嚴(yán)重。同時,該區(qū)域降雨集中且強(qiáng)度大,分散的地表徑流由于受到地形影響逐漸集中,從而沖刷地表而產(chǎn)生坡面侵蝕。本研究選取第四紀(jì)紅黏土發(fā)育的紅壤作為研究對象,系統(tǒng)的分析了不同水流含沙量和坡面糙度條件下,坡面流水力學(xué)特性的變化及其對紅壤團(tuán)聚體破壞剝蝕的影響,從機(jī)理層面揭示坡面流內(nèi)團(tuán)聚體輸移破壞規(guī)律。主要取得的結(jié)論如下:1.通過對5種模擬糙度和6種不同沖刷距離組合下3種粒徑的紅壤團(tuán)聚體在坡面水流內(nèi)的剝蝕破壞規(guī)律的研究得出:(1)在相同運移距離條件下,隨粒徑和糙度的增加團(tuán)聚體剝蝕破壞程度呈增加趨勢,與粒徑相比,糙度對剝蝕破壞程度的影響更大。(2)相同模擬糙度下,隨著運移距離的增加,剝蝕率均呈拋物線形先增大后減小的趨勢;各運移距離下,7~5 mm粒徑團(tuán)聚體的剝蝕率隨糙度的增加而增加;5~3 mm和3~1 mm粒徑團(tuán)聚體在各運移距離內(nèi)隨糙度的增加變化規(guī)律不一致。(3)團(tuán)聚體剝蝕破壞程度隨徑流水深、阻力系數(shù)、水流剪切力的增加均呈冪函數(shù)減小后趨于平緩的趨勢,且大粒徑較小粒徑變化趨勢更明顯;但是不同糙度下,水深對團(tuán)聚體剝蝕破壞程度的影響還需在多坡度流量條件下進(jìn)行進(jìn)一步探索。2.選取單一粒徑的紅壤團(tuán)聚體,在4種坡度、5種流量和5種模擬糙度條件下進(jìn)行沖刷試驗,詳細(xì)分析水力學(xué)特性的變化及其對團(tuán)聚體破壞剝蝕的影響。(1)相同糙度條件下,小坡度(8.8%~17.6%)時,隨流量的增加,團(tuán)聚體剝蝕程度下降;而在較陡坡度(26.8%~36.4%)和下墊面糙度較大時,Wr/Wi值隨流量變化規(guī)律有所不同,在大流量(1.0 L·s-1~1.2 L·s-1)條件下Wr/Wi值均有不同程度的下降。(2)在各糙度下,平均流速和水流剪切力隨坡度和流量的增加而增加;徑流水深隨流量的增加而增加,隨坡度的增加而減小,而阻力系數(shù)的變化卻與之相反。隨著下墊面糙度的增加,徑流水深、阻力系數(shù)以及水流剪切力呈增加趨勢,而平均流速呈減小趨勢。(3)多個坡度和流量組合下,Wr/Wi值隨徑流水深變化無明顯規(guī)律,但單一糙度中,Wr/Wi(%)值均隨徑流水深的增加呈現(xiàn)冪函數(shù)增加的趨勢;在不同糙度和單一糙度下,Wr/Wi值均隨阻力系數(shù)和水流剪切力的增加呈冪函數(shù)減小趨勢。3.選取單一粒徑的紅壤團(tuán)聚體,在2種坡度、5種流量和5種不同渾水條件下進(jìn)行沖刷,詳細(xì)分析水力學(xué)特性的變化及其對團(tuán)聚體破壞剝蝕的影響。(1)清水條件下,Wr/Wi值隨流量的增加而增加,表現(xiàn)為團(tuán)聚體剝蝕破壞程度的隨流量的增加而下降;所有處理中,Wr/Wi值均隨含沙量的增大呈現(xiàn)冪函數(shù)的減小趨勢。(2)隨著供沙量和流量的增加,水深均呈增加趨勢;在兩種坡度條件下,流量、供沙量及其之間的交互作用對水深的影響均表現(xiàn)為:流量供沙量交互作用。五種流量下,隨著供沙量的增加,平均流速、雷諾數(shù)和弗汝德數(shù)均呈減小趨勢,坡面流呈現(xiàn)出由紊流急流向?qū)恿骶徚靼l(fā)展的趨勢。各流量下,阻力系數(shù)隨供沙量的增加而變大,且大坡度(15°)條件下表現(xiàn)更為明顯。在各坡度和供沙量組合條件下,阻力系數(shù)均隨雷諾數(shù)的增加呈冪函數(shù)減小趨勢,且有較好的相關(guān)性。(3)在相同流量中,Wr/Wi(%)值隨徑流水深、水流剪切力的增加呈冪函數(shù)降低趨勢,綜合所有不同含沙量數(shù)據(jù),Wr/Wi(%)值隨徑流水深和水流剪切力變化無明顯規(guī)律。本試驗條件中Wr/Wi(%)所有值均隨著阻力系數(shù)的增大呈冪函數(shù)形式減小,團(tuán)聚體剝蝕破壞程度隨阻力系數(shù)增加而增加。
[Abstract]:The red soil hilly area of southern China has a large population density, high utilization rate of hilly slope land and severe soil erosion. At the same time, the rainfall concentration and intensity are large and the scattered surface runoff is gradually concentrated due to the topography effect, thus erosion on the surface of the surface. The red soil developed in the Quaternary red clay is selected as the research object. The variation of hydraulic characteristics of slope surface flow under the conditions of different flow sediment and slope roughness and its effect on the destruction and erosion of red soil aggregates are analyzed systematically. The failure rules of aggregate transport in the slope flow are revealed from the mechanism level. The main conclusions are as follows: 1. by combining 5 kinds of simulated roughness and 6 different scour distances. The erosion damage law of red soil aggregates with grain size in the flow of slope is studied. (1) under the same migration distance, the erosion damage degree of aggregate increases with the increase of particle size and roughness. Compared with the particle size, roughness has a greater impact on the degree of erosion damage. (2) under the same simulated roughness, with the increase of migration distance, peeling off. The erosion rate increases first and then decreases, and the erosion rate of 7~5 mm particle aggregates increases with the increase of roughness, and the variation of 5~3 mm and 3~1 mm aggregates with the increase of roughness is not consistent with the roughness. (3) the degree of erosion and destruction of aggregates follows the depth of runoff, the coefficient of resistance and the shear force of the flow. The increase of the power function tends to be slow after the power function decreases, and the large particle size is more obvious than the small size. But under the different roughness, the influence of the depth of water on the erosion degree of the aggregate should be further explored under the condition of the multi slope flow and the single particle size of the red soil aggregate should be selected by.2., in 4 kinds of slope, 5 kinds of flow and 5 kinds of simulation. Under the roughness condition, the change of the hydraulic characteristics and its effect on the damage and erosion of aggregates were analyzed in detail. (1) the erosion degree of aggregates decreased with the increase of the flow rate under the same roughness (8.8%~17.6%), while the Wr/Wi value changed with the flow rate at the higher gradient (26.8%~ 36.4%) and the lower surface roughness. Under the conditions of large flow (1 L. S-1~1.2 L. S-1), the Wr/Wi value decreased in varying degrees. (2) under the roughness, the average flow velocity and flow shear force increased with the increase of slope and flow; the depth of water increased with the increase of the flow rate, and decreased with the increase of the gradient, but the change of the resistance coefficient was opposite to the underlying surface. The increase of roughness, water depth, drag coefficient and flow shear force showed an increasing trend, and the average flow velocity decreased. (3) under the combination of multiple slopes and flow, there was no obvious law of Wr/Wi value with the depth of water flow, but in the single roughness, Wr/Wi (%) value increased with the increase of the depth of water flow; in different roughness and single. Under the roughness, the Wr/Wi value decreases with the increase of the resistance coefficient and the increase of the flow shear force.3., the single particle size of red soil aggregates is selected, and the 2 gradient, 5 flow and 5 different muddy water conditions are scoured. The variation of the hydraulic characteristics and its effect on the destruction and erosion of the aggregates are analyzed in detail. (1) the value of Wr/Wi under clear water conditions. With the increase of flow, the degree of erosion and destruction of aggregates decreased with the increase of flow rate; in all treatment, the Wr/Wi value decreased with the increase of sediment content. (2) with the increase of sediment supply and flow, the depth of water increased; under the two gradient conditions, the flow, the amount of sediment supply and the interaction between them The effect of the effect on water depth is the interaction of flow supply. Under five kinds of flow, the average flow rate, Reynolds number and Froude number decrease with the increase of sediment supply, and the slope flow shows a trend from turbulent flow to laminar flow. The resistance coefficient increases with the increase of sediment supply and the large slope (15 degrees) under each flow. Under the conditions of slope and sand supply, the resistance coefficient decreases with the increase of the Reynolds number, and has a better correlation. (3) in the same flow, the Wr/Wi (%) value is deep with the diameter flow, the increase of the flow shear force decreases with the power function, and the Wr/Wi (%) value is integrated with all the different sediment content data. There is no obvious law of changing the depth of water and the shear force of water flow. All the values of Wr/Wi (%) decrease in the form of power function with the increase of the resistance coefficient, and the erosion degree of the aggregate increases with the increase of the drag coefficient.

【學(xué)位授予單位】：華中農(nóng)業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：S157.1

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