【摘要】：土地資源的損失已成為全球性的資源環(huán)境問題,而中國(guó)等發(fā)展中國(guó)家所面臨的狀況尤為嚴(yán)重。細(xì)溝溝道中的水流攜帶著大量的泥沙,加劇細(xì)溝的土壤侵蝕和水土流失。細(xì)溝水流侵蝕力和搬運(yùn)能力均遠(yuǎn)遠(yuǎn)大于雨滴打擊和坡面片狀水流所具有的侵蝕力和搬運(yùn)力,坡面水蝕動(dòng)力和細(xì)溝發(fā)育過程相互影響、相互作用,同時(shí)又受流量、坡度和坡長(zhǎng)等外界條件的影響。本文以黃土為研究對(duì)象,采用室內(nèi)放水沖刷的方法在12m長(zhǎng)土槽上進(jìn)行細(xì)溝徑流侵蝕研究,分別在5個(gè)坡度(5。,10°,15°,20°,25°)和3個(gè)流量(2,4,8 L/min)控制條件下研究黃土細(xì)溝徑流流速沿坡長(zhǎng)變化的規(guī)律,分析細(xì)溝侵蝕形態(tài)變化過程、細(xì)溝徑流流速與流量和坡度的關(guān)系,侵蝕產(chǎn)沙量與細(xì)溝徑流流速的關(guān)系,以探究黃土發(fā)生細(xì)溝侵蝕時(shí)的臨界剪切力和最大剝蝕率。本研究對(duì)于揭示坡面土壤侵蝕過程及其內(nèi)在規(guī)律、建立土壤侵蝕物理模型、提高土壤侵蝕預(yù)測(cè)和預(yù)報(bào)水平,具有重要的理論意義和實(shí)際應(yīng)用價(jià)值。本研究得到以下結(jié)論：(1)細(xì)溝沖刷后形成的細(xì)溝深度呈現(xiàn)隨著坡長(zhǎng)的增加細(xì)溝深度先增加后減小的趨勢(shì)。距放水口0～2m段,細(xì)溝深度具有最大值；大坡度大流量時(shí)距放水口0.5 m左右細(xì)溝深度出現(xiàn)最大值。表明在放水沖刷試驗(yàn)中距放水口0-2 m處細(xì)溝侵蝕最強(qiáng)。細(xì)溝內(nèi)跌穴出現(xiàn)沿坡長(zhǎng)分布具有隨機(jī)性,細(xì)溝深度在沿坡長(zhǎng)發(fā)育過程中呈現(xiàn)波動(dòng)性。(2)黃土細(xì)溝侵蝕中坡度和流量是影響細(xì)溝徑流流速的主要因素,流速隨坡度和流量增加而增加。細(xì)溝徑流平均流速與坡度、流量成冪函數(shù)關(guān)系,擬合經(jīng)驗(yàn)公式為v=1.488·q0.342S0.644。坡度一定條件下,細(xì)溝徑流流速與放水流量之間呈冪函數(shù)關(guān)系：v=α.Qb,相關(guān)分析表明隨著流量變化,細(xì)溝流速可以用經(jīng)驗(yàn)公式很好的擬合。(3)細(xì)溝徑流流速沿坡長(zhǎng)0-8 m時(shí)呈現(xiàn)迅速增加的加速狀態(tài),在8-12 m坡長(zhǎng)段細(xì)溝徑流流速增加速度減緩,流速變化趨于平衡,細(xì)溝侵蝕達(dá)到動(dòng)態(tài)平衡。細(xì)溝徑流流速與坡長(zhǎng)之間存在冪函數(shù)關(guān)系,擬合經(jīng)驗(yàn)公式為v=c.Ld。擬合系數(shù)c的變化范圍為0.1772～0.8836,指數(shù)d變化范圍為0.0747～0.3265。(4)細(xì)溝徑流剪切力隨坡長(zhǎng)的變化可用冪函數(shù)方程描述：τ=k·Ln,其中系數(shù)n的值均為負(fù)數(shù),表明徑流剪切力隨坡長(zhǎng)變化呈遞減趨勢(shì)；系數(shù)k表現(xiàn)為坡度相同時(shí),流量越大k值越大；當(dāng)流量相同時(shí),隨著坡度的增加k值也會(huì)逐漸增大。k值變化與徑流剪切力在不同坡度和流量條件下的變化趨勢(shì)相同,因此k值可以用來描述徑流剪切力隨坡度和流量變化的分布特征。(5)試驗(yàn)坡度和水流流量對(duì)徑流泥沙含量和徑流剪切力的影響是相似的,都會(huì)隨著坡度和流量的增大而增大,但是影響關(guān)系是不同步的,即徑流泥沙含量的耦合作用效果要大于徑流剪切力。細(xì)溝內(nèi)徑流剪切力隨著泥沙含量的增加呈減小趨勢(shì),徑流剪切力與泥沙含量之間的關(guān)系可以用線性函數(shù)表達(dá)為：τ=m+p·c。(6)徑流剪切力和剝蝕率是研究徑流對(duì)細(xì)溝內(nèi)泥沙侵蝕強(qiáng)度的指標(biāo),細(xì)溝內(nèi)剝蝕率呈現(xiàn)隨坡長(zhǎng)增加而遞減的分布特征,細(xì)溝內(nèi)徑流剪切力與徑流剝蝕率呈顯著線性關(guān)系,且隨徑流剪切力值增大徑流剝蝕率也增大,二者之間的關(guān)系可以用線性方程來模擬：Drmax=a+b·x。計(jì)算得到本試驗(yàn)土壤的可蝕性參數(shù)Kd值為0.1361 kg/(m2·s),臨界剪切力T0值為0.2367 N/m2。
[Abstract]:The loss of land resources has become a global resource environment problem, and the situation of the developing countries such as China is particularly serious. The water flow in the channel of the fine trench carries a large amount of sediment, which increases the soil erosion and soil erosion of the fine trench. The erosion force and handling capacity of the water flow of the fine trench are much larger than that of the raindrop striking and surface-like water flow, and the interaction and interaction between the water erosion power and the fine trench development process of the slope surface are influenced by the external conditions such as flow, slope and slope length. In this paper, on the basis of loess as the research object, the runoff erosion of the fine trench is carried out on the 12m long soil tank by using the method of indoor water discharge and erosion, and the law of the change of the flow velocity along the slope of the loess fine trench is studied under the control conditions of 5 slope (5., 10 擄, 15 擄, 20 擄, 25 擄) and 3 flow (2, 4, 8 L/ min), respectively. The relationship between the flow velocity of the fine trench and the flow rate and the slope of the fine trench is analyzed, and the relationship between the sediment concentration and the flow velocity of the fine trench is analyzed to study the critical shear and the maximum erosion rate at the time of the fine trench erosion in the loess. The study is of great theoretical significance and practical application value to reveal the process of soil erosion and its internal law in the slope surface, to establish a physical model of soil erosion, to improve the prediction and forecast of soil erosion. The following conclusions are obtained in this study: (1) The depth of the fine trench formed after the fine trench is washed is shown to decrease with the increase of the slope length and the depth of the fine trench. The depth of the fine trench has a maximum value from 0 to 2m of the water discharge port, and the maximum value of the depth of the fine trench at the distance of about 0.5 m from the water outlet when the large-grade large flow is large. It is shown that the erosion of the fine trench at 0-2m from the water outlet is the strongest in the water-discharge flushing test. There is randomness in the long distribution along the slope, and the depth of the fine trench presents the fluctuation in the course of the long development of the slope. (2) The slope and flow rate in the erosion of the fine trench of the loess are the main factors that affect the flow velocity of the fine trench, and the flow velocity is increased with the increase of the slope and the flow rate. The average flow velocity of the fine channel runoff is the power function relation with the slope and the flow rate, and the fitting experience formula is v = 1. 488. q0. 342so. 644. There is a power function relation between the flow velocity of the fine trench and the discharge water flow under a certain condition: v = 1. Qb, the correlation analysis shows that with the change of flow, the flow rate of the fine channel can be well fitted with the empirical formula. (3) The flow velocity of the fine trench is increased rapidly along the slope length of 0-8 m, and the velocity of the flow velocity of the fine channel in the long section of the 8-12 m slope is reduced, the flow rate change tends to be balanced, and the erosion of the fine trench reaches the dynamic balance. There is a power function relation between the flow velocity of the fine channel and the length of the slope, and the formula of the fitting experience is v = c. Ld. The variation range of the fit coefficient c is 0.1772-0.8836, and the variation range of the index d is 0.0747-0.3265. (4) The shear force of the fine trench can be described by the power function equation with the change of the slope length: xt = k. Ln, where the value of the coefficient n is negative, indicating that the runoff shearing force is decreasing with the change of the slope length; when the coefficient k is the same as the slope, the greater the value of the higher k value of the flow; and when the flow is the same, As the slope increases, the value of k also increases. The k-value change is the same as that of the runoff shearing force under different slope and flow conditions, so the k-value can be used to describe the distribution characteristics of the runoff shearing force with the change of the slope and the flow rate. (5) The effect of the test slope and the flow rate on the runoff and sediment content and the runoff shear force is similar, which will increase with the increase of the slope and the flow rate, but the influence relation is not synchronous, that is, the coupling effect of the runoff and sediment content is greater than the runoff shearing force. The flow shear force in the fine trench decreases with the increase of the sediment content, and the relation between the runoff shear force and the sediment content can be expressed by the linear function as: m = m + p 路 c. (6) The runoff shearing force and the denudation rate are the index of the study run-off on the erosion intensity of the sediment in the fine trench. The erosion rate in the fine trench presents a decreasing distribution characteristic along with the increase of the slope length, and the runoff shear force in the fine trench is linearly related to the runoff and denudation rate, and the runoff erosion rate is increased along with the runoff shearing force value, and the relationship between the two is simulated by the linear equation: Drmax = a + b 路 x. The Kd value of the soil in this test is 0.1361 kg/ (m2 路 s), and the critical shear force T0 is 0.2367N/ m2.
【學(xué)位授予單位】：西南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：S157

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