本文選題：黃土高原　切入點：擾動堆積土體　出處：《中國科學院研究生院（教育部水土保持與生態(tài)環(huán)境研究中心）》2014年碩士論文

【摘要】：隨著西部大開發(fā)的推進和區(qū)域經(jīng)濟建設的需求，黃土高原地區(qū)生產(chǎn)、開發(fā)類建設項目越來越多，由此引起的擾動堆積土體所帶來的土壤侵蝕問題愈發(fā)凸顯。由于遭到劇烈的擾動，松散堆積土體原有土體結(jié)構(gòu)遭到破壞，并且常常缺乏水土保持工程措施和植物措施的保護，在暴雨條件下極易發(fā)生劇烈土壤侵蝕而破壞農(nóng)田、道路等，給人民的生命財產(chǎn)帶來巨大的損失。為了探明擾動堆積土體的土壤侵蝕特性隨坡度和初始水動力條件的變化，我們建設了標準的試驗小區(qū)，探討其在3個坡度、4個放水流量下土壤侵蝕的特性及其發(fā)生的原因和過程。通過整個試驗過程得到以下主要結(jié)論： （1）從小區(qū)的土壤侵蝕特性來看：試驗條件下的產(chǎn)流速率隨時間的變化規(guī)律基本一致，均呈現(xiàn)先增大然后基本穩(wěn)定的變化特性；平均產(chǎn)流速率與放水流量呈線性正相關(guān)關(guān)系；在30L/min的放水流量下產(chǎn)流總量與坡度沒有明顯關(guān)系，其他流量下產(chǎn)流總量隨著坡度的增大而增大。小區(qū)產(chǎn)沙速率隨時間的變化規(guī)律在不同坡度不同放水流量并不完全一致，基本呈現(xiàn)以下2種變化規(guī)律：①在最大放水流量下，產(chǎn)沙速率先迅速增大，然后逐漸減小，最后穩(wěn)定在一定的范圍內(nèi)；②在其他情況下，產(chǎn)沙速率先增大然后基本穩(wěn)定。平均產(chǎn)沙速率與放水流量、坡度均存在線性正相關(guān)關(guān)系，但Ma-Q回歸方程的顯著性水平（Sig.值）要高于Ma-S回歸方程的顯著性水平，說明與坡度相比放水流量對平均產(chǎn)沙速率的影響更大。 （2）徑流含沙量隨時間的變化規(guī)律主要一下有3種：①放水流量較小且坡度較小時，徑流含沙量在較長的一段時間內(nèi)基本穩(wěn)定，在試驗后期（18min）才逐漸減��；②放水流量較大或坡度較大時，徑流含沙量前期（9～12min以前）逐漸減小之后基本穩(wěn)定；③介于前兩種情況之間的徑流含沙量隨時間不斷減小。平均徑流含沙量與放水流量呈線性負相關(guān)關(guān)系，與坡度則呈線性正相關(guān)關(guān)系。試驗條件下產(chǎn)流產(chǎn)沙關(guān)系基本可以用冪函數(shù)y=axb來表達，a值在0.388～1.445之間變化，b值在0.256～0.911之間變化；隨著放水流量和坡度的增大a值在不斷增大，而b值在不斷減��；當放水流量為60L/min時，雖然產(chǎn)流產(chǎn)沙之間仍呈現(xiàn)正相關(guān)關(guān)系，但冪函數(shù)已經(jīng)不能很好地擬合兩者之間的關(guān)系。 （3）各個放水流量下，在小區(qū)中部（斷面3上下）都存在一個流速大小穩(wěn)定在0.3～0.5m/s的斷面。處在該斷面以上的斷面，平均流速隨放水時間整體呈現(xiàn)減小趨勢；處在該斷面以下的斷面，平均流速隨放水時間整體呈現(xiàn)增大趨勢。各觀測斷面的平均水深均隨著放水時間的延長不斷增加；在小區(qū)的上部（斷面1～2）平均水深變化劇烈，而在小區(qū)中下部（斷面3～5）平均水深變化較為舒緩并一直處在0.5mm～1mm之間；平均水深與放水流量無較為明顯的關(guān)系。 （4）試驗條件下坡面流基本為層流，只有在斷面1和部分時段為過渡流；除了個別現(xiàn)象外，坡面流均屬急流范疇；各個放水流量下弗汝德數(shù)與雷諾數(shù)均為負相關(guān)關(guān)系；阻力系數(shù)與雷諾數(shù)存在冪函數(shù)關(guān)系，但與放水流量關(guān)系不明顯。分析阻力系數(shù)沿坡長的變化情況發(fā)現(xiàn)，0～6m的坡長范圍內(nèi)土壤侵蝕強烈，是坡面流中泥沙的主要供給部位；6～20m坡長范圍內(nèi)土壤侵蝕微弱，該區(qū)域?qū)ζ旅媪髦械哪嗌橙杂泄┙o，但供給速率緩慢。坡面阻力系數(shù)與水深呈線性正相關(guān)關(guān)系，因此變化特性與水深基本一致。 （5）水流切應力隨坡長的變化可以很好地解釋小區(qū)土壤侵蝕的主要發(fā)生部位在小區(qū)中上部（0～10m）的原因。水流切應力雖然與單位面積土壤侵蝕速率存在較好的線性關(guān)系，，但由于水流剪切力只代表了水流剝蝕土壤顆粒進入坡面流的能力，且本試驗選取的坡度屬于陡坡范疇，重力侵蝕作用表現(xiàn)強烈，該侵蝕模型已經(jīng)不適合來解釋本試驗條件下侵蝕速率的變化。由于水流功率是反映了坡面流搬運能力，所以水流功率模型能運用于本試驗條件下來反應土壤侵蝕速率的變化。
[Abstract]:With the advance of western development and regional economic construction demand and production in the Loess Plateau, the development of construction projects more and more, the disturbance caused by the accumulation of soil erosion on soil caused by the increasingly prominent. Due to severe disturbance, loose accumulation soil the original soil structure destroyed, and often lack of protection measures and maintain engineering plant measures of soil and water, severe soil erosion and destruction of farmland, prone to storm conditions such as roads, bring huge losses to people's lives and property. In order to explore changes of soil erosion characteristics of soil disturbance accumulation with slope and initial hydrodynamic conditions, we establish a standard test area, on the 3 4 slope, soil erosion characteristics of the water flow and its causes and process. The main conclusions are as follows through the whole test process:
(1) from the area of the soil erosion characteristics: test conditions of runoff rate variation with time is consistent, increased first and then change characteristics is basically stable; average runoff rate showed a linear correlation with the flow discharge and slope flow in total; no obvious relationship between the discharge of 30L/min production and other traffic flow volume increased with the increase of slope area. The sediment rate changes with time at different slope of different discharge is not entirely consistent, characterized by the following 2 basic changes: in the maximum discharge, sediment yield rate first increases rapidly, then decreases gradually, finally stabilized in a certain range; in other cases, the sediment yield rate increases at first and then remained stable. The average sediment discharge rate, there was a positive linear correlation between the slope, but the regression equation was Ma-Q The Sig. value is higher than the significant level of the Ma-S regression equation, indicating that the effect of the discharge flow rate on the average sediment yield is greater than that of the slope.
(2) the variation of runoff sediment concentration with time mainly has 3 kinds: first, the water flow is small and the slope is small, the basic stability of the sediment concentration in a longer period of time, at the end of the experiment (18min) was gradually decreased; the water flow is larger and larger slope, runoff sediment early (9 ~ 12min ago) decreased gradually after basically stable; sediment concentration between the range of the first two cases with time decreases. The average sediment concentration of runoff and discharge showed a linear negative correlation, linear positive correlation with slope. The experimental conditions of runoff and sediment relationship with power function to express y=axb and the a value is between 0.388 ~ 1.445, the b value is between 0.256 ~ 0.911; with the flow discharge and slope increased a value increasing, while the b value decreases; when the water flow is 60L/min, while the runoff and sediment There is still a positive correlation between the two, but the power function can not well fit the relationship between the two.
(3) the water flow rate, in the central area (Section 3) there is a stable flow in the 0.3 ~ 0.5m/s section. In the section above the section, with the overall average velocity of drainage time decreased; in the following section of the section, the average flow velocity with the drainage time showed an increasing trend. The average depth of each observation section increased with the increase of discharge time; in the area of the upper part (section 1~2) with an average depth of change, and in the area in the lower part (section 3~5) with an average depth of change is soothing and has been in the 0.5mm ~ 1mm; the average depth of water flow and no obvious relationship.
(4) the test conditions of overland flow is laminar, only in Section 1 and part time for transition flow; in addition to the individual phenomenon, overland flow is jet flow discharge under each category; Froude number and Reynolds number were negatively correlated; the relationship between the power function of drag coefficient and Reynolds number, but the relationship and the water flow is not obvious. Analysis of resistance coefficient changes along the slope length, slope length of 0 ~ 6m within the scope of intense soil erosion is the main supply of overland flow sediment in the area; 6 ~ 20m slope length range of soil erosion in the region is still weak, the supply of sediment in runoff, but supply the rate of slow slope. The drag coefficient increases linearly with the depth, the change characteristics and depth are basically the same.
(5) the flow shear stress varies with the length of the slope can be well explained by the area of soil erosion mainly occurred in the area of the upper part (0 ~ 10m). The reason of flow shear stress and soil erosion rate per unit area, although there was a good linear relationship, but due to shear stress only on behalf of the soil the particles flow into the erosion of runoff, and the test of the slope slope belongs to the category of the strong performance of the role of gravity erosion, erosion model is not suitable to explain changes in erosion rates under the conditions of this experiment. Because the flow power reflects the transport capacity of overland flow, so the water power model can be used in this experiment down reaction the soil erosion rate of change.

【學位授予單位】：中國科學院研究生院（教育部水土保持與生態(tài)環(huán)境研究中心）
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：S157.1

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