發(fā)布時間：2019-06-20 10:09

【摘要】：黃土高原水蝕風蝕交錯帶是黃土高原土壤侵蝕最為劇烈的區(qū)域及黃河下游河床粗泥沙的主要源區(qū),該區(qū)域內(nèi)有特殊的片沙覆蓋黃土地貌,存在片沙在上黃土在下的沙土二元結構坡面。本論文以此沙土二元結構坡面為研究對象,通過野外調(diào)查采樣,確定沙土二元結構坡面上下層土壤理化性質(zhì)的差異,在此基礎上,以覆沙厚度、雨強和坡度為影響因子,設計不同的實驗組合,對沙土二元結構坡面進行人工模擬降雨觀測實驗,研究覆沙坡面的產(chǎn)流產(chǎn)沙過程特征,確定覆沙坡面產(chǎn)流產(chǎn)沙對不同影響因子的響應特征,分析坡面徑流流速變化規(guī)律及水沙耦合關系等,得到以下主要結果:(1)探索了片沙覆蓋坡面沙土二元結構剖面理化性質(zhì)的差異:沙土二元結構剖面沙層和黃土層的土壤結構、土壤容重、顆粒組成、孔隙度、飽和導水率、土壤特征曲線等都差異明顯,尤其是顆粒組成、飽和導水率和水分特征曲線,土壤特性在上下層的較大差異,為沙土二元結構坡面特殊的水分入滲、產(chǎn)匯流、土壤侵蝕、物質(zhì)運移等過程奠定了基礎,導致這種坡面可能發(fā)生特殊的侵蝕過程。(2)分析了片沙覆蓋黃土沙土二元結構坡面產(chǎn)流特征:不同覆沙厚度對坡面徑流速率的影響不同,產(chǎn)流后,徑流速率在0.5cm和2cm覆沙坡面時隨降雨進行先遞增后趨于準穩(wěn)定狀態(tài),在5cm和10cm覆沙坡面,隨降雨進行先快速增加,然后又緩慢降低,在15~25cm覆沙坡面徑流速率隨降雨進行陡增陡降;不同雨強條件下覆沙坡面徑流速率隨降雨歷時變化的整體趨勢是先遞增,到達峰值后波動遞減或快速遞減,隨雨強增大,坡面產(chǎn)流速率變化加劇;不同坡度下覆沙坡面產(chǎn)流速率有明顯差異,10°、15°坡面徑流速率的變化趨勢接近,徑流速率小,產(chǎn)流后緩慢遞增,之后趨于穩(wěn)定;20°、30°坡面徑流速率變化趨勢接近,先增大,到達峰值后開始減小;25°徑流速率變化最為特別,徑流速率陡增陡減,其峰值比其他坡度都都大。次降雨60min內(nèi),覆沙厚度與累計產(chǎn)流量成極顯著負相關,雨強與徑流量呈極顯著正相關,坡度與徑流量成極顯著正相關且在25°左右存在臨界坡度。雨強變化對產(chǎn)流量的影響最大,貢獻率達64%,其次為覆沙厚度,坡度的影響最小。徑流量與坡度、雨強、覆沙厚度的回歸方程為:Q=0.065I1.342S0.513(1+H-0.227)(R2=0.756,N=43)。(3)研究了片沙覆蓋黃土沙土二元結構坡面產(chǎn)沙特征:不同條件下覆沙坡面產(chǎn)沙速率變化不同,薄覆沙坡面侵蝕過程產(chǎn)沙速率變化小,峰值不明顯,隨覆沙厚度增大,出現(xiàn)了垂直滲流-坡面潛流-崩塌-徑流沖刷的侵蝕過程,降雨過程中侵蝕速率變化較大,陡增陡降,具有明顯峰值。覆沙坡面侵蝕速率隨覆沙厚度、雨強、坡度的梯度增加整體上表現(xiàn)出遞增的趨勢。在小雨強下,覆沙坡面不易發(fā)生侵蝕,在大雨強下,覆沙坡面侵蝕速率劇增;覆沙坡面侵蝕速率變化存在臨界坡度,該坡度值在25°左右。相同坡度和雨強下,60min降雨內(nèi)覆沙坡面累計產(chǎn)沙量隨覆沙厚度的增大而增大,在較薄覆沙厚度時,增加較快,隨覆沙厚度的加厚,增加速率降低。相同降雨歷時下,覆沙坡面侵蝕量與覆沙厚度、雨強和坡度的偏相關系數(shù)分別0.532、0.599和0.342,雙側顯著性檢驗呈顯著。方差分析顯示雨強極顯著的影響產(chǎn)沙量變化,貢獻達30%;覆沙厚度變化顯著影響產(chǎn)沙量變化,貢獻率為14.24%;坡度對于產(chǎn)沙量變化的影響不顯著。次降雨產(chǎn)沙量與坡度、雨強、覆沙厚度的回歸方程為:M=0.005I1.204S0.801(1+H0.669)(R2=0.659,N=43)。(4)揭示了片沙覆蓋黃土沙土二元結構產(chǎn)流產(chǎn)沙關系:隨覆沙厚度、坡度和雨強的增加,降雨過程中產(chǎn)流速率和產(chǎn)沙速率變化的一致性增加。在薄覆沙、小雨強及低坡度下,產(chǎn)流后一定時間內(nèi)產(chǎn)流產(chǎn)沙的變化關系相對一致,即都呈增加趨勢,之后一般是產(chǎn)流速率相對穩(wěn)定,產(chǎn)沙速率呈減少趨勢;隨著覆沙厚度、坡度和雨強的增大,產(chǎn)沙速率和產(chǎn)流速率都出現(xiàn)先增大,之后達到峰值,之后再減少的趨勢,二者呈線性關系。對于60min降雨內(nèi),不同坡度、雨強產(chǎn)流和產(chǎn)沙速率具有很好的一致性,產(chǎn)流速率增大,產(chǎn)沙速率也增大,而對于不同覆沙厚度的坡面,產(chǎn)流量和產(chǎn)沙量呈相反的變化趨勢,產(chǎn)流量小而產(chǎn)沙量大,主要是因為在這種條件下覆沙厚度控制了徑流速率和產(chǎn)沙速率的變化所致。綜合分析發(fā)現(xiàn)徑流速率、坡度和覆沙厚度能夠表征坡面產(chǎn)沙速率的變化,得到M=0.249Q0.745S0.315(1+H0.799)回歸關系式,決定系數(shù)達0.926。(5)闡明了黃土坡面與片沙覆蓋黃土坡面產(chǎn)流產(chǎn)沙的差異:黃土坡面產(chǎn)流產(chǎn)沙過程相對平穩(wěn),降雨過程中產(chǎn)流速率先增大后穩(wěn)定,片沙覆蓋黃土坡面產(chǎn)流產(chǎn)沙過程隨不同的坡面條件差異顯著,產(chǎn)流產(chǎn)沙過程具有明顯單峰性,黃土坡面坡面降雨過程中坡面徑流速率一直小于降雨強度,沙土二元結構坡面在降雨過程中出現(xiàn)瞬時產(chǎn)流速率大于降雨強度,徑流系數(shù)大于1,甚至達到2以上的現(xiàn)象。在相同降雨歷時內(nèi),黃土坡面產(chǎn)流量大于片沙覆蓋黃土坡面,產(chǎn)沙量小于片沙覆蓋黃土坡面。片沙覆蓋黃土坡面在較薄覆沙時侵蝕過程與黃土坡面的侵蝕過程相似,而當覆沙厚度增大時,出現(xiàn)了垂直滲流-坡面潛流-崩塌-徑流沖刷的侵蝕過程,與黃土坡面侵蝕演化明顯不同。
[Abstract]:The water-erosion and wind-erosion cross-section in the Loess Plateau is the most severe area of soil erosion in the Loess Plateau and the main source area of the coarse sediment in the lower reaches of the Yellow River. In this paper, the difference of the physical and chemical properties of the lower-layer soil on the slope surface of the sandy soil is determined by the field investigation and sampling, on the basis of the field investigation and sampling, the different experimental combinations are designed based on the influence factors of the thickness of the sand, the rain intensity and the slope as the influencing factors. An artificial simulated rainfall observation experiment was carried out on the slope of the dual-structure sandy soil, and the characteristics of the sand-producing process on the surface of the sand-covered slope were studied, and the response characteristics of the sand on the surface of the sand-covered slope to different influencing factors were determined, the change law of the flow rate of the runoff and the coupling relation of the water and sediment were analyzed. The main results are as follows: (1) The difference of the physical and chemical properties of the two-dimensional structure of the sandy soil is explored: the soil structure, the soil bulk density, the particle composition, the porosity, the saturated hydraulic conductivity, the soil characteristic curve and the like of the sand layer and the yellow soil layer of the sandy soil binary structure are obvious, in particular to a particle composition, a saturated hydraulic conductivity and a water characteristic curve, Resulting in a special erosion process for such a slope. (2) The flow characteristics of the slope runoff at the two-dimensional structure of the sand-covered loess sandy soil are analyzed. The influence of different sand-coating thickness on the runoff rate of the slope is different. After the runoff is produced, the runoff rate tends to be quasi-stable after increasing with the rainfall in the surface of 0.5 cm and 2 cm, and the surface of the sand-covered slope is covered with 5 cm and 10 cm. according to the rainfall, the runoff rate of the sand-covered slope surface is gradually increased along with the rainfall, and the runoff rate of the sand-covered slope surface under different rainfall conditions is gradually increased with the change of the rainfall duration, and the fluctuation of the peak-to-peak fluctuation is decreased or rapidly decreased, With the increase of the rainfall, the change of runoff rate in the slope of the slope is increased; the flow rate of the surface runoff at the slope of different slopes is obviously different, the change trend of the runoff rate at the slope of 10 擄 and 15 擄 is close, the runoff rate is small, the flow rate of the runoff is increased slowly, and then the stability is stabilized; The change trend of the runoff rate of 20 擄 and 30 擄 slope is close to that of the 30 擄 slope. The peak value of the runoff is increased, and the change of the runoff rate of 25 擄 is the most special. The runoff rate is steep and steep, and the peak value is larger than the other slope. There is a negative correlation between the thickness of the sand and the accumulated runoff in 60 minutes of the secondary rainfall, and the rain intensity is positively correlated with the runoff, and the slope is positively correlated with the runoff of the runoff, and the critical slope is present at about 25 擄. The influence of the change of the rain on the production flow is the largest, the contribution rate is 64%, and the second is the thickness of the sand and the influence of the slope. The regression equation of runoff and slope, rain intensity and sand-covering thickness is Q = 0.065 I1.342 so.513 (1 + H-0.227) (R2 = 0.756, N = 43). (3) The characteristics of the sediment yield of the two-dimensional structure of the sand-covered loess sandy soil are studied: the change of the sand-producing rate of the sand-covered slope surface under different conditions is different, the change of the sand-producing rate during the erosion process of the thin sand-covered slope is small, the peak value is not obvious, and the thickness of the sand-covered slope is increased, The erosion process of the vertical seepage-surface undercurrent-collapse-runoff is developed, and the rate of erosion in the process of rainfall is large, the steep increase and steep drop, and the obvious peak value. The erosion rate of the sand-covered slope increases with the thickness of the sand, the rain is strong, and the gradient of the slope increases as a whole. Under the strong rain, the surface of the sand-covered slope is not easy to be eroded, and the erosion rate of the sand-covered slope is greatly increased when the heavy rain is strong, and the critical slope is present at the change of the erosion rate of the sand-covered slope, and the slope value is about 25 擄. In the same slope and rain, the accumulated sediment concentration in the sand-covered slope in the 60-min rainfall is increased with the increase of the thickness of the sand and sand, and at the time of the thinner sand-covering, the increase is faster, with the thickening of the thickness of the sand and sand, and the rate of increase is decreased. The correlation coefficient between the erosion amount of the sand-covered slope and the thickness of the sand-covered slope, the rainfall intensity and the slope was 0.532, 0.599 and 0.342 respectively under the same rainfall duration, and the two-sided significance test was significant. The analysis of variance showed that the rainfall intensity had a significant effect on the change of sediment yield, the contribution was up to 30%, the change of the thickness of the overlying sand significantly affected the change of the sediment yield, the contribution rate was 14.24%, and the influence of the slope on the change of the sediment yield was not significant. The regression equation of the sediment concentration and the slope, the rain intensity and the sand-covering thickness of the secondary rainfall is: M = 0.005 I1.204 so.801 (1 + H0.669) (R2 = 0.5659, N = 43). (4) The relationship between the runoff and sand production of the two-dimensional structure of the sand-covered loess sandy soil is revealed: the increase of the thickness of the sand-covered sand, the slope and the strong rain, the increase of the flow rate and the change of the sand-producing rate during the rainfall process. in that low slope of the thin sand, the small rain and the low slope, the change of the abortion sand in a certain time after the production flow is relatively consistent, that is, the flow rate is increase, and then the flow rate is generally relatively stable, and the sand production rate is reduced; and with the increase of the sand-coating thickness, the slope and the rain intensity, The rate of sand production and the rate of production flow are increased first, then the peak value is reached, and then the trend is reduced, and the two are linear. For 60-min rainfall, the rate of runoff and sediment yield of different slope, rain-strong runoff and sand-producing rate is very good, the flow rate of runoff is increased, and the sand production rate is also increased, and for the slope with different sand-covering thickness, the runoff and sediment yield are in the reverse direction, and the production flow is small and the sediment concentration is large. The main reason is that under this condition, the thickness of the sand is controlled by the change of the runoff rate and the sand production rate. It is found that the runoff rate, slope and sand-covered thickness can be used to characterize the change of runoff yield, and the regression relation of M = 0.249 Q0.745 so.315 (1 + H0.799) is obtained, and the coefficient of determination is 0.926. (5) The difference of the runoff and sand on the surface of the slope and the surface of the slope is clarified: the process of the runoff and sand production is relatively stable during the precipitation process, the flow rate in the process of rainfall is the first to increase, and the process of the sand-and-sand covering the surface of the slope surface is obviously different with the different slope conditions. The runoff rate of the slope is less than that of the rainfall intensity, and the runoff coefficient is more than 1 and even more than 2. During the same period of rainfall, the runoff of the slope surface is greater than that of the sand covered by the sand, and the sediment concentration is less than that of the sand covered by the sand. The erosion process is similar to the erosion process of the slope surface, and the erosion process of the vertical seepage-surface undercurrent-collapse-runoff is different when the thickness of the sand cover is increased.
【學位授予單位】：西北農(nóng)林科技大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：S157.1

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本文編號：2503137