片沙覆盖黄土区沙土二元结构坡面侵蚀过程研究
发布时间：2019-06-20 10:09
【摘要】：黄土高原水蚀风蚀交错带是黄土高原土壤侵蚀最为剧烈的区域及黄河下游河床粗泥沙的主要源区,该区域内有特殊的片沙覆盖黄土地貌,存在片沙在上黄土在下的沙土二元结构坡面。本论文以此沙土二元结构坡面为研究对象,通过野外调查采样,确定沙土二元结构坡面上下层土壤理化性质的差异,在此基础上,以覆沙厚度、雨强和坡度为影响因子,设计不同的实验组合,对沙土二元结构坡面进行人工模拟降雨观测实验,研究覆沙坡面的产流产沙过程特征,确定覆沙坡面产流产沙对不同影响因子的响应特征,分析坡面径流流速变化规律及水沙耦合关系等,得到以下主要结果:(1)探索了片沙覆盖坡面沙土二元结构剖面理化性质的差异:沙土二元结构剖面沙层和黄土层的土壤结构、土壤容重、颗粒组成、孔隙度、饱和导水率、土壤特征曲线等都差异明显,尤其是颗粒组成、饱和导水率和水分特征曲线,土壤特性在上下层的较大差异,为沙土二元结构坡面特殊的水分入渗、产汇流、土壤侵蚀、物质运移等过程奠定了基础,导致这种坡面可能发生特殊的侵蚀过程。(2)分析了片沙覆盖黄土沙土二元结构坡面产流特征:不同覆沙厚度对坡面径流速率的影响不同,产流后,径流速率在0.5cm和2cm覆沙坡面时随降雨进行先递增后趋于准稳定状态,在5cm和10cm覆沙坡面,随降雨进行先快速增加,然后又缓慢降低,在15~25cm覆沙坡面径流速率随降雨进行陡增陡降;不同雨强条件下覆沙坡面径流速率随降雨历时变化的整体趋势是先递增,到达峰值后波动递减或快速递减,随雨强增大,坡面产流速率变化加剧;不同坡度下覆沙坡面产流速率有明显差异,10°、15°坡面径流速率的变化趋势接近,径流速率小,产流后缓慢递增,之后趋于稳定;20°、30°坡面径流速率变化趋势接近,先增大,到达峰值后开始减小;25°径流速率变化最为特别,径流速率陡增陡减,其峰值比其他坡度都都大。次降雨60min内,覆沙厚度与累计产流量成极显著负相关,雨强与径流量呈极显著正相关,坡度与径流量成极显著正相关且在25°左右存在临界坡度。雨强变化对产流量的影响最大,贡献率达64%,其次为覆沙厚度,坡度的影响最小。径流量与坡度、雨强、覆沙厚度的回归方程为:Q=0.065I1.342S0.513(1+H-0.227)(R2=0.756,N=43)。(3)研究了片沙覆盖黄土沙土二元结构坡面产沙特征:不同条件下覆沙坡面产沙速率变化不同,薄覆沙坡面侵蚀过程产沙速率变化小,峰值不明显,随覆沙厚度增大,出现了垂直渗流-坡面潜流-崩塌-径流冲刷的侵蚀过程,降雨过程中侵蚀速率变化较大,陡增陡降,具有明显峰值。覆沙坡面侵蚀速率随覆沙厚度、雨强、坡度的梯度增加整体上表现出递增的趋势。在小雨强下,覆沙坡面不易发生侵蚀,在大雨强下,覆沙坡面侵蚀速率剧增;覆沙坡面侵蚀速率变化存在临界坡度,该坡度值在25°左右。相同坡度和雨强下,60min降雨内覆沙坡面累计产沙量随覆沙厚度的增大而增大,在较薄覆沙厚度时,增加较快,随覆沙厚度的加厚,增加速率降低。相同降雨历时下,覆沙坡面侵蚀量与覆沙厚度、雨强和坡度的偏相关系数分别0.532、0.599和0.342,双侧显著性检验呈显著。方差分析显示雨强极显著的影响产沙量变化,贡献达30%;覆沙厚度变化显著影响产沙量变化,贡献率为14.24%;坡度对于产沙量变化的影响不显著。次降雨产沙量与坡度、雨强、覆沙厚度的回归方程为:M=0.005I1.204S0.801(1+H0.669)(R2=0.659,N=43)。(4)揭示了片沙覆盖黄土沙土二元结构产流产沙关系:随覆沙厚度、坡度和雨强的增加,降雨过程中产流速率和产沙速率变化的一致性增加。在薄覆沙、小雨强及低坡度下,产流后一定时间内产流产沙的变化关系相对一致,即都呈增加趋势,之后一般是产流速率相对稳定,产沙速率呈减少趋势;随着覆沙厚度、坡度和雨强的增大,产沙速率和产流速率都出现先增大,之后达到峰值,之后再减少的趋势,二者呈线性关系。对于60min降雨内,不同坡度、雨强产流和产沙速率具有很好的一致性,产流速率增大,产沙速率也增大,而对于不同覆沙厚度的坡面,产流量和产沙量呈相反的变化趋势,产流量小而产沙量大,主要是因为在这种条件下覆沙厚度控制了径流速率和产沙速率的变化所致。综合分析发现径流速率、坡度和覆沙厚度能够表征坡面产沙速率的变化,得到M=0.249Q0.745S0.315(1+H0.799)回归关系式,决定系数达0.926。(5)阐明了黄土坡面与片沙覆盖黄土坡面产流产沙的差异:黄土坡面产流产沙过程相对平稳,降雨过程中产流速率先增大后稳定,片沙覆盖黄土坡面产流产沙过程随不同的坡面条件差异显著,产流产沙过程具有明显单峰性,黄土坡面坡面降雨过程中坡面径流速率一直小于降雨强度,沙土二元结构坡面在降雨过程中出现瞬时产流速率大于降雨强度,径流系数大于1,甚至达到2以上的现象。在相同降雨历时内,黄土坡面产流量大于片沙覆盖黄土坡面,产沙量小于片沙覆盖黄土坡面。片沙覆盖黄土坡面在较薄覆沙时侵蚀过程与黄土坡面的侵蚀过程相似,而当覆沙厚度增大时,出现了垂直渗流-坡面潜流-崩塌-径流冲刷的侵蚀过程,与黄土坡面侵蚀演化明显不同。
[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 掳 and 15 掳 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 掳 and 30 掳 slope is close to that of the 30 掳 slope. The peak value of the runoff is increased, and the change of the runoff rate of 25 掳 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 掳. 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 掳. 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.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S157.1
本文编号：2503137
[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 掳 and 15 掳 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 掳 and 30 掳 slope is close to that of the 30 掳 slope. The peak value of the runoff is increased, and the change of the runoff rate of 25 掳 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 掳. 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 掳. 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.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S157.1
【参考文献】
相关期刊论文 前1条
1 许炯心;黄河中游支流悬移质粒度与含沙量、流量间的复杂关系[J];地理研究;2003年01期
，本文编号：2503137
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