稀土元素定量监测坡面浅沟产生及发育过程
发布时间：2018-08-01 08:00
【摘要】：针对目前坡面浅沟侵蚀的产生及发育过程研究不足的现状,本论文以黄土为研究对象,在室内模拟降雨条件下采用稀土元素示踪技术,主要研究了坡面产流产沙过程,量化了坡面侵蚀形式的变化过程,分析了土壤类型和降雨动能对坡面侵蚀形式变化的影响以及瓦背型地貌浅沟侵蚀过程。所得的研究结果为浅沟侵蚀发生地区尤其是黄土高原地区坡耕地土壤侵蚀治理提供科学参考。主要研究结论如下:(1)研究了不同降雨强度、不同土壤类型和不同降雨动能条件下坡面产流和产沙过程。坡面产流率和产沙率均随着累积降雨量的增加呈现先增加后平稳波动的变化规律,部分实验最后阶段出现逐渐减小的趋势。降雨强度、土壤类型和降雨动能对坡面产流和产沙均具有较大影响。(2)量化了坡面侵蚀形式的变化过程。位于沟坡表面的Eu示踪层降雨初期开始出现产沙,随后在雨滴打击和径流共同作用下逐渐下切至其他各层。安塞黄绵土在405 mm降雨过程中十个示踪层(共50 cm)均先后出现明显产沙,而杨凌X土和长武黑垆土坡面最下面三层(每层各6 cm,共18 cm)一直未出现明显产沙。片蚀产沙量随着累积降雨量的增加呈现先增加再波动减小的变化趋势。其贡献率则呈现复杂变化,在降雨初期提供主要泥沙贡献,随后在细沟发育过程中逐渐减小至平稳阶段,并在浅沟出现后呈现进一步减小的变化趋势。细沟侵蚀产沙量随着累积降雨量的增加呈现先快速增加后波动稳定至浅沟侵蚀发生后略有减小,随后细沟产沙量持续增加至最大值后处于波动稳定后再减小的变化趋势。细沟在降雨初期贡献率较小,随后快速增加到较大值并处于稳定波动至浅沟出现后再逐渐减小至平稳波动。浅沟产沙量随着累积降雨量的增加呈现先增加后波动稳定至降雨结束,或先增加后波动稳定再减小的变化趋势。浅沟贡献率自出现后逐渐增加至稳定波动状态。根据三种侵蚀类型产沙贡献率的变化规律,将坡面侵蚀过程分为以下五个阶段:片蚀阶段(片蚀贡献率大于80%)、细沟发育阶段、细沟侵蚀稳定阶段(细沟贡献率大于70%、片蚀贡献率小于20%)、浅沟侵蚀发育阶段和浅沟侵蚀稳定阶段(浅沟贡献率50%-70%,细沟贡献率20%-40%,片蚀贡献率小于5%)。(3)分析了土壤类型和降雨动能对坡面侵蚀形式变化的影响。土壤类型和降雨动能对坡面侵蚀形式变化具有重要影响。不同土壤类型的团聚体稳定性差异较大,随着土壤团聚体稳定性的增加,除细沟发育阶段外,其他各阶段持续时间均随着团聚体稳定性的增加而增加。随着降雨动能的增加,对细沟发育阶段及细沟稳定阶段的沟道发育起促进作用,对浅沟发育阶段的影响较为复杂,在整体上促进沟道发育。侵蚀过程中0.002mm粒级和0.002-0.02 mm粒级富集明显。随着土壤团聚体稳定性增加,更多的0.002 mm粒级和0.002-0.02 mm粒级以0.05 mm粒级团聚体的形式搬运出坡面。降雨动能主要对片蚀阶段泥沙分选具有较大影响,而对其他侵蚀阶段泥沙分选影响不大。土壤类型和降雨动能均对沟宽具有影响较大,黄绵土坡面沟深最大,X土和黑垆土坡面沟深差别不大。整个降雨过程中,降雨动能对沟深的影响较小。(4)研究了瓦背型地貌浅沟侵蚀过程。瓦背型浅沟径流率均随着累积降雨量的增加存在着先快速增加后慢速增加再趋于波动稳定的变化趋势,而产沙率则呈现先增加后平稳波动再减小的趋势。沟坡部位产沙量随着累积降雨量的增加呈现先慢速增加后快速增加至最大值再波动减小的变化规律。沟坡部位产沙贡献率先处于稳定波动变化,随后逐渐增加至最大值再减小到较小值,随后稳定波动且略有减小。沟底部位产沙量随着累积降雨量的增加呈现先快速增加后慢速增加至最大值,之后出现稳定波动再逐渐减小的变化现象。沟底部位产沙贡献率先处于稳定波动变化,随后逐渐减小至最小值再增加达到较大值,而后稳定波动且略有增加。瓦背型地貌的在整个降雨过程中沟底部位产沙贡献率均大于沟坡部位产沙贡献率。随着累积降雨量的增加,沟坡部位和沟底部位产沙贡献率共出现了三个明显拐点,根据这三个拐点可以将瓦背型地貌浅沟侵蚀过程大致分为四个阶段:沟底沟道下切阶段;沟坡快速坍塌阶段;沟坡坍塌减缓阶段;沟道稳定阶段。
[Abstract]:In view of the present situation of insufficient research on the production and development process of shallow gully erosion on the slope, this paper takes loess as the research object. The process of runoff and sediment production on slope surface is mainly studied by using rare earth element tracing technique under indoor simulated rainfall conditions, and the change process of slope erosion form is quantified, and soil types and rainfall kinetic energy are analyzed on the slope surface. The influence of erosion form changes and the shallow gully erosion process of tile back landform. The results of the study provide scientific reference for soil erosion control in shallow gully erosion area, especially in the Loess Plateau area. The main conclusions are as follows: (1) the slope surface of different rainfall intensity, different soil type and different rainfall kinetic energy conditions are studied. The runoff yield and sediment yield in the process of runoff and sediment yield increase first and then the steady fluctuation with the increase of accumulated rainfall, and the trend of gradual decrease in the final stage of some experiments. The rainfall intensity, soil type and rainfall kinetic energy have great influence on the runoff yield and sediment yield on the slope. (2) the form of slope erosion is quantified. The Eu tracer layer on the surface of the ditch began to produce sediment, and then gradually cut down to the other layers under the joint action of raindrop and runoff. In the 405 mm rainfall process of Ansai yellow soil, ten tracer layers (a total of 50 cm) all had obvious sediment yield, while Yangling X soil and Changwu black soil slope surface at the bottom of the slope. There has been no obvious sediment yield in the 6 cm layer of each layer, and a total of 18 cm). The amount of sands yield increases first and then decreases with the increase of accumulated rainfall. Its contribution rate presents a complex change, which provides the main sediment contribution at the early stage of rainfall, and then decreases gradually to the smooth stage in the process of the development of the trench, and appears after the appearance of the shallow gully. As the cumulative rainfall increased, the sediment yield of the rill erosion first rapidly increased and then fluctuated to a slight decrease after the shallow gully erosion, and then the sediment yield increased to the maximum value and then decreased after the fluctuation. The contribution rate of the fine ditch at the early stage of the rainfall was smaller, and then fast. The variation trend of shallow gully yield increases first and then fluctuates to the end of rainfall, or increases first and then decreases. The contribution rate of shallow gully increases gradually to stable fluctuation state. The variation of the contribution rate of the three types of erosion is divided into five stages: the erosive stage (the slice erosion contribution rate is more than 80%), the rill development stage, the rill erosion stable stage (the rill contribution rate is greater than 70%, the slice erosion contribution rate is less than 20%), the shallow gully erosion development stage and the shallow gully erosion stable stage (the shallow ditch contribution rate 50%). -70%, the contribution rate of rill is 20%-40%, the contribution rate of sheet erosion is less than 5%). (3) the influence of soil type and rainfall kinetic energy on the change of slope erosion form is analyzed. Soil type and rainfall kinetic energy have an important influence on the change of slope erosion form. The duration of the other stages increased with the increase of the stability of the aggregate. With the increase of rainfall kinetic energy, the growth stage of the trench and the channel development of the rill stable stage were promoted, and the influence on the development stage of the shallow gully was more complex, and the channel development was promoted on the whole body. The 0.002mm grain level in the erosion process was improved. And 0.002-0.02 mm grain level enrichment is obvious. With the increase of soil aggregate stability, more 0.002 mm grain grade and 0.002-0.02 mm grain grade are transported out of slope surface with 0.05 mm particle aggregate. The rain kinetic energy has great influence on the furrow width, and the depth of the slope in the slope of the yellow cotton soil is the largest. The influence of the rainfall kinetic energy on the depth of the ditch is small in the whole rainfall process. (4) the shallow gully erosion process of the tile back topography is studied. The shallow gully flow rate of the tile back has a rapid increase with the increase of accumulated rainfall. The slow increase then tends to fluctuate and stable, while the sediment yield increases first and then decreases. Then gradually increase to the maximum value and then decrease to the smaller value, and then steady fluctuation and slightly decrease. The sediment yield at the bottom of the ditch shows a rapid increase and then slowly increase to the maximum value with the increase of cumulative rainfall, then the steady fluctuation then gradually decreases. In the whole rainfall process, the contribution rate of sediment yield in the bottom of the ditch is greater than that in the ditch. With the increase of accumulated rainfall, the contribution rate of sediment yield in the slope and the bottom of the ditch has three obvious inflection points. According to these three inflection points, the shallow gully erosion process of the tile back landform can be roughly divided into four stages: the undercut stage of the ditch bottom channel, the rapid collapse stage of the gully slope, the slow collapse stage of the gully slope and the stable stage of the channel.
【学位授予单位】：西北农林科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：S157.1
，
本文编号：2156832
[Abstract]:In view of the present situation of insufficient research on the production and development process of shallow gully erosion on the slope, this paper takes loess as the research object. The process of runoff and sediment production on slope surface is mainly studied by using rare earth element tracing technique under indoor simulated rainfall conditions, and the change process of slope erosion form is quantified, and soil types and rainfall kinetic energy are analyzed on the slope surface. The influence of erosion form changes and the shallow gully erosion process of tile back landform. The results of the study provide scientific reference for soil erosion control in shallow gully erosion area, especially in the Loess Plateau area. The main conclusions are as follows: (1) the slope surface of different rainfall intensity, different soil type and different rainfall kinetic energy conditions are studied. The runoff yield and sediment yield in the process of runoff and sediment yield increase first and then the steady fluctuation with the increase of accumulated rainfall, and the trend of gradual decrease in the final stage of some experiments. The rainfall intensity, soil type and rainfall kinetic energy have great influence on the runoff yield and sediment yield on the slope. (2) the form of slope erosion is quantified. The Eu tracer layer on the surface of the ditch began to produce sediment, and then gradually cut down to the other layers under the joint action of raindrop and runoff. In the 405 mm rainfall process of Ansai yellow soil, ten tracer layers (a total of 50 cm) all had obvious sediment yield, while Yangling X soil and Changwu black soil slope surface at the bottom of the slope. There has been no obvious sediment yield in the 6 cm layer of each layer, and a total of 18 cm). The amount of sands yield increases first and then decreases with the increase of accumulated rainfall. Its contribution rate presents a complex change, which provides the main sediment contribution at the early stage of rainfall, and then decreases gradually to the smooth stage in the process of the development of the trench, and appears after the appearance of the shallow gully. As the cumulative rainfall increased, the sediment yield of the rill erosion first rapidly increased and then fluctuated to a slight decrease after the shallow gully erosion, and then the sediment yield increased to the maximum value and then decreased after the fluctuation. The contribution rate of the fine ditch at the early stage of the rainfall was smaller, and then fast. The variation trend of shallow gully yield increases first and then fluctuates to the end of rainfall, or increases first and then decreases. The contribution rate of shallow gully increases gradually to stable fluctuation state. The variation of the contribution rate of the three types of erosion is divided into five stages: the erosive stage (the slice erosion contribution rate is more than 80%), the rill development stage, the rill erosion stable stage (the rill contribution rate is greater than 70%, the slice erosion contribution rate is less than 20%), the shallow gully erosion development stage and the shallow gully erosion stable stage (the shallow ditch contribution rate 50%). -70%, the contribution rate of rill is 20%-40%, the contribution rate of sheet erosion is less than 5%). (3) the influence of soil type and rainfall kinetic energy on the change of slope erosion form is analyzed. Soil type and rainfall kinetic energy have an important influence on the change of slope erosion form. The duration of the other stages increased with the increase of the stability of the aggregate. With the increase of rainfall kinetic energy, the growth stage of the trench and the channel development of the rill stable stage were promoted, and the influence on the development stage of the shallow gully was more complex, and the channel development was promoted on the whole body. The 0.002mm grain level in the erosion process was improved. And 0.002-0.02 mm grain level enrichment is obvious. With the increase of soil aggregate stability, more 0.002 mm grain grade and 0.002-0.02 mm grain grade are transported out of slope surface with 0.05 mm particle aggregate. The rain kinetic energy has great influence on the furrow width, and the depth of the slope in the slope of the yellow cotton soil is the largest. The influence of the rainfall kinetic energy on the depth of the ditch is small in the whole rainfall process. (4) the shallow gully erosion process of the tile back topography is studied. The shallow gully flow rate of the tile back has a rapid increase with the increase of accumulated rainfall. The slow increase then tends to fluctuate and stable, while the sediment yield increases first and then decreases. Then gradually increase to the maximum value and then decrease to the smaller value, and then steady fluctuation and slightly decrease. The sediment yield at the bottom of the ditch shows a rapid increase and then slowly increase to the maximum value with the increase of cumulative rainfall, then the steady fluctuation then gradually decreases. In the whole rainfall process, the contribution rate of sediment yield in the bottom of the ditch is greater than that in the ditch. With the increase of accumulated rainfall, the contribution rate of sediment yield in the slope and the bottom of the ditch has three obvious inflection points. According to these three inflection points, the shallow gully erosion process of the tile back landform can be roughly divided into four stages: the undercut stage of the ditch bottom channel, the rapid collapse stage of the gully slope, the slow collapse stage of the gully slope and the stable stage of the channel.
【学位授予单位】：西北农林科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：S157.1
，
本文编号：2156832
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