【作者】 李飞；

【导师】 张茂省；

【作者基本信息】 西北大学 ， 地质工程， 2018， 硕士

【副题名】以吉县幅为例

【摘要】 黄土沟谷系统自动化分级对于认识黄土高原沉积侵蚀演化历史、地质灾害发育规律和发生机理具有重要的科学和现实意义。本研究以吉县幅黄土沟谷地貌为研究对象,开展了黄土沟谷系统划分和特征的研究工作,取得的主要成果如下:(1)基于地表径流模型和Strahler河道分级原理建立了地表水运动模型,模拟了实际流水在1:5万DEM栅格数据表面的动态运动过程,实现了吉县幅黄土沟谷系统自动化分级,确定了沟谷提取及沟道分级最优精度的汇流累积阈值(X=10),其结果与实际调查沟谷类型相吻合。(2)结合文献调研法和野外调查法从沟谷形态、几何特征和分布规律等方面对沟谷特征进行了研究,总结了坡面侵蚀沟、冲沟、干沟和河沟的从“沟头-沟中-沟口”和“沟缘-沟坡-沟底”等发育特征,揭示了沟谷不同发育部位多级形成阶段下的动态演化规律,并探讨了黄土地区塬梁峁不同地貌单元与沟谷发育的伴生关系。(3)基于流域侵蚀动力学理论研究了沟谷系统演化机制,揭示了沟道流水对沟坡地和沟底地的侵蚀搬运过程及模式,提出了沟谷系统发育过程物理力学概化模型及稳定性计算简化模式,结合不同发育阶段、沟谷不同部位的侵蚀过程和稳定性,构建了完整的沟谷系统演化过程。(4)根据沟谷系统的演化机制,结合沟谷系统发育过程中的沟坡稳定性问题和地质灾害的变形破坏模式,探讨了不同发育阶段沟谷的致灾效应,研究发现不同级别沟谷发育的地质灾害类型不同。坡面侵蚀沟以坡面泥流、小型滑塌为主,冲沟易发生小型滑塌、崩塌,且威胁对象较小,干沟易发生中小型滑坡,灾点密度较大,而河沟处于相对稳定期,人类活动强烈且诱发地质灾害较多;且在支沟交汇位置处地质灾害(崩滑流)频发且具有群发性特点,多沿沟谷两侧呈条带状展布,发育于斜坡中下部高陡直立面。更多还原

【Abstract】 The automatic classification of the loess valley system has important scientific and practical significance for the history of the evolution of sedimentary erosion on the Loess Plateau,the development regularity and the occurrence mechanism of geological disasters.The study took the loess valley landform of the sheets of Ji Xian County as the research object,and carried out the research of loess valley system division and characteristics.The main achievements were as follows.(1)The surface water movement model was established based on the rainfall runoff model and the Strahler Channel Classification Principle.The study simulated the dynamic movement process of the actual water flow on the 1:50000 DEM grid data surface and realized the automatic classification of the loess valley system in the sheets of Ji Xian County.The cumulative threshold(X=10)of the best convergence accuracy of the channel classification and valley extraction was determined,which was consistent with the actual survey valley type.(2)On the basis of the valley characteristics research from the aspects of vally morphology,distribution patterns and geometric characteristics combined with literature survey and field investigation,the study summarized the features and developmental mechanism of V-shaped,sharp U-shaped and U-shaped valley section of slope erosion valley,alluvial valley,dry valley and river valley,and discussed the dynamic evolution regularity of different parts of the valley(valley head-slope surface-valley bottom)on the multistage forming stage and associated relations of the development of different geomorphic units and valleys in the loess plateau.(3)Based on the theory of basin erosion dynamics,the study discussed the evolution mechanism of the valley system and the erosion process and stability of the valleys at different times and in different locations,and revealed the erosion transport process and model of channel flow on the valley slope and the valley ground.Meanwhile,the physical and mechanical generalization model of the valley system development process and the simplified model for stability calculation were proposed,and the complete evolution process of the valley system was constructed.(4)The types of geological disasters at different levels of valley development are different based on the geological disasters effects study of the valley system development of Ji Xian County sheets.The slope erosion trenches are dominated by slope mudslides and small slumps.Geological disasters(collapsing flow)occur frequently at the alluvial valleys intersectionsd,characterized by clustering;Small and medium-sized landslides are prone to occur at dry valleys,while the river valleys are in a relatively stable period with less geological disasters.更多还原