融水作用下冰碛土体失稳转化为冰川泥石流的力学机理

This research focuses on the mechanism of melting water triggering failure and debris flow initiation from moraine with large porosity and frame structure. By analyzing the composition and structure of moraine，the slope and the stream discharge in the watershed where there are times of glacier debris flows in history, the parameter of debris flow initiation experiment is made.In the research, experiments on debris flow initiation from melting water seeping in Parlung Zangbo basin will be carried out. We pay attention to the fluctuation of surface runoff, subsurface runoff, pore pressure, soil moisture during the initiation process, and the deris flow density, viscous resistance and its erosion process. Based on the changing of soil strength, the Mohr-Coulomb model is applied to reveal the failure process, the contraction effect of soil mass during failure process is conducted by the study of changing density of soil mass; later, the pore water pressure and the liquefactio model of gravel soil are combined to study the mechnism of soil mass liquefaction and debris flows initiation; in the end, the fluid dynamics model is adopted based on the decline of dynamic resistance to disclose debris flows enlargement by entraining along the path way. On the whole, debris flows triggering mechanism would be concluded into contraction, failure, liquefaction and entraniment.

项目研究冰雪融水作用下大孔隙、架状结构冰碛土体失稳产生泥石流的力学机理。项目通过研究冰川泥石流多发区冰碛土体的组成与结构特征，确定泥石流启动实验的土体特征指标；通过对藏东南帕隆藏布流域典型冰川泥石流灾害事件的调查，确定冰川泥石流启动的坡度与径流指标，进行融水渗透引起冰碛土体失稳转化为泥石流的实验，研究冰碛土体启动产流过程中的径流、渗流、孔压、含水量与泥石流容重、粘滞阻力与侵蚀特征的变化；基于土体强度的变化，采用库伦模型揭示土体剪切的机理，基于土体容重分析剪缩模型揭示土体剪切破坏过程的收缩机理；基于孔压变化特征，应用粗粒土的液化模型揭示土体液化转化为泥石流机理；基于动态阻力的降低应用流体力学模型揭示泥石流的铲蚀机理。揭示泥石流起动过程中的“收缩、剪切、液化和铲蚀”机理。

项目采用资料搜集与分析、现场调查、室外泥石流起动实验、室内模型实验等方法研究了冰碛土体形成泥石流的地貌和水文特征指标、泥石流易发区冰碛土体的组成结构和强度特征、特征径流作用下冰碛土体性质的变化和冰碛土体起动泥石流的力学机理。. 查明了藏东南帕隆藏布流域冰碛土体的类型及其地形地貌特征，起动泥石流的水文参数特征，发现高陡松散冰碛土体起动冰川泥石流的坡度和径流特征；研究了帕隆藏布冰川泥石流易发区松散冰碛土体的组成结构和强度特征差异，研究衡量低粘粒冰碛土体的组成和结构的分形分维综合指标，确定易发泥石流冰碛土体的分形特征；明确了冰川融水渗流作用下代表性松散冰碛土体的密度、含水量与渗透率的变化特征；揭示了冰川融水渗流导致冰碛土体强度衰减的力学条件和机理，提出了一种冰碛台地区的泥石流防治模式；并对冰湖溃决型泥石流进行了危险性评估。. 项目总体按研究计划执行，并超额完成研究目标。项目执行期间共获奖4项；发表论文18篇，其中SCI论文12篇，核心期刊论文6篇；出版研究专著1部；撰写的6份咨询报告获国家领导人和西藏自治区领导批示。