基于土体特性和侵蚀过程的泥石流预警阈值实验研究

Wenchuan Earthquake strongly hit rock and soil so that the earth structure and physical and mechanical properties have a great change, resulting in debris flow initial critical conditions are very different from pre-earthquake, as a result, the pre-earthquake debris flow warning threshold is difficult to identity whether a debris flow occur or not during post-earthquake warning. Therefore，it is very important and essential to study debris flow warning threshold for Wenchuan earthquake influenced region. However, the debris flow disasters demonstrated that debris flow in seismic zones have significant differences in distribution, forming conditions, scales, moving styles as well as other disaster modes. Erosion and cutting was the mainly and typical initiating mode for the debris in earthquake hit region. In this study, experimental tests will be used to exploring the intiating process, mechanism of the erosion mode debris flow, and the correlation of debris supplement process and precipitation is revealed. Based on the initiation mechanism of debris flow and the mechanism of runoff yield and confluence, combine with the soil mechanism parameters of the debris source to determine the critical conditons of the debris transition and construct the calculation formula of warning threshold. This project is about to explore on the key scientific issues of the process, threshold for the erosion based mode debris flows reserve, which can contribute great significance for the disaster mitigation and reduction in Wenchuan earthquake regions.

汶川地震对岩土体的强烈扰动作用改变了泥石流源区土体结构和物理力学性质，造成泥石流启动临界条件发生改变，导致震前泥石流启动阈值不能准确预报震后泥石流事件。本项目拟针对震后大型崩滑体堆积区普遍出现的物源拉槽侵蚀破坏形成泥石流的过程，开展泥石流预警阈值研究。主要通过物理模型实验分析降雨激发条件下典型源区土体拉槽侵蚀启动的过程，探索泥石流启动、演化过程中主控要素的时空变化规律，揭示物源泥石流化过程与降雨激发条件的耦合关系，并结合土体物理力学性质和水理性质实验、产汇流理论及静态极限平衡原理分析，确定拉槽侵蚀型泥石流物源转化的临界条件，并建立定量预测泥石流启动的多参数预测模型，以期解决拉槽侵蚀型泥石流物源补给过程的临界条件和预警临界值计算的关键科学问题，为震后泥石流预警预报和风险评估提供技术支撑。

汶川地震对岩土体的强烈扰动作用改变了泥石流源区的土体结构和物理力学性质，造成泥石流启动临界条件发生改变，导致震前泥石流启动阈值不能准确预报震后泥石流事件。针对这一问题，本项目选择了都江堰银洞子泥石流沟为原型，开展了降雨激发条件下典型源区土体拉槽侵蚀和沟道冲刷形成泥石流的物理模型实验，探索了泥石流启动、演化过程中主控要素的时空变化规律，并建立了多因素泥石流阈值模型，以期解决拉槽侵蚀型泥石流物源补给过程的临界条件和预警临界值计算的关键科学问题，为震后泥石流预警预报和风险评估提供技术支撑。研究结果表明（1）体积含水量是宽级配土物理状态发生变化最敏感的参数，可以作为物源启动的控制性参数；（2）弄清了震区物源拉槽侵蚀失稳破坏的模式；（3）建立了IGM和IGD两种泥石流预警阈值。