高山峡谷区域暴雨泥石流成灾临界阈值研究

Enhancing the research on the critical threshold value of regional rainstorm-induced debris flows is the basis for studies on early-warning and forecasting of debris flows in mountainous areas, and the difficult point of and the key to mitigating and preventing debris flow disasters, too. With three typical debris flow ditch in Zhouqu as the subject of this study, and based on field survey and data collection, the experiments such as in-situ testing, geotechncial testing and numerical simulation and a large number of real-time monitoring data were done. Moisture content variation law of space and time were quantitatively analyzed in the process debris flow with various condition. The threshold values and critical initiation conditions of disaster-forming environmental factors of various kinds of debris flows in variable scales were elaborated, and a system of critical indexes was established for induction of debris flows by rainstorm in mountainous areas. The hydrodynamic conditions for debris flow occurring was studied in depth, the influential of the runoff and runoff depth and sediment on the process of debris flow were quantitatively analyzed, the TOPOFLOW model systematically reveal the runoff sediment effect on the debris flow initiation, formation and movement mechanisms on different underlying surface conditions. The research result can provide scientific bases for regulation decision-making, early warning and forecasting of regional rainstorm-induced debris flow disasters.

深化区域暴雨泥石流临界阈值研究是山区泥石流预警预报研究的基础，也是减轻和防治泥石流灾害的难点和关键所在。本课题以舟曲3处典型泥石流沟为研究对象，从野外勘察、资料收集入手，通过原位测试、土工试验和数值模拟等方法，结合大量实时监测数据，定量阐明不同地质环境条件、不同下垫面情况下，泥石流在启动、运动过程中含水率的时空变化规律，揭示位移、流速、泥位和坝体应力对降雨的动态响应机制；进一步细化降雨特征指标，揭示不同地质环境条件下，激发区域暴雨泥石各降雨指标的函数关系，临界雨量（激发雨型、激发雨强）特征规律，确定激发泥石流启动的降雨临界阈值；分析泥石流启动的临界径流量、径流深，径流流速临界条件和水流含沙量对泥石流启动的影响，揭示不同下垫面情况下降雨转化为峰值流量规律、侵蚀产沙对泥石流启动的作用机制。为我国山区泥石流灾害防治奠定基础，为区域暴雨泥石流灾害调控决策、预警预报提供科学依据。

本研究首先以舟曲区域以及三眼峪、罗家峪、寨子沟为研究对象，总结、归纳并梳理以往研究成果，系统研究舟曲“8.8”特大山洪泥石流地质灾害的成灾模式、致灾因素，并提出舟曲地质灾害监测预警方案和风险减缓措施。.其次，通过有限差分数值模拟方法，分析三眼峪小流域位移场、应力场以及塑性区分布规律，阐明三眼峪重力侵蚀发生的空间分异特征及发生机理。采用有限元求解方法，开发三维连续介质模型程序，建立舟曲高速远程滑坡及泥石流的三维动态动力分析模型。开展泥石流和高速远程滑坡的临界启动研究，运动侵蚀行为及冲淤特征研究，灾害体动力过程研究，流变参数敏感性研究以及拦挡坝对泥石流、滑坡拦挡动力行为研究，系统揭示舟曲泥石流与高速远程滑坡形成机理。.最后，采用水文学分析方法，计算不同降雨频率下洪水特征值与降雨特征值，划分地质灾害不同预警级别，提出预警判据，计算不同预警级别下的降雨特征阈值，建立前期含水量在一般和干旱两种条件下，不同预警级别的降雨历时与降雨雨强函数关系曲线，阐明触发不同等级地质灾害的临界降雨特征。在此基础上，开展不同预警级别下区域地质灾害危险性区划研究，分析不同预警级别下，地形湿度指数空间分布、灾害点分布范围变化趋势及规律，稳定区、潜在不稳定区域与不稳定区域的区域面积比例与所占滑坡的比例迁移与转化规律，揭示区域地质灾害不同预警级别下危险性区划分布规律，建立舟曲区域地质灾害预警模型；同时针对舟曲已经布设的监测仪器，建立不同预警级别下，不同监测指标的预警阈值信息，以期为舟曲区域乃至高山峡谷区地质灾害危险性区划以及监测预警提供科学依据。