冰滑坡涌浪及其作用下的冰湖溃决机理研究

Glaciers in the mountain areas ablate quickly in response to the global warming. The glacier lake outburst flood (GLOF) caused by the surge waves, which are triggered by the glacier avalanches increases in recent years. This kind of hazards pose serious threats to the local people's life and property and the national major projects such as the hydropower projects along Yarlung Zangbo River, Sichuan-Tibet railway, and Sichuan-Tibet expressway.Based on the GLOF hazard mitigation requirement,the typical GLOF cases will be chosen as the study objects in the southeast of Tibet autonomous region in this project. Some important basic data related to dynamic evolution process of surge waves triggered by glacier avalanches and the GLOF will be obtained based on the remote sensing interpretation and field investigation. By combining the physical modeling experiments,theoretical analysis, and numerical simulation, the dynamic evolution process of surge wave: formation-propagation-attenuation will be analyzed. The prediction model for initial height of surge waves will be established. The initialization condition and transportation rate of moraine dam materials will be revealed under the influence of surge waves. The failure mechanism and process of moraine dams will be investigated. Predicting model for the peak discharge of GLOF under the effects of surge waves will also be put forward in this project. Investigation on surge wave dynamic evolution process and its effect on the moraine dam failure mechanism will provide scientific and technological support to the GLOF risk assessment and hazard mitigation.

在全球气候暖化的环境背景下，高寒山区冰川急剧消融，冰滑坡涌浪作用诱发的冰湖溃决灾害不断增加，严重威胁着当地人民群众的生命财产和国家重大工程安全（如雅鲁藏布江梯级水电工程、川藏铁路、川藏高速）。针对冰湖溃决减灾需求，本项目拟选择西藏东南地区典型冰湖溃决案例，通过遥感解译与野外考察，获得冰滑坡涌浪-冰湖溃决动力演化过程中重要的基础数据；结合室内模型实验、理论分析与数值模拟，研究冰滑坡作用下涌浪形成-演进-衰减动力过程，构建冰滑坡涌浪初始高度预测模型；揭示冰滑坡涌浪作用下坝体物质的起动与输移规律，研究涌浪作用下冰碛坝溃决过程与机理，构建冰湖溃决峰值流量计算模型，为科学评估高寒山区冰湖溃决风险，合理制定溃决洪水减灾方案提供理论支撑。

在全球气候暖化大环境背景下，高寒山区冰川急剧消融，冰滑坡涌浪作用下诱发的冰湖溃决灾害不断增加，严重威胁当地民众的生命财产安全和国家重大工程布局(高山峡谷区水电工程、川藏铁路、川藏高速公路、滇藏铁路等)。针对冰湖溃决风险减灾实际需求，本项目通过开展系统的资料收集整理、野外考察、实验研究，以及数值模拟等，研究了冰滑坡入水过程中涌浪形成-演进-衰减动力过程与机制，分析了冰碛坝稳定性，构建了溃决洪水峰值流量计算模型，主要结论如下：.1）冰滑坡快速入湖激发涌浪，涌浪高度与滑块体积、滑动角度、入水速度呈正相关关系，与水深呈负相关关系，基于无量纲参数，构建了涌浪高度计算模型，运用该模型对米堆沟冰湖涌浪高度进行了预估，计算结果与现场测量值吻合良好。.2）涌浪演进过程中，涌浪高度在距滑块入水点X/h0=1附近涌浪高度最大，随后高度呈指数衰减，当距离X/h0>1.5时，浪涌高度衰减速率明显低于冰滑块刚入水激起涌浪的衰减速率，且呈现出类似于正弦波（余弦波）周期变化，距离入水点越远，涌浪周期性变化规律越明显。.3）考虑冰滑坡涌浪作用力对冰碛坝整体稳定性的影响，基于极限平衡理论，建立了冰碛坝稳定性判识模型：当SF<1.0时，表明坝体所承受的外荷载超过了坝体的抵抗力，坝体存在整体向下游滑动的溃决风险；当SF>1.0时，表明坝体所承受的外荷载小于坝体自身的抵抗力，坝体难以发生向下游的整体滑动，整体溃决的风险很低。在些基础上，对坝体颗粒受力条件进行了分析，提出了坝体颗粒起动临界条件。.4）引入土体颗粒标度分布作为冰碛坝峰值流量参数，利用模型实验研究了涌浪作用下冰碛坝的溃决机理，建立了涌浪作用下冰碛坝溃决峰值流量计算模型，并与实验数据进行比较。结果表明：计算值与实验测量结果吻合良好，相关系数R2=0.93。