基于RAMMS的冰湖溃决型泥石流演进模拟及危害性

Evolution Process Simulation and Hazard Research of Debris Flow Induced by Glacier Lake Outburst Based on RAMMS

冰湖溃决型泥石流作为目前西藏境内最主要的地质灾害之一,对下游工程的建设与运营造成潜在威胁。以西藏洛隆县冻错曲冰湖为例,基于现场调查、遥感解译、特征值计算和数值模拟方法,对冻错曲冰湖泥石流孕灾条件、动力学特征及溃决演进过程进行研究,分析其对下游工程建设的影响。采用无量纲堵塞指数(dimensionless blockage index,DBI)方法对冻错曲冰湖堰塞体稳定性进行评价,结果表明该堰塞体位于非稳定区与稳定区之间,存在发生溃决的风险。基于三维动态模拟软件RAMMS的Voellmy-Salm单相流模型,模拟分析了冻错曲冰湖泥石流在2种溃决模式下的演进过程。模拟结果显示:冻错曲冰湖泥石流溃决演进过程可归纳为初始溃决、加速运动、减速运动、沟口停淤4个阶段;2种溃决模式下冰湖溃决影响范围都经过拟建工程位置,潜在威胁区泥石流平均深度分别为4.87 m和8.26 m;在瞬时全部溃决场景下,冰湖溃决泥石流在拟建工程处最大流速为5.74 m/s,最大流量为2843.38 m^(3)/s。研究成果有助于评价冰湖溃决型泥石流的危害性,并为工程防治设计提供参考。

Glacier lake outburst debris flow,as one of the most primary geohazards in Tibet,poses a potential threat to the construction and operation of infrastructures.Based on field investigation,remote sensing interpretation,eigenvalue calculation and numerical simulation,the Dongcuoqu glacier lake in Luolong County,Tibet was introduced to study the predisposing conditions,kinetic characteristics and outburst evolution process of the Dongcuoqu glacier lake outburst debris flow,and to further evaluate its impacts on the downstream constructions.The dimensionless blockage index(DBI)method was used to evaluate the stability of the barrier dam of the Dongcuoqu glacier lake.The results show that the barrier dam is located in the critical zone between the unstable and the stable zone,presenting the probability of outburst.On the basis of the Voellmy-Salm single-phase fluid model of three-dimensional dynamic simulation software RAMMS,the evolution process of the Dongcuoqu glacier lake debris flow is simulated and analyzed under two different outburst modes.The simulation results demonstrate that the evolution process of glacier lake outburst can be divided into four stages:initial outburst,accelerated movement,decelerated movement,cessation and deposition.The influence ranges of glacier lake outburst both pass through the proposed construction site under the two outburst modes,and the average depth of debris flow in the potential threat area is 4.87 m and 8.26 m respectively.In the scenario of instantaneous complete outburst,the maximum flow velocity of glacier lake outburst debris flow at the proposed construction site is 5.74 m/s,with the maximum peak flow of 2843.38 m^(3)/s.The simulation results contribute to evaluate the hazard of glacier lake outburst debris flows and could serve as a preference for prevention and control engineering design of construction.