金沙江沃达潜在滑坡诱发灾害链成灾过程数值模拟

Numerical Simulation of the Evolution Process of Disaster Chain Induced by Potential Landslide in Woda of Jinsha River Basin

滑坡诱发灾害链演化过程复杂,相比于单一滑坡灾害其危害性可通过时间和空间上的延拓得到极大增加,目前针对滑坡诱发灾害链演化动力特征的定量研究仍较为匮乏。为此,以滑坡堰塞湖溃决洪水灾害链为例,采用多物理模型耦合方法反映灾害链多物理过程特点,通过开展金沙江沃达滑坡诱发灾害链演化过程的预测模拟,定量评价了灾害链各阶段的动力特征,计算结果显示:滑坡起动后滑动速度高达38 m/s,入水后可诱发次生涌浪灾害,并在狭窄地形作用下最终堵塞河道,形成高69 m、长1.8 km的堰塞坝,滑坡影响范围可达2.1 km2,所形成的堰塞湖最大水深可达54 m;当堰塞湖水位超过坝顶高度时,发生漫顶溢流,进而引发漫顶溃决,可形成洪峰流量高达1.2×104 m3/s的溃坝洪水。此外,通过分析滑坡摩擦阻力系数和溃口侧面稳定系数两个关键因素变化对灾害链演化过程的影响,研究了灾害链各阶段之间的关联性。结果表明:滑坡摩擦系数变化不仅对滑坡运动的动力特征产生显著影响,还会影响后续所形成堰塞湖的特征,如水位高程及溃口位置等;坝体稳定性系数在影响滑坡坝溃决速度的同时,也会对后续溃决洪水的动力特征如峰值流量及最大流深等产生影响。由此可见灾害链阶段关联性是影响灾害链演化的重要因素。研究结果对滑坡诱发灾害链的防灾减灾具有重要支撑作用。

Landslide-induced disaster chain(LDC)has a complex evolution process,and distinguishing from the landslide disaster itself,the risk of LDC could be enhanced significantly by enlarging the scale in both space and time.Currently,the study on the quantitative analysis of the dynamic characteristics of landslide-induced disaster chain is still lack.Giving an example LDC,i.e.,the disaster chain of landslides-barrier lakesoutburst,a coupled model to reflect its multiple-physical processes was adopted.The evolution process of disaster chain which may be caused by Woda landslide located in Jinsha River basin was predicted and quantitative analyzed by numerical modeling.The calculation results indicate that the maximum of landslide velocity could reach 38 m/s and a landslide dam with a height of 69 m and a length of 1.8 km blocked the river course.The area influenced by landslide could reach 2.1 km2.Dambreak could be induced when the elevation of barrier lake exceeded that of the dam crest of landslide dam.A flood with a maximum flux of 1.15×104 m3/s originated from the barrier lake with a maximum depth of 54 m could be formed after dambreak.Furthermore,the relations between each stage of disaster chain were investigated by analyzing the effects of two key factors(the basal frictional coefficient and breach stability coefficient)on the evolution process of disaster chain.It was found that the change of basal frictional coefficient had a directly influence on the mobility of landslide and the characteristics of barrier lake such as water level and breach position.For breach stability coefficient,it affected the speed of dam break as well as the characteristics of flood such as maximum flux and flow depth.It demonstrated that the relation between each stage of disaster chain was a key factor influencing the evolution of disaster chain and should be considered.These results played a supporting role in the prevention and mitigation of LDC.