贵州望谟“20110606”泥石流灾害成因及启动类型

2011年6月5-6日在最大降雨量105.9 mm/h的暴雨激发下,贵州望谟县内多个乡镇暴发泥石流灾害,造成37人死亡、15人失踪,灾害极其严重。为了解本次泥石流灾害的成因和启动类型,更好地提高泥石流预报和预警水平,在实地调查的基础上,分析了此次泥石流灾害的成因和启动类型。调查结果显示:(1)本次泥石流的集中暴发是地形地貌、物源和降雨等多因子耦合的必然结果,打破50年记录的降雨是本次泥石流暴发的主导因素,但陡峻的地形、砂岩等软岩强风化层也是引发泥石流灾害的重要原因;(2)沟床启动型、滑坡型、溃决性3种典型泥石流启动类型是调查区内主要启动类型,汇流作用下沟道侵蚀是沟床启动型泥石流的主要特征,前期降雨条件下坡体滑动提供物源是滑坡型泥石流的主要特征,堵塞沟道、在雨水作用下漫坝或溃坝最终增大泥石流流量是溃决型泥石流的主要特征。

Formation Mechanism of the “20110606” Debris Flows within Wangmo, Guizhou

The "20110606" rainstorm(105.9 mm/h)triggered many debris flows in Wangmo County,Guizhou Province.During the hazards,thirty-seven people were killed and fifteen people were lost,and many houses were seriously destroyed.In order to improve the result accuracy of the forecasting and early warning system,based on field investigation and analysis,this paper analysis formation and mechanism of debris flows.The results reveal the following aspects:(1)the tense outbreak of debris flow is an inevitable coupling result of topography,material sources and rainstorms,and the rainfall breaking the 50-year record is the main factor for the outbreak of those debris flows,but the steep terrain and soft rock layers,such as sandstones and shales etc.,are the important causes;(2) the formation mechanism of debris flows,including bed-failure-triggered debris flow,outburst-triggered debris flow and landslide-triggered debris flow were main types in this area,and the initiation of bed-failure-triggered debris flow was surface flow→erosion gradually→transformed into debris flow,and the initiation of outburst-triggered debris flow was collapse→block→burst→transformed into debris flow,the initiation of landslide-triggered debris flow was rainwater infiltration→failure→fluidization→transformed into debris flow.