金沙江上游扎马古滑坡复活特征及堵河危险性分析

Resurgent characteristics of Zhama Landslide and river blocking risk analysis in the upper reaches of Jinsha River

随着人类工程活动不断加剧和极端天气的频繁出现,古滑坡复活堵江问题日益突出,严重威胁着山区城镇安全。以金沙江上游巴曲右岸扎马特大古滑坡为例,采用无人机航测、现场精细调查和数值模拟分析等方法,查明了古滑坡复活特征,剖析了不同重现期降雨条件下滑坡的稳定性和失稳概率,模拟研究了不同工况下滑坡运动过程、堆积范围及堵河危险性。结果表明:(1)扎马古滑坡前缘局部复活主要表现为地表变形迹象清晰,呈现牵引式渐进破坏的特点,前缘复活区体积约185万m^(3),存在进一步失稳滑动可能;(2)滑坡前缘在天然状态下稳定,20年一遇的月极值降雨条件下处于不稳定状态,失稳概率为87.95%,50年、100年一遇的月极值降雨条件下前缘与后部整体处于不稳定状态,失稳概率分别为58.75%、68.60%;(3)前缘失稳或前缘与后部连续失稳后,滑坡体在沟口处达到的最大速度分别为9、11 m s,滑移距离最远可达480 m,在巴曲沟道形成高度约42~48 m的堰塞坝;(4)堵塞巴曲后形成的回水可能淹没滑坡上游德达乡段G318国道、居民建筑及场站等基础设施,涉及范围约0.81~1.02 km^(2),形成的堰塞湖可能在7天内发生漫坝,应引起重视。

With the continuous intensification of human engineering activities and the frequent occurrence of extreme weather,the problem of ancient landslide resurrection and river blocking is becoming more and more prominent,which seriously threatens the safety of mountain towns.Taking the Zhama ancient landslide on the right bank of Baqu River in the upper reaches of Jinsha River as an example,using UAV aerial survey,field investigation and numerical simulation analysis,the characteristics of the resurrection of ancient landslide were identified,the deformation and failure range and instability probability of landslide under different rainfall conditions in different recurrence periods were analyzed,and the process of landslide movement,accumulation range and river blocking risk under different working conditions were simulated and studied.The results show that:(1)The local reactivation of the Zhama landslide front is mainly characterized by clear surface deformation signs and progressive tractive failure.The volume of the front reactivation area H 1 is about 185×10^(4)m^(3),with the possibility of further destabilizing sliding.(2)The front edge H 1 of the landslide is stable in its natural state,unstable under monthly extreme rainfall conditions that occur once every 20 years,with a probability of instability of 87.95%,under monthly extreme rainfall conditions that occur once every 50 years and 100 years,the front edge H 1 and rear H 2 are overall unstable,with probabilities of instability of 58.75%and 68.60%.(3)After the front H 1 is unstable,and the rear H 2 and H 1 are continuously unstable,the maximum velocity at the groove is 9 m s and 11 m s,respectively,and the slip distance is as far as 480 m.A barrier dam with a height of 42~48 m is formed in Baquu channel.(4)The backwater formed after the blockage of Baqu may inundate the G318 National Road,residential buildings and station and other infrastructure in Deda Township upstream of the landslide,covering an area of 0.81~1.02 km^(2).The dammed lake may overflow within 7 days,which requires high attention.