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汶川地震触发的高速远程滑坡主要沿龙门山主中央断裂带汶川映秀—安县高川—北川县城—平武南坝—青川一线地震破裂带展布。由于获得了1.5g以上的抛掷加速度,具有明显的气垫效应,估计最大滑动速度一般大于70m.s-1,滑动距离一般为滑体启动时长度的数倍甚至10多倍,堆积成坝形成多处堰塞湖,最大滑行距离达3.2km。本文重点解剖了位于地震破裂带南西段(初始震中)的汶川映秀牛圈沟滑坡—碎屑流、位于地震破裂带中段的北川城西滑坡和位于地震破裂带北东段青川东河口滑坡—碎屑流3个典型实例,认为具有如下特征:(1)岩性条件:母岩遭受长期构造动力作用,呈碎裂岩体,后期被强烈风化,岩体极为破碎;(2)抛掷效应:位于汶川地震主断裂带或附近,垂直加速度大于水平加速度,强地面运动持时长,岩体发生振胀和抛掷;(3)碰撞效应:上部滑坡体发生高位剪出和高位撞击,致使岩体碎屑化;(4)铲刮效应:撞击作用导致下部山体被铲刮,形成次级滑坡,为碎屑流体提供了足够展翼和抛洒物源体积;(5)气垫效应:碎屑化岩体快速抛掷导致下部沟谷空气迅速谷状圈闭和向下紊流,形成气垫效应,或者,在下部地形开阔地带压缩空气呈层流状态致使滑体凌空飞行。
The high-speed remote landslide triggered by the Wenchuan earthquake is mainly distributed along the rupture zone of Wenchuan Yingxiu-Anxian Gaochuan-Beichuan County-Pingwu Nanba-Qingchuan first-line earthquake in the main central Longmenshan fault zone. Due to the above 1.5g throwing acceleration and obvious air cushion effect, the maximum sliding speed is estimated to be more than 70m.s-1. The sliding distance is usually several times or even 10 times of the length of the sliding body, Dammed Lake, the maximum taxiing distance of 3.2km. This paper focuses on the Wenchuan Yingxiu Niuquangou landslide-debris flow located in the southwestern segment of the earthquake rupture zone (initial epicenter), the Beichuan west-west landslide located in the middle of the earthquake rupture zone, and the landslide- (1) Lithology conditions: The mother rock suffered long-term tectonic dynamic and appeared as a cataclastic rock mass, the later was strongly weathered and the rock mass was extremely crushed. (2) Throwing effect: (3) Collision effect: the upper landslide body occurs high shear and high impact, resulting in the detritus of the rock mass ; (4) scraping effect: the impact caused by the impact of the lower mountain was scraped to form a secondary landslide, the debris flow enough wing and spatter source volume; (5) air cushion effect: rapid detritus crushed rock mass As a result, air in the valley of the lower part of the valley is swirled rapidly and turbulently downwards to form an air cushion effect. Or, the compressed air in the lower part of the terrain is laminar and causes the flying body to fly voluntarily.