2008年5·12四川汶川里氏8级地震,引发了大量崩塌滑坡.安县高川乡的大光包滑坡是规模最大的高山滑坡,总方量约10×109m3.它的形成机制和运动学特征引起国内外学者的广泛关注.在前人调查研究的基础上,本课题组对滑坡的外形和结构特征及其所处地质环境作了较详细地现场调查,系统研究了滑坡的形成和演化过程,开展了室内实验及震动台物理模拟实验,通过与类似地区地质现象的对比分析,对滑坡获得以下认识:(1)大光包滑坡是一个巨型的楔型槽状滑落体,以下伏的震旦系白云岩层面为主滑面,以与层面近于正交的早期X构造裂隙面为侧滑面,两控制面交线倾向北北东,倾角12.左右；(2)滑坡前缘的黄洞子沟是滑坡的剪出口位置,滑坡起动加速滑入黄洞子沟后受到沟道左侧山梁的阻挡而迅速制动,受阻的滑坡体上部高速越过山梁冲向山坡并发展为碎屑流；(3)作为滑坡主滑面的震旦系白云岩岩层,为一经历了强烈岩溶的白云岩沙化层,强烈地震引发沙化层因突然产生的超空隙压力而流态化,这可能是导致山体突然失稳的主要原因.大光包滑坡事件可能为我们提供了地震引发山体失稳的一种新的模式,在分析研究和评价山坡的演化和稳定性时具有重要意义.%The Wenchuan M8.0 earthquake on May 12, 2008 caused thousands of rock falls and landslides. The Daguangbao landslide in Anxian County is the largest landslide site. Its failed slope volume is up to 1 billion m3 . Its formation mechanism and kinematics attract a wide attention of scholars at domestic and abroad. Based on a series urvey of the landslide field measurement and laboratory experiments, this paper presents some new understandings of the landslide as follows. (1) the landslide is a wedge and trough shaped fall. The bottom Sinianperiod dolomitite layer functioned as the main surface of rupture. The early X-tectonic fractures that orthogonal to the layer functioned as a side surface of rupture. The intersection line of two control planes tends to 64°with dip angle 12°. (2) the Huangdongzi valley in front of landslide is the outlet of the surface rupture. The landslide rapidly slipped into the valley. The moving mass was obstructed and braked by the valley slope on its left side. The upper part of landslide mass passed over the left valley slope and developed a debris flow. (3)the rupture plan of the landslide is along a layer of Sinian dolomite rock mass. It experienced strong karstification and became a band layer of sand-soil. This sand-soil layer during the strong vibration changed its performance caused by the suddenly increase of excess pore pressure. Even then, it developed into a fluidal structure layer. This may be the main formation mechanism of this huge landslide. Daguangbao landslide may be the new model of mountain collapse that caused by earthquake. The research on the analysis of the evolution and the stability of the slope has an important meaning.
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