BASIC CHARACTERISTICS AND FORMATION MECHANISM OF THE LARGEST SCALE LANDSLIDE AT DAGUNGBAO OCCURRED DURING THE WENCHUAN EARTHQUAKE
BASIC CHARACTERISTICS AND FORMATION MECHANISM OF THE LARGEST SCALE LANDSLIDE AT DAGUNGBAO OCCURRED DURING THE WENCHUAN EARTHQUAKE
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发表时间：
2008
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通讯作者：
Liu Tianbin
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作者：
Liu Tianbin
大广堡和红洞子沟滑坡是汶川地震中规模最大的滑坡，其体积达7.42亿m3，泥石流坝高达690 m，是我国地震诱发的规模最大的滑坡。拥有中国最高的滑坡泥石流坝，更是世界上已知的少数超大型滑坡之一，滑坡位于发震断裂上盘，距映秀地震触发断裂近7 km，滑坡体的堆积物北川断裂带的斜坡在三面削坡前是一个孤立的山脊Earthquake.it，其高差达1500 m，斜坡的走向几乎垂直于坡面，斜坡的伸展性很好，它们共同构成了滑动面形成的基本条件。调查分析表明，北川断裂带的自由面条件是滑坡形成的基本条件，滑坡的稳定性是滑坡形成的主要原因滑坡形成的基础是斜坡和灰岩层面的地表连通性，而强度大、持续时间长的强烈地震引起的地面运动是滑坡的根本触发因素，滑坡的机理和过程可分为4个阶段：（a）坡体破碎、松弛、崩解阶段;（B）高速滑动阶段;（9）冲击堆积阶段;第二次抛射和泥石流堆积阶段，由于坡体的失稳和高速下滑，沿主滑动方向形成长4.2 km、宽2.2 km的存款体，高速碎屑流穿越风伯岩下游，沿沿着红洞子沟形成长1 km的泥石流存款带。
The landslide at Daguangbao and Hongdongzigou site is the largest among all landslides occurred during the Wenchuan Earthquake.Its volume is up to 742 Mm3,and its debris dam height reaches 690 m.So it is also the most largest scale landslide triggered by earthquake among all investigated landslides in China.Additionally,it has the highest debris dam originating from landslide in China.It is even one of a few super large-scale landslides known all over the world,whose individual volume is over 500 Mm3.The debris dam formed by this landslide can be the highest around the world.The landslide is located on the upper plate of the Causative Fault.It is nearly 7 km away from the triggering seismic fracture of Yingxiu-beichuan fault.The slope was an isolated ridge before the Earthquake.it's the ridge had its 3 sides cut.Its height difference reaches 1500 m.The strike of clinothen was almost vertical to the slope surface.the clinothen had perfect extension.They composed together the basic conditions of sliding surface formation.Our investigation and analysis show that the free surface conditions of the slope and the surface connectivity of limestone bedding plane were the base of landslide formation.And the ground movement resulted from the intensive quaking with large intensity and long duration was the radical triggering factor of the landslide.The mechanism and process of the landslide could be divided into 4 stages as follows:(a) the stage of slope body shatter,relaxation and disintegration,(b) the stage of high speed sliding,9c) the stage of accumulation with shock,and(d) the stage of the second projectile and debris flow deposition.Because of destabilization and high speed sliding down,the slope mass composed a deposit body along main direction of sliding,4.2 km long and 2.2 km wide.High-speed clastic flow crossed downstream Fengboyan,and formed a deposit zone of debris flow along Hongdongzigou,1 km long.