CHARACTERISTICS AND FORMATION MECHANISM OF HIGH SLOPE LANDSLIDE INDUCED BY WENCHUAN EARTHQUAKE IN MIAOBA COUNTY OF DUJIANGYAN CITY

The 5 12 Wenchuan Earthquake induced tens of thousands of landslides.The high landslide induced by the earthquake presents a unique mountain motion and failure model comparing with the landslide induced by gravity.The Miaoba landslide is a typical representative.The Miaoba landslide lies in the middle of the central fault zone of Longmen Mountains.The intensity of the landslide area is Ⅺ.The landslide volume is about 113104m3.Through the field investigation and synthetic analysis,this paper strives to reveal its characteristics and formation mechanism.It takes a detailed partition of the landslide.According to the partition and dynamic characteristics of the landslide,its process can be divided into the following four stages: (a)the embryonic stage; (b)the starting and accelerating stage; (c)the high-speed motion stage; and (d)the stop and accumulation stage.At the embryonic stage,the reasons of the slope rock mass cutting out with high-speed are explained.The reasons are that the earthquake produced the acceleration coupling slope body structures.Its genetic model is the spatial combination of the crack-granular slipping and then the crack-bedding slipping. between the starting and accelerating to the high-speed motion stage,the paper analyzes the movement program of the projectile coupling the landslide topography.The research shows that the landslide from start-up to end only took 32s, and the average speed was about 20.1m s-1.At the stop and accumulation stage,the paper explains the peculiarity of the accumulation(Ⅲ1)area formation coupling trees of the slope and micro-topography.Based on the above analysis of formation mechanism of the landslide,the paper obtains that the functions of coupling dynamic of the internal and external earth are the reasons of forming the high landslide induced by earthquake.