Abstract: In August 2010，Sichuan Province was hit by heavy rainstorms，and a large number of landslides formed under the action of heavy rainfall，among which was Guanyintan landslide.The landslide has been continuously deformed since the formation，posing agreat threat to the life and property safety of the people living at the toe of slope.Through engineering geological survey，it is found that the square of the landslide body is 81，000m3，which is a small bedding landslide.The plane shape of the landslide body is tongue-shaped.The surface of the landslide is obviously deformed.Seven broken line cracks were developed at the trailing edge，side wall and middle and rear parts of the landslide.In the natural，heavy rain and earthquake conditions，the typical section is selected to establish the calculation model.The stability of the landslide is calculated by SLOPE/W software.The results show that the safety factors of the landslide in natural and seismic conditions are 1.541and 1.072，respectively.Both are in stable states.Under heavy rain conditions，the safety factor of the landslide is 1.019，which is in an unstable state.Combined with process geological survey and stability calculation and analysis，the formation process of Guanyintan landslide can be summarized that air condition generated by slope excavation，together with agricultural production，which intensifies deformation，eventually lead to slope instability under the rainfall.Its geomechanical  mode is sliding and fracturing.

Key words: rainfall landslide, slope stability, formation mechanism, sliding and fracturing

摘要： 在2010年的8月,四川遭受特大暴雨袭击,强降雨作用下形成了大量滑坡,观音滩滑坡便是其中之一。滑坡自形成以来持续发生变形,对坡脚处的群众生命财产安全构成巨大威胁。通过工程地质调查,查明滑坡体的方量为8.1万m~3,为小型顺层滑坡,滑坡体平面形态呈舌形;滑坡表面变形明显,滑坡后缘、侧壁及中后部发育7条折线型裂缝。在天然、暴雨以及地震工况下,选取典型剖面建立计算模型,采用SLOPE/W软件对滑坡的稳定性进行了计算,结果表明:在天然及地震工况下滑坡安全系数分别为1.541和1.072,二者均处于稳定状态;在暴雨工况下,滑坡安全系数为1.019,处于欠稳定状态。结合工程现场地质调查与稳定性计算分析,观音滩滑坡的形成过程可概括为:边坡开挖产生临空条件,农业生产活动加剧了滑坡变形,降雨作用导致边坡失稳,其地质力学模式为滑移拉裂。

关键词: 降雨滑坡, 边坡稳定, 形成机制, 滑移拉裂