| The formative mechanism and the stability analysis of landslide is major issues in Geotechnical Engineering, which has practical background and factual purport. Based On extensive field investigation and interior analysis, combining with Hydrogeology and Engineering Geology condition and underground deformation monitoring information and the field sliding Mechanism, the author uses theoretic and numerical analysis and so on tests to assist his research which takes the subgrade lanslide of ding-jiafen village in shuangbai county for object of study. The main rsults of this paper can be summed up as follows:(1) Terrain, ground feature and lithology and inconformity of weathering in the horizontal direction and vertical direction lay the foundations of the formation of landslide. Water-Rock Interaction not only aggravates fissures widening and weaken property of rock and soil and reduce shear strength, but also prompt formation and development of sliding zone.(2) Vegetation cover prompt evolution of landslide. On the one hand, the development of vegetation roots promotes fissures widening, which is in favor of water infiltration. On the other hand, the vegetation cover in the area adds weight and the swing power which result from wind blow to vegetation. As a result vegetation cover has an adverse effect on the stability.(3) Based on the condition of strong rainfall, after the landslide experience the front edge deformation process of creeping-creeping expanding-formation of potential sliding zone under the action of composite mechanism which forces the slope to experience the deformation process of creeping-tension fracture-shearing, the landslide is generated.(4) The relation between landslide sliding and shear strength reducing is not a simple one-way driven program. on the one hand, sliding cause gain crushing. Its not only produces bathtub model, but increases pore water pressure. As a result of this, effective stress and shear strength bring down. on the other hand, lessening shear strength driven landslide sliding.(5) On the strength of Rescale Range Anlysis from january to july in the year of 2010, the monthly average displacement of ZK2,ZK10 and ZK 11 was in incremental condition and the Hurst and C (t) index of displacement had a distinct trend of declining along with the gradual failure of landslide. By the end of july in the year of 2010, although the Hurst and C (t) index of ZK2,ZK10,ZK11 reduced to 0.800,0.7634,0.7642 and 1.5658,1.3311,1.3360 respectively, the Hurst and C (t) index were separately greater than 0.5 and 0. It is found that a complex mass movement of landslide is not generated and small-scale destruction happen.(6) Based on Numerical Simulation Analysis, the upper of depletion is more stable in comparison with the bottom. the zone deepened from 9 m to 20 m of depletion and accumulation not only has obvious phenomenon of stress concentration, but Kp is less-than 1.5. The Kp of partial shallow surface deepened from 9 m to 10 m is less-than 1. Its confirms that shallow surface deepened from 9 m to 20 m of zone of depletion and accumulation is easy to destroy., Especially shallow surface which The Kp is less-than 1 is easier to destroy or have beening run.(7) Combining with Rescale Range Anlysis and Numerical Simulation Analysis, it is found that the upper zone of depletion is more stable in comparison with the bottom. The whole landslide is in the unstable condition and parts of shallow surface of the landslide have beening run which generates catastrophic Phenomenon, such as falls, topples, and earthflow, etc. If it heavy rains, that mass movement of landslide should be generated and cause integral destruction.
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