Abstract:

Pianshan landslide, one of the large-scale landslides in Geheyan reservoir, occurs 54 km far away from Geheyan dam in the middle-reach of the Qingjiang River. Since the stability of Pianshan landslide maybe directly threaten the safety of local more than 200 lives and normal operation of the Geheyan reservoir, it is of significance to carry out the study on the formation mechanism of landslide by the means of field investigation techiniques such as engineering geological mapping, drilling, geophysical, trench exploration and so on. The result shows the external driving factor is the mainly influencing factors on the landslide stability,such a as rainstorm and the water level fluctuation of the reservoir and topography, lithology, physical structures are the secondary factors.Monitoring results from deep displacement, surface displacement and surface cracks show the landslide is now in the creep stage and the deformation formed in partial section. Stability calculation of the landslide combined with the formation mechanism and influence factors show that the landslide is in the state of the integral stability, but the stability coefficient will be decreased and even slumping occur in local place under the conditions of rainstorm and sudden drawdown of reservoir water level.

Key words: Pianshan landslide, consequent landslide, landslide deformation, Geheyan reservoir on Qingjiang River