Deformation failure mechanism of Baijiabao landslide in Xiangxi River Valley

Baijiabao landslide(located near the mouth of Xiangxi River) continuously and seriously developed after the impoundment of Three Gorges.Surface investigation showed that there were shearing,tensing and crush-pressing fissures.The monitoring data showed that displacement of middle part was bigger than that of forepart,and the moving direction changed because of 139 m impounded water.Deep displacement monitoring showed that there was a clear sliding surface in the middle part of landslide.So the landslide mechanism was towing forward and pushing backward,and towing happened mainly in the prophase,while pushing happened mainly in the anaphase.The key of transforming from deforming to failure was the penetration of slide-surface in the disintegrating region.With the help of FEM,it was found that the stress convergence region was located in the disintegrating region in the middle of landslide.It was suggested by geo-engineering analogy that this landslide failure type should probably be a sliding with mid-low velocity.