MECHANISM AND EVOLOTION OF TOPPLING IN INTERBEDDED SLOPES AT UPSTREAM OF YALONG RIVER

The mechanism and evolution of toppling in interbedded rock slopes in upstream of Yalong River are analyzed with the typical case of Jaxi toppling. The analysis covers the aspects of geological background, development characteristics and formation conditions. This comprehensive study points out that the large-scale toppling in research area is developed by the unique structure of slopes in gravity stress field. The slopes are consisted of a pervasive foliation dipping steeply into the slope, have soft layer and hard layer interbedded and a set of well-developed cross-joints. A model illustrates a typical feature of toppling failure of interbedded rock slope. It is recombination of block-flexure toppling in hard rock and flexural toppling in soft rock, respectively. With the evolution of Yalong River, the deformation of the slope experiences four steps:unloading and rebound, initial deformation, breaking in flexure, and failure as landslide. The sliding surface can be developed along the cross-joints, rather than the maximum bending zone.