DEFORMATION AND FAILURE MECHANISM OF YANGJIA WELL LANDSLIDE IN THREE GORGES RESERVOIR AREA

On April 11, 2015, affected by the continuous rainfall, a large-scale counter-dipping rock landslide occurred at Shazhenxi village of Zigui County. The landslide of about 25×10⁴m³ in volume and about 2.5×10⁴m² in area damaged the town road and a large number of facilities seriously. It is named as Yangjia Well Landslide. On the basis of the first-hand field investigation, the special geological features and rock mass structure characteristic of the landslide are studied in detail. The origin of the landslide is analyzed from two aspects including geologic origin and the environment origin. The formation mechanism and evolution process of the landslide is proposed tentatively by utilizing the theories of geomorphy and engineering geology mechanics. It is also predicted the deformation trend of the landslide. Conclusions as follows:(1) This landslide is continuous rainfall-induced counter-dipping rock landslide, and has traction sliding deformation mode. (2) The particular geological structure is the long-term breeding inner condition of landslide formation; the continuous rainfall is the main and direct triggering factors of landslide formation. (3) With valley incised, high stress released and the unloading and rebound of slope, layered rock mass bent and toppled to outside of the slope, producing fissures parallel to slope surface; with the development of consequent tension joints gradually, the undersurface of bending belt formed a weak structure plane which plays an important role in landslide deformation. (4) During the flood season, local deformation may happen in a certain time, but barrier lake and debris flow is almost impossible; it is advised that the corresponding engineering management should be carried out after the flood season.