Deformation And Failure Mechanismand Stability Predictionof Traction Zone Inqianjiangping Landslideof Three Gorges Area

On July 13,2003,43 days after an impoundment to 135m of the Three Gorges reservoir,a landslide(2×107m3)in bedrock which lasted five minutes occurred at the village called Qianjiangping in ShaZhenxi town of ZiGui county in Hubei Province.Qianjiangping landslide was the first catastrophic landslide occurred in the reservoir area of the Three Gorges dam after its impoundment and its sliding characteristics and formation mechanism received extensive attention.Domestic.and foreign scholars use different methods to analyze the formation mechanism of the landslide,including geological conditions qualitative analysis,numerical simulation,physical simulation,comprehensive study.The current academic pay more attention to formation mechanism of Qianjiangping landslide while less attention to the deformation?failure and stable trend of the traction area of the landslide.Bedding Bank Slopes similar to Qianjiangping landslide in Three Gorges Reservoir are widespread and instability and failure of the traction area of the landslide often happen after the landslide occurred.So the research of the stability of traction area of Qianjiangping landslide can provide theoretical basis to control new landslide in Three Gorges Reservoir.This paper selected Qianjiangping landslide traction area as the study area.Traction area was delineated in accordance with the regional geological structural and boundary features.Following analyzing the characteristics of the landslide,FLAC3d software was used to study the deformation and failure mechanism and the steady trend of the traction area under the action of the reservoir water:(1)conditions of mpounding:the traction area was stable under 95m water level.With the rising of reservoir water level from 95 to 135m,slope stability declined,tension zone appear at the front and the edge of the traction area and the shear zone appear at the weak zones.The slope was in a stable state,but lower security reserve.With the rising of reservoir water level from 135 to 175m,the slope stability continue to decrease,but change little.(2)conditions of water level falling:the reservoir water level will be adjusted after an impoundment of the reservoir to 175m and the reservoir water level will fluctuate between 145 and 175m.Hydrodynamic pressure was formed in the slope and groundwater seepage in the slope.Slope stability perform as follows:the stability decreases as the water level drops.Above all,we determine that the stability of the landslide traction zone:The rear of the sliding body is less stable and the plastic zone generate tensile fractures first.The front edge of the slip surface is nearly flat,so the front play the role of resisting slipping from the perspective of the force.Traction area may damage characterized by thrust load-caused.Traction area is still stable with an impoundment to 175m of the Three Gorges reservoir,while the stability of the traction zone continued to decline with the reservoir water level dropped by 175m to 145m,traction zone was still in the stable state.