| The Yagong toppling failure is located on the right bank 5 km upstream of the Lancang River in Liujiangtong Village,Deqin County,Diqing Autonomous Prefecture,Yunnan Province.A planned hydropower station,named the Gushui hydropower station,is located upstream at a distance of 2 km from the study area.The Yagong toppling-failure is distributed in the elevation range of 2250m-3250m with a volume over 8×10~5 m~3,the relative height difference was exceeding 800m,the slope is 40°approxmately.According to the field investigation,the rock mass in the study area toppled intensively in double directions.The horizonal depth of toppled rock mass was exceeding 200m.The intensive toppled rock mass has a possibility of evoving into a huge landslide triggered by some factors,such as manual excavation,futher erosion of river and rainstorm.Based on the detailed field investigation,we investigated the discontinuous,including joints,weak structural plane and faults,which were developed in the study area.The structural types and rock mass quality of the toppled rock mass were also classified and zoned.The failure mechanism and stability of the toppled rock mass were also analysied by using physical modeling and numerical simulation method.Some important results were obtained as follows:(1)Due to the reconstraction of geological tectonic movement and the erosion of Lancang River and its tributary Mushui River,the large-scale toppling deformation on double directions is formed(normal rock mass turns to N10°E,NW?80°?90°,toppling failure rock mass turns to N80°E,SE?20°?40°,S80°E,SW?15°?45°)(2)According to the research results of experts and scholars on the classification of toppling failure degree,combined with the actual situation of the Yagong toppling failure body.The results show that the toppled rock mass located downstream of the landslide could be classified into four zones,namely,highly toppled,strongly toppled,weakly toppled and normal rock mass,from the surface to the deep-seated rock mass along the slope according to three factors:the unloading intensity,variation in the occurrence of the rock layer,and toppling fracture zone.(3)Based on the field investigation of the adits of Yagong toppling failure body,the structural plane of Yagong toppling failure was divided into five types and the geological characteristics of each type of structural plane were analyzed and summarized.At the same time,the influence of the combination of the superior structural planes on the stability of the slope was analyzed,and it was concluded that the combination of the structural planes may lead to the slope failure.(4)According to the specified specifications,the engineering quality grade of rock mass in each adit was calculated,and it was concluded that the rock mass of Yagong toppling failure body is mainly grade III and grade IV,and the rock mass is broken as a whole,providing internal conditions for slope deformation and failure.(5)On the basis of the failure characteristics of the toppling failure body,combined with the geological qualitative analysis,physical simulation test analysis and numerical simulation calculation analysis,it was concluded that there are three types of failure modes of the toppling deformation body in Yagong:toppling tension fracture,toppling fracture dislocation,sliding shear,and the potential failure surface path of the slope is inferred.(6)Based on limit equilibrium method of rigid body,the present stability and the future evolution trend of Yagong toppling failure were calculated.From the calculation:The stability of Yagong toppling failure is better under the natural condition.Under the rainfall condition,the overall stability is relatively good,and in the excavation condition,the overall stability of the slope changes obviously,which may lead to instability. |
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