Study On Failure Mechanism And Instability Of The Laminated Rock Slope At The Left Bank For The Dam Site Of Ciha Gorge Hydroelectric Station Of The Yellow River

Ci Ha Xia Hydropower Stationis located in tongde county in qinghai province,along the border with xinghai county gorge canyon near the mountain pass,is the Yellow River mainstream results above,altitude 3000 m below the river's largest cascade hydropower stations.Height of dam site area belongs to deep valley landforms,the slope of about 400 m,steep slope,average slope in more than 40 °.On the left bank slope mainly consists of thin layer sandstone and slate of oblique or reverse slope,these are toppling for slope deformation created good conditions.In less than 4 km range of slope development 3 large toppling body,among them 4 # and 10 # toppling body distribution near the dam axis,the 2 # toppling body is distributed in the left bank of the plunge pool.Therefore,the slope stability has a very important influence on engineering activities,how to correctly analysis of slope buckling failure mode and the reasonable calculation of slope stability of engineering construction and operation has a crucial role,once the slope instability will cause big loss to engineering,and may have major disasters.In dam site area on the left bank slope of the terrain conditions,lithologic assemblages,type a detailed analysis of the slope structure,combined with the feature of deformation and failure of slope at present,to study the anti inclined slope deformation mechanism and failure mode and its controlling factors;And take the stability of different calculation methods for typical slope stability evaluation.The main obtained results were as follows:(1)According to the characters of slope topography,rock mass characteristics and slope structure will be studied area slope points 4 districts and 9 subregion,? area are mainly distributed in 10 # and 4 # toppling body,slope in 55 °,30 ° ~ mainly oblique slope,more ZongLong depression for reverse slope;? area mainly for oblique slope,located in 10 # toppling body downstream to the elm ditch,slope at 40 ° ~ 55 ° between;? toppling area in 2 # scope,mainly for the reverse slope,slope between 30 ° ~ 40 °;? area distribution in the downstream to 8 # 2 # toppling body toppling body,mainly for the transverse slope,oblique,local slope at about 45 °.(2)Investigation through the scene on the toppling slope deformation characteristics,combined with lots of adit and drilling data analysis,according to toppling toppling body within the scope of slope can be divided into four zones,by the table and inner surface loose and broken zone respectively,strongly toppling cracking deformation zone,medium toppling cracking deformation zone and mild toppling deformation zone.(3)Thin layer of hard and soft interbed of sand plate for the dam site area,toppling slope deformation provides a material basis,good conditions and oblique international airport near the reverse slope structure to control the slope of the toppling deformation degree.Study area soft interbed of toppling slope deformation mainly has experienced four stages: The initial stage,the slight bending stage,the crack propagation stage,the breaking or the crushing stage.By bottom friction test simulated the tilting deformation of layered rock slope instability process found that toppling slope deformation mainly occurs in the process of instability of the layer in shear rupture,internal tension,broken overhead bursts and shear slip.Toppling slope deformation after the formation of the toppling of body section depth changes show different toppling broken degree,surface deformation of toppling the most intense,cracking deformation,with depth increase cracking deformation degree reduced.(4)In the dam site area on the left bank of detailed geological environment condition,based on the analysis of the deformation characteristics and deformation mechanism,summarized in layered rock slope instability mode mainly include two categories: sliding instability and buckling,the collapse of sliding instability mode is divided into two categories: one is controlled type continuous destruction of the slip,cracking and sliding shear,secondly,controlled by discontinuous damage the ductility curved toppling,brittle fracture and compression;Collapse buckling mode mainly for toppling and sliding collapse collapse.Through the typical toppling deformation of slope establish UDEC model analysis,toppling deformation of slope deformation and failure is mainly affected by the slope surface control structure and different combination of structural surface forming different instability modes.Topplinging body surface loose and broken zone is mainly collapse instability and failure,in prominent parts of the terrain possible collapse and slip or slip crack sliding instability;topplinging body in the posterior development a lot of steep dip tensile cracks,especially parts of the ridge,and the front slope of a group of gently inclined structural surface combination,together constitute the toppling deformation of slope slip shear type instability boundary.(5)In characteristics of left bank slope deformation and instability mode analysis,based on the preliminary conclusion slope topography conditions mainly control the development of slope deformation and destruction,main control characteristic and the structure of the slope rock mass slope deformation and instability of type,level,structural plane,and the weak combination is mainly to control the size of the instability and failure of slope.(6)Using analytic hierarchy process and fuzzy comprehensive evaluation method to the dam site area on the left bank slope stability evaluation,and compare the limit equilibrium method,finite element method and intensity coefficient of subtraction in toppling body overall stability calculation results,the strength coefficient of subtraction application obtained good effect.