Deformation Failure Mode And Stability Study Of The Natural Slope On The Abutment Of Songta Hydropower Station In Nu River Of Tibet

Nujiang River hydropower station is located in eastern Tibet Autonomous Songta Chayu Nyingchi County Cawarong,designed with double curvature concrete arch dam height of 318m,the world’s most similar type of dam.Study area slope steep hill and valleys relative height above 2000m,is a typical alpine valley topography,slope inside the development tendency of the slope outside the crack and slow steep dykes,faults.Among these features,and gently dipping fissure veins,deformation and fracture behavior of the fault has been unstable modes and the stability of the slope may play a controlling role in abutment slope stability can have a significant impact on the type of dam finalized,restricting select engineering arrangement and design scheme.Therefore,this article in the understanding of the study area engineering geological conditions,based on the structure and rock slope deformation and fracture have been signs of departure.The use of trace length estimation method calculated in the study area on both sides of each adit communicating values,while signs of deformation and fracture of each survey line adit appearing one by one from outside to inside the search,integrated communication and degree of rock deformation and fracture was a possible cross-strait abutment slope instability modes and boundaries of the study area.Then,by means of numerical analysis software FLAC^3D and limit equilibrium method abutment slope stability analyzes and calculations.The following results were achieved mainly and understanding:（1）Through field investigation,indoor statistical analysis in the study area has a gently inclined fissures unevenness.Specific performance between the left and right banks,different elevations,on the lower reaches of the differences:the left bank of the slow crack development less than the right bank;the elevation,less slow crack in the overall number of high elevation,but three slow penetration in the number of relatively large cracks（ie"sparse and long"）;a small amount of slow crack in the bottom elevation,but three slow penetration of the relatively small number of cracks（known as"dense and short"）.The direction down the river,upstream of a larger number of slow crack growth,down stream of a small number of slow crack development.More importantly,from the dome to the inner slope tunnel segment of the range of 150¹80m,the slow crack along the cave deep distribution is uneven,namely in the form of density and white.Slow crack in the typical interval distribution of lead in the study area connectivity values distributed by leaps and bounds,communication often becomes part of the high rate of regional instability through.（2）Study on deformation and fracture zone is divided into the following 5 types:shear-slip,slip-rifting,Zhang shear rupture,steeply dipping rifting and Mud rupture zone.Wherein the shear-slip and slip-mainly developed in rifting shallow section,the difference between two steep crack development thereon whether the open.Zhang slope Up shear rupture in vivo distribution,mud rupture zone also belongs to the category of Zhang shear rupture from the genesis for the folder,deformation and fracture behavior of these two control modes slope instability and sliding bottom border.Steeply dipping rifting phenomenon generally along the faults,dykes and rock face of the structure,slope instability may become a trailing edge crack surface.（3）Comprehensive analysis of the local deformation instability following two combinations of modes:（1）Slow crack and split steep combinations:slow slope superficial cracks along the inclined portion of the development of structural surface creep thereby pull off the steep slope fractures occur in vivo instability,such deformation occurs in the more superficial portion.（2）The slow crack and steep dikes combination of faults:slow slope superficial cracks along the inclined portion of the development of structural surface creep,body steep slope faults,dykes along the contact surface or fault fracture zone occurred rifting.The main part of the study area of slope instability occurred occurred in the shallow section,the possibility of instability in the deep occurrence is unlikely.The two sides slope failure modes are different.Right bank slope instability may be mainly in the form of stepped instability,and because the steep right bank dyke and development intensive,and therefore may be unstable after the slope edge crack surface selectively lot,thus resulting in a multi-ladder instability based.Left bank slope faults and dikes on the right bank development is relatively small,it may bottom border instability mainly due to the elevation of each Mud rupture with the top down through the lap can control the main folder along with the mud mansard Instability based,multi-step does not appear unstable phenomenon.（4）On the basis of qualitative analysis to study the geological prospecting line cross-sectional area S2^S4 geoetric model,using simulation software has been FLAC3D slope stress field in the state of nature,the analysis of the slope of the stress distribution and shear strain characteristics.Calculated by limit equilibrium method in the study area on the right bank slope except S4 line of local insecurity in the remaining parts are all in steady state conditions,the left bank line of slope S2,S4 line unstable blocks more,should focus on strengthening protection.But this stability is only relatively slow crack growth,high connectivity rate,and thus its superficial portion there is a greater possibility of local small-scale instability based on the specified chunk body obtained in the study area.