Dam Shoulders Anti-sliding Buckling Mode Research For Songta Hydropower Station In Nu River Of Tibet

Songta dam is located in the territory of the Tibet Autonomous Region Cawarong Chayu County,Nujiang rivers to about N10 ° E,flows south,presenting a narrow valley shape,straight river dam area,the valley presents the symmetrical "V" shape.Engineering design type is hyperbolic arch dam,the largest dam height of 318 m.Both sides of abutment rock structure is more complex,there is the development of dykes,faults,steeply dipping gently inclined cracks and fissures in these structures may constitute a boundary surface potential instability of the block.Therefore,the identification of the two sides abutment surface resistance of the body's structural development characteristics and boundary conditions are a prerequisite for abutment against sliding mode instability analysis and stability calculations.Based on the engineering geological conditions of the dam,the statistical characteristics of the rock abutment structure development,the use of projection,trace length estimation and two-dimensional network simulation method calculates the gently dipping steeply dipping fractures and fracture connectivity rate,according to rock icosahedral structure connectivity features a combination of potential instability blocks,and the blocks were calculated and analyzed unstable modes.details as follows:(1)Structural features of the abutment rock analysis: Veins and wall rock contacts features to Merging contacts and contacts based fissure,fault fracture zone and substance cuttings silted mud cuttings folders based;The overall occurrence of cracks present "a group of two steep and slow crack crack",steep crack and slow crack in the continuity,roughness,opened similar filling and groundwater characteristics,namely continuity in [1 ~ 3m)to Lord,wavy rough roughness mainly fill open to close without filling the main groundwater dry,wet-based.(2)Based on trace length estimation method(H-H method,Laslett method)is calculated steep connectivity rate,the rate of communication with steep elevation to draw each communication rate band and S4 sectional tendencies attributed belt.Potential side fracture surface communicating values Select: trace length estimation steep rate tends to crack communicating attributed value.LCB-3 to give the left bank of the LCB-7 with five sharp split within the scope of the arch thrust,communicating values from 5.1% to 46.8%,which LCB-4,LCB-5 connectivity rates were 46.8% and higher 42.1%;RCB-2 within the right bank to the RCB-8 with seven located thrust arch scope,communicating values from 14.7% to 65.2%,the highest value of 65.2% is located in RCB-2 band;High steep right bank of communicating with more than the development of the left bank,two high connectivity rates on the left bank of the steeply dipping zone(LCB-4,LCB-5)accounted for about half of the arch of the left bank of the scope of thrust,while the right bank of four high connectivity rate almost all of the steeply dipping zone(RCB-4,RCB-5,RCB-6,RCB-7)occupy the right bank of the arch thrust of influence.By projection,trace length estimation and two-dimensional network simulation method were calculated in the gently dipping fracture connectivity rate,the rate of communication with the gently inclined towards the elevation of each draw band connectivity rate and S4 sectional tendencies attributed with give and trace length estimation dimensional network simulation tendency attributed value.Potential slip bottom surface communicating values chosen: to trace length estimation of the value attributed to slow cracking tendency,combined with the two-dimensional network simulation method tends to be attributed to the value of the high value of trace length estimation method was compared with taking a large value or mean.LB-4 to get the left bank LB-10 in seven slow crack band could cut and thrust in the arch of influence,communicating values were: 54.7%,35.1%,25.9%,29.4%,33.8%,32.4% and 36.3%;right bank RB-4 to RB-5 may be cut and within the scope of the arch thrust,communicating values were taken 52.0%.(3)According to three faces potential side fracture surface,fault plane and potential slip bottom surface combined nine unfavorable abutment stability of the block(the left bank of seven,on the right bank two),calculated using the rigid limit equilibrium method under load stability;Conclusion is: no earthquake conditions,the potential instability of the left bank just blocks overall design requirements to meet the arch,on the right bank below the design specification requirements;While there is an earthquake conditions,the left bank to f33 is a side fracture surface of ZKT-1,on the left bank with f133 is a side fracture surface of ZKT-7,on the right bank with f111 is a side fracture surface of YKT-1,on the right bank with f116 is a side split face YKT-2 in pure shear friction and low friction coefficient computing security.The four blocks may be unstable,located near surface boundary condition is visible from the outside and at the end of the arch,should be addressed;In general,the overall dam abutment skid resistance or compliance with the design requirements.