The Study Of Rock Mass Unloading Characteristics Of The Right Bank Slope Of Laxiwa Hydropower Station Dam In Yellow River

The right bank slope on area is located in the area of Shuidiantang slope—Shuangshu valley of Laxiwa hydropower station dam.The right bank the fruit bank slope of rock mass unloading depth and distribution is larger,the same as the dam site area,lithology and structure under the condition of unloading rock mass characteristics exist significant difference.Further study of the cause of unloading rock mass characteristics has important theoretical and engineering significance.Area of laxiwa hydropower station and dam on the basis of studying the geological environmental conditions and characteristics of unloading rock mass are studied in detail,and by using the established quantitative index of rock mass unloading fruit bligh unloading characteristics of the right slope of the bank slope and dam site area has carried on the quantitative zonation research,combined with the feature of valley evolution,valley stress field,the research fruit zone in deep formation mechanism of unloading zone.The paper's main conclusion are as follows:(1)Advantage through structural plane Angle relationship with the river valley,bad geological phenomenon and factors,such as distribution density,on the right bank of the dam slope according to the characteristics of slope structure is divided into four areas: shuidiantang slope after the dam slope to ? area of upstream cross ditch,cross ditch to beam is ? area within the scope of 1,2 ~ 4 liang is ? area,double tree gully beam ~ for 4 IV area.(2)Take qualitative analysis and the quantitative indicators such as velocity ratio,the integrity coefficient,the RQD,fissures opening closed ratio,water permeability to make a comprehensive study for the dam site slope rock mass weathering and unloading,results showed that the lower limit of weak unloading is about 16~57m;the lower limit of the weak unloading is about 59~165m;up to 285 m deep unloading most.Generally,the weathering and the unloading depth of ridged terrain are obviously greater than ditch part,and the high elevation is greater than low elevation.(3)The toppling condition of massive rocky slopes including terrain conditions,physical and mechanical parameters of rock,rock structure and stress conditions.(4)According to the regional geological data and Guobu bank slope's engineering geological conditions,on the basis of regional river bank slope evolution history research,shows that under the special geological conditions of Guobu bank slope,in the process of incised valley that the accumulation of granite formation in the early tectonic movement of ground stress,energy release rapidly,the unloading rebound tracks early dipping faults,structural plane creep cracking along the flat structure surface,eventually forming deep unloading zones.That is to say,the deep unloading zone of Guobu bank slope is the product of shallow reformation of rock massbank deep reformation is shallow rock mass unloading zone of the product.(5)Using phase and FLAC3 D on the right bank of reservoir rock mass stress field characteristics,the formation of unloading zones of rock mass in numerical simulation research shows that stress of rock bank slope zoning results and the basic corresponding bank slope unloading depth,better explain the dam site area and fruit of bank slope rock mass unloading zones development difference.