Inversion Of In-situ Stress Field Of Dam Site Area And Study On Surrounding Rock Stability Of The Underground Powerhouse

The yabiluo hydropower station located nujiang river main stream of theLuShui county in yunnan province，is the seventh step engineering of thirteenhydropower plan in the middle and lower of the nujiang river. This reach is alpinevalley type landform, the mountain top was the higherThan river bed nearly1000m, the channel is convex to the west. The largest heightof the arch dams planed to reach152.5m, reservoir normal storage level is1075m,its installed capacity cound reach1950MW, the length of reservoir is about32km,with a total capacity is471.3million m3.Hydropower station dam site reach out outdoor layer mainly for the proterozoicgroup GaoLiGongShan group (Ptgl1) mixed rock, including gneiss shallow grainrock schist,etc, part of the rock have altered phenomenon. Surface mapping anddrilling, adit revealed that the lithology is mainly for gneiss. According to theweathering degree of rock mass in the dam site area can be divided into weakweathering and breeze mineralization belt, the dam site area fracture moredevelopment, fault density is larger, the fault f4through the undergroundpowerhouse.Hydropower station dam site area of drilling zk54zk29zk34three dimensionalgeo-stress measurements made, according to the measured results show that thehorizontal tectonic stress plays a leading role, therefore, the stress field is mainlycomposed of tectonic stress field and gravity stress place composition. According tothe working condition of four different respectively established the gravity stressload model horizontal tectonic stress load model and tangential stress load model,selecting appropriate physical and mechanical parameters of rock mass and fault,Using linear elastic constitutive model, using the finite element software (ABAQUS)three dimensional finite element stress regression analysis, the study area is obtainedof the stress regression equation, namely for the dam site area of the ground stressfield. Contrast the measured point measured value and return value, and the resultsshow that stress regression value is reasonable, more close to the measured point. The region ground stress field by the horizontal tectonic stress is given priority to,the maximum principal stress close to the level, the direction for NE～NEE.According to the position of the hydropower station underground powerhouseburied deep lithologic and fault characteristics, a simplified model to reducecalculation time take underground powerhouse depth length for the model length.Model using free mesh division unit and using the elastoplastic constitutive modelfor finite element analysis using Matlab software fitting ground stress field and thecoordinate function relationship, write in FORTRAN program, using ABAQUS usersubroutine SIGINI applied to model the initial geostress field, balance in-situ stress.According to the hole room engineering characteristics, by go up and down thepartial section excavation method, is divided into12excavation section simulationcavern excavation process. Based on the simulation results, the numerical valuecalculation, this article analyzes the integral stability of the rock mass ofunderground workshop is good, because in the rock mass to the development of theunderground powerhouse structure complexity with the excavation, the surroundingrock stress redistribution, underground powerhouse table department may occurunloading rock mass, Suggestions on table department rock for spray concrete andsome random bolt support, near fault rocks in anchor reinforcement. Considering thesize of underground powerhouse and its importance, the proposal of buildingengineering monitoring of surrounding rock.