Acoustic Emission Experiment Research Of Plagiogranite In Yebatan Hydropower Station

Through field survey Yebatan Hydropower station area reveals the deep rock mass deformation fracture phenomenon,and profoundly analyzed the stress environment and moisture state of deformation of deep fracture to design scientific and reasonable test plan.This article is based on MTS815 rock mechanics testing machine and PAC-II acoustic emission testing system research Yebatan Hydropower station plagiogranite cyclic triaxial test on growth and unloading under different confining pressure and moisture content.According to the acoustic emission ringing counting and acoustic emission energy,amplitude reflection rupture point development activity of rock deformation and failure process;And based on burst point spatial cluster distribution analysis rock internal potential danger zone,and reveals the main fracture plane formation and mechanics in instability and failure process of rock.The main research results are as follows:(1)according to acoustic emission events rate,the cumulative number of events,ringing count,energy count over time of rock deformatioan and failure,the changes process of acoustic emission can be divided into five stages,ability and good correspond to stages of rock deformation process.(2)due to the difference structure and materials of compositionof of rock,and non-uniformity,b value change have differences in rock deformation and failure process,but in general has the following pattern: instability and failure of rock before,b values will be a small increase or reduce or small amplitude fluctuation,show that rock failure in steady progressive failure process;Near destruction,b value well be big drop or volatility,rock structure intense damage,crack rapidlly expand and cut-through,on behalf of the instability and failure of an emergency.(3)Based on analysis statistics method of the spatial distribution of acoustic emission events past,puts forward a statistical new method of spatial distribution of acoustic emission events,namely time-distance method.the process of rock deformation and damage can be divided into three stages,and it has two obvious Character meaning point.the point is great important in the process of rock deformation and failure,can be used as the important indicators of rock deformation and failure process of internal structure change.(4)at the beginning of the acoustic emission,the distance between the burst point,mainly 3-6 mm and greater than 8 mm distance ratio over 10%,shows that the distance between the burst point is larger,the correlation is not obvious.With the development of rock deformation and failure process gradually,rupture point distance gradually reduce,concentrated distribution in 1 to 2 mm,the proportion of about 50%.the proportion of distance from 0 to 1 mm,gradually increased along with the rock deformation and failure process and increased from the original 1% to 10 ~ 30%.spatial correlation length instability and failure of rock finally keep in 2 mm or so,when the spatial correlation length decreased to 2 mm indicates the instability and failure of the rock testing.(5)the confining pressure is an important factor to improve the rock mechanics properties,the peak stress and peak strain of saturated specimen and natural sspecimen are significantly increased with increased as the confining pressure.Same confining pressure conditions,peak stress and strain and of natural specimen is obviously higher than saturated specimen rock,present that water can reduce the strength of the rock,and weakening the ability of resistance deformation.(6)Acoustic emission technology is an important method to monitor the stability of rock mass,and its application is widely used in practice.Combined with acoustic emission in different stages of the rupture point of space distribution,determine the burst point bearing spatial cluster,identify the location of the rock internal potential danger zone.d value trend and have a bigger relevance rock deformation and failure process,but to realize the quantitative evaluation of rock stability,and there are many need to carry out the follow-up work.