AE Characters Of Rock Shear Failuer Under Three-axial-stress And Analysis Of Surface Fracture

Rock is a composed of several minerals uneven plastid,therefore the properties of the rock is more complicated.Rock damage in nature and engineering is hard to predict,by applying triaxial stress condition,this paper studies shear deformation and failure process of rock acoustic emission peak frequency characteristics,more than permeability characteristics,and the characteristics of surface roughness,to seek out some sensitive indexes of rock shear failure.True triaxial testing machine used double-sided shear test on granite and limestone and single shear test,combined with acoustic emission instrument acoustic signal,in the process of collection and test for granite double shear stress of the whole cutting process-time curve and acoustic emission parameters-time characteristic curve.Applying different method to analysis and lateral stress,constant shear deformation and failure process of the acoustic emission peak frequency variation characteristics.Experimental results show that the change of normal stress can cause damage in the form of different(steady and unsteady damage),which causes the difference of the peak frequencycharacteristics;Lateral stress change to not significantly affect the peak frequency characteristics;Shear deformation in the process of acoustic emission peak frequency can be divided into the quiet period,ups and downs and rise;Peak frequency can successfully predict the damage threshold of the rock,can be a sensitive index,shear failure judgment granite peak shear stress in the process of frequency variation characteristics and destruction also has certain corresponding relationship between the changes.Analysis in the process of shear failure more than permeability characteristics,found that the events of the connectivity rate of C can be used as the basis for judgment of rock damage.In the process of granite double-sided shear failure,when the event space share reaches 60% to 65%,reach maximum shear stress,granite steady destruction or unsteady failure;In granite and limestone single shear failure in the process,when the event space share reaches55% to 60%,the maximum shearing stress,rock sample.Energy cumulative growth rate also can be used as the basis of rock breaking,shear failure process,the elastic deformation and elastic-plastic deformation stage,the growth rate of energy accumulation value quickly;Shear stress peak value after sample damage occurs,energy accumulation value growth rate significantly reduced.Surface roughness is the representation form of surface micro geometry shape error,this article from the height of the surface roughness parameters(Rsa arithmetic average deviation,and Outlines the Rsz average roughness height,maximum height and contour Rsy)study the shear fracture surface morphologycharacteristics.Found in double side shear failure of granite and single shear failure process,the normal stress value,the greater the value of the Rsa,Rsz and Rsy is smaller;Lateral stress value of the Rsa,Rsz and Rsy value had no obvious effect;In the process of limestone of single shear failure,normal stress value,the greater the value of the Rsa,Rsz and Rsy is smaller.