Study On The AE Characterizaiton Of The Meso Micro Fracture Development Of Rock Under Uniaxial Compressive Loading

Acoustic emission technique is a kind of real-time dynamic nondestructive testing technology,and the current acoustic emission technology has become an effective tool for dynamic monitoring of micro fracture in the process of deformation and failure of rock.But rock failure instability occurs mainly from the inside and the outside of the,and and rock fine internal view is closely related to the structure and the internal defects,but only rely on the acoustic emission technique is difficult to from the meso level determine the rock internal micro cracks development law,so for acoustic emission and micro fracture direct relationship will not be set up correctly,so unable to macroeconomic instability and failure to provide accurate judgment basis,with the result that the sound emission technology in monitoring and forecasting of engineering disaster did not play its due role.So carried out the rock meso damage and failure to lose the steady process and acoustic emission study on the relationship between the variation of the parameter,the acoustic emission parameter of rock fine micro rupture and macroscopic failure instability were characterized,has important theoretical and practical significance of acoustic emission technique in rock dynamic disaster monitoring and forecasting application,also has the important theoretical significance of acoustic emission technology in the laboratory application.Firstly,emission technology and research results of CT scanning technique the sound at home and abroad are analyzed and summarized;followed by using the acoustic emission(AE)combining the technology of monitoring and CT scan,of three kinds of rocks are gypsum,mudstone and sandstone were experimental failure under uniaxial loading conditions;again for three kinds of rocks in different loading stages of acoustic emission characterization parameters and CT scan results were analysis.Finally the data were analyzed and summarized,draw the following conclusions:(1)Acoustic emission event location in the initial loading less distribution is scattered,CT scan with contrast is mainly a result of the due to the ends of the specimen in the process may exist at both ends of the uneven and lead to occur in the early stage of loading rock internal stress re adjustment;with the load increasing event location increases gradually accumulate,load to increase location events increased rapidly again scattered distribution in part of the region appear to aggregate the results of CT scan results were control derived from analysis of AE location events that can directly reflect the loading process inside the rock crack,propagation,coalescence and finally form the macro crack.(2)Rock test pieces in the loading process,the energy curve and ringing count curve of acoustic emission(AE)showed a point mutation,and the point is rock acoustic emission signal of Kaiser effect point,through the energy curve,and ringing count curves of Kaiser point comparative study and find the Kasier effect point corresponding to the load,by acoustic emission method for measuring stress and provide the basis for.(3)During the process of rock failure,the AE activity showed different active degree with the increase of the load.In the early stage of loading and acoustic emission activity is not active enough,acoustic emission activity energy,ringing count less,just in the Kaiser effect point appear suddenly increased,after the acoustic emission duration is not active,energy,ring count smaller;with the load increasing,the acoustic emission activity began active,energy,ringing count increases;load to increase to the specimen,the acoustic emission activity in the most active,energy,ring count before the specimen reaches the maximum.(4)In the process of rock failure,the different sections of the specimens are different in different load stages.In the early stage of loading test of pore and fracture closed to varying degrees,sliced porosity,primary crack width becomes small;with the increase of the load,into the elastic deformation stage,this stage with the inner pore and fissure again opened,the stability of primary crack continues to expand and new crack derived leading to porosity also sustained and stable increase;load to increase to the specimen,specimen crack propagation velocity increases quickly,original cracks and new crack continuous expansion and through,and finally the formation of macro cracks form the macro crack.(5)Contrast to the rock failure process,the acoustic emission activity(energy,ring count)and the results of CT scan(porosity,crack width,length)with the load increasing different changes,can be found in the acoustic emission energy,ring count parameters in different stages of load change situation can in some extent characterization of rock sample test piece under load at different stages of the test pieces within the pore and fracture development.By observing the change of the acoustic emission characteristic parameters,it can be inferred that the damage degree of the rock specimen is monitored.