Analysis Of Acoustic Emission Parameters Of Limestone With Different Rock Burst Tendencies And Research On Fracture Characteristics

With social progress and further development of basic industrial industries,the demand for mining resources in China is getting bigger and bigger,deep mining is becoming more and more popular in mines,and rock burst disasters are becoming more frequent.For acoustic emission technology,rock acoustic emission is an information carrier that can effectively reflect the change of pore structure inside the rock.The characteristics of acoustic emission parameters in the process of rock burst fracture and instability are studied,and the theoretical basis for acoustic emission parameters early warning of rock burst in deep mining is provided.Different depth in the same borehole limestone core sample,to develop the embedded depth of limestone acoustic emission of uniaxial compression test,Brazilian split test and uniaxial and unloading test,based on the elastic energy index,linear elastic and brittle index evaluation index for the embedded depth of limestone rock burst orientation,access to the embedded depth of limestone AE characteristic parameters in the process of uniaxial compression fracture,and the limestone rock burst tendency and analyzes the correlation between acoustic emission characteristics,combined with acoustic emission RA value and AF,macro crack morphology and microstructure characteristics of different embedded depth of limestone sample is studied under different rock burst tendency of failure mode and fracture characteristics,The results are as follows:(1)When the buried depth is more than 600 m,the rock burst tendency of limestone increases step by step from weak to strong.Based on the comprehensive analysis of the rock burst tendency of limestone under multiple criteria,the unified discrimination is made: the depth of 600 m and 700 m is weak rock burst tendency;At 800 m and 900 m,the rock burst tendency is moderate.When the buried depth reaches 1000 m,the limestone shows a strong rock burst tendency.(2)By different embedded depth of limestone under uniaxial loading process parameters were analyzed,and the acoustic emission characteristics with weak rock burst tendency of limestone,acoustic emission ringing count and the number of events appear along with the soothing rose to its highest level of loading process,AE accumulative energy curve showed a trend of "step up" and medium and strong rock burst tendency of rock burst limestone acoustic emission ringing count and the number of events in the pore pressure dense phase is low,the crack propagation stage,the acoustic emission signals into active,smooth characteristic parameter fluctuations,before peak rupture,acoustic emission ringing count and the number of events has risen sharply,During the loading process,the cumulative energy curve of acoustic emission shows a trend of "slow rising-rapid growth".(3)The correlation dimension D value of the acoustic emission energy rate in the process of limestone failure is calculated based on the G-P algorithm,and the fractal dimension value evolution law of limestone with different rock burst tendencies is summarized,that is,from no rock burst or weak rock burst "dimension-fluctuation" The evolution model of "-dimensionality reduction" is transformed into the "smooth-dimensionality reduction" evolution mode of strong rock burst tendency,which provides a theoretical basis for identifying rock burst by acoustic emission parameters in deep mining..(4)Calculate the RA and AF values of acoustic emission parameters during the uniaxial compression of limestone,and classify limestone rock burst failure cracks.It is found that as the depth of burial increases,the limestone changes from a "tensioned" sound under a weak rock burst tendency.The emission signal evolved into a mixed signal of "tension type" and "shear type" acoustic emission under strong rock burst tendency.(5)Combining the classification of limestone fracture macro cracks and the microscopic fracture morphology characteristics,the rock burst failure characteristics of different buried depths of limestone are analyzed: with the increasing depth of limestone buried,limestone with weak rock burst and non-rock burst tends to be tensile failure.Mainly,the micro-fracture characteristics are embodied as inter granular fracture and trans granular fracture between crystals.Limestone with strong rock burst tendency is mainly tensile-shear failure,and the micro-fracture characteristics are embodied as inter granular fracture,trans crystalline fracture and shear fracture.