Experomental Study On Gas Seepage Characteristics And Acoustic Emission Characteristics Of Permeability Coal Seam

Gas control is the most important thing to prevent serious accidents in coal mines,and it is of great significance to eliminate the hazards of coal gas.With the increasing of the average mining depth,many coal seams in China show the characteristics of high stress and low permeability,which further increases the difficulty of gas control.In this paper,Lu’an Changcun Coal Mine No.3 coal seam as the research object,carry out the low permeability coal seam gas seepage experimental study on acoustic emission characteristics.The main contents include the following:First,the thesis analysis the related theory of permeability of coal,further discusses the coal permeability characterization factors,the permeability of coal characteristics,coal permeability evolution and coal permeability factors.In addition,the thesis analysis the Kaiser effect mechanism and acoustic emission mechanism of coal and rock mass,expounds the application of acoustic emission technology on coal permeability test from the two aspects.They lay the foundation for the study of the characteristics of permeability and acoustic emission.Secondly,sample coal samples on the Lu’an Changcun mine N3 workingface,and prepare standard coal samples(Φ50*100).And on the basis of the basic mechanical parameters of experiments,two experiments are developed with WYS-800 microcomputer controlled electro-hydraulic servo three bearing fluid seepage test device,including coal-gas coupling experiment of three axial compression and experiment of coal-gas coupling in three-axis cyclic loading and unloading.The results are as follows:(1)The stress-strain curves of coal samples during cyclic loading and unloading process will be controlled by the corresponding curves of the triaxial compression test.The variation trend of permeability and strain of coal samples is very good with the stress-strain relationship,but the maximum permeability of the permeability curve is relatively lagging behind the stress to the peak point.(2)The strain-permeability curve of coal has piecewise significant feature.In the loading process,with the increasing of axial stress,the permeability of coal samples will show a trend of steady-decrease-increase suddenly-keep high stability.(3)The stress strain permeability curves of coal samples are separately divided into four sections after the first loading and unloading tests.In the four stage,the characteristics of the permeability change are that the permeability is reduced,the permeability increases slightly,the permeability decreases slowly,and the permeability incresses quickly.Thirdlly,sample coal samples on the Lu’an Changcun mine N3 workingface,and prepare four group coal samples(Φ50*70,Φ50*80,Φ50*90,Φ50*100).Acoustic emission characteristics test and three-dimensional positioning test under uniaxial conditions is developed with acoustic emission detector.The results are as follows:(1)The relationship between the stress time ringing and ringing accumulation of coal samples is better to reflect the deformation and breakage of coal samples.The acoustic emission pattern of the coal sample with smaller size is progressive,and the acoustic emission pattern of the larger coal sample is a jump type.(2)The acoustic emission energy can corresponding the number of the ringing.Under the condition of same diameter and different height diameter ratio,with the increase of height,the compressive strength of coal samples increases,but the cumulative number of acoustic emission energy decreases.(3)The acoustic emission localization effect of coal sample can be used to judge the trend and direction of coal sample crack generation and expansion,and to predict the failure surface of coal samples.