| Because coal has been China's energy constitute the largest proportion,the cause of the current coal mining in China has entered the stage of deep mining,the mining environment characterizes by " high ground stress,gas pressure,high gas content and low permeability ",which leads to coal rock dynamic disaster constantly;meanwhile,gas is also an unconventional natural gas resource.Therefore,it is particularly important to how to carry out deep mining and gas utilization in a safe,efficient and green way.The stress of coal bearing coal is mainly expressed as the composite effect of loading and unloading in the process of actual mining.Based on the previous studies,in this paper,No.2 coal in No.22301 working face of Tun Lan mine is the research object,using independent research and development of coal containing gas seepage experimental system for acoustic emission experiment of coal containing gas under different loading unloading conditions,the simulation of complex situation of actual mining,seepage characteristics and acoustic emission characteristics of coal containing gas,for the prevention and control of coal and rock dynamic gas disaster and provide a theoretical basis for more scientific.Specific research contents are as follows:(1)The conventional triaxial compression test:(1)? the deviatoric stress-strain curves can be divided into the compaction stage,the elastic stage,the yield stage and the failure stage;(2)?the overall change of permeability is as follows: continuous reduction?rapid increase?slow increase?stability and constant change;(3)?due to the Klinkenberg effect,with the increase of gas pressure,the maximum axial stress decreases,the permeability of the corresponding period of the first decrease and then increase tendency of "U",because of the effect of confining pressure,the maximum deviator stress increases and the permeability of the corresponding period decreased with the increase of confining pressure;(4)?the variation trend of the acoustic emission characteristic parameters corresponds to the change of stress and permeability respectively.(2)Uniaxial compression of different loading speeds:(1)? with increasing stress,acoustic emission activities increasingly actived,when instability damaged,acoustic emission activity was most intense,brittle failure stage of the acoustic emission activity sustained severe state,counting and amplitude values were high stage,after the failure of coal body acoustic emission signal to the sharp decline stage;(2)?with the increase of loading speed,the peak axial stress and the peak strain show a downward trend,and the failure mode is more serious.(3)The loading-unloading compression of fixed axial loading speed and change of unloading confining pressure speed: the overall change of permeability is: first decreasing?sharp increase?slow change and stable,which presents change trend of "V" type;with the increase of unloading confining pressure:(1)?peak axial stress decreases,radial strain and volume strain increase after failure,(2)?the time of the permeability to the minimum value increases rapidly and the peak area increases,(3)?the more active acoustic emission activities of coal bearing coal,the characteristic parameters of acoustic emission appears doublet peak phenomenon.(4)The loading-unloading compression of unloaded confining pressure speed fixed and axial loading speed change: the overall change of permeability is also: first decreasing?sharp increase ?slow change and stable,which presents change trend of "V" type;the characteristic parameters of acoustic emission are all doublet peak phenomenon;with the increase of axial loading speed:(1)?peak axial stress decreases,radial strain and volumetric strain increase after failure,(2)?the slower the permeability reaches the minimum value and the greater the peak area is,(3)?the more active the acoustic emission activity of coal is.(5)In different loading-unloading compression experiments,the variation rule of acoustic emission characteristics is basically corresponding to the variation law of stress strain and permeability of gas bearing coal.Therefore,acoustic emission can be used to predict the occurrence of coal and rock dynamic disasters. |
PDF Full Text Request