Theoretical And Experimental Study On Unstable Failure And AE Characteristic Of Coal Contained Gas

Both unstable failure of coal contained gas and the coal and gas outburst are key problems in the process of coal mining. In this paper, triaxial gas seepage - creep of coal and Simulation Testing System of coal and gas burst are self-developed, and both the theoretical and experimental study on the unstable failure and AE laws under uniaxial compression, triaxial compression, cyclic loading, creep of coal or coal contained gas and simulation of coal and gas outburst were done, the Main research results as follows:1. Test equipment of triaxial gas seepage - creep and Simulation Testing System of coal and gas burst are self-developed.2. In order to investigate both the stress and stress paths-dependent of mechanical properties of coal contained gas, the experiment under different stress level and loading path are done. The results of experiment show: bigger stress sensitivity is had by mechanical properties of coal contained gas, and the obvious ductility and nonlinear characteristics are showed by coal because the gas exist.3. Based on experiments of triaxial compression and creep of coal and coal contained gas, both Four-section constitutive model under triaxial compression and creep constitutive model of coal and intrinsic time constitutive model under triaxial compressionand creep have improved K-B constitutive model of coal contained gas;the conception of secondary hysteretic curve is proposed.4. Experiments of AE in process of deformation under different stress and loading method of coal and coal contained gas are done and their characteristics are obtained. The results show: the characteristic curve of AE under uniaxial compression is similar to complete stress-strain curve of coal, hysteretic nature and double peak form are the obvious characteristic of the curve of AE under triaxial compression; the AE characteristic curve of coal contained gas under triaxial compression becomes gentle and present three peak form because of the existing of gas.5. AE characteristic of coal in process of deformation is simulated by the soft of RFPA. Based on results, damage constitutive equation of coal is built based on AE characteristic and damage mechanics theory, damage parameters are obtained according to event rate and energy of AE. 6.Based on experiments of mechanical properties, acoustic emission characteristics and results of sem study, effect of particle size are built.7. Based on the laboratory studies of AE in process of deforming coal contained gas and nonlinear theory, the nonlinear characteristic of AE in process of instability of coal contained gas is analyzed, the laws of Self-Similar parameter, fractal dimension, self-organization evolution are analyzed, the way of AE source location in which the velocity of AE signal is eliminated is built on one-dimensional and two- dimensional.8. Based on the laboratory studies of mechanical properties and AE in process of deforming coal or coal contained gas, grey-catastrophe model that is used to predict and judge the instability of coal contained gas is built according to grey theory and catastrophe theory, the result of predict and judge the instability of coal contained gas show by the model: the accuracy is higher.9. The result of coupling relationship between velocity of gas seepage and stress in process of whole deformation under three-dimensional stress shows: quartic curve expresses the coupling relationship between velocity of gas seepage and axial pressure under fixed confining pressure very well, and the velocity after instability of coal contained gas is bigger than before ; quadratic curve expresses the coupling relationship between velocity of gas seepage and confining pressure under fixed axial pressure;the effect on velocity of gas seepage caused by gas pressure before instability of coal contained gas is obviously bigger than after it; the effect on velocity of gas seepage of coal sample composed of different diameter coal particle decreases as diameter coal particle increase, the velocity of gas seepage of coal sample composed of big diameter coal particle is obviously bigger than small it under same conditions, and the conception of difficulty stress point of gas seepage is the gas seepage equation model is built based on fluid-solid coupling theory.10. Simulation Testing System of coal and gas burst is self-developed, and the experiments of coal and gas burst under same conditions or different ground stress and moisture content of coal are done, the results show: the characteristics which include diversification of loading mode, large-scale of outburst assembly, large open and close speed of outburst ostium, complanation of inflation-style, dynamic development of recording process and high precision ,high reproducibility, are posses; and the conclusions that both quadratic curve expresses the relationship between moisture content and intensity of outburst, improved logarithmic relationship expresses the relationship between ground stress and intensity of outburst are obtained.