Research On The Multi-scale Mechanism Of Coal And Gas Outburst And Continuance

In order to study the mechanical conditions of that coal and gas outburst develops and lasts in drifting tunnel, experiments on adsorbed gas-coal under different temperatures and pressures by WY-98B adsorbed gas-coal coefficient apparatus are conducted with considering major factors of coal and gas outburst. Unaxial and triaxial compression tests of coal samples are also conducted with MTS8150.4 electro-hydraulic triaxial servo testing system, which test results are analyzed for strength distributions of the samples. According to the experiment results and theoretical analysis, multi-scale mechanical conditions of that coal and gas outburst develops and lasts are presented. The main conclusions are as follows:(1) The adsorption isotherms of different coal samples are different. In normal mode, adsorption constants, a as well as b, decrease as the temperature increase. With the increase of the temperature, the quantity of adsorbed gas-coal decreases. With the increase of the pressure, the quantity of adsorbed gas-coal has significant change. When the temperature-change trend are same, adsorption constants-change trend of different coal samples are different.(2) Because of the randomness of coal samples, the brittle fracture strength distributions of coal samples appears non-uniform and the brittle fracture strength of different coals also have obvious difference. Regarding fracture strength of coal samples, compare with Weibull distribution, approximate normal distribution can clearly explain stress concentration of coal samples in a certain range.(3) On basis of the spherical shell destabilization theory and experimental law, multi-scale mechanical conditions of adsorbed gas-coal are presented. The predicted probability density function of coal and gas outburst under different temperature and pressure are also provided.(4) In the process of coal and gas outburst, probability density of two phase flow that consists of broken coal and gas as well as energy distribution density in roadway both decrease with the distance increase from the center of coal rock outburst. With increase of original pressure, outburst potential energy of two phase flow increase, and outburst potential energy-change trend is more obvious. With increase of temperature and pressure, coal and gas outburst can easily develop. If outburst potential is larger than zero, outburst can last. Otherwise, outburst is not easy to develop.