Experimental Study On Damage And Gas Migration Of Coal Under Adsorption-Sudden Unloading Methane

Coal and gas outburst is a complex dynamic instability process,which is a scientific problem of multi-field coupling such as stress field and gas flow field.Under the influence of the mining effect,the original stress state in the coal seam is destroyed,resulting in changes in the pore-fracture structure and the desorption/adsorption state of the coal to the gas.The state of gas occurrence,especially the change of gas pressure,will affect the mechanical properties of the coal.Coal and gas outburst are the result of the coupling between coal damage and gas desorption.Therefore,it is of great theoretical and practical significance to study the mechanism of coal body damage and gas desorption-seepage coupling in the prominent process.In this paper,based on the theory of gas,coal mechanics and damage characteristics,microstructure,gas desorption,gas seepage mechanism and other theoretical and basic experiments,the experimental study on coal damage and gas desorption-seepage coupling under sorption-sudden unloading of methane is carried out.Analyze the damage of the coal during the protruding process.To study the characteristics of deformation and failure of coal at the instant of coal and gas outburst,we developed an experimental apparatus for subjecting coal samples to sudden unloading under differing gas conditions.The apparatus consists of coal sample cell,fast pressure unloading system,monitor and control system and a gas filling system.Through the reliability verification test,it is found that the test equipment guarantee,pressure relief performance and sensitivity can meet the experimental requirements.It can carry out the adsorption-sudden unloading of gas test of various coal and rock mass under different pressures or different adsorption gas,and it can control the gas pressure unloading speed according to the actual situation,which provides the experimental conditions for the research.Through the comparison test of different gas conditions,the deformation process of coal sample in the environment of adsorbed gas and non-adsorbed gas was analyzed.At the same time,the parameters such as deformation,deformation rate and damage degree of coal sample in gas adsorption and sudden unloading test were analyzed.The damage and gas migration law of coal in different gas environments and different gas pressures are obtained.Through the experimental study on the adsorption-sudden unloading of gas in different pore structure coal,the mercury intrusion experiment was first carried out,and the influence of the coal powder ratio of different particle sizes on the pore parameters of briquette was obtained.At the same time,by comparing and analyzing the variation of ?v??r??z,the kinetics of gas and the damage degree of coal sample in five groups of experiments,the deformation and damage of coal with different pore structure under gas adsorption-sudden unloading methane were obtained.The above research results have certain significance for the prediction and prevention of coal and gas outburst disasters,and help to promote the exploration and development of coal and gas outburst mechanism.