Experiment on permeability features of gassy coal under pressure relief condition

In order to study the permeability of gassy coal seam under different pressure relief condition,pressure relief tests were conducted on the gassy coal under different surrounding pressure,different gas pressure and different pressure relief speed combined condition to simulate the geostress,gas pressure and the gassy coal per meability features under the influence of mining intensity. The test results showed that under the condition of surrounding pressure and pressure relief speed unchanged,th e higher surrounding pressure was,the higher coal gas permeability would be. Under the condition of gas pressure and pressure relief speed unchanged,the higher surroun, ding pressure was,the lower coal gas permeability would be. Under the condition of the gas pressure and surrounding pressure unchanged,the coal stability lost and failure process would be speeded up with the pressure relief speed rate increased and the permeability would be increased with the pressure relief speed rate increased.