Study On The Test Experiment Of The Shatter Proneness Of Coal Containing Gas And Its Characterization Index

Coal and gas outburst,and rockburst are both serious dynamic disasters in coal mines.The main difference between them is that there must be high pressure gas in the coal seam when outburst happened.And outburst usually brings out a large amount of shattered coal,some of which has even been pulverized.While these phenomenon don’t occur in rockburst.It indicates that the high-pressure gas plays an important role in coal shatter during outburst process.In order to verify that the coal containing gas can be shattered when it is suddenly unloaded,a device testing the shatter of coal containing gas was developed independently,and the experiments of various coal samples under different gas pressure conditions were carried out by using this device.The particle size distribution of the shattered coal,the shatter proneness indexes of the coal containing gas,the shatter cause and its occurrence conditions were obtained.And the relationship between the shatter proneness indexes and the outburst influencing factors was further analyzed.The device is a horizontal pressure vessel,and its opening is sealed by a rupture disc,which can achieve the purpose of pumping air,inflating gas and instantaneous pressure relief.By observing the shatter situation of 8 kinds of coal samples under different gas pressure conditions,it is found that only under the action of gas pressure and the gas pressure is high enough,most of the coal containing gas can be shattered when the pressure is suddenly relieved.For the same coal sample,the higher the gas pressure,the more severe the shatter of coal.Different coal samples have different shatter degree under the same gas pressure-There is basically a minimum shatter gas pressure pmin for each coal sample.The shattered coal obtained from each experiment was collected,sieved and statistically analyzed.The results show that the particle size of the shattered coal follows the Weibull distribution,and its shape parameter k and characteristic particle diameter d,can represent the shatter degree of coal under a specific gas pressure conditions.The further study shows the pmin value of the coal and the de value under the specific gas pressure were selected as the shatter proneness indexes of the coal containing gas.The smaller the two values,the more likely the coal is to be shattered.Based on the experimental conditions,the relevant model was established.Through theoretical analysis,it is concluded that the reason for the shatter of coal containing gas is mainly related to the gas pressure and the unloading wave formed after the external gas of coal block was relieved suddenly.When the stress intensity factor at the long axis end of the pore and crack or the effective tensile stress generated in the coal reaches its critical value,it will cause and accelerate the expansion destruction of the pore and crack,thereby causing coal damage.Through the dimensionless analysis of the control factors causing coal damage in the outburst process,it is proposed to use the shatter proneness indexes of the coal as a one of the main indicators to identify or predict the outburst dangerous.This has certain reference value to the research work of outburst mechanism and prevention technology.