Abstract
In view of the difference of the adsorption structure between soft and hard coal, there is a big difference in the critical value of the inspection index for the regional outburst risk caused by the gas content. For the coal seams with soft and hard coal stratification, the model of gas content in the equilibrium state was established first, and the microscopic parameters of different rank coals were determined by the low-temperature liquid nitrogen adsorption test and mercury intrusion test. Then, the adsorption capacity of coal samples was determined by the adsorption test. Finally, the residual gas content of the coal seam in the equilibrium state was calculated based on the adsorbed gas content, and the critical value of prediction indexes of regional outburst based on the residual gas content was studied. The results show that for the same metamorphic degree, the specific surface area of soft coal is larger than that of hard coal. However, under the same gas pressure, the residual gas content of hard coal of anthracite and lean coal is greater than that of soft coal with the same metamorphic degree, while that of meager-lean coal and gas-fat coal is opposite. It is suggested to adopt the small value (rounded) of the measured gas content of soft and hard coal at 0.74 MPa as the critical value of the residual gas content in the regional effect test from the economic perspective. It is of great significance to determine the critical standard of the residual gas content in the regional effect test according to local conditions for reducing the cost of outburst prevention work.
Highlights
In China, the Regulations on Prevention and Control of Coal and Gas Outburst stipulates that the critical values of gas pressure and gas content should be 0.74 MPa and 8 m3/t, respectively, without experimental investigation.[1]
When the soft and hard coals coexist in the coal seam, the prediction of coal and gas outburst is carried out according to these critical values, and it is found that the prediction index is not sensitive and the critical value is unreliable sometimes.[2−5] Many coal seams in mines often contain soft and hard coal stratification
There are significant differences in mechanical characteristics and permeability between soft and hard coal.[6−9] The mechanical strength of soft coal stratification is low, which is a prominent breakthrough point.[10−12] based on the difference of adsorption structure between soft and hard coal, it is of great significance to study the critical value of the inspection index for the regional outburst risk caused by the residual gas content when soft and hard coals coexist
Summary
In China, the Regulations on Prevention and Control of Coal and Gas Outburst stipulates that the critical values of gas pressure and gas content should be 0.74 MPa and 8 m3/t, respectively, without experimental investigation.[1]. There are significant differences in mechanical characteristics and permeability between soft and hard coal.[6−9] The mechanical strength of soft coal stratification is low, which is a prominent breakthrough point.[10−12] based on the difference of adsorption structure between soft and hard coal, it is of great significance to study the critical value of the inspection index for the regional outburst risk caused by the residual gas content when soft and hard coals coexist. Mastalerz et al.[24] considered that the average limit adsorption value of soft coal is 21.26%−74% higher than that of the primary structure coal This leads to the phenomenon that the coal seams with soft and hard coal stratification cannot eliminate the outburst at the same time when the effect of outburst prevention measures is tested. The relationship model of related parameters is established, and the critical value of the inspection index for the regional outburst risk caused by the residual gas content is studied
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