Mathematical Model Of The Permissive Coalbed-Gas Content And The Minimum Gas-Preextracted Ratio For Safe Coal-Mining

Which degree does coalbed gas (CBG) is pre-extracted to so that safe coal mining can be just assured? Heretofore, a unambiguous respondence or evaluating solution to the question is absent in China and other countries. Thus, based on the geologic evolution, from tectonic framework and sedimentary environment, the formation and distribution law of coal gas in mine area, wre comprehensively discussed. It was researched that the influencing factors on the mine gas concentration were geological structure, carbonification, coal seam thickness variation, coal structural factors, and so on Mining factors of the mine gas concentration. Taking the relative provisions of National Coal Mine Safety Regulations as a pilot, the authors in the paper developed a mathematical model for computing the permissive CBG content (PCBGC) in the lights of some factors such as CBG geology, mine-gas, coal-mining activity and mine ventilation & safety, suggested some new concepts such as permissive CBG-desorbed quantity (PCBGDQ), and estimate further the PCBGC and PCBGDQ from 34 units of six coal-mining districts in China. The results show that the average value is 0.8999 m3/t for PCBGDQ and 6.1444 m3/t for PCBGC, which indicates that the upper limit provision of the gas concentration for the prevention of coal-mine gas explosion in the districts can be appeased in general. The authors suggested that there is no uniform PCBGC standard in whole country but the PCBGDQ and gas-preextracted ratio could be a key for establishing the standard of mine gas safety.