On methods of categorizing the outburst-hazardous of coal seams

Abstract

Abstract. Having analyzed the existing methods for categorizing the outburst hazard of coal seams the author worked out the proposals on improving the methodology for categorizing the outburst hazard of coal seams during their mining. The research methodology includes analysis of existing methods for categorizing of prone-to-outburst coal seams depending on the depth and speed of mining operations driving. It is established that the regulatory document on categorization of the prone-to-outburst coal seams needs to be updated in order to take into account possible manifestation of not only sudden outbursts of coal and gas, but also other known types of gas-dynamic phenomena and to specify the main criterion features and indicators, which should be determined quite simply and without significant time costs. Categorization of several coal seams was assessed: in some cases it depends on the grade of the seam (volatile content), but not always on the indicator M. An obvious defect of the obtained dependencies was found in the regulatory document (perhaps the reason is the lack of necessary data on the study of natural gas content and other properties and conditions for the manifestation of sudden outbursts of coal and gas). Thus, with indicators М = 24,5‑26,2 and М = 23,7‑27,6, critical value of natural gas content and the depth of prediction are the same. The authors of the regulatory document give no explanation to this fact as well as how and why, when determining the indicator for different dependencies, the same criteria of outburst hazard are obtained. The comprehensive studies on assessing a gas-dynamic state of potential prone-to-outburst zones in the threatened formations reveals that with greater depth of mining operations these zones should be timely transferred to the category of prone-to-outburst ones before the first outburst happens. In the paper, methods for referring the coal seams to the outburst hazard categories are discussed. It is concluded that the normative document needs to be revised in terms of categorization of prone-to-outburst coal seams with taking into account a more complete classification of all types of gas-dynamic phenomena. Keywords: categorization, outburst hazard, coal seam, sudden outbursts, normative document.