Vestnik Naučnogo Centra po Bezopasnosti Rabot v Ugolʹnoj Promyšlennosti (Jun 2018)
MODERN OPPORTUNITIES FOR A COAL SEAM GAS CONTENT FORECAST AT THE PREPARATORY OPENINGS’ HEADING
Abstract
Research work results in the field of methane inflow forecasting at the preparatory opening heading through coal seams with high gas content and their gas content clarification were given.Clarification of residual gas resources in the seam before the beginning of the preparatory workings heading or working out of the extraction pillar, especially in the presence of significant deformation processes in the immediate vicinity due to man-caused activity, is an important task, since the gas barrier is the main constraint to increasing the productivity of mining and heading works in coal mines.The paper describes the geomechanical situation near the research object (western track inclined gallery 401) and the processes that caused the low methane inflow of the preparatory openings and played a significant role in reducing the natural gas content of seam 4 compared to the values provided by the geological survey of the mine.For the methane inflow forecast at the preparatory workings heading, the method of analogue openings was applied. As a result of the method, the average daily methane inflow of the western track inclined gallery 401 without use of barrier boreholes is expected to be no more than 1 m3/min. The calculated value is almost 2 times lower than the actual values established during the preparatory workings’ heading through the seam 5, and with a difference in the natural gas content of the seams by 25%. This fact indicates that the seam 4 in the vicinity of the western track inclined gallery 401 was subject to partial degassing. This degassing nature understanding goes beyond the classical notions of a rock massif displacement processes when the seam is underworked. The coal sampling to clarify the natural gas content also indicates significant degassing of the seam 4.The presented results indicate that with the long-term (more than 15 years) unloading of the coal seam caused by its underworking, significant degassing takes place, which goes beyond the geomechanical angles of unloading (shifts) specified in the relevant regulatory documents, and probably caused by its gas shrinkage.
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