Hazardous manifestation of gas-dynamic phenomena in the faces of coal mines

Abstract

The statistics of coal and gas outbursts in the faces of the Russian coal mines is provided. The mining-geological and mining-engineering conditions for the occurrence of sudden outbursts during the coal mining are considered, and the distinctive features in the factors of their occurrence and behavior are discussed. The criteria for identifying the potentially hazardous zones with the help of geophysical measurements are given. It is shown that it is important to take into account the data on the actual occurrence of outburst hazard in overlying and underlying longwall faces and development workings, as well as the results of the current forecast when preparing the extraction area for mining, as it follows from the results of underground investigations. The features are noted and the concept of the mechanism causing sudden coal and gas outbursts of faces is formulated. According to this concept, the probability of a hazardous situation is minimal at the beginning of the face advancement before the primary roof collapse. After the primary caving, the outburst hazard increases with the face advancement from the place of caving due to increased stresses in the bearing pressure zone, strengthening of the restraint of the nearest roof support, and the formation of a low permeable bridge in the coal seam near the exposed surface of the coal massif, which increases the pressure and free gas volume behind this bridge. The maximum degree of outburst hazard in the cleaning face is reached at the time of secondary roof collapses.