Methane hazard in high-productive coal mine

Abstract

Extensive underground mining of gas-bearing coal seams is carried out mainly in the Kuznetsk Coal Basin and the Vorkuta deposit of the Pechora Basin, where the coal sea m methane content is from 8 to 2 1.2 m3/t. At the average daily longwall productivity of 4100–13075 tons, methane emission in the longwalls varies from 18.8 to 113.1 m3/min. The influence of partings and longwall advance velocity in coal seams on the degree of natural degassing of contiguous seams is shown. The use of a package o f gas drainage methods and schemes in contiguous coal seams and in mined-out areas changes the structure of the gas balance in a mine. An increase in the rate of methane release into the mined-out void is associated with the main coal roof subsidence, which causes stress relaxation in contiguous coal seams and also contributes to fracture of strong floor rocks and to liberation of methane accumulated in the voids in the floor rocks. The current assessment procedure of methane hazard category of a mine based on the methane emission rate longwalls with high-performance coal mining equipment fails to meet mining safety by gas criterion. At high longwall outputs, methane content in longwalls decreases and, according to the accepted assessment procedure of methane hazard, puts them on a lower hazard level, which leads to the underestimation of the role of the gas factor in underground mining. It is recommended to classify methane hazard of high-productive coal mines by the absolute methane emission value.