Underground methods of extraction of thick coal seams—a global survey

Abstract

Thick coal seams, despite the lack of a precise definition and varying national norms for classification, constitute some 30 percent of the global resource endowment in coal. The exploitation of such thick seams by underground methods offers a challenging task, posing as it does a host of problems related to production concentration, spontaneous heating risk, safety and recovery. The current status of the diverse exploitation techniques in different coal basins worldwide is critically appraised and the available database for thick seam reserves and norms of classification, besides contributions from different methods and roof control techniques, are presented and analysed. The paper sets out to review the highlights of technological developments in room and pillar thick seam mining, single pass longwall, multislice longwall, underwinning and hydraulic mining methods in order to help identify the more promising thick seam methods for the near-term future. The strategy of advancing the state-of-the-art of thick seam technology is also briefly examined.