The influence of distant coal seam edges on seismic hazard during longwall mining

Abstract

Underground coal seam mining has been carried out in the Upper Silesian Coal Basin, Poland, for many years and with a simultaneous increase in exploitation depth. Frequently, coal seams are not fully extracted due to numerous reasons which lead to their edges and remnants remaining in the rock mass. Even in the case of the full extraction of a coal seam, mining usually ends at the border of a protecting pillar to protect underground or surface objects, sometimes at the border of themining area, or some distance from the old goaf or high throw fault. Extraction of subsequent coal seams in an analogous range results in a cluster of coal seam edges remaining. In the vicinity of the mentioned remainders, the disrupted stress distribution is expected. The infraction of the aforementioned equilibrium repeatedly results in the occurrence of strong mining tremors. The observations from the studied coal seam no. 408’s longwall panel indicated that mining works are able to disturb the present stress-strain equilibriumin the area of the edges of other coal seams, even if they are located at a greater vertical distance away. The seismological parameters and distributions have been applied for this purpose.