The role of powered support in ensuring the proper longwall working cross-section area in rockburst-prone seams

In Poland, for underground hard coal seam extraction, the longwall method is used. Retreat longwalls with natural roof caving in the gob are the most common. Currently it is estimated that about a half of the hard coal output in Poland originates from seams located in areas of rock burst hazard. The article shows information about 18 rock bursts, and 14 other seismic events which occurred between 2003 and 2012 in underground mines belonging to one of coal companies in Poland. In addition, negative consequences of those dynamic phenomena in the longwall workings are described. In the next part of paper, the most common types of damage to powered supports after the rock mass tremors and other dynamic phenomena in longwall workings are shown. In order to avoid damage of powered supports, in geo-mining conditions where dynamic phenomena occur, different types of protective means are applied. In the paper the methodology of assessing the powered support yield ability is described. At the end, an example of the assessed yield ability of a powered support in given geo-mining conditions of a longwall face affected by the seismic events is presented