Powered support selection for longwall workings in dynamic load conditions

Abstract

Currently in Poland hard coal is mined in two Coal Basins namely Upper Silesian and Lublin. The Upper Silesian Coal Basin is located around the city of Katowice in the southern part of Poland. The Lublin Coal Basin is located in the south-eastern part of Poland, close to the Ukrainian border. In Poland, there were 30 underground hard coal mines that produced 72.5 million tons of coal in 2014. 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. In the paper, the most important data concerning the geological and mining conditions in Polish hard coal collieries were presented with particular emphasis on tremors, rock bursts and fatalities. Moreover, 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.