Summary

Problems of coal roof control occur when mining thick seams by layers from bottom to top with hydraulic stowing. These systems are used in the Polish Coal Mining Industry for the extraction of about 30 % of output which is the evidence of the importance of the problem. The coal roofs show the tendency towards delamination which is the effect of high petrographic differentiation of coal seams. The petrographic formations create the layers of a thickness from a few centimeters to a few meters. However, the seams of high petrographic heterogeneity are prevailing. The systems of coal roof control consist, first of all, in counteracting the delamination. In conventional systems this part was played by timber support left in extracted area. At the moment of passing on individual steel support the problem has been got under control through the use of rarefied timber support in the stowed area. The roof control has been made difficult as the complex mechanization of getting was being introduced with the use of powered support and powered dam. The tests made in such longwalls allowed the mechanism of delamination to be detected in state nascendi and the prevention methods to be tried out. Following systems have been tested: roof bolting with timber bolts, roof lagging with timber or metal net, rarefied timber supports and tight stowing. The results obtained allowed to put into words the modern economic principles of coal roof control.

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