Findings of studies on wave character of pillar support pressure and edge parts of coal seams

Extraction of coal measures leads to origination of a large number of increased rock pressure zones in rock mass, caused by the influence of abutment pressure of rock mass edge parts and pillars kept in adjacent seams. The presence of such zones sharply worsens the condition of development and permanent workings when developing coal measures. The paper presents the findings of the observations made in the areas of the underground workings in coal mines of Karaganda coal basin, located under and above pillars and edge parts of overlying coal seams. If abutment pressure under pillars and edge parts of coal seams has been studied quite actively, abutment pressure above the pillars and the edge parts of the coal seams has not been practically studied. The findings of the performed studies showed that in all the workings in which the observations were made, the height of the workings located underneath the pillar (the edge part) varies wavily. The studies revealed wavily behavior of the stationary abutment pressure propagating along the seam, in which the working is located, according to the law of damped sinusoid while increasing distance from the source of the abutment pressure. At the same time, the half-wave length λ/2 corresponds to the thickness of the main roof above the working. The height of the workings located above the pillar (edge part) also varies wavily. At the same time, the nature of the abutment pressure influence varies depending on the distance of the working from the pressure source and is determined by undermining factor Ku. The abutment pressure half-wave length corresponds to the step of secondary collapse of the main roof of the coal seam on which the pillar (edge part) is located.