Study on occurrence mechanism and monitoring and early warning of rock burst caused by hard roof

According to the high frequent occurrence, high strength, wide destroy scope and other problems occurred by the mine pressure bump under the condition of the hard roof, based on No. 1411 coal mining face in Huafeng Mine as an engineering background, the theoretical analysis was firstly applied to study the occurrence mechanism of the mine hard roof type pressure bump and then to analyze the acoustic emission and stress precursory information features of the hard rood type coal mining face. Finally the site practices were conducted. The study results showed that the mine hard roof type pressure bump was mainly based on the energy and stress criterion, the precursory information of the mine pressure bump mainly would have two features and they were the energy increased and stress sudden changed. A long free span of the hard roof would cause the concentrated stress continuously increased internally in the coal mass. Once the accumulated great elastic energy could not be effectively and softly released, a mine pressure bump would be possibly occurred. The acoustic emission and the stress monitoring means could be applied to timely obtain the coal stress and energy dynamic development conditions during the mining process of the hard roof type coal mining face. Thus the early warning could be conducted on the mine pressure bump danger. In combination with the site conditions, a large diameter borehole and deep borehole roof cutting blasting was designed and applied to the pressure released and the danger solved. Before and after the pressure released, the maximum drilling cuttings were reduced from 4 kg/m to 3 kg/m, the stress concentration parameters would be reduced from 2.03 to 1.72, the support pressure peak could be migrated to the deep section, the stress concentration of the coal would be obviously released and the pressure released effect would be good.