Movement laws of overlying strata and prevention measures of dynamic disasters under deep adjacent coal seam group with high gas

Abstract

The repeated mining of deep adjacent coal seam group with high gas has great influence on strata behaviours and dynamic disasters in underground mining. In this paper, the movement of overlying strata and gas for bi-level mining are studied, and then the effective methods of prevention and control disasters with consideration to the ‘time-space-strength’ is put forward. The results show that after the completely mining of upper coal seam and the lower coal seam been mining, the layers between coal seams move substantially and the tensile stress increases significantly, resulting in the overlying rock fissures are connected. Then, the stress of lower coal seam reaches peak value, and the dominant gas flow channel is formed, thereby causing in strong dynamic pressure phenomena such as increase in the gas pressure. After this, the self-developed gas sealing flexible air bag is used to block the gas in the position of face corner and to drain the gas in the goaf, which can effectively prevent gas outburst. The study results are of great significance and provide guidance to prevent dynamic disasters (i.e. gas outburst) caused by the repeated mining of adjacent coal seams.