Regularity of methane migration of heavy steep-thick coal seams in top-coal caving workings and comprehensive control
Top-coal caving in heavy steep-thick coal seams with short-distance workings is one of key approaches for fully recovery of coal resources. However,movement of rock masses is complicated. In high sectional top-coal caving it often occurs hazards of abrupt methane release,problems of exceeding methane and potential methane disasters. For hybrid control to methane problems in top-coal caving of Wudong colliery,the theory analysis,parameters testing and in-situ experiment are adopted with remarkable effects,which indicated that the methane pre-drainage rate was up to 5. 8% in B4- 6and methane concentration maintains 0. 02% in tail-entry. Besides methane draining amounts reached 23 900 m3with mining in working face which was 67. 55% of total ones,which was prerequisite to achieve safe and efficient excavation in extremely thick and steep coal seams.