Mining technology and support optimization design of super high fully mechanized caving and small mining ratio in hard and extra thick coal seam

In order to realize the safety, high efficiency and high recovery rate mining of 9-13 m thickness hard coal seam in Jinjitan Coal Mine, the top coal recovery rate and coal wall stability of different cutting heights are analyzed by theoretical analysis and numerical simulation. Based on the corresponding relationship between top coal recovery rate, coal wall stability and cutting height, a super large mining height and small mining and drawing ratio technology which based on mining and supplemented by releasing is proposed. The ZFY21000/35.5/70D two pillar shield hydraulic support with super large mining height is developed. Based on the optimization design of anti impact column and high-efficiency caving mechanism, the problems of easy impact of super high mining height fully mechanized top coal caving face, easy rib spalling of coal wall and easy arching of hard coal are solved. Fully mechanized top coal caving mining with super high mining height and small mining and caving ratio is an effective way to improve recovery rate and realize high yield and high efficiency of extra thick hard coal.