Study On Coal Recovery Ratio In Fully Mechanized Top-coal Caving Face

The fully mechanized top-coal caving mining is one of the main methods of excavating thick coal seam. The top-coal recovery ratio is the key problem in full mechanized top-coal caving face, and improving coal recovery ratio is important to the development of the fully mechanized top-coal caving technology.Based on the analysis of influence factors of top-coal recovery ratio systematically, some key factors influencing top-coal recovery ratio in hard coal seam full mechanized top-coal caving face are calculated and analyzed by FLAC3D and UDEC. With FLAC3D, the stress and deformation distribution in top coal before and after hard top coal pre-blast weakening with different mining height during the advancing of the mining face is analyzed comparatively. The distortion, deformation and collapse characteristics of top-coal along advancing before and after top coal pre-blast weakening, with different mining height and different caving step are analyzed by UDEC. The study shows that, after the top coal pre-blast weakening, stress concentration is increased, the point of stress peak is moved forward, and the influence range is expanded. When the mining height is increased, the fracture degree is enhanced. It is superior to"mining twice and caving once"than"mining once and caving once".After the numerical simulation and the analysis, many technical measures such as hard top coal pre-blast weakening, increasing mining height and adopt suitable caving step according to the geology condition of the coal seam are proposed to improve the top coal recovery ratio in this paper.The field experiment is carried on in 40301 fully mechanized caving face of Dafosi Coal Mine, the coal recovery ratio is 80.4% in this experiment which gains favorable security, technical and economic effect.