Optimization of drawing parameters based on top-coal flow law in thick-seam caving mining

With the continuous advancement of coal mining technology and widespread application of modern equipment, fully mechanized top-coal caving (FMTC) mining has become an efficient and economical option for thick coal seam mining. To study its coal drawing process, this paper takes the FMTC mining at Working Face 11508 of Xiejiagou Coal Mine in Guizhou as the research background. Via numerical simulation and bulk similar simulation experiments, it explores the law of top-coal drawing, recovery rate and gangue content under different drawing processes at the working face, clarifies the "window-closing" principle for drawing control, and optimizes drawing process parameters. Results show: When the mining-drawing ratio is 1:1, top-coal output is most balanced across steps; when it is 3:1, output difference is most obvious. The best top-coal drawing effect is achieved with a drawing step of 0.8 m and mining-drawing ratio 1:1.5 (1.96 m mined, 2.94 m drawn). At 1:1.5 ratio with 1-mining-1-drawing, though gangue content is higher, top-coal drawing rate is the highest and periodic output is stable. Strictly implementing the "close window when gangue is seen" termination principle in practice can achieve high top-coal recovery while controlling gangue content, providing guidance for thick seam FMTC mining.