Numerical and theoretical investigations of the effect of the gangue-coal density ratio on the drawing mechanism in longwall top-coal caving

Abstract Discrete element calculations of the top-coal drawing process for different gangue-coal density ratios were conducted to investigate effect ratio on mechanism in longwall caving. The effects analyzed body, boundary, and recovery top coal. results show that increasing ratio, initial body goaf side is farther away from support its width volume gradually increase. upper part sickle-shaped extends near with normal cycling stage, distance maximum width. larger smaller height coal above at end process. boundary decreases until it reaches a limit. In cycle, due hysteretic development, moves toward approximately 2.0, which consistent physical experiment results. Finally, advance length working face beneficial overall