Research on influence of coal seam thickness on caving characteristics of top-coal in inclined coal seam fully - mechanized caving faces

The coal seam at the 2125 fully mechanized top-coal caving face in Hebi Coal Mine No. 6 exhibits unstable occurrence, with a thickness ranging from 0.4 m to 24 m and a dip angle varying between 8° and 35°. To address challenges such as difficulties in top-coal caving, incoordination between coal cutting and caving, and high rates of gangue mixing during fully mechanized caving in inclined thick coal seams, a control variable method was adopted based on diverse coal seam occurrence conditions. Utilizing the CDEM numerical simulation software, a numerical model of the top-coal caving face with random particle distribution was established. The initial coal-rock interface morphology, developmental characteristics of top-coal caving bodies, and evolution patterns of the coal-rock interface were investigated under varying coal seam dip angles (25°, 30°, 35°) and top-coal thicknesses (6, 10, 15 m). Key conclusions are as follows: Under constant top-coal thickness, as the coal seam dip angle increases:The coal-rock interface near the upper end of the working face gradually elongates and flattens, while the interface near the lower end becomes steeper due to suppression by rock flow.The width of the caving funnel and single-cycle caving volume exhibit an approximately linear positive correlation with increasing dip angle.The initial caving body evolves from a near-vertical ellipsoid → quasi-circular ellipsoid → horizontal ellipsoid. Under constant coal seam dip angle, as the top-coal thickness increases: The caving body expands both vertically and transversely, with vertical growth exceeding transverse development. The inclination of the coal-rock interface intensifies with greater top-coal thickness. The caving funnel width shows an approximately linear positive correlation with thickness. Validation via numerical simulation and field trials: Caving volumes at individual outlets under sequential caving and interval caving modes were statistically analyzed, demonstrating consistency with numerical results.