Research on the Law of Top Coal Movement and Influence Factors of Coal Caving Ratio for Fully Mechanized Top Coal Caving Working Face

To investigate the movement law of top coal and the influencing factors of coal caving ratio in fully mechanized top coal caving faces, this study adopts the theory of dispersoid mechanics. First, a top coal flow model was established without considering the influence of the support. Then, the effect of the support was analyzed, and it was found that the sliding resistance of the top coal body increases with the square of both the support width and the top coal thickness. Furthermore, the positive stress on the coal particles was derived through a microelement force analysis, and a theoretical formula for arching probability was proposed. The mobility of top coal was evaluated using a flow factor, and the influence of lump size on arching tendency was quantitatively analyzed. Based on these insights, several measures to improve top coal flowability and recovery rate were proposed, including increasing mining height, enlarging the coal caving opening, enhancing the initial support force, extending the caving step, and applying multiple alternating loads to pre-break top coal. These strategies provide a theoretical basis and practical guidance for enhancing top coal caving efficiency.