Arch structure effect of the coal gangue flow of the fully mechanized caving in special thick coal seam and its impact on the loss of top coal

Based on the characteristics of the top coal thickness of the fully mechanized caving in special thick coal seam, the long distance of coal gangue caving, as well as the different sizes of the coal gangue broken fragment dimension and spatial variation of drop flow, this paper uses laboratory dispersion simulation experiment and theoretical analysis to study the arch structure effect and its influence rule on the top coal loss in the process of coal gangue flow. Research shows that in the process of coal gangue flow, arch structure can be formed in three types: the lower arch structure, middle arch structure, and upper arch structure. Moreover, the arch structure has the characteristics of dynamic random arch, the formation probability of dynamic random arch with different layers is not the same, dynamic random arch caused the reduction of the top coal fluency; analyzing the dynamic random arch formation mechanism, influencing factors, and the conditions of instability; the formation probability of the lower arch structure is the highest, the whole coal arch and the coal gangue arch structure has the greatest impact on top coal loss. Therefore, to prevent or reduce the formation of lower whole coal arch structure, the lower coal gangue arch structure and the middle whole coal arch structure is the key to reduce the top coal loss. The research conclusion provides theoretical basis for the further improvement of the top coal recovery rate of the fully mechanized caving in extra thick coal seam.