The interaction between face support and surrounding rock and its rib weakening mechanism in hard coal seam

This study was conducted in a closed system comprising the roof, near-wall coal, support, and floor at a coal face in a hard coal seam, aimed to find a way to overcome the difficulty of cutting hard coal. Energy analysis was applied to analyze the interaction between face support and surrounding rock. Based on this, effective weakening of hard coal ribs was achieved by lowering the setting load of the face support to an appropriate level. Expressions for the strain energy stored in the support rock system and the work done by external forces in the system were derived from the deformation characteristics of the system. Moreover, a stability criterion for the support rock system was obtained according to the principle of minimum potential energy. It reveals the negative relationship between the length of plastic and the length of the elastic zone in the near-wall coal. In addition, the relationship between the support force and the length of the plastic zone was obtained, it reveals through properly reducing the setting load of face support can enlarge the plastic zone and the weakening degree of hard coal ribs. The actual production at the coal face No. 8706 in a hard coal seam at Xinzhouyao Coal Mine, Datong mining area, showed that a proper reduction in the setting load of the face support led to enhance rib weakening effect, increases in shearer haulage speed and coal output, mitigation of hard roof weighting, and lower support resistance.