of the fully-mechanized sub-level caving full-seam mining with high bottom cutting height for the 20 m very thick and medium hard seam have been studied by 1∶30 physical simulation.

Based on the practice of the worksite with extra hard thick seam fully mechanized mining coal caving, the pattern of activities of the roof using fully mechanized mining coal caving located in Jincheng mining area 3 # seam, caving techniques and parameters are analyzed and summarized.

After analyzing fully-mechanized sub-level caving technology in the case of special thick and hard coal seam, it is presented that the increment of cavability of hard roof coal and available control of gas are the main difficult technology problem to be faced.

Manufacture of fully-mechanized sublevel caving hydraulic support for hard and superhigh seam;