Abstract: To avoid support crushing disaster again in No. 1602(3) working face of improving upper limit with hard roof in Panyi coal mine, Huainan, based on the similar simulation results, the fracture characteristics of overlying strata were studied, the structure mechanics model of overlying strata were established, the critical support resistance was deduced, the instability criterion of support crushing was determined, and the factors influencing critical support resistance of support crushing were further analyzed. The results prove that these measures such as reducing working face length, lowering mining height, keeping the integrity of immediate roof, preventing large hanging roof in the gob, strengthening the coal wall, hydrophobic step-down before mining, etc. can be in favor of the stability of support in the working face of improving upper limit with hard roof. On this basis, further prevention countermeasures of support crushing such as forced caving, high-grade conventional mining, reasonable equipment selection, etc. were proposed, which were applied to the modified No.1602(3) working face successfully, and good economic benefits were obtained.

Key words: working face of improving upper limit, hard roof, critical support resistance, instability criterion of support crushing, prevention countermeasures of support crushing