Mechanism of support crushing and prevention-control technology in fully mechanized top-coal caving face in extra-thick coal seam

In response to the frequent occurrence of support crushing accidents during mining in extra-thick coal seams, this study takes the 5106 fully mechanized top-coal caving face of a mine in the Huangling mining area as the research object, systematically analyzes the support crushing mechanism, and proposes comprehensive prevention and control techniques. The research indicates that support crushing accidents are primarily triggered by the coupling of multiple factors, including instability of overlying giant concentrated coal pillars, energy transfer from key stratum fracturing, deterioration of roof stability, and coupling failure of the support-surrounding rock. Through structural analysis of rock strata and dynamic monitoring of support pressure, the dominant roles of dynamic pressure from coal pillars and key stratum breakage on strata behavior are revealed. Accordingly, prevention and control measures such as surface fracturing for distress relief, trinity mine-pressure monitoring and early warning, and optimization of mining and top-coal caving technology are proposed. Application results show that after implementing the prevention and control measures, the periodic weighting intensity of the working face was reduced by 41%, the cost of handling support crushing accidents was significantly decreased, and the advancing efficiency was improved by more than four times.