Roof stability of large-area point pillar upward horizontal cut-and-fill stopes

This study conducted an in-depth investigation into the roof stability characteristics of large-area point pillar stopes at the Dahongshan Copper Mine. The research revealed that as the sublevel height and mining scope increased, roof safety hazards became progressively more severe, posing significant threats to the safety and stability of mining operations. Focusing on the roof of stopes in the unmined areas of the mine, this study comprehensively employed catastrophe theory and numerical analysis to assess the roof safety conditions and evaluate the risks associated with continuing extraction using the current mining methods. The analysis indicated that the point-pillar upward cut-and-fill method was feasible and effective for the 180 m sublevel at Dahongshan Copper Mine when the mining height was below 70 m. However, when the extraction reached heights of 80-90 m, stress concentration in surrounding unmined areas led to increased roof safety risks. At the full 180 m mining height, the plastic zone of the roof increased by nearly 100%, with a failure height reaching 10 m. Continued application of this mining method under these conditions would present serious safety challenges.