Safety analysis of Sormeh underground mine to improve sublevel stoping stability

In underground mines, sublevel stoping is used among a variety of different methods for mining an orebody, which creates large underground openings. In this case, the stability of these openings is affected by a number of factors, including the geometrical characteristics of the rock and mining-induced stresses. In this study, a sensitivity analysis was conducted with the numerical, squat pillar, and Mathews stability methods using the Taguchi technique to properly understand the influence of geometric parameters and stress on stope stability according to Sormeh underground mine data. The results show a full factorial analysis is more reliable since stope stability is a complex process. Furthermore, the numerical results indicate that overburden stress has the most impact on stope stability, followed by stope height. However, the results obtained with Mathews and squat pillar methods show that stope height has the greatest impact, followed by overburden stress and span. It appears that these methods overestimate the impact of stope height. Therefore, it is highly recommended that Mathews and squat pillar methods should not be used in high stope that is divided with several sill pillars. Nonetheless, Mathews method cannot accurately predict how the sill pillar impacts the stope stability. In addition, numerical analysis shows that all geometric parameters affect the roof safety factor, whereas the sill pillar has no significant influence on the safety factor of the hanging wall, which is primarily determined by the stope height–span ratio.