A Risk-Based Pillar Design Approach Combining Stochastic Continuous and Discontinuous Modeling in an Underground Stone Mine

The collapse of a mine pillar is a catastrophic event with great consequences for a mining operation. In spite of the low probability of occurrence for a pillar collapse in comparison to other ground control instability issues, these consequences make these events high risk. Therefore, the design of these structures should be considered from a risk perspective rather than from a factor-of-safety deterministic approach, as it has been traditionally done. This work presents a risk-based pillar design framework that enables to characterize discontinuities' effect in pillar strength, as well as accounting for the possible range of stresses that will be acting on pillars. The proposed methodology is based on the integration of stochastic discrete element modeling for pillar strength estimation, and stochastic continuous modeling for pillar stress determination. This approach was evaluated in an underground dipping stone mine. Using the reliability analysis method, results from the stress estimation model were integrated with those obtained from the stochastic DEM approach, thereby enabling the probability of failure estimation for the pillars throughout the mine. Finally, the methodology was validated by comparing numerical modeling results with LiDAR and photogrammetric surveys from the mine. Results from this design framework provide additional decision-making tools to prevent pillar failure from the design stages by reducing uncertainty. The proposed method enables the integration of pillar design into the risk analysis framework of the mining operation, ultimately improving safety by preventing future pillar collapses.