Development and validation of a Novel rigid block modelling approach for support design in underground mining, enabling new avenues for improved safety and efficiency

Support systems are vital for worker safety and to minimize production delays due to collapse incidents or the need for rehabilitation. The purchase of support elements and their installation also represent a significant cost for the operational budget of any mine. However, current standard practices rely on empirical methods developed several decades ago or on simplified kinematic models of the rock mass and its interaction with the support system based on wedge analysis and key-block theory. Experience shows that these lack the robustness required for today's mining depths and safety needs. The advent of faster computer processors and new numerical modelling tools allows us to move away from these over-simplified methodologies and embrace new approaches that can more accurately simulate the failure mechanisms encountered and interactions between the rock mass and the support elements. A new methodology using the 3D distinct-element modelling software PFC3D, combined with DFN simulations, was developed to evaluate support system strategies at the Raglan Mine. The joint strength properties were calibrated against overbreak data from lidar scans. The study demonstrated the effectiveness of the Rigid Block Modelling-DFN approach in simulating complex failure mechanisms in a gravitational stress environment. It provided valuable insights into the trade-offs between using PM12 and rebar #7 for supporting the backs of drifts, as well as determining the optimal timing for installing secondary long supports at intersections.