Numerical Model Calibration Method for Overburden Collapse in an Underground Stone Mine using FLAC3D

ABSTRACT: A catastrophic pillar system failure occurred on the upper level of an underground stone mine (Mine A) in the eastern United States, leading to the collapse of the overburden with surface disturbance. RESPEC was engaged to perform a detailed post-failure analysis. To accurately represent the geomechanical behavior of the overburden, RESPEC developed an innovative calibration methodology to determine mine-scale material properties using FLAC3D. This approach involved iterative adjustments and validation against observed failure mechanisms, ensuring that the numerical model closely replicated field conditions and failure patterns of the overburden. By refining the material properties and calibration process, the model provided enhanced insights into the complex interactions governing overburden stability and collapse in room-and-pillar stone mining environments. This paper discusses the calibration process comprehensively, highlighting the key steps, challenges, and lessons learned during the analysis. The proposed methodology offers a reliable framework for improving predictive accuracy in numerical simulations and can be applied to similar underground mining scenarios for risk mitigation and design optimization.