Use of Probabilistic Numerical Modeling to Evaluate the Effect of Geomechanical Parameter Variability on the Probability of Open-Stope Failure: A Case Study of the Niobec Mine, Quebec (Canada)

Abstract

The inherent variability of the geomechanical parameters of a rock mass plays a critical role in affecting underground mine stability. Neglecting this characteristic of a rock mass oversimplifies stability assessment and provides potentially inaccurate results as the actual behavior of rock mass is not considered. Use of probabilistic methods in conjunction with numerical analysis is a reliable approach for evaluating the effect of geomechanical parameter variability on the different modes of underground instability. The degree of stability can be expressed by the probability of failure for different stress-induced instability modes. Here, we use probabilistic methods (random Monte Carlo and Monte Carlo simulations) coupled with the finite difference code FLAC3D to incorporate the variability of rock mass geomechanical parameters into numerical analysis. We assess the stability of seven existing primary open stopes at mining levels V and VI at the Niobec Mine, Quebec, Canada. The stability around each open stope is evaluated by calculating the tensile and compressive probabilities of failure, based on the Hoek–Brown tensile and compressive safety factor, and the probability of brittle damage initiation (PDI), via the brittle shear ratio. For the evaluated open stopes, tensile and compressive failures share similar probabilities of occurrence. Considering the PDI values around all the open stopes, no brittle failure is expected to occur under the existing conditions of rock mass quality and in situ stress regime at the Niobec Mine. Comparison of these probabilistic numerical model results with those run using a deterministic numerical approach highlights the effect of variability of rock mass geomechanical parameters on stope stability.