Annualised Probabilities of Pit Slope Failures Using Two Methods

A novel framework for assessing the annualised probabilities of slope failures in open-pit mining is presented by integrating traditional geomechanical models with a comprehensive semi-quantitative assessment of multiple sources of information available for the pit design. The methodology is developed through a comparative analysis of two distinct methods applied to a real-world case study, allowing for a deeper understanding of slope failure probabilities and their implications for risk management. The paper emphasizes the importance of moving beyond conventional adimensional probability of failure (APoF) definitions to estimate annualised probability of failure (PoF) values. A novel quantitative methodology is introduced to estimate the annual PoF of slopes based on geomechanical values, incorporating considerations of slope lifespan and factor of safety (FoS). Additionally, ORE2_Slopes is presented as an alternative semi-quantitative probabilistic evaluation method, and its estimates are compared with literature benchmarks and real- life pit experiences. The study highlights the significance of estimating annualised PoFs for quantitative risk assessment (QRA), considering various parameters such as time dependency, human factors, and monitoring for a comprehensive risk evaluation. The methodology aims to provide a unified framework that balances geomechanical considerations with expert judgement assessments, offering practical tools for informed decision-making in open pit designs.