Integrating time of exposure into quantitative evolving rockfall hazard assessment for open-pit mining

A quantitative Evolving Rockfall Hazard Assessment (qERHA) methodology is proposed to address rockfall risks in open-pit mines, integrating site-specific factors such as failure frequency, block size distribution, and highwall geometry. Unlike conventional approaches reliant on return periods, qERHA introduces a novel time of exposure (ToE) framework tailored to mining operations, enabling hazard assessment over durations ranging from hourly shifts to multi-year plans. The implemented energy thresholds reflect mining infrastructure vulnerabilities. The methodology employs stochastic rockfall trajectory simulations, geological layer segmentation, and Poisson-derived likelihood analysis to generate spatially explicit hazard maps. These maps identify critical zones for targeted mitigation and operational planning based on safety considerations. A case study shows how qERHA can be applied to investigate the likelihood of rockfall occurrence in the context of machinery operating at the toe of a highwall over a period of 3 months. Results indicate that targeted reinforcement of critical geological layers significantly decreases the likelihood of rockfall hazards. The study bridges gaps in existing qualitative and quantitative hazard assessments by incorporating mining-specific energy thresholds and ToE metrics, offering a practical framework for enhancing safety and operational efficiency in open-pit environments.