Quantifying Topographic Influences on Rockfall Trajectories in Open Pit Mines Using Stochastic Rockfall Modeling

ABSTRACT: Rockfall remains one of the most critical and least understood hazards faced in open pit mining. The factors controlling when and where rockfalls occur are abundant and highly variable site to site, hindering development of effective tools for proactive rockfall hazard mapping at scales relevant to mining operations. Observations from controlled rockfall tests on mined pit slopes conducted by NIOSH support previous studies, highlighting the significant influence of sub-bench-scale topographic features on rockfall trajectories. Specifically, bench face protrusions at a lower angle than the overall bench face, which tend to "launch" rocks into trajectories with greater horizontal velocity components. While often described by previous researchers, the phenomenon is rarely evaluated quantitatively. The influence of launch features on rockfall trajectories and kinetics can be evaluated using detailed stochastic 2D rockfall modeling. This study presents the preliminary results of such modeling, which focuses on primary rockfall impact distances beneath these launch features using 27 systematic combinations of launch feature widths, angles, and heights above the catch bench, with model parameters calibrated to the NIOSH rockfall tests. This analysis serves as a critical first step in creating generalizable, predictive rockfall hazard maps incorporating launch feature geometries mapped from as-built high-resolution pit slope surveys.