Orepass geotechnical rating evaluator adapted from existing orepass longevity calculator

Abstract

This article presents an orepass geotechnical rating evaluator (OGRE) developed to help geotechnical and mine engineers assess the geotechnical risks of proposed orepass locations. Orepasses (near-vertical excavations that transport ore by gravity) are integral to many underground stope mining methods that rely on centralized haulage levels. Despite their importance, orepass designs are often not finalized during planning stages, and their longevity can be compromised by geotechnical conditions. The evaluation method presented is adapted from an existing orepass longevity calculator. Operational considerations, such as material size, blasting practices, cushion guidelines, and support or liner use, were removed, while new geotechnical parameters (sulfide-generating potential, orientation of finger raises, intersection angle of finger raises, and rock quality clarifications) were incorporated based on insights gathered from a survey on orepass planning, design, and construction practices in Canada and the United States. This allows the OGRE to consider stress regime, rock quality, geological structures, sulfide-generating potential, orepass orientation, and finger raise or knuckle use. The resulting tool enables comparison of orepass location options based on geotechnical risk. The value of each of the six aforementioned parameters individually ranges from as low as 0.05 up to 1.00, and they are multiplied together to produce a final rating between approximately 0 and 1. If an orepass location option has a number closer to 1.00, it would indicate less geotechnical risk. Furthermore, this article also identifies methods of managing geotechnical risk through design modifications for orepass locations identified as high risk.