Underground mining methods: engineering fundamentals and international case studies. Hustrulid WA, Bullock RC, eds. Littleton, CO: Society for Mining, Metallurgy, and Exploration, 2001 Mar; :627-634
Ore passes are underground conduits for the gravity transport of broken ore, waste rock, and fill from one level of a mine to a lower level. Inclination of ore passes typically ranges from vertical to 30 degrees (Pariseau 1966), and cross sections may be square, rectangular, or circular. Historically, cross-sectional areas were generally less than 5.6 m2 (60 ft 2) (Peele 1947). In recent years, much larger ore passes have come into use, especially in conjunction with open-pit mines where run-DC-mine rock may contain boulders that are more than 1.5 m (5 ft) in size. Ore pass lengths range from 18 to over 180 m (60 to 600 ft), and undoubtedly there are even shorter and longer passes in existence. Fill passes from the surface may be exceptionally long. A level interval of 46 m (150 ft) is perhaps a representative ore pass length. Ore passes serve two important purposes: transport and storage. The latter is essential to efficient mine operation. Without adequate storage, any slowdown or stoppage in one part of a mine's transport system (for example, a train derailment or conveyor belt tear) could bring the entire system to a costly halt. If ore passes intended for transport and collection of ore do not provide adequate underground storage, then additional storage facilities must be installed. Surface storage bins also help to buffer mine and mill. Total storage needed depends mainly on the production schedules of mine and mill and are thus site specific. Components of the ore pass system include (1) the ore pass itself connecting (2) two or more levels in a mine; (3) top-end facilities incorporating material size and volume control mechanisms, such as grizzlies, crushers, and surge chambers; and (4) bottom-end structures to control material flow and enable loadout.