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| Diagram of a typical ore pass |
Background
Ore passes are constructed within the rock mass for the purpose of vertical transfer of ore and waste rock from stopes or development headings. Their function is to deliver material to a lower haulage level or to shaft loading pockets for hoisting to the surface. The figure shows a typical mine ore pass with truck loadout and LHD vehicle dump.
The ore pass design research was started at the request of MSHA after several fatalities resulted from workers attempting to free clogged ore pass chutes. A review of MSHA injury and fatality data for the 20- year period between 1975 and 1995 shows that nearly 75% of the injuries were directly or indirectly related to pulling or freeing ore pass chutes, the use of hand tools, falls of broken rock, and structural failures of the chute or gate and ore pass walls. During the period 1991-2000, 83 traumatic injuries specifically caused by pulling or freeing hang-ups in chutes were reported in 18 underground metal/nonmetal mines. In addition to ore pass accidents, about one fatality per year resulted from the collapse of coal bridges that formed over feeders on coal surge piles
Particle-flow computer programs have been used in analyzing mine ore and waste passes. Preliminary finite-element analyses determined safety factors of typical ore chute control gates. New algorithms have been developed to characterize ore pass materials and conditions more accurately and specifically, and results of numerical calculations on typical ore pass systems have been validated with experimental observations.
Potential Outcome
Improved ore pass design methods can prevent accidents caused by hang-ups and structural failures. Field tests indicated that particle size and shape and ore pass system stiffness and friction properties must be determined for accurate computer analysis. Highly sophisticated computer modeling routines were adapted as a design tool for mine ore pass designers.