An Application of a Computer to Open-Pit Mine Design

General: National Asbestos Mines Limited has operated an asbestos mine and mill near Thetford Mines, Quebec, since 1958. As a result of additional exploration of the orebody in 1962-63, it became apparent that long-range mining plans would have to be revised to allow for a large increase in both ore and waste tonnages. It was decided that the task of checking out possible mine designs could best be analyzed by a computer to obtain data from which an optimum open-pit configuration could be plotted. Object: It was desired to arrive at an optimum open-pit configuration with an over-all pit slope of 45 degrees and a minimum operational width of 200 ft. at the bottom. Calculations were based on assay values from diamond drill holes in cross sections of the mine. The computer's assignment was to select and describe, by coordinates, the optimum cross section for the mine. Mine engineers then assembled the various optimum sections to produce the pit outline. As this would not necessarily result in a practical mining arrangement, the computer also provided alternate solutions,