Borehole (Slurry) Mining of Coal, Uraniferous Sandstone, Oil Sands, and Phosphate Ore.
This paper reviews advances in the art of borehole (slurry) mining made by the Bureau of Mines from 1974 to 1980. The design of a prototype borehole-mining tool (bmt) developed by the Bureau of Mines is presented along with production data, reclamation data, and an application of the bmt to the mining of coal, uraniferous sandstone, oil sands, and phosphate ore. The bmt was first used near Wilkeson, Washington, where steeply pitching metallurgical coal was mined at 8 st/h from a depth of 25 to 75 ft. Next, 940 st of uraniferous sandstone was mined at 8 st/h from a depth of 75 to 100 ft in Natrona County, Wyoming. One thousand short tons of oil sands was mined in Kern County, California, at the rate of 14 st/h from a depth of 110 to 150 ft in 1979. Most recently, 1,700 st of phosphate ore was produced at 25 st/h from deep (230- to 250-ft) deposits in St. Johns County, Florida. Progressive improvements were made in the borehole mining technique. These include the use of the hydrostatic head of a water-filled borehole for roof support and the development of methods to survey and backfill mined-out cavities.