Mining technology in 1972 / Amil Dubnie, Mining Research Centre. : M34-20/180E-PDF

“During 1971, there was a slight decrease in the tons of ore mined from surface metal mines and a slight increase in ore mined underground. As a result, the ratio of surface-mined to total showed a decrease from 0.69 to 0.66. In surface non-metal mines during 1971, the increase in underground ore was greater than for surface-mined ore. This resulted in a decrease in the ratio of surface ore to total ore from 0.66 to 0.65. The substantial increases in surface-mined coal continued and the ratio of surface-mined to total coal rose to 0.75. During 1971, about 33 per cent of underground metallic ore was mined by cut-and-fill stoping or variations thereof, followed by open stoping with long-hole drilling at 26 per cent. In terms of tons mined in underground metal mines, sublevel caving accounted for about 17 per cent, making this the third most important method. Decreases in mining costs occurred in underground mining of potash by the room-and-pillar method, and gold-quartz mining by shrinkage stoping. Other methods showed substantial increases. It is apparent that advances in underground mining technology are not keeping pace with rising costs. An important advance during 1972 was the introduction on a production scale of slurries for underground blasting and means for bulk handling and loading them"--Summary, p. i.

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