Bureau of Mines / Minerals yearbook: Metals and minerals 1977
Year 1977, Volume 1 (1977)
Cooper, Franklin D.
Mining and quarrying trends in the metal and nonmetal industries, pp. 37-60 PDF (2.0 MB)
Mining and Quarrying Trends in the Metal and Nonmetal Industries By Franklin D. Cooper' The value of nonfuel raw mineral production in the United States for 1977 increased over that of 1976 by 5%, from $16.7 billion to $17.5 billion. Metals declined by 5% from $6.1 billion to $5.8 billion, chiefly because of strikes in the iron ore industry and a depressed copper market. Subsidization of mining industries in some foreign countries accounted in part for the excess of copper and some other metals on world markets. Weak metal markets and continued slowdowns in the world economy were the main reasons of the virtual absence of new mine projects. Increasing domestic governmental involvement affecting mineral industry activities, such as pricing controls, public land withdrawals, and the Surface Mirung Control and Reclamation Act, effective August 3, continued to be controversial and to be criticized by various segments of the industry. Large capital outlay and the long lead time to attain production from a new facility were also of concern. Because of increasing costs and depletion of higher-grade reserves, the mining industry relied heavily on technology to develop more efficient mining and processing methods. The use of raise- and shaft-boring was popular, compared with former development practices, because less completion time was required. Mine ventilation was improved and less maintenance was needed after the boring was completed. Four U.S. companies produced raise-boring machines, one of which could produce a 350,000-footpound torque and a 2-mfflion-pound thrust. One manufacturer patented a "taper-lock" removable stem to eliminate the replace ment of entire boring heads up to 20 feet in diameter when only the stem is broken. Although pneumatic drill rigs dominated in most underground mines, hydraulic percussion drills with one single moving part gained favor because of faster penetration and less noise while requiring less energy and maintenance. A twin-boom tunneling jumbo equipped with a dry dust collector met the strict requirements of environmental inspectors in an underground limestone mine. The Bureau's continuous spiral drill-andblast concept, when tested in the White Pine Copper mine, indicated advance rates four times that of conventional drill-andblast methods. Explosives manufacturers introduced a new plastic connector, the Safe-T-Tube, to prevent premature detonation of detonating cord. Two new explosives were made available for underground blasting. Diesel-powered haulage continued to increase in noncoal underground mines. A roof-support system using 14- to 18-footlong fiberglass beams permitted a continuous mining operation, as demonstrated in a Pennsylvania mine, to advance 20 feet farther than with steel beams previously used. The Bureau of Mines developed an improved method for anchoring roof bolts, using a cartridge containing quick-setting portland-gypsum cement and microencapsulated water. Tungsten-halogen lighting was initially introduced in underground mines as were two new designs of roof bolts. In the surface mining sector, trends in new equipment were diversified. A 16-cubicyard hydraulic-type shovel was being tested 37
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