Single jacking in an underground mine (Butte, Montana, USA) 2 : 無料・フリー素材/写真
Single jacking in an underground mine (Butte, Montana, USA) 2 / James St. John
| ライセンス | クリエイティブ・コモンズ 表示 2.1 |
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| 説明 | (ink illustration by Buck O'Donnell; public display, World Museum of Mining, Butte, Montana, USA)--------------------------------------------The town of Butte, Montana (pronounced “byoot”) is known as the “Richest Hill on Earth” and "The Mining City". The Butte Mining District has produced gold, silver, copper, molybdenum, manganese, and other metals.The area's bedrock consists of the Butte Quartz Monzonite (a.k.a. Butte Pluton), which is part of the Boulder Batholith. The Butte Quartz Monzonite ("BQM") formed 76.3 million years ago, during the mid-Campanian Stage in the Late Cretaceous. BQM rocks have been intruded and altered by hydrothermal veins containing valuable metallic minerals - principally sulfides. The copper mineralization has been dated to 62-66 million years ago, during the latest Maastrichtian Stage (latest Cretaceous) and Danian Stage (Early Paleocene). In the supergene enrichment zone of the area, the original sulfide mineralogy has been altered.--------------------------------------------From exhibit signage:Why do miners drill?Drilling holes allow explosives to be placed and detonated inside solid rock to break it loose from the world and into pieces.Iron tools, like hammers, picks, and chisels have been used to mine since the beginning of the Iron Age, about 2000 B.C. There were no explosives, so rock was simply beaten to pieces or wedged apart. Oddly enough, it took over 300 years after the invention of gunpowder before it was used to break rocks. Even then, for may years it was only used in natural cracks and fissures.The first known use of drilled holes filled with gunpowder to break rock was in Germany in 1613. It was used exclusively for 250 years and continued to be used in coal mining and other special applications well into the 20th Century.Unbelievably, pure liquid nitroglycerine, one of the most sensitive and unstable explosives known, was used extensively for rock blasting after the American Civil War. Both manufacturing and transportation were extremely hazardous. The slightest impurity or error could cause a batch to explode when the chemicals were combined. It was hauled around in bone-jarring wagons on rough roads. Documented cases tell of wagonloads rolling down mountains without detonating, but others that exploded from an insignificant cause, like a kid throwing a rock.Alfred Nobel, the creator of the Nobel Prize, invented dynamite in 1868, using an absorbent material to de-sensitize nitroglycerine. He also invented the blasting cap to reliably set it off. The first dynamite plant in the United States was built in San Francisco in 1870, but it did not come into common use for nearly ten years until after the manufacturing and transportation methods were perfected.Hand DrillingFor 250 years, strong men swinging hammers against the iron drills was the only means of drilling holes in rock. One man drilling alone was called "single-jacking", while teams of two ore more, using heavier hammers, was "double-jacking". It was slow, hard, dangerous work with only oil lamps and candles for light. Buck O'Donnell's drawings show the drillers at work, but the white pages do not convey doing it in smoky, dusty, near-darkness and stifling heat.[A] granite block [was] a contest stone. Drillers would compete in front of huge crowds for the title and prestige of drilling the deepest hole in fifteen minutes. Butte miners Walter Bradshaw and Mike McNichols hold the world's record for double-jacking, just shy of four feet.However, two ordinary drillers working 10-12 hour shifts, day after day, year after year, drilled only four to six inches in hard rock during the same 15 minutes. Advancing a mine tunnel four feet took about a thousand inches of drilling, over eight days of constant drilling. Taking advantage of natural fractures was an important skill the best miners learned to cut this time down, but tunnel progress still averaged less than a foot a day. |
| 撮影日 | 2010-08-10 13:08:32 |
| 撮影者 | James St. John |
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