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享德孙(Henderson)矿平硐通过4600呎的复杂地质条件的岩层,平硐断面宽16.5呎、高15呎2寸。矿山矿石储量3亿吨,品位钼0.49％;1977年将生产钼5000万磅。平硐通过的岩层为变质水成岩、片麻岩及片岩,还有一些花岗岩侵入体;它还通过一系列断层和高度裂隙的岩石带。平硐掘进以3％的坡度倾向矿体,平硐的末端将比它的进口低约1500尺,故在掘进时所有的水都流向工作面。在掘进过程中开始遇到
The Henderson mine passes through a rock formation of 4,600 feet of complex geological conditions with a 16.5-ft-wide and 15-foot-2 inch high section. Mine ore reserves of 300 million tons, grade 0.49% molybdenum; 1977 will produce 50 million pounds of molybdenum. The formations that the adit passes are metamorphic igneous, gneiss and schist, with some granite intrusions; it also passes through a series of fault zones and highly fractured rock zones. The tunneling propels the orebody at a 3% slope, and the tail end of the adit is about 1,500 feet below its entrance, so that all the water is heading towards the work surface during the excavation. In the tunneling process began to encounter