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Steel beams for tunnel shoring - the chicago curve. jan 25, 2013 · tunnel shoring is used extensively in mining. steel beams are formed into a variety of shapes full circles, 180 degree segments, 180 degree segments with straight tangents (a horse-shoe tunnel support), and variations on the above., navy's first advance base madisonville in massachusetts bay in the marquesas islands, some 800 miles northeast of borabora, was established by commodore david porter to repair the frigate essex after its historic voyage around the horn in 1813. the essex, which was the first american warship to visit the pacific, is shown, with her prizes, in this old print, published in london in 1823. in his ....

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