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出典:Wikipedia
出典:『Wikipedia』 (2011/08/10 14:00 UTC 版)
Longwall mining is a form of underground coal mining where a long wall of coal is mined in a single slice (typically 1–2 m thick). The longwall panel (the block of coal that is being mined) is typically 3–4 km long and 250–400 m wide.
Longwall mining