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main levels
The first and leading excavations in mines that are made for the purpose of opening out or winning the material being mined, and that are intended to be the principal roadways of the mine.
- 词性: noun
- 行业/领域: 采矿
- 类别 一般矿业; Mineral mining
- Government Agency: USBM
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创建者
- ed.young
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(Milwaukee, United States)