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arch blocks
Applied to the wooden voussoirs used in framing a timber support for the tunnel roof, when driving a tunnel on the so-called American system. These blocks are made of plank, superimposed in three or more layers, and a breaking joint.
- 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)