pillar operation造句
造句与例句
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- It was a room and pillar operation with an estimated recovery of about 35 %.
- Hatch's mine is the old underground room-and-pillar operation.
- The Peerless Mine was an underground room and pillar operation that mined coal near the outcrop of the Wyodak seam.
- Where the seams are relatively flat lying or gently dipping most of the mines were underground room and pillar operations, and where the seams are steeply inclined to vertical, stope mining was used.
- It's difficult to see pillar operation in a sentence. 用pillar operation造句挺难的
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