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| 保护级 | |||
| 护顶盘井筒延深时，为防止岩柱的松动、冒落,紧贴其下设置的承重结构物 | |||
| protection stage: 4 phrases in 3 subjects |
| Electronics | 2 |
| Hydroelectric power stations | 1 |
| Rail transport | 1 |
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