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| 向下掘进炮孔组斜井和立井向下爆破钻凿的炮孔。由于井筒底部炮孔容易充水,岩石夹制作用大且不易清理爆落的石渣，所以用药量要比向上掘进爆破法大得多。在立井中向下掘进时，为了防止井壁崩坍和安全起见，炮孔组 - 次爆破进尺不宜太大 | |||
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sinking round : 2 phrases in 1 subject |
| Explosives and Explosive Ordnance Disposal | 2 |
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