The large diameter direct drainage borehole is used to strengthening mine drainage capacity, to ensure coalmine safety production.
大孔径直排孔的作用是加强矿井排水能力，保证煤矿安全生产。
Taking two of projects as examples, the paper discussed the technology of large diameter borehole blasting applied in the excavation of footing groove in city.
以两个工程为例，介绍了在城镇基坑开挖工程中采用了大孔径深孔爆破技术。
The large-diameter gas drainage well laid out in the Xuandong No. 2 Mine used small-diameter pilot drilling, then gradually reaming the borehole and finally completed to designed size.
宣东二号矿布设施工的大口径瓦斯抽放井以小口径导向钻进，后逐级扩孔成井。
The large-diameter gas drainage well laid out in the Xuandong No. 2 Mine used small-diameter pilot drilling, then gradually reaming the borehole and finally completed to designed size.
宣东二号矿布设施工的大口径瓦斯抽放井以小口径导向钻进，后逐级扩孔成井。
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