The largediameter 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。
2
Taking two of projects as examples, the paper discussed the technology of largediameterborehole 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。
3
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.