通过北京铁路地下直径线工程盾构施工实践经验，总结了大埋深富水砂卵石地层泥水盾构施工中带压换刀技术以及特殊情况下的带压动火焊接技术。带压换刀的技术主要有两个方面:一是选择合理换刀地点及进舱工作压力，保证掌子面土体的稳定；二是进行开挖舱高浓度泥浆的置换和中盾高浓度泥浆的注入，有效地防止了气体的逃逸。在施工中成功实现了带压进舱250余次，工作压力从0.9 bar (1 bar=100 kPa)增加到2.8 bar，未发生任何安全事故。

According to project experience in Beijing Railway underground project, the changing cutter and welding techniques with high pressure of slurry shield under deep water-rich sandy gravel stratum were summarized. There were two main technologies. One is to choose an appropriate position and an appropriate working pressure for making a good previous preparation to ensure the stability of tunnel face. The other is the replacement and grouting of high-concentration slurry, which avoided the gas escape effectively. During the repair welding, we successfully realized going into the excavation chamber with high pressure for more than 250 times, and the working pressure rose from 0.9 bar(1 bar=100 kPa) to 2.8 bar with no accident.