Abstract: When opentunnel boring machine (TBM) boring through a highpressure waterrich weakfracture altered structural belt, problems, such as surrounding rock deformation, difficult borehole drilling, difficult support, cutterhead jamming, shield jamming, and mud burstcaused shield burial, are often encountered. Two openTBMs were applied to the Gaoligongshan tunnel of the DaliRuili railway in extremely complex strata in southwest Yunnan, and they crossed highpressure waterrich weakfracture altered structural belts at section PDZK221+481. Research is conducted on key TBM construction technologies, i.e. primary support reinforcement measures, drilling technology, advanced reinforcement measures, sidewall heading depressurization measures, TBM jammingrelease technology, and adverse geology tunneling and support measures. Then, some corresponding countermeasures, such as geological detection with a high small pilot tunnel, advanced drainage depressurization with sidewall heading, insitu advanced pipe roof and grouting reinforcement, jamming release with shield expanding excavation and release, and cutterhead jamming release with cleaning periphery of the cutterhead after chemical grouting reinforcement of the tunnel surface, and primary support strengthening, are taken. Moreover, the crosssection form and support measures for the sidewall heading and pipe roof chamber, and support measures for advanced reinforcement are put forward.

Key words: railway tunnel, open TBM, highpressure waterrich weakfracture altered structural belt, mud burst, sidewall heading, jamming release