Abstract:

In order to guarantee the safety of the ultraclose underlaid shield tunnel, the protection technologies are studied by adopting structural analysis, theoretical calculation and monitoring method during foundation pit excavation. The study results show that: 1) The internal force conversion and deformation of underlaid shield tunnel is analyzed by using calculation software under protection condition; the internal force of the tunnel segment increases firstly and then decreases with foundation pit excavation, of which the increasing range is limited; the internal force of the shield tunnel does not affect the safety control, but the deformation of the shield tunnel plays an important role in safety control. 2) The effects of uplift anchor bolt in tunnel, separation pile at tunnel side, temporary support in tunnel and balance weight on shield tunnel deformation control are studied; the deformation control effect of separation pile + temporary support + balance weight is the best, followed by that of separation pile, and that of the uplift anchor bolt is the worst. 3) The shield tunnel protection technologies are put forward and applied to practice. The results can provide reference for similar projects in the future.

Key words: foundation pit excavation, shield tunnel, ultraclose underlaid, protection technology