Abstract: To clean the obstacles encountered during a shield tunnel crossing underneath operational station in waterrich sandy stratum, a case study is conducted on Wuhan metro line 12 crossing underneath an operational station, and a construction scheme, opencut obstacle cleaning shaft, obstacle cleaning by longitudinal freezing in shaft, and shield tunneling after backfilling with plain concrete, is proposed. First, the allowable deformation control indicators for the existing operating station are given by referring to industry standards and similar cases. Second, mechanical analysis is conducted on freezing excavation, obstacle cleaning shaft excavation, and shield tunneling using finite element numerical method, and key technical points of design and construction of each process are proposed. Finally, according to analytical results of the measured deformation data on site, the deformation of the existing station floor is within the range of the calculated value by finite element. The proposed scheme ensures the controllable deformation of the existing operational station, addresses water inrush and collapse problems during manual breaking of the underground obstacles in waterrich sandy layer, and improves the safety of the new tunnel passing through the underground structural obstacles.

Key words:

obstacle clearing shaft, shield tunnel, underground obstacles, freezing, mechanical analysis