Continuous tight curved belt conveyor of R30m did a TBM drift excavation a lot of

Initially the NATM was planned to be used for this project. The tunnel construction started in August 2001 from Shin-Aomori side, but two significant collapses occurred in March and September 2002. Development was therefore required of effective means to ensure safety in the work at the face and less impact on the structures on the surface, and countermeasures against delay in the work schedule.