UtakataNoAnnex
Senior Member
Forgive me for doubting you! >.<One shaft access is sufficient for cavern works. They bring all the equipment including the road header parts down through the North shaft and assemble them at the bottom. The cavern run beside shafts so work can advance in parallel with shaft excavation. This picture shows the cavern looking South, with the unexcavated part on the left is the connection to the South shaft left for a later phase.
They want the cavern to be ready as early as possible to accommodate the coming TBMs.