Similarly to general tunnel construction, the Chuo Shinkansen project
uses the New Austrian Tunneling Method (NATM) in mountainous areas.
This method sprays concrete on excavated surfaces to form a lining,
and uses bolts and concrete to reinforce the surrounding rock masses and integrate them into natural ground.
The geological stress around a tunneling site is utilized to excavate forward.
The method is characterized by its adaptability to the conditions of natural ground
at construction sites, and flexibility in accommodating geological changes and obstacles.
Learn more about NATM
Construction of the Southern Alps Tunnel involves great difficulty, as it will be one of the largest tunnels in Japan in terms of both length and depth, with a total length of approx. 16 miles and a depth of up to 4,593 feet from the ground surface (overburden). The following video provides information about our initiatives for safety and environmental conservation in the construction of the Southern Alps Tunnel.
Geological survey to ensure safety
① Drilling a pilot tunnelPrior to constructing Chuo Shinkansen's main tunnel, JR Central drills a small-diameter pilot tunnel parallel to the main tunnel. Local geology and welling of water are examined in advance to ensure safe construction. The pilot tunnel will be used for maintenance work and evacuation once the main tunnel is built.
② Ultra-long boringBoring surveys in tunnels generally examine geological properties for areas up to 328 feet from the tunnel face (foremost part of excavated site). However, due to the Southern Alps' geological complexity, JR Central has decided to use ultra-long boring to survey the geology of ground up to about 3,280 feet from the tunnel face. The geological features of ground up to 3,280 feet ahead are examined by accurately controlling the edge of the tunnel boring machine, so as to identify the most suitable construction method when proceeding with excavation work.
Installing a headrace tunnel for environmental conservation
A headrace tunnel is installed in the Shizuoka construction section to guide wellwater in the tunnel, generated from the construction work, to Oi River. JR Central carries out the tunnel construction, ensuring minimal impact on water resources in the mid and downstream reaches of Oi River.
Watch the TBM method in action
Tunnel Boring Machine [TBM] Excavation
The Tunnel Boring Machine (TBM) method, which has a relatively fast excavation speed, is used to swiftly install a headrace tunnel.
The contruction work is planned to ensure that wellwater, generated from tunnel construction, is diverted to Oi River as soon as possible.