The only way to complete the high-speed rail link between Türkiye’s major cities, Ankara and Istanbul, is to tunnel through difficult mountain terrain in what’s known as the Doğançay Bypass.
Türkiye’s complex geology and major fault zones can create significant issues for TBM construction, including squeezing ground, excessive water ingress and even face collapses.
Tunnel construction for the Doğançay Bypass takes place entirely in clay and other cohesionless units, and in seismically active ground conditions.
NATM (New Austrian Tunneling Method, also called Sequential Excavation Method) construction is being used for two high-speed rail tunnels of 2,880m (9,450ft) and 4,665m (15.305ft) lengths.
Dramix® 5D 65/60BG steel fibers have been selected instead of conventional steel bars to reinforce the cast-in-place tunnel lining, successfully meeting the support requirements in this highly challenging geology.