Steady advance marked on Izmir Metro Phase 4

Funded by Izmir Metropolitan Municipality (IMM), the US$1.26bn project will create a metro service to help reduce traffic congestion in the heart of one of Turkey’s fastest-growing cities. It is the fourth expansion of the city’s single metro line.

The project comprises 7.2km of TBM-bored tunnels with inner and outer diameters of 6.2m and 6.6m respectively. The TBMs have been launched and received from seven box stations along the route – Kaymakamlik, Sehitlik, Narlidere, Güzel Sanatlar Fakültesi, DEU Hastanesi, Çagdas and Balçova – with a total of 14 cross passages built.

Two 6.6m-diameter EPB TBMs – made by CRCHI and Herrenknecht – have been boring round the clock from Balçova in the east of the city toward Kaymakmik in the west. Overburden has ranged from between 15-35m. The two machines have together installed over 57,600 segments and excavated over 492,000m3 of soil.

Two main geologies have been encountered along the route: decomposed flysch and weathered limestone. Due to the high presence of fines in the flysch, the soil had a tendency to clog the cutterhead and bulk chamber.

Consumables for both TBMs have been delivered by Foramec in partnership with Normet. TamSoil 285AC (Normet’s anti-clay additive) was used to treat the decomposed Flysch, helping to completely reduce clogging and torque build-ups. In addition, the polymerised anti-wear foam TamSoil 261CF-AW was used to minimise wear on disc cutters and cutting tools when mining through the weathered limestone. The foam also reduced torque forces as it lubricated the surfaces in the chamber, reducing contact forces during mining.

When completed, Izmir Metro will operate the line under an indefinite lease agreement with IMM.