The route of the "Istanbul Strait Road Tube Crossing Project" runs around 100 meters below sea level at its deepest point. The interior diameter of the tunnel will be 12 meters so that two lanes in each direction can be accommodated. They will extend one above the other on two levels. 3.34 kilometers of the first road tunnel between the Asian and European parts of Istanbul, with a total length of 5.4 kilometers, are being created by a Herrenknecht Mixshield.
According to the extensive geological and hydrogeological preliminary investigations, tunnel builders must reckon with water pressures of up to 12 bar. To be able to change the excavation tools quickly and safely even with high pressures, Herrenknecht has developed an innovative cutting wheel concept. Thanks to this cutting wheel innovation, time- and cost-consuming access for maintenance work under pressurized air can be reduced. The complete cutting wheel is accessible from the rear of the machine under atmospheric pressure. From there, all disc cutters and a large part of the cutting knives can be changed safely. In addition, the Mixshield is equipped with a special, newly developed lock system. It allows pressurized air access at well over 5 bar where necessary.
To detect strong material wear early and to tackle necessary maintenance accesses in a targeted manner, wear detectors are integrated into the excavation tools as well as in the steel construction of the cutting wheel. Moreover, the disc cutters are equipped with the DCRM system (Disc Cutter Rotation Monitoring) which was developed by Herrenknecht. It provides data about the rotational movement and temperature of the disc cutters in real time to the machine operator in the control container. Thus, conclusions can be drawn regarding the condition of the tools and change intervals can be better planned.
The tunnelling for the "epoch-making project" was launched on the Asian shore of the strait in April 2014. With pioneering technology and an ideal cooperation of all project partners the TBM accomplished best performances of upt to 92 meters per week under the Bosporus. After only 16 months the Mixshield pierced the target shaft wall on the European side exactly to plan on August 22, 2015.
The successfully completed drive marks new feasibility standards in tunnel construction. In Istanbul the new road tunnel will provide major relief of traffic congestion on the strait crossing. From late 2016 around 100,000 cars a day are expected to cross between the continents in the Eurasia Tunnel on two roadways one above the other.