TBM RECORDER TBM to take on Bosphorus highway crossing14 Aug 2013
Herrenknecht News Release
A 13.6m Mixshield has been factory tested and accepted by the client for excavation of the single-tube, double-deck highway tunnel beneath the Bosphorus in Istanbul, Turkey. The new highway tunnel will add much needed capacity to the traffic bottleneck between Europe and Asia. The Herrenknecht TBM will excavate 3.34km of the total 5.4km long tunnel begin its undersea mission from a launch shaft on the Asian side. Currently, two road bridges and ferries provide the only transport link between the two parts of the city and the two continents.
The Bosphorus was first crossed using a TBM in 2008 when a Herrenknecht EPBM of 6.11m diameter excavated a water tunnel beneath the Strait.
Several advanced features identify the 13.6m Mixshield
The technical planning of the larger highway tunnelling operations posed more complex challenges. To cope with these demands the construction consortium ordered an advanced Mixshield. The machine was completed in early July 2013 in Schwanau and is now on the way to the jobsite.
"The project is certainly one of the most challenging tunnelling operations currently being addressed in the world," is the assessment of Herrenknecht Project Manager Georg Schleer. The route of the Istanbul Strait Road Tube Crossing runs about 100m below sea level at its deepest point.
Extensive geological and hydrogeological preliminary investigations indicated that the tunnel builders must reckon on hydrostatic water pressures of up to 12 bar. The Turkish-South Korean construction consortium YMSK, consisting of Yapı Merkezi lnşaat ve Sanayi A.Ş. and SK Engineering & Construction, ordered the specially developed Mixshield from Herrenknecht.
Istanbul Strait Road Tube Crossing Project
Tunnel length (mechanized tunnelling)
Sand with gravel, limestone and clay stone
One of the machine's particular features is a new type of cutterhead, where 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 number of the pick tools can be changed safely.
In addition, the Mixshield is equipped with a special, newly developed lock system. It allows pressurized air access at well in excess of 5 bar where necessary. "Even if the pressure is extremely high up front at the tunnel face, the client must be able to change the cutting tools quickly and safely if necessary," explained Schleer, summarizing the starting situation for the engineers from Schwanau.
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 cutterhead. The disc cutters are also equipped with the Disc Cutter Rotation Monitoring System (DCRM) developed by Herrenknecht.
Herrenknecht S-762 Mixshield
YMSK (Yapi Merkezi İnŞaat ve Sanayi A.Ş., SK Engineering & Construction
It provides data about the rotational movement and temperature of the disc cutters in real time to the machine operator in the control cabin. With the data, conclusions can be drawn regarding the condition of the tools and change intervals can be more effectively programmed.
In the Herrenknecht factory in Schwanau the Mixshield was named YILDIRIM BAYEZİD. This is the name of a sultan, who drove the expansion of the Ottoman Empire forward at the end of the 14th Century. After its dismantling, transport and assembly at the jobsite, the Mixshield will start its tunnelling work in Istanbul at the end of 2013.
Following the opening of the tunnel, the new quick link between Europe and Asia will initially be operated for 26 years by the Avrasya Tüneli İşletme İnşaat ve Yatırım A.Ş. (ATAŞ) Joint Venture and subsequently handed over to the government of Istanbul.
As well as the Bosphorus water tunnel crossing, several other Herrenknecht machines have worked in Istanbul. Among these, a total of about 56km of Istanbul's metro are built using machines produced in Schwanau.
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