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Lovat Readies TBM for Bosphorus Railway Tube Crossing in Istanbul

Lovat Readies TBM for Bosphorus Railway Tube Crossing in IstanbulThe Marmaray project in Istanbul will provide a fully upgraded commuter rail line, connecting Halkali on the European side with Gebze on the Asian side. The uninterrupted, modern, high-capacity commuter rail line upgraded to three tracks will offer a capacity of 75,000 passengers per hour and per direction. The upgraded three-track line on each side of the Bosphorus strait will be connected to each other through a dual-track rail tunnel under the Bosphorus. The entire upgraded and new railway system will be 76.3 km long, whereof approximately 13.5 km is underground. The main structures and systems include an immersed tube tunnel across the Bosphorus - the so-called Bosphorus crossing -, connecting bored tunnels and cut-and-cover tunnels on either side of it, at-grade structures, three new underground stations, 37 surface stations (36 of them new), an operation control centre, yards, workshops, maintenance facilities, facilities, upgrading of existing tracks and a new third track at grade, completely new electrical and mechanical systems and procurement of modern railway vehicles. Visit www.marmaray.comPartners of the projectThe owner is DLH, the General Directorate of railways, harbours and airports construction, under the Turkish ministry of transportation.Avrasyaconsult is responsible for the engineering and consulting services for the project. It is an international team of Pacific Consultants International (PCI) from Japan, Yuksel Proje of Turkey, Oriental Consultants of Japan as partner for the immersed tunnel, and JARTS also from Japan for the railway expertise. This JV teams with Parsons Brinckerhoff, which brings special expertise for the immersed tunnel and electrical and mechanical tunnel installations. The JV works also in partnership with Turkish consultancies Terzibasioglu Musavir Muhendislik (TMM) and Yerbilimleri Etud ve Musavirlik (SIAL), which bring special expertise in underground structures and geotechnical engineering. Visit www.pci-world.com/en/index.html, www.yukselproje.com.tr, www.oriconsul.co.jp/english/index.html, www.jarts.or.jp/en/index.html and www.pbworld.comThe TKGN JV, a Japanese-Turkish joint venture comprising Taisei (50%), Kumagai Gumi (25%), Gama (12.5%) and Nurol (12.5%), won the contract. Gama and Nurol, both Turkish contractors, are the contractors on the Bosphorus crossing contract. The successful contractor for each contract is responsible for the detailed design and construction of the structures and systems, and reports to Avrasyaconsult. Work started on the project at the beginning of the year. Visit www.taisei.co.jp/english/index.html, www.kumagaigumi.co.jp, www.gama.com.tr and www.nurolconstruction.com/profileng.htm Underground sectionThe underground segment mainly consists of the 1.4 km immersed tube, 11.6 km of bored tunnels, 1.3 km of cut-and-cover tunnels and three stations. The inner bored tunnel diameter is 7.04 m. The line goes underground at Yedikule, continues through the Yenikapi and Sirkeci new underground stations, passes in immersed tube under the Bosphorus, connects to the Uskudar new underground station and emerges at Sogutluçesme (see map).Two out of the three stations will be constructed with the cut-and-cover technique: Yenikapi at a depth of track of 17 m and Uskudar at a depth of track of 26 m below ground. Sirkeci station will be a tunnelled station lying at a depth of track of 45 m below the surface.The challenges are numerous. The immersed tunnel under the Bosphorus will be the deepest in the world with its deepest point at some 58 m under the water surface. The area of Istanbul will most likely experience a seismic event of up to magnitude 7.5 during the lifetime of the project. The deep stations and tunnels will have to be constructed in an area where civilization can be traced more than 7,000 years back in time. Preservation and rescuing of historical heritage is therefore a focus point not to be neglected. Read E-News Weekly 20/2006. The bored and cut-and-cover tunnels run under many historical and cultural structures and run through important archeological strata. The European side peninsula is the historical peninsula registered as World Heritage. Urban areas are densely populated and consist of series of old 5-6 storey buildings, which are closely built to each other on the ground without positive foundations. Furthermore, there are numbers of registered or unregistered wells used for daily life.The existing TCDD rail line runs along the new line in the western part on the European side and these two lines are nearly overlapping between Yenikapi and Yedikure. It means the TCDD line, which runs on the surface, must stay operational throughout all the tunnelling works.Bored tunnelsA new Lovat EPB shield on the European side will excavate 3,670 metres. Four 7.84 m-diameter Hitachi Zosen slurry shield TBMs will also be employed, two on the European side to bore 3.3 km through cracked rock and two on the Asian side to carve out 4.6 km of cracked rock. The rock is essentially heavily fractured sandstone with some inactive faults and a high risk of high groundwater pressures. The four machines were scheduled to start operating in the spring of 2006. Visit www.hitachizosen.co.jp/english/index-e.htmlThe EPB Lovat soft ground machine has been ordered by the Gama-Nurol joint venture. The JV has recently accepted the Lovat TBM model RME314SE series 21900. The tunnel alignment runs between Yedikule and Yenikapi. The tunnel consists of twin tubes of 1,835 metres each. The TBM length is 10 metres, while the TBM and back-up length is 85 metres. The machine weighs 552 tonnes. Its cutting diameter is 7,994 mm, its bore diameter is 7,969 mm and the shield diameter is 7,956 mm. The TBM will erect and install a prefabricated concrete segment tunnel with significant design considerations on potentially-volatile local seismic conditions. The tunnel lining will be made of six prefabricated concrete segments and one key. A screw conveyor will be used in a closed/pressurised mode for the mucking-out.The geology along the tunnel alignment is comprised of hard silt, hard sandy clay, clay, lenses of limestone, hard gravelly sandy clay, firm clay, and hard clay.Lovat was contracted to design and custom manufacture the mixed face EPB TBM along with associated ancillary equipment. Currently, the assembly process is ongoing. The main sections of the TBM have been assembled and positioned on the launch cradle. Assembly of the trailing gantry is now being completed. The official launch ceremony is scheduled for 15th-16th December, 2006. Visit www.lovat.com Immersed tunnelThe proposed method for the immersed tunnel requires using two dry docks at Tuzla, 41 km away from the immersion site by the proposed towing route. Each dock can take two tunnel elements. A steel plate surrounds the bottom and sides, and the sides are to be stiffened steel plate, including temporary bracings over the top of the tunnel. These and the end bulkheads form the basis of the immersed tunnel element. Two are assembled in each dry dock. The base is then cast in a single operation, followed by half the wall height. This partially completed tunnel element is then floated out.Using floating pontoons as working platforms, the elements are completed afloat, with the roof slab also being cast in a single operation. This procedure enables new tunnel elements to be started when the tunnel elements are only half finished, shortening the overall construction time.The contractor proposed to backfill the area around the end of the tunnel with mix-soil, a cementitious mixture with a strength of about 1 MPa which will form a more or less watertight transition from the adjacent rock to the immersed tunnel.Clay, silt and sand exist in the central portion of the waterway where the immersed tunnel is specified. The immersed tunnel is laid in a trench excavated in the seabed.The geotechnical conditions of the Bosphorus strait are such that the connection between the bored tunnels and the immersed tunnel will constitute a special technical challenge in terms of seismic conditions. The marine works will have to be performed in very deep waters in a waterway that carries more than 50,000 ships every year, among which a great number of ferries and passenger boats crossing the strait. FinancingIn 1999, a funding agreement between the Republic of Turkey and the Japanese Bank for International Cooperation (JBIC) was signed. This loan agreement forms the basis for the funding of the Marmaray project, which represents some 35% of the costs for the entire railway project. In 2005, another funding agreement of a similar amount (EUR650 million) was signed between Turkey and the European Investment Bank (EIB). The remaining funding for the project is being guaranteed by the Turkish government (loans and/or by private funding). Click tr/14. 48/06.