Marmaray project: Tunnels and stations in BC contract

• Published in: Tunnelling and underground space technology 2005-11, Vol.20 (6), p.612-616
• Main Author: Sakaeda, Hideki
• Format: Article
• Language: English
• Subjects: Bosphorus crossing; Closed-face shield TBM; Employer’s requirement; Historical and cultural heritages; Marmaray project
• ISSN: 0886-7798; 1878-4364
• DOI: 10.1016/j.tust.2005.08.007

Istanbul is one of the most famous historical cities in the world. However, the project alignment selected as the best of a range of alignments cannot avoid passing beneath the historical and cultural heritages of Istanbul as well as under ancient and densely inhabited areas of the city. This paper will explain some of the challenges related to the bored tunnels. Historical buildings are vulnerable. Yet many existing residential and office buildings are old and constructed on minimal foundations. As a consequence, it is vital that any drawdown of groundwater and any ground settlements have to be minimized. In addition, the connection between the immersed and bored tunnels will be made directly and totally underground, without the usual intermediate shafts and beneath the deep waters of the Bosphorus Strait. This operation needs the utmost control of the tunnel excavation face to ensure its stability and to minimize water ingress. Based on such considerations, tunnel excavation by tunnel boring machine (TBM) using a slurry shield and having the ability to operate under high pore pressures was recommended as the method of excavation for the main running tunnels. The paper will explain how the design team from Avrasyaconsult – the Employer’s Representative – arrived at the final minimum, specific and functional requirements of the bored tunneling works which are to be carried out using the ‘FIDIC EPC/Turnkey Project’ conditions.