Page 10 - TunnelTalk Annual Review 2010 Preview

An immersed tunnel will also present considerable technical challenges. However, unlike a bridge, an immersed tunnel will not entail as many technical operations which push the limits of what has been done before. Essentially, the procedure will be the same as it was for construction of the Øresund Fixed Link’s immersed tunnel under the Drogden Channel between Denmark and Sweden, only many times longer and deeper. The Fehmarnbelt Tunnel will be just under 18km long and up to 30-40m deep, while the Øresund Tunnel is approximately 4km long and about 10m deep.
Both a cable-stayed bridge and an immersed tunnel would impact the marine environment but the preliminary conclusion is that a bridge would have slightly more significant permanent impact than an immersed tunnel.
In the interests of navigation safety, a tunnel poses fewer risks than a bridge. The Fehmarnbelt is a heavily trafficked stretch of water with 47,000 vessel transits per annum (2006). In the coming years, traffic is expected to increase substantially to about 90,000 vessel transits in 2030.
Financial factors
In financial terms, there is very little difference between the two projects. The construction estimate (in 2008 price level) for an immersed tunnel is E5.1 billion and for a cable-stayed bridge, E5.2 billion.
The construction time for the tunnel is estimated at 61⁄2 years, and for the bridge, 6 years. The cost of operation and maintenance is slightly higher for a tunnel than for a bridge. All told, the payback time for the two projects would be essentially the same at about 30 years for the coast-to- coast project. In a press release of the announcement, Danish Minister for Transport Hans Chr. Schmidt stated: “From an overall financial perspective, there is no difference between bridge and tunnel. The cost of the two solutions is, generally speaking, the same, which confirms the project’s sound financial basis.”
Over the coming year, Femern A/S will complete the Environmental Impact Statement to be considered by the authorities in Denmark and Germany in accordance with national regulations and submit an application for construction approval to German authorities during the first six months of 2012. A construction bill will then be submitted to the Danish Parliament, Folketinget, in 2013. Following approvals, construction of one of Europe’s biggest infrastructure projects is expected to commence in 2014 and open to traffic in 2020. n
References
• Fehmarnbelt fixed link options - TunnelTalk, June 2009
• Cost comparison for Fehmarnbelt link options - TunnelTalk, Nov 2010
Innovations for the
In September 2008, the Danish and German Ministers of Transport signed a treaty to establish a link across the Fehmarnbelt between Lolland, Denmark and Fehmarn, Germany. The same treaty was subsequently approved by the Danish Parliament and the German Bundestag. The Fehmarnbelt Fixed Link will be the third major crossing in Denmark after realization of the Great Belt (1998) and the Øresund (2000) links. It represents the missing link in an efficient transport corridor between Scandinavia and Europe and will accommodate a four-lane motorway and a double track railway (Fig 1).
Denmark has assumed sole responsibility for the financing, implementation and future operation of the fixed road and rail link and for this purpose the state owned organization Femern A/S has been established. A feasibility study in 1996-1999 looked into a great number of possible solutions, including bridge and tunnel (immersed and bored) options, train shuttles, double and four lane motorways, single and double track rail, integrated or seperated from the motorway. On the basis of the study it was decided to construct a four-lane motorway and a double track railway. A cable-stayed bridge was favoured and the Danish and German Governments labelled this as the preferred solution. However, it was decided that an immersed tube tunnel alternative for the entire crossing had to be investigated during the planning stage. Variants which combine in-line or parallel bridge-tunnel combinations were not considered due to the great waterdepth, which would require a huge reclamation to
connect the bridge and tunnel for the in line option; and for economical reasons for the parallel arrangement. The final decision between either a bridge or a tunnel was to be taken only after it had become clear that both options were technically feasible and necessary approvals could be obtained.
In April 2009, Femern A/S selected the Rambøll-Arup-TEC JV for the design of the tunnel alternative.
The immersed tunnel solution will set new records in terms of its dimensions; it will be the longest tunnel and one of the deepest tunnels of this type ever built with a length of 20km and foundation depths reaching more than 40m under the sea surface. The size of the project will create major challenges for designers and future contractors and will allow for an innovative approach based on proven technology.
If constructed, the immersed tunnel, will also be the world’s longest combined road and rail tunnel; the world’s longest under water tunnel for road; and the deepest immersed tunnel with road and rail traffic. The size of the project is about five times the tunnel part of the Øresund Link between Denmark and Sweden and will require a huge logistical and qualitative challenge to build in the available construction time of approximately six years. The amount of material to be dredged for the trench is about 20 million m3 and the amount of concrete for the immersed tube elements is about 3 million m3. Production of the elements would require four to five construction facilities as used for the Øresund Link.
Operational safety in a tunnel of this length is a challenge and requires careful
Fig 1. Integration of the road and rail Fehmarnbelt fixed link
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