Undersea tunnel

An undersea tunnel is a tunnel which is partly or wholly constructed under a body of water. They are often used where building a bridge or operating a ferry link is impossible, or to provide competition or relief for existing bridges or ferry links.[1]

Advantages

Compared with bridges

One such advantage would be that a tunnel would still allow shipping to pass. A low bridge would need an opening or swing bridge to allow shipping to pass, which can cause traffic congestion. Conversely, a higher bridge that does allow shipping may be unsightly and opposed by the public. Higher bridges can also be more expensive than lower ones. Bridges can also be closed due to harsh weather such as high winds. Another possible advantage is space: the downward ramp leading to a tunnel leaves a smaller footprint compared to the upward ramps required by most bridges.

Tunneling will generate soil that has been excavated and this can be used to create new land, as was done with the soil of the Channel Tunnel.

Further information: Tunnel – Choice of tunnels vs. bridges

As with bridges, albeit with more chance, ferry links will also be closed during adverse weather. Strong winds or the tidal limits may also affect the workings of a ferry crossing. Travelling through a tunnel is significantly quicker than travelling using a ferry link, shown by the times for travelling through the Channel Tunnel (75–90 minutes for Ferry[2] and 21 minutes on the Eurostar). Ferries offer much less frequency and capacity and furthermore travel times tend to be longer with a ferry compared to a tunnel.

Disadvantages

Compared with bridges

Tunnels require far higher costs of security and construction than bridges. This may mean that over short distances bridges may be preferred rather than tunnels (for example Dartford Crossing). As stated earlier, bridges may not allow shipping to pass, so solutions such as the Øresund Bridge have been constructed.

As with bridges, ferry links are far cheaper to construct than tunnels, but not to operate. Also tunnels don't have the flexibility to be deployed over different routes as transport demand changes over time. Without the cost of a new ferry, the route over which a ferry provides transport can easily be changed.

List of notable examples

TunnelDescriptionDistanceDepth (from surface)Constructed in
Thames TunnelThe oldest underwater tunnel in the world, crossing the Thames in London0.4 km1825–1843
Severn TunnelOne of the oldest underwater tunnels in the world7.01 km1873–1886
Elbe Tunnel (1911)Pioneering underwater pedestrian and vehicular tunnel crossing the Elbe River in Hamburg, Germany0.426 km24 m1907-1911
Holland TunnelThe first modern underwater road tunnel in the world, crossing the Hudson River between Manhattan and Jersey City2.6 km28.3 m1920-1927
Queensway TunnelThe longest road tunnel of any type in the world when first built, crossing the River Mersey between Liverpool and Birkenhead3.24 km1925-1934
Bankhead TunnelCarries Hwy. 90 in Mobile, AL. Business District, to Blakely Island. The eastern end has large "flood door" that can be closed to prevent water from the Mobile Bay from flooding the tunnel during hurricanes or tropical storms. Two lanes that only allows cars and pick up trucks now to travel through the tunnel.1.033 km12.2m1938-1942
Lincoln TunnelSet of road tunnels built in three stages, crossing the Hudson River between Manhattan and New Jersey2.4 km average30 m1934-1957
Chesapeake Bay Bridge TunnelConnecting Virginia Beach with the Eastern Shore of Virginia1.6 km (tunnel section)1960–1964
Cross Harbour TunnelA busy road tunnel in Hong Kong1.86 km1969–1972
Elbe Tunnel (1975)8-lane road tunnel crossing the Elbe River in Hamburg, Germany3.3 km1968–1975
Ahmed Hamdi TunnelPasses under Suez Canal connecting the Asian Sinai Peninsula to the town of Suez on the African mainland1.63 km1979–1981
Vardø TunnelConnecting the small island community of Vardø in northern Norway to the mainland2.9 km88 m1979–1982
Seikan TunnelWorld's longest undersea railway tunnel when non-undersea portions of the tunnel are also measured53.9 km1971–1988
Sydney Harbour Tunnel2.8 km1988–1992
Channel TunnelWorld's longest undersea portion railway tunnel37.9 km1988–1994
Hitra TunnelThe deepest in the world at the time of construction5.6 km264 m1992–1994
Tokyo Bay Aqua-LineWorld's longest undersea portion road tunnel9.6 km1988–1997
North Cape TunnelThe tunnel goes under the Magerøysundet strait between the Norwegian mainland to the large island of Magerøya and the North Cape, Norway6.8 km212 m1993–1999
Bømlafjord TunnelThe deepest point of the International E-road network. Connects Stord municipality to the Norwegian mainland. 7.8 km260.4 m1997–2000
Eiksund TunnelWorld's deepest undersea road tunnel7.7 km287 m2003–2008
Busan–Geoje Fixed LinkWorld's deepest immersed road tunnel3.7 km48 m2008–2010
MarmarayRail tunnel connecting Asia and Europe in Istanbul13.6 km2004–2013
Marina Coastal ExpresswaySingapore's first undersea tunnel5 km2008–2013
Port of Miami Tunnel2.1 km2010–2014
Eurasia TunnelRoad tunnel connecting Asia and Europe in Istanbul5.4 km106 m2011–2016

Proposed

Road

  • Eysturoyartunnilin, Faroe Islands to be opened in 2020. The tunnel will have three entrances connected by an underwater roundabout. link The road length from Hvítanes to the roundabout will be 7.5 km, whilst the road length from the roundabout to Strendur and to Saltnes will be 1.7 km and 2.2 km, respectively. This results in an overall length of a 11.24 km of sub sea tunnel.[3]
  • Ryfylke tunnel – to be opened in 2019, 14.3 km length, 292 m depth
  • Rogfast – decided, construction to start in 2018, 27 km length, 392 m depth, will be longest road tunnel and deepest undersea tunnel in the world.

Rail

See also

References

  1. ↑ Sullivan, Walter. Progress In Technology Revives Interest In Great Tunnels, New York Times, June 24, 1986. Retrieved 15 August 2010.
  2. ↑ Dover–Calais Ferry Times, poferries.com website.
  3. ↑ http://www.estunlar.fo/fo/um-tunlarnar/eysturoyartunnilin/
  4. ↑ http://dalian.runsky.com/2018-03/21/content_5816155.htm
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