Undersea tunnel

An undersea tunnel is a tunnel which is partly or wholly constructed under the sea or an estuary. They are often used where building a bridge or operating a ferry link is unviable, 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.

Tunneling makes excavated soil available that can be used to create new land (see land reclamation). This was done with the rock excavated for the Channel Tunnel, which was used to create Samphire Hoe.

Further information: Tunnel § Choice of tunnels versus 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 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
Tunnel PlaceDescriptionDistanceDepth (from surface)Constructed in
Thames Tunnel London, EnglandThe oldest underwater tunnel in the world, crossing the Thames in London0.4 km1825–1843
Mersey Railway Tunnel Liverpool, EnglandThe oldest underwater rail tunnel in the world, crossing the Mersey in Liverpool1.21 km1881–1886
Severn Tunnel Wales – EnglandOne of the oldest underwater tunnels in the world7.01 km1873–1886
Blackwall Tunnel (western) London, EnglandThe oldest underwater vehicular tunnel in the world, crossing the Thames in London1.35 km1892–1897
Elbe Tunnel (1911) Hamburg, GermanyPioneering underwater pedestrian and vehicular tunnel, crossing the Elbe River in Hamburg0.426 km24 m1907–1911
Holland Tunnel New York – New Jersey, USAThe longest continuous underwater vehicular tunnel in the world when first built, crossing the Hudson River between Manhattan and Jersey City2.6 km28.3 m1920–1927
Queensway Tunnel Liverpool, EnglandThe longest vehicular tunnel of any type in the world when first built, crossing the River Mersey between Liverpool and Birkenhead3.24 km1925–1934
Bankhead Tunnel Mobile, AlabamaCarries 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 tunnel1.033 km12.2m1938–1942
Lincoln Tunnel New York, USASet of road tunnels built in three stages, crossing the Hudson River between Manhattan and New Jersey2.4 km average30 m1934–1957
George Massey Tunnel Vancouver, CanadaThe first tunnel in North America to use Immersed Tube technology0.629 km23 m1957-1959
Chesapeake Bay Bridge Tunnel Virginia, USAConnecting Virginia Beach with the Eastern Shore of Virginia1.6 km (tunnel section)1960–1964
Transbay Tube San Francisco – Oakland, USARail tunnel for Bay Area Rapid Transit. Connects Oakland to San Francisco. It is the longest underwater tunnel in North America5.8 km41 m1965–1969
Cross Harbour Tunnel Hong KongA busy road tunnel in Hong Kong1.86 km1969–1972
Elbe Tunnel (1975) Hamburg, Germany8-lane road tunnel crossing the Elbe River in Hamburg3.3 km1968–1975
Ahmed Hamdi Tunnel Suez, EgyptPasses under Suez Canal connecting the Asian Sinai Peninsula to the town of Suez on the African mainland1.63 km1979–1981
Vardø Tunnel Vardo, NorwayConnecting the small island community of Vardø in northern Norway to the mainland2.9 km88 m1979–1982
Kanonersky Tunnel Saint-Petersburg, Russiaconnecting Kanonersky Island to Kirovsky District of Saint-Petersburg through Neva Bay0.927 km1970-1983
Flekkerøy Tunnel Flekkerøy, NorwayConnecting the island community of Flekkerøy in southern Norway to the mainland2.3 km101 m1986–1989
Seikan Tunnel Seikan, JapanThe Seikan Tunnel is the world's longest tunnel with an undersea segment.53.8 km1971–1988
Sydney Harbour Tunnel Sydney, Australia2.8 km1988–1992
Channel Tunnel England – FranceThe world's longest undersea portion railway tunnel (37.9km underwater length)50.4 km1988–1994
Hitra Tunnel Trøndelag, NorwayThe deepest in the world at the time of construction5.6 km264 m1992–1994
Tokyo Bay Aqua-Line Tokyo, JapanThe world's longest undersea portion road tunnel9.6 km1988–1997
North Cape Tunnel Magerøya, NorwayThe 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 Tunnel Føyno – Sveio, NorwayThe deepest point of the International E-road network. Connects Stord municipality to the Norwegian mainland. 7.8 km260.4 m1997–2000
Eiksund Tunnel Møre og Romsdal, NorwayThe world's second deepest undersea road tunnel (before 2019 world's deepest)7.7 km287 m2003–2008
Xiamen Xiang'an Tunnel Xiamen, China6.05 km70 m2005–2010
Busan–Geoje Fixed Link Busan – Geoje, South Korea3.7 km48 m2008–2010
Qingdao Jiaozhou Bay Tunnel Hangdao – Qingdao, China7.808 km84.2 m2006–2011
Marmaray Istanbul (Bosphorus strait), TurkeyRail tunnel connecting Asia and Europe in Istanbul1.39 km (Undersea section)2004–2013
Marina Coastal Expressway SingaporeSingapore's first undersea tunnel5 km2008–2013
Port of Miami Tunnel Miami, USA2.1 km2010–2014
Eurasia Tunnel Istanbul (Bosphorus strait), TurkeyRoad tunnel connecting Asia and Europe in Istanbul5.4 km106 m2011–2016
Hong Kong–Zhuhai–Macau Bridge Hong Kong – Macau, China55 km-long sea crossing between Hong Kong, Macau and Zhuhai, China6.7 km (tunnel section)2009–2018
Ryfylke Tunnel Stavanger – Ryfylke, NorwayThe longest and deepest undersea tunnel for cars, from Stavanger to Ryfylke14.3 km293 m2013–2020
Riachuelo Lot 3 Tunnel Buenos Aires, ArgentinaOutfall tunnel of the Riachuelo System - Third world's longest undersea tunnel excavated with TBM12 km48 m2017–2019

Proposed

Road
  • Eysturoyartunnilin, Faroe Islands to be opened in 2020. The tunnel will have three entrances connected by an underwater roundabout.[3] 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 11.24 km of sub sea tunnel.[4]
  • Rogfast tunnel in Norway – construction having started in 2018, at 27 km length, 392 m depth, it will be the longest road tunnel and deepest undersea tunnel in the world.
  • Underwater Road Tunnel Salamina island-Perama - planned road tunnel in Attica, Greece. Currently at the second stage of the tender from which the concessionaire will be selected.[5][6]

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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. "Eysturoyartunnilin verður liðugur í 2019". sjovarkommuna.fo. Archived from the original on June 13, 2018.
  4. "The Eysturoy tunnel". Eystur- og Sandoyatunlar.
  5. "Undersea Road Tunnel Salamina island - Perama". ec.europa.eu. Retrieved 2020-05-13.
  6. Καραγιάννης, Νίκος (2020-05-12). "Design for Salamina island undersea road tunnel, finalized". Ypodomes.com (in Greek). Retrieved 2020-05-13.
  7. "我市全国人大代表返连努力创造属于新时代的光辉业绩_大连新闻_时政经济_大连天健网". dalian.runsky.com. Archived from the original on July 28, 2018.
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