Difference between revisions of "Tunnel" - New World Encyclopedia
From New World Encyclopedia
({{Paid}}) |
m (Protected "Tunnel": Copyedited [edit=sysop:move=sysop]) |
||
| Line 1: | Line 1: | ||
| − | {{Claimed}}{{Contracted}}{{Images OK}}{{Submitted}}{{Approved}}{{Paid}} | + | {{Copyedited}}{{Claimed}}{{Contracted}}{{Images OK}}{{Submitted}}{{Approved}}{{Paid}} |
| − | [[Image:Disused railway tunnel.jpg|right|thumb| | + | [[Image:Disused railway tunnel.jpg|right|thumb|250px|A disused railway tunnel now converted to pedestrian and bicycle use, near Houyet, [[Belgium]]]] |
| + | [[Image:LightTunnelDetroit.jpg|thumb|right|250px|Colorful pedestrian "Light Tunnel" connecting two terminals in Detroit Metropolitan Wayne County Airport (USA)]] | ||
| + | A '''tunnel''' is an underground passage. The definition of what constitutes a tunnel is not universally agreed upon. However, in general, tunnels are at least twice as long as they are wide. In addition, they should be completely enclosed on all sides, save for the openings at each end. | ||
| − | A | + | A tunnel may be for [[pedestrian]]s or [[cycling|cyclists]], for general road traffic, for [[motor vehicle]]s only, for [[rail transport|rail]] traffic, or for a [[canal]]. Some are [[aqueduct]]s, constructed purely for [[water supply|carrying water]]—for consumption, for [[hydroelectric]] purposes or as sewers—while others carry other utility services such as [[telecommunication]] cables. Some tunnels are designed as wildlife crossings. Some secret tunnels have been built to provide means of or escape from an area, such as the Cu Chi Tunnels. |
| − | + | In the [[United Kingdom]], a pedestrian tunnel or other underpass beneath a road is called a subway. This term was also used in the past in the [[United States]], but it now refers to underground [[rapid transit]] systems. The longest canal tunnel is the [[Standedge Tunnels|Standedge Tunnel]]* in the United Kingdom, which stretches over three miles. | |
| − | |||
| − | + | [[Image:North east Line tunnels.jpg|right|thumb|250px|The North East MRT Line in [[Singapore]] is a fully-underground rail line]] | |
| − | [[Image:North east Line tunnels.jpg|right|thumb|250px|The | ||
== Tunnels for different purposes == | == Tunnels for different purposes == | ||
| − | * '''Rapid transit networks:''' The central part of a rapid transit network is usually built in tunnels. To allow non-level crossings, some lines run in deeper tunnels than others. At metro stations there are usually pedestrian tunnels from one | + | * '''Rapid transit networks:''' The central part of a rapid transit network is usually built in tunnels. To allow non-level crossings, some lines run in deeper tunnels than others. At metro stations there are usually pedestrian tunnels from one platform to another. Often, ground-level [[train station|railway stations]] also have one or more pedestrian tunnels under the railway to enable passengers to reach the platforms without having to walk across the tracks. However, in the United Kingdom, [[bridge]]s are an equally popular method of pedestrian access between two or more different [[railway station]] platforms. |
* '''Overbridges:''' An overbridge can sometimes be built by covering a road, river, or railway with brick or still arches, then leveling the surface with earth. In railway parlance, a surface-level track that has been built or covered over is called a covered way. | * '''Overbridges:''' An overbridge can sometimes be built by covering a road, river, or railway with brick or still arches, then leveling the surface with earth. In railway parlance, a surface-level track that has been built or covered over is called a covered way. | ||
| − | * '''Protection for railways:''' A | + | * '''Protection for railways:''' A snow shed is a kind of tunnel built to protect a railway from avalanches of snow. Likewise, the Stanwell Park, New South Wales '''steel tunnel''' on the Nowra, New South Wales railway line protects the line from falling rock. |
| − | * '''Utility ducts:''' | + | * '''Utility ducts:''' Utility ducts are man-made tunnels created to carry two or more utility lines underground. Through co-location of different utilities in one tunnel, governments and companies are able to reduce the costs of building and maintaining utilities. |
| − | * '''Underground bunkers:''' The construction of underground bunkers and other habitable areas are often associated with | + | * '''Underground bunkers:''' The construction of underground bunkers and other habitable areas are often associated with military use during armed conflict, or civilian responses to the threat of attack. |
| − | == Choice of tunnels vs. bridges == | + | == Choice of tunnels vs. bridges == |
| − | For water crossings, a tunnel is generally more costly to construct than a bridge. However, navigational considerations may limit the use of high bridges or [[drawbridge]] spans when intersecting with shipping channels at some locations, necessitating use of a tunnel. Additionally, bridges usually require a larger footprint on each shore than tunnels; in areas with particularly expensive real estate, such as [[Manhattan]] and urban [[Hong Kong]], this is a strong factor in tunnels | + | For water crossings, a tunnel is generally more costly to construct than a bridge. However, navigational considerations may limit the use of high bridges or [[drawbridge]] spans when intersecting with shipping channels at some locations, necessitating use of a tunnel. Additionally, bridges usually require a larger footprint on each shore than tunnels; in areas with particularly expensive real estate, such as [[New York City|Manhattan]] and urban [[Hong Kong]], this is a strong factor in favor of tunnels. Boston's Big Dig project replaced elevated roadways with a tunnel system in order to increase traffic capacity, hide traffic, reclaim land, redecoration, and reunite the city with the waterfront. |
| − | Examples of water-crossing tunnels built instead of bridges include the [[Holland Tunnel]] and [[Lincoln Tunnel]] between [[New Jersey]] and Manhattan in [[New York City]], and the | + | Examples of water-crossing tunnels built instead of bridges include the [[Holland Tunnel]] and [[Lincoln Tunnel]] between [[New Jersey]] and Manhattan in [[New York City]], and the Elizabeth River tunnels between Norfolk and Portsmouth, Virginia and the [http://www.westerscheldetunnel.nl Westerscheldetunnel], Zeeland, Netherlands. |
| − | Other reasons for choosing a tunnel instead of a bridge are aesthetic reasons (i.e. preserve the above-ground view, landscape, and scenery) | + | Other reasons for choosing a tunnel instead of a bridge are aesthetic reasons (i.e. preserve the above-ground view, landscape, and scenery) and also for weight capacity reasons (it may be more feasible to build a tunnel than a sufficiently strong bridge). |
| − | Some water crossings are a mixture of bridges and tunnels, such as the | + | Some water crossings are a mixture of bridges and tunnels, such as the Oresund Bridge that links Denmark to Sweden and the Chesapeake Bay Bridge-Tunnel in the eastern [[United States]]. |
==Construction== | ==Construction== | ||
| − | [[Image:CH Gotthard Basistunnel Amsteg 1.jpg|thumb| | + | [[Image:CH Gotthard Basistunnel Amsteg 1.jpg|thumb|250px|right|Gotthard Base Tunnel under construction]] |
| − | [[Image:Tunnel Boring Machine (Yucca Mt).jpg|thumb|right| | + | [[Image:Tunnel Boring Machine (Yucca Mt).jpg|thumb|right|250px|A tunnel boring machine that was used at Yucca Mountain, [[Nevada]]]] |
Tunnels are dug in various types of materials, from soft clays to hard rocks, and the method of excavation heavily depends on the ground conditions. | Tunnels are dug in various types of materials, from soft clays to hard rocks, and the method of excavation heavily depends on the ground conditions. | ||
| Line 41: | Line 41: | ||
'''Cut-and-cover''' is a simple method of construction for shallow tunnels where a [[trench]] is excavated and [[roof]]ed over. Strong supporting beams are necessary to avoid the danger of the tunnel collapsing. | '''Cut-and-cover''' is a simple method of construction for shallow tunnels where a [[trench]] is excavated and [[roof]]ed over. Strong supporting beams are necessary to avoid the danger of the tunnel collapsing. | ||
| − | Shallow tunnels are often of the cut-and-cover type (if under water, of the immersed-tube type), while deep tunnels are excavated, often using a | + | Shallow tunnels are often of the cut-and-cover type (if under water, of the immersed-tube type), while deep tunnels are excavated, often using a tunneling shield. For intermediate levels, both methods are possible. |
===Boring machines=== | ===Boring machines=== | ||
| − | '''[[Tunnel-boring machine]]s''' (TBMs) can be used to automate the entire tunneling process. There are a variety of TBMs that can operate in a variety of conditions. One type of TBM, called an earth-pressure balance machine, can be used deep below the [[water table]]. This pressurizes the cutter head with air or another fluid in order to balance the water pressure. As a result operators of the TBM must go through decompression chambers, much like divers. | + | '''[[Tunnel-boring machine]]s''' (TBMs) can be used to automate the entire tunneling process. There are a variety of TBMs that can operate in a variety of conditions. One type of TBM, called an earth-pressure balance machine, can be used deep below the [[water table]]. This pressurizes the cutter head with air or another fluid in order to balance the water pressure. As a result operators of the TBM must go through decompression chambers, much like divers. |
| − | |||
| − | Currently there are four even larger machines: two for the M30 ringroad in Madrid, Spain; two for the Chong Ming tunnels in Shanghai, China. These machines are 15.2 | + | Until recently the biggest TBM built was used to bore the Green Heart Tunnel (Dutch: Tunnel Groene Hart) as part of the HSL-Zuid in the Netherlands. Its diameter is 14.87 meters.<ref>[http://www.hslzuid.nl/hsl/uk/bouw/ment/Bored_Tunnel_Groene_Hart/index.jsp The Groene Hart Tunnel.] HSL-Zuid. Retrieved April 25, 2007.</ref> |
| + | |||
| + | Currently there are four even larger machines: two for the M30 ringroad in Madrid, Spain; two for the Chong Ming tunnels in [[Shanghai]], [[China]]. These machines are 15.2 meters and 15.4 meters in diameter, respectively.<ref>The two machines for Spain were built by Mitsubishi/Dura Fuelgo and [http://www.herrenknecht.com Herrenknecht]. The TBMs for China were built by Herrenknecht.</ref> | ||
===NATM=== | ===NATM=== | ||
| − | The ''' | + | The '''New Austrian Tunneling Method''' (NATM) was developed in the 1960s. The main idea of this method is to use the geological [[stress (physics)|stress]] of the surrounding [[Rock (geology)|rock]] [[mass]] to stabilize the tunnel itself. Based on geotechnical measurements, an optimal [[cross section (geometry)|cross section]] is computed. The excavation is immediately protected by thin [[shotcrete]], just behind the excavation. This creates a natural load-bearing ring, which minimizes the rock's [[deformation]]. |
| − | By special | + | By special monitoring the NATM method is very flexible, even at surprising changes of the [[geomechanics|geomechanical]] rock consistency during the tunneling work. The measured rock properties lead to appropriate [[tool]]s for tunnel [[Strength of materials|strengthening]]. In the last decades also soft ground excavations up to 10 kilometers became usual. |
=== Pipe jacking === | === Pipe jacking === | ||
| Line 62: | Line 63: | ||
===Underwater tunnels=== | ===Underwater tunnels=== | ||
| − | There are also several approaches to underwater tunnels, for instance an | + | There are also several approaches to underwater tunnels, for instance an immersed tube, as in Sydney Harbor. |
===Other=== | ===Other=== | ||
'''Other tunneling methods''' include: | '''Other tunneling methods''' include: | ||
| − | * | + | * Drilling and blasting |
| − | * Slurry- | + | * Slurry-shield machine |
| − | * | + | * Wall-cover construction method. |
==Examples of tunnels== | ==Examples of tunnels== | ||
===In history=== | ===In history=== | ||
| + | [[Image:Thamestunnel.jpg|thumb|right|250 px|Interior of the Thames Tunnel, [[London]], mid-nineteenth century]] | ||
| + | * The ''qanat'' or ''kareez'' of [[Persian Emprire|Persia]] is a water management system used to provide a reliable supply of water to human settlements or for irrigation in hot, arid and semi-arid climates. The oldest and largest known ''qanat'' is in the [[Iran|Iranian]] city of Gonabad, which after 2,700 years still provides drinking and agricultural water to nearly 40,000 people. Its main well depth is more than 360 meters and its length is 45 kilometers. | ||
| + | |||
| + | * The Eupalinian aqueduct on Samos Island ([[Ionia]]) was built around 520 B.C.E. by the Ionian engineer [[Eupalinos]]. Eupalinos organised the work so that the tunnel was begun from both sides of the hill and the two teams met in the middle. The estimates for the time required range from five to 15 years; the mountain is solid limestone and one has to suppose that many of the slaves doing the work died. | ||
| + | |||
| + | The tunnel's existence was recorded by [[Herodotus]] (as was the mole and harbor, and the third wonder of the island, the great temple to Hera, thought by many to be the largest in the Greek world). The precise location of the tunnel was only re-established in the nineteenth century by German [[archaeology|archaeologists]]. The tunnel proper is 1,030 meters (3,432 feet) long and visitors can still enter it.<ref>Hughes, Dan. [http://homepages.cwi.nl/~aeb/math/samos/ The Tunnel of Eupalinos.] Retrieved April 25, 2007.</ref> | ||
| + | |||
| + | * Sapperton Tunnel on the Thames & Severn Canal in [[England]], dug through hills, which opened in 1789, was 3.5 kilometers long and allowed [[ship]] transport of [[coal]]. Above it runs the Sapperton Long Tunnel which carries the "Golden Valley" railway line between Swindon and Gloucester. | ||
| − | + | * The tunnel created for the first true steam [[locomotive]], the Penydarren locomotive, was able to make his historic journey from Penydarren to Abercynon in 1804. Part of this tunnel can still be seen at Pentrebach, Merthyr Tydfil. This is arguably the oldest railway tunnel in the world, for self-propelled steam engines on rails. | |
| − | |||
| − | * | + | * Box Tunnel in England, which opened in 1841, was the longest railway tunnel in the world at the time of construction. It was dug and has a length of 2.9 kilometers. |
| − | + | ||
| − | + | * The Thames Tunnel, built by [[Marc Isambard Brunel]] and his son [[Isambard Kingdom Brunel]], opened in 1843 and was the first underwater tunnel and the first to use a tunnelling shield. Originally used as a foot-tunnel, it is now part of the East London Line of the [[London Underground]]. | |
| − | + | ||
| − | * The | + | * The Cobble Hill Tunnel and Murray Hill Tunnel in [[New York City]] are the world's oldest railway tunnels lying below streets, roofed over in 1850 and the 1850s, respectively. |
| − | * The | + | |
| − | * The oldest sections of the [[London Underground]] were built using the cut-and-cover method in the 1860s. The Metropolitan, Hammersmith | + | * The oldest sections of the [[London Underground]] were built using the cut-and-cover method in the 1860s. The Metropolitan, Hammersmith, Circle and District lines were the first to prove the success of a metro or subway system. |
| − | * | + | |
| + | * Col de Tende Road Tunnel, one of the first longer road tunnels under a pass. | ||
===The longest=== | ===The longest=== | ||
| − | *The | + | *The Seikan Tunnel in [[Japan]] is the longest rail tunnel in the world at 53.9 kilometers (33.4 miles), of which 23.3 kilometers (14.5 miles) is under the sea. |
| − | *The [[Channel Tunnel]] between [[France]] and [[England]] under the [[English Channel]] is the second-longest, with a total length of 50 | + | |
| − | *The | + | *The [[Channel Tunnel]] between [[France]] and [[England]] under the [[English Channel]] is the second-longest, with a total length of 50 kilometers (31 miles), of which 39 kilometers (24 miles) is under the sea. |
| − | *The | + | |
| − | *The | + | *The Lærdal Tunnel in [[Norway]] from Lærdal to Aurland is the world's longest road tunnel, intended for cars and similar vehicles, at 24.5 kilometers (15.2 miles). |
| − | *The | + | |
| − | *The | + | *The St. Gotthard Tunnel from Göschenen to Airolo in [[Switzerland]], opened on September 5, 1980, is the world's second longest [[highway]] tunnel at 16.32 kilometers (10.14 miles). |
| − | *The | + | |
| − | * | + | *The Ryfast road program in Stavanger, Norway includes the tunnel Solbakktunnelen, which is scheduled to be opened within 2015. This tunnel will be 14 kilometers long, making it both the world's longest underwater road tunnel and longest underwater highway tunnel. The tunnel will have four driving lanes in total, and a speed limit of 90 kilometers per hour. |
| + | |||
| + | *The Hsuehshan Tunnel in northern [[Taiwan]] opened on June 16, 2006 with a length of 12.955 kilometers (8.05 miles). This tunnel is the longest highway tunnel in Asia and the fourth in the world (as of 2006). | ||
| + | *The Rennsteig Tunnel in middle [[Germany]] runs under the Thuringian Forest over a length of 8.5 kilometers (5.2 miles) and is currently Germany's longest tunnel. The highway A71 connects Erfurt with Schweinfurt. | ||
| + | |||
| + | *The North Cape Tunnel in northern Norway, connecting the island of Magerøya with the mainland, was the world's longest undersea road tunnel when opened in 1999, at about 7 kilometers. It reaches a depth of 212 meters below sea level. | ||
| + | |||
| + | * Päijänne Water Tunnel is the world's longest complete tunnel that is bored into cliff. It is located in southern [[Finland]] and it is 120 kilometers long. Its purpose is to provide the greater [[Helsinki]] metropolitan area with fresh water. | ||
===Notable=== | ===Notable=== | ||
| − | *The [[Lincoln Tunnel]] between [[New Jersey]] and [[New York]] is one of the busiest vehicular tunnels in the world, at 120,000 vehicles | + | *The [[Lincoln Tunnel]] between [[New Jersey]] and [[New York]] is one of the busiest vehicular tunnels in the world, at 120,000 vehicles per day |
| − | *The | + | |
| − | + | *The Fredhälls Tunnel in [[Stockholm]], [[Sweden]] | |
| − | * | + | |
| − | *The | + | *New York City Water Tunnel No. 3, started in 1970, has an expected completion date of 2020.<ref>[http://www.nyc.gov/html/dep/html/news/3rdtunnel.html City Water Tunnel No. 3.] New York City Department of Environmental Protection. Retrieved April 25, 2007.</ref> |
| − | *The | + | *The Chicago Deep Tunnel Project is a network of 109 miles (197 kilometers) of tunnels designed to reduce flooding in the Chicago area. Started in the mid 1970s, the project is due to be completed in 2019. |
| − | *The | + | |
| + | *The Fenghuoshan Tunnel on Qinghai-Tibet railway is the world's highest railway tunnel. | ||
| + | |||
| + | *The Houston Downtown Tunnel System is a system of tunnels about twenty feet below [[Houston]], Texas's downtown street system. The system forms a network of subterranean, climate-controlled, pedestrian walkways that link 25 full city blocks. | ||
| + | |||
*The [[Sydney Harbour Tunnel]] in [[Sydney]], [[Australia]] was built in 1992 to augment the [[Sydney Harbour Bridge]]. | *The [[Sydney Harbour Tunnel]] in [[Sydney]], [[Australia]] was built in 1992 to augment the [[Sydney Harbour Bridge]]. | ||
| Line 112: | Line 132: | ||
* '''Snow tunnels''' are created by voles, chipmunks, and other rodents for protection and access to food sources. A tunnel built by an animal is called a [[burrow]]. | * '''Snow tunnels''' are created by voles, chipmunks, and other rodents for protection and access to food sources. A tunnel built by an animal is called a [[burrow]]. | ||
| − | * The | + | * The Punarjani Guha is a natural tunnel 15 meters long, in a rocky cliff in Kerala, [[India]]. |
| − | == | + | ==Notes== |
| − | + | <references /> | |
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
== References == | == References == | ||
| − | * Oxlade, Chris. 2001. ''Tunnels (Building Amazing Structures S.)''. Chicago | + | * Oxlade, Chris. 2001. ''Tunnels (Building Amazing Structures S.)''. Chicago: Heinemann Library. ISBN 043110980X |
| − | * Landau, Elaine. 2000. ''Tunnels (True Books : Buildings and Structures)''. New York | + | * Landau, Elaine. 2000. ''Tunnels (True Books : Buildings and Structures)''. New York: Children's Press (CT). ISBN 0516273256 |
| − | * Donovan, Sandra. 2003. ''The Channel Tunnel (Great Building Feats)''. Minneapolis, | + | * Donovan, Sandra. 2003. ''The Channel Tunnel (Great Building Feats)''. Minneapolis, M.N.: Lerner Publications. ISBN 0822546922 |
| − | * Moore, John Hammond. 2006. ''The Faustball Tunnel: German POWs in America And Their Great Escape''. Annapolis, | + | * Moore, John Hammond. 2006. ''The Faustball Tunnel: German POWs in America And Their Great Escape''. Annapolis, M.D.: Naval Institute Press. ISBN 1591145260 |
== External links == | == External links == | ||
| − | *[http://www.transglobalhighway.com Trans Global Highway | + | All retrieved April 25, 2007. |
| − | *[http://www.remuseum.org.uk/rem_his_engineer.htm Royal Engineers Museum] British Army | + | |
| − | * | + | *[http://www.transglobalhighway.com Trans Global Highway] – A proposal by Frank Didik |
| + | *[http://www.remuseum.org.uk/rem_his_engineer.htm#tunnel Royal Engineers Museum and Library] – History Section: British Army World War I Tunneling | ||
| + | *[http://home.no.net/lotsberg/index.html The World's Longest Tunnel Page] – Edited by Gunnar Lotsberg | ||
*[http://www.ita-aites.org ITA-AITES International Tunnelling Association] | *[http://www.ita-aites.org ITA-AITES International Tunnelling Association] | ||
Revision as of 22:22, 25 April 2007
A disused railway tunnel now converted to pedestrian and bicycle use, near Houyet, Belgium
A tunnel is an underground passage. The definition of what constitutes a tunnel is not universally agreed upon. However, in general, tunnels are at least twice as long as they are wide. In addition, they should be completely enclosed on all sides, save for the openings at each end.
A tunnel may be for pedestrians or cyclists, for general road traffic, for motor vehicles only, for rail traffic, or for a canal. Some are aqueducts, constructed purely for carrying water—for consumption, for hydroelectric purposes or as sewers—while others carry other utility services such as telecommunication cables. Some tunnels are designed as wildlife crossings. Some secret tunnels have been built to provide means of or escape from an area, such as the Cu Chi Tunnels.
In the United Kingdom, a pedestrian tunnel or other underpass beneath a road is called a subway. This term was also used in the past in the United States, but it now refers to underground rapid transit systems. The longest canal tunnel is the Standedge Tunnel in the United Kingdom, which stretches over three miles.
The North East MRT Line in Singapore is a fully-underground rail line
Tunnels for different purposes
- Rapid transit networks: The central part of a rapid transit network is usually built in tunnels. To allow non-level crossings, some lines run in deeper tunnels than others. At metro stations there are usually pedestrian tunnels from one platform to another. Often, ground-level railway stations also have one or more pedestrian tunnels under the railway to enable passengers to reach the platforms without having to walk across the tracks. However, in the United Kingdom, bridges are an equally popular method of pedestrian access between two or more different railway station platforms.
- Overbridges: An overbridge can sometimes be built by covering a road, river, or railway with brick or still arches, then leveling the surface with earth. In railway parlance, a surface-level track that has been built or covered over is called a covered way.
- Protection for railways: A snow shed is a kind of tunnel built to protect a railway from avalanches of snow. Likewise, the Stanwell Park, New South Wales steel tunnel on the Nowra, New South Wales railway line protects the line from falling rock.
- Utility ducts: Utility ducts are man-made tunnels created to carry two or more utility lines underground. Through co-location of different utilities in one tunnel, governments and companies are able to reduce the costs of building and maintaining utilities.
- Underground bunkers: The construction of underground bunkers and other habitable areas are often associated with military use during armed conflict, or civilian responses to the threat of attack.
Choice of tunnels vs. bridges
For water crossings, a tunnel is generally more costly to construct than a bridge. However, navigational considerations may limit the use of high bridges or drawbridge spans when intersecting with shipping channels at some locations, necessitating use of a tunnel. Additionally, bridges usually require a larger footprint on each shore than tunnels; in areas with particularly expensive real estate, such as Manhattan and urban Hong Kong, this is a strong factor in favor of tunnels. Boston's Big Dig project replaced elevated roadways with a tunnel system in order to increase traffic capacity, hide traffic, reclaim land, redecoration, and reunite the city with the waterfront.
Examples of water-crossing tunnels built instead of bridges include the Holland Tunnel and Lincoln Tunnel between New Jersey and Manhattan in New York City, and the Elizabeth River tunnels between Norfolk and Portsmouth, Virginia and the Westerscheldetunnel, Zeeland, Netherlands.
Other reasons for choosing a tunnel instead of a bridge are aesthetic reasons (i.e. preserve the above-ground view, landscape, and scenery) and also for weight capacity reasons (it may be more feasible to build a tunnel than a sufficiently strong bridge).
Some water crossings are a mixture of bridges and tunnels, such as the Oresund Bridge that links Denmark to Sweden and the Chesapeake Bay Bridge-Tunnel in the eastern United States.
Construction
.jpg)
A tunnel boring machine that was used at Yucca Mountain, Nevada
Tunnels are dug in various types of materials, from soft clays to hard rocks, and the method of excavation heavily depends on the ground conditions.
Cut-and-cover is a simple method of construction for shallow tunnels where a trench is excavated and roofed over. Strong supporting beams are necessary to avoid the danger of the tunnel collapsing.
Shallow tunnels are often of the cut-and-cover type (if under water, of the immersed-tube type), while deep tunnels are excavated, often using a tunneling shield. For intermediate levels, both methods are possible.
Boring machines
Tunnel-boring machines (TBMs) can be used to automate the entire tunneling process. There are a variety of TBMs that can operate in a variety of conditions. One type of TBM, called an earth-pressure balance machine, can be used deep below the water table. This pressurizes the cutter head with air or another fluid in order to balance the water pressure. As a result operators of the TBM must go through decompression chambers, much like divers.
Until recently the biggest TBM built was used to bore the Green Heart Tunnel (Dutch: Tunnel Groene Hart) as part of the HSL-Zuid in the Netherlands. Its diameter is 14.87 meters.[1]
Currently there are four even larger machines: two for the M30 ringroad in Madrid, Spain; two for the Chong Ming tunnels in Shanghai, China. These machines are 15.2 meters and 15.4 meters in diameter, respectively.[2]
NATM
The New Austrian Tunneling Method (NATM) was developed in the 1960s. The main idea of this method is to use the geological stress of the surrounding rock mass to stabilize the tunnel itself. Based on geotechnical measurements, an optimal cross section is computed. The excavation is immediately protected by thin shotcrete, just behind the excavation. This creates a natural load-bearing ring, which minimizes the rock's deformation.
By special monitoring the NATM method is very flexible, even at surprising changes of the geomechanical rock consistency during the tunneling work. The measured rock properties lead to appropriate tools for tunnel strengthening. In the last decades also soft ground excavations up to 10 kilometers became usual.
Pipe jacking
Pipe Jacking, also known as pipejacking or pipe-jacking, is a method of tunnel construction where hydraulic jacks are used to push specially made pipes through the ground behind a tunnel boring machine or shield.
Underwater tunnels
There are also several approaches to underwater tunnels, for instance an immersed tube, as in Sydney Harbor.
Other
Other tunneling methods include:
- Drilling and blasting
- Slurry-shield machine
- Wall-cover construction method.
Examples of tunnels
In history
Interior of the Thames Tunnel, London, mid-nineteenth century
- The qanat or kareez of Persia is a water management system used to provide a reliable supply of water to human settlements or for irrigation in hot, arid and semi-arid climates. The oldest and largest known qanat is in the Iranian city of Gonabad, which after 2,700 years still provides drinking and agricultural water to nearly 40,000 people. Its main well depth is more than 360 meters and its length is 45 kilometers.
- The Eupalinian aqueduct on Samos Island (Ionia) was built around 520 B.C.E. by the Ionian engineer Eupalinos. Eupalinos organised the work so that the tunnel was begun from both sides of the hill and the two teams met in the middle. The estimates for the time required range from five to 15 years; the mountain is solid limestone and one has to suppose that many of the slaves doing the work died.
The tunnel's existence was recorded by Herodotus (as was the mole and harbor, and the third wonder of the island, the great temple to Hera, thought by many to be the largest in the Greek world). The precise location of the tunnel was only re-established in the nineteenth century by German archaeologists. The tunnel proper is 1,030 meters (3,432 feet) long and visitors can still enter it.[3]
- Sapperton Tunnel on the Thames & Severn Canal in England, dug through hills, which opened in 1789, was 3.5 kilometers long and allowed ship transport of coal. Above it runs the Sapperton Long Tunnel which carries the "Golden Valley" railway line between Swindon and Gloucester.
- The tunnel created for the first true steam locomotive, the Penydarren locomotive, was able to make his historic journey from Penydarren to Abercynon in 1804. Part of this tunnel can still be seen at Pentrebach, Merthyr Tydfil. This is arguably the oldest railway tunnel in the world, for self-propelled steam engines on rails.
- Box Tunnel in England, which opened in 1841, was the longest railway tunnel in the world at the time of construction. It was dug and has a length of 2.9 kilometers.
- The Thames Tunnel, built by Marc Isambard Brunel and his son Isambard Kingdom Brunel, opened in 1843 and was the first underwater tunnel and the first to use a tunnelling shield. Originally used as a foot-tunnel, it is now part of the East London Line of the London Underground.
- The Cobble Hill Tunnel and Murray Hill Tunnel in New York City are the world's oldest railway tunnels lying below streets, roofed over in 1850 and the 1850s, respectively.
- The oldest sections of the London Underground were built using the cut-and-cover method in the 1860s. The Metropolitan, Hammersmith, Circle and District lines were the first to prove the success of a metro or subway system.
- Col de Tende Road Tunnel, one of the first longer road tunnels under a pass.
The longest
- The Seikan Tunnel in Japan is the longest rail tunnel in the world at 53.9 kilometers (33.4 miles), of which 23.3 kilometers (14.5 miles) is under the sea.
- The Channel Tunnel between France and England under the English Channel is the second-longest, with a total length of 50 kilometers (31 miles), of which 39 kilometers (24 miles) is under the sea.
- The Lærdal Tunnel in Norway from Lærdal to Aurland is the world's longest road tunnel, intended for cars and similar vehicles, at 24.5 kilometers (15.2 miles).
- The St. Gotthard Tunnel from Göschenen to Airolo in Switzerland, opened on September 5, 1980, is the world's second longest highway tunnel at 16.32 kilometers (10.14 miles).
- The Ryfast road program in Stavanger, Norway includes the tunnel Solbakktunnelen, which is scheduled to be opened within 2015. This tunnel will be 14 kilometers long, making it both the world's longest underwater road tunnel and longest underwater highway tunnel. The tunnel will have four driving lanes in total, and a speed limit of 90 kilometers per hour.
- The Hsuehshan Tunnel in northern Taiwan opened on June 16, 2006 with a length of 12.955 kilometers (8.05 miles). This tunnel is the longest highway tunnel in Asia and the fourth in the world (as of 2006).
- The Rennsteig Tunnel in middle Germany runs under the Thuringian Forest over a length of 8.5 kilometers (5.2 miles) and is currently Germany's longest tunnel. The highway A71 connects Erfurt with Schweinfurt.
- The North Cape Tunnel in northern Norway, connecting the island of Magerøya with the mainland, was the world's longest undersea road tunnel when opened in 1999, at about 7 kilometers. It reaches a depth of 212 meters below sea level.
- Päijänne Water Tunnel is the world's longest complete tunnel that is bored into cliff. It is located in southern Finland and it is 120 kilometers long. Its purpose is to provide the greater Helsinki metropolitan area with fresh water.
Notable
- The Lincoln Tunnel between New Jersey and New York is one of the busiest vehicular tunnels in the world, at 120,000 vehicles per day
- The Fredhälls Tunnel in Stockholm, Sweden
- New York City Water Tunnel No. 3, started in 1970, has an expected completion date of 2020.[4]
- The Chicago Deep Tunnel Project is a network of 109 miles (197 kilometers) of tunnels designed to reduce flooding in the Chicago area. Started in the mid 1970s, the project is due to be completed in 2019.
- The Fenghuoshan Tunnel on Qinghai-Tibet railway is the world's highest railway tunnel.
- The Houston Downtown Tunnel System is a system of tunnels about twenty feet below Houston, Texas's downtown street system. The system forms a network of subterranean, climate-controlled, pedestrian walkways that link 25 full city blocks.
- The Sydney Harbour Tunnel in Sydney, Australia was built in 1992 to augment the Sydney Harbour Bridge.
Natural tunnels
- Snow tunnels are created by voles, chipmunks, and other rodents for protection and access to food sources. A tunnel built by an animal is called a burrow.
- The Punarjani Guha is a natural tunnel 15 meters long, in a rocky cliff in Kerala, India.
Notes
- ↑ The Groene Hart Tunnel. HSL-Zuid. Retrieved April 25, 2007.
- ↑ The two machines for Spain were built by Mitsubishi/Dura Fuelgo and Herrenknecht. The TBMs for China were built by Herrenknecht.
- ↑ Hughes, Dan. The Tunnel of Eupalinos. Retrieved April 25, 2007.
- ↑ City Water Tunnel No. 3. New York City Department of Environmental Protection. Retrieved April 25, 2007.
ReferencesISBN links support NWE through referral fees
- Oxlade, Chris. 2001. Tunnels (Building Amazing Structures S.). Chicago: Heinemann Library. ISBN 043110980X
- Landau, Elaine. 2000. Tunnels (True Books : Buildings and Structures). New York: Children's Press (CT). ISBN 0516273256
- Donovan, Sandra. 2003. The Channel Tunnel (Great Building Feats). Minneapolis, M.N.: Lerner Publications. ISBN 0822546922
- Moore, John Hammond. 2006. The Faustball Tunnel: German POWs in America And Their Great Escape. Annapolis, M.D.: Naval Institute Press. ISBN 1591145260
External links
All retrieved April 25, 2007.
- Trans Global Highway – A proposal by Frank Didik
- Royal Engineers Museum and Library – History Section: British Army World War I Tunneling
- The World's Longest Tunnel Page – Edited by Gunnar Lotsberg
- ITA-AITES International Tunnelling Association
Credits
New World Encyclopedia writers and editors rewrote and completed the Wikipedia article in accordance with New World Encyclopedia standards. This article abides by terms of the Creative Commons CC-by-sa 3.0 License (CC-by-sa), which may be used and disseminated with proper attribution. Credit is due under the terms of this license that can reference both the New World Encyclopedia contributors and the selfless volunteer contributors of the Wikimedia Foundation. To cite this article click here for a list of acceptable citing formats.The history of earlier contributions by wikipedians is accessible to researchers here:
The history of this article since it was imported to New World Encyclopedia:
Note: Some restrictions may apply to use of individual images which are separately licensed.
