A tunnel is an underground passageway, dug through the surrounding soil/earth/rock and enclosed except for entrance and exit, commonly at each end. A pipeline is not a tunnel, though some recent tunnels have used immersed tube construction techniques rather than traditional tunnel boring methods.
A tunnel may be for foot or vehicular road traffic, for rail traffic, or for a canal. The central portions of a rapid transit network are usually in the tunnel. Some tunnels are aqueducts to supply water for consumption or for hydroelectric stations or are sewers. Utility tunnels are used for routing steam, chilled water, electrical power or telecommunication cables, as well as connecting buildings for convenient passage of people and equipment.
Secret tunnels are built for military purposes, or by civilians for smuggling of weapons, contraband, or people. Special tunnels, such as wildlife crossings, are built to allow wildlife to cross human-made barriers safely. Tunnels can be connected together in tunnel networks.
Contents
- 1 Terminology
- 2 History
- pipeline is not a tunnel, though some recent tunnels have used immersed tube construction techniques rather than traditional tunnel boring methods.
A tunnel may be for foot or vehicular road traffic, for rail traffic, or for a canal. The central portions of a rapid transit network are usually in the tunnel. Some tunnels are aqueducts to supply water for consumption or for hydroelectric stations or are sewers. Utility tunnels are used for routing steam, chilled water, electrical power or telecommunication cables, as well as connecting buildings for convenient passage of people and equipment.
Secret tunnels are built for military purposes, or by civilians for smuggling of weapons, contraband, or people. Special tunnels, such as wildlife crossings, are built to allow wildlife to cross human-made barriers safely. Tunnels can be connected together in tunnel networks.
Contents
- 1 Terminology
- 2 History
- 3 Geotechnical investigation and design
- 4 Construction
- 5 Variant tunnel types
- 5.1 Double-deck and multipurpose tunnels
- traffic, for rail traffic, or for a canal. The central portions of a rapid transit network are usually in the tunnel. Some tunnels are aqueducts to supply water for consumption or for hydroelectric stations or are sewers. Utility tunnels are used for routing steam, chilled water, electrical power or telecommunication cables, as well as connecting buildings for convenient passage of people and equipment.
Secret tunnels are built for military purposes, or by civilians for smuggling of weapons, contraband, or people. Special tunnels, such as wildlife crossings, are built to allow wildlife to cross human-made barriers safely. Tunnels can be connected together in tunnel networks.
A tunnel is relatively long and narrow; the length is often much greater than twice the diameter, although similar shorter excavations can be constructed, such as cross passages between tunnels.
The definition of what constitutes a tunnel can vary widely from source to source. For example, the definition of a road tunnel in the United Kingdom is defined as "a subsurface highway structure enclosed for a length of 150 metres (490 ft) or more."[1] In the United States, the NFPA definition of a tunnel is "An underground structure with a design length greater than 23 m (75 ft) and a diameter greater than 1,800 millimetres (5.9 ft)."[2]
In the UK, a pedestrian, cycle or animal tunnel beneath a road or railway is called a subway, while an underground railway system is differently named in different cities, the "Underground" or the "Tube" in London, the "Subway" in Glasgow, and the "Metro" in Newcastle. The place where a road, railway, canal or watercourse passes under a footpath, cycleway, or another road or railway is most commonly called a bridge or, if passing under a canal, an aqueduct. Where it is important to stress that it is passing underneath, it may be called an underpass, though the official term when passing under a railway is an underbridge. A longer underpass containing a road, canal or railway is normally called a "tunnel", whether or not it passes under another item of infrastructure. An underpass of any length under a river is also usually called a "tunnel", whatever mode of transport it is for.
In the US, the term "subway" means an underground rapid transit system, and the term pedestrian underpass is used for a passage beneath a barrier. Rail station platforms may be connected by pedestrian tunnels or footbridges.
History
![[icon]](//upload.wikimedia.org/wikipedia/commons/thumb/1/1c/Wiki_letter_w_cropped.svg/20px-Wiki_letter_w_cropped.svg.png)
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Joralemon Street Tunnel on 1913 postcard, part of the New York City Subway systemMuch of the early technology of tunneling evolved from mining and military engineering. The etymology of the terms "mining" (for mineral extraction or for siege attacks), "military engineering", and "civil engineering" reveals these deep historic connections.
Antiquity and early middle ages
Predecessors of modern tunnels were adits to transport water for irrigation or drinking, and sewerage. The first Qanats are known from before 2000 B.C.
The Tunnel of Eupalinos is a tunnel aqueduct 1,036 m (3,399 ft) long running through Mount Kastro in Samos, Greece, built in the 6th century BC to serve as an aqueduct. It is the second known tunnel to have been excavated from both ends, after the Siloam tunnel in the Palestinian neighbourhood of Silwan in eastern Jerusalem.
In Ethiopia, the Siqurto foot tunnel, hand-hewn in the middle ages, crosses a mountain ridge.
Geotechnical investigation and design
A major tunnel project must start with a comprehensive investigation of ground conditions by collecting samples from boreholes and by other geophysical techniques. An informed choice can then be made of machinery and methods for excavation and ground support, which
Predecessors of modern tunnels were adits to transport water for irrigation or drinking, and sewerage. The first Qanats are known from before 2000 B.C.
The Tunnel of Eupalinos is a tunnel aqueduct 1,036 m (3,399 ft) long running through Mount Kastro in Samos, The Tunnel of Eupalinos is a tunnel aqueduct 1,036 m (3,399 ft) long running through Mount Kastro in Samos, Greece, built in the 6th century BC to serve as an aqueduct. It is the second known tunnel to have been excavated from both ends, after the Siloam tunnel in the Palestinian neighbourhood of Silwan in eastern Jerusalem.
In Ethiopia, the Siqurto foot tunnel, hand-hewn in the middle ages, crosses a mountain ridge.
A major tunnel project must start with a comprehensive investigation of ground conditions by collecting samples from boreholes and by other geophysical techniques. An informed choice can then be made of machinery and methods for excavation and ground support, which will reduce the risk of encountering unforeseen ground conditions. In planning the route, the horizontal and vertical alignments can be selected to make use of the best ground and water conditions. It is common practice to locate a tunnel deeper than otherwise would be required, in order to excavate through solid rock or other material that is easier to support during construction.
Conventional desk and preliminary site studies may yield insufficient information to assess such factors as the blocky nature of rocks, the exact location of fault zones, or the stand-up times of softer ground. This may be a particular concern in large-diameter tunnels. To give more information, a pilot tunnel (or "drift tunnel") may be driven ahead of the main excavation. This smaller tunnel is less likely to collapse catastrophically should unexpected conditions be met, and it can be incorporated into the final tunnel or used as a backup or emergency escape pas
Conventional desk and preliminary site studies may yield insufficient information to assess such factors as the blocky nature of rocks, the exact location of fault zones, or the stand-up times of softer ground. This may be a particular concern in large-diameter tunnels. To give more information, a pilot tunnel (or "drift tunnel") may be driven ahead of the main excavation. This smaller tunnel is less likely to collapse catastrophically should unexpected conditions be met, and it can be incorporated into the final tunnel or used as a backup or emergency escape passage. Alternatively, horizontal boreholes may sometimes be drilled ahead of the advancing tunnel face.
Other key geotechnical factors:
The Harbor Tunnel in Baltimore, which carries I-895, serves as an example of a water-crossing tunnel built instead of a bridge.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 intersecting with shipping channels, necessitating a tunnel.
Bridges usually require a larger footprint on each shore than tunnels. In areas with expensive real estate, such as Manhattan and urban Hong Kong, this is a strong factor in favor of a tunnel. Boston's Big Dig project replaced elevated roadways with a tunnel system to increase traffic capacity, hide traffic, reclaim land, redecorate, and reunite the city with the waterfront.
The 1934 Queensway Tunnel under the River Mersey at Liverpool was chosen over a massively high bridge for defense reasons; it was feared that aircraft could destroy a bridge in times of war. Maintenance cos
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 intersecting with shipping channels, necessitating a tunnel.
Bridges usually require a larger footprint on each shore than tunnels. In areas with expensive real estate, such as Manhattan and urban Hong Kong, this is a strong factor in favor of a tunnel. Boston's Big Dig project replaced elevated roadways with a tunnel system to increase traffic capacity, hide traffic, reclaim land, redecorate, and reunite the city with the waterfront.
The 1934 Queensway Tunnel under the River Mersey at Liverpool was chosen over a massively high bridge for defense reasons; it was feared that aircraft could destroy a bridge in times of war. Maintenance costs of a massive bridge to allow the world's largest ships to navigate under were considered higher than for a tunnel. Similar conclusions were reached for the 1971 Kingsway Tunnel under the Mersey. In Manhattan and urban Hong Kong, this is a strong factor in favor of a tunnel. Boston's Big Dig project replaced elevated roadways with a tunnel system to increase traffic capacity, hide traffic, reclaim land, redecorate, and reunite the city with the waterfront.
The 1934 Queensway Tunnel under the River Mersey at Liverpool was chosen over a massively high bridge for defense reasons; it was feared that aircraft could destroy a bridge in times of war. Maintenance costs of a massive bridge to allow the world's largest ships to navigate under were considered higher than for a tunnel. Similar conclusions were reached for the 1971 Kingsway Tunnel under the Mersey. In Hampton Roads, Virginia, tunnels were chosen over bridges for strategic considerations; in the event of damage, bridges might prevent US Navy vessels from leaving Naval Station Norfolk.
Water-crossing tunnels built instead of bridges include the Holland Tunnel and Lincoln Tunnel between New Jersey and Manhattan in New York City; the Queens-Midtown Tunnel between Manhattan and the borough of Queens on Long Island; the Detroit-Windsor Tunnel between Michigan and Ontario; and the Elizabeth River tunnels between Norfolk and Portsmouth, Virginia; the 1934 River Mersey road Queensway Tunnel; the Western Scheldt Tunnel, Zeeland, Netherlands; and the North Shore Connector tunnel in Pittsburgh, Pennsylvania.
Other reasons for choosing a tunnel instead of a bridge include avoiding difficulties with tides, weather, and shipping during construction (as in the 51.5-kilometre or 32.0-mile Channel Tunnel), aesthetic reasons (preserving 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 Denmark to Sweden link and the Chesapeake Bay Bridge-Tunnel in Virginia.
There are particular hazards with tunnels, especially from vehicle fires when combustion gases can asphyxiate users, as happened at the Gotthard Road Tunnel in Switzerland in 2001. One of the worst railway disasters ever, the Balvano train disaster, was caused by a train stalling in the Armi tunnel in Italy in 1944, killing 426 passengers. Designers try to reduce these risks by installing emergency ventilation systems or isolated emergency escape tunnels parallel to the main passage.
Government funds are often required for the creation of tunnels.[6] When a tunnel is being planned or constructed, economics and politics play a large factor in the decision making process. Civil engineers usually use project management techniques for developing a major structure. Understanding the amount of time the project requires, and the amount of labor and materials needed is a crucial part of project planning. The project duration must be identified using a work breakdown structure (WBS) and critical path method (CPM). Also, the land needed for excavation and construction staging, and the proper machinery must be selected. Large infrastructure projects require millions or even billions of dollars, involving long-term financing, usually through issuance of bonds.
The costs and benefits for an infrastructure such as a tunnel must be identified. Political disputes can occur, as in 2005 when the US House of Representatives approved a $100 million federal grant to build a tunnel under New York Harbor. However, the costs and benefits for an infrastructure such as a tunnel must be identified. Political disputes can occur, as in 2005 when the US House of Representatives approved a $100 million federal grant to build a tunnel under New York Harbor. However, the Port Authority of New York and New Jersey was not aware of this bill and had not asked for a grant for such a project.[7] Increased taxes to finance a large project may cause opposition.[8]
Tunnels are dug in types of materials varying from soft clay to hard rock. The method of tunnel construction depends on such factors as the ground conditions, the groundwater conditions, the length and diameter of the tunnel drive, the depth of the tunnel, the logistics of supporting the tunnel excavation, the final use and the shape of the tunnel and appropriate risk management.
There are three basic types of tunnel construction in common use. Cut-and-cover tunnels are constructed in a shallow trench and then covered over. Bored tunnels are constructed in situ, without removing the ground above. Finally, a tube can be sunk into a body of water, which is called an immersed tunnel.
Cut-and-cover
The New Austrian Tunnelling method (NATM)—also referred to as the Sequential Excavation Method (SEM)[14]—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, by allowing a measured relaxation and stress reassignment into the surrounding rock to prevent full loads becoming imposed on the supports. Based on geotechnical<
Once construction is complete, construction access shafts are often used as ventilation shafts, and may also be used as emergency exits.
The New Austrian Tunnelling method (NATM)—also referred to as the Sequential Excavation Method (SEM)[14]—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, by allowing a measured relaxation and stress reassignment into the surrounding rock to prevent full loads becoming imposed on the supports. Based on geotechnical measurements, an optimal cross section is computed. The excavation is protected by a layer of sprayed concrete, commonly referred to as shotcrete. Other support measures can include steel arches, rock bolts, and mesh. Technological developments in sprayed concrete technology have resulted in steel and polypropylene fibers being added to the concrete mix to improve lining strength. This creates a natural load-bearing ring, which minimizes the rock's deformation.[14]
monitoring the NATM method is 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.[14]
Pipe jacking
In pipe jacking, hydraulic jacks are used to push specially made pipes through the ground behind a TBM or shield. This method is commonly used to create tunnels under existing structures, such as roads or railways. Tunnels constructed by pipe jacking are normally small diameter bores with a maximum size of around 3.2 metres (10 ft).
Box jacking
Box jacking is similar to pipe jacking, but instead of jacking tubes, a box-shaped tunnel is used. Jacked boxes can be a much larger span than a pipe jack, with the s
Box jacking is similar to pipe jacking, but instead of jacking tubes, a box-shaped tunnel is used. Jacked boxes can be a much larger span than a pipe jack, with the span of some box jacks in excess of 20 metres (66 ft). A cutting head is normally used at the front of the box being jacked, and spoil removal is normally by excavator from within the box. Recent developments of the Jacked Arch and Jacked deck have enabled longer and larger structures to be installed to close accuracy. The 126m long 20m clear span underpass below the high-speed rail lines at Cliffsend in Kent, UK is an example of this technique[citation needed].
Underwater tunnels
During construction of a tunnel it is often convenient to install a temporary railway, particularly to remove excavated spoil, often narrow gauge so that it can be double track to allow the operation of empty and loaded trains at the same time. The temporary way is replaced by the permanent way at completion, thus explaining the term "Perway".
Enlargement
excavated spoil, often narrow gauge so that it can be double track to allow the operation of empty and loaded trains at the same time. The temporary way is replaced by the permanent way at completion, thus explaining the term "Perway".
Enlargement
The vehicles or traffic using a tunnel can outgrow it, requiring replacement or enlargement:- The original single line Gib Tunnel near Mittagong was replaced with a double-track tunnel, with the original tunnel used for growing mushrooms.[15][16]
- The 1832 double-track mile-long tunnel from Edge Hill to Lime Street in Liverpool was near totally removed, apart from a 50-metre section at Edge Hill and a section nearer to Lime Street, as four tracks were required. The tunnel was dug out into a very deep four-track cutting, with short tunnels in places along the cutting. Train services were not interrupted as the work progressed.An open building pit consists of a horizontal and a vertical boundary that keeps groundwater and soil out of the pit. There are several potential alternatives and combinations for (horizontal and vertical) building pit boundaries. The most important difference with cut-and-cover is that the open building pit is muted after tunnel construction; no roof is placed.
Other construction methods
- Drilling and blasting
- Hydraulic splitter
- Slurry-shield machine
- Wall-cover construction method.
Variant tunnel types
Double-deck and multipurpose tunnels
The upper-level traffic lanes through Yerba Buena Island, part of the San Francisco–Oakland Bay BridgeSome tunnels are double-deck, for example, the two major segments of the San Francisco–Oakland Bay Bridge (completed in 1936) are linked by a 540-foot (160 m) double-deck tunnel section through Yerba Buena Island, the largest-diameter bored tunnel in the world.[21] At construction this was a combination bidirectional rail and truck pathway on the lower deck with automobiles above, now converted to one-way road vehicle traffic on each deck.
In Turkey, the Eurasia Tunnel under the Bosphorus, opened in 2016, has at its core a 5.4 km (3.4 mi) two-deck road tunnel with two lanes on each deck.[22]
Additionally, in 2015 the Turkish government announced that it will build the world's first three-level tunnel, also under the Bosporus.[23] The tunnel is intended to carry both the Istanbul metro and a two-level highway, over a length of 6.5 km (4.0 mi).The French A86 Duplex Tunnel in west Paris consists of two bored tunnel tubes, the eastern one of which has two levels for light motorized vehicles, over a length of 10 km (6.2 mi). Although each level offers a physical height of 2.54 m (8.3 ft), only traffic up to 2 m (6.6 ft) tall is allowed in this tunnel tube, and motorcyclists are directed to the other tube. Each level was built with a three-lane roadway, but only two lanes per level are used – the third serves as a hard shoulder within the tunnel. The A86 Duplex is Europe's longest double-deck tunnel.
In Shanghai, China, a 2.8 km (1.7 mi) two-tube double-deck tunnel was built starting in 2002. In each tube of the Fuxing Road Tunnel both decks are for motor vehicles. In each direction, only cars and taxis travel on the 2.6 m (8.5 ft) high two-lane upper deck, and heavier vehicles, like trucks and buses, as well as cars, may use the 4.0 m (13 ft) high single-lane lower level.[24]
In the Netherlands, a 2.3 km (1.4 mi) two-storey, eight-lane, cut-and-cover road tunnel under the city of Maastricht was opened in 2016.In Turkey, the Eurasia Tunnel under the Bosphorus, opened in 2016, has at its core a 5.4 km (3.4 mi) two-deck road tunnel with two lanes on each deck.[22]
Additionally, in 2015 the Turkish government announced that it will build the world's first three-level tunnel, also under the Bosporus.[23] The tunnel is intended to carry both the Istanbul metro and a two-level highway, over a length of 6.5 km (4.0 mi).The French A86 Duplex Tunnel in west Paris consists of two bored tunnel tubes, the eastern one of which has two levels for light motorized vehicles, over a length of 10 km (6.2 mi). Although each level offers a physical height of 2.54 m (8.3 ft), only traffic up to 2 m (6.6 ft) tall is allowed in this tunnel tube, and motorcyclists are directed to the other tube. Each level was built with a three-lane roadway, but only two lanes per level are used – the third serves as a hard shoulder within the tunnel. The A86 Duplex is Europe's longest double-deck tunnel.
In Shanghai, China, a 2.8 km (1.7 mi) two-tube double-deck tunnel was built starting in 2002. In each tube of the Fuxing Road Tunnel both decks are for motor vehicles. In each direction, only cars and taxis travel on the 2.6 m (8.5 ft) high two-lane upper deck, and heavier vehicles, like trucks and buses, as well as cars, may use the 4.0 m (13 ft) high single-lane lower level.[24]
In the Netherlands, a 2.3 km (1.4 mi) two-storey, eight-lane, cut-and-cover road tunnel under the city of Maastricht was opened in 2016.[25] Each level accommodates a full height, two by two-lane highway. The two lower tubes of the tunnel carry the A2 motorway, which originates in Amsterdam, through the city; and the two upper tubes take the N2 regional highway for local traffic.[26]
The Alaskan Way Viaduct replacement tunnel, is a $3.3 billion 1.76-mile (2.83 km), double-decker bored highway tunnel under Downtown Seattle. Construction began in July 2013 using "Bertha", at the time the world's largest earth pressure balance tunnel boring machine, with a 57.5-foot (17.5 m) cutterhead diameter. After several delays, tunnel boring was completed in April 2017, and the tunnel opened to traffic on February 4, 2019.
New York City's 63rd Street Tunnel under the East River, between the boroughs of Manhattan and Queens, was intended to carry subway trains on the upper level and Long Island Rail Road commuter trains on the lower level. Construction started in 1969,[27] and the two sides of the tunnel were bored through in 1972.[28] The upper level, used by the IND 63rd Street Line (F and <F> trains) of the New York City Subway, was not opened for passenger service until 1989.[29] The lower level, intended for commuter rail, will not see passenger service until completion of the East Side Access project, expected in late 2022.[30]
In the UK, the 1934 Queensway Tunnel under the River Mersey between Liverpool and Birkenhead was originally to have road vehicles running on the upper deck and trams on the lower. During construction the tram usage was cancelled. The lower section is only used for cables, pipes and emergency accident refuge enclosures.
Hong Kong's Lion Rock Tunnel, built in the mid 1960s, connecting New Kowloon and Sha Tin, carries a motorway but also serves as an aqueduct, featuring a gallery containing five water mains lines with diameters between 1.2m and 1.5m below the road section of the tunnel.[31]
Wuhan's Yangtze River Highway and Railway Tunnel is a 2.59km two-tube double-deck tunnel under the Yangtze River completed in 2018. Each tube carries 3 lanes of local traffic on the top deck with one track Wuhan Metro Line 7 on the lower deck.[32][33][34]
Some tunnels have more than one purpose. The SMART Tunnel in Malaysia is the first multipurpose "Stormwater Management And Road Tunnel" in the world, created to convey both traffic and occasional flood waters in Kuala Lumpur. When necessary, floodwater is first diverted into a separate bypass tunnel located underneath the 2.5 mi (4.0 km) double-deck roadway tunnel. In this scenario, traffic continues normally. Only during heavy, prolonged rains when the threat of extreme flooding is high, the upper tunnel tube is closed off to vehicles and automated flood control gates are opened so that water can be diverted through both tunnels.[35]
Common utility ducts or utility tunnels carry two or more utility lines. Through co-location of different utilities in one tunnel, organizations are able to reduce the costs of building and maintaining utilities.
Over-bridges can sometimes be built by covering a road or river or railway with brick or steel arches, and then leveling the surface with earth. In railway parlance, a surface-level track which has been built or covered over is normally called a "covered way".
Snow sheds are a kind of artificial tunnel built to protect a railway from avalanches of snow. Similarly the Stanwell Park, New South Wales "steel tunnel", on the Illawarra railway line, protects the line from rockfalls.
Safety and security
Snow sheds are a kind of artificial tunnel built to protect a railway from avalanches of snow. Similarly the Stanwell Park, New South Wales "steel tunnel", on the Illawarra railway line, protects the line from rockfalls.
Owing to the enclosed space of a tunnel, fires can have very serious effects on users. The main dangers are gas and smoke production, with even low concentrations of carbon monoxide being highly toxic. Fires killed 11 people in the Gotthard tunnel fire of 2001 for example, all of the victims succumbing to smoke and gas inhalation. Over 400 passengers died in the Balvano train disaster in Italy in 1944, when the locomotive halted in a long tunnel. Carbon monoxide poisoning was the main cause of death. In the Caldecott Tunnel fire of 1982, the majority of fatalities were caused by toxic smoke, rather than by the initial crash.
Motor vehicle tunnels usually require ventilation shafts and powered fans to remove toxic exhaust gases during routine operation.[36]
Rail tunnels usually require fewer air changes per hour, but still may require forced-air ventilation. Both types of tunnels often have provisions to increase ventilation under emergency conditions, such as a fire. Although there is a risk of increasing the rate of combustion through increased airflow, the primary focus is on providing breathable air to persons trapped in the tunnel, as well as firefighters.
Aerodynamic pressure wave produced by high speed trains entering a tunnelventilation shafts and powered fans to remove toxic exhaust gases during routine operation.[36]
Rail tunnels usually require fewer air changes per hour, but still may require forced-air ventilation. Both types of tunnels often have provisions to increase ventilation under emergency conditions, such as a fire. Although there is a risk of increasing the rate of combustion through increased airflow, the primary focus is on providing breathable air to persons trapped in the tunnel, as well as firefighters.
Aerodynamic pressure wave produced by high speed trains entering a tunnel[37] reflects at its open ends and changes sign (compression wave-front changes to rarefaction wave-front and vice versa); When two wave-front of the same sign meets the train, significant and rapid air pressure[38] may cause aural discomfort[39] to passengers and crew. When high-speed trains exit tunnels, a loud "Tunnel boom" may occur, which can disturb residents near the mouth of the tunnel, and it is exacerbated in mountain valleys where the sound can echo.
When there is a parallel, separate tunnel available, airtight but unlocked emergency doors are usually provided which allow trapped personnel to escape from a smoke-filled tunnel to the parallel tube.[40]
Larger, heavily used tunnels, such as the Big Dig tunnel in Boston, Massachusetts, may have a dedicated 24-hour manned operations center which monitors and reports on traffic conditions, and responds to emergencies.[41] Video surveillance equipment is often used, and real-time pictures of traffic conditions for some highways may be viewable by the general public via the Internet.
database of seismic damage to underground structures using 217 case histories shows the following general observations can be made regarding the seismic performance of underground structures:
Earthquakes are one of nature's most formidable threats. A magnitude 6.7 earthquake shook the San Fernando valley in Los Angeles in 1994. The earthquake caused extensive damage to various structures including buildings, freeway overpasses and road systems throughout the area. The National Center for Environmental Information estimates total damages to be 40 billion dollars.[43] According to an article issued by Steve Hymon of TheSource – Transportation News and Views, there was no serious damage sustained by the LA subway system. Metro, the owner of the LA subway system, issued a statement through their engineering staff about the design and consideration that goes into a tunnel system. Engineers and architects perform extensive analysis as to how hard they expect earthquakes to hit that area. All of this goes into the overall design and flexibility of the tunnel.This same trend of limited subway damage following an earthquake can be seen in many other places. In 1985 a magnitude 8.1 earthquake shook Mexico City; there was no damage to the subway system, and in fact the subway systems served as a lifeline for emergency personnel and evacuations. A magnitude 7.2 ripped through Kobe Japan in 1995, leaving no damage to the tunnels themselves. Entry portals sustained minor damages, however these damages were attributed to inadequate earthquake design that originated from the original construction date of 1965. In 2010 a magnitude 8.8, massive by any scale, afflicted Chile. Entrance stations to subway systems suffered minor damages, and the subway system was down for the rest of the day. By the next afternoon, the subway system was operational again.[44]
Examples
This section may require cleanup to meet WThis same trend of limited subway damage following an earthquake can be seen in many other places. In 1985 a magnitude 8.1 earthquake shook Mexico City; there was no damage to the subway system, and in fact the subway systems served as a lifeline for emergency personnel and evacuations. A magnitude 7.2 ripped through Kobe Japan in 1995, leaving no damage to the tunnels themselves. Entry portals sustained minor damages, however these damages were attributed to inadequate earthquake design that originated from the original construction date of 1965. In 2010 a magnitude 8.8, massive by any scale, afflicted Chile. Entrance stations to subway systems suffered minor damages, and the subway system was down for the rest of the day. By the next afternoon, the subway system was operational again.[44]
The history of ancient tunnels and tunneling in the world is reviewed in various sources which include many examples of these structures that were built for different purposes.[45][46] Some well known ancient and modern tunnels are briefly introduced below:
- The qanat or kareez of Persia are water management systems used to provide a reliable supply of water to human settlements or for irrigation in hot, arid and semi-arid climates. The deepest known qanat is in the Iranian city of Gonabad, which after 2700 years, still provides drinking and agricultural water to nearly 40,000 people. Its main well depth is more than 360 m (1,180 ft), and its length is 45 km (28 mi).[47]
- The Siloam Tunnel was built before 701 BCE for a reliable supply of water, to withstand siege attacks.
- The Eupalinian aqueduct on the island of Samos (North Aegean, Greece) was built in 520 BCE by the ancient Greek engineer Eupalinos of Megara under a contract with the local community. Eupalinos organised the work so that the tunnel was begun from both sides of Mount Kastro. The two teams advanced simultaneously and met in the middle with excellent accuracy, something that was extremely difficult in that time. The aqueduct was of utmost defensive importance, since it ran underground, and it was not easily found by an enemy who could otherwise cut off the water supply to Pythagoreion, the ancient capital of Samos. The tunnel's existence was recorded by Herodotus (as was the mole and harbour, 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 19th century by German archaeologists. The tunnel proper is 1,030 m long (3,380 ft) and visitors can still enter it.
- One of the first known drainage and sewage networks in form of tunnels was constructed at Persepolis in Iran at the same time as the construction of its foundation in 518 BCE. In most places the network was dug in the sound rock of the mountain and then covered by large pieces of rock and stone followed by earth and piles of rubble to level the ground. During investigations and surveys, long sections of similar rock tunnels extending beneath the palace area were traced by Herzfeld and later by Schmidt and their archeological teams.[48]
- The Via Flaminia, an important Roman road, penetrated the Furlo pass in the Apennines through a tunnel which emperor Vespasian had ordered built in 76–77 CE. A modern road, the SS 3 Flaminia, still uses this tunnel, which had a precursor dating back to the 3rd century BCE; remnants of this earlier tunnel (one of the first road tunnels) are also still visible.
- The world's oldest tunnel traversing under a water body is claimed[49] to be the Terelek kaya tüneli under Kızıl River, a little south of the towns of Boyabat and Durağan in Turkey, just downstream from where Kizil River joins its tributary Gökırmak. The tunnel is presently under a narrow part of a lake formed by a dam some kilometers further downstream. Estimated to have been built more than 2000 years ago, possibly by the same civilization that also built the royal tombs in a rock face nearby, it is assumed to have had a defensive purpose.
- Sapperton Canal Tunnel on the Thames and Severn Canal in England, dug through hills, which opened in 1789, was 3.5 km (2.2 mi) long and allowed boat transport of coal and other goods. Above it the Sapperton Long Tunnel was constructed which carries the "Golden Valley" railway line between Swindon and Gloucester.
- The 1791 Dudley canal tunnel is on the Dudley Canal, in Dudley, England. The tunnel is 1.83 miles (2.9 km) long. Closed in 1962 the tunnel was reopened in 1973. The series of tunnels was extended in 1984 and 1989.[50]
- Fritchley Tunnel, constructed in 1793 in Derbyshire by the Butterley Company to transport limestone to its ironworks factory. The Butterley company engineered and built its own railway a victim of the depression the company closed after 219 years in 2009. The tunnel is the world's oldest railway tunnel traversed by rail wagons using gravity and horse haulage. The railway was converted to steam locomotion in 1813 using a Steam Horse locomotive engineered and built by the Butterley company, however reverted to horses. Steam trains used the tunnel continuously from the 1840s when the railway was converted to a narrow gauge. The line closed in 1933. In the Second World War, the tunnel was used as an air raid shelter. Sealed up in 1977 it was rediscovered in 2013 and inspected. The tunnel was resealed to preserved the construction as it was designated an ancient monument.[51][52][52]
- The 1794 Butterley canal tunnel canal tunnel is 3,083 yards (2,819m) in length on the Cromford Canal in Ripley, Derbyshire, England. The tunnel was built simultaneously with the 1773 Fritchley railway tunnel. The tunnel partially collapsed in 1900 splitting the Cromford Canal, and has not been used since. The Friends of Cromford Canal, a group of volunteers, are working at fully restoring the Cromford Canal and the Butterley Tunnel.[53]
- The 1796 Stoddart Tunnel in Chapel-en-le-Frith in Derbyshire is reputed to be the oldest rail tunnel in the world. The rail wagons were originally horse-drawn.
- Derby Tunnels in Salem, Massachusetts were built in 1801 to smuggle imports affected by President Thomas Jefferson's new customs duties. Jefferson had ordered local militias to help the Custom House in each port collect these dues, but the smugglers, led by Elias Derby, hired the Salem militia to dig the tunnels and hide the spoil. The tunnels ran 3 miles connecting the wharfs in town to an underground train station[citation needed]. Along the way they connected prominent businessmen and politicians homes to their stores, bank, and museums. Members of the Salem Commons Fund hid the tunnels behind a project to fill in the ponds and grade the local common. Tunnel dirt was hidden in those ponds and was used to fill in rivers to create new wharfs to connect the tunnels to. Many politicians were involved including a Superior Court Justice, a Secretary of the Navy, and many Senators in the Federalist Party.[citation needed]
- A tunnel was created for the first true steam locomotive, from Penydarren to Abercynon. The Penydarren locomotive was built by Richard Trevithick. The locomotive made the historic journey from Penydarren to Abercynon in 1804. Part of this tunnel can still be seen at Pentrebach, Merthyr Tydfil, Wales. This is arguably the oldest railway tunnel in the world, dedicated only to self-propelled steam engines on rails.
- The Montgomery Bell Tunnel in Tennessee, an 88
The use of tunnels for mining is called drift mining.
Military use
Some tunnels are not for transport at all but rather, are fortifications, for example Mittelwerk and Cheyenne Mountain Complex. Excavation techniques, as well as the construction of underground bunkers and other habitable areas, are often associated with military use during armed conflict, or civilian responses to threat of attack. Another use for tunnels was for the storage of chemical weapons[69][70] [2].
Secret tunnels
Door to a compartment where runaway slaves would sleep, on the Underground RailroadSecret tunnels have given entrance to or escape from an area, such as the Cu Chi Tunnels or the smuggling tunnels in the Gaza Strip which connect it to Egypt. Although the Underground Railroad network used to transport escaped slaves was "underground" mostly in the sense of secrecy, hidden tunnels were occasionally used. Secret tunnels were also used during the Cold War, under the Berlin Wall and elsewhere, to smuggle refugees, and for espionage.
Smugglers use secret tunnels to transport or store contraband, such as illegal drugs and weapons. Elaborately engineered 1,000-foot (300 m) tunnels built to smuggle drugs across the Mexico-US border were estimated to require up to 9 months to complete, and an expenditure of up to $1 million.[71] Some of these tunnels were equipped with lighting, ventilation, telephones, drainage pumps, hydraulic elevators, and in at least one instance, an electrified rail transport system.[71] Secret tunnels have also been used by thieves to break into bank vaults and retail stores after hours.[72][73] Several tunnels have been discovered by the Border Security Forces across the Line of Control along the India-Pakistan border, mainly to allow terrorists access to the Indian territory of Jammu and Kashmir.[74][75]
The actual usage of erdstall tunnels is unknown but theories connect it to a rebirth ritual.
Natural tunnels
- Lava tubes are emptied lava conduits, formed during volcanic eruptions by flowing and cooling lava.
- Natural Tunnel State Park (Virginia, US) features an 850-foot (259 m) natural tunnel, really a limestone cave, that has been used as a railroad tunnel since 1890.
- Punarjani Guha in Kerala, India. Hindus believe that crawling through the tunnel (which they believe was created by a Hindu god) from one end to the other will wash away all of one’s sins and thus allow one to attain rebirth. Only men are permitted to crawl through the tunnel.
- Torghatten, a Norwegian island with a hat-shaped silhouette, has a natural tunnel in the middle of the hat, letting light come through. The 160-metre (520 ft) long, 35-metre (115 ft) high, and 20-metre (66 ft) wide tunnel is said to be the hole made by an arrow of the angry troll Hestmannen, the hill being the hat of the troll-king of Sømna trying to save the beautiful Lekamøya. The tunnel is thought actually to be the work of ice. The sun shines through the tunnel during two few minutes long periods every year.[76]
- Small "snow tunnels", called burrows, are created by voles, chipmunks and other rodents for protection and access to food sources.
Major accidents
- Clayton Tunnel rail crash (1861) – confusion about block signals
- Welwyn Tunnel rail crash (1866) – train failed in tunnel, guard did not protect train.
- Balvano train disaster (1944)
- Caldecott Tunnel fire (1982) – major motor vehicle tunnel crash and fire.
- Channel Tunnel fire (1996)
- Mont Blanc Tunnel fire (1999)
- Princess Diana's death – Car crash in Pont D'alma tunnel, Paris, which killed Princess Diana.
See also
- Euphrates Tunnel
- Cattle creep
- Hobby tunneling
- Megaproject
- Rapid transit
- Sequential Excavation Method
- Structure gauge — measure of maximum physical clearance in a tunnel
- Tree tunnel
- Tunnels in popular culture
- Underground living
- United States Army Corps of Engineers
References
- ^ DESIGN MANUAL FOR ROADS AND BRIDGES: VOLUME 2: SECTION 2: PART 9: BD 78/99: DESIGN OF ROAD TUNNELS (PDF). The Department for Transport. 1999.
- ^ NFPA Standard for Safeguarding Construction, Alteration, and Demolition Operations. National Fire Protection Association.
- ^ Sutcliffe, Harry (2004). "Tunnel Boring Machines". In Bickel, John O.; Kuesel, Thomas R.; King, Elwyn H. (eds.). Tunnel Engineering Handbook (2nd ed.). Kluwer Academic Publishers. p. 210. ISBN 978-1-4613-8053-5.
- ^ Powers, P.J. (2007). Construction dewatering and groundwater control. Hoboken, NJ: John Wiley & Sons Inc.
- ^ a b United States Army Corps of Engineers. (1978). Tunnels and shafts in rock. Washington, DC: Department of the Army.
- ^ "Capital Projects Funds". Cord.edu. Archived from the original on 17 December 2011. Retrieved 19 April 2013.
- ^ Chan, Sewell (3 August 2005). "$100 Million for a Tunnel. What Tunnel?". The New York Times.
- ^ "Encouraging U.S. Infrastructure Investment – Council on Foreign Relations". Cfr.org. Retrieved 19 April 2013.
- ^ Ellis 2015, p. 118.
- ^ "Tunnels & Tunnelling International". Tunnelsonline.info. Archived from the original on 16 March 2012. Retrieved 19 April 2013.
- ^ "The Groene Hart Tunnel". Hslzuid.nl. Archived from the original on 25 September 2009. Retrieved 19 April 2013.
- ^ Johnson, Kirk (4 December 2012). "Engineering Projects Will Transform Seattle, All Along the Waterfront". The New York Times.
- ^ "Tunnelling". tunnellersmemorial.com. Archived from the original on 23 August 2010. Retrieved 20 June 2010.
- ^ a b c "Understanding the New Austrian Tunnel Method (NATM)". Tunnel Business Magazine. Benjamin Media. 5 December 2018. Retrieved 27 December 2018.
- ^ "Mushrooms and Tours | Li-Sun Exotic Mushrooms". www.li-sunexoticmushrooms.com.au.
- ^ BISCOE, EMMA (15 May 2014). "Mittagong mushroom business will close down". Illawarra Mercury.
- ^ "Archived copy". Archived from the original on 4 March 2016. Retrieved 2 April 2009.CS1 maint: archived copy as title (link)
- ^ "Archived copy". Archived from the original on 4 March 2016. Retrieved 2 April 2009.CS1 maint: archived copy as title (link)
- ^ The Railway Magazine August 2015, p12.
- ^ "Report on Redeveloping Railway Tunnels". www.tunnel-online.info.
- ^ "San Francisco-Oakland Bay Bridge". Bay Area Toll Authority. 4 November 2015.
- ^ "Eurasia Tunnel Project" (PDF). Unicredit – Yapı Merkezi, SK EC Joint Venture. Archived from the original (PDF) on 20 January 2016. Retrieved 13 April 2014.
- ^ "Istanbul's mega-project: World's first three-level tunnel to be built under the Bosporus – Daily Sabah". 19 February 2017. Archived from the original on 19 February 2017.
- ^ "Shanghai to Dig Double-deck Tunnel". 15 May 2006. Archived from the original on 15 May 2006.
- ^ "Maastricht's new highway tunnel: a role model for Europe". DW.COM.
- ^ Unique stacked tunnel under Maastricht (archived) – Imtech Traffic & Infra
- ^ "To Break Ground For 63rd St., East River Tunnel". New York Leader-Observer. 20 November 1969. p. 8. Retrieved 29 July 2016 – via Fultonhistory.com.
- ^ "Governor Rockefeller and Mayor Lindsay Attend 'Holing Through' of 63d St. Tunnel". The New York Times. 11 October 1972. ISSN 0362-4331. Retrieved 3 February 2018.
- ^ Lorch, Donatella (29 October 1989). "The 'Subway to Nowhere' Now Goes Somewhere". The New York Times. Retrieved 20 October 2011.
- ^ MTA East Side Access program
- ^ "Black & Veatch uses trenchless technology for water main rehabilitation in Hong Kong – WaterWorld". 5 June 2017. Archived from the original on 5 June 2017.
- ^ "新闻分析：这条隧道藏了多少科技秘密——揭秘"万里长江公铁第一隧"-新华网". www.xinhuanet.com. Retrieved 7 June 2020.
- ^ 汉网 (27 September 2018). "揭秘武汉长江公铁第一隧"尖板眼" 68个通道可供江底逃生". news.sina.com.cn. Retrieved 7 June 2020.Mittelwerk and Cheyenne Mountain Complex. Excavation techniques, as well as the construction of underground bunkers and other habitable areas, are often associated with military use during armed conflict, or civilian responses to threat of attack. Another use for tunnels was for the storage of chemical weapons[69][70] [2].
Secret tunnels
- pipeline is not a tunnel, though some recent tunnels have used immersed tube construction techniques rather than traditional tunnel boring methods.
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