Trench Less Techniques

8/6/2019 Trench Less Techniques

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Trenchless rehabilitation includes such construction methods as sliplining,thermoformedpipe,pipe bursting, shotcrete, gunite, cured-in-place pipe (CIPP), grout-in-place pipe,mechanical spot repair, and other methods for the repair, rehabilitation, or replacement ofexisting buried pipes and structures without excavation, or at least with minimal excavation.Mechanical Spot Repairis applied where damaged pipelines require the re-instatement of

structural integrity. Sliplining, CIPP, and thermoformed pipe lining involve pulling orinverting a new liner into an existing pipe, then applying heat and/or pressure to force theliner to expand to fill the pipe. CIPP technologies combine a carrier (felt or fibreglass)impregnated with heat, ultraviolet light, or ambient curable resin to form a "pipe within a

pipe". Pipe bursting fractures a pipe from the inside and forces the fragments outwards whilea new pipe is drawn in to replace the old.[2] The other methods are primarily for fixing spotleaks. Trenchless rehabilitation methods are generally more cost-effective than traditionalexhume (dig) and replace methods.

[edit] Trade AssociationsThe trenchless technology industry is represented by several industry associations in addition

to standing committees within almost every water and sewer related industry association. TheNational Association of Sewer Service Companies (NASSCO) was established in 1976 and isthe oldest such association with a trenchless focus. TheNorth American Society forTrenchless Technology(NASTT) was established in 1990. The Indian Society for TrenchlessTechnology or IndSTT is the apex organization to promote Trenchless Technology in SouthAsia. It was established in 1995 with its head office at New Delhi. TheInternational Societyfor Trenchless Technology, established in 1986, has 25 activenational trenchless technologysocietiesassociated with it. Several organizations bring out Technical Journals for sensitizingthe readers about such techniques.No Dig India is the official Journal of IndSTT.

[edit] References

Wikipedia, the free encyclopedia

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Look uptunneling in Wiktionary, the free dictionary.

Tunneling may refer to:

Digging tunnels (the literal meaning)

Quantum tunneling, the quantum-mechanical effect where a particle crosses through aclassically-forbidden potential energy barrier

Tunneling (fraud), a fraud committed by a company's own management or by majorshareholders

Tunneling protocol, transmitting one computer network protocol that is encapsulatedinside another network protocol

MicrotunnelingFrom Wikipedia, the free encyclopedia

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As the name implies, microtunneling is used to construct small tunnels. These smalldiameter tunnels make it impossible to have an operator in the machine itself. Instead, themicrotunnel boring machine or MTBM must be operated remotely. Usually the operatorcontrols the machine from a control room on the surface of the ground. The operator is givenconstant feedback about the machines location, orientation and hydraulic devices via a

computer console. Most machines also have video cameras set up to give the operator moreinformation. The operator can then control the MTBM and the jacking frame from the safetyof the control room.

In most microtunneling operations the pipe is inserted from the entry and pushed behind themachine. This is a process often calledPipe Jacking. As the machine advances, more tunnelliner is pushed from the entrance. Thus, the speed of the advancing machine is controlled bythe speed at which the pipe is inserted into the entrance.

As the length of tunnel increases, the friction of the ground around the pipe increases as well.Usually, two practices are used to minimize this friction. First, over-cutting is used to give aslight gap between the inner edge of the tunnel and the outer edge of the liner. Usually this isachieved by using a cutter wheel with a diameter inch (12mm) to 4 inches (100mm) largerthan the outside diameter of the liner. Secondly, an economical and ecologically friendlylubricant, oftenbentoniteslurry, is injected into this gap. In addition to lubrication, the

pressure of the lubricant prevents the gap from collapsing.

While friction can be reduced, it can never be eliminated, and so hundreds of tons of force arerequired to push the machine and liner into the ground. A large jacking frame is required to

produce these forces. In most cases the entrance must be modified to support this frame andthe forces it generates.

In addition to the jacking frame, smaller jacks, called interjacks, may be inserted betweensections of tunnel liner. These push the two sections of liner apart. Friction on the linersections between the interjack and the tunnel entrance helps to prevent the liner from sliding

out backwards. So while the liner behind the interjack does not move, those sections in frontof it receive additional pushing force.

Microtunnel boring machineMicrotunnel Boring Machines (MTBM) are used formicrotunneling. They are verysimilar to tunnel boring machines(TBM)but on a smaller scale. These machines generallyvary from 0.61 to 1.5 meters (2 ft 0.02in to 4 ft 11 in) but smaller and larger machines haveexisted. The main differences between MTBM and TBM operations are:

MTBM is operated by remote control.

MTBM usually has the tunnel liner pushed behind the machine instead of built as the

machine advances.

Directional drillingDirectional drilling (or slant drilling) is the practice of drilling non-vertical

wells. It can be broken down into three main groups: Oilfield Directional Drilling,
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Utility Installation Directional Drilling (or H.D.D. or Horizontal Directional Drilling)Directional boring, and in-seam directional drilling (Coal-Bed methane

A horizontal directionaldrill in operation

[edit] HistoryMany prerequisites enabled this suite of technologies to become productive. Probably thefirst requirement was the realization that oil wells (or water wells, but since they areshallower, most development was in the oil industry) are not necessarily vertical. Thisrealization was quite slow, and did not really grasp the attention of the oil industry until thelate 1920s when there were several lawsuits alleging that wells drilled from a rig on one

property had crossed the boundary and were penetrating a reservoir on an adjacent property.Initially, proxy evidence such as production changes in pre-existing wells was accepted, butsuch cases fueled the development of small diameter tools capable of surveying wells duringdrilling.

Measuring the inclination of a wellbore (its deviation from the vertical) is comparativelysimple, requiring only a pendulum. Measuring the azimuth (direction with respect to thegeographic grid in which the wellbore is running from the vertical), however, was moredifficult. In certain circumstances, magnetic fields could be used, but could be influenced bymetalwork used inside wellbores, as well as the metalwork used in drilling equipment. Thenext advance was in the modification of small gyroscopic compasses by theSperryCorporation, who were making similar compasses for aeronautical navigation. Sperry did thisunder contract to Sun Oil(who were involved in a lawsuit as described above), and a spin-offcompany "Sperry Sun" was formed, which brand continues to this day, absorbed intoHalliburton. Three components are measured at any given point in a wellbore in order todetermine its position: the depth of the point (measured depth), the inclination at the point,

and the magnetic azimuth at the point. These 3 components combined are referred to as a"survey". A series of consecutive surveys are needed to track the progress and location of awellbore. Many of the earliest innovations such as photographic single shot technology andcrow's feet baffle plates for landing survey tools were developed by Robert Richardson, anindependent directional driller who first drilled in the 1940s and was still working in 2008 .[1]

Prior experience with rotary drilling had established several principles for the configurationof drilling equipment down hole ("Bottom Hole Assembly" or "BHA") that would be proneto "drilling crooked hole" (initial accidental deviations from the vertical would be increased).Counter-experience had also given early directional drillers ("DD's") principles of BHAdesign and drilling practice which would help bring a crooked hole nearer the vertical.

In 1934, John Eastman of California became a pioneer in directional drilling. (E&P, "Makinga hole was hard work",Kris Wells, AOGHS Contributing Editor, Nov. 1, 2006). In aMay,1934 Popular Science Monthly article, it was stated that " Only a handfull of men in the
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world have the strange power to make a bit rotating a mile below ground at the end of a steeldrill pipe, snake its way in a curve or aroung a dog leg angle, to reach a desired object." By1973, the two companies had merged to become Eastman Whipstock, Inc., the worlds largestdirectional company. (Making a hole was hard work, supra).

Combined, these survey tools and BHA designs made directional drilling possible, but it was

perceived as arcane. The next major advance was in the 1970s, when downholedrillingmotors (aka mud motors, driven by the hydraulic power of drilling mud circulated down thedrill string) became common. These allowed the bit to be rotated on the bottom of the hole,while most of the drill pipe was held stationary. Including a piece of bent pipe (a "bent sub")

between the stationary drill pipe and the top of the motor allowed the direction of thewellbore to be changed without needing to pull all the drill pipe out and place anotherwhipstock. Coupled with the development ofMeasurement While Drilling tools (using mud

pulse telemetry orEM telemetry, which allows tools down hole to send directional data backto the surface without disturbing drilling operations), directional drilling became easier.Certain profiles could not be drilled without the drill string rotating at all times.

[edit] BenefitsDirectional wells are drilled for several purposes:

Increasing the exposed section length through the reservoir by drilling through thereservoir at an angle

Drilling into the reservoir where vertical access is difficult or not possible. Forinstance an oilfield under a town, under a lake, or underneath a difficult to drillformation

Allowing more wellheads to be grouped together on one surface location can allowfewer rig moves, less surface area disturbance, and make it easier and cheaper tocomplete and produce the wells. For instance, on an oil platformor jacket offshore, up

to about 40 wells can be grouped together. The wells will fan out from the platforminto the reservoir below. This concept is being applied to land wells, allowingmultiple subsurface locations to be reached from one pad, reducing costs.

Drilling a "relief well" to relieve the pressure of a well producing without restraint (a"blow out"). In this scenario, another well could be drilled starting at a safe distanceaway from the blow out, but intersecting the troubled wellbore. Then, heavy fluid (killfluid) is pumped into the relief wellbore to suppress the high pressure in the originalwellbore causing the blowout.

Most directional drillers are given a well path to follow that is predetermined by engineersand geologists before the drilling commences. When the directional driller starts the drilling

process, periodic surveys are taken with a downhole instrument to provide survey data(inclination and azimuth) of the well bore. [2] These pictures are typically taken at intervals

between 30500 feet, with 90 feet common during active changes of angle or direction, anddistances of 200300 feet being typical while "drilling ahead" (not making active changes toangle and direction). During critical angle and direction changes, especially while using adownhole motor, an MWD (Measurement while drilling) tool will be added to thedrill stringto provide continuously updated measurements that may be used for (near) real-timeadjustments.

These data indicate if the well is following the planned path and whether the orientation ofthe drilling assembly is causing the well to deviate as planned. Corrections are regularlymade by techniques as simple as adjusting rotation speed or the drill string weight (weight on

bottom) and stiffness, as well as more complicated and time consuming methods, such asintroducing a downhole motor. Such pictures, or surveys, are plotted and maintained as an
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engineering and legal record describing the path of the well bore. The survey pictures takenwhile drilling are typically confirmed by a later survey in full of the borehole, typically usinga "multi-shot camera" device.

The multi-shot camera advances the film at time intervals so that by sealing the camerainstrument into a tubular housing and dropping the assembly into the drilling string (down to

just above the drilling bit), and then withdrawing the drill string at time intervals, the wellmay be fully surveyed at regular intervals (approximately every 90 feet being common, thetypical length of 2 or 3 joints of drill pipe, known as a stand, since most drilling rigs "stand

back" the pipe withdrawn from the hole at such increments, known as "stands".)

Drilling far from the surface location still requires careful planning and design. The currentrecord holders manage wells over 10 km (6 miles) away from the surface location at a depthof only 1,6002,600 m (5,2008,500 ft).[3]

[edit] DisadvantagesUntil the arrival of modern downhole motors and better tools to measure inclination and

azimuth of the hole, directional drilling and horizontal drilling was much slower than verticaldrilling due to the need to stop regularly and take time consuming surveys, and due to slowerprogress in drilling itself (lower rate of penetration). These disadvantages have shrunk overtime as downhole motors became more efficient and semi-continuous surveying became

possible.

What remains is a difference in operating costs: for wells with an inclination of less than 40degrees, tools to carry out adjustments or repair work can be lowered by gravity on cable intothe hole. For higher inclinations, more expensive equipment has to be mobilized to push toolsdown the hole.

Another disadvantage of wells with a high inclination was that prevention of sand influx intothe well was less reliable and needed higher effort. Again, this disadvantage has diminished

such that, provided sand control is adequately planned, it is possible to carry it out reliably.

[edit] Stealing oil

In 1990, Iraq accused Kuwait of stealing Iraq's oil through slant drilling. [citation needed] TheUnited Nations redrew the border after the 1991 Gulf war that liberated Kuwait from a seven-month Iraqi occupation under former leader Saddam Hussein. It placed 11 oil wells, somefarms and an old naval base that used to be in Iraq on the Kuwaiti side.[4]

In the mid-twentieth century, a slant-drilling scandal occurred in the hugeEast Texas OilField.[5]

Top of Form

Special:Search

Tunnel
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Underground tunnel for heatpipes between Rigshospitalet and Amagervrket in Denmark.

Underground railway tunnel on the Taipei Metro in Taiwan.

Coal tunnel under construction using handset aluminum concrete forms.
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A tunnel is an underground passageway, completely enclosed except for openings for egress,commonly at each end.

A tunnel may be for foot or vehicular road traffic, forrailtraffic, or for a canal. Some tunnelsare aqueducts to supply water for consumption or forhydroelectric stations or are sewers.Other uses include routing power or telecommunication cables, some are to permit wildlife

such as European badgersto cross highways. Secret tunnels have given entrance to or escapefrom an area, such as the Cu Chi Tunnelsor the smuggling tunnels in the Gaza Stripwhichconnect it to Egypt. Some tunnels are not for transport at all but rather, are fortifications, forexample Mittelwerkand Cheyenne Mountain.

In the United Kingdom, a pedestrian tunnel or other underpass beneath a road is called aunderpass subway. In the United States that term now means an undergroundrapid transitsystem.

The central part of a rapid transit network is usually built in tunnels. Rail station platformsmay be connected by pedestrian tunnels or by footbridges.

Contents[hide]

1 Usage limitations

2 Geotechnical investigation

3 Construction

3.1 Cut-and-cover

3.2 Clay-kicking

3.3 Boring machines

3.4 Shafts

3.5 Other key factors

3.6 Sprayed concrete techniques

3.7 Pipe jacking

3.8 Box jacking

3.9 Underwater tunnels

3.10 Other

3.11 Costs and cost overruns of tunnels

3.12 Choice of tunnels vs. bridges

4 Variant tunnel types

4.1 Double-deck tunnel

4.2 Artificial tunnels

4.3 Hazards

5 Examples of tunnels

5.1 In history

5.2 Longest

5.3 Notable
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5.4 Other uses

6 Natural tunnels

7 Temporary way

8 Enlargement

9 Floor Lowering

10 Accidents

11 See also

12 Notes

13 Bibliography

14 Further reading

15 External links

[edit] Usage limitationsA tunnel is relatively long and narrow; in general the length is more (usually much more)than twice the diameter. Some hold a tunnel to be at least 0.160kilometres(0.10 mi) long andcall shorter passageways by such terms as an "underpass" or a "chute". For example, theunderpass beneath Yahata Stationin Kitakyushu, Japanis 0.130 km long (0.081 mi) and somight not be considered a tunnel.

[edit] Geotechnical investigationMain article: Geotechnical investigation

A tunnel project must start with a comprehensive investigation of ground conditions by

collecting samples from boreholes and by other geophysical techniques. An informed choicecan then be made of machinery and methods for excavation and ground support, which willreduce the risk of encountering unforeseen ground conditions. In planning the route thehorizontal and vertical alignments will make use of the best ground and water conditions.

In some cases conventional desk and site studies yield insufficient information to assess suchfactors as the blocky nature of rocks, the exact location of fault zones, or the stand-up timesof softer ground. This may be a particular concern in large diameter tunnels. To give moreinformation a pilot tunnel, or drift, may be driven ahead of the main drive. This smallerdiameter tunnel will be easier to support should unexpected conditions be met, and will beincorporated in the final tunnel. Alternatively, horizontal boreholes may sometimes be drilledahead of the advancing tunnel face.

[edit] Construction
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Cut-and-cover constructions of the Paris Mtroin France

Tunnels are dug in types of materials varying from soft clay to hard rock. The method oftunnel construction depends on such factors as the ground conditions, the ground waterconditions, the length and diameter of the tunnel drive, the depth of the tunnel, the logistics ofsupporting the tunnel excavation, the final use and shape of the tunnel and appropriate riskmanagement.

There are three basic types of tunnel construction in common use:

Cut and cover tunnels, constructed in a shallow trench and then covered over.

Bored tunnels, constructed in situ, without removing the ground above. They areusually of circular or horseshoe cross-section.

Immersed tube tunnels, sunk into a body of water and sit on, or are buried just under,its bed.

[edit] Cut-and-cover

Cut-and-cover is a simple method of construction for shallow tunnels where a trench isexcavated and roofed over with an overhead support system strong enough to carry the loadof what is to be built above the tunnel. Two basic forms of cut-and-cover tunnelling areavailable:

Bottom-up method: A trench is excavated, with ground support as necessary, and thetunnel is constructed in it. The tunnel may be of in situ concrete, precast concrete,

precast arches,or corrugated steel arches; in early days brickwork was used. Thetrench is then carefully back-filled and the surface is reinstated.

Top-down method: Here side support walls and capping beams are constructed fromground level by such methods as slurry walling, or contiguous bored piling. Then a

shallow excavation allows making the tunnel roof of precast beams or in situ concrete.The surface is then reinstated except for access openings. This allows earlyreinstatement of roadways, services and other surface features. Excavation then takes

place under the permanent tunnel roof, and the base slab is constructed.

Shallow tunnels are often of the cut-and-cover type (if under water, of the immersed-tubetype), while deep tunnels are excavated, often using a tunnelling shield. For intermediatelevels, both methods are possible.

Large cut-and-cover boxes are often used for underground metro stations, such as CanaryWharf tube stationin London. This construction form generally has two levels, which allowseconomical arrangements for ticket hall, station platforms, passenger access and emergency

egress, ventilation and smoke control, staff rooms, and equipment rooms. The interior ofCanary Wharf station has been likened to an underground cathedral, owing to the sheer sizeof the excavation. This contrasts with most traditional stations on London Underground,where bored tunnels were used for stations and passenger access.

[edit] Clay-kicking

Clay-kicking is a specialised method developed in the United Kingdom, of manually diggingtunnels in strong clay-based soil structures. Unlike previous manual methods of usingmattocks which relied on the soil structure to be hard, clay-kicking was relatively silent andhence did not harm soft clay based structures.

The clay-kicker lies on a plank at a 45-degree angle away from the working face, and inserts

a tool with a cup-like rounded end with his feet. Turning the tool with his hands, he extracts asection of soil, which is then placed on the waste extract.
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Regularly used in Victorian civil engineering, the methods found favour in the renewal of theUnited Kingdom's then ancient sewerage systems, by not having to remove all property orinfrastructure to create an effective small tunnel system. During the First World War, thesystem was successfully deployed by the Royal Engineer tunnelling companiesto deploylarge military mines beneath enemy German Empire lines. The method was virtually silent

not susceptible to listening methods of detection.[1]

[edit] Boring machines

Main article: Tunnel boring machine

A tunnel boring machine that was used at Yucca Mountain,Nevada, United States

Tunnel boring machines (TBMs) and associated back-up systems are used to highly automatethe entire tunneling process, reducing tunneling costs.

Tunnel boring in certain predominantly urban applications, is viewed as quick and costeffective alternative to laying surface rails and roads. Expensive compulsory purchase of

buildings and land with potentially lengthy planning inquiries is eliminated.

There are a variety of TBMs that can operate in a variety of conditions, from hard rock to softwater-bearing ground. Some types of TBMs, bentonite slurry and earth-pressure balancemachines, have pressurised compartments at the front end, allowing them to be used indifficult conditions below the water table. This pressurizes the ground ahead of the TBMcutter head to balance the water pressure. The operators work in normal air pressure behindthe pressurised compartment, but may occasionally have to enter that compartment to renewor repair the cutters. This requires special precautions, such as local ground treatment orhalting the TBM at a position free from water. Despite these difficulties, TBMs are now

preferred to the older method of tunneling in compressed air, with an air lock/decompressionchamber some way back from the TBM, which required operators to work in high pressureand go through decompression procedures at the end of their shifts, much like divers.

In February 2010, Aker Wirth delivered a TBM to Switzerland, for the expansion of LinthLimmern Power Plant in Switzerland. The borehole has a diameter of 8.03 metres (26.3 ft). [2]

The TBM used for digging the 57-kilometre (35 mi)Gotthard Base Tunnel, in Switzerland,has a diameter of about 9 metres (30 ft). A larger TBM was built to bore the Green HeartTunnel (Dutch: Tunnel Groene Hart) as part of theHSL-Zuid in the Netherlands, with adiameter of 14.87 metres (48.8 ft).[3] This in turn was superseded by the Madrid M30ringroad, Spain, and the Chong Ming tunnels in Shanghai, China. All of these machines were

built at least partly by Herrenknecht.

[edit] Shafts

A shaft is sometimes necessary for a tunnel project. They are usually circular and go straight

down until they reach the level at which the tunnel is going to be built. A shaft normally hasconcrete walls and is built to be permanent. Once they are built, Tunnel Boring Machines are
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lowered to the bottom and excavation can start. Shafts are the main entrance in and out of thetunnel until the project is completed. Sometimes if a tunnel is going to be long, multipleshafts at various locations will be bored so that entrance into the tunnel is closer to theunexcavated area.[4]

[edit] Other key factors

Stand-up time is the amount of time a tunnel will support itself without any addedstructures. Knowing this time allows the engineers to determine how much can beexcavated before support is needed. The longer the stand-up time is the faster theexcavating will go. Generally certain configurations of rock and clay will have thegreatest stand-up time, and sand and fine soils will have a much lower stand-up time.[5]

Groundwater control is very important in tunnel construction. If there is water leakinginto the tunnel stand-up time will be greatly decreased. If there is water leaking intothe shaft it will become unstable and will not be safe to work in. To stop this fromhappening there are a few common methods. One of the most effective is ground

freezing. To do this pipes are inserted into the ground surrounding the shaft and arecooled until they freeze. This freezes the ground around each pipe until the wholeshaft is surrounded frozen soil, keeping water out. The most common method is toinstall pipes into the ground and to simply pump the water out. This works for tunnelsand shafts.[6]

Tunnel shape is very important in determining stand-up time. The force from gravityis straight down on a tunnel, so if the tunnel is wider than it is high it will have aharder time supporting itself decreasing its stand-up time. If a tunnel is higher than itis wide the stand up time will increase making the project easier. The hardest shape tosupport itself is a square or rectangular tunnel. The forces have a harder time beingredirected around the tunnel making it extremely hard to support itself. This of course

all depends what the material of the ground is.[4]

[edit] Sprayed concrete techniques

The New Austrian Tunneling Method (NATM) was developed in the 1960s, and is the bestknown of a number of engineering solutions that use calculated and empirical real-timemeasurements to provide optimised safe support to the tunnel lining. The main idea of thismethod is to use the geological stress of the surrounding rockmass to stabilize the tunnelitself, by allowing a measured relaxation and stress reassignment into the surrounding rock to

prevent full loads becoming imposed on the introduced support measures. Based ongeotechnical measurements, an optimal cross section is computed. The excavation isimmediately protected by a layer of sprayed concrete, commonly referred to asshotcrete,

after excavation. Other support measures could include steel arches, rockbolts and mesh.Technological developments in sprayed concrete technology have resulted in steel andpolypropylene fibres being added to the concrete mix to improve lining strength. This createsa natural load-bearing ring, which minimizes the rock's deformation.
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Illowra Battery utility tunnel, Port Kembla. One of manybunkers south of Sydney.

By special monitoring the NATM method is very flexible, even at surprising changes of thegeomechanical rock consistency during the tunneling work. The measured rock propertieslead to appropriate toolsfor tunnel strengthening. In the last decades also soft groundexcavations up to 10 kilometres (6.2 mi) became usual.

[edit] Pipe jacking

Main article:Pipe jacking

Pipe Jacking, also known as pipejacking orpipe-jacking (orpipe ramming in USEnglish), is a method of tunnel construction where hydraulic jacks are used to push speciallymade pipes through the ground behind a tunnel boring machine or shield. This technique iscommonly used to create tunnels under existing structures, such as roads or railways. Tunnelsconstructed by pipe jacking are normally small diameter tunnels with a maximum size ofaround 2.4m.

[edit] Box jacking

Box jacking is similar to pipe jacking, but instead of jacking tubes, a box shaped tunnel isused. Jacked boxes can be a much larger span than a pipe jack with the span of some box

jacks in excess of 20m. A cutting head is normally used at the front of the box being jackedand excavation is normally by excavator from within the box.

[edit] Underwater tunnels

Main article: Undersea tunnel

There are also several approaches to underwater tunnels, the two most common being boredtunnels orimmersed tubes.Submerged floating tunnels are another approach that has not

been constructed.

[edit] OtherOther tunneling methods include:

Drilling and blasting

Hydraulic splitter

Slurry-shield machine

Wall-cover construction method.

[edit] Costs and cost overruns of tunnels

Tunnels are costly and generally more costly than bridges. Large cost overruns are commonin tunnel construction. Costs and cost overruns are documented in[7] and [8]

[edit] Choice of tunnels vs. bridges

For water crossings, a tunnel is generally more costly to construct than a bridge. Navigationalconsiderations may limit the use of high bridges ordrawbridge spans intersecting withshipping channels, necessitating a tunnel.

Bridges usually require a larger footprint on each shore than tunnels. There are actually morecodes to follow with bridges than with tunnels. In areas with expensive real estate, such asManhattanand urban Hong Kong, this is a strong factor in tunnels' favor. Boston's Big Dig

project replaced elevated roadways with a tunnel system to increase traffic capacity, hidetraffic, reclaim land, redecorate, and reunite the city with the waterfront.

The 1934 Queensway Road Tunnel under the River Mersey at Liverpool, was chosen over amassively high bridge for defence reasons. It was feared aircraft could destroy a bridge in
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times of war. Maintenance costs of a massive bridge to allow the world's largest shipsnavigate under was considered higher than a tunnel. Similar conclusions were met for the1971 Kingsway Tunnel under the River Mersey.

The QueensMidtown Tunnel inNew York City serves as an example of a water-crossingtunnel built instead of a bridge.

Examples of water-crossing tunnels built instead of bridges include the Holland Tunnel andLincoln TunnelbetweenNew Jersey and Manhattan inNew York City, theQueens-MidtownTunnel between Manhattan and theboroughofQueenson Long Island, and the ElizabethRivertunnels betweenNorfolkand Portsmouth, Virginia, the 1934 River MerseyroadQueensway Tunnel and the Western Scheldt Tunnel, Zeeland, Netherlands.

Other reasons for choosing a tunnel instead of a bridge include avoiding difficulties withtides, weather and shipping during construction (as in the 51.5-kilometre or 32.0 miChannelTunnel), aesthetic reasons (preserving the above-ground view, landscape, and scenery), andalso for weight capacity reasons (it may be more feasible to build a tunnel than a sufficientlystrong bridge).

Some water crossings are a mixture of bridges and tunnels, such as the Denmark to Swedenlinkand the Chesapeake Bay Bridge-Tunnel in the eastern United States.

There are particular hazards with tunnels, especially from vehicle fires when combustiongases 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 trainstalling in the Armi tunnel in Italy in 1944, killing 426 passengers.

[edit] Variant tunnel types

[edit] Double-deck tunnel

Some tunnels are double-deck, for example the two major segments of theSan Francisco Oakland Bay Bridge (completed in 1936) are linked by a double-deck tunnel, the largest

diameter bore tunnel in the world.[9] At construction this was a combination bidirectional railand truck pathway on the lower deck with automobiles above, now converted to one-wayroad vehicle traffic on each deck.

The Lion Rock Tunnel, built in the mid-1960s connectingNew Kowloon and Sha Tin withinthe territory of Hong Kong, carries a motorway and an aqueduct.

A recent double-decker tunnel with both decks for motor vehicles is the Fuxing Road Tunnelin Shanghai, China. Cars travel on the two-lane upper deck and heavier vehicles on thesingle-lane lower.

Multipurpose tunnel are tunnels that have more than one purpose. The SMART TunnelinMalaysia is the first multipurpose tunnel in the world, as it is used both to control traffic and

flood in Kuala Lumpur.
http://en.wikipedia.org/wiki/Queens%E2%80%93Midtown_Tunnelhttp://en.wikipedia.org/wiki/New_York_Cityhttp://en.wikipedia.org/wiki/Holland_Tunnelhttp://en.wikipedia.org/wiki/Lincoln_Tunnelhttp://en.wikipedia.org/wiki/Lincoln_Tunnelhttp://en.wikipedia.org/wiki/New_Jerseyhttp://en.wikipedia.org/wiki/New_York_Cityhttp://en.wikipedia.org/wiki/Queens-Midtown_Tunnelhttp://en.wikipedia.org/wiki/Queens-Midtown_Tunnelhttp://en.wikipedia.org/wiki/Queens-Midtown_Tunnelhttp://en.wikipedia.org/wiki/Borough_(New_York_City)http://en.wikipedia.org/wiki/Borough_(New_York_City)http://en.wikipedia.org/wiki/Queenshttp://en.wikipedia.org/wiki/Queenshttp://en.wikipedia.org/wiki/Long_Islandhttp://en.wikipedia.org/wiki/Elizabeth_River_(Virginia)http://en.wikipedia.org/wiki/Elizabeth_River_(Virginia)http://en.wikipedia.org/wiki/Norfolk,_Virginiahttp://en.wikipedia.org/wiki/Norfolk,_Virginiahttp://en.wikipedia.org/wiki/Portsmouth,_Virginiahttp://en.wikipedia.org/wiki/River_Merseyhttp://en.wikipedia.org/wiki/River_Merseyhttp://en.wikipedia.org/wiki/Queensway_Tunnelhttp://en.wikipedia.org/wiki/Western_Scheldt_Tunnelhttp://en.wikipedia.org/wiki/Channel_Tunnelhttp://en.wikipedia.org/wiki/Channel_Tunnelhttp://en.wikipedia.org/wiki/Channel_Tunnelhttp://en.wikipedia.org/wiki/Oresund_Bridgehttp://en.wikipedia.org/wiki/Oresund_Bridgehttp://en.wikipedia.org/wiki/Chesapeake_Bay_Bridge-Tunnelhttp://en.wikipedia.org/wiki/United_Stateshttp://en.wikipedia.org/wiki/United_Stateshttp://en.wikipedia.org/wiki/Switzerlandhttp://en.wikipedia.org/wiki/Balvano_train_disasterhttp://en.wikipedia.org/wiki/Italyhttp://en.wikipedia.org/w/index.php?title=Tunnel&action=edit&section=16http://en.wikipedia.org/w/index.php?title=Tunnel&action=edit&section=17http://en.wikipedia.org/wiki/San_Francisco_%E2%80%93_Oakland_Bay_Bridgehttp://en.wikipedia.org/wiki/San_Francisco_%E2%80%93_Oakland_Bay_Bridgehttp://en.wikipedia.org/wiki/San_Francisco_%E2%80%93_Oakland_Bay_Bridgehttp://en.wikipedia.org/wiki/Lion_Rock_Tunnelhttp://en.wikipedia.org/wiki/New_Kowloonhttp://en.wikipedia.org/wiki/New_Kowloonhttp://en.wikipedia.org/wiki/Sha_Tin_New_Townhttp://en.wikipedia.org/wiki/Shanghaihttp://en.wikipedia.org/wiki/SMART_Tunnelhttp://en.wikipedia.org/wiki/SMART_Tunnelhttp://en.wikipedia.org/wiki/Malaysiahttp://en.wikipedia.org/wiki/Floodhttp://en.wikipedia.org/wiki/Kuala_Lumpurhttp://en.wikipedia.org/wiki/File:Midtown_Tunnel.JPGhttp://en.wikipedia.org/wiki/File:Midtown_Tunnel.JPGhttp://en.wikipedia.org/wiki/Queens%E2%80%93Midtown_Tunnelhttp://en.wikipedia.org/wiki/New_York_Cityhttp://en.wikipedia.org/wiki/Holland_Tunnelhttp://en.wikipedia.org/wiki/Lincoln_Tunnelhttp://en.wikipedia.org/wiki/New_Jerseyhttp://en.wikipedia.org/wiki/New_York_Cityhttp://en.wikipedia.org/wiki/Queens-Midtown_Tunnelhttp://en.wikipedia.org/wiki/Queens-Midtown_Tunnelhttp://en.wikipedia.org/wiki/Borough_(New_York_City)http://en.wikipedia.org/wiki/Queenshttp://en.wikipedia.org/wiki/Long_Islandhttp://en.wikipedia.org/wiki/Elizabeth_River_(Virginia)http://en.wikipedia.org/wiki/Elizabeth_River_(Virginia)http://en.wikipedia.org/wiki/Norfolk,_Virginiahttp://en.wikipedia.org/wiki/Portsmouth,_Virginiahttp://en.wikipedia.org/wiki/River_Merseyhttp://en.wikipedia.org/wiki/Queensway_Tunnelhttp://en.wikipedia.org/wiki/Western_Scheldt_Tunnelhttp://en.wikipedia.org/wiki/Channel_Tunnelhttp://en.wikipedia.org/wiki/Channel_Tunnelhttp://en.wikipedia.org/wiki/Oresund_Bridgehttp://en.wikipedia.org/wiki/Oresund_Bridgehttp://en.wikipedia.org/wiki/Chesapeake_Bay_Bridge-Tunnelhttp://en.wikipedia.org/wiki/United_Stateshttp://en.wikipedia.org/wiki/Switzerlandhttp://en.wikipedia.org/wiki/Balvano_train_disasterhttp://en.wikipedia.org/wiki/Italyhttp://en.wikipedia.org/w/index.php?title=Tunnel&action=edit&section=16http://en.wikipedia.org/w/index.php?title=Tunnel&action=edit&section=17http://en.wikipedia.org/wiki/San_Francisco_%E2%80%93_Oakland_Bay_Bridgehttp://en.wikipedia.org/wiki/San_Francisco_%E2%80%93_Oakland_Bay_Bridgehttp://en.wikipedia.org/wiki/Lion_Rock_Tunnelhttp://en.wikipedia.org/wiki/New_Kowloonhttp://en.wikipedia.org/wiki/Sha_Tin_New_Townhttp://en.wikipedia.org/wiki/Shanghaihttp://en.wikipedia.org/wiki/SMART_Tunnelhttp://en.wikipedia.org/wiki/Malaysiahttp://en.wikipedia.org/wiki/Floodhttp://en.wikipedia.org/wiki/Kuala_Lumpur


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[edit] Artificial tunnels

The 19th century Dark Gate in Esztergom,Hungary.

Overbridges can sometimes be built by covering a road or river or railway with brick or stillarches, and then levelling the surface with earth. In railway parlance, a surface-level trackwhich 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 Walessteel tunnel, on the South Coast railway line,

protects the line from rockfalls.

Common utility ducts are man-made tunnels created to carry two or more utility linesunderground. Through co-location of different utilities in one tunnel, organizations are able toreduce the costs of building and maintaining utilities.

[edit] Hazards

It has been suggested thatTunnel fire be merged into this article or section.(Discuss)Proposed since September 2010.

Owing to the enclosed space of a tunnel, fires can have very serious effects on users. Themain dangers are gas and smoke production, with low concentrations ofcarbon monoxide

being highly toxic. Fires killed 11 people in theGotthard tunnel fire of 2001 for example, all

of the victims succumbing to smoke and gas inhalation. Over 400 passengers died in theBalvano train disasterin Italy in 1944, when the locomotive halted in a long tunnel. Carbonmonoxide poisoning was the main cause of the horrifying death rate.

[edit] Examples of tunnels

[edit] In history
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A short section remains of the 1836 Edge Hill to Lime Street tunnel inLiverpool. This is theoldest used rail tunnel in the world. A tilting train passes through the tunnel.

Lehigh Tunnel, Pennsylvania

The World's oldest underwater tunnel is rumored to be the Terelek kaya tneli underKzl River, a little south of the towns ofBoyabatand Duragan in Turkey. Estimated

to have been built more than 2000 years ago (possibly 5000), it is assumed to havehad a defence purpose.

The qanat orkareez ofPersiais a water management system used to provide a reliablesupply of water to human settlements or for irrigation in hot, arid and semi-aridclimates. The oldest and largest known qanat is in the Iranian city ofGonabad, whichafter 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).

The Eupalinian aqueduct on the island ofSamos(North Aegean, Greece). Built in 520BC by the ancient Greek engineerEupalinos ofMegara. Eupalinos organised thework 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, somethingthat was extremely difficult in that time. The aqueduct was of utmost defensiveimportance, since it ran underground, and it was not easily found by an enemy whocould otherwise cut off the water supply toPythagoreion, the ancient capital ofSamos. The tunnel's existence was recorded by Herodotus (as was the mole andharbour, and the third wonder of the island, the great temple to Hera, thought by manyto 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 1,030m long (3,380 ft) and visitors can still enter it Eupalinos tunnel.

The Via Flaminia, an important Roman road, penetrated the Furlopass in theApenninesthrough a tunnel which emperorVespasian had ordered built in 76-77. Amodern road, the SS 3 Flaminia, still uses this tunnel, which had a precursor dating
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back to the 3rd century BC; remnants of this earlier tunnel (one of the first roadtunnels) are also still visible.

Sapperton Canal Tunnel on the Thames and Severn Canal in England, dug throughhills, which opened in 1789, was 3.5 km (2.2 mi) long and allowedboat transport ofcoal and other goods. Above it runs the Sapperton Long Tunnel which carries the

"Golden Valley" railway line between Swindon and Gloucester.

The 1796 Stoddart Tunnel in Chapel-en-le-Frith in Derbyshire is reputed to be theoldest rail tunnel in the world. Rail wagons were horse-drawn.

The tunnel was created for the first true steam locomotive, from Penydarren toAbercynon. The Penydarren locomotive was built by Richard Trevithick. Thelocomotive made the historic journey fromPenydarrentoAbercynon in 1804. Part ofthis tunnel can still be seen at Pentrebach,Merthyr Tydfil, Wales. This is arguably theoldest railway tunnel in the world, for self-propelled steam engines on rails.

The Montgomery Bell Tunnelin Tennessee, a 88 m (289 ft), high water diversiontunnel, 4.50--2.45 m high (15--8.0 ft), to power a water wheel, was built by slave

labour in 1819, being the first full-scale tunnel in North America.

Crown Street Station, Liverpool, 1829. Built by George Stephenson, a single tracktunnel 291 yd long (266 m) was bored from Edge Hill to Crown Street to serve theworld's first passenger railway station. The station was abandoned in 1836 being toofar from Liverpool city centre, with the area converted for freight use. Closed down in1972, the tunnel is disused. However it is the oldest rail tunnel running under streetsin the world. [1]

The 1.26 mile (2.03 km) 1829Wapping Tunnel in Liverpool, England, was the firstrail tunnel bored under a metropolis. Currently disused since 1972. Having two tracks,the tunnel runs from Edge Hill in the east of the city to the south end Liverpool docks

being used only for freight. The tunnel is still in excellent condition and is beingconsidered for reuse by Merseyrail rapid transit rail system, with maybe anunderground station cut into the tunnel. The river portal is opposite the new LiverpoolArena being ideal for a serving station. If reused it will be the oldest usedunderground rail tunnel in the world and oldest part of any underground metrosystem.

1836, Lime St Station tunnel, Liverpool. A two track rail tunnel, 1.13 miles (1,811 m)long was bored under a metropolis from Edge Hill in the east of the city to LimeStreet. In the 1880s the tunnel was converted to a deep cutting four tracks wide. Theonly occurrence of a tunnel being removed. A very short section of the original tunnelstill exists at Edge Hill station making this the oldest rail tunnel in the world still in

use, and the oldest in use under a street, albeit only one street and one building. 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 km (1.8 mi).

The 0.75 mile long 1842 Prince of Wales Tunnel, in Shildon near Darlington,England, is the oldest sizable tunnel in the world still in use under a settlement.

The Thames Tunnel, built by Marc Isambard Bruneland his son Isambard KingdomBrunel and opened in 1843, was the first underwater tunnel and the first to use atunnelling shield. Originally used as a foot-tunnel, it was a part of the East LondonLine of the London Underground until 2007, being the oldest section of the system.From 2010 the tunnel becomes a part of the London Overground system.

The 2.07 miles (3.34 km) Victoria Tunnelin Liverpool, opened in 1848, was boredunder a metropolis. Initially used only for rail freight and later freight and passengers
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serving the Liverpool ship liner terminal, the tunnel runs from Edge Hill in the east ofthe city to the north end Liverpool docks. Used until 1972 it is still in excellentcondition, being considered for reuse by the Merseyrail rapid transit rail system.Stations being cut into the tunnel are being considered. Also, reuse by a monorailsystem from the proposed Liverpool Waters redevelopment of Liverpool's Central

Docks has been proposed. The oldest underground sections of the London Undergroundwere built using the cut-

and-cover method in the 1860s. The Metropolitan, Hammersmith & City, Circle andDistrict lines were the first to prove the success of ametro or subway system. Datingfrom 1863, Baker Street station is the oldest underground station in the world.

The 1882 Col de Tende Road Tunnel, at 3182 metres long, was one of the first longroad tunnels under a pass, running between France and Italy.

The Mersey Railway tunnel opened in 1886 running from Liverpool to Birkenheadunder the River Mersey. The Mersey Railwaywas the world's first deep-levelunderground railway. By 1892 the extensions on land from Birkenhead Park station to

Liverpool Central Low level station gave a tunnel 3.12 miles (5029 m) in length. Theunder river section is 0.75 miles in length, being the longest underwater tunnel inworld in January 1886.

The rail Severn Tunnel was opened in late 1886, at 4 miles 624 yd (7,008 m) long,although only 2 miles (3.62 km) of the tunnel is actually under the river. The tunnelreplaced the Mersey Railway tunnel's longest under water record, which it held forless than a year.

James Greathead, in constructing the City & South London Railway tunnel beneaththe Thames, opened in 1890, brought together three key elements of tunnelconstruction under water: 1) shield method of excavation; 2) permanent cast irontunnel lining; 3) construction in a compressed air environment to inhibit water

flowing through soft ground material into the tunnel heading.[10]

St. Clair Tunnel, also opened later in 1890, linked the elements of the Greatheadtunnels on a larger scale.[10]

The 1927 Holland Tunnelwas the first underwater tunnel designed for automobiles.This fact required a novel ventilation system.

See also the rapid transit history.

Main article:History of rapid transit

[edit] Longest

Main article:List of tunnels by length The Delaware Aqueductin New YorkUSA is the longest tunnel, of any type, in the

world at 137 km (85 mi). It is drilled through solid rock.

The Gotthard Base Tunnel is the longest rail tunnel in the world at 57 km (35 mi). Itwill be totally completed in 2017.

The Seikan Tunnelin Japan was the longest rail tunnel in the world at 53.9 km(33.5 mi), of which 23.3 km (14.5 mi) is under the sea.

The Channel Tunnel between Franceand the United Kingdomunder the EnglishChannel is the second-longest, with a total length of 50 km (31 mi), of which 39 km(24 mi) is under the sea.

The Ltschberg Base Tunnel opened in June 2007 in Switzerland was the longest landrail tunnel, with a total of 34.5 km (21.4 mi).
http://en.wikipedia.org/wiki/Merseyrailhttp://en.wikipedia.org/wiki/Liverpool_Watershttp://en.wikipedia.org/wiki/London_Undergroundhttp://en.wikipedia.org/wiki/London_Undergroundhttp://en.wikipedia.org/wiki/Rapid_transithttp://en.wikipedia.org/wiki/Rapid_transithttp://en.wikipedia.org/wiki/Baker_Street_stationhttp://en.wikipedia.org/wiki/Col_de_Tende_Road_Tunnelhttp://en.wikipedia.org/wiki/Mersey_Railwayhttp://en.wikipedia.org/wiki/Mersey_Railwayhttp://en.wikipedia.org/wiki/Mersey_Railwayhttp://en.wikipedia.org/wiki/Severn_Tunnelhttp://en.wikipedia.org/wiki/James_Greatheadhttp://en.wikipedia.org/wiki/St._Clair_Tunnelhttp://en.wikipedia.org/wiki/Holland_Tunnelhttp://en.wikipedia.org/wiki/Holland_Tunnelhttp://en.wikipedia.org/wiki/History_of_rapid_transithttp://en.wikipedia.org/w/index.php?title=Tunnel&action=edit&section=22http://en.wikipedia.org/wiki/List_of_tunnels_by_lengthhttp://en.wikipedia.org/wiki/Delaware_Aqueducthttp://en.wikipedia.org/wiki/Delaware_Aqueducthttp://en.wikipedia.org/wiki/USAhttp://en.wikipedia.org/wiki/Gotthard_Base_Tunnelhttp://en.wikipedia.org/wiki/Seikan_Tunnelhttp://en.wikipedia.org/wiki/Seikan_Tunnelhttp://en.wikipedia.org/wiki/Japanhttp://en.wikipedia.org/wiki/Channel_Tunnelhttp://en.wikipedia.org/wiki/Francehttp://en.wikipedia.org/wiki/Francehttp://en.wikipedia.org/wiki/United_Kingdomhttp://en.wikipedia.org/wiki/United_Kingdomhttp://en.wikipedia.org/wiki/English_Channelhttp://en.wikipedia.org/wiki/English_Channelhttp://en.wikipedia.org/wiki/L%C3%B6tschberg_Base_Tunnelhttp://en.wikipedia.org/wiki/Switzerlandhttp://en.wikipedia.org/wiki/Merseyrailhttp://en.wikipedia.org/wiki/Liverpool_Watershttp://en.wikipedia.org/wiki/London_Undergroundhttp://en.wikipedia.org/wiki/Rapid_transithttp://en.wikipedia.org/wiki/Baker_Street_stationhttp://en.wikipedia.org/wiki/Col_de_Tende_Road_Tunnelhttp://en.wikipedia.org/wiki/Mersey_Railwayhttp://en.wikipedia.org/wiki/Mersey_Railwayhttp://en.wikipedia.org/wiki/Severn_Tunnelhttp://en.wikipedia.org/wiki/James_Greatheadhttp://en.wikipedia.org/wiki/St._Clair_Tunnelhttp://en.wikipedia.org/wiki/Holland_Tunnelhttp://en.wikipedia.org/wiki/History_of_rapid_transithttp://en.wikipedia.org/w/index.php?title=Tunnel&action=edit&section=22http://en.wikipedia.org/wiki/List_of_tunnels_by_lengthhttp://en.wikipedia.org/wiki/Delaware_Aqueducthttp://en.wikipedia.org/wiki/USAhttp://en.wikipedia.org/wiki/Gotthard_Base_Tunnelhttp://en.wikipedia.org/wiki/Seikan_Tunnelhttp://en.wikipedia.org/wiki/Japanhttp://en.wikipedia.org/wiki/Channel_Tunnelhttp://en.wikipedia.org/wiki/Francehttp://en.wikipedia.org/wiki/United_Kingdomhttp://en.wikipedia.org/wiki/English_Channelhttp://en.wikipedia.org/wiki/English_Channelhttp://en.wikipedia.org/wiki/L%C3%B6tschberg_Base_Tunnelhttp://en.wikipedia.org/wiki/Switzerland


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The Lrdal Tunnel in Norway from Lrdal to Aurland is the world's longest roadtunnel, intended for cars and similar vehicles, at 24.5 km (15.2 mi).

The Zhongnanshan Tunnelin People's Republic of China opened in January 2007 isthe world's second longesthighway tunnel and the longest road tunnel in Asia, at18 km (11 mi).

The longest canal tunnel is the Rove Tunnel in France, over 7.12 km (4.42 mi) long.

[edit] Notable

The Lincoln Tunnel betweenNew Jersey andNew Yorkis one of the busiestvehicular tunnels in the United States, at 120,000 vehicles/day.

The Central Artery Tunnelin Boston carries approximately 200,000 vehicles/day.

The Fredhlls Tunnelin Stockholm, Sweden, and theNew Elbe Tunnelin Hamburg,Germany, both with around 150,000 vehicles a day, two of the most trafficked tunnelsin the world.

Gerrards Cross tunnel in Britain is notable in that it is being built over a railwaycutting that was dug in the early part of the 20th Century. Thus, arguably, making itthe tunnel longest in construction by the cut and cover method. When complete a

branch of the Tesco supermarket chain will occupy the space above the railwaytunnel.

Williamson's tunnels in Liverpool, built by a wealthy eccentric are probably thelargest underground folly in the world.

New York City Water Tunnel No. 3[2], started in 1970, has an expected completiondate of 2020.

The Chicago Deep Tunnel Project is a network of 175 km (109 mi) of tunnelsdesigned to reduce flooding in theChicago area. Started in the mid 1970s, the project

is due to be completed in 2019.

Moffat Tunnel in Coloradostraddles theContinental Divide. The tunnel is 6.2 mi(10.0 km) long and at 9,239 ft (2,816 m) above sea level is the highest railroad tunnelin the United States.

The Fenghuoshan tunnel on Qinghai-Tibet railway is the world's highest railwaytunnel, about 4,905 m (16,093 ft) above sea level.

The La Linea Tunnel in Colombia, will be (2013) the longest, 8.58 km (5.33 mi),mountain tunnel in South America. It crosses beneath a mountain at 2,500 m(8,202.1 ft) above sea level with six lanes and it has a parallel emergency tunnel. Thetunnel is subject to serious groundwater pressure. The tunnel, which is currently under

construction, will linkBogotand its urban area with the coffee-growing region andwith the main port on the Colombian Pacific coast.

The Honningsvg Tunnel (4.443 km (2.76 mi) long) on European route E69 inNorway is the world's northernmost road tunnel, except for mines (which exist onSvalbard).

The Eiksund Tunnel[3] on national road Rv 653 in Norway is the world's deepestsubsea road tunnel (7,776 m long, with deepest point at -287 metres below the sealevel, opened in feb. 2008)

[edit] Other uses

Excavation techniques, as well as the construction of underground bunkers and otherhabitable areas, are often associated withmilitary use during armed conflict, or civilian
http://en.wikipedia.org/wiki/L%C3%A6rdal_Tunnelhttp://en.wikipedia.org/wiki/L%C3%A6rdalhttp://en.wikipedia.org/wiki/Aurlandhttp://en.wikipedia.org/wiki/Zhongnanshan_Tunnelhttp://en.wikipedia.org/wiki/Zhongnanshan_Tunnelhttp://en.wikipedia.org/wiki/People's_Republic_of_Chinahttp://en.wikipedia.org/wiki/Highwayhttp://en.wikipedia.org/wiki/Highwayhttp://en.wikipedia.org/wiki/Rove_Tunnelhttp://en.wikipedia.org/w/index.php?title=Tunnel&action=edit&section=23http://en.wikipedia.org/wiki/Lincoln_Tunnelhttp://en.wikipedia.org/wiki/New_Jerseyhttp://en.wikipedia.org/wiki/New_Yorkhttp://en.wikipedia.org/wiki/New_Yorkhttp://en.wikipedia.org/wiki/Big_Dig_(Boston,_Massachusetts)http://en.wikipedia.org/wiki/Big_Dig_(Boston,_Massachusetts)http://en.wikipedia.org/wiki/Bostonhttp://en.wikipedia.org/wiki/Essingeledenhttp://en.wikipedia.org/wiki/Essingeledenhttp://en.wikipedia.org/wiki/Stockholmhttp://en.wikipedia.org/wiki/Swedenhttp://en.wikipedia.org/wiki/Elbe_Tunnel_(1975)http://en.wikipedia.org/wiki/Elbe_Tunnel_(1975)http://en.wikipedia.org/wiki/Hamburghttp://en.wikipedia.org/wiki/Germanyhttp://en.wikipedia.org/wiki/Gerrards_Cross_railway_stationhttp://en.wikipedia.org/wiki/Tescohttp://en.wikipedia.org/wiki/Williamson's_tunnelshttp://en.wikipedia.org/wiki/Liverpoolhttp://en.wikipedia.org/wiki/New_York_City_Water_Tunnel_No._3http://www.nyc.gov/html/dep/html/news/3rdtunnel.htmlhttp://en.wikipedia.org/wiki/Tunnel_and_Reservoir_Planhttp://en.wikipedia.org/wiki/Chicago_metropolitan_areahttp://en.wikipedia.org/wiki/Chicago_metropolitan_areahttp://en.wikipedia.org/wiki/Moffat_Tunnelhttp://en.wikipedia.org/wiki/Coloradohttp://en.wikipedia.org/wiki/Coloradohttp://en.wikipedia.org/wiki/Continental_Dividehttp://en.wikipedia.org/wiki/Continental_Dividehttp://en.wikipedia.org/wiki/Continental_Dividehttp://en.wikipedia.org/wiki/United_Stateshttp://en.wikipedia.org/wiki/United_Stateshttp://en.wikipedia.org/wiki/Fenghuoshan_tunnelhttp://en.wikipedia.org/wiki/Qinghai-Tibet_railwayhttp://en.wikipedia.org/wiki/La_L%C3%ADnea_(Road_Pass)http://en.wikipedia.org/wiki/Colombiahttp://en.wikipedia.org/wiki/Bogot%C3%A1http://en.wikipedia.org/wiki/Bogot%C3%A1http://en.wikipedia.org/wiki/Honningsv%C3%A5g_Tunnelhttp://en.wikipedia.org/wiki/European_route_E69http://en.wikipedia.org/wiki/Svalbardhttp://en.wikipedia.org/wiki/Eiksund_Tunnelhttp://www.tunnelintelligence.com/safety-in-detail-106.htmlhttp://en.wikipedia.org/w/index.php?title=Tunnel&action=edit&section=24http://en.wikipedia.org/wiki/Tunnel_warfarehttp://en.wikipedia.org/wiki/Tunnel_warfarehttp://en.wikipedia.org/wiki/L%C3%A6rdal_Tunnelhttp://en.wikipedia.org/wiki/L%C3%A6rdalhttp://en.wikipedia.org/wiki/Aurlandhttp://en.wikipedia.org/wiki/Zhongnanshan_Tunnelhttp://en.wikipedia.org/wiki/People's_Republic_of_Chinahttp://en.wikipedia.org/wiki/Highwayhttp://en.wikipedia.org/wiki/Rove_Tunnelhttp://en.wikipedia.org/w/index.php?title=Tunnel&action=edit&section=23http://en.wikipedia.org/wiki/Lincoln_Tunnelhttp://en.wikipedia.org/wiki/New_Jerseyhttp://en.wikipedia.org/wiki/New_Yorkhttp://en.wikipedia.org/wiki/Big_Dig_(Boston,_Massachusetts)http://en.wikipedia.org/wiki/Bostonhttp://en.wikipedia.org/wiki/Essingeledenhttp://en.wikipedia.org/wiki/Stockholmhttp://en.wikipedia.org/wiki/Swedenhttp://en.wikipedia.org/wiki/Elbe_Tunnel_(1975)http://en.wikipedia.org/wiki/Hamburghttp://en.wikipedia.org/wiki/Germanyhttp://en.wikipedia.org/wiki/Gerrards_Cross_railway_stationhttp://en.wikipedia.org/wiki/Tescohttp://en.wikipedia.org/wiki/Williamson's_tunnelshttp://en.wikipedia.org/wiki/Liverpoolhttp://en.wikipedia.org/wiki/New_York_City_Water_Tunnel_No._3http://www.nyc.gov/html/dep/html/news/3rdtunnel.htmlhttp://en.wikipedia.org/wiki/Tunnel_and_Reservoir_Planhttp://en.wikipedia.org/wiki/Chicago_metropolitan_areahttp://en.wikipedia.org/wiki/Moffat_Tunnelhttp://en.wikipedia.org/wiki/Coloradohttp://en.wikipedia.org/wiki/Continental_Dividehttp://en.wikipedia.org/wiki/United_Stateshttp://en.wikipedia.org/wiki/Fenghuoshan_tunnelhttp://en.wikipedia.org/wiki/Qinghai-Tibet_railwayhttp://en.wikipedia.org/wiki/La_L%C3%ADnea_(Road_Pass)http://en.wikipedia.org/wiki/Colombiahttp://en.wikipedia.org/wiki/Bogot%C3%A1http://en.wikipedia.org/wiki/Honningsv%C3%A5g_Tunnelhttp://en.wikipedia.org/wiki/European_route_E69http://en.wikipedia.org/wiki/Svalbardhttp://en.wikipedia.org/wiki/Eiksund_Tunnelhttp://www.tunnelintelligence.com/safety-in-detail-106.htmlhttp://en.wikipedia.org/w/index.php?title=Tunnel&action=edit&section=24http://en.wikipedia.org/wiki/Tunnel_warfare


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responses to threat of attack. The use of tunnels for mining is called drift mining. One of thestrangest uses of a tunnel was for the storage of chemical weapons [11][12][4].

[edit] Natural tunnels Lava tubes are partially empty, cave-like conduits underground, formed during

volcanic eruptions by flowing and cooling lava.

Natural Tunnel State Park(Virginia, USA) features an 850-foot (259 m) naturaltunnel,

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