Shopping on line can be easy, simple and save you lots of money. It can also take a lot of your time, frustrate you, and result in unwanted purchases. Now the same can be said for regular high street shopping, but with the vast opportunity presented by the Internet it will pay you to spend a few minutes reading this and understanding how to better optimize your Tunnel shopping experience:

1. Compare - without doubt the biggest advantage that the Tunnel offers shoppers today is the ability to compare thousands of Tunnel at a time. This is a great thing, but not necessarily all the time! Too much can be daunting at times so take advantage of the great comparison sites and where possible let them do the hard work for you.

2. Research - if it has been said it will be on the internet. Ignorance is no longer a justifiable reason for buying the wrong thing. Take the time to research in detail everything that you could possible want to know about

3. Testimonials - don't know anybody that has bought a Tunnel? Wrong! If the Tunnel is good the internet will let you know. Use the Internet as a friend and get testimonials before you buy.

4. Questions - Got a question about Tunnel then search the Forums, FAQ's, Blogs etc. Don't be afraid to ask .....

5. Reputation - Never heard of the company selling Tunnel? Don't worry, no reason why you should know every company in the world, but you know someone that does! Use the internet to find out what people are saying about Tunnel and build up a picture of their reputation for sales, returns, customer service, delivery etc.

6. Returns - still worried that even after all of the above your Tunnel wont be what you want? Check out the returns policy. There is so much competition now that someone, somewhere is bound to offer the terms that you are comfortable with.

7. Feedback - happy with your Tunnel then let people know, after all you are depending on others people input in your buying decision, so why not give a little back.

8. Security - check for the yellow padlock on the Tunnel site before you buy, and the s after http:/ /i.e. https:// = a secure site

9. Contact - got a question about Tunnel, or want to leave a comment then check out the sites contact page. Reputable companies have them and respond.

10. Payment - ready to pay for your Tunnel, then use your credit card or PayPal! Be aware of companies that don't accept them, there may be genuine reasons but given the huge amount of choice you have when buying online there is no reason at all not to buy via credit card or PayPal.



, Belgium

A tunnel is an underground passage. The definition of what constitutes a tunnel is not universally agreed upon. However, in general tunnels are at least twice as long as they are wide. In addition, they should be completely enclosed on all sides, save for the openings at each end.

A tunnel may be for pedestrians or cyclists, for general road traffic, for motor vehicles only, for rail transport traffic, or for a canal. Some are aqueducts, constructed purely for water supply — for consumption, for hydroelectric purposes or as sewers — while others carry other services such as telecommunications cables. There are even tunnels designed as wildlife crossings for European badgers and other endangered species. Some secret passage have also been made as a method of entrance or escape from an area, such as the Cu Chi Tunnels or the Smuggling tunnel#Smuggling tunnels in Rafah, Gaza Strip connecting the Gaza Strip to Egypt.

In the United Kingdom a pedestrian tunnel or other underpass beneath a road is called a Subway (underpass). This term was used in the past in the United States, but now refers to underground rapid transit systems.

The longest canal tunnel is the Standedge Tunnels in the United Kingdom, over three miles long.

In the Czech republic, the verb to 'tunnel' is a synonym for to embezzle. For example: the manager 'tunnelled' the company and now lives on the Bahamas; or, many banks collapsed because they were 'tunnelled'. Tunneling (fraud)

airport. in Singapore is a fully-underground rail line.

The central part of a rapid transit network is usually built in tunnels. To allow non-level crossings, some lines run in deeper tunnels than others. At metro stations there are usually pedestrian tunnels from one railway platform to another. Often, ground-level train stations also have one or more pedestrian tunnels under the railway to enable passengers to reach the platforms without walking across the tracks. In the United Kingdom bridges are an equally popular for pedestrian access between two or more railway station platforms.

Geotechnical investigation It is essential that any tunnel project starts with a comprehensive investigation of ground conditions. The results of the investigation will allow proper choice of machinery and methods for excavation and ground support, and will reduce the risk of encountering unforseen ground conditions. In the early stages, the horizontal and vertical alignment will be optimised to make use of the best ground and water conditions.

In some cases, conventional desk and site studies will not produce sufficient information to assess, for example, the blocky nature of rocks, the exact location of fault zones, or stand-up times of softer ground. This may be a particular concern in large diameter tunnels. To overcome these problems, a pilot tunnel, or drift, may be driven ahead of the main drive. This smaller diameter tunnel will be easier to support when unexpected conditions occur, and will be incorporated in the final tunnel. Alternatively, horizontal boreholes may sometimes be used ahead of the advancing tunnel face.

==Construction== under construction

Tunnels are dug in various types of materials, from soft clay to hard rock, and the method of excavation depends on the ground conditions.

Cut-and-cover Cut-and-cover is a simple method of construction for shallow tunnels where a trench is excavated and roofed over. Strong supporting beams are necessary to avoid the danger of the tunnel collapsing due to over head pressure.

Two basic forms of cut-and-cover tunnelling are available:

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

Boring machines , Nevada

Tunnel boring machines (TBMs) and associated back-up systems can be used to highly automate the entire tunneling process. There are a variety of TBMs that can operate in a variety of conditions, from hard rock to soft water-bearing ground. Some types, bentonite slurry and earth-pressure balance machines, have pressurised compartments at the front, allowing them to be used in difficult conditions below the water table. This pressurizes the ground ahead of the TBM cutter head to balance the water pressure. The operators work in normal air pressure behind the pressurised compartment, but may occasionally have to enter that compartment to renew or repair the cutters. This requires special precautions, such as local ground treatment or halting 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/decompression chamber some way back from the TBM, which required operators to work in high pressure and go through decompression procedures at the end of their shifts, much like divers.


Until recently the biggest TBM built was used to bore the Green Heart Tunnel (Dutch: Tunnel Groene Hart) as part of the HSL-Zuid in the Netherlands. Its diameter is 14.87 m.

Nowadays 4 even larger machines exist: 2 for the M30 ringroad in Madrid, Spain, 2 for the Chong Ming tunnels in Shanghai, China. These machines are 15,2 m and 15,4m in diameter respectively. The two machines for Spain were built by Mitsubishi/Dura Fuelgo and Herrenknecht . The TBMs for China were built by Herrenknecht.

NATM The New Austrian Tunnelling method (NATM) was developed in the 1960s. The main idea of this method is to use the geological stress (physics) of the surrounding Rock (geology) mass to stabilize the tunnel itself. Based on geotechnical measurements, an optimal cross section (geometry) is computed. The excavation is immediately protected by thin shotcrete, just behind the excavation. This creates a natural load-bearing ring, which minimizes the rock's deformation.

By special Condition monitoring the NATM method is very flexible, even at surprising changes of the geomechanics rock consistency during the tunneling work. The measured rock properties lead to appropriate tools for tunnel Strength of materials. In the last decades also soft ground excavations up to 10 km became usual.

Pipe jacking Pipe Jacking, also known as pipejacking or pipe-jacking, is a method of tunnel construction where hydraulic jacks are used to push specially made pipes through the ground behind a tunnel boring machine or shield. This technique is commonly used to create tunnels under existing structures, such as roads or railways.

Underwater tunnels There are also several approaches to underwater tunnels, for instance an immersed tube as in the Sydney Harbour Tunnel, and the Posey and Webster Street Tubes which connect the cities of Oakland, California and Alameda, California, running beneath the Alameda-Oakland Estuary.

Other Other tunneling methods include:

Choice of tunnels vs. bridges For water crossings, a tunnel is generally more costly to construct than a bridge. 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 tunnels' favor. Boston's Big Dig (Boston, Massachusetts) project replaced elevated roadways with a tunnel system to increase traffic capacity, hide traffic, reclaim land, redecorate, and reunite the city with the waterfront. Examples of water-crossing tunnels built instead of bridges include the Holland Tunnel and Lincoln Tunnel between New Jersey and Manhattan in New York City, and the Elizabeth River (Virginia) tunnels between Norfolk, Virginia and Portsmouth, Virginia and the Westerscheldetunnel, Zeeland, Netherlands. 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 km 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 Oresund Bridge and the Chesapeake Bay Bridge-Tunnel in the eastern United States.

Short tunnels A short tunnel can be built as an alternative to an overpass. One example of a short tunnel is the Croom Tunnel on the South Coast railway line, New South Wales.

Artificial tunnels Overbridges can sometimes be built by covering a road or river or railway with brick or still arches, and then levelling 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 South Coast railway line, New South Wales, which protects the line from rockfalls.

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

Examples of tunnels In history , London, mid 19th century



See also the Rapid transit#History of Rapid transit.

Longest

Notable

Other uses Excavation techniques, as well as the construction of underground bunkers and other habitable areas, are often associated with tunnel warfare, or civilian responses to threat of attack.

Media Natural tunnel

Snow tunnels are created by voles, chipmunks and other rodents for protection and access to food sources. Larger versions are created by humans, usually for fun.

For more information regarding tunnels built by animals, see Burrow

See also

References External links



, Belgium

A tunnel is an underground passage. The definition of what constitutes a tunnel is not universally agreed upon. However, in general tunnels are at least twice as long as they are wide. In addition, they should be completely enclosed on all sides, save for the openings at each end.

A tunnel may be for pedestrians or cyclists, for general road traffic, for motor vehicles only, for rail transport traffic, or for a canal. Some are aqueducts, constructed purely for water supply — for consumption, for hydroelectric purposes or as sewers — while others carry other services such as telecommunications cables. There are even tunnels designed as wildlife crossings for European badgers and other endangered species. Some secret passage have also been made as a method of entrance or escape from an area, such as the Cu Chi Tunnels or the Smuggling tunnel#Smuggling tunnels in Rafah, Gaza Strip connecting the Gaza Strip to Egypt.

In the United Kingdom a pedestrian tunnel or other underpass beneath a road is called a Subway (underpass). This term was used in the past in the United States, but now refers to underground rapid transit systems.

The longest canal tunnel is the Standedge Tunnels in the United Kingdom, over three miles long.

In the Czech republic, the verb to 'tunnel' is a synonym for to embezzle. For example: the manager 'tunnelled' the company and now lives on the Bahamas; or, many banks collapsed because they were 'tunnelled'. Tunneling (fraud)

airport. in Singapore is a fully-underground rail line.

The central part of a rapid transit network is usually built in tunnels. To allow non-level crossings, some lines run in deeper tunnels than others. At metro stations there are usually pedestrian tunnels from one railway platform to another. Often, ground-level train stations also have one or more pedestrian tunnels under the railway to enable passengers to reach the platforms without walking across the tracks. In the United Kingdom bridges are an equally popular for pedestrian access between two or more railway station platforms.

Geotechnical investigation It is essential that any tunnel project starts with a comprehensive investigation of ground conditions. The results of the investigation will allow proper choice of machinery and methods for excavation and ground support, and will reduce the risk of encountering unforseen ground conditions. In the early stages, the horizontal and vertical alignment will be optimised to make use of the best ground and water conditions.

In some cases, conventional desk and site studies will not produce sufficient information to assess, for example, the blocky nature of rocks, the exact location of fault zones, or stand-up times of softer ground. This may be a particular concern in large diameter tunnels. To overcome these problems, a pilot tunnel, or drift, may be driven ahead of the main drive. This smaller diameter tunnel will be easier to support when unexpected conditions occur, and will be incorporated in the final tunnel. Alternatively, horizontal boreholes may sometimes be used ahead of the advancing tunnel face.

==Construction== under construction

Tunnels are dug in various types of materials, from soft clay to hard rock, and the method of excavation depends on the ground conditions.

Cut-and-cover Cut-and-cover is a simple method of construction for shallow tunnels where a trench is excavated and roofed over. Strong supporting beams are necessary to avoid the danger of the tunnel collapsing due to over head pressure.

Two basic forms of cut-and-cover tunnelling are available:

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

Boring machines , Nevada

Tunnel boring machines (TBMs) and associated back-up systems can be used to highly automate the entire tunneling process. There are a variety of TBMs that can operate in a variety of conditions, from hard rock to soft water-bearing ground. Some types, bentonite slurry and earth-pressure balance machines, have pressurised compartments at the front, allowing them to be used in difficult conditions below the water table. This pressurizes the ground ahead of the TBM cutter head to balance the water pressure. The operators work in normal air pressure behind the pressurised compartment, but may occasionally have to enter that compartment to renew or repair the cutters. This requires special precautions, such as local ground treatment or halting 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/decompression chamber some way back from the TBM, which required operators to work in high pressure and go through decompression procedures at the end of their shifts, much like divers.


Until recently the biggest TBM built was used to bore the Green Heart Tunnel (Dutch: Tunnel Groene Hart) as part of the HSL-Zuid in the Netherlands. Its diameter is 14.87 m.

Nowadays 4 even larger machines exist: 2 for the M30 ringroad in Madrid, Spain, 2 for the Chong Ming tunnels in Shanghai, China. These machines are 15,2 m and 15,4m in diameter respectively. The two machines for Spain were built by Mitsubishi/Dura Fuelgo and Herrenknecht . The TBMs for China were built by Herrenknecht.

NATM The New Austrian Tunnelling method (NATM) was developed in the 1960s. The main idea of this method is to use the geological stress (physics) of the surrounding Rock (geology) mass to stabilize the tunnel itself. Based on geotechnical measurements, an optimal cross section (geometry) is computed. The excavation is immediately protected by thin shotcrete, just behind the excavation. This creates a natural load-bearing ring, which minimizes the rock's deformation.

By special Condition monitoring the NATM method is very flexible, even at surprising changes of the geomechanics rock consistency during the tunneling work. The measured rock properties lead to appropriate tools for tunnel Strength of materials. In the last decades also soft ground excavations up to 10 km became usual.

Pipe jacking Pipe Jacking, also known as pipejacking or pipe-jacking, is a method of tunnel construction where hydraulic jacks are used to push specially made pipes through the ground behind a tunnel boring machine or shield. This technique is commonly used to create tunnels under existing structures, such as roads or railways.

Underwater tunnels There are also several approaches to underwater tunnels, for instance an immersed tube as in the Sydney Harbour Tunnel, and the Posey and Webster Street Tubes which connect the cities of Oakland, California and Alameda, California, running beneath the Alameda-Oakland Estuary.

Other Other tunneling methods include:

Choice of tunnels vs. bridges For water crossings, a tunnel is generally more costly to construct than a bridge. 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 tunnels' favor. Boston's Big Dig (Boston, Massachusetts) project replaced elevated roadways with a tunnel system to increase traffic capacity, hide traffic, reclaim land, redecorate, and reunite the city with the waterfront. Examples of water-crossing tunnels built instead of bridges include the Holland Tunnel and Lincoln Tunnel between New Jersey and Manhattan in New York City, and the Elizabeth River (Virginia) tunnels between Norfolk, Virginia and Portsmouth, Virginia and the Westerscheldetunnel, Zeeland, Netherlands. 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 km 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 Oresund Bridge and the Chesapeake Bay Bridge-Tunnel in the eastern United States.

Short tunnels A short tunnel can be built as an alternative to an overpass. One example of a short tunnel is the Croom Tunnel on the South Coast railway line, New South Wales.

Artificial tunnels Overbridges can sometimes be built by covering a road or river or railway with brick or still arches, and then levelling 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 South Coast railway line, New South Wales, which protects the line from rockfalls.

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

Examples of tunnels In history , London, mid 19th century



See also the Rapid transit#History of Rapid transit.

Longest

Notable

Other uses Excavation techniques, as well as the construction of underground bunkers and other habitable areas, are often associated with tunnel warfare, or civilian responses to threat of attack.

Media Natural tunnel

Snow tunnels are created by voles, chipmunks and other rodents for protection and access to food sources. Larger versions are created by humans, usually for fun.

For more information regarding tunnels built by animals, see Burrow

See also

References External links



Welcome to Eurotunnel
Eurotunnel, operator of the Channel Tunnel. To find out more about the Group and for Shareholder information, Click here

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Welcome to Channel Tunnel Publications, the leading source of books, reports and videos on the system. Here you will find a wealth of information on all aspects of the Channel ...

Channel Tunnel
Channel Tunnel: history of different schemes and how the present tunnel works. Future developments.

Tunnel Brewery Real Ales - Lord Nelson Inn, Ansley, Warwickshire
The Tunnel Brewery Website, a micro-brewery in the small village of Ansley, Warwickshire. Producers of traditional real ales.

Carpal tunnel syndrome Introduction - Health encyclopaedia - NHS ...
Painful hand and wrist ... Carpal tunnel syndrome is numbness, tingling and pain in the thumb and fingers of one or both hands.

the Tunnel 84 Mitchell St Glasgow
Enter Tunnel Website

London-New York Tunnel
Tiscali news is up to date with all the latest breaking news. ... Tiscali Quicklinks. Please visit our Accessibility Page for a list of the Access Keys you can use to find your way ...

Eurotunnel.com Passenger home page
From Folkestone to Calais in just 35 minutes. It's a smooth journey whatever the weather. Just visit eurotunnel.com and you'll be saving money as well as time. It's so simple.

heart - The Time Tunnel
Heart 106.2, More Music Variety. Heart 106.2 features music events, showbiz news, contests, concerts, clubs and more!

Tyne Tunnel - Home Page
Located on the A19 under the River Tyne east of Newcastle Upon Tyne, Great Britain. Toll information and background.

 

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