How to Build a Tunnel Underwater?

What is the Concept behind Building an Underwater Tunnel? What is the Evolution of UnderwaterTunnels? Which is the Longest and Oldest Underwater Tunnel? What are the Reasons to prefer Immersed Tube Construction?
how to build a tunnel underwater

Underwater tunnel construction seems risky, right? Just think of how masses of people work under the pressure of so much water to build a tunnel. Even the thought of constructing it is so haunting. However, man has found a way how to build a tunnel underwater way back 200 years from now. Let’s know more about the underwater tunnel construction, uses, and methods of building it, which connects the world underneath the large water bodies. Also, we will bring you details about the longest underwater tunnel.

1. What is the History of the Underwater Tunnels?

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After a long experience of building tunnels underwater, there has been much evolution in the methodology of how a tunnel is built. There have been continuous changes in the process of how to build a tunnel underwater, resulting in a much safer and more refined underwater tunnel.

  • The idea of constructing tunnels underwater emerged back in 1818 by a French Engineer, Marc Brunel. He wanted to help the workers so that the mud and water could not ruin their hard work by constructing tunnels underwater.
  • A device merely called a tunnel shield is a rectangular iron cast with a good number of shutters. These shutters were meant to be opened once a day and dug a portion of the dirt.
  • Workers built a thick brickwork barrier that acted as the tunnel’s casing as it can be pushed forward by millimeters at a time.

Brunel was hailed for his achievement, and engineers worldwide started replicating his idea. It took nine years to complete a 1,200-foot passage beneath the Thames River in London, the globe’s first underwater tunnel. (Also read 7 Moat Around Castle Facts)

2. How did the Underwater Tunnel Evolve?

The tunneling shield is surprisingly still used to make bore-hole tunnels. This shield was made of a large wooden frame, all covered up with movable plates of iron. These iron plates protected the miners from getting flooded during work and the cave-ins. The frame was moved a bit forward with the advancement of the miners. The first tunnel was very risky and cost several lives to build. However, it was completed in 1841.

Around 1860, a new concept of building railways (railway tracks) in the tunnel came into the picture, still used today as the underground metros. This helped to get rid of highly trafficked seaports, harbors, and piers in several places. These concepts have grown to remake a better and safer tunnel by engineers through all these years. Also, check out the Road Construction Process.

3. How the Underwater Tunnel Construction is done?

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How to build a tunnel underwater? One of the most efficient methods is the immersed tube construction.

  • The elements of an immersed tube construction would be manufactured individually in a dry dock or shipyard.
  • These items are then transported to a location where a trench has previously been dug beneath the water.
  • After immersing the parts in water, they are linked together to form the tunnel.
  • In some circumstances, elements have weighed up to 55,000 tonnes and measured up to a football field in length. The main benefit of this system is that it eliminates the need for compressed air or other measures to keep water out of the tunnel, as was the case with previous construction. (See How does a Water Wheel work?)

4. Why Immersed Tube Construction is used?

After knowing how to build a tunnel underwater, the below list gives the reasons for preferring immersed tube construction. 

  • The costs of building an immersed tube tunnel are substantially lower than those of drilling a tunnel deep below the surface. The duration of the project also becomes shorter.
  • Work and advancement of miners or workers in a bored tunnel would be limited to two ends. There is also relatively little traffic disturbance on the water channel where it is being installed.
  • Tunnel boring entails a number of safety considerations, such as responding to the water and air pressure that are not present in the construction of submerged tubes. However, submerged tube tunnels are prone to sabotage and shipping dangers because they are generally close to the channel bed.
  • These issues can be overcome by taking proper care of the engineering designs and measurements made, considering the immense forces exerted during laying and joining procedures. Must read How Cranes Work?

5. Which is the Longest Underwater Tunnel?

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The world’s longest underwater tunnel is the 53.85 km long Seikan Railway Tunnel in Japan, passing underneath the Tsugaru Strait

  • It connects the Aomori Prefecture on Honshu Island and Hokkaido Island.
  • The railway track has been laid at a distance of 140 m underneath the seabed, making it the world’s significantly deepest and longest tunnel ever constructed. Also, check out What is a Flight of Stairs?
  • The magnificent tunnel was planned between 1939 and 1940.
  • The construction of this tunnel began in 1971 and reached its stages of completion in 1988, costing about $3.6 billion.
  • The Japan Railway Construction, Transport, and Technology Agency took up this giant project, with the operation sector being handled by the JR Hokkaido. (Also read Why did they built the Brooklyn Bridge?)

How to build a tunnel underwater has been an interesting field of research and development for years. There are still more and more innovations being carried out to develop methodologies. Never miss taking a ride or visiting these underwater tunnels if you get an opportunity. (See How to Size a Rough Opening for Bifold Door?)

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