Construction of any tunnel is a lot of work, requiring a lot of time and money, and is also associated with a risk to the lives of workers. While digging a tunnel, the rocks on top can collapse, and builders risk being left under tons of earth. Digging tunnels underwater is even more dangerous because workers can easily drown. Such an accident first occurred in 1827 during the construction of an underwater tunnel under the British Thames. During the digging process, water entered the tunnel, killing six workers. Fortunately, thanks to modern technology, digging tunnels underwater takes less time and is not as risky as it used to be.
Digging underwater tunnels used to be a risky business, but thanks to modern technology, everything has changed. Source: rg.ru
Contents
- 1 What is a tunneling shield
- 2 What was invented by Marc Brunel
- 3 The very first underground tunnel in the world
- 4 How tunnels are dug under water
- 5 Construction of sections of an underwater tunnel
What is a tunneling shield
Almost all tunnels, both onshore and underwater, are usually built using a tunneling shield. This is the name of a cylindrical metal structure that prevents rock collapse and, moving forward, creates a passage. During the operation of this giant, rocks move along a conveyor and are removed outside.
Mining shields have a diameter of several tens of meters. Source: rbc.ru
Using a tunneling shield, you can build tunnels with a diameter of up to 19 meters. The tunnels created in this way become parts of the subway, railways and other routes.
What Marc Brunel invented
The inventor of the tunneling shield is the English engineer Mark Brunel. He was inspired to create such a mechanism by shipworms: he noticed that these creatures make holes in the wood using a head with a hard shell. They leave a layer of lime on the walls of the holes they make to strengthen them.
English engineer Mark Brunel. Source: britannica.com
The inspired engineer created a cylindrical structure that had compartments for workers. The tunnel began on the surface and gradually went deeper. While underwater, the invention protected people from flooding – they manually dug a tunnel. After part of the hole was made, the structure was pushed forward, and the back of the dug tunnel was covered with brickwork for strengthening. The extracted soil was transported to the surface.
Image of Marc Brunel’s tunneling shield in action. Source: maximonline.ru
Work inside the tunnel shield. Source: wikimedia.org
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The very first underground tunnel in the world< /h2>
With the help of Marc Brunel's tunneling shield, the very first underground tunnel in the world was dug. It was located in London, under the River Thames – its construction began in 1825 and was completed in 1843. At first the tunnel was used as an underground passage. In 1865 it was bought by the East London Railway and is now part of the London Underground.
The Thames Tunnel is part of the London Underground. Source: wikimedia.org
How tunnels are dug under water
Today, instead of shields, tunnel boring machines. The main part of these huge cylindrical structures is the cutting head. It rotates, cuts the soil, and thus creates a tunnel. For soft and hard rocks, cutters of different shapes and hardness are used.
A tunneling shield and a tunnel boring complex are almost the same, it’s just that the second design is more technologically advanced. Source: 21mm.ru
To move forward, tunnel boring systems use a system of hydraulic cylinders. It applies high pressure to the cutting head of the device, which allows it to cope even with very hard rocks.
Tunnel drilling complexes also have a soil removal system. The rocks immediately end up on the conveyor belt and are brought out, so drilling can proceed almost without stopping.
In the modern world, tunnel drilling looks something like this, with minimal heavy manual labor. Source: mirvu.ru
To prevent the tunnel from collapsing, immediately after the drilling head the walls are reinforced with concrete or other material. After laying the entire route, rails are installed in the tunnel, electricity is supplied, and so on.
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Construction of sections of an underwater tunnel
In some cases, tunnels are built on the surface, and only then immersed under water. The sections are made of steel or reinforced concrete and are usually rectangular or oval in shape.
Simultaneously with the tunnel sections, a deep trench is dug at the bottom of the reservoir. Its bottom must be leveled and covered with a layer of gravel so that the structure stands firmly.
Building underwater tunnels using sections is considered the safest. Source: news.rambler.ru
Then the sections are lowered into the trench one by one and fastened together. To ensure tightness, sealing rings are installed between them. After assembly, all the water is pumped out of the tunnel, and then it is provided with light, and so on.
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As you can see, modern technology allows you to build amazing things. If you are interested, right now you can read about the longest bridges in the world and a huge copy of the Moon in Dubai.