How are tunnels built in the depths of the sea in the presence of water?

 The longest tunnel in the world under water, with a length of 53.9 km. How are these tunnels built in the presence of water?

The primary goal of science has always been to serve man and save his time, money and effort.

Perhaps civil and architectural engineering is one of the most important sciences that serve man in various fields, due to its achievements such as towers, dams, roads and bridges, which shorten distances and facilitate traffic in an unimaginable way.

One of the most recent achievements is the ability of civil engineering scientists to study and implement underwater tunnels, which represented a quantum leap in the civil structure of many countries.

Tunnels are one of the greatest masterpieces of architecture built by humans, which saved a lot of time and money for transporting materials and others.

Building tunnels on the surface of the earth is much easier compared to tunnels that are built under water, as building an underwater tunnel requires a lot of labor, time, money and effort.

History of underwater tunnel construction

The oldest tunnel built under water was on the River Thames and became known as the Thames Tunnel. It was 0.44 km long and took nearly a decade to complete because the technology that was available at that time was very old.

It involved a lot of human labor and there were few machines available to assist in construction at that time.

The longest underwater tunnel ever built is the Seikan Tunnel, which is located at the bottom of the Tsugaru Strait, with a length of 53.9 km and connects Hokkaido Island with Aomori Prefecture.

The tunnel was built in 1988 and it took almost three years to build this tunnel because the technology in Japan is very advanced compared to other parts of the world.

How does the process take place underwater?

The answer to this question dates back to 1818 when Marc Brunel, a French inventor, built a device called the TBM or Tunnel Boring Machine.

The tunnels that pass under the water are one of the engineering wonders that man can build, whether for recreational, strategic or other purposes.

But how are these engineering wonders built, with water spurting from everywhere even the tiniest hole? 

At that time the ports were crowded with ships carrying coal and other commodities, the roads were full of horse-drawn cars, and the crowds were turbulent.

Especially since the industry was on the rise, so they needed a way to increase the rate of trade and travel without increasing the traffic.

At the time, the idea of building an underwater tunnel was very strange, but the engineers also realized that it was the most efficient solution, and of course there were risks.

For example, the pressure could push mud and water through the cracks, and the entire tunnel would break, which of course would be disastrous.

However, Mark Brunel, known as one of England's most brilliant engineers, developed an ingenious device that could penetrate the sea floor without allowing any mud or water to seep in. Its construction was genius.

Mark used something like a submarine, about 12 meters long, protected by a wall of steel and bricks.

The process was done by using that machine to carry sand from the watery medium, which gives an opportunity to the workers to fill the removed area with cement after planting and installing the waterproofing walls around the excavated area, and in this way they were able to stop the flow of water and remove the excess water from the tunnel area.

The tunnel was dug by that machine, where the workers break the rocks and dig with sand, then others put a protective cover around the excavated areas, and the workers in the front were the ones who dig through small cavities, while the people behind them put the stones (protective cover) on The length of the tunnel their colleagues had dug, and the workers had to develop two outlets, one to get rid of mud and sand, and the other for water.

Engineers predicted that it would take only 3 years, but in fact it took about 18 years, and finally, the bricks were fortified with concrete, and it ended with the development of a tunnel capable of withstanding horse-drawn vehicles and trains later, and the tunnel is still an important part of the railway network in London For a short time, it was considered the eighth wonder of the world.

However, instead of building a tunnel by digging, it was developed that a tunnel could first be built on land and later placed under water.

Such a tunnel is not built entirely, but in sectors, then it is floated with the help of additional weights, then each part is joined to form the tunnel, and water is pumped between the joints hydraulically, so that the inside of the tunnel becomes isolated from water.

The main advantages of underwater tunnel construction are:

It allows ships to pass over it while traffic is still going inside.
Very fast to navigate rather than using traditional over water navigation methods.
Connecting places that were difficult to connect except by air or by boats and ships.

It provides an opportunity to see marine life in its natural state if the walls used are transparent.
Another new method of creating underwater tunnels is the cut and cover method

To use this method, builders dig a trench in the river bed or ocean floor. Then they dump the prefabricated steel or concrete pipe into the trench. After covering the pipes with a thick layer of rock, workers connect the pipe sections and pump out any remaining water.

This method was used to create the Ted Williams Tunnel, which connects the southern part of Boston with Logan Airport. The twelve giant steel pipes sunk into the trench are 325 feet long and actually contain fully constructed roads!

Engineers always come up with new ideas. Based on experimental rock-cutting methods, underwater tunnels of tomorrow can be built with the help of high-pressure water jets, lasers, or ultrasonic acoustic machines.

New technologies can enable the construction of tunnels that once seemed impossible. For example, some engineers want to build a transatlantic tunnel to connect New York to London. The 3,100-mile tunnel can accommodate a train that can travel at 5,000 miles per hour. A trip that now takes 7 hours by plane may one day take less than an hour!