From the Brenner Pass to the Gotthard Pass, here are the longest railway tunnels in the world

From Switzerland to England, from China to Korea, from Japan to Italy, their goal is to make trains run despite everything, or rather, despite hundreds and sometimes thousands of meters of rock above the heads of travelers.

Railway tunnels are feats of engineering because they allow a strategic and sustainable mobility system like trains to shorten distances and run straight in the direction required by the route, even when it becomes necessary to dig tens of kilometers of rock between one end and the other of the tunnel.

In many cases, their history dates back to a distant past, as in the case of the Gotthard Tunnel, which was first built in 1882, even though initially it did not provide for the running of trains. And so, the technique of digging under the mountains has been refined over time, reaching the most sophisticated innovations such as those currently being experimented in the construction site of the Brenner Base Tunnel, which will become – once completed – the longest railway tunnel in the world.

The Brenner Base Tunnel is destined to break every record, first and foremost the length. The new railway line under construction beneath the Italian and Austrian Alps will reach a total length of 64 kilometers, an absolute record that will have an incredible impact on transportation in an already congested region. Once operational, travel times between Fortezza in Italy and Innsbruck in Austria (the two ends of the tunnel) will be reduced by 69% compared to today, going from the current 80 minutes to 25 minutes.

Webuild is one of the main players in the construction of this project, which has required the use of the most innovative technologies, given the characteristics of the terrain, including some areas wetted by the waters of the Isarco River, as well as the height of the mountains, which exceed a thousand meters above the future train route. To stabilize the terrain, the Webuild Group has tested the freezing technique in the Brenner Base Tunnel, securing the excavations by freezing the ground using liquid nitrogen. This technique has also been used in numerous urban excavations, such as the M4 Milan Metro, where the tunnels were built just a few steps away from the foundations of historic buildings.

The Gotthard Base Tunnel has been called the engineering work of the century by many. The tunnel, currently holding the world record with a length of 57 kilometers, runs beneath mountains that are 2,300 meters high and has a truly unique history.

Apart from the first construction that took place in the 19th century and the subsequent modernizations, the current tunnel was recently inaugurated on June 1, 2016. For its construction, approximately 4,000,000 cubic meters of concrete were used, roughly the volume of 84 Empire State Buildings, as well as 3,200 meters of copper.

The goal of the Swiss government was to create a fast connection between Rome and Zurich, allowing trains to travel between the two cities in just 3 hours. And so it was. After the referendum in 1992, which called on Swiss citizens to express their opinion on the project, work began involving over 2,000 people. The construction lasted for years until June 1, 2016, when the project was handed over to the Swiss railways, and passenger traffic began on December 11, 2016.

In Japan, the island of Hokkaido is connected to the other islands thanks to a partially underground railway. This is made possible by a great engineering work, the Seikan Railway Tunnel, which is 53.9 kilometers long and currently the second-longest in the world.

What makes it unique, however, is its depth: the railway running under the Tsugaru Strait in Japan was built at a depth of 140 meters below sea level, a record even higher than that of the Channel Tunnel. The Channel Tunnel has always been a symbol of modern engineering: the tunnel connecting France and Great Britain is 50.5 kilometers long and carries the Eurostar TGV passenger trains and the Eurotunnel shuttle for road vehicles. It is currently the longest under-sea tunnel in the world, a testament to European construction excellence.

However, large tunnels have also been built in Spain, China, again in Switzerland, in Japan, and in Korea, where the Yulhyeon Tunnel is located, the fourth-longest railway tunnel in the world. With its 50.5 kilometers, the tunnel occupies almost the entire high-speed line built to connect the Suseo station with the Southeast area of Seoul, and thanks to its characteristics, trains can reach speeds of 300 km/h, drastically reducing travel times.