Seoul, Apr 2 (EFE) .- Trains reaching 180 kilometers per hour 50 meters underground. With this formula, which poses complex engineering challenges and will be released in 2023, Seoul seeks solutions to the great mobility challenge faced by the world’s major conurbations.

Like many large cities, the South Korean capital cannot be understood only in its strict municipal area.

Its 10 million inhabitants are joined by 13.4 million in the surrounding Gyeonggi province and 3 in the adjacent city of Incheon, drawing an urban tangle of more than 26 million souls.

In this region, people “take an average of 133 minutes a day to go to and from work compared to the 28 on average recorded in the OECD,” the director of high-speed rail in the capital region explained in a recent presentation. of the South Korean Ministry of Transportation, Jang Chang-seog.

THE SOLUTION IS UNDER THE FEET

Although Seoul is preparing a pilot plan to test drones as a means of public transport between now and the next few years, it has been a decade since it began to look in the opposite direction for large-scale solutions that alleviate the nightmare of rush hour commuting.

This underground project, baptized Great Train eXpress (GTX), began to become a reality in 2019 with the construction of the first of its three lines, the A, which will link the bedroom cities of Paju and Hwaseong in less than 55 minutes and will have only 10 stations.

Of those 10, three will be in two large central districts of Seoul and connected to existing subway interchanges.

“The trains will run at an average of 100 kilometers per hour compared to 30 kilometers per hour on average if you go by bus, subway or by car at rush hour,” said Jang, who explained that “you can go from the periphery to the downtown Seoul in less than 30 minutes and vice versa. “

When the three GTX lines are operational around 2025 – which will have a combined cost of 14.8 trillion won (about 13,000 million dollars) and will be financed through a public-private scheme – the vehicles will circulate daily in the region. They could also be reduced by about 880,000, improving the lousy air in Seoul.

NO SPACE ON SHALLOW SURFACE

However, the option of building new lines underground – with a route as straight as possible for trains to reach high speeds – posed challenges from the beginning in a city that began to bore holes in its soil in the 1960s for transport and commercial surfaces and It hasn’t stopped since.

“In addition to the subway, normally built at a depth of 20-30, and the shopping galleries, there are pipelines for water, gas, sewerage, fiber optics or even geothermal energy infrastructure”, lists Kim Chang-yong, from the Institute of Engineering. Civil and Construction Technology (KICT), which participates in the project.

The solution, then, was lower still, about 50 meters on average, which makes the GTX the most ambitious network in terms of maximum speed of the convoys and kilometers of tracks at great depth (more than 300) when compared with projects such as the London Crossrail or the existing underground sections of the French RER.

A DESCENT THAT IMPRESSES

Going down in the access elevator to the tunnels of the GTX line in the town of Goyang (northwest of Seoul) is impressive.

In this section, the so-called Sequential Excavation Method (SEM) is being used and underground water is filtered through the thin layer of concrete that is applied as the drilling progresses.

Of course, the phones do not have coverage now, but that will not be a problem when line A is released in 2023, whose trains and stations will use LTE technology for operations and maintenance, say those responsible.

Another great challenge will be to drill deep tunnels under the Han River, where the soils are very soft and hydro-shield tunnel boring machines will be used, colossi more than 100 meters long that inject bentonite into the earth to stabilize it and that, according to excavated , they regurgitate it through some pipes.

“We believe that the use of the great depths will be extended in the future in cities and that thanks to the GTX project, the security protocols, technology and related intellectual property will improve,” he explains, at the exit of the tunnels. , Kim Chang-yong.

Kim emphasizes that there are similarities with the undergrounding of the M-30 in Madrid, a project that he personally visited and that impressed him, and he hopes that, in the same way, the achievements of the GTX can be exported to other countries.

Andres Sanchez Braun

(c) EFE Agency

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