FCC Construcción

The Pajares tunnels belong to the project for the new high-speed railway line between León and Asturias. These two-track tunnels provide passage through the Cordillera Cantábrica mountain range, shortening the route in current use from 83 to 50 kilometres. The layout to be replaced by the new route was built in the second half of the 19th century and was a piece of extraordinary engineering for its time.

The tunnels are two parallel tubes 24.9 kilometres long apiece and are therefore the sixth-longest tunnels in Europe and the seventh-longest in the world. Their inner diameter is 8.50 metres, and they are designed for speeds of over 250 km/h.

Five tunnel-boring machines participated in the excavation work, which was a great engineering challenge.

The tunnel's execution was divided into four lots. FCC did the first section, which included execution from the southern mouth of the tunnels between La Pola de Gordón and the district of Folledo. The first 7.9 kilometres were bored with two TBMs, and the remaining 2.5 kilometres were handled using conventional methods.

The variety of formations the tunnels have had to penetrate forced designers to come up with an extremely wide range of structural elements in terms of tunnel linings.

The tunnels are lined with 50-centimetre, prefabricated, reinforced concrete segments manufactured on site. To uphold a higher level of safety, every 400 metres cross-galleries have been built between the tunnels to facilitate maintenance work and evacuation, should that ever become necessary.