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miércoles 27 enero 2021

Bertan > Bertan 10 Trenes de Gipuzkoa > Versión en inglés: Bridges and tunnels

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Bridges and tunnels

The great virtue of the railway, the scarce friction between the wheel and the steel tracks, a factor which allows it to haul great loads with little effort, becomes a disadvantage on climbing slopes, where the engines slip easily when faced with the smallest obstacle. Ramps of over 3% are almost insurmountable for conventional trains, and other systems have to be used such as rack or funicular railways.

101. The Euskotrenbideak viaduct over the Urola River in Zumaia.
101. The Euskotrenbideak viaduct over the Urola River in Zumaia.

In a territory like Gipuzkoa, with its extremely rugged orography, the establishment of railways was only made possible by taking recourse to the carrying out of impressive engineering works.

It was thanks to the construction of daring viaducts across rivers and valleys and the boring of long tunnels to overcome the mountains, that a viable railway network could be set up in Gipuzkoa.

The first great engineering work carried out in Gipuzkoa was the construction of the Northern Railway. A total of 22 tunnels with a combined length of 10,402 m. through the entrails of the earth, punctuate the hard ascent from Beasain to Alsasua. Outstanding is the tunnel of Oazurza which, when it was built in 1863, with its 2,957 m. in length, was the longest in the state, a record it still holds in the Basque Country. Another 9 tunnels completed the route to Irún, with a total length of 3,822 m.

The Northern Railway Company also had to build important bridges, among which was the outstanding Ormaiztegi viaduct, with its five metallic separations and 289 m. in length. This bridge has recently been pensioned-off, as a new concrete version has been built nearby. However, thanks to the love of the people, due to which it has become an inseperable image, the old bridge will be kept as a monument. Another nine viaducts span the main rivers in Gipuzkoa.

102. The Andoain tunnel.
102. The Andoain tunnel.

Although the philosophy of narrow-gauge lines was that of avoiding the building of large works as far as possible, certain geographical factors often meant that the entrails of the earth had to be perforated. Excellent examples of this were the late Plazaola railway line and the popular Topo train. The former, between Andoain and Leiza, required 34 tunnels, coming to a total of 3,000 m., which are now used for leisure by strollers and bicycle riders. The Topo, or "mole" as its nickname implies, has 14 tunnels which represent a 20% of the whole line, although the most outstanding tunnel is nº 2 for its 2,072 m. in length.

An outstanding example of good work was offered to us by the no longer existing Urola railway, built in 1926 by Gipuzkoa County Council. Its daring route meant that it could easily follow the rugged course of the river Urola between Azkoitia and Urretxu, thanks to the 16 bridges and 17 tunnels built along its short route. Its exemplary layout is still the envy of the car drivers who circulate in this area, since they have to put up with one of the most winding and busy roads in Gipuzkoa.

103. The Ormaiztegi viaduct.
103. The Ormaiztegi viaduct.

Nor could the Vascongados Railway avoid great works of infrastructure, as it had to build a total of 28 tunnels, coming to 8,288 m. in length. Among these tunnels is the shortest in Gipuzkoa, that of Mogote, situated between Deba and Itziar, which measures 26 m. in length. Very near here, Euskotrenbideak has started building the new Arronamendi tunnel, with almost 1,200 m. in length, which will mean the elimination of one of the most troubled spots on the line, given the instability of the banks supporting the stretch to be rectified. The graceful metallic Zumaia viaduct and the no less attractive curved viaduct in Orio complete a stretch where we mustn't forget the unusual retaining walls lying between Elgoibar and Alzola. Their huge round stones seem to have taken direct inspiration from Inca empire constructions.

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