The municipality of Oñati has an imposing karstic landscape in limestone rock that is a great attraction, with extensive complex speleologic phenomena, where the Arrikrutz cave is located. The variety and dimensions of the formations made by dissolution and precipitation make it an extremely interesting system, with huge groups of flowstones, stalagmites and an underground watercourse.
The cave is located in the middle of the road between Oñati and the Aranzazu Sanctuary, about 400 m above sea level. Open to the public since June 2007, a visit lasts 60 minutes, with a trajectory that is 500 m in length with 35 m of descent. The tour follows a hanging walkway with a modern dynamic lighting system.
GFRP composite is the ideal material for this purpose as it does not become degraded by the humidity in the heavily corrosive atmosphere. At the same time, the strength of the profiles ensures a sturdy, non-slip walking surface for visitors to the impressive surroundings.
As well as enhancing the beauty of the cave the profiles’ pale grey colour constituted a major plus for the project as it made the walkway easier to assemble in what were dark and difficult lighting conditions.
The cramped conditions also ruled out the use of machinery inside the cave. All the profiles therefore had to be conveyed to the bottom of the cave manually, just like on an expedition to the unknown. In this context the low weight of the profiles was therefore a distinct advantage.
Sobrino J.A.; Pedestrian bridges with hybrid Stainless Steel-GFRP Structure. Proceedings of the International Bridge Conference (IBC-11-51). Pittsburgh (USA), June 2011.