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ACCIONA completes construction of the Bolaños tunnels on the Madrid-Galicia high-speed line


The excavation work for both tunnels has been completed, as well as the cut-and-cover tunnels at the Vilariño entrance.

The project includes two single-track parallel tunnels, each one 6.7 km long.

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ACCIONA Construction has completed the excavation of the Bolaños tunnels in the province of Ourense. The two tunnels are 6.7 km long and run parallel to each other, housing a single high-speed rail track.

The tunnel breakthrough occurred at the end of last year, in a symbolic milestone marking the end of the excavation works, while construction of the cut-and-cover tunnels at the Vilariño entrance was completed last week. The cut-and-cover tunnels at the other entrance, in Campobecerros, are still to be completed, as well as various other structures and the gallery linings, before the project can be concluded.

These works are part of the future high-speed line between Madrid and Galicia that is a key infrastructure project to improve rail communications between the north-west of the country and the central and southern regions of the Peninsula.

Most of the tunnelling has been excavated by a single shield Herrenknecht tunnel boring machine (TBM) with a 9.9 metre nominal excavation diameter. This machine, which was 120 metres long, was prepared and tested at ACCIONA Construction’s machinery depot in Noblejas (Toledo).

The tunnels, which have an internal diameter of 8.76 metres, were lined with 37cm-thick prefabricated ring sections. An EPDM double seal solution was selected for the lining segments to improve the waterproofing and integrity of the tunnels. This will produce better load distribution and improved compression performance.

Furthermore, instead of conventional grout, a two-component system was used during the tunnel construction process. This innovative solution is increasingly employed in these types of projects and was successfully used by ACCIONA to construct the Legacy Way tunnels in Brisbane (Australia). The use of an injection system by the shield tail around the whole ring, combined with the low density and viscosity of the two-component grout, helps to optimise the lining.

ACCIONA Construction also used an organo-mineral resin injection system to improve ground stability on the project, helping to solve the construction challenges caused by the geology.

ACCIONA Construction has constructed more than 1,200 km of high-speed lines and more than 600 km of tunnels around the world, incorporating innovative solutions and advanced materials into its projects, integrating construction processes with sustainable best practices.

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