of tunnels

Lines 9 and 5 of the Barcelona Metro

ACCIONA is a leading company in the design, construction and commissioning of transport infrastructure in cities. Throughout its history, the Company has developed innovative, sustainable and responsible solutions adapted to specific cases, both in Spain and worldwide.

2002 saw ACCIONA use the EPB TBM, with a record 12.09m bore, to perform works on this section of Metro Line 9. The works consisted of boring two tunnels, of 4.6km and 6.15km length, at great depth, between the different stations of the section.


Furthermore, ACCIONA carried out the extension of Barcelona Metro Line 5, involving 2.6 km of new route, three stations and a 300m-long train depot. Conventional tunnel excavation methods were used in all the underground works in Barcelona's complex urban environmen.


The scope of the project involved the implementation of the infrastructure, superstructure and electrification of the extension of line 5 of the underground railway in the city of Barcelona, from the previously existing Horta station to the new Vall d'Hebron station. The total length of the section is 2.47 km.

The project included the excavation of a 1.568 m long tunnel for a double-track line, the excavation of a 300 m long area to park trains (capacity for five tracks), the excavation of a tunnel for a train bypass and three stations, as well as their corresponding access.

Drilling of the main tunnel and the rest of the underground elements was carried out using the new Austrian method (NATM) by mechanical excavation (drilling and blasting) split into heading and upper bench excavation phases and the installation of a flexible support. The caverns for the construction of the stations were bored using drills and blasting.

The works included:

  • Construction of a 1.67 km tunnel and three caverns, all excavated using the NATM.
  • Due to the urban environment where the work is located, specific regulations on the generation of noise and dust during the work were respected. The location of the works in a predominantly urban and densely populated area made it necessary to analyse and forecast solutions for the road traffic, streets and supply services affected. Thus, temporary detours and the necessary negotiations were established with business owners to maintain services during the construction of main roads and other above-ground works.
  • Several construction methodologies were used to carry out this project. The tunnel of the line was built by excavating the heading and bench. The stations were large caverns built using the side galleries and central pillar method. For the accesses, the deep vertical wells were executed with sheet piling, and inclined galleries and fortified enclosures have also been executed.
  • Due to the complexity of the terrain, horizontal drilling was carried out in the tunnel on each of the excavation faces, and vertical drilling was carried out in each of the station lobbies and wells.


This represents the longest underground line in Europe, at 50 km long and with 52 stations. It is also the deepest line in Barcelona, reaching a depth of almost 85 m. Line 9 of the Barcelona Metro established a direct connection between Barcelona airport and the city centre.

The Barcelona Metro Line 9 project is an automated, driverless metro system built in a dense urban area in Spain's second largest city, with a population of approximately 1.6 million people. ACCIONA was responsible for managing the construction and design equipment of the design and construction contractor; coordinating all interfaces and disciplines during design and construction; and implementing quality, safety and environmental management systems.


Design and Construction

The contracts awarded are located in a very complex urban environment, and involved the construction of 3.9 km of drilled tunnels using the EPB tunnel boring machine, six large underground stations and 657 m of false tunnels. Moreover, an additional 1.5 km of excavated tunnel was carried out with the same EPB and two "cut and cover" structures. Also included were the track-laying and catenary system. Due to the lack of surface area in this urban location, a single-track tunnel with a two-storey railway configuration was designed for this metro line.

The scope of the project included the construction of several underground concrete structures, including vertical wells for station access, stations between diaphragm walls, as well as other structures, all located in the main urban area of the city. These structures are as follows:

  • 60-m wide crossing well: a well for the tunnel boring machine was made at the Sagrera station to join the two metro lines. This challenging well is 60 m wide, executed using screens with a total area of 9,152.57 m2 and a depth of 29 m.
  • Access axis: The access axis for the tunnel boring machine in Gorg, executed using screens with a total area of 2,015 m2 and a depth of 25.19 m.
    • Gorg station: a very shallow station, and in light of this it was executed using non-circular screens.

    • La Salut station: a circular well with screens with an internal diameter of 26.80 m and a depth of 37.63 m.

    • Llefiá station: a circular well with screens with an internal diameter of 28 m and a depth of 50 m.

    • Bon Pastor station: a circular well with screens with an internal diameter of 28.25 m and a depth of 30.81 m.

    • Onze de Setembre station: a circular well with screens with an internal diameter of 28.40 m and a depth of 34.50 m.

A total of 4,199 m of 40 cm thick intermediate slab, which divided the tunnel cross-section into two traffic levels (one in each direction), was also carried out.


Soil stabilisation, geotechnical conditions and proximity to the metro line

Due to the conditions of the soil, soil treatments were necessary both on the surface and under the buildings above the tunnel works.

Due to the extensive monitoring and reliability of the actual data, all existing metro lines remained open at all times during the tunnelling work, where the settlements were higher than expected.



The design team did a tremendous amount of work and technical assessments to obtain better solutions for various problems:

  • Innovations, including an improved TBM access axis that allowed for an accelerated advancement of the tunnel.
  • The development of the BIM 3D model significantly helped construction.
  • Extensive consultation was carried out with the community and other stakeholders; the information gathered from the consultation was incorporated into the design of the tunnel, surrounding infrastructure and tunnel systems.

ACCIONA developed and implemented an Occupational Safety Management System. Due to the effectiveness of its H&S plan, which ACCIONA applies to all its projects, the company was rewarded the Atlante Health and Safety Award. In Barcelona, ACCIONA used several means to communicate the results of inspections, audits, accidents, improvement activities, etc.

Occupational health and safety management system

ACCIONA developed and implemented an Occupational Safety Management System. Due to the effectiveness of its H&S plan, which ACCIONA applies to all its projects, the company was rewarded the Atlante Health and Safety Award. In Barcelona, ACCIONA used several means to communicate the results of inspections, audits, accidents, improvement activities, etc.



The project was carried out between the "Fira de Barcelona" area and the Llobregat river, with a length of 3.8 km.

ACCIONA executed the project using the "cut and cover" technique at three underground stations (Fira, Parc Logístic and Mercabarna); three ventilation and emergency wells (Pozo Motors, Pozo 7A and Pozo 7B); two output shafts for the TBM on the Fira side and the Llobregat side of the logistics section of Pare, and a 371 m long mud-wall tunnel section between the axis on the Llobregat side and the logistics station of Pare, which will connect line 2 of the metro in the future.

Soil treatment prior to the execution of the tunnel was also carried out to guarantee the stability of the structures.

  • Mercabarna station: A conventional station with 120.8 m long side platforms. It had a total surface area of 3,450 m2 and the depth of the concrete walls was 20.5 m.
  • Fira station: An interchange station for lines 9 and 2. This was designed on two levels, with only the top level corresponding to line 9, although it was prepared to allow for the construction of line 2 in the future.
  • Parc Logístic station: Also a transfer station between lines 9 and 2. The difference is that both lines are on the same level, with a shared upper lobby for both stations. The main area of the cement grout wall is rectangular: 152.50 m long and 17.90 m wide, with a cement grout wall depth of 25.60 m.

The Parc Logístic station is a 1.20 m thick wall-to-wall tunnel, with a length of 371 m. This structure provides the connection from line 2 to line 9 by means of an overhead bridge, which allows the track on line 2 to merge with the track on line 9, passing under the other line 9 track.




The stations of the section of work between the University Area and Bifurcació were executed. It consisted of the execution of three underground stations: Collblanc (deepest station in all of line 9), Torrassa and Gornal. In addition, a well outlet for the tunnel boring machine at the Campus Sud station.

Awards and recognitions

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