New metro line Akalla-Barkarby, Sweden

Project Järfällatunneln represents extension of blue subway line on the northwestern suburbs of Stockholm. Metrostav Norge AS participated on the excavation of track tunnels, cross passages and technical rooms between current last station Akalla and newly built stations Barkarby and Barkarbystaden.

Basic information

Client: Stockholms läns landsting, Förvaltningen för utbyggd tunnelbana (FUT)
Main contractor: SBT Sverige AB
Contractor: Metrostav Norge AS
Construction period: 08/2020 – 03/2023
Price: app. 500 000 000 SEK w/o VAT

Project characteristics

Extension of metro line in Stockholm. The Blue Line is being extended from Akalla to Barkarby – an important travel hub for future public transport passengers, connecting bus services to metro, commuter and regional train services.

Järfälla Municipality is expected to grow to around 115,000 inhabitants by 2030. A new district is emerging around the new station in Barkarbystaden, and the Veddesta industrial area, which is closest to Barkarby station, is also being transformed into an urban environment.

Project data

2 ks (1845 m + 1865 m)

Tunnels:

17 ks (315 m)

Cross passages, technical buildings:

2 ks

Shafts:

1 ks

Pumping stations:

T5,5 (35 m²)

Tunnel profile:

120 m²

Ventilation cavern profile:

132 000 m³

Excavated volume:

3 200 m³

Shotcrete:

1 200 000 kg

Cement grouting:

29 000 ks

Rock bolts:

19 000 m²

Lining:

Challenges / Specifics of the project

Complicated and very accurate excavation method along passage under Forbifarten Stockholm tunnels (=2 highway tunnels above our metro tunnels). Difference between bottom of the highway tunnels and the roof of metro tunnels is only 4,9m. That brings very strict limitations and challenges from technological and also controlling point of view.
Use of rock splitting method to eliminate the fracture zone around the contour along the Forbifarten passage.
Use of wire sawing method in part of track tunnels and for excavation of one ventilation shafts.
Breakthrough to existing station without affecting the traffic of the metro.
Excavation underneath residential area with low overburden which brings strict vibration and noise limits, strict living environment rules and complicated ventilation.
Complicated geometry and space conditions during excavation of ventilation rooms and big caverns, use of electronical ignition system.
BIM based project
CEEQUAL rating and proximity of Natural reserve brings strict environmental rules