The Skanska/Vinci joint venture has received the go-ahead for 11km of tunnelling worth US$315M to complete the Hallandsås tunnel project in Sweden where excavation has been suspended since 1997.

In November 2002, the joint venture was awarded the contract to finish the tunnels, but since then the contract has been pending the resolution of permit issues to become binding. During this period, the joint venture and client, the Swedish Rail Administration (SRA), have investigated alternative techniques to excavate through the challenging ground conditions in the Mölleback zone (MBZ) of the ridge. The predominant rock type is gneiss, with many fissures and clay bands; as detailed by prior experience, ground water is a particular problem. The joint venture has opted for a 10.6m Herrenknecht TBM to run in either open or closed mode for the remaining 5.6km of twin tunnels. The TBM has been costed at approximately US$48M and is scheduled for delivery in 2005. The MBZ will be prepared for the arrival of the TBM with pilot tunnels and freezing or grouting operations to stabilise the ground. In the 60m section one, brine is used to freeze the annulus and air-cooling is also carried out from the pilot to maximise the freezingÕs effectiveness. In section two which is also 60m, freezing on a smaller scale is deemed adequate, without additional air-cooling. For the longer section three, the approach is traditional cement grouting.

Contractor Kraftbyggarna originally started constructing the tunnel in September 1992 and by May 1993 was using a TBM in open mode for excavation. Two months later it got jammed and work continued using drill and blast. Following a dispute with the SRA, Kraftbyggarna quit the project in December 1995 and in January 1996 Skanska took over construction, opting to continue using drill and blast.

Extensive water leaks became apparent and groundwater contamination problems were experienced with Rhoca Gil, the chemical sealing agent used to combat them. By October 1997 work on the tunnel was suspended pending investigation and a decontamination programme was started. Skanska quit the project in 2001 and both Skanska and Rhoca Gil were later fined for the incident.

Related Files
Hallandsås tunnels