As part of the Norwegian Public Roads Administration’s maintenance programme, Multiconsult was hired under a framework contract to perform a condition survey of the Fosskollen tunnel in Lier Municipality, Buskerud.
The survey was commissioned due to uncertainty as to whether the concrete vault had been weakened as a result of damage to the concrete.
The tunnel was built in 1972. The tunnel portals are cast-in-situ, while the rest of the tunnel consists of a vaulted concrete roof made of precast elements.
Scope of work
We performed a visual inspection, and also took concrete samples for chloride analysis.
Carbonation depths and concrete cover were measured to check the lifespan and the likelihood of further deterioration.
The calculations of the static load capacity of the vault were reviewed. A rough assessment was made of the vault’s resistance to rocks falling from above.
- Conditions surveys and reports
- Review of calculations
- Analysis of concrete samples