The Sjølyst and Bygdøy Tunnels were rehabilitated as part of the Norwegian Public Roads Administration’s Oslo Tunnel Upgrade project. Located on the E18 west of Oslo, Bygdøy Tunnel was originally built in 1959 and was expanded in 2001 with an additional bridge and a roundabout over the two bridges.
The Sjølyst Tunnel was constructed in 2003/2004 and consists of a 167-meter-long tunnel made from prefabricated concrete elements. As part of the project, a new culvert for Hoffselva was built across the E18 beneath the Sjølyst Tunnel.
Aas-Jakobsen is the contracting partner with the Norwegian Public Roads Administration and holds project management responsibilities. To cover all fields in condition assessment, detailed design, and project follow-up, Aas-Jakobsen has collaborated with several firms: Vianova, Geovita, Electronova, Grindaker, NGI, Brekke & Strand, and Safetec.
The main work in the project included:
Before the project began, Hoffselva flowed through a pipe under the E18 and into Bestumkilen. This pipe had partially collapsed, causing settlements in the E18 roadway. As a temporary solution, a smaller pipe was installed inside the existing one, but the flood capacity for Hoffselva became inadequate. Consequently, the existing pipe was excavated and replaced with a new, larger, prefabricated concrete culvert designed to handle a 200-year flood. The work was carried out in a river excavation, which meant there was a strong focus on the external environment, especially in terms of river pollution. The work was also performed close to residential areas, placing limitations on noise-intensive activities. Excavating the E18 significantly impacts traffic, so the culvert replacement was completed simultaneously with the rehabilitation of the two tunnels to limit the total project duration. It was noticeable to Oslo drivers that E18 capacity was reduced in summer 2023, although work was scheduled during a period of minimal traffic and performed around the clock to minimize the duration.
It has been particularly exciting in this project to work with phased plans and construction execution to ensure continuous traffic flow in both directions on the E18. Excavation and installation of the Hoffselva culvert across the E18 were carried out in multiple phases, allowing traffic in both directions to pass at all times. The project required close monitoring and quick assessments along the way to minimize the impact of unforeseen events on traffic flow.
The Hoffselva culvert under the E18 is now equipped to handle future flood events.
The E18 beneath the Bygdøy Tunnel now has full clearance, eliminating the need for detours via the local road network.
Lars Narvestad
Direktør Samferdsel
lna@aaj.no
+47 932 23 060
