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In Norway, the Norwegian Public Roads Administration (Statens vegvesen) is currently building the twin-tube Boknafjord Tunnel north of Stavanger as part of the E39 Rogfast project. This tunnel will be the longest and deepest underwater road tunnel in the world, with a length of 26.7 km and a depth of 390 m below sea level at its deepest point. Statens vegvesen has selected this project, amongst others, as a pilot project for more sustainable construction through the use of electrically powered heavy construction machinery.

Statens vegvesen has commissioned a consortium, consisting of ILF Consulting Engineers in Norway, ILF Consulting Engineers in Austria, Graz University of Technology (Austria) and Søvik Consulting (Norway), to carry out a risk assessment for the use of battery-electric dump trucks during the excavation of the Boknafjord Tunnel. The detailed study has shown through fire simulations that large fires in remote underground locations that involve either a conventional diesel or a battery-electric dump truck both require evacuation of the workforce to rescue shelters. While fires involving large traction batteries are estimated to potentially last longer, currently available dump trucks incorporate multiple layers of built-in battery management and fire safety systems to reduce the likelihood of such hazards. The study has also highlighted the limitations of the battery capacities currently in use in battery-electric dump trucks – in particular in case of operation in high-energy-demand conditions such as in deep underwater tunnels. Currently available dump trucks typically counteract this through battery regeneration, augmented by battery swapping solutions, requiring energy management strategies to be included in the tunnelling process.

By providing this service, the consortium has made a targeted contribution to one of the largest tunnel projects ever to be built in Norway and to the sustainability of tunnelling in general. The risk study has provided new insights into the fire risks and process impacts that should be considered when using battery-electric dump trucks. More information about the study, including the report from the detailed study, can be found on Statens vegvesen’s website.