Engineering the world’s first ship tunnel

If all goes according to plan, construction of the Stad Ship Tunnel in in western Norway will begin early this year and aim for completion at some point during 2025/26.

At a hazardous and highly weather-exposed section of the Norwegian coastline, the tunnel will enable ships to navigate the Stadhavet sea more easily, improve safety at sea, and support regional commerce and industry. Currently, as the most windswept part of the nation’s coastline, stormy for around 100 days of the year, ships can often for wait days before they are able to pass through.

However, the size of the project, safety requirements, and infrastructure limitations will present major engineering challenges.

Because roads in the area are unable to take construction vehicle traffic, materials will be transported by sea. The actual tunnel construction is expected to use conventional drilling and blasting methods utilising underground pallet rigs and drilling rigs to remove gneiss – a very hard, solid metamorphic rock – to construct a tunnel 1.7km long, 26.5m wide, and 37m high.

The cross-sectional area of the tunnel will be 1,661 square metres, and the total volume of rock expected to be removed is around 3 million cubic metres – equivalent to approximately 8 million tonnes of blasted rock.

If necessary, cofferdams – watertight enclosures which are pumped dry to enable construction work below the waterline – will be created.

Once extracted, some of the rock will be used to create, develop and expand new and existing land areas for further industry and commerce, while any rock remaining unused could be deposited in a deep water reservoir.

A key challenge is the infrastructure both in the tunnel and the surrounding area, according to NCA’s Stad Ship Tunnel project manager Terje Andreassen,

“Because of the height, you have to do the drilling and blasting in several different levels, starting at the top with ordinary drill and blast – you drill horizontally and blast. When you’ve done the securing work, you start to move downwards. Then you do excavation the same as open mining – you drill vertically and blast.”

Access to different levels will be through specially constructed service tunnels or roads which could then be utilised as emergency evacuation routes. However, throughout construction, sections of rock will be left at both ends of the tunnel to mitigate water ingress. Post-completion, the remaining rock will be blasted out and both ends dredged to allow water through.

The studio looked to the peninsula’s characteristic stone walls to create a design that would provide a visual impact and also blend with its natural environment.

The entrance walls will be created using wire-cut and blasted stone while on its western side, an existing road will be rerouted over the tunnel on a new bridge that will offer an observation point for approaching ships. Lighting will be provided via LED hoses.

The Stad Tunnel is believed to be the world’s first full-scale ship tunnel.

RB Plant | Multi-Disciplinary Engineering Consultancy | Factory aerial view