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Floating Concrete Giants: Inside Belgium’s Tunnel Mega-Project

*Recently, eight colossal concrete tunnel elements—each weighing around 60,000 tonnes—were floated out from a prefabrication dock in Zeebrugge. Source: Construction Review*

In an extraordinary display of modern geotechnical and civil engineering, Belgium’s 1.8-kilometre Scheldt Tunnel is taking shape beneath the mighty Scheldt River in Antwerp. As part of the transformative Oosterweel project, this tunnel is not only designed to close a crucial gap in the city’s ring road but to do so with a level of technical ambition rarely seen in submerged infrastructure. Recently, eight colossal concrete tunnel elements—each weighing around 60,000 tonnes—were floated out from a prefabrication dock in Zeebrugge. This marks a milestone in a construction sequence where each segment, precision-engineered to accommodate a subtle curvature beneath the riverbed, will travel over 100 kilometres by sea before being immersed into a pre-dug trench.

Engineering Feats Beneath the Scheldt

The Scheldt Tunnel’s construction embraces the “immersed tube” method—a masterstroke of gravity, buoyancy, and precision alignment. Once floated and transported, each sealed segment is carefully submerged and connected to preconstructed shore sections. To accommodate both vehicle and bicycle traffic, the tunnel will feature three lanes in each direction and a 6-meter-wide dedicated cycling tube. This intricate process, requiring the flooding of the construction dock with 800,000 cubic metres of water and complex underwater placement techniques, showcases the critical role of geotechnical planning, hydrodynamic analysis, and precision dredging.

To accommodate both vehicle and bicycle traffic, the tunnel will feature three lanes in each direction and a 6-meter-wide dedicated cycling tube. Source: Amusement logic

A Tunnel with a Curved Vision

What sets the Scheldt Tunnel apart is not only its sheer scale but the elegance of its engineering under constraint. Designed with a deliberate curve to preserve Antwerp’s natural riverbanks and reduce flood risk, the project integrates ecological sensitivity with infrastructural necessity. With phased openings expected through 2030, including a cycling tube anticipated by 2028, this engineering marvel stands as a blueprint for future urban infrastructure in tidal, densely built environments.

Check out the following video for more insights on the Europe’s $7BN Megaproject.