The A24 Blankenburg connection: An innovative design concept for an immersed tunnel project in a busy port

• Alternative Contractor’s Design - Staggered construction of immersed tunnel on top of cut and cover tunnel. • Cross-section design with lateral prestressing for an immersed tunnel. • Permanent reinforced underwater concrete at 30 m depth. • Construction tunnel elements in ships dock. The A24 Blankenburg connection is a new three-lane highway in the Port of Rotterdam connecting two existing highways. The project incorporates a ground level subsurface tunnel of approximately 500 m (Holland Tunnel), an immersed tunnel of approximately 900 m (Maasdelta Tunnel), a fly-over connecting the A15 and a dive-under connecting the A20 and the widening of the existing A20 highway. Challenging to construct the connection is the location in the busiest part of the Port of Rotterdam, one of biggest ports in the world and therefore of great importance to the Dutch economy. The A24 Blankenburg connection is being constructed by the BAAK consortium (consisting of Ballast Nedam and DEME Group). The consortium developed a completely new innovative design concept for the immersed tunnel which embraces the minimization of hindrance both on water as well as on land. This paper will address the original plan, the tender design and some of the key elements of the design and construction of this project.