PROJEKTE

The major construction project, the Altona Cover (Deckel Altona), over the A7 federal motorway in Hamburg, sets new standards for urban integration and environmental protection. This 2.2-kilometer-long cut-and-cover tunnel structure, built north of the Elbe Tunnel, not only gains the city 190,000 m² of new public space but also delivers a significant increase in peace and improved air quality for residents.

The ARGE Deckel Altona consortium (Implenia AG and Hochtief AG) is realizing the shell construction over approximately eight years. The structure requires an impressive 270,000 m³ of concrete – equivalent to over 38,000 mixer truckloads.

💡 The Challenge: Securely Sealing the Tunnel Roof

The tunnel roof, the actual “cover,” is dimensioned with a thickness of 1.00 to 1.30 meters. It must not only bear its own weight but also the load of the up to 1.20 meters of backfilled, root-penetrable soil placed on top of it.

The roof is constructed in concreting sections of approximately 700 m³ each, using a tunnel formwork carriage (traveller). The formwork is anchored back into the previously concreted section using climbing cones with $26.5 \text{ mm}$ Dywidag threads.

After the formwork is removed, the remaining conical opening, located in an “overhead” position, must be securely and permanently sealed. Since reliable setting of conventional adhesive systems or grouting could not be guaranteed in this overhead application, an innovative solution was required.

🔒 The Solution: The MARO Anchor Plug (Ankerkegel)

Our proposal – the MARO Anchor Plug – was the convincing answer:

• Immediate Mechanical Lock: The plug consists of a high-quality concrete cone with an exactly centered threaded sleeve embedded within it. This sleeve engages the permanent, lost-in-place tension rod (Ankerstab), creating an immediate and firm mechanical connection between the plug and the rod.
• Fast Installation: The plug is fully screwed into place with just a few turns.
• Reliable Bonding: The primary safety mechanism—a two-component adhesive system—is applied both inside the sleeve and on the rim of the cone. The secured position provided by the sleeve ensures the reliable setting of the adhesive.
• Tested Quality: Pull-off adhesion tests on the mechanically fixed plug (without adhesive) already measured values between 1.472 N/mm² and 1.792 N/mm².

In the first construction section, 700 MARO Anchor Plugs have already been successfully installed. Another 700 plugs will be used in the subsequent phases.

This proven solution can be offered for all appropriately sized cones that need to be screwed onto a lost-in-place anchor rod (e.g., steel/plastic cones, universal cones, and climbing cones).

Thank you to the construction management of the ARGE Deckel Altona for the excellent cooperation and the opportunity to document the installation of this innovative product.