Alte Mainzer Tunnel Mainz

Space for passing trains

To prepare the Alte Mainzer Tunnel - the "Old Tunnel" of Mainz, first opened in 1884 for modern train service, a cross-section of two segments left after a partial opening in 1924 needed to be expanded by 1.5 metres. Due to the enlarged distance between railway tracks, passing of fast trains (ICE) is now possible.

The project building contractors intended to secure the excavation despite the the initial tendering requirements. KREBS+KIEFER evaluated the alternative design plan for the tunnel from a structural and constructional perspective, and judged the plan favourably. To prepare for tunnelling, the surrounding loose rock from the existing vault was hardened by injections. This made driving through the deformation-sensitive tertiary rock stratum of the Mainz Basin possible, without buildings and facilities above-ground taking on damage. Because of the groundwater pressure—the ground water table lies in the development area between the upper edge of the rails and the tunnel roof—and foreign water that occurred in patches, the widened tunnel was sheathed in a water pressure tight inner shell, made of concrete impermeable to water.


  • Technical verification
  • Site supervision
  • Prüfingenieure