Motorway A81, Engelberg Base Tunnel

Leonberg, Germany
Leonberg, Germany
Regional Council Stuttgart
Planning period
01/2017 - 12/2018; 06/2019 - 05/2022
Total length
west tube (direction Singen) ca. 2,530 m; east tube (direction Würzburg) ca. 2,520 m
overall width
16.80 m
height clearance
8.10 m
number of tubes
Joint venture
SSF Ingenieure AG/Amberg Engineering AG
(HOAI 2013) Project planning of engineering structures §41ff / Lph 5 + 6 (final design, preparation of tenders); partial additions Lph 2 + 3 (preliminary and draft design); Structural engineering §49ff / Lph 4 + 5 (approval and final design) of regular blocks (reference design), Lph 5 (final design) of 6 special blocks (reference design), Lph 6 (preparation of tenders); Technical equipment §53ff / Lph 5+6 (final design, preparation of tenders) + special services; Additional BIM

The Engelberg Base Tunnel (EBT) near Leonberg is part of federal motorway A81 and is located directly north of intersection Leonberg near Stuttgart. The tunnel is used daily by 110,000 vehicles and is essential for the accessibility of the metropolitan area Stuttgart.

The Engelberg Base Tunnel had been built by underground excavation between 1995 and 1999 as two-tube tunnel with a length of around 2500 metres.

After almost 20 years of operation, both tunnel tubes show significant damages on a length of around 180 metres at the inner shell and the slotted channels in form of deformation in the area of the anhydrite rock. Those damages require a comprehensive strengthening of the inner shell, following the resistance principle as steel/steel composite structure with additional inner shell.

The strengthening of the Engelberg Base Tunnel also comprises a comprehensive optimisation and complementation of the operational equipment throughout the whole tunnel to adapt it to the state of the art as per RABT 2016 (German guidelines for the equipping and operation of road tunnels).


- modernisation and retrofitting during maintained traffic

- traffic management for construction phases

- „round the clock“ construction

Additional BIM:   

- adaptation of 2D data to 3D-Revit data /

- rendering as BIM model/visualisation

- complexity of structural strengthening

- detailed design of pivoting bearings / spherical bearing / ridge support, etc.

- BIM data use for adaptation of virtual reality “tunnel accessibility”

Interactive model of Engelberg Base Tunnel