Future of Tunnel Construction:

BauBots drill ahead. fischer robots support the reinforcement of the Engelberg Tunnel in Leonberg

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Future of Tunnel Construction:
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Reinforcement of the Engelberg Tunnel in Leonberg

The Autobahn GmbH Southwest Branch is currently carrying out a comprehensive structural and operational reinforcement of the Engelberg Tunnel in Leonberg (Baden-Württemberg). Three fischer BauBots were used in the process. The construction robots drilled more than 9,000 holes with a diameter of 20 mm and a drilling depth of 240 mm at heights of up to 7.5 m fully automatically. This increased efficiency and precision in fastening tasks.

The Engelberg Tunnel is part of the important traffic artery of the federal motorway A81 and passes through the eponymous Engelberg north of the Leonberg Triangle. With around 120,000 vehicles daily, it is one of the busiest motorway tunnels in southern Germany. The two tunnel tubes are each 2,530 meters long and feature three lanes plus a hard shoulder in the west tube towards Karlsruhe/Munich, and also three lanes plus a hard shoulder in the east tube towards Heilbronn. The current tunnel was originally constructed from 1995 to 1999 as a replacement for the old Engelberg Tunnel from 1938.

Over the years, mountain pressure caused damage – approximately 180 m in the west tube and about 170 m in the east tube are affected. Geological challenges exist in the anhydrite rock, which swells upon contact with moisture, deforming the tunnel linings and endangering the structure. The complex reinforcement is carried out under ongoing traffic with all lanes maintained, thus in very confined space – made possible by a sophisticated construction site traffic concept. Closures occur exclusively during low-traffic periods. As part of the construction measure, the operational technology is completely renewed at the same time, while safety must still be guaranteed 100 percent. The comprehensive renovation began in April 2019, with completion planned for 2026. The client is the Federal Republic of Germany, represented by Autobahn GmbH, Southwest branch.

The measures to reinforce the tunnel inner linings in the anhydrite-damaged sections include: the installation of a reinforced concrete lining with steel beams for the static bracing of the vaults and the installation of an intermediate ceiling. Additionally, the roadway slab, which serves as transverse bracing, is reinforced. At the same time, the safety and operational technology is renewed along the entire tunnel length. 

Project Brief Engelberg Tunnel in Leonberg

Client:
Federal Republic of Germany, represented by Autobahn GmbH, Southwest Branch
Project duration:
Start April 2019 - planned completion 2026
Project scope:
Fully automatic drilling of 9,000 boreholes with a diameter of 20 mm and a drilling depth of 240 mm at a height of up to 7.5 m
Reason for the renovation:
Mountain pressure damage – approximately 180 m in the west tunnel and approximately 170 m in the east tunnel are affected

Innovative Construction Robotics by fischer in Action

On behalf of the renowned tunnel construction company Baresel, the project participants deployed three fischer BauBot construction robots. The robot-assisted high-precision drilling technology enabled fast, safe, and precise preparation of anchoring points – especially in hard-to-reach areas within the tunnel vault. The BauBots fully automatically created more than 9,000 hammer-drilled holes with a diameter of 20 mm and a drilling depth of 240 mm at heights of up to 7.5 m in concrete. 

The BauBot Services GmbH – the central contact point for planning and implementing fischer robotics applications on the construction site – coordinated and supervised the deployment of the construction robots – from planning through execution to documentation. 

fischer services ranged from creating the digital construction plan, which provided the BauBots with the exact drilling points, to on-site support of the execution by operators, up to successful completion. The integrated dust extraction of the robots ensured a clean, health-friendly working environment as well as the compliant installation of the fasteners in the cleaned drill holes. Drill bits and consumables were included in the service package. Additionally, spare robots, end effectors, and operators were available to prevent downtime. Each drilling operation, including relevant process parameters such as drilling depth, reinforcement hits, and other important details, was automatically documented – manual logs were not necessary. 
The deployment of our three fischer BauBots significantly contributed to increasing efficiency and improving quality in the renovation of the Engelberg Tunnel.
Emil Kral, Managing Director of BauBot Services GmbH
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