Innovation for enhanced safety and ergonomics in tunnels

Tunnel floor lining

The second team's first task is to prepare the lower third of the tunnel, the floor formwork. To do this, before the tool comes into action, our workers prepare and rework the ground by projecting mortar. Then, using the tool, they create a waterproofing layer with a minimum of three layers: a geotextile fabric and geogrid, a geomembrane, and a protective black. This is followed by reinforcement, to ensure even distribution of traction forces. Once this work is complete, the final step is to position the formwork to pour the concrete from the back of the machine. This finally forms the solid base of the tunnel floor.

The work steps described require considerable physical effort, as Alexander Heim points out: “For the waterproofing, we produce an extra-strong layer, 3 mm thick and 2 m wide.” The geotextile is delivered in huge rolls weighing around 150 kg each and must be installed around the entire circumference of the tunnel. The geotextile is bolted to the facing with a washer. The geomembrane is welded to the washers, and the strips are welded together. The protective black is then welded onto the geomembrane. Rolls and reinforcement are supplied from the front of the machine, using winches and jib cranes integrated into the machine for ease of handling.   

Reduce the risk of accidents

“In this kind of work, where heavy equipment is moved and installed, the risk of accidents is high,” explains Alexander Heim. “Our mission is clear: we are responsible for our employees and must ensure that they return home in good health in the evening. This is what prompted us to develop an innovative, customized tool for tunnel lining.”

To do this, a team including Florent Baulat, Senior Works Engineer, and Karine Puyjarinet, Site Environment Manager and Concrete Referent, began to define what such a machine should do. Seven criteria were defined to make work easier and more efficient: assembly and disassembly, accessibility, access to the machine, workstations, tool handling, maintenance and task automation. “In concrete application, the machine had to transport materials and equipment inside the tunnel and permit the team to carry out their work according to the most ergonomic standards possible,” explains Florent Baulat. “This means that, wherever possible, they should not move loads by hand, and that they should always have all auxiliary aids like lifting and support devices within reach.”

New development with Kern

In partnership with Kern Tunneltechnik in Switzerland and one of their plants in Slovenia, an innovative solution was developed over a 12-month period from existing components. On March 25, 2025, the machine began operating at the tunnel entrance and is now progressing in 10-meter steps towards the tunnel interior.  “The smile on the employees' faces when they use the machine's functions are impressive: the tools are adapted to the tasks required,” explains Florent Baulat. “It's always a source of pride to see a working machine transformed from a drawing on a blackboard. Kern's advanced engineering enabled us to design a custom machine. They were able to guide us through the design and assembly of the tool”. 

“It's important to invest in an ergonomic process when designing the tool, to adapt the working environment – tools, equipment, traffic, organization, etc. – to the user's needs, with the goal of mechanizing tasks as much as possible,” explains Karine Puyjarinet. “This enables us to check, as far as possible, in advance that the tool is working properly, and then adaptations are made in the factory during acceptance or on site during assembly.”