VirtuRail® – with an Autonomous Train into the Heart of the Tunnel
It’s a warm day in June 2018 in the Tyrolean Alps. But there is little evidence of this in the exploratory tunnel for the Brenner Base Tunnel. The shotcrete walls, illuminated by lamps, emit a pleasant coolness. The moisture of the mountain collects on the concrete floor. Two cones of light appear in the dark: “Christl”, a train pulling five wagons, passes by at about 20 km/h. Its destination is the tunnel boring machine (TBM), which it supplies with prefabricated concrete segments – so-called “Tübbings”. Thanks to the autonomous VirtuRail® system, Christl doesn’t need any rail tracks. This makes it a world-first, which adds another innovation to tunnelling at STRABAG.
Self-driving train on rubber tyres
Today, Business Unit Manager Christian Kaiser and TBM Site Manager Sebastian Grüllich look back with satisfaction on their work with Christl. Together with their team, they have implemented the drive for the 15 km long exploratory tunnel as well as the other 30 km long tunnels for the Tulfes-Pfons tunnel section. The Multi Service Vehicle (MSV) developed by the STRABAG experts together with partner companies played an important role in this.
“This is the first time that we used the approximately 55 m long, autonomous trains to provide uninterrupted supplies to the tunnel boring machine,” says Sebastian Grüllich. The vehicles supplied by logistics system specialist ROWA are rubber-tired – a practical approach that eliminates the need for track installation and operation.
Smart train system ensures new records
The five coupled wagons can transport 95 tons of material from the tunnel portal to the TBM without reloading. For comparison: standard MSVs achieve a maximum payload of 55 tons. “The trains contributed greatly to the world tunnel propulsion record of 61.04 m in 24 hours,” says Grüllich proudly. Another special achievement is its ability to overcome a 12 % slope over a distance of more than 2 km.
This was also a major goal behind the train’s development: the gradient made track-bound supply impossible. “The MSVs available on the market so far were out of the question due to their poor track keeping behaviour and their small size.
Safe through the mountain on a virtual track
A look back to June 2018: The starting station for Christl is at the tunnel portal. Here the team takes over the loading. Shotcrete, rock anchors, reinforcing mats, precast concrete segments – the train can carry them all. Then Christl begins its approximately one-hour trip to the tunnel boring machine. A steering wheel can`t be found in the driver’s cab. The VirtuRail® system from MobileTronics steers all 18 axles electronically so that they precisely follow a virtual track.
An additional driver assistance system automatically controls the first axle in the tunnel. And thanks to state-of-the-art navigation sensors, it is also capable of recognising possible obstacles. In this way, the train safely navigates the 90-degree bend at the end of the access tunnel.
Joystick instead of steering wheel in the operator cabin
In automatic mode, the driver merely controls the speed and uses a joystick to inform the system in which section of the tunnel the MSV is currently located.
“By the end of the project, 250,000 km of supply trips were successfully completed without a single accident,” says Christian Kaiser. Given the difficult conditions involved in underground transport, such as dust and moisture accumulation as well as mechanical strain on the equipment, that’s a noteworthy achievement.
“The use of a total of six MSVs also reduced the fuel consumption and exhaust emissions in the tunnel compared to other known supply concepts such as trucks,” summarises the Business Unit Manager. Besides the long trains Annemarie, Christl and Emma there were also the short trains Bärbel (self-rescue), Dorli (special transports) and Florian (external rescue fire brigade train) in operation.
World’s first autonomous supply run
Can the autonomous vehicle operate completely without a driver? The proof was provided by an impressive demonstration in December 2018. For the first fully autonomous supply run, the train technology was complemented with electronic “traffic signs” in the Brenner Base Tunnel. The MSV read its location from these signs and then defined the parameters for the next leg of the trip.
“I was surprised at how smoothly the driverless train moves. The MSV also interacted perfectly with the other vehicles operating in the tunnel,” Grüllich recalls. The experiment was a complete success and demonstrated the potential of autonomous operation. However, in the construction of the exploratory tunnel for the Brenner Base Tunnel, it didn’t go beyond this one demonstration. “Since the end of the drive at 15 km came in sight so quickly, the move to autonomous driving in full operation would not have paid off in time,” Grüllich explains.
Electric power as the next step
Nevertheless, this result plays a pioneering role for the future. “In the future, all material logistics could be carried out remotely via a central control station,” says Christian Kaiser. “That would be a huge opportunity, especially on larger construction sites with several tunnel boring machines.” The expert sees the next step in the development of Multi Service Vehicles in the conversion to an electric or hybrid driving system.
STRABAG and the Brenner Base Tunnel
The 45 km long Tulfes-Pfons section is a part of the construction project for the Brenner Base Tunnel (BBT), the longest underground railway in the world. Located at the northeast end of the tunnel, the section extends from the town of Tulfes to Pfons at the Brenner. In addition to the main tunnel and the connecting tunnel, the consortium of STRABAG and Salini-Impregilo is also building additional structures such as an exploratory tunnel and an emergency stop. The contract value for this project was around € 380 million.
More information: bbt-se.com
Christl has now reached the trailer ofthe tunnel boring machine. Here the vehicle has to enter exactly in the middle. Within 30 minutes, the team then unloads the heavy tunnel segments, using cranes. The empty shotcrete buckets are moved back into the wagons. Christl returns to the site mobilisation area. The next round can start – and soon, the next tunnel project.