Tubbing ring production in the BBT project: a model of environmental sustainability

Tubbing rings are precast concrete elements that form the final lining of the tunnels. Environmentally sustainable production processes were chosen in order to minimise impacts on the environment and the local population in the project area.

Tubbing rings are precast concrete elements that form the primary lining as well as the final lining in the construction of the tunnel. In the main tunnels of the BBT one complete ring consists of 7 elements and a base arch. The tubbing rings in the exploratory tunnel, on the other hand, have six precast elements and two base arches. An ordinary tubbing element (for the main tunnel lining) weighs about 9 tons, a key segment about 3 tons and a base arch about 17 tons. The tubbing rings in the exploratory tunnel weigh about half as much as those needed to line the main tunnels.

But how are the ring elements produced? Giorgio Malucelli, Operations Manager in the construction lot "H61 Mules 2-3", tells us about it: "The tubbing rings for the Mules construction lot are produced at the prefabrication plant Hinterrigger. The aggregates required for the production of concrete come from the tunnel excavations and reach Hinterrigger - to a very large extent - via conveyor belts that run from the excavation fronts inside the site areas to the prefabrication plant. After curing, the tubbing rings are transported by rail convoys to the TBM that will then complete the lining of the tunnel. Each rail convoy can transport up to 2 rings, and therefore 16 elements".

An efficient process that allows the re-use of around 30% of the excavated material for lining tunnels. This eliminates the need to source from off-site quarries, reducing the number of road transports during the supply phase, as well as reducing the final volume of material for the final disposal sites.

What about Austria? In the other tubbing ring factory in the Ahrental project area, the production of the segments directly on the construction site eliminates the need for around 27,000 truck transports.

In the H53 Pfons-Brenner construction lot, it was not possible to produce the tubbing rings directly on site due to the limited space available. However, transporting the tubbing rings by rail will avoid around 40,000 lorry transports, thus minimising the environmental impact. In the last few days, the first tubbing rings have arrived on the construction site.

Reducing travel times and promoting sustainable mobility, while protecting natural habitats in the project area during construction: the Brenner Base Tunnel project is about all this and much more.