From BBT SE,

Brenner Base Tunnel reaches state border for the first time

Tunnel boring machine “Serena” reached its destination at the Brenner Pass after 14 km and 3.5 years of excavation works.

A small-scale celebration was held by the Brenner Base Tunnel company BBT SE to mark this historic milestone - together with guests invited from political as well as business spheres - when the excavation works reached the state border between Italy and Austria at the Brenner Pass, for the first time. The event took place in compliance with the strict COVID safety measures applicable at the present time.
On this occasion, the tunnel boring machine named "Serena" worked its way through the last centimetres of gneiss to complete its task and be the first to reach the Brenner border. At 14.30 pm the TBM was stopped after about 14 kilometres of successful excavation.

Quotes
BBT SE Board of Directors BBT SE CEOs Gilberto Cardola e Martin Gradnitzer:
"Today, TBM Serena has reached an important, symbolic destination: the Brenner. This is the first step in building a continuous tunnel linking Italy and Austria. Our greatest congratulations go to the TBM teams for this result, but we also wish to thank all the other tunnel workers, planners, engineers, geologists and BBT SE employees who work day after day to drive this project forward."

The journey of the tunnel boring machine (TBM) "Serena" began in May 2018. It was started in the exploratory tunnel of the Brenner Base Tunnel to excavate it on the Italian side (Alto Adige). The tunnel boring machine has now reached its destination at the state border, marking a major success for the bilateral infrastructure project. The fact that the rock at the base of the mountain is now uninterrupted all the way to the Brenner border symbolises the progress of the construction works for the railway tunnel. Moreover, two TBMs are also operating in the two main tunnel tubes above the newly excavated tunnel, which are working at full speed and can achieve almost 65% and 75% progress respectively.

The largest BBT construction site
The Mules construction lot, where the TBM "Serena" carried out its work, is the largest construction site of the BBT project in terms of kilometres of tunnel to be completed. About 65 km are being excavated here between Mezzaselva and the border at the Brenner Pass. The overall construction progress of this construction lot is also going well and 82% of it has already been completed. This section of the Brenner Base Tunnel includes approximately 800 employees as works here began in September 2016.

Key information on TBM "Serena"
This machine is a double shielded tunnel boring machine with a diameter of 6.85 m. It has been operational at the Mules construction lot since May 2018 and it excavated a total of 14.13 km of tunnel (exploratory tunnel section northwards) up to the Brenner border. Tubbing rings were used for the tunnel lining. This means that this "underground factory" with a driving power of 2,800 kW not only worked its way through the rock and excavated the exploratory tunnel with its cutting head, but it also used a trailing structure to move prefab concrete elements, known in technical jargon as "tubbing rings", as an inner shell in a single work sequence. To produce these concrete elements, the rock from the excavation is recycled sustainably. A tubbing ring consists of five standard tubbings, a keystone and two bottom tubbing segments (ground elements). TBM "Serena" almost 300 m long and weighs over 1,200 t.

https://www.bbt-se.com/en/information/news/detail/news/translate-to-en-brenner-basistunnel-erreicht-erstmals-staatsgrenze/