Gotthard Road Tunnel Second Tube: TBM Set To Resume Operations in the South in Spring 2026
Excavation work on the second tube of the Gotthard Road Tunnel has been underway since 14 February 2025. On the north side, mechanised tunnelling is progressing according to plan. The TBM has completed a total of 2.5 km of tunnelling there; 250 m were excavated in October. The “Mesozoic” fault zone in the northern half of the tunnel – around 4 km from the tunnel portal – was accessed in parallel with TBM tunnelling and excavated using conventional methods. This work was completed in September. Therefore, the risks for the main drive on the northern side were significantly reduced as planned.
Heavily fractured, partially loose rock and cavities are currently impeding the southern TBM drive in the second tube of the Gotthard Road Tunnel. Since the end of October 2025, around 500 metres of tunnel are being conventionally excavated there using the drill and blast method (partial excavation, crown only)
Credit/Quelle: ASTRA
Blasting Towards the TBM Paulina
While the advance in the north is proceeding on schedule, the TBM Paulina on the south side had to be stopped on 23 June 2025 after about 190 m. Severely fractured, partially loose rock and cavities prevented safe TBM advance and could have damaged the machine.
Credit/Quelle: ASTRA
Credit/Quelle: ASTRA
The Swiss Federal Roads Office (FEDRO) therefore decided to excavate the remaining section of the complex Tremola geology, approximately 500 m in length, using conventional blasting (partial excavation, crown only). To this end, a connecting tunnel with a length of 250 m was created from the south access tunnel to the level of the second tube using drilling and blasting. This was completed at the end of October.
Since then, counter-advance has been underway to the south in the direction of the TBM. Around 50 m had been excavated by the end of November 2025; a total of around 250 m is required before the TBM is reached. At the same time, conventional advance is also underway to the north so that the TBM can be reused there in solid rock from tunnel metre 740 in spring 2026.
Work in the “Guspis” Fault Zone Is Progressing Well
The remaining work on the south side is proceeding according to plan. The “Guspis” fault zone – around 4 km from the tunnel portal – has been excavated up to 58% of the way. This also significantly reduces the risks for the main excavation from the south. In Airolo, the first elements of the Valnit bridge are also visible. The approximately 250 m long bridge will span a reservoir, among other things.
Impact on Schedule and Cost
As things stand at present, the adjustments will lead to a delay of around six to eight months and additional direct cost of around 15 to 20 million Swiss francs. A reserve for such risks is provided for in the project budget and construction programme.
In order to be able to absorb the impact if necessary, FEDRO is considering, among other things, three-shift operation seven days a week, bringing forward further work or extending the drive from the north. Such measures could speed up construction if necessary, but would themselves incur cost. It is therefore intended to carefully clarify which measures might be required. The aim is to mitigate the risk that has arisen in the southern tunnel as far as possible so that the planned overall budget and the overall construction programme can be adhered to.
