Construction access shaft of the Semmering-Basistunnel at the Zwischenangriff Grautschenhof, Spital am Semmering, part of the westernmost tunnel section.
The Zwischenangriff Grautschenhof at Spital am Semmering is the intermediate attack point of the third and final construction section of the 27.3-kilometre Semmering-Basistunnel railway tunnel being built by ÖBB-Infrastruktur AG. This 7-kilometre section connects the Fröschnitzgraben section with the western portal at Mürzzuschlag. The Grautschenhof site is located between Spital am Semmering and Mürzzuschlag in Styria.
Preliminary works began in May 2016 and shaft sinking commenced from September 2016. Two access shafts of approximately 100 metres depth were sunk at this site; tunnelling works were formally launched on 30 June 2017. The contract was awarded to a joint venture (ARGE) of Marti GmbH Österreich and Marti Tunnel AG, with a construction value of approximately 301 million euros.
Tunnel driving on the Grautschenhof section was completed in two stages: the westward drive towards Mürzzuschlag was finished in August 2023, and the final breakthrough of the entire Semmering-Basistunnel was achieved on 29 November 2024. The tunnel is scheduled to open at the December 2029 timetable change.
The Zwischenangriff Grautschenhof is the intermediate attack point for the westernmost of the three construction sections of the Semmering-Basistunnel — Baulos SBT3.1 (Tunnel Grautschenhof). The Semmering-Basistunnel is a 27.3-kilometre twin-tube railway tunnel running between Gloggnitz in Lower Austria and Mürzzuschlag in Styria, forming part of the Baltic-Adriatic Corridor of the trans-European rail network. The project is the largest construction project of the Austrian Federal Railways (ÖBB).
The Grautschenhof section is approximately 7 kilometres long and runs between the area of Mürzzuschlag-Ost/Grautschenhof on the western side and the junction with the Fröschnitzgraben section on the eastern side. The tunnel route at this western end descends northwestward from the Fischbacher Alpen towards the Mürz valley, crossing beneath the valley floor, the Semmering Schnellstraße, and the existing Semmeringbahn mainline before emerging east of Mürzzuschlag station.
ÖBB-Infrastruktur AG awarded the contract for Baulos SBT3.1 to a joint venture (ARGE) of Marti GmbH Österreich (Graz) and Marti Tunnel AG (Moosseedorf, Switzerland), with Marti GmbH Österreich serving as technical lead. The contract value was approximately 301 million euros. Construction works began in May 2016, initially with preliminary works including noise protection walls and water treatment infrastructure. Shaft sinking at the Grautschenhof site began in September 2016. Two access shafts of approximately 100 metres depth were sunk at the site. Tunnel driving was formally launched on 30 June 2017.
Excavation at the Grautschenhof section was carried out by conventional drill-and-blast methods (Neue Österreichische Tunnelbaumethode) in both directions from the intermediate attack point. A public observation platform — the "Infoblick" — was opened at the site during the construction period to allow members of the public to follow progress on the construction site from approximately 10 metres above ground level.
In 2018 a significant fraud case was uncovered at the Grautschenhof site: the chief purchasing officer of the construction consortium was found to have diverted approximately 300,000 litres of diesel fuel and materials valued at over two million euros — including concrete, steel, and bricks — for resale. Criminal proceedings were opened against eight suspects for fraud and breach of trust by the Staatsanwaltschaft Leoben.
Tunnel driving in the eastward direction from Grautschenhof was completed in the first half of 2023, creating a connection with the Fröschnitzgraben section. The westward drive towards Mürzzuschlag was completed in August 2023. The final breakthrough of the entire Semmering-Basistunnel was achieved on 29 November 2024. The tunnel, including the Grautschenhof section, is scheduled to open with the December 2029 timetable change.