Semmering base tunnel

The New Semmering Base Tunnel is one of the most important infrastructural projects in the heart of Europe. It is a twin-bore tunnel, 27.3-kilometer-long, with an emergency stop in the middle. The tunnel will connect Gloggnitz with Mürzzuschlag, Styria, Austria and will be part of the Baltic-Adriatic railway corridor. It is considered to be one of the most important large-scale infrastructure projects in Central Europe.

Fig.1 Layout of the Semmering Base Tunnel

The Semmering rail line is the first railway to cross the Alps, built between 1848 and 1854, listed as a historic monument and nominated as the World Heritage Site by UNESCO. A total of 70,000 goods and passenger trains run through the mountainous route each year, making it one of the busiest routes in Austria. The new Semmering Base tunnel will comprise twin parallel bores, each with a 10m diameter, separated by up to 70m and connected at maximum intervals of 500m by cross-passages. The tunnel will enable trains to travel at a speed of 250km/h and will reduce the travel time between Vienna and Graz by 30min and it is considered to be is one of the key projects in the expansion and upgrading of Austria's southern railway. Additionally, the B27 road will be relocated and flood protection measures will be taken along the Schwarza River as part of the project.

Site preparation and other works at the Semmering base tunnel began in 2012. A ground-breaking ceremony was held at Gloggnitz on April 25, 2012 to officially launch preliminary construction works for the 27·3 km Semmering Base Tunnel. Construction work started in January 2014 and is expected to be completed in 2024. Once completed, this tunnel will become one of the world's longest railway tunnels.

Fig.2 Location of the Semmering Base Tunnel on the rail line between Vienna and Graz in Austria.

The Semmering Base Tunnel is one of the most important long-term large-scale infrastructure projects in the Austrian and European high-capacity route network. Through this tunnel, a sustainable investment is being made in both Austrian and international rail transport. In the long-term, the Semmering Base Tunnel will not only relieve the ‘Semmering-Bahn’ UNESCO World Heritage Site, but also enable a faster, more attractive freight and passenger transport service – powerful and future-oriented.

Austrian Federal Railways (ÖBB) was commissioned to develop the tunnel with an estimated investment of €3.3bn. The contract for the construction of the 13km-long central section of the Semmering base tunnel was awarded to the consortium of Implenia and Swietelsky. The value of the contact is approximately €623m. The work by Implenia and Swietelsky on the central section started in summer 2015 and expected to be finalized by 2024.

This major project includes also other companies: Amberg Engineering was awarded the contract for conducting tunnel excavation works, while Strabag was engaged to conduct drilling, ÖBB contracted the Werner Consult and Witrisal consortium to conduct the route planning for the tunnel, Gruner was engaged to provide design service for the new twin-tube tunnels, INSITU Geotechnics engaged to supply soil mechanical and geotechnical consulting services for the Fröschnitzgraben and Grautschenhof intermediate sites and BGG Consult engaged to provide geotechnical and hydrogeological consulting services during tendering and construction phases.

Works on the third and last tunnel section, the south-western section (Baulos Grautschenhof) have started in June, 2016. Thus the Semmering Base Tunnel is fully in construction now. For the approximately 27 kilometers rail tunnel, a total of 62 tunnel kilometers will be digged – in addition to the two railway tunnels, 8 kilometers of access tunnels, more connecting tunnels and shafts. In the south-western section Grautschenhof (municipality of Spital / Semmerig) the construction of the two shafts will start this year. The tunnel is being excavated from multiple sites, through the mountain at Gloggnitz, working at Göstritz on the construction of a 1km-long tunnel to access a large construction site from where work will begin in 2019 on the railway tunnels. The construction from various access points saves time and helps to overcome the rocks from several sides.

Plan is to start further work in 2017 on the running tunnels from two other locations - Fröschnitzgraben and Grautschenhof - using a mixture of techniques including boring and blasting. From 2017 the actual rail tunnel tubes will be built there – some with a large tunnel dredging machine, partly by dredging and blasting. Construction of a new station tunnel portal at Mürzzuschlag will start in 2019. All in all, the plan is to open the tunnel for traffic in 2024, and that will reduce the Vienna – Graz journey time from 2h 30min to around two hours.

author: Sanela Kovačević, 23.06.2016.