Semmering Base Tunnel
The Semmering Base Tunnel is one of the most important long-term, large-scale infrastructure projects in the Austrian and European high-capacity rail network. The purpose of the tunnel is to remedy a bottleneck along the Baltic-Adriatic Corridor and enable an attractive freight traffic route along the Austrian southern line.
The Semmering Base Tunnel decongests and complements the existing Ghega mountain section, which has reached its capacity limit with its 160 years of age. When the tunnel is completed in 2026, the travel time for passengers travelling from Vienna to Graz will be reduced by 30 minutes.
The tunnel itself runs from Gloggnitz to Murzzuschlag, will take 14 years to construct and is 27.3 km in length. Tackling an 8.4% gradient, the two parallel tunnel tubes with enable trains to travel up to 230 kph or carry up to 1,600 tonnes with only one locomotive.
As is to be expected of a project with such a significant timeframe, the tunnel is particularly complex. For geological and construction logistics, the work has been divided into three tunnel sections – Gloggnitz, Froschnitzgraben and Grautschenhof – and several contract sections. Intermediate access shafts will provide additional access to the tunnel to allow excavation to be carried outwards.
The entire project has been commissioned by ÖBB-Infrastruktur AG, who plan, develop, maintain and operate the entire ÖBB railway infrastructure.
Taking each section individually, Gloggnitz lies entirely in Lower Austria over a stretch of 7 km. Building work at this site has been in progress since July 2015 and the tunnel is being created entirely using digger and blasting procedures. ÖBB-Infrastruktur AG has commissioned a syndicate with Implenia, HOCHTIEF Infrastructure and Thyssen Schachtbau for the section.
Froschnitzgraben is the middle section and longest stretch of the Semmering Base tunnel. A 4 km stretch will be constructed by drill-and-blast in the direction of Murzzuschlag with approximately 9 km heading in the direction of Gloggnitz using two tunnel boring machines. Building on this site has been underway since January 2014.
Finally, the Grautschenhof section is about 7 km long and has been in progression since May 2015. The miners initially worked in two shafts down to a depth of 100 metres before excavations and blasting in each direction.
At peak times, taking all the tunnel building sites together, around 1200 people will be working directly on this project. A total of 4500 jobs have been created as a result of the project. As one of the most complex tunnel construction projects in Europe, the work has required a great deal of patience and innovative thinking. In order to implement the tunnel as quickly, efficiently and environmentally friendly as possible, long-term planning has been required.
When completed, the Semmering Base Tunnel will be a beacon of engineering ingenuity from which others will be able to draw inspiration. Visible for centuries to come, the tunnel will not only benefit the two largest cities in Austria but it will also be central to the development of European transit routes in neighbouring countries.