The geology continues to cause problems for the tunnel builders at Semmering. As the ÖBB announced on Friday, the 27-kilometer-long rail tunnel between Styria and Lower Austria should therefore be put into operation a year later, in December 2029. Construction costs also amount to almost four billion euros.
The seemingly never-ending story of the Semming Base Tunnel continues. After decades of political debate and some realignments, the big construction site started in 2012. But the mountain is proving difficult to overcome.
Especially a fracture zone in the Grassberg when driving in the direction of Gloggnitz (Lower Austria) is difficult. “Unfortunately, the prediction that the special measures in the Grassberg area that were decided and then implemented in 2021 would completely solve the technical and geological challenges has not been fulfilled,” ÖBB said on Friday.
Due to the “extremely complicated mountain structure” with completely different rock layers (hard, soft, aquifer, dry), the work will take several months longer and the opening of the tunnel will therefore be postponed until the 2029/30 timetable change. The so-called grouting measures in this section are extended “until a stable crossing of the fracture zone can be safely carried out using excavators and blasting”.
Construction costs rise to almost four billion euros
Construction costs are also rising sharply. The current extreme cost increases for building materials and energy also play a major role. According to ÖBB, the estimated total costs will increase by EUR 360 million to approximately EUR 3.9 billion.
Big head machines are done working
However, the Federal Railways also announce positive things: about 23 of the total 27.3 kilometers of the two-tube tunnel has already been dug. The two large tunnel machines made faster than expected progress and have already completed their work.
Source: Krone

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