For the first time a railway tunnel in Norway was being driven with a TBM. A Gripper TBM from Herrenknecht excavated the 6.9 kilometers of the Ulriken Tunnel for the expansion of the previously single-track connection between Bergen and Arna to double track. Because the new tunnel was built at a distance of only 30 meters from the existing tunnel, mechanized tunnelling was given preference over drilling and blasting.
Due to changes in the construction processes the TBM had to be assembled in Arna outside the portal of the approach tunnel. In cooperation with the joint venture contractor, Herrenknecht developed a special walking mechanism for the cutterhead, with which the assembled back-up is pulled along in two meter steps. Herrenknecht personnel supported the customer throughout the assembly process.
For the tunnelling in extremely hard gneiss and with an overburden of upt o 600 meters Herrenknecht equipped the Gripper TBM with a total of 62 19 inch disc cutters.
In December 2015 the machine was christened “Ulrikke” and then began the drive. As soon as early April 2016 the jobsite reported average tunnelling rates of 18 meters per day. On August 29, 2017, the team on the Herrenknecht machine drilled through the last meters of rock – breakthrough was achieved after only approx. 21 months and best weekly performances of up to 169 meters.