Tunnel boring machine (TBM) manufacturer Herrenknecht has said that the TBM driving the second tube of the Bossler Tunnel on the Stuttgart-Wendlingen-Ulm railway line has achieved breakthrough.
Arge ATA Albaufstieg, formed by Porr Deutschland, G Hinteregger & Söhne Baugesellschaft, Östu-Stettin Hoch-und Tiefbau and Swietelsky Baugesellschaft, started work on the second bore in April last year.
The earth pressure balance TBM successfully completed the first tunnel drive, which is parallel to the second, in November 2016.
The TBM was used to drive more of the tunnels than previously planned. The original concept was for 2.8km of the tunnel to be driven by TBM but ground conditions turned out to be more favourable than expected and the TBM was used to drive 7.8km of the first bore and 8.8km on the second, which is almost the full length of the tunnel.
In total the TBM has drive 18km of tunnel through sandstone, limestone and claystone rock.
Tunnel drives of up to 38m per day were achieved at the height of the work.
The tunnel on the new rail line is expected to become operational in 2022 and will halve time on the Stuttgart to Ulm route.