A convertible Herrenknecht multi-mode tunnel boring machine (Ø 9,890 mm) was used to modernize the Czech railway line between Rokycany and Pilsen. The machine excavated two tunnels, each about 4 km long. Because of the heterogeneous soil conditions, the TBM initially worked in EPB mode, then on the last third in open single-shield mode.
With the expansion of the railway line as a high-speed rail link, the Czech railway network is being modernized. The line in the western part of the Czech Republic is part of the railway corridor linking Pilsen to Prague and thus to the European railway network. Over a distance of 4150 m it consists of two single-track tunnel tubes. The tubes were built by the Czech contractor Metrostav. For the first time in Eastern Europe, a convertible multi-mode TBM, specifically designed and manufactured by Herrenknecht at its Schwanau plant, was used. The multi-mode TBM built two-thirds of the two tunnels through quartzite shale stone and clay soils in closed EPB mode with screw conveyor muck removal. On the last 1.1 km of each route the machine S-799 had to penetrate hard spilite rock, for which it was converted inside the tunnel to open single-shield mode with belt conveyor removal within two weeks.