Dual-mode TBMs modernize Czech rail infrastructure 03 May 2018

Two single track 4km tunnels for a project to modernize the Czech railway line between Rokycany and Pilsen have been excavated by a convertible 9.8m diameter multi-mode TBM supplied by Herrenknecht. The resulting high speed rail link, built by contractor Metrostav, will connect the West Bohemian countryside to the capital Prague and thus to the European railway network.

Herrenknecht multi mode built two 4km rail tunnels

The TBM worked in closed EPB mode with screw conveyor muck removal for the first two thirds of the two tunnels through quartzite shale stone and clay. For the last third the TBM switched to open single-shield mode with belt conveyor removal to penetrate hard spilite rock. Each conversion was performed within two weeks inside the tunnels.

"For variable ground conditions along the tunnel alignment, a convertible multi-mode TBM is the best and most flexible solution. It can be run in different tunnelling modes and thus operate in changing geologies," said Korbinian Kröger, Herrenknecht Project Manager.

The cutting tools were changed from 18in disc for the first part of the drive to 19in for the second section of each drive as the larger disc diameter allowed higher contact pressure in the solid hard rock and longer running times.

Open single shield mode was used on hard rock

Advance rates of 38m a day were achieved

With small overburdens in parts, the TBM achieved weekly top advance rates of up to 182m. Herrenknecht also provided additional equipment, such as multi-service vehicles from subsidiary TMS, a cooling tower and belt conveyor systems.

The new high-speed rail link reduces the average travel time between Rokycany and Pilsen by around 10 minutes, and the capital city of Prague can be reached from Pilsen in less than one hour. As a result the region around Pilsen – with about 170,000 inhabitants the fourth largest city in the Czech Republic – will be better connected to the trans-European transport network.

The modernization project makes the railway journeys faster and also includes special safety features in the new tunnels such as fire protection solutions and escape routes.

Herrenknecht is also involved in other infrastructure development projects in Eastern Europe including the 10km long Slowacki Route in Gdansk, Poland and the road tunnel crossing under the Vistula River, and metro expansion projects in Moscow, Sofia and Warsaw.

Final breakthrough of the second tunnel occurred in October 2017 after 12 months tunnelling.