South of Basel, the railway lines Basel-Zurich, Basel-Luzern, Basel-Bern and the highly frequented exit from the rail marshaling yard Muttenz interconnect. For years, this bottleneck had been a challenge for the planning team and operations experts – with the even tighter timetable of the project “Rail 2000” it would no longer have been possible to take on this challenge. A double-track railway tunnel between Muttenz and Liestal is planned to relieve the situation. The geology of the Adler Tunnel: Jura slate consisting of greatly different formations with low rock strength and a pressure of up to 600 tonnes per square meter.
The Herrenknecht TBM, named “Atalanta”, which was the world’s largest Hard Rock TBM todate with a diameter of 12.58 meters, was planned to drive a 4.1-kilometer-long tunnel. Despite the impediments related to geology, performance rates were considerable: the two tunnelling teams and the maintenance team achieved best daily performances of 25 meters and best monthly performance rates of 495 meters within 23 workdays. In early 1998 breakthrough was achieved and the tunnel was put into operation in 2000.