Project track replace­ment in the Lötschberg summit tunnel completed
Project track replace­ment in the Lötschberg summit tunnel completed

Project track replace­ment in the Lötschberg summit tunnel completed

ARGE Marti LBST has been working in the Lötschberg summit tunnel since 2018, re­placing the existing ballasted track with a slab track. The over-100-year-old, 14.6 km rail tunnel between Kandersteg and Goppenstein connects the cantons of Bern and Valais. It is the heart of Lötschberg mountain railway from Spiez to Brig. In August 2023, Marti in­stalled the last meters of track, then set and cast the golden crosstie as the symbolic con­clusion of the project.

The ballasted track from the 1970s in the Lötschberg summit tunnel had reached the end of its service life. ARGE Marti LBST was there­fore commis­sioned to re­place the old track with a new slab track. One particular challenge was that the track replace­ment had to be conduc­ted during on­going operations as full closure of the tunnel was not possible. To meet the challenge, logistical solutions and con­structions were de­veloped in the run-up to the project. In collaboration with Marti Technik, the team from Marti Tunnel Ltd. de­veloped an innovative transport system.

Custom-built solutions for an optimal construction process

To transport material in the con­struction phase, the tunneling crew installed a specially designed transport track with a monorail on the tunnel vault. Movable crane attach­ments on the monorail were then used to re­move the old track panels and lay the new ones. Ballast and concrete were trans­ported bet­ween the con­struction section and the work train via a mobile con­veyor belt system sus­pended from the monorail.

There were also five different train types used, all specially de­signed by Marti for this project: The drilling car was used to drill the anchors for the monorail on the tunnel vault. The track-laying train was used to remove the old track sections and install new ones. A ballast train trans­ported the ex­cavated ballast from the tunnel and the concreting train delivered fresh concrete to the tunnel for the new slab track. And finally, the supply train with emergency containers, toilets, stored materials, water treat­ment system and supply. The trains were driven by three of the company’s own locomotives.
A deceptively tricky project – by no means just «re­moving a bit of track ballast and then in­stalling some concrete.»
Simon Bertholet,
Project Manager Marti Tunnel AG

Intensive construction phases and tight spaces

BLS required the use of both tracks during the winter months, so the intensive con­struction phases for Marti were between Easter and December. The con­struction crews used the inter­vening period for main­tenance and pre­paratory work. During the entire con­struction period, the tunneling crews were con­fronted with ex­tremely tight and dangerous working con­ditions, with continuous rail traffic on the ad­jacent track. The safety of the crews was there­fore the utmost priority. Crews worked in three shifts, from Monday morning to Saturday morning. An in-depth look at the different stages and processes is presented in the project film Lötschberg summit tunnel – Installation of the slab track during operations.

Summer 2023 – the final meters of track are in place

On the night from the 15th to the 16th of August, Marti laid and cast the last tracks. The mile­stone was symbolically celebrated with the casting of the final golden cross­tie, and ultimately celebrated by those involved with a project-completion party at the installation site in Kandersteg. The team would later clear the tunnel and the installation site and hand the tunnel back over to BLS.