The Gotthard Tunnel: ten years in service without a replacement

ISSUE

• On a 57 km ballastless track carrying up to 325 trains a day, each elastomeric component is subjected to some of the highest levels of vibration and dynamic loading in the world: a standard component would deteriorate rapidly under such conditions, which would necessitate major replacement programmes in a tunnel that is difficult to access
• Electrical insulation between the sleepers and the concrete slab is critical: without it, stray currents spread, damaging the infrastructure and disrupting signalling, with a direct impact on the safety and availability of the line
• In an underground environment at depths of up to 2,300 metres beneath the massif, vibrations transmitted to the rock and structure-borne noise must be attenuated: otherwise, mechanical fatigue in the structure will increase and acoustic comfort will deteriorate
• Any maintenance work on a deep single-tube tunnel involves infrequent and costly maintenance windows: a component that needs replacing too soon has an impact on the infrastructure’s operational availability, not just on its maintenance budget

BORFLEX SOLUTIONS

• An integrated system comprising an elastomer insole and a microcellular rubber sole with calibrated static and dynamic properties; a technology developed and refined since 1978, designed to withstand extreme loads
• Electrical insulation integrated into the sleeve, preventing the spread of stray currents between the cross-member and the slab without the need for any additional components
• Design using finite element method (FEM) simulation and mechanical qualification on an MTS Landmark hydraulic test bench, validating fatigue performance prior to industrial deployment
• Supply of 212,000 track pads for 57 km of track, delivered between 2013 and 2016, with IRIS and ISO 9001 certification, and compliance with REACH, RoHS and Euroclasses NF EN 13501-1

WHAT IT HAS ACHIEVED

Ten years after their installation, the 212,000 BORFLEX elastomeric bearings are still in service at the Gotthard Tunnel without having needed to be replaced, whilst the infrastructure now handles traffic of up to 325 trains a day at a depth of 2,300 metres.

On this type of infrastructure, the actual service life of an elastomeric component is the decisive factor: premature replacement not only puts a strain on the budget, but also takes up maintenance slots, thereby limiting the line’s commercial availability. The experience gained on the Saint-Gothard project positions BORFLEX as a qualified supplier for major construction projects using two-piece sleepers with elastomeric pads.

Ten years of continuous operation without replacement represents the most rigorous industrial validation test there is for a railway elastomer component. Our complete mastery of the entire process – from compound formulation and finite element simulation to mechanical qualification on the MTS Landmark test rig and mass production – constitutes our decisive competitive advantage.

Thierry Germe, KAM Railway, BORFLEX Group