High-impact operations in France’s oldest tunnel
In Rive-de-Gier (Loire), the Couzon Tunnel – recognised as France’s oldest railway tunnel – underwent modernisation during two weekends of intensive works, in order to minimise the impact on rail services. This complex project drew on the expertise of La Champenoise de Voies Ferrées (ETF) and LMTP (Sogea Environnement), subsidiaries of VINCI Construction.
Carrying out work on a historic structure – which is narrow and subject to significant technical constraints – requires meticulous organisation. Working round the clock, the teams took turns over the May Day and Whitsun weekends, enabling a total of 600 metres of track to be renewed.
A resumption of work tailored to the realities on the ground
An initial phase of works had been carried out in 2021 by another contractor on one of the tunnel’s two tracks. However, this work had been hampered by a major difficulty: the unexpected hardness of the track bed. As a result, only one track had been renewed.
The teams from Champenoise de Voies Ferrées and LMTP therefore resumed work on the project, rethinking their approach and adapting their methods and resources to best suit the actual conditions encountered on site.
La Champenoise carried out all the railway works: removal of the existing track, earthworks, complete renewal of the subgrade and re-laying of the track, thereby ensuring the long-term durability of the infrastructure. For its part, LMTP was responsible for a key element of the project: the construction of the central railway drainage system, which is essential for water drainage and the stability of the subgrade.
A project requiring a high degree of adaptability
During the works, the teams had to overcome a number of technical challenges. The uncertainty surrounding the presence of particularly hard areas within the railway platform, as well as a larger volume of excavated material than anticipated, meant that the working methods and resources deployed had to be constantly adapted.
Despite the specific constraints of working in a tunnel, the teams demonstrated responsiveness and expertise, enabling them to complete nearly 90 per cent of the planned length of the central drain, whilst ensuring that the track was renewed within the set timeframe.
This project demonstrates the ability of ETF and its partners to carry out work on heritage structures, whilst meeting the network’s modern requirements in terms of performance, safety and sustainability.