When a train fire caused severe damage over a 760 m length of the Channel Tunnel, urgent concrete repairs were necessary. Trains were restricted to a single track and Eurotunnel wanted full operation to be restored in time for the UK school holidays in February.

As well as inflicting extensive damage to the concrete lining of the tunnel, the fire destroyed rails, catenaries, electrical lines and cooling equipment over the same distance, all of which had to be replaced.

  • Name of the owner
    Eurotunnel
  • Delivery date of the project
    February 2009
  • Partners of the project
    Main contractor: Vinci Energies / Eurovia Travaux Ferroviaires / Freyssinet consortium
    Designer: Setec TPI

Freyssinet’s experience has been key

Freyssinet’s experience of carrying out repairs after a similar fire in 1996 was central to the team’s ability to respond and mobilise rapidly and to understand the challenges of the task ahead. They could predict the type of damage that would need addressing, and the access and logistical challenges that they would face, without even visiting the tunnel.

Building on this knowledge, Freyssinet proposed a programme of works by a consortium that could complete all the repairs within a single contract, rather than a series of follow-on contracts that carried the risk of further delays. A price estimate was compiled within a matter of days, and a schedule of just four months was proposed to carry out the repairs and fully reopen the tunnel by 12th February as required. Eurotunnel signed a contract with Freyssinet to manage the full programme of works little more than a month after the fire had taken place.

Channel tunnel engineers
Channel tunnel scaffolding

Custom-designed 550 m-long scaffolding structure

One of the critical obstacles was to provide access to the full height of the tunnel lining to allow repairs to the concrete. On the previous contract this work was carried out from a train, but it made it physically challenging for the operatives to access all areas that needed attention.  To address this, a custom-designed 550 m-long scaffolding structure with a number of levels was erected to provide direct access around the full circumference. More than 100 staff were able to work on this equipment at the same time, carrying out manual preparation of the tunnel surface, fixing rebar, shotcreting and repairing the electrical services. A temporary 650 m-long track was built using 3,600 t of ballast and 2,500 fire-retardant oak ties from which hydrodemolition robots, forklifts and other equipment could be operated and to provide access to the scaffolding for operatives.

A challenging operation planning

Logistics and planning of the operation presented by far the biggest challenge to the success of the contract. The need to mobilise 400 staff very quickly, for example, and the speed with which materials and supplies had to be ordered and equipment obtained even before the full extent of the damage could be surveyed. With a single entrance and an 11 km-long journey to the site, control of deliveries to and from the workface was a full-time job and in the final weeks of work had to be managed on an hourly schedule.

Despite such restrictions, Freyssinet successfully completed the entire contract two weeks ahead of the holiday deadline, allowing the tunnel to fully reopen in time for the first peak travel season of the year.

 

  • 400
    Depth of damage to concrete (mm)
  • 12,600
    Area of concrete repair required (m2)
  • 1,072
    Number of anchor bolts installed
  • 4,000
    Amount of concrete sprayed in 32 days (tons)

I had the opportunity to work on the repairs after the 2008 fire. We spent five months together in a community of work and goals that I had never experienced before – or have since – with the owner, the engineer, and Freyssinet. We were obsessed with our aim of delivering the repaired tunnel faster than anyone imagined possible; which we did!

Michel Kahan -  
Setec group, Chairman & CEO

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