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Craeybeckx Tunnel - Ventilation survey

The challenge

The challenge in designing the longitudinal ventilation in this tunnel was taking into account the specific framework conditions pertaining to the situation.

  • For example, the existing geometry varied in cross section, so it was difficult coming to a decision about the positioning and type of boosters,
  • plus, life cycle costs and ease of maintenance also needed to be considered,
  • and, where possible, avoiding the excess pressure installation in the 31 emergency exits.


1D analyses were used to:

  • Predict the flow profiles under different framework conditions in terms of boosters.
  • A ventilation strategy for certain cases was determined, with different battery boosters activated according to the position of the flashpoints.
  • By ensuring a constant lower pressure in the tunnel shaft, we were able to demonstrate how the excess pressure installation was unnecessary.
  • We also carried out sensitivity analyses into wind effect, traffic and fire size.

A 3D analysis was used to

  • validate the final design for the three fire scenarios.
  • It was demonstrated that the new longitudinal ventilation system:
    • Helped to achieve a high speed to limit the propagation of smoke upstream
    • Helped to maintain a lower pressure throughout the majority of the tunnel


the innovative nature of this survey led to submission of a paper to the renowned BHR International Symposium on Aerodynamics, Ventilation Fire in Tunnels.

The results of the survey will be presented in Lyon, France on 13 - 15 September 2017.

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De klant vertelt

Fire tests in the Craeybeckx Tunnel indicated that the existing ventilation system was no longer up to date. FESG carried out numerical simulations before the fire tests, and the results corresponded well with the tests, bolstering confidence in the models. When it came upgrading the ventilation system, I considered ease of maintenance and life cycle costs to be important factors. FESG was involved from the very outset, and produced a design that was customised to the objectives. It was a seamless collaboration with positive results. A satisfied client.

Jef Vercammen (Agency for Roads and Traffic )