On behalf of Heathrow Airport Ltd, Atkins has assessed options for the upgrade of fire & life safety systems in two major road tunnels at Heathrow Airport. We adopted a performance-based design approach with detailed risk analysis to determine the optimum tunnel safety upgrade provisions for fire protection, evacuation and ventilation systems.
Applying ‘as low as reasonably practicable’ (ALARP) principles with a combination of qualitative assessment, stakeholder engagement and more focused quantitative risk analysis, Atkins assessed the risk to life safety, structural integrity and business operations associated with potential tunnel fires. Targeted improvements to the fire protection, ventilation and evacuation systems were recommended based on their value contribution.
Passive fire protection can offer cost benefits due to reduced structural damage and repair time in the case of vehicle fires. We quantified the potential benefits of sprayed and board linings for a variety of fire scenarios in the Heathrow tunnels.
Active fire suppression systems are a relatively new technology for road tunnels, with no tunnel-specific design standards. We engaged with specialist suppliers and manufacturers; analysed data from recent full scale fire test programmes; conducted independent analysis and developed design and performance specification for an effective, reliable fixed fire fighting system (FFFS).
Ventilation systems play a key role in minimising risk to life safety in tunnels. In addition to the maintenance of air quality during normal tunnel operation, the ventilation system is used to direct smoke and hot gases away from tunnel users in the event of a fire. We developed the design for a longitudinal ventilation system in one tunnel and a semi-transverse system in a second tunnel to provide effective improvements.
For the longitudinal system, we developed a unique and innovative aerodynamic jet fan deflector system which was trialed in the tunnel. Results demonstrated significant improvements in ventilation efficiency with simple deflector technology, intelligently applied on site; enabling significant cost savings in the final solution for ventilation upgrade.
Heathrow Airport Ltd
Additional key facts
Findings of jet fan system upgrade published in BHR ISAVFT 2013, Performance evaluation of jet fan deflectors for road tunnel longitudinal ventilation, Gary Clark, Atkins Ltd, 2013.