Explosion Mitigation Techniques in Tunnels and their Applicability to Scenarios of Hydrogen Tank Rupture in a Fire

This paper presents a comprehensive review of existing explosion mitigation techniques for tunnels and evaluates their applicability in scenarios of hydrogen tank rupture in a fire. The study provides an overview of the current state of the art in tunnel explosion mitigation and discusses the challenges associated with hydrogen explosions in the context of fire incidents. The review shows that there are several approaches available to decrease the effects of explosions, including wrapping the tunnel with a flexible and compressible barrier and introducing energy-absorbing flexible honeycomb elements. However, these methods are limited to the mitigation of the action and do not consider either the mitigation of the structural response or the effects on the occupants. The study highlights how the structural response is affected by the duration of the action and the natural period of the structural elements and how an accurate design of the element stiffness can be used, in order to mitigate the structural vulnerability to the explosion. The review also presents various passive and active mitigation techniques, aimed at mitigating the explosion effects on the occupants. Such techniques include tunnel branching, ventilation openings, evacuation lanes, right-angled bends, drop-down perforated plates or high-performance fibre-reinforced cementitious composite (HPFRCC) panels for blast shielding. While some of these techniques can be introduced during the tunnel's construction phase, others require changes to the already working tunnels. To simulate the effect of blast wave propagation and evaluate the effectiveness of these mitigation techniques, a CFD-FEM study is proposed for future analysis. The study also highlights the importance of considering these mitigation techniques to ensure the safety of the public and first responders. Finally, the study identifies the need for more research to understand blast wave mitigation by existing structural elements in the application for potential accidents associated with hydrogen tank rupture in a tunnel.