International audienceSEVESO industrial sites are suspected to produce major accidents, as for instance explosions, meaning that the disruptive effects of the blast wave may significantly impact the neighborhood. Despite effective mitigation measures may be taken, some residual risks exist which sometimes requires a protection of the buildings. In the specific case of blast, walls may be constructed to try and shelter important buildings. This kind of technique was developed decades ago in the pyrotechnical/ammunition industry for instance to avoid the transmission of an accidental explosion from a depot to the next one [1]. The protection is often a bund which characteristic sizes (thickness, height…) are much larger than that of the pressure wave. In the case of SEVESO industrial sites, the blast originates from a vapor cloud explosion, not from a detonation, so that not only the form of the pressure wave is different (“N” type rather than “triangular”) but also its duration, usually longer by orders of magnitude [2]. The duration of the wave might be hundreds of ms so that the wavelength of the wave amounts easily tens of m, larger than the characteristic dimensions of a bund. What kind of protection a blast wall would be able to offer in such circumstances? This specific aspect was investigated experimentally and a tentative interpretation is proposed using a CFD tool
