Simulating large blast event using small scale explosive charges detonation has become a major tool in assessing the effects of terroristic or accidental threats. Scaling laws adapted to modern plastic explosives however still requires to be refined to achieve the necessary precision on the blast induced damages determination. This statement was the starting point of the cooperation between the Institute for Radiological Protection and Nuclear Safety (IRSN), a French public institute with industrial and commercial activities, and the French-German Research Institute of Saint Louis (ISL), a bi-national military research institute.

During the past few years, IRSN developed a strong experience on hemispherical blast effect assessment using 42g Hexomax® charges detonated in contact to a ground surface equipped with different types of pressure sensors (piezo-electric and piezo-resistive). Based on this experience, ISL developed a new outdoor blast-pad located at its own explosive range: 400g TNT equivalent charges are detonated in a factor 2 up-scaled version of IRSN test configuration. Similar sensors are flush-mounted inside a metallic rail integrated below the concrete pad surface. Blast effects generated by cast-TNT, Hexomax® and Semtex were recorded at the different IRSN reference scaled-up distances. Peak pressure, peak positive impulse and arrival time are analyzed and compared for the two different scales, in order to verify Hexomax® scalability between the two configurations, as well as the TNT equivalent factors (in peak pressure or positive impulse) of Hexomax® and Semtex.

All these measurements are supported by a novel high speed imaging setup based on direct lighting of the shockwave propagating in front of a specific reflective screen. This technique provided significant amount of light despite the camera to charge distance, and a consequent microsecond level of exposure time, leading to high precision images of the shock structure.