Mitigation of open-air explosions by blast absorbing barriers and foam

Open-air explosions are inevitable connected to activities from the Ministry of Defense (e.g. large detonations or EOD operations). And also the industry uses open-air explosions for production processes (e.g. explosion welding). This requires the protection of people and buildings relatively close to the source. But the annoyance, for instance due to rattling, can also be an issue for the surrounding community. Often, mitigation measures are necessary, but due to the high source energy this is not an easy task. Two techniques have been tested for charges ranging from 20 to 500 kg. The first technique applies a porous barrier at less than 10 m from the source. The mitigation at 300 m from the source was predicted with a model that takes into account the non-linear interaction with a barrier as well as the nonlinear interaction with the porous material (here: gravel). The model has been validated in a previous research phase. It is demonstrated that, depending on the barrier construction, a significant reduction of the shock wave can be achieved. The second technique applies water based foam directly on the explosives. Blast measurements have been carried out up to 200 m from the source. Peak level reductions ranging from 20 to 50% were achieved.