On the azimuth angle characteristics of the blast waves from an underground magazine model (IV) -Large-scale field experiments-

We conducted large-scale field explosion experiments of an underground magazine model and applied an emulsion explosive of the order of kilograms. The overpressures of the blast wave were measured using piezoelectric pressure sensors. Experimental data were obtained at four azimuth angles (0 degrees, 60 degrees, 120 degrees, and 180 degrees, where 0 degrees defines the exit direction). As the azimuth angle increased from 0 degrees to 120 degrees, the peak overpressures reduced, then recovered at 180 degrees. We compared the results with those of laboratory experiments using a 1-g pellet of pentaerythritol tetranitrate. The loading density, defined as the ratio of the mass of the explosive to the volume of the magazine, was equivalent in both experiments. To account for the different types of explosives, we scaled the isobaric plots of the field experiments by a conversion factor estimated from the peak overpressures of the two experiments at a reference point. For similar magazine shape and loading density, the scaled isobaric plots did not depend on the mass and the type of explosive.