A subsurface magazine has an explosive storage chamber, a horizontal passageway, and a vertical shaft for vent. It was proposed and legislated in Japan. The authors found that small amount of water on the floor of its storage chamber mitigated the blast pressure remarkably. The mechanism of the mitigation has been studied, however, it is not still well understood. In this study, the explosion in a transparent, square cross section, and straight tube was carried out to examine the mechanism of blast-wave mitigation by water. The arrangement and amount of water in the tube were varied for five ways. The dependence of mitigation effect on the arrangement and amount of water was evaluated by measuring the blast pressures in the tube and outside the tube. The results of this study concluded that the mitigation of blast wave by water is mainly due to the interaction between the explosion and the water very near the explosion point. On the contrary, the water at other part of the tube was found to strengthen the blast pressure.

Blast Wave Mitigation from the Straight Tube by Using Water Part I - Small Scale Experiment

A subsurface magazine is proposed to reduce the debris and the air-blast pressure caused by an accidental explosion. First, 1/20-scale indoor explosion model tests for subsurface magazines were con...

Internal explosion tests for scaled subsurface magazines

As proposed and legislated in Japan, subsurface magazines have an explosive storage chamber, a horizontal passageway, and a vertical shaft for a vent. The authors found that a small amount of water on the floor of the storage chamber mitigated blast pressure remarkably. The mitigation mechanism has been examined more closely. To examine the effect of water, the present study assesses explosions in a transparent, square cross section, and a straight tube. A high-speed camera used to observe the tube interior. Blast pressure in and around the tube was also measured. Images obtained using the high-speed camera revealed that water inside the tube did not move after the explosion. Differences between cases of tubes without water and with water were unclear. Along with blast pressure measurements, these study results suggest that blast pressure mitigation by water occurs because of interaction between the explosion and the water near the explosion point.

Explosion interaction with water in a tube

Mitigation of blast wave, caused by explosion of explosives, from a straight tube using water in a bag (water bag) was evaluated. The length of the tube was 330 mm and the cross-section area was 30 x 30 mm2. One end of the tube was closed. The water bag was placed on the floor or closed end wall of the tube near the explosive. The thickness of water was 3 mm. A specially designed small detonator, which contains lead azide of 100 mg, was ignited near the closed end wall of the tube. The blast pressure outside the tube was measured and examined. The blast wave was remarkably mitigated by the water bag. Equivalent ratio analysis revealed that the glass beads absorbed 33%-45% of explosion energy.

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Blast mitigation by water in a bag on a tunnel floor

The subsurface magazine is a new type of magazine in Japan, which is defined as a magazine constructed underground and equipped with elevators of other transportation means. and is different from the usual tunnel type underground magazine.

Explosions of explosives in model subsurface magazines were carried out. and explosion gases and shock waves blown out from their entrances were observed by schlieren photography. The blast overpressures were also measured by piezoelectric transducers. these external effects by explosion of explosives in the subsurface magazines were found to be less than those in the underground magazines.

The above phenomena were simulated by numerical analysis using PISCES 2DELK code. Caluculated maximum overpressure and velocity of gases and shock waves were in fair agreement with their experimental values.

Kunihiko Munemasa

Papers

Explosion of Explosives in Subsurface Magazines and its numerical analysis