Science and Technology of Energetic Materials

Vol.67, No.6 (2006)

Research paper

Study on the shock sensitivity of an emulsion explosive by the sand gap test
Koki Ishikawa, Takayuki Abe, Shiro Kubota, Kunihiko Wakabayashi, Tomoharu Matsumura, Yoshio Nakayama, and Masatake Yoshida


The gap test has been widely used as the shock sensitivity test for explosives. Shock sensitivity determined by the gap test is one of the important safety measures for explosives.

A specimen consisting of a vinyl chloride tube and two mortar discs filled with sand was used as the gap material, and an emulsion explosive widely used as a commercial explosive with comparatively high shock sensitivity was used for the donor and acceptor charges. Both charges had a cylindrical shape with the ratio of the length to the diameter (L/D) being set to 1. The thickness of the sand layer between the two mortar discs of a constant thickness was adjusted by changing the height of vinyl chloride tube.

The objective of this study was to obtain basic data on sympathetic detonation experimentally. We studied the shock sensitivity of different amounts of explosives by the gap test method to clarify the scale effects.

The experiments were conducted with four amounts of explosives, i.e., 20 g, 160 g, 1.25 kg and 5 kg, and the relationship between the gap thickness and amount of explosives was determined. The following results were obtained.
1) It was possible to determine the each boundary between sympathetic detonation and non-detonation within the range of 2.5 mm, 5 mm, 10 mm, and 20 mm, where the respective critical gap lengths were 14.2 mm, 33.1 mm 90.4 mm, and 130.4 mm for explosive amount of 20 g, 160 g, 1.25 kg, and 5 kg, respectively.
2) There was found to be a linear relationship between the critical gap length and the amount of explosives on the logarithmic scale.

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Shock sensitivity, Sympathetic detonation, Sand gap test, Scale effects, Emulsion explosive

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