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.
ギャップ試験は爆薬の衝撃起爆感度試験として広く行われている。ギャップ試験によって決定される衝撃起爆感度は，爆薬の重要な安全対策の1つである。
ギャップ材は，砂を装填した塩ビ管を2枚のモルタル円板で挟むことによって製作し，励爆薬，受爆薬には比較的衝撃感度の高い産業爆薬として広く使用されているエマルション爆薬を用いた。爆薬試料はいずれも直円柱状で，その高さと直径の比(L/D)は，1とした。一定の厚さの2枚のモルタル円板で挟まれた砂の層の厚さは，塩ビ管の高さを変化させて調整した。
本研究では，殉爆に関する基礎データを実験的に取得し，衝撃起爆感度の薬量効果に関して検討するため種々の薬量のギャップ試験を行った。
20 g，160 g，1.25 kg及び5 kgの4種類の薬量で実験を行い，ギャップ材厚さと薬量の関係を求め，以下の結果を得た。
1） 殉爆，不爆の境目は薬量20 g，160 g，1.25 kg及び5 kgに対し，各々2.5 mm，5 mm，10 mm及び20 mmの範囲で詰めることができ，限界ギャップ長は，各々14.2 mm，33.1 mm，90.4 mm及び130.4 mmであった。
2） 薬量と限界ギャップ長の間には，両対数目盛りで直線関係のあることがわかった。）
Shock sensitivity, Sympathetic detonation, Sand gap test, Scale effects, Emulsion explosive