The series of card gap test like experiments were carried out to examine the relation between gap length and sympathetic detonation of plastic high explosive, and the scale effect of shock initiation sensitivity of the explosive. Composition C-4 explosive charges (1400kg∙m-3 in density) of cylindrical shape and with same weight, were used as donor and accepter charges. The ratio of charge length to diameter (L/D) was set to be one. The experiments have been conducted with five explosive weights; 10g, 40g, 320g, 2.5kg, and 20kg. Three kinds of gap materials, i.e., mortar, light weight concrete and sand with various thicknesses, were used. The sand layer was sandwiched by two thin mortar disks. Detonation or no-detonation of accepter charge was determined by observing the situation of a mild steel witness plate after the experiment. It became clear that, even in the case for 20 kg charge, the critical gap length of detonation and no-detonation can be evaluated in the range of 20mm or so. Furthermore, in log-log coordinate system of gap length as a function of explosive weight, it was found that all three gap materials showed good linear relationship, and those inclinations were larger than the value of the scale factor of explosive weight ( =0.333). It was obtained a tendency that the material with higher density showed higher obstruction effects to prevent the sympathetic detonation.
可塑性爆薬のギャップ長と殉爆の関係，また，当該爆薬の衝撃起爆感度の規模効果を調べる目的で，カードギャップ 試験に類似したシリーズ実験を行った。励爆薬と受爆薬には，同薬量の円柱形コンポジションC４爆薬（密度1400 kg・m-3） を使用した。爆薬長さと直径の比（L/D）は１とした。５水準の薬量（10g，40g，320g，2.5kg，および20kg）で実験 を行った。様々な厚さの３種類のギャップ材（モルタル，軽量コンクリート，砂）を使用した。砂の層は２枚の薄いモ ルタル板でサンドイッチにした。受爆薬の爆・不爆は，軟鋼製の証拠板を観測することで判定した。本実験により，薬 量20kgの場合でも，爆・不爆の限界ギャップ長を20mm程度の範囲で評価できることが分かった。加えて，３種類のギャッ プ材全てについて，爆薬量と限界ギャップ長は両対数座標系で良好な直線関係を示すこと，それらの傾きは爆薬のスケー ル則の値（1/3＝0.333）より大きいことが分かった。また，本実験で用いた薬量の範囲では，密度の高い材料ほど，殉爆 阻止効果が大きくなる傾向が得られた。
shock sensitivity, sympathetic detonation, gap test, scale effects, composition C-4.