Analysis of the field test results of ammonium nitrate: fuel oil explosives as improvised explosive device charges

摘要

When the over pressure of a blast wave is calculated and its effects on valuated objects are set, many approximations are used. Basic relationships, used to calculate the maximum blast overpressure, safety distances and building damage, are created for industrial accidents or for objects where explosives and munitions are stored. This method is invalid in public spaces. More than 95% of all terrorist attacks are carried out using ANFO (ammonium nitrate - fuel oil) explosives in three different variants (ammonium nitrate with oil, ammonium nitrate with oil and aluminium powder or ammonium nitrate with oil and trinitrotoluene (TNT)).The commonly used method to calculate the overpressure uses a scaled distance. The value of the scaled distance is derived from heat created by combustion. A theoretical value for the combustion heat of an industrial-produced ANFO explosion does not represent the real history of explosion or the size of overpressure. For example, the heat of combustion of Slovak-produced DAP-E is the same as TNT. From the relationship used, it emerges that the explosions have the same capacity. We have conducted more than 130 field tests of the ANFO explosive, where the history of blast wave was recorded. The results of the measurements clearly show the invalidity of this theory. The values of the calculated and measured overpressure are significantly different. It is necessary to choose a different approach for the TNT equivalent method. In the first part of this paper, we present the results of the conducted field tests. The experimental results are analysed using commonly-used methods. At the end of our paper we present a new relationship, used to calculate the maximum blast overpressure, which is based on the measured overpressure. This paper presents the results of scientific research at the Faculty of Special Engineering, University of Zilina.