Far field blast parameters from cuboidal charges

The loading experienced by civilian infrastructure as a result of an explosion is often of high magnitude, and as such, accurate prediction of blast parameters is necessary to ensure structural robustness and resilience. Whilst there is significant literature around the characterisation of hemispherical and spherical charges, the same cannot be stated for different shapes of charge, which have not been studied to the same degree. Accidental or malicious explosions rarely conform to this (hemi-)spherical approximation and the resulting loading may differ substantially from the predicted values. However, there currently is no recognised tool with the ability to accurately predict loading parameters from non-spherical charge shapes, highlighting the need for a thorough experimental investigation into the effects of charge shape. This article presents the results from experimental tests using 250g PE4. Cuboidal charges of 1:1:1 and 1:1:3 (L:W:H) aspect ratio were surface-detonated at standoff distances between 2m to 8m from rigid reflecting surfaces with flush-mounted piezoresistive pressure gauges. Predictions for hemispherical surface bursts from a validated predictive tool are used to make comparisons to the recorded experimental data, highlighting significant differences in the loading parameters from cuboidal-shaped explosives. Specifically, a prominent subsequent shock, with a magnitude equal to that of the primary shock at the furthest scaled distances, seen in the cuboidal charge waveforms. Overall, it is seen that the behaviour of the blast wave emanating from cuboid charges strongly depends on scaled distance, in particular the significance of the aforementioned secondary feature. Furthermore, the substantial differences between hemispherical blast parameters and the cuboidal experimental data presented herein shows there to be a significant gap in the knowledge, which clearly warrants additional research.