Study on the effect of shape parameters and initiation points of rectangular high explosive on the spatial distribution of blast loads

Rectangular explosive charges are usually used in military or civilian explosive transportation and storage. The effects of shape parameters and detonation positions on the peak overpressure and maximum impulse of blasts lack comprehensive investigation, which is significant for the design of blast-resistant structures. In this paper, the side-length ratio of the rectangle, orientation, and detonation position of the charge are chosen as controlling parameters to investigate their influence on blast loads in the scaled distances of the gauges ranging from 0.63 to 10.54 m/kg^1/3 with well validated 3D numerical simulations. The results show that there is a large difference in the near-field spatial distribution of the blast load of the rectangular charge; if the blast load of the rectangular charge is simply evaluated with the spherical charge, the maximum peak overpressure (maximum impulse) will be underestimated by a factor of 7.46 (4.84). This must be taken seriously by blast-resistant structure designers. With the increase in the scaled distance, when the critical scaled distance is greater than 6.32 (7.38) m/kg^1/3, the influence of the charge shape on the maximum peak overpressure (maximum impulse) of the spatial blast load can be ignored. In general, the impact of detonation of the charge at the end on the maximum peak overpressure is greater compared with central detonation, but for the impact of the maximum impulse, it is necessary to pay attention to the side-length ratio of the rectangular charge and the specific detonation position on the end face. Furthermore, the structural response of steel plates placed at different azimuths under the blast load of a rectangular charge is preliminarily analyzed, and the results show that the deformation and energy of the plates are consistent with the distribution of the blast load. These analysis results provide a reference for the explosion protection design in near-field air explosions.