We conducted small-scale explosion experiments to assess the effect of the shape of an underground magazine both with and without a dike. The values of the internal length-to-diameter ratio L/D of the magazine model were 9 and 21, respectively, with the inner diameter fixed as 38.8 mm. The overpressures of the blast wave were measured using piezoelectric pressure sensors. A series of explosion experiments provided the azimuth angle characteristics of the peak overpressures of the blast wave from the exit. Increasing L/D led to a reduction in the peak overpressure. We discuss the applicability of an empirical formula proposed previously for L/D =3 but now for varying L/D , which implies that the azimuth angle characteristics depend only on properly referenced data such as the peak overpressure in the exit direction. This gives the peak-overpressure distribution around an underground magazine with 3 ≤ L/D ≤ 21.
small-scale experiment, blast wave, azimuth angle characteristics, underground magazine, magazine shape