In recent years there has been a definite trend of increased use of underground magazines for explosives storage in Western Australia. While this practice avoids some of the downsides of traditional surface storage, it creates new challenges that may not have been recognised, or properly addressed, particularly the potential effects of unconfined blasts.
A review of research papers indicates that the overpressure from unconfined underground blasts is more destructive than is generally understood. Blast waves propagate significantly further through underground tunnels than on the surface. Cross-cuts and corners have limited effect and only decrease the overpressure by some 10 to 25 per cent for high pressures. Pressure waves may be intensified as they reflect off walls and other surfaces, resulting in peak pressures that are greater than the initial blast overpressure.