Internal separation distances for underground explosives storage in hard rock

Most recent studies on underground explosives storage have focused their attention on external safety distances, mostly inhabited distances for airblast, debris, and ground shock. Internal distances in prevailing codes generally deal with the need to prevent sympathetic detonation as a result of propagation by rock spall impact, or to prevent damage in an adjacent chamber in the event of an accidental explosion. For complex facilities, guidelines on separation requirements are often lacking. Also, there are several inconsistencies in the current separation requirements. This paper attempts to fill in the gap and rationalise the separation requirements for the various components of an underground storage facility. Recommendations will be made based on a comprehensive review of tunnel damage and results from large-scale tests.