In this study Dynamic Finite Element Modelling is used to investigate the
distribution of peak particle accelerations (PPA) induced in a rock mass
by a vertical decked column of explosives. The rock mass is assumed to
be viscoelastic. The influence of the delay time between decking charges,
the viscosity attenuation (quality factor Q), the decking configuration, and
the velocity of detonation (VOD) on PPAs is examined. The results of
this paper are relevant to fragmentation since the nature of the
fragmentation is related to the stress magnitude and hence the PPAs. It
was found that increasing the VOD, and increasing Q increases the PPAs
in the neighbourhood of the blasthole. However, the VOD and rock
quality factor Q have little influence upon the distribution of PPA. It was
also found that an even distribution of PPAs, at a fixed distance from the
blasthole, could only be obtained by increasing the ratio of charge length
to stemming length. The study showed that the amplitudes and
distribution of PPA surrounding the blasthole was approximately
independent of the delay time between the decked charges. The
modelling also shows that the particle accelerations at locations below the
bottom of the charge are relatively small and so the model predicts no
substantial damage below the bottom of the charge after blasting.