Flyrock is the
unexpected and undesirable projection of rock fragments during detonation of a
blast and managing this risk is becoming an increasing challenge as urban
development encroach toward mineral extraction sites. The basic factors
associated with flyrock are discussed in relation to geology, blast design and
management. Published data of historical flyrock events are investigated and
compared with local information on incidents. Good agreement was found between
the data sets. A computer program of flyrock was developed using projectile
motion based on launch velocity and angle, rock size, shape and density. This
deterministic model was coupled with a probability model to simulate blast
events. The impulse time t
of the explosive pressure was taken as the stochastic variable to replace
launch velocity. The variables were calibrated to replicate field data. A
simulation was executed to demonstrate the capability of the approach to
defining flyrock danger zones. For a simplistic situation it was identified that
an appropriate distance to be cordoned off for the blast danger zone is a radius
of 120 m in front of the blast and 65 m behind.