A recently-developed model is used as a tool to optimise the design of
blasts used to create final walls in large open pit mines. The use of this
tool has allowed present blasting practice and proposed designs to be
evaluated to predict the likely extent of rock damage behind the final
wall. The evaluation of the damage is dependent on the predominant
local geology. Modelling of damage using the software allows the potential zones of
rock damage to be evaluated under the following criteria: I . the extent of new fractures formed in the intact rock mass; and 2. the distance to which dilation and extension of existing
discontinuities and pre-existing fractures will likely occur. The computer model has been used to examine present blasting
practice and to estimate the damage induced by final and intermediate
rows of blastholes. The results of current practices are presented in a
visual form that allows simple comparisons to be made for any proposed
changes in design. To confirm the predictions of the modelling, physical measurements
are being undertaken at selected mines to quantify damage behind blast
patterns, and experimental programs are underway to measure near-field
vibration, or shock, levels. The computer modelling software is being
used to qualify and improve the design of final rock slopes in large
surface mining excavations, and to provide site engineers with
well-defined design criteria for consistency in design. The model is seen
to be just one of many tools which are being used in large open cut
mining operations to gain an improved understanding of blasting and
blast control.