ABSTRACT: The concepts of probability and risk can be applied to blast designs and the expected results of these designs. The natural variability in some blast design parameters, its impact on blast performance predictions and the use of probability in blast design are discussed.

Measurements can be made of the variability of blast design parameters and combined with estimates of our lack of knowledge of these parameters. These are expressed in terms of frequency distributions. From these data probability distributions for the expected results of the blast (i.e. maximum ground vibration, flyrock range, fragmentation size distribution, extent of damage etc.) can be calculated. This approach determines the uncertainty in achieving the desired results from the variability of outcomes.

If the probability of a successful blast (i.e. "reliability" of the design) can be determined it can be weighed against the associated cost of implementing the design and the likely cost of failure. This leads to more informed decisions based on quantifiable success, quantifiable design parameters and estimates of the probability of failure with associated costs, particularly in critical situations. The cost of failure includes such things as reduced production due to oversized muck through to closure of operations due to excessive vibration or flyrock.

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