Modeling Vs. Monitoring Blast Movement: The Cost of Variation
In March of 2013, an undisclosed gold mine (MINE X), located in the Western United States, performed blast movement monitoring of three blasts occurring in one of two active pits.
Blast Movement Monitors (BMMs) were placed in the bench before blasting, and located after the blast to determine vectors of movement. Using blast movement software, ore/waste boundaries were translated.
These locations were compared to MINE X’s standard ore translation procedure, which consisted of moving polygon boundaries by 17.5 feet (5.3 m) in the burden direction of the blast hole pattern. This translation amount, identified by MINE X as “average” motion, had been ascertained by performing a previous blast movement study.
All three of these blasts were monitored on the same bench, in the same pit, with the same timing and caps, and in similar geological types. Although every blast is different, variation exhibited when all designed variables are held constant can still have serious financial consequences for mining operations.
It is important to note that each blast varied significantly from the mean. The consequence of this variance is that no blast moves according to a template, even when all controllable attributes are held constant. Even if the overall movement in a blast were to move according to the “average” template, the random variance within a single blast is such that individual points will not actually move according to the modeled displacement.
In this case, the benefits of direct monitoring were far in excess of the costs. The return on investment (ROI) for blasts 9480-47 and 9480-52 was 14.5 in the actual situation and 20.4 in the scenario presented. The cost of the observed variation reached $5,209 per foot from the control case and could have easily resulted in losses of $6,920 per foot.