The movement of ore within a blast can have significant economic impact on open pit metal mines. The deposits are often heterogeneous with valuable mineralization disseminated throughout the planned mining blocks and benches.
Blasting of these blocks is necessary to fragment the rock mass and loosen the resulting muckpile for efficient excavation however blasting causes movement of the rock and this is detrimental to the accurate delineation of the ore and waste regions within the resulting muckpile. The consequences can be ore loss (the ore moves to a region marked as waste and is discarded) and dilution (waste is miscategorised as ore and sent to the concentrator). If the movement can be accurately measured, ore loss and dilution can be minimised and significant increase in profit can be realised.
Various methods have been used to assess muckpile movement, including poly-pipe, sandbags and magnets but these have been either inaccurate or impractical.
Orica Mining Services commissioned BMT to use their Blast Movement Monitors (BMMs) to measure movement within blasts at two gold mines.