Mining in focus
Downstream
impacts
of drilling and blasting
Drilling and
blasting are not
always given the
full emphasis it
deserves, writes
Anthony Konya.
[16] MINING MIRROR MAY 2018
D
rilling and blasting is a complex
process and plays a critical role in
process development and controlling
the cost throughout the mine. For example,
the blasting process dictates muck-pile
configuration, which affects shovel and
loader fill factors. The fill factor of the shovel
affects how many trucks are required on site,
how fast those trucks can be loaded, and the
truck fill factor. The fragmentation of the
blast affects the crushing costs and leaching
efficiency. The over-break of the blast affects
slope stability, slope steepness, pit safety, and
scaling costs. The blasting process impacts
every aspect of the operation and poor
blasting can lead to millions of dollars in
direct costs and tens of millions in indirect
costs at larger operations, such as copper
and gold mines. In many cases, the drill and
blast team may not need to understand the
haulage, as the haulage does not have an
impact on blasting (in a direct cost sense).
However, every person responsible for any
operation at a mine must at least understand
drilling and blasting — enough to explain
what they require of the drill and blast team.
How stemming can change blast
function
One variable of blasting is stemming.
Stemming is a material that is inserted
into a blast hole to help prevent gases from
escaping. Incorrectly placed stemming can
greatly decrease fragmentation size at a
blast. While important, stemming is not
nearly as vital as other variables such as
burden and stiffness ratio.
However, stemming can dramatically
change a blast’s function. It can reduce the
air overpressure from a blast by over 98%,
which dramatically reduces noise. Proper
stemming can also decrease the P80 (post
primary crush 80% passing size) of a blast
by over 10% and reduce mucking cycle times
by over 18%. It is incredible to think that
a few feet of gravel can really change the
blast this much. Poor stemming will blow
out, causing poor results for fragmentation,