Modern Quarrying July-August 2016

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32 MODERN QUARRYING July - August 2016
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QUARRYING
SERVICES
example, operations can check these
factors as well as calculate drilling devi-
ation from the design at fixed intervals.
Boretrak comprises a control display unit
(CDU) logger, a rack of rods, a probe and
a gyroscope or gravity sensors. All of
this equipment feeds into an interface
which can represent the status of a drill-
hole, removing all guesswork from blast
planning.
Other equipment which is crucial
in checking drillholes is borehole calli-
per logs, which comprise a tripod with a
probe on a pulley which is lowered into
the hole. The probe is equipped with arms
that can open out on command to mea-
sure the average diameter and average
variance of the drillhole.
In an ideal world, the hole should
resemble a cylindrical tube – with smooth
walls and an equal diameter through-
out. In reality, however, there are often
deviations. By measuring these devi-
ations with the probe, blasting teams
can determine the optimal amount and
type of explosives that each unique hole
requires or if the hole needs slight drilling
adjustments.
A well planned and successfully exe-
cuted blast has several benefits. It can
deliver operation-specific fragmentation
levels that result in improved productiv-
ity and remove the need for secondary
blasts. This is because the correct level
of fragmentation reduces the levels of
loading and hauling, and optimises plant
operations by making processes such as
crushing more efficient.
A successful blast also improves safety
because it reduces the amount of flyrock,
while its environmental benefits include
meeting airblast and ground vibration
limits.
While the information that surveying
provides is crucial, it is what operations do
with it that really counts. Through thor-
ough measurement and analysis, opera-
tions can take corrective action to reduce
downtime and unnecessary secondary
blasts. By ‘measuring twice and blasting
once’, mines can reap the financial and
operational rewards of thorough plan-
ning and measurement.
Manare Mokoatlo, mining engineer, AEL
Mining Services, presented the paper entitled
The Importance of Blasthole Monitoring at the
recent IQSA conference in Cape Town.