Mining_Methods_UnderGround_Mining - Mining and Blasting

Boomer S1 L drill rig in operation.
the blast holes, and electric delay detonators
along with small primers are
used for blasting. Blasting takes place
around midnight, and the mine then ven-
tilates throughout the night.
Each blasted face produces about
60-65 t of rock, and each rig can drill
up to 10 faces/shift, depending upon the
availability of working places.
After the blast, the muck pile is washed
down, and the back is scaled. Ore
is loaded and hauled by the Scooptrams
from the headings to the orepasses.
Once the limits of the stopes are established,
then the final extraction takes
place with 3 m x 3 m pillars created
from the perimeter retreating to the
access ramp.
drilling performance
The mine drill rig fleet comprises three
Atlas Copco Boomer H126 L drill rigs
mounted with COP 1238ME rock drills;
five Atlas Copco Rocket Boomer S1 L
low-profile drill rigs mounted with
COP 1838ME rock drills; and three
older drill rigs retrofitted with COP
1238LP rock drills.
All drilling uses ballistic button bits,
of which the preferred 43 mm-diameter
Atlas Copco Secoroc SR35 bits used by
the COP 1838 rock drills are returning
370 m/bit, while the 41 mm-diameter
bits are returning 450 m/bit. In such
abrasive rock, bit wear has to be closely
monitored to avoid an escalation in
costs. Likewise, regrinding has to be to
a high standard.
Core drilling in the levels.
BarrOCa grande, POrTugal
The recent addition of Rocket Boomer
S1 L models to the fleet has resulted in
a 50% increase in output/drill rig, while
less waste rock is generated due to the
lower profile required for safe operation.
This drill rig will operate in a seam
height as low as 1.3 m and is equipped
with four-wheel drive for maximum trac-
tability. The COP 1838 rock drill has
double reflex dampening for high-speed
underground mining methods 139