Mining_Methods_UnderGround_Mining - Mining and Blasting

zinkgruVan, Sweden
Boltec LC installing rockbolts in a development drift.
a 165 mm hole for gravitating into Nygruvan,
and a 300 mm hole for pumping
under high pressure into Burkland.
The fill is transported through 6 in
steel pipes along the distribution levels,
connected by plastic pipes into the
stopes.
Advantages of longhole open stoping
with paste fill are: improved working
environment for all underground activi-
ties with regards to exposure of open
stopes and backfill; reduced pillar
reservation, leading to increased ore
reserves; increased flexibility, with
more stopes in simultaneous production
and lower grade fluctuation; all tailings
can be used; no bulkheads required;
reduced drainage water; and possibility
of filling abandoned stopes.
Disadvantages are: higher costs than
conventional hydraulic fill; and plugged
fill pipes and drill holes require more
effort.
The long-term focus is directed towards
optimization of the water/cement
ratio in the paste fill, with a view to
reducing the amount of cement used.
lower development
In order to mine below the 800 m level,
the mine uses three Kiruna Electric
trucks for ore and waste haulage to the
main crusher. A Simba M4C longhole
drill rig is used on production, drilling
up to 40 m-long x 76 mm or 89 mmdiameter
blastholes. The machine produces
some 50,000 drillmetres/year,
while an older Simba 1357 drills a similar
number of metres in the 51-64 mm
range. The mine is so impressed with
the stability of the Simba M4C rotation
unit that it has had an old Simba 1354
rebuilt to incorporate the same unit. A
new Simba M7C handles the cable bolt
drilling. The drilling consumables are
supplied by Atlas Copco Secoroc under
contract. The ramp will be driven from
the current 980 m to the 1,100 m level.
An Atlas Copco Rocket Boomer L2 C
is used on ramp and sublevel development,
where the requirement is for 18
rounds/week on a 2 x 7 h shift basis.
The mine has purchased a second twin-
boom Rocket Boomer, this time an M2 C,
which is the mining version of the
Rocket Boomer L2 C.
rock reinforcement
The mine installs up to 20,000 resin anchored
rockbolts each year, and, having
upgraded its production process, found
that bolting became the new bottleneck.
After prolonged testing of the latest
Atlas Copco Boltec LC, they ordered
two units.
Using these machines, the working
environment for the bolting operatives
has improved immeasurably, since the
continuous manual handling of resin
cartridges has been eliminated. The
Boltec LC is a fully mechanized rockbolting
rig, with computer-based control
system for high productivity and precision.
The Zinkgruvan models feature a
new type of magazine holding 80 resin
cartridges, sufficient for installation of
16 rockbolts. It is equipped with a
stinger, which applies constant pressure
to keep it stable at the hole during the
entire installation process. The operator
can select the number of resin cartridges
to be shot into the hole, for which the
blow capacity is excellent.
The Rig Control System (RCS) fea-
tures an interactive operator control
panel, with full-colour display of the
computer-based drilling system. Automatic
functions in the drilling process,
such as auto-collaring and anti-jamming
protection, as well as improved regulation
of the rock drill, provide high per-
formance and outstanding drill steel
economy. There is integrated diagnostic
and fault location, and a distributed
hydraulic system, with fewer and shorter
hoses for increased availability. Data
transfer is by PC-card, which also
allows service engineers to store optimal
drill settings.
The MBU bolting unit on the Boltec
LC features a single feed system, utilizing
a cradle indexer at the rear end,
and a robust drill steel support plus
indexer for grouting at the top end. It is
equipped with a low-mounted magazine
for 10 bolts, designed for maximum
56 underground mining methods