Mining_Methods_UnderGround_Mining - Mining and Blasting

0.1% Cu, 99 g/t Ag and 0.3 g/t Au.
Probable ore brought total reserves up
to 10.67 Mt. That compares with 3.63
Mt of reserves at the beginning of 2005.
Total resources were also increased, from
11.08 Mt in January, 2005 to 13.22 Mt.
This should be sufficient to add another
15-20 years to mine life.
These quantities should increase
further when portions of the orebodies
at Kaspersbo (from 1,000 m down to
1,300 m), Lappberget (500–800 m and
1,100–1,400 m), Dammsjön (500–785
m and 925–1,100m), and a smaller section
at Tyskgården are included in the
reserves figures. Kvarnberget is yet to
be added, and Boliden is also exploring
to the north of the Gransjön where the
property extends for several kilometres.
Sublevel stoping at
lappberget
The geological and geotechnical characteristics
of significant portions of the
newly-discovered orebodies allow mi-
ning using more productive longhole
methods instead of cut-and-fill. Lappberget
ore, for instance, can be 60 m-wide
through considerable vertical distances,
and has proved to be suitable for sublevel
stoping using a system of primary
and secondary stopes progressing upwards.
Primary stopes are 15 m-wide
and 40 m-high and filled with paste
made from concentrator tailings mixed
with about 5% cement. The 20 m-wide
secondary stopes are filled with development
muck without cement. High pre-
cision drilling is necessary to get optimum
ore recovery and fragmentation.
This mining method can possibly be
used in parts of the Kaspersbo orebody,
if rock quality is high enough. This will
help with cost control, which is crucial
for mining in Sweden. With Lappberget
alone containing 5.46 Mt of the current
reserves, grading over 7% zinc and 2.6%
lead, plus silver and gold, it is no surprise
that present development activities
focus on using longhole-based production
from these orebodies to raise total
metal-in-concentrate output. Presently
eight orebodies are being exploited.
Garpenberg has generated a strategic
plan for 2006–2019 allocating SEK 1
billion for developing Lappberget. The
overall programme includes: increasing
Mined in
“Central Zone”
Possible
sequence
Sublevel stoping layout and mining sequence for Lappberget orebody.
concentrator capacity to 1.2 Mt/y;
designing and building a paste fill production/distribution
system; and starting
longhole drilling. This latter project
involved rill mining in the Tyskgården
orebody, followed by sublevel stoping
in Lappberget.
rill mining
A special mining method known as rill
mining has been developed for excavating
the Tyskgården orebody. The orebody
is relatively small, and large quantities
garPenBerg, Sweden
of development muck have to be accommodated
underground as hoisting facilities
are used for ore only.
The method can be described as a
modified sublevel stoping with successive
back fill as mining is progressing.
The 10 m-wide cut-off slots are drilled
across the orebody using up-holes and
blasted in one single firing, starting from
the centre. Seven 127 mm holes are left
uncharged to provide sufficient expansion
for the remaining 64 mm holes.
After the slot has been opened, 70 de-
grees up-holes fans consisting of eight,
underground mining methods 49
17.5 m
Drawpoint
spacing
3 m
3 9 4 10 5 11
Development and primary stoping layout 1080 level.
Primary stope:
15 m wide x 40 m high
Paste fill
6
896 Z
916 Z
956 Z
Secondary stope:
20 m wide x 40 m high
Rock fill
Note:
How this hole must be designed to just
miss the drift below to break properly
996 Z