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