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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Production<br />
area<br />
5<br />
4<br />
80 m<br />
57,5 m 22,5 m<br />
1. Development<br />
Principle 2. Drilling of pre-undercut & blasting at Esmeralda. to start caving<br />
3. Development<br />
4. Open trenches (boxholes + drilling)<br />
in turn 5. Extraction are related to the scheduling of<br />
the development of the drawbells, <strong>and</strong><br />
construction of the drawpoints.<br />
The pre-undercut variant has been a<br />
substantial success in the Esmeralda sector,<br />
with only minimal damage occurring<br />
on the production level, <strong>and</strong> its<br />
associated orepasses <strong>and</strong> drawpoints.<br />
There was a significant reduction of<br />
damage to the drifts located under the<br />
undercut level, as well as a significant<br />
reduction of rockburst occurrence by<br />
better draw management. The stability<br />
<strong>and</strong> rock condition with the pre-undercut<br />
variant dramatically improves, so it<br />
was possible to reduce the cost of support,<br />
<strong>and</strong> increase the availability of the<br />
area by nearly 90%.<br />
Some optimization of the pre-undercut<br />
is still continuing, in particular some<br />
fine-tuning of undercut level pillars <strong>and</strong><br />
improvement of the co-ordination <strong>and</strong><br />
scheduling of the development activities.<br />
It is vital that the spacing of the activities<br />
is maintained, so as to keep the<br />
production development ahead of the<br />
active cave, but still within the destressed<br />
area.<br />
Current productivity obtained at<br />
Esmeralda is over 115 t/day/worker. In<br />
comparison with other methods such as<br />
sublevel caving, panel caving gives El<br />
Teniente more advantages. The direct<br />
cost of the sublevel caving method is at<br />
least double that of panel caving, <strong>and</strong><br />
the current direct cost for mine at El<br />
Teniente is US$2.5/t of ore, <strong>and</strong> indirect<br />
costs close to US$1/t<br />
The average cost of panel caving is<br />
US$3.5/t, compared to more than US$5/t<br />
3<br />
Undercut area<br />
Production<br />
area<br />
2<br />
5<br />
4<br />
Preparation area<br />
for sublevel caving. Hence, El Teniente<br />
is developing its new productive sectors<br />
using the panel caving method with preundercut,<br />
though other variants could<br />
be used, depending on the local conditions,<br />
lithology, stresses <strong>and</strong> economics<br />
of each sector.<br />
Production at esmeralda<br />
1<br />
1. Development<br />
2. Drilling & blasting to start caving<br />
3. Development<br />
4. Open trenches (boxholes + drilling)<br />
5. Extraction<br />
Cave undercutting at Esmeralda is presently<br />
carried out with the 'parallel long<br />
hole' technique, which basically consists<br />
of excavating an 855 cu m pillar of solid<br />
rock 11.4 m-wide, 25 m-long <strong>and</strong> 3 mhigh.<br />
A triangular pattern of 14 parallel<br />
long holes of 3 in-diameter, with 9 rows<br />
of 2 holes <strong>and</strong> 1 hole each is used. This<br />
pattern has better efficiency, absorbs<br />
blast hole deviation, <strong>and</strong> avoids formation<br />
of residual pillars.<br />
Drilling is carried out with an Atlas<br />
Copco Simba H157 drill rig, whose output<br />
is 60 m/shift of 3 in-diameter holes<br />
<strong>and</strong> 85 m/shift of 2.5 in-diameter holes.<br />
St<strong>and</strong>ard ANFO is the column charge,<br />
with 300 gm cylindrical pentolite as the<br />
booster, detonated using Nonel.<br />
Atlas Copco equipment at Esmeralda<br />
includes one Rocket Boomer, two Boltec<br />
rigs, two Simba rigs <strong>and</strong> one 3.5 cu yd<br />
Scooptram loader.<br />
In the production level, a fleet of<br />
nine LHDs is used, including Atlas<br />
Copco Scooptram ST6C <strong>and</strong> ST1000<br />
loaders of capacities 6 cu yd <strong>and</strong> 7.3 cu<br />
yd respectively.<br />
The support methods used in Esmeralda<br />
include 22 mm-diameter <strong>and</strong> 2.3<br />
m-long bolts, 6 mm-diameter by 10 cm<br />
Undercut area<br />
el TenienTe, CHile<br />
Preparation area<br />
spacing mesh, 10 cm-thick shotcrete, <strong>and</strong><br />
6 in-diameter cable bolts. There are two<br />
types of cable bolts, plain <strong>and</strong> birdcage,<br />
which are 4 m to 10 m-long, <strong>and</strong> 5 m to<br />
2<br />
7 m-long respectively. 1<br />
raise boring<br />
In an interesting application during the<br />
development of Esmeralda, two Atlas<br />
Copco Robbins raise boring machines,<br />
a 34RH <strong>and</strong> a 53RH were used. These<br />
are multipurpose machines, <strong>and</strong> can be<br />
employed for upwards boxhole boring<br />
or down reaming, as well as conventional<br />
raiseboring.<br />
At Esmeralda, the Robbins 34RH unit<br />
was used in the production level to drill<br />
draw bell slot vertical holes approximately<br />
15 m to 20 m-long <strong>and</strong> 0.7 mdiameter.<br />
The machine worked three<br />
shifts/day, giving a penetration rate of<br />
2.1 m/h. It had a capacity of 93 m/month<br />
<strong>and</strong> a utilization rate of 39%.<br />
The Robbins 53RH was employed to<br />
bore 1.5 m-diameter boxholes up to 75<br />
m-long for use as ventilation shafts, <strong>and</strong><br />
inclined pilot raises for orepasses, with<br />
an average length of 24 m. The machine<br />
worked three shifts/day, giving a penetration<br />
rate of 1.8 m/hr. It had a capacity<br />
of 111 m/month <strong>and</strong> a utilization<br />
rate of 57.3%.<br />
Atlas Copco trained the operators<br />
from El Teniente, <strong>and</strong> was in charge of<br />
the equipment maintenance during the<br />
first few months.<br />
rocket Boomer drill rigs<br />
Shortly after acquiring the raise boring<br />
machines, El Teniente acquired two<br />
Atlas Copco Rocket Boomer 282 drill<br />
rigs for drift development at Esmeralda.<br />
In order to increase the drilling pre-<br />
cision, the mine installed the Atlas<br />
Copco Feed Angle Measurement (FAM)<br />
instrument on the Rocket Boomer units.<br />
The machines also featured the direct<br />
controlled drilling system, which incorporates<br />
the anti-jamming function<br />
Rotation Pressure Controlled Feed Force<br />
(RPCF).<br />
The Rocket Boomer rigs were fitted<br />
with COP 1838 rock drills with 20 KW<br />
impact power <strong>and</strong> dual-damping system,<br />
giving high speed drilling <strong>and</strong> good steel<br />
economy.<br />
underground mining methods 87<br />
80 m<br />
57,5 m 22,5 m<br />
3