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SYNOPSIS
This paper describes bard and pillar trackless mining at
depths of 1 DOOm and deeper on the Merensky reef horizon.
INTR UCTI
Impala Platinunl Limited, Implat's major operational asset, has
its primary operations concentrated on the Impala lease area
on the Western limb of the world-renowned Bushveld
Complex, near the towns of Phokeng and Rustenburg in
South Africa's North West Province. The mining lease
covering approximately 27 500 hectares.
Mining at Impala focuses primarily on two reefs, Merensky
reef and UG2 Chromitite layer, a well- layered ultramafic to
mafic igneous succession of the 2 000 million year old
Bushveld Complex.
INTRODUCTION C T.1
Thirteen operational shafts deliver ore to two reduction plants. A total of 16m tons per annum of which the TM3 bord and pillar operations delivers 11 % of the total volume of the mine.
12 Shaft's Merensky ore reserve block that has been mined conventionally, is being depleted rapidly. To maintain the production volume at the shaft, it was decided to mechanise the ore reserves below the bottom level of the shaft, as the channel width lends itself to trackless mining.
INTR UCT~ CONT.2
An ore reserve block below the deepest level, 20 level, on the
down dip side was available for mining, however the development
rate for opening up ore reserves for conventional mining did not
make any contribution to the short term mining plan.
An opportunity arose whereby the production challenge could be
met by implementing a bord and pillar TM3 mining method.
Feasibility studies pointed out that bord and pillar TM3 mining
could be mined at an acceptable profit margin in that specific ore
block. Mining cornmenced in late 2003.
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SAFETY
l.T.I.F.R. per Million Man Hours
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o Feb-05 Mar-05 Apr-05 May-05 Jun-05 Jul-05 Aug-05 Sep-05 Gct-05 Nov-05 Oec-05 Jan-06
SAFETY
• Safety is a priority and it is our goal to ensure that Impala's
safety performance, which currently ranks among the best in
South Africa, at least matches best international underground
mining practices .
., A behaviour - based safety observation process aimed at
eliminating actions that could cause injuries to employees,
has been implemented. This process creates commitment to
working safely.
• In line with a set of Best Practice safety rules, each operating
division introduced a set of five platinum rules to address
critical risks.
• The Lost Time Injury Frequency Rate for the current Business
Plan is 3.39 per million man hours worked.
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1'
INING LAYOUT
The trackless section is situated on the deepest level of 12
shaft, 1000m deep, with a strike distance of 1.5km from the
shaft structure in a southerly direction.
Access to the section is through a twin haulage configuration:
A men-and-material haulage with man carriages, and an ore
transport haulage with a 20Dt electric overhead train.
All large equiprnent and machinery is dismantled or split on
surface and re-·assembled on 20 level station.
1J
1Nl LAYOUT CONT. 1
The conveyor belts are not fire-retarded, but equipped with a
automatic Fogtech fire suppression system on all the dip belt
drive units. The remaining strike belts have been equipped
with fire hydrant units, 30 meters apart.
A dip conveyor belt has being installed on true dip, on reef
and essentially in the middle of the ore block, within reach of
the development ends. A 2.2m/s 1050mm steel core conveyor
belt tips into a silo which feeds into a second silo via a
second dip conveyor belt loading into the 200t electric
overhead train, the final tram to the shaft.
c
1Nl LAYOUT C T.2
Six strike conveyor belts tip onto the dip conveyor belt. Three from the north nlining direction and three from the south mining direction.
These are 1.5m/s 1050mm canvas conveyor belts with Rammer Z250 telescopic hydraulic hammers on each loading point at the face. The dip spacing between conveyor belts is 154m.
8elt forward moves are planned to maintain a maximum of 75m from the working face to the loading point.
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I I LAYOUT T.3
Strike belt sections
A strike belt section consists of 8 X 12m bords. Four X12m
Bords are up dip from the strike conveyor belt and 4 X 12m
bords are down dip. The 6m wide strike belt is drilled by a
conventional hand held rock drill crew and cleaned by an
LHD.
A strike conveyor belt section forms one unique mining unit
with the following allocated to that unit: a cost code, a
workgroup and trackless equipment.
The total TM3 section consists of six strike belt sections.
The development comprises of 3 down dip bords, two 12m
down dip intake airways and one 6m down dip conveyor bord.
cc-
ININ yeLE
• Two 8 hour shifts per day, a night shift and a day shift.
• Eleven day fortnight.
ID On average 23 days per month.
• 274 Day's per year.
• End of morning shift surface centralized blasting.
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PR UCTIO
Planned production for a strike belt section
" 2100m 2 /month.
• 12500Umonth.
Planned production for the total bord and pillar section.
" 12600m2 /month.
" 75000t/month.
On reef development to open up new bords.
.. 145m linear in the 3 development on reef bords.
" 8000Umontlh.
PIRODUCTION T. 1
Mining parameters
A stoping width of 1.9m is being achieved currently with a relative density of 3.05t1m3 and a head grade of 3.70g/t.
The drilling pattern is a burn cut of 50cm horizontal and 50cm vertical, addingl up to + 89 holes per face. Three meter effective drill holes are drilled and loaded with 4.5kg of Expanfo 200 alllmonium nitrate fuel oil explosives per hole. The bottom holes are loaded with Explogel V10 watergel exp~osives. ThE~ initiation system is a 7.8m 3800/3800 millisecond Dual Detonator Primadet nonelectric initiation system.
TI'
PR UCTI CONT.2
SUPPORT
Support is provided by 4m x 12m yield grid pillars with 12m x
36m stable barrier pillars along the conveyor belts. In-stope
support is 1.5m hydra bolts on a 1.5m x 1.5m pattern.
Installation is done by a conventional hand held rock drill
crew, supporting two bords per shift. Extra support in the form
of shot crete and long anchors is installed at geological
features, low "C~" rating or poor ground conditions.
FLEET
et The trackless fleet per conveyor belt section consists of the
following:
et 1 Drill Rig. (Axera 126 LP Single boom HLX5 Drifter.)
• 2 LHD's. (EJC 115)
• 1 Utility 'Vehicle. (GHH)
• A swing LHD and Drill Rig is available per 3 belt sections for
replacement during scheduled maintenance.
• The developrnent section consists of:
• 1 Drill Rig. (Axera 126 LP Single boom HLX5 Drifter.)
o 2 LHD's. (EJC 115)
et 1 Utility Vehicle. (GHH)
1];
FLEET T. 1
The total fleet for this TM3 section is as follows:
• 10 Drill Rigs. (Exera, single boom, HLX 5)
• 18 LHD's. (EJC 115)
• 5 Utility Vehicles. (2 Fermel and 3 GHH)
• 2 Supervision vehicles. (Scorpions)
• 1 Breakdown Vehicle. (Toyota)
The total fleet is being maintained by Sandvik Mining and Construction (SMC) based on a labour hire contract basis. Parts and consumables are financed and managed by the Mine.
LABOUR COMPLEMENT
The total labour complement for this bard and pillar mining
section, including the logistic complement but excluding the
service departrnents, is listed below.
• Mining, Stope:
• Mining De,,:
CD Mining Sectionals:
• Engineering:
• SMC:
• TOTAL SECTION
TI:
AT WORK
224
38
36
128
44
470
EFFICIENCIES
Efficiencies calculated, based on the production achieved
during the period July 2005 to January 2006 are below.
• LHD. (EJC 115)
• Drill Rig. (A.xera 126 )
e Average Face Advance.
et Average Advance Per Blast.
e Tons per total employee.
• Average on reef development.
6550tlmonth
2210m 2 /month
26.4m/month
2.8m/blast
185/month
194.6m/month
EFFICIE IES T. 1
Fleet efficiency for two full 8 hour shifts, including traveling
time to work place:
• LHD. 85 % Available and 74% Utilized.
• Drill Rig utilization, on percussion hours only.
4& Drill Rig. 92% Available and 35% Utilized.
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'T NAGE BUILD UP
Important points to mention which contribute to the success of
achieving the planned build up:
ID The drill ri~) determines the rate of mining and the mining
cycle.
Et The minin~) cycle must be understood and communicated between shifts ..
• Each strike belt section must understand their daily call
and aim to achieve that call.
4) Mining supervision must concentrate on the utilization of
the available fleet to ensure that production is being
achieved.
• Equipment utilization per shift must be maximized.
u:
NCLUSIO
The trackless mining section's total shaft cost per Kg PGM's
has proved to be competitive with other conventional shafts
on Impala. However, the wide channel width in this area that
has made trackless mining possible, is localised and is not
present at other Impala Shafts, except for a small section at
no. 14 Shaft.
Acknowledgement:
The author wishes to thank the management of Impala
Platinum for their permission to publish this paper, as well as
their commitment to better and safer mining.
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