Resue Mining Stawell - desenvolvimento controle de diluição com EDEV

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11TH UNDERGROUND OPERATORS’ CONFERENCE / CANBERRA, ACT, 21 - 23 MARCH 2011 73
INTRODUCTION 
The Stawell Gold Mines Operation is located 150 km west of 
Melbourne in the Australian state of Victoria (Figure 1) and is 
serviced by the rural town of Stawell with a population of 6500 
people. The mine is owned by NAVCO Australia, a wholly owned 
subsidiary of Northgate Minerals Corporation of Canada. 
Gold was fi rst discovered in the Stawell area in 1853, with 
2.7 million ounces produced in the 65 years to the 1920s. This 
mining was fi rst through alluvial workings, before working 
hard rock sources underground to depths of 700 m below the 
surface 
Modern mining of Stawell Gold Mines (SGM) was 
commenced in 1981 under WMC, with 29 continuous years 
of production winning two million ounces in the modern era. 
Access to the underground working is via 6.0 m × 5.5 m 
decline. Ore is hauled to the surface using 60 tonnes capacity 
trucks, with majority of waste consumed underground as 
backfi ll.
GEOLOGY
The Stawell gold fi eld is located in the western Stawell zone 
of the Lachlan fold belt, which consist of deformed meta-
sedimentary rocks. Three principal rock types make up 
the formation with Magdala Basalt, Albion formation and 
Leviathan formation. Ore from the Magdala and Golden Gift 
orebodies are hosted by subparallel faults and shear zones on 
the western fl ank of the Anticline basalt dome. Fredericksen 
and Miller (2008) describes the Golden Gift ore types having 
typical widths of 8 - 12 m with shoots ranging from 150 m 
to 400 m in strike. Magdala lode mineralisation is located 
in a quartz shear with width of between 0.5 and 10 m, with 
1. MAusIMM, Senior Operations Engineer, Stawell Gold Mines, Leviathan Road, Stawell Vic 3380. Email: Chris.Hamilton@northgateminerals.com.au
2. Senior Technical Services Engineer, Orica Mining Services, Gate 6, Tilburn Road, Deer Park Vic 3023. Email: bonifacio.degay.jr@orica.com
Resue Mining with eDev™ Electronic 
Detonators at Stawell Gold Mines
C Hamilton1 and B Degay Jr2 
ABSTRACT 
Stawell Gold Mines (SGM) is an underground mining operation located in Victoria, Australia. The 
mining method employed is long hole retreat stoping, utilising up and downholes and artifi cial 
concrete pillars. Stawell is currently mining the Golden Gift and Magdala orebodies.
Access to the Magdala and Golden Gift deposits is via 6.0 m wide by 5.5 m high declines developed 
at a gradient of one in eight to one in seven from the surface to a depth of 1500 m, with a planned 
depth of 1650 m. From the declines, cross cutting drives are developed to intersect the orebodies. 
Orebodies in the Gift system are discrete lodes which are generally mined from a bottom up centre 
retreat to minimise geotechnical stresses.
Ore development fronts are currently located between 1000 m and 1500 m below surface, with 
all ore being hauled to the surface using a fl eet of 60 tonne underground trucks. With the use 
of conventional pyrotechnic long period (LP) delays, broken rock of combined ore and waste is 
thrown 10 m from the face and the materials hauled to the surface. The majority of the mullock 
from development is consumed in the underground as backfi ll.
With the use of Orica Mining Services eDev™ Electronic Blasting System for Tunnelling, the 
waste is thrown up to 40 m from the face, while majority of the ore is left 5 - 10 m from the face, 
effectively segregating ore and waste. This enables signifi cant recovery of gold values with minimal 
loss and signifi cantly reduced dilution. By using this technique in ore drives with a 30:70 waste to 
ore ratio, SGM is able to haul 24 000 tonnes less mullock to the surface annually. Resue mining 
is applied to narrow vein headings and gives a 40 per cent grade increase at the faces as well as 
increasing the economic footprint of development. This will also contribute to an improved grade 
profi le for the year from 3.98 - 4.16 g/t Au and allow extra capacity for ore haulage from stoping 
and for milling.
This paper describes the application and the successful blast outcomes achieved using the eDev™ 
Electronic Blasting Systems for resue mining at SGM. Results to date, since commencement 
in March 2010, have been achieving signifi cant benefi ts in terms of ore grade as confi rmed by 
geologists grab sample grades. Face advance have also shown improvement with better breakage of 
perimeter holes giving improved face profi le. These benefi ts are delivering increased productivity 
and safety performance when compared to other resue fi ring techniques.
11TH UNDERGROUND OPERATORS’ CONFERENCE / CANBERRA, ACT, 21 - 23 MARCH 2011
C HAMILTON AND B DEGAY JR
74
economic vertical shoots from 30 m to 350 m in strike. Ore 
mineralisation at the fringes of both the Golden Gift and 
Magdala lode vertical shoots have the potential to be mined 
economically through selective mining techniques such as 
resue mining, while accessing through to the next ore shoot.
MINING TECHNIQUE
Stawell Gold mines use a sublevel uphole retreat stoping 
technique. Approximately 65 000 tonnes are mined each 
month, from stopes and development headings at depths 
of around 1400 m below the surface. Reserves have been 
delineated to around 1650 m below surface. The SGM fi ll 
balance allows all waste mined from development operations 
underground to be consumed within stope backfi lling 
operations.
The stoping method used at Stawell requires the development 
of the tunnels at the base of the ore blocks. These tunnels are 
developed in ground that may have a marginal ore value due 
to the tunnel size including small to large volumes of waste 
and changes in ore geometry. This waste, when mixed with the 
ore, reduces the value of the ore recovered and in cases makes 
it uneconomic and therefore is handled as waste. Figure 2 
shows a typical tunnel with approximately 50 per cent ore and 
50 per cent waste content as determined by the mine geologist 
and a typical pyrotechnic detonator delay fi ring sequence that 
may have been used.
The waste region is shaded dark while the ore region is 
shaded light to enhance clarity. This is applied consistently on 
the succeeding face fi gures. Explosives used at SGM include 
both Ammonium Nitrate Fuel Oil (ANFO) and Orica Emulsion 
products, initiated with Orica Senatel™ Magnum™ primers.
The use of long period delay detonators results in broken ore 
and waste mixed together and heaved 10 - 15 m from the face 
making the segregation of ore and waste during the bogging 
process impossible.
Single pass resue mining using millisecond detonators have 
been practiced since the 1990s with Bock (1996) referring 
to segregation of ore and waste in narrow vein gold reefs in 
South Africa. It is a process of casting the waste in the fi rst 
part of the blast and fi ring the ore in the second part of the 
blast to provide segregation for dilution minimisation. 
SGM recognised that resue mining using single pass resue 
mining had been identifi ed as a way of high grading marginal 
headings while advancing the heading as per the normal cycle 
time. The advantage of single pass resue mining is allowing 
marginal headings to be profi table, as well as reducing cost of 
hauling and treating mullock, especially as the mine continues 
to develop to depth because of signifi cant haulage costs.
Orica have developed the eDev™ blasting system for use 
in civil tunnelling applications to maximise pull, minimise 
blast vibrations and improved perimeter profi le. A secondary 
objective is to have a system that is simple to use and 
comparable with the use of pyrotechnic delay detonators using 
the delay number system. The eDev™ system has proven to be 
benefi cial in resue development mining.
Other alternatives considered
Electronic detonator systems on the market such as Orica’s 
i-Kon™ detonators and Daveytronic™ systems were both 
considered due to product knowledge of these systems at 
SGM from production fi ring. Thesewere both rejected, 
however, due to the unit sale against eDev™ being more 
than twice the price and the user interface of these systems 
not allowing for programming of detonators using a system 
similar to that familiar with operators using nonel systems. 
The 0.1 per cent accuracy of the eDev™ system was considered 
suffi cient against i-Kon™ with accuracy of 0.01 per cent (Orica 
Australia Pty Ltd, 2010, TDS) as minimum fi ring delays of 
15 milliseconds (ms) were used. 
 Use of pyrotechnic long period delays (LP) and millisecond 
series detonators combined were given initial consideration, 
but rejected due a number of factors. The primary concern 
was the infl exibility to change the fi ring sequence at the face 
when the ore profi le in the drive changes or the ability to 
modify fi ring delays to gain best results from fi rings. Concerns 
regarding the logistical and fi nancial burden of maintaining 
stocks of short lead length detonators were also considered.
Constant in-hole delay detonators with surface delay such as 
Orica Excel™ Develdet™ in combination with LP detonators 
FIG 1 - Stawell Gold Mines location in Victoria, Australia.
FIG 2 - Conventional long period (LP) pyrotechnic delay system as 
used on the face.
11TH UNDERGROUND OPERATORS’ CONFERENCE / CANBERRA, ACT, 21 - 23 MARCH 2011
RESUE MINING WITH EDEV™ ELECTRONIC DETONATORS AT STAWELL GOLD MINES
75
have been used in industry to achieve resue fi ring benefi ts. 
These were rejected due to inability to modify parameter 
to improve success. Economic benefi ts from using these 
detonators were not enough to justify a trial.
Traditional resue mining
Traditional resue mining ensures reliable segregation of ore 
and waste in two separate fi rings. However, this method 
slows down the development advance in a heading as multiple 
fi ring events are required for a single round. This would then 
require the next shift to bore and fi re the remaining half of the 
heading. The potential to expose the charge crew to the fi red 
half unsupported ground using this technique is also present 
which contradicts the SGM safety policy of not working under 
unsupported ground.
In short, the best option is to do a single pass fi ring with 
the ability to effectively segregate ore and waste and maintain 
or surpass current advance rates including equal or reduced 
cycle times.
Technical solutions
The introduction of the eDev™ electronic development 
detonators and applying combined Orica and SGM develop- 
ment drill and blast skills and experience such as:
  Locating the burn at the waste portion of the face enables 
the best segregation of the two distinct broken materials 
without loss of ore.
  Sequencing the blast to optimise the advance of the burn 
area, while improving the segregation of the ore and 
waste. The initial section is fi red fast to maximise throw, 
the shot is then paused and the section to be left at the face 
is fi red slowly. A spiralling sequencing has proven that 
a better muckpile shape can be achieved (Degay, 2006). 
Pyrotechnic detonators do not afford suffi cient delays to 
permit use of the spiralling sequence.
  Modifi cation of the delay timing to suit explosive product 
used. A delay of 15 ms in the thrown material was used 
when ANFO was used to charge the holes, while a slower 
delay of 20 ms between holes was used for emulsion fi ring.
  Involvement of geologists to map out the face prior to 
drilling to delineate the contact between the ore and waste 
at the face. The location for the burn will be indicated in 
the waste region, ensuring that the desired fi ring sequence 
can be achieved. Geologists are also required after fi ring 
to clearly identify the boundary between the broken ore 
and waste and to guide loader operators during bogging 
operations. The geologist will paint a vertical line on the 
wall of the drive indicating ore and waste boundaries 
within the muckpile.
  Trials showed that the eDev™ system is at least as fast to 
load and program as the time spent at the face with the 
use of conventional pyrotechnic delays, and averages 
50 minutes. A delay table was created using delay number 
0 - 25. The waste portion utilises delays 0 - 15 while delays 
16 - 25 are used for the ore region. Delay 16 is times to fi re 
one second after delay 15. 
System overview
The eDev™ blasting system consists of the detonators, scanner, 
network tester, blastbox and harness wire. The detonator 
is a fully programmable detonator with 0 - 10 000 ms fi ring 
time with 1 ms increments and 0.1 per cent accuracy. Each 
detonator has unique identity number set at the factory using 
a barcode. The detonators have two way communication with 
the blast box during programming and fi ring times. 
The scanner is used at the tunnel/heading faces to scan 
the barcode of the detonator to allocate a delay number 
and sequence that enables a complex electronic timing to 
be used simply. The scanner assigns times according to its 
downloaded program, or according to rules supplied by the 
design engineer. The two basic rules assign an inter-shot 
delay between detonators of the same delay number, and 
another assigned delay between the last of one number and 
the fi rst of the next number (or the inter-number delay) are. 
This affords a true single-hole fi ring of the entire round. 
Orica describes the scanner as an inherently safe passive 
device where the detonator identifi cation is collected and 
stored without applying any energy to the detonator. Figure 3 
illustrates scanning at the face. The scanner will scan up to 
500 detonators. 
The network tester is another inherently safe handheld 
testing device used to test circuit leakage and continuity. 
The Network tester does not test the functionality of the 
detonators.
The blast box is used to arm and fi re the detonators. 
Detonator data transfer from the scanner to this equipment 
is done via Bluetooth™. Two-way communication to the 
detonators is maintained during the programming stage.
The eDev™ system has been developed to include addressing 
simplicity and ease of use by tunnellers and miners (Simpson, 
2010). A delay table can be generated and loaded into the 
scanners that can mimic the delay numbering of conventional 
pyrotechnic delay detonators from 0 - 15. The delay table 
can be set based on the preference of the end users, to suit 
their particular applications be it resue mining like SGM, 
advance rates, vibration control, over break reductions, or 
combinations of these. 
Results 
Ore and waste confi gurations on a heading or face encountered 
during the trial period at SGM were quite varied. These 
included semi-vertical, vertical, or slanted ore and waste 
split at the face. The face illustrated in Figure 4 used SGM’s 
existing drill pattern and the round was taken over a 4.5 m 
drill length. The fi gure also shows eDev™ delay numbering 
used and fi ring times showing single hole fi ring and a pause 
of two seconds after fi ring the waste region and before fi ring 
FIG 3 - Scanning of detonator barcode and allocation of delays at the face 
using eDev™ system.
11TH UNDERGROUND OPERATORS’ CONFERENCE / CANBERRA, ACT, 21 - 23 MARCH 2011
C HAMILTON AND B DEGAY JR
76
the ore region. The fi ring order adopted resulted in spiralling 
in a clockwise direction and a concentration of the broken 
material on the left side of the drive as shown in Figure 5 and 
the waste segregated ahead of the ore as shown in Figure 6.
Grab samples were taken throughout the muck pile and 
revealed and average grade of 7 g/t Au of ore removed and 
mullock removed at 0.2 g/t Au. This agrees with the predicted 
ore/waste split resulting to a more than 40 per cent increase 
in grade. A geologist painted the wall delineating boundary of 
broken waste and ore.
Figure 7 illustrates a heading where the waste was occupying 
approximately a quarter of the total face. The eDev™ System 
was used in this scenario to provide a real test for the 
shotfi rersusing the scanner. This also gave the opportunity 
to try a modifi ed delay table to improve the segregation where 
the pause was reduced by 500 ms from the initial 2000 ms.
Results as shown in Figure 8 show a clear segregation of ore 
and waste with most of the ore left close to the face with the 
furthest travelling no more than 10 m. 
Grab samples showed the waste portion averaging 0.1 g/t Au 
and the ore having a grade of 4.1 g/t Au.
The most dramatic result occurred for a slanted ore and 
waste split illustrated in Figure 9. The results, in Figures 10 
and 11, show a channel left in the centre of the drive with 
enough segregation and space for the loader to limit mixing 
the two separate materials together during the mucking 
process. Grab samples taken every 2 m along the muck pile 
revealed an average waste grade of 0.1 g/t Au and an average 
grade of more than 25 g/t Au for the ore region.
Of note, there was no attempt to locate the burn in the ore 
region. With the burn located in the waste, the waste material 
is thrown the furthest. Locating the burn at the ore may have 
the potential to have the ore being buried under the mullock at 
the boundary of waste and ore, and the geologist may declare 
the material as waste. In short, a slightly diluted ore is a better 
option than loss of ore.
Identifi ed points of concern critical for success
  The mapping of the position of the ore and waste on the face 
and how it changes through the ‘cut’ is critical to the success 
of the process,
 
FIG 4 - Semi-vertical ore contact heading with eDev™ fi ring times, demonstrating fast initial fi ring of waste in a clockwise spiralling pattern and 
following a pause the stripping of the ore into the void. 
FIG 5 - Blast result for semi vertical ore contact heading in a cross-section using 
spiralling blast delay sequence.
11TH UNDERGROUND OPERATORS’ CONFERENCE / CANBERRA, ACT, 21 - 23 MARCH 2011
RESUE MINING WITH EDEV™ ELECTRONIC DETONATORS AT STAWELL GOLD MINES
77
  increased geology input for mapping of face and muckpile 
split for digging,
  the burn of the round needs to be in the waste and there needs 
to be enough room to allow for the spiralling of the waste to be 
thrown separating it from the ore,
  butts or sockets from the previous shots can restrict position 
of the burn and reduce effectiveness of resue fi ring,
  ensure that rock handling during mucking allows for waste 
and ore dispatch,
  a more complex cycle will require training of charging and 
mucking crews,
  extra cost – detonators cost an extra $400 per round, and
  potentially increased drilling to suit changes in ore 
geometry of face and position of butts in previous face.
Identifi ed improvements to customer needs 
specifi cation
  Increased detonator lead lengths will allow the shot to be 
scanned and programmed from the ground level;
  modifi ed clips to allow one handed or gloved hook up 
which is incorporated on Orica’s next generation of the 
system to be released; and
  testability of detonators before fi ring time, this is again 
incorporated into the next generation of the system.
Demonstrated benefi ts 
The major benefi ts of the resue mining by blasting method in 
development is that ore and waste separation can be achieved 
 
FIG 6 - Longitudinal section result of the blast with semi-vertical ore contact using spiralling blast delay sequence.
FIG 7 - Heading showing ore and waste split with face geometry requiring tight 
mullock removal in bottom quarter of face.
 
FIG 8 - Result in longitudinal section of tight fi ring of mullock in quarter of face.
11TH UNDERGROUND OPERATORS’ CONFERENCE / CANBERRA, ACT, 21 - 23 MARCH 2011
C HAMILTON AND B DEGAY JR
78
reducing the dilution of ore at the headings and improving ore 
recovery where dilution would render the muck uneconomic 
or low-grade. The SGM trials resulted in equivalent to a 
40 per cent increase in haul grade profi le of face dirt, reducing 
in downstream haulage and processing costs. By using this 
technique in ore drives with a 30:70 waste to ore ratio, SGM 
will theoretically be able to haul 24 000 tonnes less mullock 
to the surface annually. Also if the general mine grade is 
improved then overall mined ounces are improved, together 
with the addition a dirt which would otherwise be hauled as 
mullock. This will also contribute to a theoretical improved 
grade profi le for the year from 3.98 g/t Au to 4.16 g/t Au and 
allow extra capacity for ore haulage and milling.
No split fi ring steps are required, which would slow 
down the development rates considerably. There are also 
compromises to safety associated with traditional split fi rings 
due to requirement to re-access a partially fi red face to recover 
the remaining material.
 In terms of advance effi ciency, eDev™ fi red faces showed 
improved perimeter blast performance and measurements 
revealed no butts at the centre of the face, with a maximum of 
100 mm on the wall holes, while butts measured from 200 mm 
to 300 mm on the faces fi red with standard fi ring, indicating 
an improvement on advance effi ciency. 
A time in motion study revealed a charging time of thirty 
minutes and a scanning and clipping time of seventeen 
minutes for a total of forty seven minutes. This is comparable 
to the time consumed with the use of conventional 
pyrotechnic initiation. An advantage of the electronic system 
is that all holes are loaded with the same detonator, unlike 
conventional systems where specifi c delays need to go in a 
certain hole. Therefore, when the detonators are sourced from 
the magazine, there is no problem with ensuring that the mix 
of delay numbers is correct, and there is no chance of stock 
outages of a certain delay number. Extension of lead lengths 
together with modifi cation of clip design will in the future will 
allow for all hole logging to be conducted from ground level, 
increasing utilisation of primary charging functions as they 
are not required during hook-up.
Fragmentation with eDev™ fi red faces had been recognised 
by loader operators to be fi ne and uniform resulting in ease 
and quickness of the bogging/mucking cycle. Load factors in 
trucks and use of the waste as road base are potential benefi ts 
that have not been assessed at this stage.
FIG 11 - Plan view of heading showing ore on the right and waste on the left of the drive of fi ring with slanted ore contact.
FIG 10 - Result heading in longitudinal section showing ejection of mullock along the drive with slanting ore contact.
 
FIG 9 - A slanted ore and waste split at the face illustrating the burn location 
using spiralling pattern to eject the mullock surrounding the burn.
11TH UNDERGROUND OPERATORS’ CONFERENCE / CANBERRA, ACT, 21 - 23 MARCH 2011
RESUE MINING WITH EDEV™ ELECTRONIC DETONATORS AT STAWELL GOLD MINES
79
CONCLUSIONS 
Northgate Minerals Corporation, Stawell Gold Mines and 
Orica Mining Services have worked together to deliver success 
of resue mining by fi ring in development. The knowledge 
of SGM and the expertise and systems of Orica combined 
in this ‘resue mining project’ is able to effectively segregate 
the ore and waste thereby upgrading the ore delivered to the 
mill, allow economic recovery of lower grade headings, while 
maintaining optimum advance and delivering acceptable 
productivity.
Marginal headings by defi nition are unknown and can 
change grade and geology quickly, which can make resue 
mining in these conditions diffi cult. The extra cost of using 
electronic detonators (eDev™) is around $400 per round 
which is more than payed for with the reduction of dilution, 
waste haulage to the surface, improved head grade, increased 
recovery and increased ore haulage capacity not to mention 
the increase in advance.
The bottom line for this exercise will be the reduction in the 
cost per ounce of gold produced at SGM. Given the estimation 
that this method can contribute to upgrading the annual 
production grade forthe year from 3.98 grams Au/tonne to 
4.16 grams Au/tonne, this will be closely monitored.
ACKNOWLEDGEMENTS
The authors wish to acknowledge both Stawell Gold Mines 
and Orica Mining Services Management and personnel for 
their full support on this project.
To the geology department for providing forecasts and 
mapping the faces.
Special acknowledgement is due to Craig Walker for 
approving this paper to be published and to Mike Lovitt for 
his time and help in writing this paper.
REFERENCES 
Bock, I, 1996. Selective blast mining in gold mines, The Journal 
of the South African Institute of Mining and Metallurgy, 
pp 183-186 (The Southern African Institute of Mining and 
Metallurgy).
Degay, B, 2006. i-Kon Eagles nest tunnel design and spiraling fi ring 
technique, Orica internal report.
Fredericksen, D and Miller, G, 2008. Technical report on Stawell 
Gold Mines, Victoria, Australia – Pursuant to National Instrument 
43-101 of the Canadian Securities Administrators, 2:31. 
Orica Australia Pty Ltd, 2010. Technical data sheet, iKon™ Digital 
Energy Control System, Orica Mining Services.
Simpson, L, 2010. eDevtm System user training manual, Orica 
internal presentation.