A Low-Cost, Remotely Operated Mining Method

ROES A Low-Cost, Remotely Operated Mining MethodI Gipps1, J Cunningham2, G Cavanough3, M Kochanek4 and A Castleden5

ABSTRACTROES is a proposed new mining system for underground hard rockmines. Ore is accessed from within a shaft, which is located close to orwithin the stope, and pitched either vertical or within approximately20 degrees of vertical. The shaft is designed to exclude personnel entry soproduction drilling and explosive placement is done using remotelycontrolled or automated machines. Routine remotely controlled survey ofthe shaft, stope back and broken rock within the stope is typically donefollowing each blast. The survey may include excavation geometry, rockfragmentation and geotechnical characteristics. Blastholes are surveyedbefore placement of explosives. This provides mine operators andengineers with real-time data, allowing them to monitor productionperformance and risk factors so that they can make rapid changes asrequired. ROES is designed to apply to open stoping or sublevel cavingsituations either in disseminated, geologically defined, thick tabular ornarrow vein orebodies. The technologies developed for ROES will alsohave potential applications to block caving operations to reduce the riskof frozen ore and poor fragmentation. In a typical sublevel openstope application, ROES will reduce the amount of stope-associateddevelopment by about half and therefore will allow ore to be broughton-stream sooner and at significantly reduced cost. Other savings areexpected to flow from the centralisation of mining activities andoperational data, reduction in mining fleet, reduction in ventilationrequirements, improved occupational safety and reduced mine complexity.CSIRO and Orica Mining Services are developing the requiredtechnology and AMIRA is seeking sponsorship for a project to trial themining method. This paper details the ROES method, expected benefitsand applications and includes typical stope and mining block designs anddesign requirements.

INTRODUCTIONThe Mining Industry is under continuous pressure to improveits performance in areas of safety, cost and productivity. Thishas been achieved in the past by improvements throughmechanisation, scale-up of equipment size and occasionallychanges in mining methods. The ability of underground mines toimprove productivity by increasing equipment size is constrainedby the trade-off between opening dimensions and ground supportrequirements. Another constraining factor is the increasingmining depth resulting in increased geotechnical risk, increasedtravel times and more hostile working environments for people.

To overcome these constraints a considerable effort is beingundertaken by equipment manufacturers, research organisationsand mining companies into the remote control and automationof mining equipment. The mining industry currently has accessto both remotely controlled and automated machinery for stand-alone mining activities. While the take-up of these technologies

is increasing, significant transformation will only come aboutwhen technologies are fully integrated or when a designed-for-automation mining system is introduced. Isolated introduction ofremote control and automation may shift bottlenecks to otherparts of the system.

Mining methods based on block, panel and sublevel cavinghave been attractive for a number of reasons, including their lowoperating costs and high production rates (Brown, 2007).However, caving methods can be problematic when the cavedoes not perform as expected, especially when ground conditionsare not suitable. Issues such as frozen ground, excessive dilutionand poor fragmentation are difficult to remedy once a cave hasbeen initiated. However, sublevel open stoping (SLOS) is moreflexible, allows better control of fragmentation and can bring amining block into production earlier. Unfortunately SLOS hashigher operating costs.

For some time, horidiam or raise mining geometries for drilland blast mining have been proposed and used for shaftexpansion and stoping. For example: Mount Charlotte (Mikulaand Lee, 2000), Mount Lyell (Usher and Kennewell, 1992) andViscaria (Anon, 1983, 1984). These applications used manuallyoperated equipment and therefore risked high exposure tohazardous environments. The protective measures applied tomitigate the risks limit productivity and the minimum shaft size.Mikula and Lee (2000) and others have observed that automationof the process should be possible and beneficial to overcomesome of these drawbacks. Early concepts for automation havebeen proposed and discussed by various people (eg Adams,1996) including equipment suppliers. The Curtin University ofTechnology, Western Australian School of Mines published amasters thesis which examined an application for automatedhoridiam stoping (Fleetwood, 2002). This was proposed andsponsored by the CSIRO. More recently, Dorricott outlined amining strategy using horidiam for underground uranium mines(Dorricott, Derrington and Horsley, 2006).

CSIRO has develop a mining system concept called ROES,which is based on horidiam geometries and aims to operate byremote and automated control. To achieve this, a system isproposed that uses the latest technology that will ultimatelydeliver a level of control and integration unprecedented inmining operations. ROES will be a non-entry mining systemand as such, allows more freedom in stope design than isavailable through conventional horidiam methods. Consequently,benefits of horidiam should be delivered beyond the reduction insublevels. ROES offers the benefits of SLOS at an operatingcost close to that of caving methods when the latter includesamortisation of capital. Compared with caving it also offersdeterministic control of fragmentation, recovery and dilution.CSIRO has worked with other parties, including Orica MiningServices, and the Curtin University of Technology duringthe development of ROES concepts. CSIRO undertook andcommissioned extensive evaluation of the technical andeconomic benefits of ROES including mining block designs fora number of mineral deposits.

ROES SYSTEMROES is a system comprising equipment and software that willbe used for the remote/automated mining of bulk undergroundstopes in hard rock mines and quarries as well as the stripping ofshafts in mines and civil projects. This is a proposed new miningsystem currently being developed to fully utilise the benefits of

Tenth Underground Operators Conference Launceston, TAS, 14 - 16 April 2008 147

1. MAusIMM, Research Stream Leader, Non-Entry UndergroundMining, Minerals Down Under National Research Flagship, CSIRO,QCAT Technology Court, Pullenvale Qld 4069. Email: [email protected]

2. MAusIMM, Research Theme Leader, Transforming the Future Mine,Minerals Down Under National Research Flagship, CSIRO, QCATTechnology Court, Pullenvale Qld 4069.Email: [email protected]

3. Mechatronics Research Engineer, CSIRO Exploration and Mining,QCAT Technology Court, Pullenvale Qld 4069.

4. Research Physicist, CSIRO Exploration and Mining, QCATTechnology Court, Pullenvale Qld 4069.

5. Mechanical Engineer, CSIRO Exploration and Mining, QCATTechnology Court, Pullenvale Qld 4069.

remote and automated machine control without the constraintsrequired by the presence of operators near the active workingarea. Rock fragmentation is achieved using drill and blastmethods and the system includes integrated sensor technologyfor monitoring the mining equipment and stope environment. Asall of the equipment and the processes are controlled remotely, orby automation there is no need for people to be in closeproximity to the associated hazardous activities of mining. Rockis extracted at the base of the stopes via conventional drawpoints. ROES operators and mine engineers will be able to useonline software for design of blasting patterns and assessment ofrelevant mining conditions and monitoring product quality.

ROES is primarily designed as a replacement for sublevelopen stoping (SLOS) with improved safety, lower costs andhigher productivity, but can potentially be reconfigured forsublevel caving (SLC) or used to precondition block cavingoperations. It aims to solve many occupational health and safetyhazards in mining, reduce the operating costs and reduce the timerequired to bring new stopes online. As a result of the lower coststructure, ROES will also have the ability to increase orereserves by shifting lower grade mineralised zones fromsubeconomic to economic.

As shown in Figure 1, ROES requires significantly lessdevelopment compared with conventional SLOS, and theprimary access to the ore for drilling and blasting is vertical (ornear vertical inclined) rather than lateral access. This allowsreductions in total development metres, generally smalleraverage development profiles and more efficient and effectiveuse of development in both tonnes per metre of development andtotal metres required. ROES, as a remote/automated system,will be configured to provide remote controlled and real-timesurvey of the stope so that blasting patterns, blasthole loadingsand stope shape can be modified easily during the productioncycle as required.

ROES DETAILSPertinent aspects of the system are discussed below.

Stope accessThe stope access is provided on two levels: The lower or draw point access is developed to allow mining

of the undercut and extraction of the broken rock from thestope. Current design for the system utilises a draw pointlayout similar to that used for SLOS and provides for

equipment ventilation and access between the draw pointsand ore passes or truck loading facilities. This design wasadopted to increase confidence in using the system but it isexpected that as experience is gained, a modified layout willbe developed that utilises the ROES equipment and shaft todevelop the undercut bells. This will further reduce thelateral development associated with the undercut.

The upper access as currently designed is developed abovethe stope crown pillar and provides access to the ROESraise and for equipment deployment. The developmentprovides for access to the ROES chamber and raise as wellas flow-through ventilation for service and re-supply crews.While the design places the development above the crownpillar, if required this crown pillar could be extracted via amass blast when the stope is near the end of its production.

The development for the top level is likely to be less than thatrequired for a SLOS stope layout because access is required onlyto the raise rather than a number of suitable drilling locations forSLOS. This development will have drive dimensions similar tothose currently in use.

ROES chamberThe ROES chamber will be above the stope and usually abovethe crown pillar to maximise development usage. It will beof similar cross-sectional dimensions required by a raise boremachine but will be longer than a conventional raise borechamber. Again it is likely that once experience has been gainedwith the method, the length of the chamber may be reduced fromthat shown. Once the chamber has been developed then a raise ismined between the ROES chamber and the draw point horizon.

The chamber, as shown in Figure 2, will be equipped with acrane or hoist to lower and raise the ROES modules in the shaftand to move the modules between the shaft and service, storageand resupply areas. The concept shown uses an overhead bridgecrane with a 10 t capacity to deploy and store the ROESmodules. Alternative methods have been considered, includingmonorails, rail tracks, mobile, jib and pedestal cranes. The areawill be laid out to allow easy movement of the modules as wellas re-supply (consumables) and servicing in a safe environment.The chamber will be equipped with a communications nodebetween the ROES modules and the control station and minenetwork if required. Technology is also available to provide thisfunctionality from a distant remote monitoring or control stationvia secure web communication protocol. Examples of this

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SLOS Layout ROES Layout

SLOS Layout ROES Layout

FIG 1 - ROES layout.

capability can be seen in the ACARP sponsored longwallautomation project (ACARP, 2008). This initial chamber conceptis recommended for the trial stages of the development programto provide maximum flexibility. A production version of ROESmay use a simplified concept.

ROES raiseAlthough the raise shown in Figure 2 is located centrally to thestope plan area and pitched vertically, this need not be the case. Itcan be located and pitched as required by geotechnical andorebody considerations. The top of the raise in this example islocated towards the return air end of the chamber and set towardsone side to allow easy movement of the various items ofequipment past each other and around the chamber. The raise isexpected to be 2.4 m in diameter, although final dimensionsabove this size, up to 3.0 m, may be justified. The raise wouldreplace the cut-off slot raise as used in SLOS but a largerdimension (2.4 m to 3.0 m versus 1.4 m to 1.8 m) is required toaccommodate the ROES modules.

ROES equipment modulesThe two main modules deliver drilling and explosives placementwith a third module for survey. All modules have been designedto achieve a loaded weight well below the 10 t rating of thecrane, including the weight of the ropes.

Drilling moduleThe drilling module shown in Figure 3 consists of a drifter andpower pack similar to that used in existing stoping drilling rigs.Modifications will be made to traditional boom, slide and drillcarousel, in order to fit the smaller opening dimensions of theROES raise. Power and water are supplied to the platform fromthe ROES chamber and compressed air is provided locallyfrom an onboard air compressor. The rig carries sufficientconsumables for several rings of drilling before re-supply isnecessary. The system design anticipates that before drillingcommences, hydraulically powered legs extend radially to theraise wall to lock the drill into position. This configuration,together with the more compact design of the boom and slide, ismechanically very stiff compared with existing stoping rigs,

allowing increased collaring and drilling accuracy. The drillcollar will be initiated orthogonal to the shaft walls, providingvery accurate collar location. As the drill progresses in the collar,the orientation of the drifter changes to acquire the desiredblasthole inclination. Once this is reached, the slide stingerextends to lock against the opposite side of the shaft so that all ofthe drilling reaction force is applied directly to the shaft wall.

A specially developed drill control algorithm has beendeveloped and will be applied to maintain the correct force onthe bit as the rock type changes or the bit wears. As a result,the drill will be operating at its optimal performance whileminimising wear, directional drift and risk of stalling.Additionally, any automatic change in the drilling control pointwill be logged and may be interpreted as a change in rock type,thus providing a level of measurement while drilling.


ROES A LOW-COST, REMOTELY OPERATED MINING METHOD

FIG 3 - Conceptual drilling module.

FIG 2 - ROES chamber layout.

Explosives moduleThe explosives module will be similar in size to the drillingmodule. It consists of storage and assembly area for the initiationcomponents, emulsion and sensitiser storage and mixing and therobotic manipulators to load the components into the blasthole.Power and water are supplied to the platform from the ROESchamber and compressed air is provided locally from an on-board air compressor. The rig carries sufficient emulsion andconsumables for a ring of drill holes before resupply isnecessary.

Survey moduleThis carries the instruments to accurately survey the stope voidand map the exposed backs and walls of the stope. This modulecan operate independently of or in conjunction with the other twomodules. Depending on requirements and local conditions, thesurvey will provide accurate dimensional data and possible blockjointing patterns and a measure of fragmentation. Based on thedata provided by the survey module, particularly the shape andlocation of the stope back, it will be possible to redesign the nextblast round to correct any deficiencies with the previous round.Scanning lasers, millimetre radar and photogrammetry have beenproven in similar applications and may be used for this survey.

ROES design

Mine layoutAs the ROES system only accesses the stope from two areas, thetop and base, the mine layout will be significantly simplified andtotal development required will be reduced by up to 50 per centdependent upon the stope height, orebody dimensions andorientation. Figure 1 gives some indication of the difference indevelopment needed for a stope block of three by four stopes,Table 1 shows this comparison numerically. Obviously the totalpercentage saving will depend on the amount of declining andother capital development required per stope, but an overallsaving of 50 per cent in development is certainly an achievabletarget.

Top level developmentThere is a slight reduction in total metres of developmentrequired compared with SLOS because only one drive is requiredper stope versus two drill drives and a ballroom cross-cut forSLOS. However, ventilation development remains similar so thatin the layout shown, a saving of about 20 per cent is possible forthis level.

SublevelsROES requires no sublevel development so that each sublevelremoved is a saving of the total development for that level.

Extraction levelROES is shown as having the same development for this levelas the SLOS system. If the draw point cones were to bedeveloped using the ROES drill and blast platforms, then someminor savings on this level would also be possible.

RaisingROES requires slightly more vertical development comparedwith SLOS because the chamber is placed above the crown drive.In addition to the extra length of raising, the ROES raise islikely to be of a greater diameter than conventional existing slotraises.

Drilling and blastingThe ROES system will provide advantages in both drilling andblasting.

The drilling advantages arise because: The drill module is held rigidly against the surface of the

raise, reducing the opportunity for reactive forces to causemisalignments in drill collar location and/or hole direction.

ROES collars orthogonally into a machined surface (raisebore hole) before slowly acquiring the desired hole angle andthis greatly improves collar location and accuracy. Collarslippage is expected to be nil.

The axis of the drill slide can be accurately located in bothposition and orientation allowing the hole to be drilled in theexact location and in the orientation it was designed.

Where the ROES raise is within the orebody, the maximumdrill hole length is reduced and drilling occurs in the planethat has the smallest dimension.6

Improved drill accuracy should allow a reduction in totalholes, total drill metres and explosives (and explosiveconsumables) as less allowance will be required for holedeviation. This also leads to improved control offragmentation.

Initial calculations show that ROES requires slightly moretotal drill metres (zero to five per cent) for the same powderfactor than would be used for SLOS. This is a result of theshorter holes being slightly less efficient in coverage of thevolume to be blasted. These calculations, however, did not takeinto account the potential reduced powder factor as a result ofmore accurately placed drill holes.


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6. This compares with SLOS where the aim is normally to maximisethe height between sublevels (and hence blasthole length) to reducedevelopment requirements.

Item ROES SLOS stope heightStope height (m) Variable 100 m 150 m 200 m 250 mTop level (m) 1500 1800 1800 1800 1800Sublevels (number of) 0 1 2 3 4Distance at 1800 m 1800 3600 5400 7200Draw points (m) 1800 1800 1800 1800 1800Total (m) 3300 5400 7200 9000 10 800Saving with ROES (m) 2100 3900 5700 7500Saving with ROES (%) 40% 55% 62% 70%

TABLE 1Development metres comparison.

Blasting advantages arise because: No blasting energy is required to throw the rock clear of the

face as broken material falls clear of the face that is beingworked.

The stope can be fired as single rings, multiple rings or as amass blast (as can SLOS stopes).

As no broken material will remain against the blast face, itmay be possible that less material is required to be removedfrom the stope compared with SLOS before it is practical tofire the next ring blast. This may be of benefit where it isdecided to maintain ore within the stope for wall supportuntil the final extraction sequence.

Again initial calculations show a slight increase in blastingconsumables (detonators and boosters) as a result of the shorteraverage drill hole length leading to more holes. This may benegated by reduced powder factor with improved drill holelocation.

VentilationROES also benefits the mine in other ways as a result of thereduced development and reduced complexity of the miningoperation. One of these areas is mine ventilation, whereventilation requirements are reduced and simplified comparedwith conventional SLOS because: reduction of sublevels reduces ventilation requirements for

drives by approximately 40 to 70 per cent, having fewer openings into stopes with no sublevel openings

and only a single top level opening reduces short circuitsthrough stopes,

the reduced complexity of the ventilation system means lessmanagement will be required to ensure that re-circulation isnot occurring, and

there will be reduced exposure of people to contaminants thatmay be flushed from stopes into the ventilation circuit.

Dependent upon the amount of air required to ventilate stopes,the potential to save over 50 per cent of ventilation operatingcosts exists and significant reductions in capital cost may beavailable. In most mines with reduced openings into the stopes,very little stope ventilation air will be required. Also, ventilationair required for service crews does not need to pass through thestope, making control easier.

Stope fillingThe ROES system provides the potential for improvements tothe stope filling. In the ROES stope it should be possible totight fill against most of the crown as the fill can be placedthrough the raise, with the fill rising up the arched backs of thecrown pillar and into the raise. The placement of dry fill throughthe raise borehole should also be safer than traditional practicevia a drill drive. Large machinery cannot fall into the stope andthe ground from which the equipment is operating should bemore stable as it is above the crown pillar, not adjacent to theblasted void.

Stope designThe design of ROES stopes is reasonably flexible as the stopecan accept several shapes and can be varied to follow theorebody profile or grade contours.

While the early diagrams indicate a rectangular shape to theROES stopes, they need not be restricted and will conceivablymigrate to other shapes as the system is introduced and minesbecome more confident about the method. Suggestions for otherstope shapes are shown below. Various shapes considered to dateinclude the following.

Rectangular (square)This shape has been adopted for the initial feasibilitycomparisons with SLOS stopes during the early stages of ROESdevelopment. It allows easy comparison with the SLOS system,which currently utilises square or rectangular plan shapes.

In an area where square or rectangular stopes are optimal thenthe ROES stopes may be arranged as shown in Figure 4, whichshows a four by three stope block. Note that the ROES chamberlayout shown has a single pass airflow so that mine staff areisolated from air that leaves the stope. This is particularly usefulfor uranium mining.

Hexagonal and circularIn areas where cemented fill is to be used, the stope may have ahexagonal or circular shape to improve drill hole efficiency andreduce exposed surface areas of fill in adjacent stopes (seeFigure 5). In areas of low grade and in the absence of cementedfill, rock pillars are left between stopes and the ROES stopeshape could be circular to maximise drill hole efficiency anddeliver improved geotechnical stability, or elliptical to matchground stress directions (Figure 6).

InclinedThe stope does not need to be vertical as the raise can be pulledto match the ore orientation. The maximum inclination wouldcurrently be limited by the rill angle of the blasted materialwithout modifications to the draw point layouts (see Figure 7).



FIG 4 - Square/rectangular stopes.

FIG 5 - Hexagonal stopes.

FIG 6 - Circular stopes.

ShapedThe ROES stope does not need to have a constant plan area, orbe vertical, as ground can be made or lost as required duringthe mining of the stope (as shown in Figure 8) to meet anycombination of grade contours, geotechnical or infrastructureconstraints. Since the location of the drilling rig and the locationof the collar and its direction are also known very accurately forROES, the drill pattern can easily be changed from the controlstation as information is updated.

The design of ROES envisages that the drill holes willnormally be subhorizontal but the angle from the horizontal canbe varied as required and this allows the stope to either make orlose ground to match the desired stope profile. This is achievedby varying the amount of subgrade drilled, or preferentially bychanging the angle that the drill holes intercept the profile shape,ie changing the amount of dump angle on the drill holes.

Figure 9 shows how by varying the declination of the hole itwould be possible to change the plan area of the stope and makeground. Increasing the dump angle (angle from the horizontal)should increase the gain angle by one degree for every onedegree increase in the dump. As the initial design of the drillmodule allows angles of up to 40 degrees from the long axis of

the machine, it should be possible to gain ground at a rapid rateby decreasing the ring burden at the toe by increasing the dumpangles with successive rings until the new profile has beenreached. It should be possible to expand the plan area byachieving a gain of 30 - 40 degrees off the shaft axis. This isenough to allow the stope wall angle to approach the rill angle ofthe broken material.7

There can be several reasons for shaping stopes. These couldbe to follow geological or grade boundaries or to mine throughareas that have existing development that intrudes through the


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7. An angle lower than the rill angle could be obtained but would not bepractical unless a modified extraction layout was developed.

1

4

ROES TM shaft

Ore outline

5

3

2

1. Dump angle to arch backs forgeotechnical reasons.

2. Dump angle required to make blastholesperpendicular to required stope outlinemaking ground.

3. Dump angle with added safety margin toallow for some loss of ground duringblasting.

4. Ground to be made to match ore outline.5. Safety margin to allow for any losses.

1

4

ROES TM shaft5

3

2

1

4

ROES TM shaft5

3

1

4

ROESTM shaft5

3

2

FIG 9 - Making ground.

FIG 8 - Shaped stopes.

FIG 7 - Inclined stopes.

stoping area. This development will intersect ROES blastholeswith the potential to cause shadows or sterilised ore, as shownin Figure 10. With the reduced development resulting from theROES system there are fewer opportunities to locate a drillingrig close to the intrusive development except from the ROESraise. A first solution might be to utilise the intrusive drives todrill the shadow zone; however, if these drives requirerehabilitation before safe entry can be obtained then it may bepreferable to avoid that task and fire the entire stope from theROES raise. The various ways this can be achieved are shownin the following diagrams and discussion.

Managing intrusive developmentOne of the perceived problems with adoption of a ROES systemis that first applications will probably occur in mines using SLOSand the first stopes mined are likely to occur in areas withexisting sublevel development. The problem then becomes thatsome of the ROES stopes may have existing development driveswithin the stoping area that will give rise to shadows that cannot be accessed by the standard ROES drill pattern. While theoccurrence of narrow natural voids can be accommodated by thedrilling and explosive loading modules, these development drivesare too large to be managed in a practical way. The magnitude ofthe challenge is determined by: the location of the drive relative to the ROES shaft, the location of the drive relative to the edges of the stope, and the size of the drive relative to the drill pattern spacing and

burden.The main approaches to avoiding a significant loss of ore as a

result of existing development causing drill shadows can bedivided into the following categories: redesign of the stoping block and individual stopes to

relocate the development in a suitable position relative tostope boundaries and the stope raise,

access the drive and use it for some drilling, leave ore grade material in place, and reconfigure the ROES rings to drill the shadow from above

and below.

Redesign stoping boundariesIf possible the stopes and stope block should be redesigned so that: The stope is designed to ensure that the drives are as close as

possible or coincident with the boundary of the stopes andrunning parallel to the boundary. This minimises the size ofthe shadow at it may be decided to leave the relatively smallremnant material at the edge of the stope.

The stoping layout is designed so that the ROES raisepasses through the drive. As it is possible to locate theROES shaft non-central to the stope, this offers some scopefor avoiding the creation of a shadow.

Access the driveThis is a solution provided that the drive is in good condition andcan be easily accessed and has not been already isolated from themine access development. This enables conventional stopedrilling rigs and explosive loading equipment to access the driveso that they can drill and fire material that would otherwise beleft behind. The length of the drill holes in the ROES ringscontracts and re-expands to cover the rest of the material.

However, if the drive is in a remnant part of the mine the costsof doing this may not be justified, particularly if the material islow grade. This solution will probably also require rehabilitationof accesses leading to the intersecting-stope drive. Figure 11shows the drill pattern around a rehabilitated drive. Note that inorder to ensure safe access, explosive loading from the drivewould need to be done prior to firing at least three ROES ringsbelow the drive. Hence this system would probably require firingof at least five rings in combination, ie at least three ROES ringsbelow the drive plus two that intersect it in a sequenced firing.

Leave grade material behindThe material within the shadow and some material both aboveand below would have to be left in place so that ground could belost and regained around the shadow area while forming a bulgeinto the stope (as shown in Figure 12). This provides areasonably easy solution if the material does not have a highvalue and is adjacent to the edge of the stoping region; however,this solution may not be possible if adjacent areas are of fill asthere would be insufficient strength to hold the bulge in place.

Reconfigure ROES ringsThe flexibility of the ROES system allows the material in theshadow to be accessed by modifying the ring drilling parametersand design. There are two main solutions required: where drilling and firing occurs a single ring at a time, and where drilling and firing is on multiple rings (or mass blast).



FIG 11 - Rehabilitated drive.

FIG 10 - Drill shadows.

To demonstrate the ability of the ROES system to overcomethis issue an example is shown based on assumed designparameters of: spacing and burden at stope boundaries are:

4 m spacing between holes, 3 m ring burden, and

dump angle on holes from the horizontal of 15 degrees down.When the stope is mined by drilling and blasting a single ring

at a time the hardest problem is presented. The constraint of thesingle ring at a time firing being that additional rings can not bedrilled through the plane of standard rings, making it harder toaccess the material within the shadow. Figure 13 shows apotential solution by modifying the drilling as the stopeapproaches the development, causing the drill shadow. Thefollowing modifications are made:

The inclination of the holes within a ring is adjusted from15 degrees down to flat or inclined slightly upward in theregion of the development. The ring spacing at the collars ofthe hole decreasing to half that at the hole toes so that thering burden remains constant at the toe location.

Just below the base of the development the rings are drilledhorizontal or with a slight upward inclination to accessmaterial behind the drive.

At the level of the drive the rings are drilled horizontal. Above the drive one or two shortened rings are drilled

horizontal or on a very low downward inclination to createthe cone.

From further above the drive, the rings will move to a steepdownward inclination to pick up material within the drillshadow.

Each subsequent ring will be drilled at a lower inclinationuntil the standard inclination has been reached. Again thecollar burden between the rings is half that of the ring burdenat the toes until the standard inclination has been achieved.

In practice the ring locations would be designed to minimisethe number of rings that would occur within the elevation of thedevelopment and the amount of inclination and extra dump onholes in rings around the development would vary with thelocation of the drive and its height relative to the ring burden.

Note in Figure 13 the light blue rings at the base and toprepresent rings drilled on the standard ring pattern. The purplerings represent drill patterns where the rings have been adjusted.

Note that this ring design is provided to show that it is possibleto modify rings to overcome shadows and does not represent anoptimal ring design.

Where multiple rings are fired in combination it is possible tointerweave the rings to improve the solution. In this case, shownin Figure 14, one extra part ring is drilled from below and oneextra part ring is drilled from above the drive to intersect materialin the shadow. As the rings are fired in multiples it is possible tofire the lower purple ring in combination with the three ringsabove and the upper purple ring in combination with the ringsbelow.

Stope block and development layoutOne of the advantages of the ROES system is that the top lateraldevelopment is not required to be coincident with the top of thestope. It thus becomes possible to handle rapid variations in thethickness of the ore zone by varying the thickness of the crownpillar. As shown in Figure 15, as the top level of the ore varies


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FIG 14 - Multi-ring firing.

FIG 13 - Single ring firings.

FIG 12 - Loose ground.

the development can remain on one level by varying thethickness of the crown pillar for individual stopes. The onlyadditional cost of this approach is due to the additional metres ofraising for some stopes. This compares with SLOS where anumber of options might be used, including an additionalsublevel, acceptance of additional waste within the stopeboundaries (dilution), loss of economic grade material that mightbe above the drill horizon. For orebodies that are close to thesurface or near the base of an open pit, it is possible to deployand service the ROES equipment from the surface while stillleaving an intact crown pillar.

A significant advantage of this ability to vary stope heightwithout changing the development levels is that it then becomespossible to delay making decisions about the economics ofmining marginal grade material until much later in the miningprocess, ie when the material is in fact being mined. Wheremineralisation slowly declines with elevation it is possible toplan development well above the stope and cease drill and blastonly when the actual grade falls below the cut-off grade. The costof this extra economic freedom is only the additional metres ofraising undertaken.

Stope schedulingStope scheduling becomes slightly easier using ROES than forSLOS as the removal of all sublevels and the placement of thechamber and access above the crown pillar means that the stopesequence is not constrained by the requirements of access to themiddle rows of stopes if the stoping block is more than twostopes wide. Additionally, less development needs to be sacrificedas each stope is completed for ventilation and services.

The stope can, if required for geotechnical or productionreasons, retain most of the blasted material to act as support forthe walls up until the final extraction sequence, as the blast face

is advancing vertically not horizontally. Only sufficient ore mustbe extracted between blasts to allow for expansion of the nextblast.

Hence for most of the stope life, the height of exposed wallcan be less than for SLOS stopes.8

ProductionOf major concern for the introduction of any new mining methodis the likely production rate compared with existing systems. Aspart of the detailed feasibility work undertaken for ROES astudy was undertaken to model the performance of the ROESstope and to compare these results with the SLOS stopes from anoperating mine.

It was determined that for a single stope, the drilling rigdedicated to the stope spent 85 per cent of its available timedrilling, six per cent of its available time travelling (up and downthe shaft) and the remaining time was spent waiting for blastingto occur. This utilisation was significantly above that achieved byconventional stoping rigs, principally because the machine spentless time travelling between the various sublevels within a stope.A similar modelling of the explosives module showed that it wasrequired for 14 per cent of the time loading, five per centtravelling and 80 per cent free, indicating that it would bereasonable to expect one explosive module to service four stopesat a time, while still allowing time to travel between stopes. Thestudy also indicated that a single ROES drilling module wouldbe able to supply significantly more than the daily scheduledproduction from the stope for the comparison mine. In fact thedrilling and blasting rate was in excess of twice the scheduledproduction rate for a stope.

TECHNOLOGY DEVELOPMENTThe ROES technology development program is designed tominimise costs, time and first-trial risks. It will use existingequipment to the fullest extent possible to deliver confidence and



FIG 15 - ROES generalised layout.

8. This may be particularly important when extracting against a filledstope.

maintain compatibility with existing mine equipment fleets.However where necessary, it will also use recent advances incommunications, remote and automated equipment control,sensing and machine guidance which have been proven in otherprojects undertaken by CSIRO and Orica Mining Services. Manyof these technologies have been commercialised and some are inthe commercialisation stage. Technology to remotely placeexplosives is currently being developed by Orica MiningServices, with assistance from CSIRO. This will be the thirdgeneration of the remote placement technology. To minimise therisk during trials, the trial stope will be designed so that it iscompatible with SLOS layouts so that mining can revert easily tosublevel stoping methods at any time during the trials if required.This eliminates the risk of sterilising ore and minimises sunkcosts during the trial phase. Conversely, it will not use anoptimum design for ROES. Sponsorship for a mining trial iscurrently being sought through AMIRA International.

DESKTOP STUDIESOver time, a series of desktop studies have been undertaken tohelp develop the concept. The first of these was a Masters Thesisby K Fleetwood in 2002 (Fleetwood, 2002), this was a majorstudy undertaken to look at all aspects of the system includingrock mechanics, stope scheduling, design of the draw point andtop levels, ring design and timing of activities. This study wasbased on a standard mine design layout of a 12 stope (three byfour) block. Three subsequent major studies have since beenundertaken. While the results of the studies remain confidentialto the companies involved they clearly demonstrated that ROESoffered significant cost reductions over conventional SLOSstoping. In the first of these studies, undertaken by WASM at therequest of CSIRO, operating savings of six per cent, 14 per cent,16 per cent and 20 per cent per tonne were shown for ROEScompared with SLOS. Subsequently CSIRO has undertaken withtwo mining companies studies showing savings of approximately20 per cent for ROES, compared to SLOS, for blocks of stopes.One of these studies included detailed modelling of stopeproduction based on typical drilling performance achieved at themine and scheduled production rates from stopes.

SUMMARY OF ROES ADVANTAGESEconomic and safety advantages of ROES will arise from: No one working near the openings into open stopes all

equipment can be housed, serviced and launched from theROES chamber or from the surface if the raise opens to thesurface for shallow orebodies.

Reduced lateral development length, leading to: improved safety with reduced exposure of operators to

the development cycle, reduced costs with lower capital and operating costs, and reduced time to bring ore production online.

Improved drill/blast performance: more accurate hole collar location, shorter and more accurate holes,

improved fragmentation control, and simple real-time control of blasting pattern during the

production cycle. Reduced ventilation requirements due to:

less development to ventilate; no through stope ventilation required to provide

ventilation for stope drill and blast crews; and smaller, simpler ventilation circuits with reduced risk of

short circuiting. Potential to improve geotechnical performance due to:

improved ability to arch the stope backs, and improved ability to increase wall support (broken rock to

support walls). Improved stope backfilling due to:

fewer entries into stope, able to arch stope crown, and able to close fill to stope crown through ROES raise.

Improved ability to monitor and hence control stopeperformance: real-time acquisition of survey and equipment data

during operation; and opportunity to integrate control of mining production

with other operational tasks, including processing.

REFERENCESACARP, 2008. Longwall automation web site. Available from:

.Adams, M, Hannigan, T, Horsley, T, Cunningham, J B, et al, 1995 - 1997.

Personal communication.Anon, 1983. Viscaria A new copper mine in Northern Sweden, Mining

Magazine, October:226-233.Anon, 1984. High grade spurred Viscaria development, Engineering and

Mining Journal, 185(2):33-35.Brown, E T, 2007. Block Caving Geomechanics, The International

Caving Study, second edition (Julius Kruttschnitt Mineral ResearchCentre: Brisbane).

Dorricott, M, Derrington, A and Horsley, T, 2006. Underground miningstrategies for uranium deposits, in Australias Uranium 2006 Program/Abstracts, pp 19-20 (The Australasian Institute of Miningand Metallurgy: Melbourne).

Fleetwood, K G, 2002. The development and evaluation of the automatedhoradiam stoping method, Thesis, Master of Science by Research Mining Engineering, Curtin University of Technology, October.

Mikula, P A and Lee, M F, 2000. Bulk low-grade mining at MountCharlotte Mine, in Proceedings MassMin 2000, pp 623-635 (TheAustralasian Institute of Mining and Metallurgy: Melbourne).

Ulrich, W, 1983. Critical Heuristics of Social Planning, second edition(University of Chicago Press: Chicago).

Usher, R E and Kennewell, G J, 1992. Evolution of mining and currentpractices in the Prince Lyell orebody, Mount Lyell Mining andrailway Company Limited, in Proceedings Fifth UndergroundOperators Conference, pp 37-46 (The Australasian Institute ofMining and Metallurgy: Melbourne).


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A Low-Cost, Remotely Operated Mining Method