UNDERGROUND EXCAVATION Alternative …

1 The Redpath Groupin a recent paperstated: Through technology andinnovation advancements, the opportunityto implement Alternative EXCAVATION methods inthe mining industry is becoming a reality. If arobust and well- managed feasibility review ofalternative EXCAVATION methods is undertaken,we are able to pursue the various opportunitiesof mining through poor ground conditions andsubsequently deliver economical solutions forresource development that may otherwise beunviable. The company recommends that thefollowing list of technical and performancefactors should be considered beforeimplementing any Alternative excavationmethod:nIs the method compliant with local legislationand standards?

2 NDoes the method of EXCAVATION improvesafety?nWhat productivity can be achieved?nAre the necessary skills available in thelocality to implement the EXCAVATION method?nCan a workforce be trained in the requiredskills to implement the alternativeexcavation method?The company adds: Once consideration isgiven to these technical and performancefactors, the economics of the solution must bereviewed and whether the implementation of analternative EXCAVATION method will delivernecessary the value to undertake thedevelopment of the resource. It is only throughthe willingness to explore alternatives to thenorm that advancement can be made andinnovation for the betterment of the industryimplemented.

3 Alternative EXCAVATION methodsOver the years, Redpath has undertaken amultitude of tunnelling and undergroundexcavation projects for civil and mining clientsboth domestically and internationally. Theseprojects have been undertaken through varyingstrata conditions with differing excavationmethods in remote locations and in centralbusiness districts. With the recent turbulentnature of the global financial environment,project drivers have been challenged with theemphasis being placed on methods to gain earlyaccess to orebodies, rapid developmenttechniques, lower capital costs and reducedlabour requirements to name a number of mining companies seeking toachieve these objectives have commenced thejourney to better understand the operationalconstraints.

4 Challenges and opportunities thatmay be available with the use of alternativeexcavation development of safe and effectivealternative EXCAVATION methods that comply withboth domestic and international mininglegislation and regulatory requirements is achallenge the industry needs to embrace. Giventhe current cost pressures being faced by theAustralian mining industry particularly, somealternative EXCAVATION methods offer thepotential for longer term sustainability and rapiddevelopment of recently work has been undertaken on aproject that challenged the norm andimplemented an Alternative EXCAVATION methodwith the use of an excavator with a rotatingdrum cutter head.

5 Completed noteworthyprojects that have included varying excavationmethods in remote and challengingenvironments include:nGhaghoo diamond mine sand tunnel,Botswana Gem Diamonds. Construction of adecline through the sands of the Kalaharidesert in Botswana (see this month sOperation Focus for more details)nOk Tedi Mine Drainage Tunnel, Papua NewGuinea Ok Tedi mining Ltd (OTML).Construction of a km tunnel for thepurpose of dewatering the open pit mine. Themain tunnel development was driven by a diameter tunnel boring machine (TBM)nKestrel Mine Extension, Australia KestrelCoal. Drift development using modifiedroadheaders supported by a sliding floornCarborough Downs Drift Development,Australia Carborough Downs CoalManagement.

6 Construction of 3 drift entriesthrough drill and blast excavationnMechanical EXCAVATION with TBM of both theconveyor drift and transport drift at AngloAmerican s Grosvenor and GrosvenorThe following summarises project details firstpublished in the12th AusIMM UndergroundOperator's Conferenceproceedings and the14thCoal Operators development of two drift access tunnelson the Kestrel Mine Extension (KME) project inEmerald, Queensland, Australia was completedUNDERGROUND EXCAVATION80 International mining | SEPTEMBER2014 Alternative excavationPaul Moore reviewssome projects andtechniques forhorizontal minedevelopment, plusprovides an update ontwo new verticalexcavation toolsRedpath s current scope of work at PT FreeportIndonesia covers the development of all mainaccesses, levels, fix facilities, ventilation driftsand ore flow system for the Grasberg BlockCave Mine and Deep Mill Ore Zone Mine82 International mining | SEPTEMBER 2014by Redpath Australia during the period 2009 to2011.

7 The works package consisted of theconstruction of two drifts, a conveyor drift andtransport drift, followed by the inseamdevelopment and subsequent paneldevelopment for a longwall coal mine. The driftsat KME are exclusive of each other, designedwith different grades and close inseaminterfaces at the German Creek coal seam. As aresult of this, the drift portals are located asignificant distance apart on the surface. KestrelMine is a Rio Tinto/Mitsui joint venture. TheKME drift design provided by Kestrel Coal isgenerally described as follows:nConveyor drift (Arch Profile) gradient 1 in 6,nominally m wide x m high x 1,560 mslope distance from thestart of the box cut tothe inseam phaseinterface, and;nTransport drift (ArchProfile) gradient 1 in 8,nominally m wide m high x 1870 mslope distance from thestart of the box cut tothe inseam number ofimportant factorsneeded to beconsidered during thetender period for thisworks given some ofthe constraints imposedon the works.

8 Theseconstraints included nocross passagesincluded in the design;construction throughmultiple coal seams;and compliance withthe Coal mining Safetyand Health Act was establishedthat to deliver therequirements of the scope of work and contract,a method that would deliver completed drift asthe face advanced was what was required. Thebasic construction principle carried forward wasto provide a completed drift cross section within30 m of the advancing drift EXCAVATION would ensure no delays to subsequentwork activities once the drifts were final drift construction methodologyproceeded with the major EXCAVATION equipmentcomprising of a Mitsui S200MA roadheader,combined with an integrated ground supportsystem.

9 It was further concluded that to achievethe desired outcome systems that minimisedelays to the face advance needed to bedeveloped. The systems identified as integral tothe success of the chosen method included:nMachine capable of EXCAVATION andsupporting to eliminate place changing at thefacenA continuous material handling systemnMethod of extending the ventilation withminimal disruption to the worksnPavement installation method that wouldwork concurrent to the face equipment selection and design for theworks required due consideration of industryregulations, codes of practice and projectspecific requirements and general constraintsassociated with the nature and environment ofthe work.

10 A significant influencing factor in theequipment selection and design was therequirements of the CMSHR. The CMSHR alongwith the recognised standards stipulate thecontrols that must be placed on equipmentoperating in an UNDERGROUND coal mine. Thestipulated requirements meant that the majorityof the UNDERGROUND equipment planned to beused to construct the drifts would requiresignificant modifications prior to the comply with the CMSHR for explosion riskzones (State of Queensland, 2011), it wasnecessary to ensure that any piece of equipmentthat operated in-bye of the last installedventilation duct complied with the requirementsof an Explosion Risk Zone 1 (ERZ1).