1 THE UNIVERSITY OF NEW SOUTH WALES Outline of Presentation SCHOOL OF MINING ENGINEERING z Mining Methods z z z z David Laurence Classification of Mining Methods Surface mining Underground mining Environmental impacts and risks Safety impacts and risks © UNSW School of Mining Engineering 2 Mining methods - Classification z z z z Surface Mining Surface and underground Coal and non-coal Non-coal Metals Non-metals Non-metals Construction materials Industrial minerals Gemstones Open cut metal mining 3 © UNSW School of Mining Engineering © UNSW School of Mining Engineering Characteristics of large-scale open pits Technology developments z Typically low unit value ores, either: low grade / high value commodity z base metals: eg Bingham Canyon (USA), Century Zinc (Aus) gold & diamonds: eg SuperPit (Aus), Finch (RSA) z Î Î Î Î Late 1800s large-scale surface mining began with development of steam operated mining units Steam shovel technology first used in civil construction for construction of Panama & Suez canals Î low value commodity z iron ore: eg Pilbara region rare earths: eg Borax (USA) z Î Î 5 later transferred in 1904 to Bingham Canyon for loading rock into rail wagons Technology in minerals processing allowed economic recovery of low-grade ores Progressive improvements in technology led to Î © UNSW School of Mining Engineering 4 Î larger & heavier rotary drill rigs bulk explosives electrical and hydraulic loading units larger capacity trucks © UNSW School of Mining Engineering UNSW KCMI 6 David Laurence Best Practice - Mining Methods 2 Comparison with U/G methods Characteristics - business drivers 9 More favourable aspects (especially if large, regular shaped, shallow deposits) z 9 9 9 9 9 working environment and less hazards - safety lower unit operating costs flexibility of operations grade control can selectively mine (eg using excavators) z 8 Less favourable 8 8 8 8 increasing recovery tied to increasing ore dilution greater environmental impact - all overlying material needs to be extracted lesser ability to selectively leave rock in situ more exposed to natural elements & climatic changes 7 © UNSW School of Mining Engineering To be profitable requires economies of scale from low unit cost high volume Key Business Drivers high productivity methods and processes high capital utilisation high volumes efficiencies to position in 1st quartile of cost curve © UNSW School of Mining Engineering 8 Characteristics - mining operations z Emphasis on quality control measures to ensure Î Î z high recovery, & low dilution Continuous, round the clock operations Usually on-site processing to z Î Î Î z reduce transport costs improve grade increase inherent value Leverage from materials handling Î Trend to use larger capacity equipment & more automation 9 © UNSW School of Mining Engineering Pit terminology – active pit zones z z z z z z © UNSW School of Mining Engineering 10 Pit design Bench - a working surface (normally horizontal) on which mining activites take place Bench face - a vertical exposure of the rock face Bench height - vertical distance between adjoining benches Bench crest - top edge of a bench face Bench toe - bottom edge of bench face Bench slope - the angle joining the toe to crest © UNSW School of Mining Engineering 11 © UNSW School of Mining Engineering UNSW KCMI 12 David Laurence Best Practice - Mining Methods 3 Some large-scale operations z z z Cadia Gold/Copper. Mine reserves >200 Mt, grades 0.73g/t Au, 0.17% Cu, 10 year mine life @ mining rate 60 Mtpa (1999) Pilbara mines Iron Ore. Mining reserves >500Mt, grade 64% Fe, 50+ year mine life @ mining rate 30-80 Mtpa Porphyry copper mines Alumbrera Namosi © UNSW School of Mining Engineering 13 Cadia Hill Gold Mine Mining Cadia Hill Gold Mine KOMATSU HYDRAULIC SHOVEL LOADING CAT793 TRUCK 15m bench height Current rate ~200kt per day Mining Fleet: 14 x Cat 793C trucks 2 x Demag H655 shovels 1 x Cat 994 loader 2 x Cat D11R dozers 1 x Cat 854 / 1 x Cat 844 wheel dozers 1 x Cat 16H / 1 x Cat 24H graders 1 x Cat 769D water truck 1 x Cat 773D fuel/service truck 3 x Ingersoll-Rand DML 45 blasthole rigs Cadia Hill Gold Mine 40’ SAG MILL Cadia Hill Gold Mine UNSW KCMI Cadia Hill Gold Mine David Laurence Best Practice - Mining Methods 4 Surface Mining Quarrying © UNSW School of Mining Engineering 19 © UNSW School of Mining Engineering 20 Importance of Industrial Minerals z z z z z z © UNSW School of Mining Engineering 21 essential to society building blocks of economies - industrialised and developing mostly for domestic consumption can be major export earner NSW - > A$200 million; WA > $1billion USA - 2.6 billion tonnes of aggregate - 1997 © UNSW School of Mining Engineering 22 Characteristics of the Industry z z z z z z © UNSW School of Mining Engineering 23 from large corporations (eg Normandy, WMC) to small partnerships large companies are becoming more global in outlook eg Normandy in Pasir Gudang (glass-grade K feldspar from WA); WMC in Finland principal industries - paint, plastics, rubber, paper, ceramics, refractories, glass and foundries unglamorous side of the mining industry high bulk low value (except gems) highly substitutable (eg fillers) © UNSW School of Mining Engineering UNSW KCMI 24 David Laurence Best Practice - Mining Methods 5 Characteristics of the Industry (continued) z z z OHS Issues and Constraints z limited value adding in Australia industry is fragmented compared with coal, gold and base metals legislation sometimes unclear and variable state by state z z dust disease injuries mobile and stationary equipment rock mass blasting Î © UNSW School of Mining Engineering © UNSW School of Mining Engineering 25 flyrock 26 © UNSW School of Mining Engineering 27 28 © UNSW School of Mining Engineering Environmental issues and constraints z z z z z © UNSW School of Mining Engineering 29 vegetation biological diversity sedimentation and water quality noise, vibration landscape © UNSW School of Mining Engineering UNSW KCMI z z z social/community impact traffic closure highly visible many opportunities for multiple land use 30 David Laurence Best Practice - Mining Methods 6 Underground metal mining z Terminology z Mining methods – drivers, core risks, unit operations z 31 © UNSW School of Mining Engineering Open stoping – sublevel, long-hole, benching Caving Other The Future? © UNSW School of Mining Engineering 32 Common Terms z z z z z z z z z z z z z z shaft skip winder adit decline ramp crosscut drive drawpoint raise z z z z z z z z z z z z z z z z z z mullock cuddy stope slot square set stull orepass chute longwall flatback cablebolt rockbolt splitset sump pump rising main gympie spaller crib …….. winze footwall - hangingwall sublevel sill 33 © UNSW School of Mining Engineering © UNSW School of Mining Engineering 34 Scope and Scale z z z z z z narrow quartz reefs to massive disseminated porphyry copper ore bodies <1 tonne/person/day to 1000s tonne/person/day 1 person to > 5000 person operation pick and shovel to teleremote loaders tens of thousands to $500 million capital cost near surface to 4000 metres depth © UNSW School of Mining Engineering 35 © UNSW School of Mining Engineering UNSW KCMI 36 David Laurence Best Practice - Mining Methods 7 Stoping Methods z z z z z z z z z Choice of method dependent on: z massive disseminated narrow vein ORE BODY CONFIGURATION z z z z z z SAFETY/REGULATORY FACTORS z ENVIRONMENTAL FACTORS z ECONOMIC CONSIDERATIONS • Lithology Groundwater Rock strength & stresses LABOUR & POLITICAL CONSIDERATIONS z FLEXIBILITY • Trend Back to Underground Mining z z z z Handle the unexpected – internal and external changes © UNSW School of Mining Engineering 40 What are we trying to achieve? 1980s - gold boom - small/medium open cuts resource continues at depth cost issues - block caving competitive with open pit technology - eg large trucks environmental issues © UNSW School of Mining Engineering Aim to choose a method generating a consistent profitable cash-flow for the longest period of time. z 39 © UNSW School of Mining Engineering 38 © UNSW School of Mining Engineering Dip, plunge, strike, depth GEOTECHNICAL EVALUATION z Small scale Others Choice of method dependent on: MINERAL OCCURRENCE z Cut and Fill stoping Room and Pillar Shrink stoping Vertical Crater Retreat 37 © UNSW School of Mining Engineering z Sublevel or long-hole open stoping Bench or retreat stoping Caving methods z z z z 41 Safety Efficiency (maximum resource utilisation) Economy (lowest cost, maximum profit) Environmentally friendly © UNSW School of Mining Engineering UNSW KCMI 42 David Laurence Best Practice - Mining Methods 8 The Production Cycle SUBLEVEL STOPING 43 © UNSW School of Mining Engineering Sublevel Stoping Sublevel Stoping - Operations • • • • • • or blast-hole or long-hole stoping or benching high production, bulk mining method large, steeply dipping, regular ore bodies having competent ore and rock that requires little or no support development-intensive minimum stope widths > 5m • • • • • • 3 z drilling – fan or vertical; downholes/upholes – up to 60m blasting – single or multiple rings ground support – cables up to 45m loading – boggers – “manned” or remote controlled hauling – orepasses or direct onto trucks backfilling – deslimed tailings – with, w/o cement; mullock; safety – very safe; working under protected ground or on top of broken ground; retreat method; remote equipment; good ventilation; economics – favourable until a production problem then very serious 45 © UNSW School of Mining Engineering © UNSW School of Mining Engineering Sublevel Stoping - Advantages Sublevel Stoping - Disadvantages • • • • • • • z amenable to mechanisation and high stoping efficiencies (100 tonnes/shift) high production rate safe high ore recovery > 90% easily scheduled, stopes drilled well in advance blasting infrequent ore drawn off immediately (compared with shrink stoping) © UNSW School of Mining Engineering • 46 capital intensive non-selective • 47 44 © UNSW School of Mining Engineering can be high dilution if irregular walls © UNSW School of Mining Engineering UNSW KCMI 48 David Laurence Best Practice - Mining Methods 9 Retreat Benching (Bench stoping) Retreat Benching (Bench stoping) • • • • • z narrow stoping widths unfilled or filled with development waste longitudinal stopes, need for vertical (rib) and horizontal (sill or crown) pillars pillars in low grade or dictated by geotechnical assessment development in ore 5 © UNSW School of Mining Engineering 49 Retreat Benching (Bench stoping) CAVING SYSTEMS z z z © UNSW School of Mining Engineering 51 Sublevel Caving Based on fracturing the mineralised rock and the surrounding waste rock under more or less controlled conditions. Fractured material fills the voids left by ore extraction, creating a caved area on the surface over the ore body. Complete and continuous caving is essential since large empty spaces underground can collapse suddenly with severe after effects on the mining operation. 52 © UNSW School of Mining Engineering Sublevel Caving • • • • • © UNSW School of Mining Engineering 50 © UNSW School of Mining Engineering 53 Uses gravity flow for blasted ore and caved waste. Orebody divided into closely spaced (8-15m) sublevels Fan-shaped upholes drilled ahead of blasting Blasting of one fan breaks the ore causing a cave. Ore is loaded and waste rock in hanging wall breaks and fills the void. Increasing dilution until loading stopped and next fan blasted. © UNSW School of Mining Engineering UNSW KCMI 54 David Laurence Best Practice - Mining Methods 10 Sublevel Caving Sublevel Caving • z • • • z Used in steeply dipping ore bodies and others having large vertical dimensions Preferred where ore and waste can be easily separated Much development in ore Highly mechanised with LHDs Most examples international rather than Australia • • • • 55 © UNSW School of Mining Engineering Sublevel Caving z • • • • • 56 Relatively high dilution All ore must be drilled and blasted Ore losses in passive zones of gravity flow Relatively large amount of development – horizontal and vertical Possible subsidence and surface damage Relatively large amount of research data required 57 Block Caving z © UNSW School of Mining Engineering Block Caving © UNSW School of Mining Engineering z One of the safest methods – mining activities in relatively small drives Highly mechanised – repetitive Flexibility Working conditions and organisation Disadvantages • z Advantages 58 Block Caving Suitable for large, massive ore bodies with a proper fracture pattern. Once ore is undercut, the settlement by gravity causes crushing and fracturing of the ore. As the broken ore is drawn off, additional settlement and crushing takes place. © UNSW School of Mining Engineering © UNSW School of Mining Engineering z Typical ore body a porphyry copper z Rock strength can be fairly weak or strong Must have sufficient fractures in different orientations to allow the rock mass to break up under gravity into pieces small enough to pass through the drawpoints. z 59 well-disseminated mineralisation of large lateral and vertical extent. © UNSW School of Mining Engineering UNSW KCMI 60 David Laurence Best Practice - Mining Methods 11 Porphyry Coppers Block Caving z Production • Up to 80,000 tpd • Drawpoint design & spacing critical • Good ventilation to remove dust • Undercut and slot drilling and blasting to initiate cave • Dilution often 10 to 25% but variable dependent on ore grades, commodity price etc • Secondary blasting a major cost • Hangups a major problem 61 © UNSW School of Mining Engineering Block Caving z • • • z Inexpensive since drilling, blasting, ground support and labour costs reduced Ventilation simplified Production levels can approach open pits Grade control through drawpoints aids mine planning © UNSW School of Mining Engineering © UNSW School of Mining Engineering 62 Block Caving Advantages • © UNSW School of Mining Engineering Disadvantages • • • • 63 65 Major surface subsidence Development time and money can be excessive Levels and drawpoint maintenance is expensive Draw control requires continual focus © UNSW School of Mining Engineering © UNSW School of Mining Engineering UNSW KCMI 64 66 David Laurence Best Practice - Mining Methods 12 © UNSW School of Mining Engineering © UNSW School of Mining Engineering 67 © UNSW School of Mining Engineering 69 © UNSW School of Mining Engineering 68 70 Other Stoping Methods z z z z Cut and Fill Room and Pillar McArthur River – NT Vertical Crater Retreat INCO (& Broken Hill) Narrow vein mining Shrink & gallery stoping Î © UNSW School of Mining Engineering 71 Hillgrove © UNSW School of Mining Engineering UNSW KCMI 72 David Laurence Best Practice - Mining Methods 13 Cut and fill stoping Cut and Fill z z z z Ore excavated in horizontal slices, starting from the bottom of a stope and advancing upwards. Blasted ore is loaded and completely removed from the stope. When the full slice has been excavated the corresponding volume is filled with waste material The fill supports the stope walls and is a working platform to mine the following ore slice. 2 © UNSW School of Mining Engineering 73 © UNSW School of Mining Engineering 74 Room and Pillar • • • • • • • • Oldest underground method Ore left as pillars Typically flat ore bodies generally <30 deg Competent rock masses – stopes stay open during life of mine Depth limitation due to load capacity of pillars Low chance of surface subsidence Can be large scale, versatile and flexible 2 Recoveries < 100% © UNSW School of Mining Engineering 75 © UNSW School of Mining Engineering Vertical Crater Retreat (VCR) Vertical Crater Retreat (VCR) z z z z © UNSW School of Mining Engineering 76 77 A horizontal, flat-back variation of sublevel stoping using spherical crater charges to break the ore. the only patented method. blasting carried out at the base of vertical holes, making horizontal cuts and advancing upward. Shrinkage provides wall support. © UNSW School of Mining Engineering UNSW KCMI 78 David Laurence Best Practice - Mining Methods 14 Shrink stoping Shrink stoping • z z z z • Vertical overhand mining method – most of the broken ore remains in the stope to form the working floor Broken ore also provides additional wall support Mining upwards in horizontal slices Sufficient ore drawn off for swell factor Narrow veins Difficult to mechanize – drawpoints generally replaced chutes 79 © UNSW School of Mining Engineering © UNSW School of Mining Engineering 80 The Future z z z lower cost safer technological advances automation trucks Î loaders, trucks Î Deeper Î larger payloads (>50t) types Î surface • larger drive dimensions • road trains 81 © UNSW School of Mining Engineering ground support © UNSW School of Mining Engineering 82 The Future z Novel methods eg McArthur River Uranium (Canada) Raise Bore Mining Method ore © UNSW School of Mining Engineering Step 4 : Back Filling lower strength concrete injected from the upper mining chamber. 83 © UNSW School of Mining Engineering UNSW KCMI 84 David Laurence Best Practice - Mining Methods 15 THE UNIVERSITY OF WALES ROW 25 Top View of Zone 2 Ore NEW SOUTH Zone ROW 24 ROW 23 ROW 22 ROW 21 ROW 20 ROW 19 SCHOOL OF MINING ENGINEERING In Summary…. ROW 18 ROW 16 ROW 15 ROW 14 ROW 13 ROW 12 1. ROW 11 ROW 10 ROW 9 ROW 7 High Grade Ore ROW 6 ROW 5 2. ROW 4 ROW 3 ROW 2 ROW 1 Mined out as of June 2002 Poten tial Sa nd 3. Choice of stoping method is dependent on a number of factors Sublevel stoping and benching have produced the most tonnes but caving methods are likely to increase in significance Technological advances are happening based on cost, safety and environmental drivers © UNSW School of Mining Engineering UNSW KCMI 86 David Laurence Best Practice - Mining Methods
