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On the 18th November, 19'58, the first coal was delivered to the Morwell Power Station from the adjacent Open Cut using conveyors for the transport of the coal from the working face to the boiler bunkers. As the cut develops the coal seam will be worked for its full depth of about 360 feet from four benches, each feeding a conveyor line along th.e face and up out of the cut to the power station and briquette factory. By 1970 the estimated maximum daily demand reaches 60,000 tons and the total annual output 18 million tons. The complete conveyor installation will then total some 9 miles with a capital cost of over £3~ million.The choice of conveyors in place of the more usual rail system was made possible by the development of movable belt conveyors which use mechanical conveyor shifting, high belt speeds and flexible high strength belts and the paper deals with these and some other aspects of the scheme.INTRODUCTIONThe development of brown coal deposits is usually based on open cut workings equipped with a few large dredgers giving an almost continuous output of coal or overburden which has to be hauled a comparatively short distance. These are ideal conditions for conveyor operation, and it is surprising that, until recently, rail transport has been used almost exclusively in brown coal open cuts. In some cases inclined conveyors have been introduced to take the coal from the coal levels up out of the cut to bunkers at groundlevel, but trains have been left to operate between the ditch bunker feeding the conveyor system and the dredger.

Jan 1, 1960

The proximity of the Town of Kalgoorlie to the Mount Charlotte mine necessitates that charge weight per delay be limited in order to keep surface vibration levels within acceptable limits and to reduce damage to underground workings. The mining system requires that large mass blasts must be used to recover pillars and therefore a large number of separate delays are needed. Until recently all blasting has been done electrically, fired from mains, but with the introduction of large diameter blastholes (165mm diameter) this firing system was inadequate. Various firing systems were considered, but after extensive trials a non-electric sequential firing system was chosen. This system fulfilled all criteria of blast design, was relatively straight forward in charging technique and had a very simple primary initiation system. Although initially designed for large mass blasts, the non-electric firing system is now used for all large hole blasting and in a simpler form for small (57mn diameter) holes.

Jan 1, 1982

By P D. Franzmann, D J. Readett, J Peterse

A better connection between laboratory- and pilot-scale test results, and heap bioleaching performance can be achieved by generating reliable information on the fundamental microbial, chemical and physical processes that occur in heaps and incorporating this information into a comprehensive and robust model. More efficient heap bioleaching, particularly of chalcopyrite, has the potential to add value to the mining industry as well as deliver attractive environmental and social benefits to the communities within which those companies operate.The results of fundamental chemical and microbiological studies of the leaching mechanism, the temperature dependence of chalcopyrite bioleaching, and the optimisation of leaching conditions are described with examples from full-scale heaps. The development and application of a number of novel techniques and tools has assisted our understanding of heap subprocesses mineralogy, hydrology, chemistry and microbiology. The heap bioleaching model HeapSim, which embodies a large number of effects not previously accounted for in other models, continues to be refined and has been applied successfully to the study of several heap bioleach systems.

Jan 1, 2004

Truly launched during the 1939-45 war, b¬,osted since by huge increases in demand for food, shelter and manufactures of ill kinds, petrochemicals have rocketed into prominence' all'oVer''th'e world and are accelerating to even greater heights.Manipulation of the hydrocarbons in petroleum or natural gas provides raw materials for a wid.e'variety of plastics, resins, detergents, rubbers, chemical intermediates, fibres and fertilisers. These in. turn.. go into a host of products essential to our way of life.A5 a source of chemicals, petroleum has achieved a high place. because of its abundance, relative.eheapness acid ease "f transport and because it can,be' economically processed.'If a nation's industrial' progress is measured by ' the ' modern yardstick of petrochemical production,'Australia has reasonto be proud, for it now has 1S petrochemical plants worth'156 million, either in operation or under construction.At several locations near Sydney and Melbourne, these plants produce petroleum ethylene, propylene, butadiene and benzene, or convert these building blocks into the three major thermoplastics (polyethylene; polyvinylchloride and polystyrene)-a.nd"S.B.R.synthetic" rubber. "A number bf other imr-ortant petrochemicals, including carbon black, and ammonia, also are made, or-planned...Most petrochemicals find application. in seven principal industries - rubber, fibres, detergents, surface coatings, automotive, agriculture and plastics. They play a .part in many other industries, including mining and metallurgy.In Australia, population growth,.an -incr.easing standard of living, greater industrial activity and the replacement of older materials all should considerably expand the markets for established petrochemical plants and lead to the introduction of new manufactures.Unless thwarted, these positive forces should propel petro-chemicals into a future glittering with promise;' ò 'However, some help for the infant industry seems needed if petrochemicals, while growing with the nation, are to contribute as they can to our national development.

Jan 1, 1962

By M J. Saynor, W D. Erskine an, D R. Moliere

The Jabiluka uranium mine was constructed in the Ngarradj catchment, a right bank tributary of Magela Creek in the Northern Territory. The Jabiluka Mineral Lease is adjacent to Kakadu National Park, near an area listed as Wetlands of International Importance under the Ramsar Convention and recognised under the World Heritage Convention. In the late dry season of 1998 and prior to the 1998 - 1999 wet season, a stream-monitoring program was implemented in the Ngarradj catchment to collect baseline data on sediment transport within the catchment to assess and proactively manage associated impacts caused by mining at Jabiluka. Stream suspended mud concentration, stream discharge and rainfall data were collected for four wet seasons (1998 - 2002) giving an almost continuous data set. The stream system has high natural variability dependent on rainfall intensity and subsequent discharge and pre-wet season fire distribution and intensity. In general, mud concentration is elevated at the commencement of the wet season until about February. This is caused by first-flush removal of surface material detached during the dry season by agents such as bioturbation (including anthropogenic activity), wind erosion and surface desiccation. Water quality trigger values downstream of the mine were derived using upstream percentiles and the before-after-control-impact, paired site design. Both analyses showed no observable impact from mine construction in 1998 or during the study period. However, the impacts of dry season fires could be clearly detected. The data set provides good baseline information for future assessment at Jabiluka and demonstrates the need to view measured parameter values on a catchment-wide basis with knowledge of rainfall, discharge and fire distribution.

Jan 1, 2004

By H Beucher

The uranium grade in roll front deposits is the result of successive processes that can be summarised in two steps. First a sedimentary phase, which gives the deposit support, then an oxidation-reduction phenomenon, which leads to the uranium deposit itself. In order to simulate such a deposit, it is important to mimic these different phases. The final aim of such a study is to localise the uranium itself and to reproduce the internal heterogeneity of the orebody in order to simulate the recovery process. The idea in this paper is not to reproduce a genetic approach but to consider the final image of the deposit. Three approaches are proposed. The first one consists of simulating the facies of the sedimentary deposit. The second approach reproduces the distribution of facies resulting from oxidation phenomenon (reduced or oxidised facies). The third approach consists of simulating the mineralisation at the interface of reduced and oxidised areas using the definition of a new data set determined by the grade values. At the end of each approach, the uranium grade could be simulated facies by facies according to the corresponding distribution characteristics. The plurigaussian method dedicated to random set simulations is well-suited for the facies simulations of deposits resulting from several sedimentary processes whether correlated or not. In this paper, the benefit of this method is demonstrated in an actual case study.

Jan 1, 2006

By P Jago

KCGMÆs Fimiston Open Pit, located in the centre of the historic Golden Mile, is situated above some 3000 kilometres of old underground workings. These workings, both level and vertical, present significant safety and operational problems in the pit. One of these challenges is in safely drilling void areas so that they can be charged and blasted effectively. Current drilling practices in these areas require machines that can only drill 115 mm holes on a smaller pattern than the standard blast pattern. This results in more time and cost to both drill and charge these areas. Any other method currently available to drill out these areas involves putting operators in a potentially hazardous situation by being too close to the void area being drilled. Not effectively drilling and blasting these areas leads to hazardous situations further in the mining cycle including oversize, large toe and uncollapsed voids. Ineffective blasting also causes reductions in mining productivity and mine to mill performance. In response to these issues, KCGM has commissioned the implementation of a fully remote controlled DM45 blast hole drill rig to drill out selected void areas. The remote system, installed in conjunction with Ausdrill Ltd and GM Mining Electrics, is designed to operate similarly to a tele-remote bogging system with the operator controlling the drill rig from a separate control cabin via radio signals and video feed. This allows KCGM to drill in areas of higher risk without exposing the operators to voids. The drill rig will also be able to drill standard patterns through some specially selected void areas, reducing costs and extra time associated with drilling and charging void affected areas. The remote rig is expected to provide a number of benefits, both in the drilling process and in further downstream operations. Costs of drilling in void areas are expected to decrease with standard patterns instead of smaller patterns being drilled. Safety and operator comfort are also expected to increase through removing the operator from the pit floor. Blasting is also expected to see significant improvements through increased ease of charging void areas (because of larger holes and standard patterns), more consistent patterns resulting in less secondary blasting and toe and an overall improvement in the speed and cost of charge-up practices. This more consistent blasting will also improve shovel productivity, crusher performance and overall mine-to-mill efficiency. This paper presents an overview of the development of the remote controlled system, including modifications that have occurred since commissioning. It explains some of the problems encountered and how these have been solved. Key issues for operational success will be identified and explained with a view to making future implementations easier. Factors used to assess the performance of the remote controlled rig will also be explained in further detail and used in a preliminary assessment of the rigÆs feasibility.

Jan 1, 2003

By S Hughes

The smelting of concentrates and secondary materials has been subject to increasing challenges in recent years due to declining grades of feed materials, increasing impurity levels and ever more stringent environmental regulations. In addition there has been a growing focus on maximising the efficiency of energy usage and recovery of values. New opportunities have been created with rising metals prices and improved systems for the collection of secondary materials, giving rise to a need for more flexible process solutions.This paper focuses on a number of specific cases where a process solution has been developed using the Outotec« Ausmelt Process to meet particular feed material challenges and overcome limitations inherent when employing traditional pyrometallurgical processes.The first case involves the development and commercial implementation of a smelting process to recover values from zinc smelting residues typically deposited into dams as a waste product. The second case describes the application of the Ausmelt process for the smelting and converting of secondary copper feed materials, including e-waste. These materials contain a wide range of metals and plastics and need to be processed appropriately to maximise the recovery of values whilst avoiding environmental problems. The third case study covers the smelting of nickel concentrates containing elevated magnesia levels as well as nickel bearing catalysts with high alumina content, neither of which can be readily processed when employing traditional pyrometallurgical technologies. CITATION:Hughes, S, 2013. Pyrometallurgical process solutions for complex raw materials, in Proceedings MetPlant 2013 , pp 519-530 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 15, 2013

By L Whitbourn, K Yang, P C, E Ramanaidou

The potential of hyperspectral mineral mapping within a mine environment is demonstrated. Central to this capability has been the development of portable or vehicle-mounted, hyperspectral mine face-mapping systems. Data from these systems were used to detect subtle mineralogical variations and map their distribution across rock faces in a fashion that previously was not possible. In one study, the data usability was enhanced by ædrapingÆ the mineralogical determinations over a three-dimensional æmodelÆ of the rock-face. The eventual melding of the spectral mine face-mapping and three-dimensional spatial technologies will result in a new generation of mineralogical and structural information becoming available to mine geologists, engineers and metallurgists. Specific uses for spectrally-derived, mineral mapping data sets could include:ore grade mapping systems based on either direct detection of ore minerals themselves (eg iron and nickel oxides), or mineralogies that may be used as surrogates for ore-grade information (via various alteration minerals) after a suitable orientation survey; detecting mineralogies that have a deleterious effect on milling, metallurgical processing or have occupational health implications (talc, swelling clays, carbonates, asbestos, etc); selective mining and blending by collecting, processing and displaying such mineralogical images in near real-time to monitor ore grade and quality, and allow the separation of ore from waste during loading operations at the mine face; a mineral detection and mapping capability to assist in structural and geotechnical mine planning applications; and an enhanced geological detection and mapping capability for ore mineral species or alteration mineralogies that may be used to vector further mineralisation, update the existing mine ore model, or provide input to assist in the control of autonomous mining equipment. Within the Woodlawn open pit, Fe- and Mg-chlorites and phengitic- micas associated with sulfide mineralisation were detected and mapped. Subsequent studies using a second generation face-mapping system demonstrated the direct detection of ore-grade materials for iron-ore and nickel laterite mining activities. Satisfactory and meaningful results were extracted from data that were collected under a variety of challenging conditions. However, these non-ideal climatic and operational conditions would be expected under most operational situations in a mine environment. Development of a system using artificial illumination, permitting night-time (and eventually underground) operation and elimination of atmospheric absorption effects is underway.

Jan 1, 2006

By Vynne J. F

Drill monitors for rotary blasthole drills have been available to the mining industry since the 1970s. The early monitors were pen strip chart recorders that were developed for the oil drilling industry and adapted to mining. They recorded drilling parameters such as depth, pull-down pressure, torque, RPM, and hailing air pressure. While these recorders could generate a large volume of paper, the amount of useful data was minimal. The data was not summarised and required an engineer to interpret the chart traces. Being a mechanical recorder, the devices were also susceptible to frequent failures. Modem electronics, and the development of the personal computer and its associated software have radically changed the type of instrumentation that is now available for blasthole drills. Perhaps more important is what can be done with the data. The PC allows the logged data to be analysed, summarised, and a variety of reports to be generated. The reports can be customised to meet the specific requirements of the mine and reduce the amount of time that is required to interpret the data. There is also an increased awareness in the mining industry of the importance of production drills. Blasthole drills have typically been the piece of production equipment that received the least amount of attention in a surface mine. Management focussed on the trucks and shovels or draglines. This situation is changing, and therefore the benefits that can be derived from monitoring drill performance are being recognised. Potential economic benefits of installing drill monitors have been documented in previous papers (Peck and Vynne, 1992). Mines are finding that pay-back periods of less than twelve months and rates of return in excess of 30 per cent are not uncommon. These benefits include the following: 1. Reduced overdrilling; 2. Increased rate of penetration; 3. Helping to locate coal seams; 4. Identification of weak and strong zones; 5. Reduce geophysical logging; 6. Optimising blasts; 7. Improved fragmentation and diggability; 8. Decreased coal dilution; 9. Increased bit life; 10. Reduced maintenance costs; 1 I . Improved accuracy of data and reports.

Jan 1, 1995

By Kneisley RO

This paper presents a brief overview of current bump mechanics theories and pillar design methodologies, and relates these concepts to experiences at two mines located in a north- central Utah coalfield where different pillar designs were used to control mountain bumps. Experiences gained at the first mine demonstrated the successful implementation of a two-entry, 9.8 m (32 ft)-wide, yield-pillar design. A U.S. Bureau of Mines field study quantified the timing of chain pillar yielding and resulting load transfer from the gateroad. In-mine pillar response, although apparently sensitive to site-specific conditions, compared favorably to estimates derived using two yield- pillar design methods. A second study conducted at another mine located in the same district, but subjected to different geologic conditions, documents the unsuccessful attempts to employ progressively narrower three-entry pillar designs based on successes achieved at the first mine site. This second mine never achieved a true yield-pillar design. Use of pillar widths ranging between 9.1 m (30 ft) and 27.4 m (90 ft) always resulted in violent bumps in the tailgate pillars. The pillars were either too large to yield, or too small to support peak operational loads. Hypothetical gateroad systems were evaluated using both analytical and empirical approaches for configurations comprised of two rows of conventional pillars, and systems incorporating both yield and abutment pillars. Analysis concluded that yield pillars less than 6.1 m (20 ft) wide and abutment pillars ranging between 30.5 m (100 ft) and 39.6 m (130 ft) square would be required to achieve a stable gateroad design. However, results of a field study conducted on a two-entry, 36.6 m (120 ft)- wide abutment pillar concluded that abutment pressures from the first panel overrode the pillar, and that a still larger pillar may be required to preclude bumps in the tailgate during second panel mining. Without the benefit of a demonstrated in-mine success, it is not clear which design would ensure elimination of gateroad bumps.

Jan 1, 1992

Over the past seven years, a combination of New Zealand-, Australian- and German-led research voyages using the research vessels Tangaroa, Southern Surveyor, and Sonne respectively, have revolutionised our understanding of the Kermadec-Tonga arc-backarc systems. This convergent margin is the most seismically-active subduction zone system on Earth with convergence rates steadily increasing northwards from the Hikurangi Trench to ~250 mm/year at northern Tonga. In combination with the intra-oceanic setting, factors potentially producing magmatic, tectonic, and hydrothermal variability in this system include an increase in potentially subductable sediment northwards along-strike, intersection of the Louisville Ridge (hot-spot chain) and Osbourn Trough (paleo-spreading centre) with the arc at ~25¦S, and the possibility of Samoan (hot-spot) plume ingression in the northern Lau Basin. The bulk of the magmatism is submarine; whereas only a few emergent (some transient) volcanic islands exist, about 80 submarine volcanic centres of significant size (>1000 m above surrounding sea floor) are present between White Island in the south to north of Tafahi in Tonga. About 35 per cent of these centres are hydrothermally active. Important petrogenetic features of the volcanic rocks along this arc system are the abundance of rhyolite (some quartz-amphibole-bearing), and the outcrop of primitive olivine-clinopyroxene-phyric basalts in satellite cones of the major edifices. Many of the edifices consist of complex caldera systems. Eruptions from and degradation of these edifices were probably tsunamigenic. Many of the hydrothermal systems developed within the edifices are likely destroyed during the sector collapses which are the characteristic edifice degradation mode. There are three backarc spreading systems along this margin: the Havre Trough, Valu Fa-Eastern Lau Spreading Centre, and the nascent Fonualei Rifts. The latter are particularly notable in having captured the entire suprasubduction zone magmatic flux for a distance of about 150 km, shutting down the adjacent volcanic front arc volcanoes.

Jan 1, 2005

By J Leppinen, B Johanson, R Kalapudas, G McMahon

The Suurikuusikko gold deposit was discovered in 1987 in western Finnish Lapland, 54 km NNE from the town centre of KittilS in the volcanic belt of Central Lapland. It is hosted by tholeiitic basalts in a graphite-bearing albitite breccia. The ore is located in subvertical shear zones characterised by strong albitisation, carbonatisation and sulfidisation. The ore minerals consist of arsenopyrite, pyrite, chalcopyrite, sphalerite, tetrahedrite, bournonite and rutile. Small amounts of pyrrhotite, gersdorffite, jamesonite, bornite, gudmundite, tetrahedrite, stibnite, kermesite, berthierite and native Sb are also present. Gold occurs as invisible and as 1 - 2 ¦m size inclusions in arsenopyrite and pyrite, on their grain boundaries and in fractures. The average amount of gold leached by cyanide is 2.93 per cent. The æinvisibleÆ gold contents were studied in pyrite and arsenopyrite by electron microprobe analysis (EPMA) and secondary ion mass spectrometry (SIMS) at CANMET/ MTL. Gold element distribution images show zoned patterns both in pyrite and arsenopyrite. SIMS analyses range from 343 to 55 ppm Au in arsenopyrite and from 217 ppm down to 0.32 ppm (detection limit 478 ppb) Au in pyrite. EPMA results range from 939 to below the detection limit 24 ppm Au in arsenopyrite and from 267 ppm to below 22 ppm Au in pyrite. Recovery of the refractory gold ore was studied using grinding, flotation, bio-oxidation and cyanidation tests. A sulfide bulk concentrate containing 40 ppm Au was obtained by flotation at 90 per cent recovery (As content 5.5 per cent, S content 22 per cent, and mass recovery 15 per cent). The grinding fineness in flotation was P80 -100 to 120 ¦m. At the original fineness the cyanidation recovery from the concentrate was lower than ten per cent, after ultra-fine grinding P80 -10 to 2 ¦m the Au recovery was less than 17 per cent. After bio- oxidation, Au recovery of 95 per cent was obtained in carbon-in-leach (CIL). The bio-oxidation time was two weeks in laboratory test, but after regrinding the oxidation rate was faster and recovery of Au higher. However, the selected method for the mining to be started in summer 2008 is open pit mining and mineral processing methods sulfide flotation and pressure oxidation in an autoclave. The ore reserves were estimated 31 December 2007 as: Probable 18.2 Mt with 5.1 g/t Au, Indicated 5.4 Mt with 3.0 g/t Au and Inferred 10.8 Mt with 3.4 g/t Au. The production capacity will be 3000 t/day.

Jan 1, 2008

By J Austin, R Bitencourt

Differences between the long-term model (LTM) and mine geology system (MGS) grade control block-outs on a blast block scale can impose difficulties to planning crusher feed grade and tonnes on a monthly to weekly blend basis. Detailed geological input to short-term planning has been integral to improve the performance and reduce risk in six-week to three-month production schedules and local variability in tonnage and grades is often not accurately represented in the LTM. The challenge of producing to combined target specifications from different mine sites in an integrated mine to ship business has been reduced with the creation of blast blockout-based short-term model. These short-term blast block models (STBBM or STM) are robust predictive tools created for upcoming benches of current mining areas by firstly collecting data from the pit in the form of bench and face mapping and projecting the structure and stratigraphy down to the next bench. A wire-frame of the projected contacts based on material destination from production blockouts is created and then checked against the LTM. Blast block data from the bench above including assay results and material logging is extracted and validated according to the projected wire-frames (geozones). Individual blast blocks and a full block model are created for each bench production defined by the STP (bench plans). Data output from the STM is in a compatible format for import into scheduling specific software packages. Additional information is incorporated into the STM to allow querying of drill penetration rates, predicted powder factors, material hardness and feed type to further aid in the production planning process and cost forecasting. To date, reconciliation of the STM has been pleasing and certainly an improvement on the LTM, especially in areas where variability is higher due to geological complexity. Short-term predictions derived from in-pit geological observations allow mine planners to more confidently decide on mining block sizes and schedule tonnages and grades, reducing the risk component attached to developing production schedules based directly upon long-term orebody models and mine plans.

Jan 1, 2005

By J E. Lynch

The Mt Leyshon gold deposit produced in excess of three million ounces of gold and considerable silver over a period of approximately 130 years. Most of this production occurred between 1987 and 2001. Mining commenced in 1872, however it was highly likely that Chinese miners were not only removing alluvial gold from the area but were also mining very rich æreefÆ gold. Records for early alluvial and hard rock mining do not exist, however gold production was probably considerable. In the early 1980s Marathon Petroleum (Australia) Ltd (MPAL) joint ventured into the Mt Leyshon area which had been held as a mining lease by Noranda Australia Ltd since 1968. Noranda at that time was concentrating its exploration effort on the Balcooma base metal prospect areas to the north of Charters Towers. In early 1982 MPALs parent company was taken over by US Steel. This led to an opportunity for MPALs Australian management to purchase all tenements and licences (except for coal, oil and gas) which were duly purchased for $US 1 million. At this time MPAL had a remarkable array of gold tenements (many of which were subsequently mined by other companies) and Mt Leyshon was considered to be the highlight. Early æseedÆ capital ($A 3.1 million) was raised with backers being the Bank of America, the NSW Government Superannuation Scheme, Westpac, private individuals and a Queensland grocery chain by the name of æJack the SlasherÆ.

Jan 1, 2004

By J Naude

The TauTona (Sotho for Great Lion) Mine near Carletonville, which is one of AngloGold AshantiÆs most profitable operations in South Africa, has started a multi-million dollar expansion project that is expected to extend the operational life of the mine by at least three years. The project will also secure some 1900 jobs for existing workers and contract workers. The $US140 million project entails the development of the orebody to a record depth of almost 4 km underground. It means that TauTona, which already mines gold at the deepest levels in the world, will deepen its mining activities from 3600 m to a new record depth of 3910 m. There is great anticipation about the expansion program, especially because of new technology that will contribute to a safer working environment. It includes a simplified hoisting system that will minimise safety risks in conveyance activities. Due to the unique nature of this project, depth below surface and working through a three-tier shaft system, various innovative measures were incorporated into the planning of the endeavour. Special support equipment was designed to reduce cycle times and enable the crews to install the extensive support, prescribed by the mineÆs rock engineering department, right up to the face before every blast. Both declines dip at 23¦. The personnel/material (P/M) shaft is 4.4 m wide x 3.9 m high. This shaft is unique in that the conveyance will have an onboard driver. The rock shaft is 4.5 m wide x 3.6 m high. Rock will be hoisted with two, ten-tonne overturning skips. In both cases, P/M and rock, the winders were designed for the highest duty cycle, which is encountered during sinking.

Jan 1, 2005

The safety culture in mining has progressed towards a zero tolerance of injury. This change has required that some historically inherent risks of mining are engineered out or reduced. One of the significant causes of fatality in Western Australia and Worldwide mining is through rock fall, subsidence and inrush. Efforts put into understanding the material properties of the ground we mine and the backfill we place are reflected in improved safety statistics. It is no longer acceptable to not manage these risks and mining, to be sustainable, has to be safe.   Mining historically produced waste products with little consideration of recycling or impact on the surrounding land. The rehabilitation of mining waste products such as mill tailings, heap leach and waste rock is one step towards managing the environmental impact of these waste products. A better step is towards recycling and redepositing these products to produce a more environmentally sustainable mine site.   Gold fields St Ives lease is an active network of new and historic undergrounds and open pits within the Lake Lefroy and Kambalda district. The process of creating voids underground followed by open pits mining through the old voids allows the use of backfilling to control inherent hazards and dilution. Backfill provides opportunity for the disposal and recycling of mining waste materials at the same time as meeting requirements of mine support. Materials available on the St Ives site include spent heap leach, reclaimed tailings and waste mullock. Through recycling and re-depositing these materials to St Ives and neighbouring mines, the reliance on imported material to meet their needs and impact on surrounding land is reduced.   At St Ives, paste fill and barricade design have been reworked to allow backfilling into stopes with water inflows up to six litres per second. This has required a rethink of the drainage and monitoring of water management systems previously used for hydraulic fill and apply them to paste.   The St Ives open pits have developed methods to mine through underground workings and individual stope voids up to 62,000m3. Here backfill is used to reduce the consequence of catastrophic, unexpected failure of the crown and minimise ore lost down voids and dilution through increased blast movement. This paper outlines the less common methods being adopted to use the recycled materials and ways it has been managed to suit the needs of the company.

Jun 1, 2010

By Cloutier JY, Quinn P, LeClerc A, Dube G, Agar GE

Gold dissolution by cyanide requires the presence of oxygen which is usually supplied by sparging compressed air into the gold containing slurry. For those ores that contain certain obnoxious substances that consume oxygen, maintaining the required minimum level of dissolved oxygen can be troublesome. One of the most economical solutions to the problem of low dissolved oxygen, especially in plants that have air compressors installed, is to enhance the rate of oxygen mass transfer. The oxygen mass transfer rate was measured in a two phase system using two different sparger arrangements, and with addition of a frother that is known to reduce the bubble size produced by the sparger. The common sparger system was shown to be inefficient compared with a readily available but under utilised method of gas dispersion which introduces air directly below the reactor turbine. Transfer of this technology to an operating plant confirmed the beneficial effect of the improved sparger system. The addition of the frother did decrease the bubble size, but it also reduced the oxygen mass transfer rate.

Jan 1, 1993

By L Richards, R L. Brathwaite, C Mazenga

Underground mining of gold-silver bearing quartz lodes was carried out in the great mines at Martha Hill, Waihi over 70 years from 1882 until 1952. Shafts and stopes reached a total depth of 600 m on 16 levels, with workings extending laterally some 1.6 km, and as new reefs were discovered the workings extended beneath parts of the township. Over their long life the mines produced 1217 tonnes of gold-silver bullion from processing 12.2 million tonnes of mined ore. In the early-1980s drilling proved large reserves of gold and silver ore remaining in stock-work zones between the previously mined lodes. This led to a new era of mining at Waihi with the opening of the Martha Hill open pit in 1988. A series of three sink holes have formed above unfilled stopes of the Royal lode. In 1999 a sudden collapse crater 40 m in diameter occurred near an occupied part of Waihi, placing in danger several houses and a busy street. This crater formed close to a similar crater that occurred in 1961. The 1999 collapse resulted in subsurface investigations and risk assessment studies being commissioned by the local Hauraki District Council. However, a further 50 m diameter collapse crater in December 2001 formed in a residential area, swallowing and wrecking an occupied house, fortunately without injuring its five occupants. Two other houses were perched on the crater rim. The 2001 collapse led to an acceleration of the work being carried out by the Institute of Geological and Nuclear Sciences Ltd. (GNS) to identify the extent of the old underground workings at Waihi. For the risk assessment detailed rock mechanics analyses were made to consider the stability of the underground mine stopes, in terms of the stope back, hangingwall, footwall and crown pillar failure mechanisms, as well as void migration. The collapse crater areas were analysed using using several methods, including analysis to simulate the probability of void migration from unfilled stopes to the surface using the @Risk program. The analyses show that in the cases of the actual collapse craters, the voids have a high probability of migrating to the surface, thus providing a method of testing the void migration modelling. Modelling analysis applied to the remaining stopes of the old underground mines show there are further areas where void migration from unfilled stopes has a high, medium and low probability of reaching the surface as a collapse crater. The locations of these probabilistic hazard zones were outlined using the @Risk modelling and deterministically by using the dimensions of the historical collapses applied along the length of the stopes. Consideration of the æincubation periodÆ (the time interval between the cessation of mining and the occurrence of collapse) and comparisons with mine subsidence histories overseas, indicates that further collapses are likely to occur over the next 50 years. Risk assessment estimates made using property values and occupancy levels within the three hazard zones, were compared with Societal and Individual Risk criteria. Results indicate that safety within the high and medium zones may be unacceptable.

Jan 1, 2003

Over the last 100 years in the Polish mining industry considerable work has been done to assess optimum slurry, develop flexible delivery systems and adjust the fill technology to a wide variety of mining and geological conditions. Sand or industrial mineral waste materials for the backfilling of underground voids are used to control ground movement and surface deformation. This paper discusses various criteria to be considered in the preparation of a fill, including slurry properties, mine infrastructure, mining geometry, placement methods and the purpose of the backfill. This paper presents laboratory and in situ test data on the influence of materials parameters on the slurry flow in a pipeline system, stiffness, permeability, binding time and strength of a backfill, on the distribution of mixture in underground voids or the penetration between roof fall materials.

Jan 1, 1998