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By T Purvis, Z Liu

Ernest Henry mine (EHM) is an underground sublevel caving mine located in north-west Queensland with a production rate of 6.4 Mt/a. The mine has sublevels spaced with a 25 m vertical interval. The production process on each level starts with the drilling and firing of a blind uphole rise to start the slot extraction. These rises are fired as a single shot and routinely need to achieve a design height of 22 m to 30 m depending on the local mine geometry. If the rise fails to perform as designed then the production phase of the level is delayed with significant rework required to remedy the situation.This paper describes the process that the EHM team has followed to improve the first time performance of each rise. The improvement process commenced with a review of results from previous rises and resulted in the identification of a number of improvement opportunities. A revised holistic approach was established for the process, which included involvement from operators and engineers. Through continued measurement and review of rise performance, inputs to the process were improved to a point where reliable results can now be expected. The successful performance of subsequent rises has been verified through a comprehensive quality assurance quality control (QA/QC) program. Before quality control processes were implemented, the success rate of blind uphole rises was only 11 per cent (one out of nine rises) at EHM. In comparison, the success rates have been vastly improved to 25 per cent (one out of four) and 75 per cent (three out of four) respectively following two stages of improvements. This paper concludes with the ‘current’ series of best practices used at EHM and recommendations.CITATION:Purvis, T and Liu, Z, 2017. Improving the performance of blind uphole rises at Ernest Henry Mine – a case study, in Proceedings 13th AusIMM Underground Operators’ Conference 2017, pp 335–340 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 16, 2017

By Y Yang, J Skrypniuk

The Jinfeng mine is Sino Gold's flagship project and is the second largest gold mine in China. Sino Gold Limited (SGL) holds 82 per cent equity in the Sino-Foreign joint venture Sino Guizhou Jinfeng Mining Limited (SGJML) with a Chinese partner. Jinfeng is located in a relatively remote site in southwestern Guizhou province. The orebody is considered to be the largest known Carlin type deposit in China. Jinfeng Plant has the world's third largest BIOX« bacterial oxidation facilities (790 t/d), treating highly refractory concentrate generated from crushing, semi-autogenous grinding (SAG) and ball milling and bulk sulfide flotation operations. The Jinfeng Plant construction started in February 2005, commissioning was completed in April 2007, and commercial gold production was achieved in September 2007. This paper describes the successful operations of Jinfeng Plant over the last two years. The key events of the project development are described, from the project background and process design, through to the commissioning and achieving design mill throughput of 3600 t/d resulting 180 000 ounces of gold per year. Process aspects of the BIOX« and carbon-in-leach (CIL) operations over the last two years are discussed which illustrate a very high BIOX« oxidation rate (more that 97 per cent) and excellent CIL recovery (more than 96 per cent). The management of the Jinfeng plant CIL tailings detoxification and filtration is described, and Jinfeng has became the first BIOX« processing plant to have achieved dry stacking of detoxified and pressure filtered CIL tailings. Current efforts to recover cyanide from CIL detoxified solution and the achievement of a zero discharge site water balance are also introduced. Many improvement projects have been made over the last two years which have culminated in a 15 per cent increase in mill throughput over the design and BIOX« CIL recovery increasing from 92.5 per cent to 96 per cent. Significant operating cost reductions from lowered of acid, lime and cyanide usage through process modifications and technical innovations are discussed.

Jan 1, 2009

By C Tickell

Achieving occupational health and environmental noise objectives is a major consideration in the planning or operational phase of resource development and industrial projects to meet the needs of the workforce and community and comply with legislative requirements. For material handling systems, ventilation plants, mobile equipment, process plants and fixed infrastructure, noise emissions need to be considered at the design phase. The preferred approach is to provide noise emission technical specifications, but in many cases this is not stipulated. An occupational noise requirement, such as ‘not to exceed 85 dBA at 1 m’, is often provided, but this will not achieve the required occupational or environmental noise objectives and may cause overly stringent requirements when they may not be needed. It should be noted that when developing the technical specification, measuring compliance needs to be taken into account as, in some cases, measuring may be very difficult or even not possible.This paper will discuss the requirements for providing an effective noise specification that ensures the environmental and occupational noise objectives are able to be achieved and that, once installed, compliance can be measured. It discusses planning such as when to set the objective, correlating the appropriate objectives for the environmental and occupational noise requirements, allowing for measurement tolerance, providing a suitable criteria and data format for the suppliers to respond to and methodology to measure compliance. Different phases of a project require different approaches to planning for noise management and these will be discussed in the paper. Examples from 35 years of industry experience will be included.CITATION:Tickell, C, 2016. Preparing effective specifications for occupational health and environmental noise objectives in mining project design and delivery, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 781–788 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By E N. Sparg, O D. A Deuchar, F Needham

Decline shafts are an attractive option to both new and existing mining operations where there is a need to access an inclined orebody deposit via on-reef development so as to generate a return in the shortest possible time. There are many different technologies that are available to transport men, material and rock in incline shafts. This paper focuses on the applicability of two hoisting technologies for decline shafts, namely endless and direct rope systems. The pros and cons of each system are reviewed. A common concern with direct rope haulage systems is the possibility of generating slack rope during deceleration. This paper illustrates the issues involved in designing a system so as to avoid the possibility of slack rope. In conclusion, the key factors relevant to the selection of endless or direct rope haulages for a particular decline application are reviewed. The paper is a joint submission by FFE Minerals-Vecor and Qualter Hall UK.

Jan 1, 2005

By D Engelhardt, G Lane

The Cadia mine has shifted from an open pit operation to the Cadia East underground panel cave. The resulting increase in milled tonnes, more competent ore and the decrease in fines production through shifting to panel caving were predicted to require an increase of over 25 per cent in installed power. This expansion was accomplished via the installation of secondary and high pressure grinding rolls (HPGR) crushing of the ore, with the semi-autogenous grinding (SAG) mill receiving a combination of primary, secondary and HPGR crushed feed. This design, criteria and rationale for selection was presented at the SAG Conference 2011. This paper reports on the initial impact of secondary and HPGR crushing on the circuit performance with the new panel cave feed.CITATION:Engelhardt, D, Lane, G and Powell, M S, 2014. Cadia expansion – the impact of installing high pressure grinding rolls prior to a semi-autogenous grinding mill, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 233–240 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014

The Health Tracking project is one of five projects being undertaken as part of the Minerals Industry Cooperation Initiative (MICI) û a national initiative sponsored by the Minerals Council of Australia. The aim of the Health Tracking project is to assess the practicality of ways to demonstrate the monitoring of hazardous exposures and the occurrence of related occupational illness and disease and development of management systems and strategies at a national level. This second stage of the project will be completed in 2005 and will cover four areas: pilot development of a comprehensive job exposure matrix (JEM) for the minerals industry; development of both proactive and reactive occupational illness and disease metrics; recommendations regarding appropriate health tracking models; and provision of best practices guidelines for management of occupational health. The synergies between these areas will establish the path towards an effective national occupational health surveillance system and the development of effective prevention strategies and policies.

Jan 1, 2005

The Gold Ridge Mine is an open-cut gold mine in the Solomon Islands. The mine is owned and operated by Gold Ridge Mining Limited, a wholly owned subsidiary of Ross Mining NL. At the invitation of the Solomon Island Government, project construction commenced in July 1997 and gold production commenced in August 1998. The mine is the countryÆs first, and represents a major milestone in the development of the Solomon Islands. At the time of project approval and construction, there was a growing awareness in the country of the potential impacts of mining in the tropics, partly due to unfavourable publicity surrounding a number of other mining operations in the Pacific region. The management of environmental impacts was therefore an important consideration in the approval of the project, and continues to receive a high level of attention from the Government and community. Ross Mining did not commit to the Gold Ridge Project until it had satisfied itself that all waste rock and tailings could be safely contained on-site, and that the standards normally expected of a mine in Australia could be met. Ross Mining approached the approval, construction, and operation of the Gold Ridge Mine with a set of operating principles that met Government and community concerns. These were:best practice environmental management; operation of the mine in accordance with standards expected of mining operations in Australia; independent peer review of key technical aspects; on-going consultation with Government and community; and equitable transfer of wealth to landowners and the local community. As a consequence, the Gold Ridge Mine has developed into a successful mining operation with a high level of support from local landowners, the general community and the Central and Provincial Governments of the Solomon Islands.

Jan 1, 1999

By P K. Singh

Recent advancements in understanding the detonation process are noteworthy, but they are still based on somewhat hypothetical situations. The actual variables that are essential parts of normal blasting practice have not yet been taken into account in such treatments. These include the various initiation practices employed to detonate a column of explosive, from single point initiation to multi-point initiation in blast holes, and the effect on detonation characteristics of both detonators and explosives under multi-deck and multi-hole blasting conditions. The in-the-hole velocity of detonation (VOD) of an industrial explosive is dependent on explosive’s charge diameter and blasthole diameter. The relationship between blasthole diameter and VOD provides a fundamental guideline to the rate of energy conversion and energy release within the detonation front on the interaction of explosives with the confining medium.The in-the-hole VOD of explosives was measured at four experimental sites in India for different blasthole diameters, ie 150 mm to 311 mm, but for identical explosive composition being same particle size, density, viscosity and loaded into blastholes with the same degree of confinement. The results of the studies demonstrated that there is definite relationship in in-the-hole VOD of the explosive and the diameter of the blast hole. The study also confirmed that the explosives initiated with concentrated boosters yielded higher VOD in comparison to those explosives that were initiated with multi-point priming. The measured increase in VOD of explosives for increasing diameter of holes was up to 24 per cent. The rate of change in in-the-hole VOD of explosives increases with increasing blasthole diameter. It can be further stated that the in-the-hole VOD of the explosive reaches a fairly constant value after reaching a limiting/threshold diameter of 311 mm.

Nov 8, 2011

By D Mather, H R. Asche

"In the civil tunnelling field, the use of tunnel boring machines (TBM) has now overtaken the use of conventional excavation methods (drill and blast / roadheader). This is due to a number of reasons, including the increasing availability and reliability of TBMs, the ability to deal with a wider range of face conditions, and the reduced excavation cost that TBMs can bring.Mining companies have spearheaded the advances in shaft boring by mechanised means, both in blind and raise boring. However, mining companies have been slower to adopt mechanised tunnelling.When contrasted with a conventional mining contract, there are good reasons why TBMs in mining applications are relatively rare. A conventional decline contract may have very little geotechnical information. The decline alignment can be subject to change as the tunnelling progresses. The infrastructure requirements are less for a conventional decline, and the sunk cost prior to excavation commencing is lower. Contract documents can be very simple.The history of TBM use in mining is reviewed and lessons are described. From the case histories and lessons learnt, the paper identifies ways that mining companies can maximise the potential benefit of TBM technology.We believe that despite the additional requirements for TBM declines, the cost and time advantage to mining companies is very attractive. The challenge is to recognise and to meet the requirements for success in a TBM drive to achieve the advantages of: faster advance rates reduced rock damage/overbreak reduced support requirements uniform muck characteristics greater personnel safety.From the case histories and lessons learnt, the paper identifies ways that mining companies can maximise the potential benefit of TBM technology.CITATION:Asche, H R and Mather, D, 2014. Use of ?tunnel boring machines in the mine environment, in Proceedings 15th Australasian Tunnelling Conference 2014, pp 655–662 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Sep 17, 2014

By A Huebner, A Noack

Companies all over the world are very sensitive concerning their IT and network security. In most network connected technical installations and machines however, network security is not taken into account to a significant extent: insecure protocols are run, unencrypted information is exchanged freely and even broadcasted wirelessly and networked machines are accessible via insecure file transfer protocol (FTP).What happens in case of malfunctions of such technical installations? Who is responsible? Who can be held liable in case of accidents? The first computer worm for automation systems (æSTUXNETÆ) (Symantec, 2010) was discovered during 2010.The paper is intended to create sensitivity among decision makers for potential security and resulting safety leaks and points out the current status quo in technical network security. It outlines best practices for secure networking and procedures for remote access and remote software updates on stationary equipment and mobile mining machinery. It describes how to ensure authentic and genuine configurations and software targets and how to ensure secure communication for autonomous and remote controlled equipment. For such equipment in particular, the following statement should apply: æThere is no safety without network securityÆ.

Sep 26, 2011

Coal mining ceased at Strongman Mine this year after 70 years of production. Underground mining finished in 2003 and opencast methods began in 1998. During the life of the mine, 8 million tonnes of coal was extracted from two underground mines and 1.2 million tonnes removed through opencast methods. Strongman Mine is within the Grey Coal Fields; various seams have been extracted from the Rewanui Coal Measures. Coal extracted was predominantly of thermal or semi-soft specifications and characterised by low sulphur and low ash.   The area has steep topography, high rainfall (>3000 mm/yr) and is particularly exposed to westerly quarter winds. Strongman 1 and 2 underground mines are located in the steep, narrow valley which leads to the Strongman Opencast at the top of the valley. Subsidence from underground mining combined with spontaneous combustion, has resulted in an underground fire which has had substantial surface effects. Opencast mining in the steep topography resulted in several landslides at the perimeters of the site. These factors, along with water management, topsoil management and erosion control have added to the complexity of rehabilitating the site.   Rehabilitation of the site is well underway, including infrastructure removal, final landform creation and revegetation of the Strongman Opencast footprint (~45 hectares). Some innovative methods of rehabilitation have been trialled. Successful trials such as helicopter-seeding and moss hydro-seeding on highwalls are now routinely used along with traditional revegetation practices. 18 hectares disturbed land has been replanted with 88 000 seedlings, and another 200 000 seedlings are scheduled for planting over the three years. Fire management is an ongoing challenge; however thermal photography shows a steady decrease in hot areas which have been contained by grout curtains.   Mine closure is some time away and will occur after all standards set by Solid Energy and regulatory bodies are achieved.

Jan 1, 2006

By R Mann, R Prasad, S Vink, V Nanjappa

The level of salinity that various aquatic organisms can tolerate without incurring any adverse effects is dependent on several environmental and evolutionary factors. These factors include the relative concentrations of different types of dissolved salts in the water that makes up their habitat, the regimes to which organisms are exposed to waters of differing salinity levels (including naturally derived variations), the degree to which an organismÆs life history stages have adapted to salinity, an organismÆs ability or behaviour to avoid adverse levels of salinity and an organismÆs capacity for osmoregulation.Release of saline water into rivers of the Fitzroy catchment has created concern about the impact on aquatic organisms. Not only is salinity itself a stressor on organisms but different ionic compositions will moderate the effects. Ecotoxicology experiments were conducted using artificial saline water based on mine water chemistry using sensitive macroinvertebrates collected from the catchment, as well as a range of laboratory organisms in accordance with the ANZECC and ARMCANZ (2000) guidelines. The 95 per cent ecosystem protection value calculated from species sensitivity distribution derived from the commercial tests was estimated to be ~2.0 mS/cm. For the protection of 99 per cent of the species the salinity has to be reduced by more than 50 per cent to 0.91 mS/cm. The electrical conductivity (EC) values, derived by commercial testing and species sensitivity distribution in this study suggests that salinity contaminant trigger values previously developed using a referential approach for protection of aquatic ecosystems from saline mine water releases in the Fitzroy may be conservative.CITATION:Vink, S, Mann, R, Nanjappa, V and Prasad, R, 2013. Determining the impacts of salinity on freshwater organisms, in Proceedings Water in Mining 2013 , pp 149-154 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 26, 2013

By C D. Rose

"The primary objective of this paper is to demonstrate a different approach to predicting and verifying mechanical sampling system precision. Early in the year 2011 an experiment was conducted to evaluate the sampling precision being obtained by a three-stage falling-stream mechanical sampling system for coal owned and operated by Peabody Energy. This system collects samples from lots averaging approximately 14000 t being loaded onto rail cars at a flow rate averaging about 9000 t/h. In phase 1 of the experiment, a total of 60 increments were collected in a two day period at preassigned intervals using a cross-belt sampler located on a conveyor belt feeding a silo upstream of the sampling system under evaluation. Coal variability parameters were calculated from the resulting laboratory analysis data using the gauge-invariant fractal model developed by the author.Estimates of precision of the three-stage system as a function of the number of increments were calculated using the variability parameters determined in phase 1. In phase 2 of the experiment, duplicate samples of 30 lots of coal were taken by the three-stage sampling system, enabling calculations of the precision being achieved by the system. Phase 2 precision estimates are in reasonable agreement with those of phase 1. Conclusions drawn from the experiment include the following: Experimental variograms or the equivalent correlograms are essential in understanding sampling issues and for designing a sampling system to meet specific precision requirements. Consensus coal sampling standards provided by ISO and ASTM may be improved by treating all stages of a mechanical sampling system as æsamplingÆ rather than considering downstream sampling stages as æsample preparationÆ, to be treated in a separate part of the document. The coal industry would profit from use of methodology for routinely monitoring the overall measurement precision and the precision of the individual components of measurement: sampling, sample preparation and laboratory testing. This would not only give necessary credence to the measurement results but would also no doubt, lead to more efficient sampling system designs.CITATION:Rose, C D, 2012. Evaluation of precision being obtained by a three-stage sampling system for coal, in Proceedings Sampling 2012, pp 115-124 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Aug 21, 2012

By C Dell

Hillgrove, situated on the New England plateau of New South Wales, is an area rich in history and resources. Key resources are predominantly antimony, gold and scheelite and the area surrounding the historical field is environmentally sensitive and topographically challenging. Since acquiring the Hillgrove leases, Straits Hillgrove Gold has undertaken a significant exploration program on these historical mining areas with the goal to return the field to production. This exploration program has enabled Straits to significantly increase the resource base and has subsequently enabled the planned redevelopment of Hillgrove to be realised. In October 2006, installation of mining infrastructure and the initial stripping of existing development had commenced. To successfully redevelop Hillgrove, Straits has had to adopt a highly mechanised, trackless, diesel mining operation which will see the production rate commence at an initial rate of 250 kt/a of ore from a narrow vein environment. This ore will be processed on site to produce antimony metal, gold bullion and a scheelite concentrate.

Jan 1, 2008

By Whiteman P. C, Stacey G. S, Hunter G. D

Processing of lead-zinc and copper ores by Mount Isa Mines Limited produces large quantit- ies of concentrator tailings waste which is pumped as a slurry to special dams where the solids are allowed to settle and dry out. These areas are unattractive and show no signs of encroachment by plant life even though the surfaces of some dams have remained undisturbed for more than a decade. During 1970 Mount Isa Mines Limited commenced a long term research program in conjunction with the Department of Agriculture, University of Queensland to deter- mine possible methods of establishing a plant cover on this material. Research has defined the major factors limiting plant growth in the tailings medium. Modification of the edaphic conditions through fertilizer inputs, particularly of phosphorus and nitrogen, and alteration of "soil" physical properties by incorporation of mulching mater- ials, provided conditions which allowed plant growth. The outstanding "soil" amendment treatment was incorporation of fly ash, a waste product of the company's coal fired power stations. A range of crop and pasture species have been selected which have grown well with adequate irrigation under the amended conditions in the field. Further research is assessing a range of native plant species and agronomic techniques to provide a stable plant cover on the tailings dams.

Jan 1, 1974

By S R. Pecover

AustraliaÆs opal and sapphire mining industry has fallen from its peak in the 1980s and 1990s into a significant low today. This is not due to exhaustion of the resource, but instead an over-reliance of the Australian miner on achieving a fair price for the gemstone product from offshore middlemen dealers. Gemstone and geological research is also at a low as Federal higher education expenditure has fallen with research institutions relying increasingly on private funding in an environment of restricted autonomy and flexibility for researchers. What little remaining research skills the universities have is being bled into the private sector as a result of the mining boom and encouraged by lower than average academic salaries. Nevertheless, some highly innovative research has been taking place, often by self-funded individuals and retired academics simply with a desire to advance the understanding of the particular branch of science in which they are interested. New models for the formation of sapphire and opal are now beginning to be applied to the exploration for these gemstone commodities. This research, together with well thought out plans for managing the gemstone product through its value-adding steps to the jewellery retail level, has the potential to bring about a resurgence in the Australian gemstone industry.

Jan 1, 2008

By R Sterk, B Reid

The Konongo Gold Project is located on the western margin of the 125 Moz Ashanti Gold Belt in Ghana, West Africa. It is situated 60 km along strike of the world-class mineral system at Obuasi and is interpreted to lie on the same controlling regional shear system.The project is operated by Signature Metals, a subsidiary of the Liongold Corporation, and is managed and funded by the Liongold Corporation.Historic underground operations at Konongo produced 1.6 Moz Au at a head grade of 11.8 g/t Au, from eight operations spread along 16 km of the shear system. Mining focused almost exclusively on free-milling gold in quartz, ignoring the gold-bearing sulfide mineralisation associated with the quartz veins. Underground mining ceased in 1986.In 2013, Signature Metals re-focused the program at Konongo to assess the viability of mining the sulfide ore sustainably. This led to the first campaign review of the historic underground data and resource potential since mine closure. The Obenemase mine was the first of the eight operations to be assessed as part of this campaign.Large amounts of legacy data have survived for Obenemase and several historic resource estimations have been completed based on these data. The data typically consisted of hand-drawn sections and plans, and ledgers of commonly incomplete drilling and sampling data. Some drill core have been lost over time, but a large amount of quarter-core and half-core as well as pulps and rejects are still available. Previous resource estimates had a low confidence value because all the available assay and geological data were integrated effectively with the estimates, resulting in a lack of understanding of both grade and geological continuity.This project built a new geological model for Obenemase that greatly enhances the understanding of the controls on mineralisation using a thorough approach of re-surveying, re-cataloguing and re-logging. This model led to an increased degree of confidence and a subsequent upgrade of resource classification, and created several previously unrecognised strong exploration targets. The resulting resource estimates increased the value of the project by 100 per cent.This paper emphasises and highlights the importance of a well-understood geological model on the confidence of a resource estimate and how this may directly impact on the project’s ‘bottom line’.CITATION:Sterk, R and Reid, B, 2014. The Konongo Gold Project, Ghana – an example of how geology makes all the difference to a resource estimate, in Proceedings Ninth International Mining Geology Conference 2014 , pp 467–476 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 18, 2014

By R Stead

So many ceramics look the same, but are they?In the past 20 years, there have been significant changes in the materials available, as well as changes to the supply chain, for ceramics used in wear applications in the hard rock mining industry. The biggest change in supply has been from the Chinese market, with many suppliers promoting their products as æstate of the artÆ. Some of them are state of the art, but are they all? There will be some concluding remarks in this respect.There are still some outstanding new developments coming from the more traditional suppliers and these should not be ignored. However, as an end user, how can one be sure that the product received meets the technical specifications of that material?This paper will address some of the questions on how to differentiate between different materials by giving a technical overview of the current (but not exclusive) range of popular ceramics, plus incorporating how these ceramics are used in process plant products by presenting case studies. The presentation will include technical data coupled with micrographs of various ceramics to illustrate just why they are different.It will also be shown that by careful selection of the wear material, it is possible to gain significant benefit when using superior materials in an ore processing plant. The impact of cost of the products, life, process efficiency, and reduced maintenance costs will be considered using cyclone components as an example.The properties (including the microstructures) of the various ceramics will be compared to the application in order to get some understanding of what is considered good or bad.Misra and Finnie (1982) summarised their paper, æA review of Abrasive Wear of MetalsÆ by saying:à it is difficult to give guidelines for selecting materials for abrasive wear resistance. Each application is a different one, and a design engineer has to take into account various other factors such as impact, fatigue and corrosion which are often coupled with abrasive wear. The same applies to ceramics.CITATION:Stead, R, 2013. Applications of ceramic wear materials in the gold industry, in Proceedings World Gold 2013, pp 325-330 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

By H Wright

Black Rock Cave (BRC) is a sublevel cave which was developed in 2018–2020 and has been in production since November 2020. BRC is part of the Mount Isa Mines complex and extracts a leached orebody comprising of high-grade chalcocite ore, situated below the historic Black Rock Open Cut workings. The mine is owned by Mount Isa Mines and operated under contract with PYBAR Mining Services. In 2021 a number of rockfalls occurred throughout the mine and were increasing in frequency. This culminated in a major rockfall on the decline in June 2021, after which the decision was made to withdraw all persons from the mine, initiate rehabilitation and conduct further investigations to deduce a safe method to provide long-term support. The rockfall investigations have shown that the corrosive nature of the highly leached rock mass can consume a split set in less than 18 months. A review of potential corrosion resistant ground support methods concluded that steel split sets have a safe lifespan of six months at BRC, and that all workings must have corrosion resistant support installed prior to exceeding the safe life of the friction bolts. The review recommended the use of 4 m cable bolts as the most suitable method of corrosion resistant support. This new support system, and the requirement to rehabilitate all mine workings within the leached orebody, had an impact to the schedule and an effect on both equipment and manning levels at BRC. Accelerated jumbo rehab allowed access to the production levels within two months of the rockfall. Cable bolting then followed the jumbo bolting in all leached areas. The direct impact has been ten months of reduced production, due to night shift closures of the decline to enable cable bolting. The impact to the mine has been minimised by the small flexible team that enabled the mine plan to change rapidly and often to accommodate the challenging conditions. In less than two months from the rockfall event, production had resumed. Within ten months of concluding that the mine required; full rehabilitation, a new support system and a full re-schedule, normal mining operations had restarted, with pre-event productions rates being achieved.

Mar 29, 2023

By K Williams, A Lavrinec, V Gurung, D Ilic

The moisture content of iron ore during handling can range from the dust extinction moisture at the point of arrival at the port to the transportable moisture limit at the point of loading ships for maritime transport. Moisture content and ore composition, specifically fines content, have a large influence on ore flowability. Typically, elevated moisture can result in bottlenecks, downtime and lost productivity due to build-up, conveyor carry-back and blockages, increasing maintenance costs. On the other hand, low moisture can result in increased dust emissions influencing the environmental footprint and product losses. Managing the use of water across the supply chain is therefore critical for service life of equipment, productivity, but also has environmental and social impacts, affecting the social license to operate. Previously, experiments have shown that oscillations induced in iron ore during handling and transport can result in movement of moisture through the ore. This kind of moisture migration depends on the nature of these oscillations, such as the undulation of idlers during conveying, the inherent ore properties and the initial moisture content. Moisture has been observed to move either upwards and/or towards the bottom of the burden. These effects can be exploited to remove excess water from the ore influencing handleability and operation, however, the actual mechanisms of moisture migration are currently poorly understood. The study presented herein involves the use of simulation to examine moisture and ore interactions. Simulations using discrete element method (DEM) and coupled with smoothed particle hydrodynamics (SPH) are implemented to investigate the behaviour of moisture in wet ore in the presence of oscillation. This is conducted at a fundamental level first using glass beads and water which is then compared to iron ore at high moisture content. The results of the modelling are discussed in view of experiments conducted.

Sep 18, 2023