Search Documents

By M L. Muller, A R. O’Donnell

The Mount Isa Mines (MIM) Copper Concentrator has an extensive history of reagent trials, with different reagents coming in and out of favour over the years. The research and use of carbon depressants is particularly prevalent, as carbonaceous pyrite is a major source of concentrate dilution. Years of research led to the use of naphthalene sulphonate due to its excellent carbon depression properties. However, due to rising reagent costs carbon depression ceased in the late 1990s. This led to the loss of knowledge about the use and value of naphthalene sulphonate. Cyanide is used at the Copper Concentrator for the sole purpose of pyrite depression and over the years multiple projects have been devoted to finding alternatives to it. In 2012 the neighbouring MIM Lead-Zinc Concentrator replaced cyanide with naphthalene sulphonate which resulted in cost savings and the elimination of a hazardous reagent. In 2013, plant trials were conducted at the Copper Concentrator in hopes to replicate the outcomes obtained at the Lead-Zinc Concentrator. The results of the trials conducted at the Copper Concentrator showed that naphthalene sulphonate could not replace cyanide and this work was set aside to pursue more promising projects. Further research conducted in 2014 found that mineralogy and a better understanding of the depressing mechanism of naphthalene sulphonate held the key to improved pyrite depression at the Copper Concentrator. The findings showed that Mount Isa copper ore contains two forms of pyrite; euhedral pyrite (cubic pyrite) and framboidal pyrite (carbon rimmed spheres of pyrite), both of which require different reagents to sufficiently depress them. Naphthalene sulphonate was found to be an excellent carbon depressant, suitable for depressing graphite and framboidal pyrite, whilst cyanide specifically targets euhedral pyrite.In 2015 laboratory test work was conducted to examine the use of naphthalene sulphonate in conjunction with cyanide to selectively target both forms of pyrite. This work led to a full plant trial, the results of which showed a significant increase in plant performance, with higher copper concentrate grades and recoveries being achieved. This paper aims to focus on the benefits and importance of understanding past work and linking a detailed knowledge of feed mineralogy to reagent selection for improved plant outcomes.CITATION:O’Donnell, A R and Muller, M L, 2018. Selectively targeting hydrophobic gangue minerals at the Mount Isa Mines Copper Concentrator, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 413–421 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

"Cash flow modelling during project evaluation is enhanced when probabilistic methods are applied to the inputs. One of the important inputs is the quarterly production profile. Typically, the steady-state production profile provided to project evaluation practitioners is deterministic, with each quarter the same as every other quarter. This is unrealistic as actual production profiles from existing mines exhibit a range or quarter-on-quarter variance. Monte Carlo stochastic simulation of the production profile can be used to provide a range of possible outcomes, but how are these ranges selected? This paper describes the use of quarterly production variance from a large database of mines worldwide as a benchmark to inform the appropriate selection of ranges. The coefficient of variation is used to rank the production from mines, with quartile analysis applied to indicate industry best, median and worst variation. Due diligence of existing mines and evaluation of future production performance can be quantitatively assessed using this approach. Examples of the effect on value are provided.CITATION:Stewart, C A, 2016. Production variance benchmarks and their use in project evaluation and due diligence, in Proceedings Project Evaluation 2016, pp 201–213 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 8, 2016

By R Varden

This paper summarises the process taken to simplify 35 ground support standards accounting for the multiple development profiles, dynamic geotechnical environment and the practical safety implications of a large-scale change in the ground control standards. This reduction was required after an incident involving incorrect standards being issued. The subsequent investigation identified that: • Selection of ground support standard for a mining instruction (MI) is not straightforward due to multiple standards, standards not reflecting current reinforcement used and complex geotechnical environment being encountered. Instead, site-specific ground control instructions were being issued. • Ground support standards were hard to follow and confusing, errors were present and not all standards to scale. • Ground support standards being used did not reflect what was being installed, ie bolt type incorrect and mesh orientation different. • No process or tier action response plan (TARP) for operators to follow for ground control standard noncompliance. • No justification for ground support standards being used in the current geotechnical environment. • No process for ground support standard selection and thereby no paper trail to document and assess adequacy of performance. A project was undertaken to reduce and simplify the ground support standards, produce a justification document to support ground support design and develop a process for site practitioners to identify the type of ground support standard required for the mining instruction. The exercise of rationalising the ground support was met with some challenges, including: • Technical aspects to determine the level of demand and the capacity for each ground support scheme. • Training the geotechnical engineers how to determine the level of risk for each area. • Winning over other technical services staff and the underground mining contractor of the new approach and then implementation. One of the major successes was the acceptance by the underground operators who found the system simplified their work and gave them increased confidence in management of seismicity. The rationalised ground support standards have now been successfully in place for over two years.

Mar 29, 2023

By S B. Fitch, S A. Wilson, A J. R Barr, P R. Searle

Improving the safety culture and performance of any operation is a fundamental goal of every mine operator. Methods of implementing, or changing a culture have developed from the early methods of operant conditioning, for example rewarding crews for achieving nominated safety milestones i.e. 3 months Lost Time Injury (LTI) free through to the current model of engaging a workforce through education and empowerment. As a large scale and mature operation with multiple contractors, Telfer has been exposed to numerous programs throughout its history. This has provided the opportunity to build on and complement these systems by integrating key elements from each. SAFE 360° is a new approach developed to engage the workforce in a holistic approach to encourage positive behaviours across all facets of an individual’s life which results in a focus on situational awareness at all times, rather than being workplace specific. It is based on three key modules: • Emotional Intelligence • Mindfulness • Situational Awareness Each module has a series of modules that help enhance the individual’s sense of self, leading to an ability to self-reflect and self-manage whilst empowering them with the moral courage to challenge their peers to raise standards. Since commencing this SAFE 360° behavioural safety risk management journey in November 2017, we have witnessed a change in the way our workforce engages with each other, their workplace and with management. There has been an increase in hazard perception, identification and ownership of issues, and we have seen a significant decrease in site TRIFR rate from 13.7 to 5.7 (as of April 2019). This paper will provide an overview of the program, how it has been implemented, case studies to demonstrate outcomes and KPIs used to measure effectiveness.

Mar 15, 2021

By P Mikula, B Darlington, J Graham, P Young

In underground mines experiencing dynamic events, there is an ever-present challenge to design and maintain a capable ground support system. One key component of ground support systems is surface support, which serves the essential roles of retaining failed rock and transferring forces generated by surface displacement to rock bolts or other support elements. Observations underground show that in many instances, standard mesh panels alone do not provide sufficient dynamic support to retain substantial bulking failures imposing displacement onto mesh, and in such cases Mesh straps and W-straps may be employed. Determining the performance of surface support elements proves to be difficult, with a multitude of variables at play in the underground environment. Quite comprehensive work has been completed on laboratory testing of surface support systems; however, very little work has been conducted on in situ dynamic testing of Mesh straps and W-straps. In 2019 in Western Area’s Flying Fox Mine, in situ dynamic testing was conducted on a series of Mesh straps and W-straps using Sandvik’s in situ Dynamic Test Rig (DTR). The testing regime applied impact energies from 5.1 to 15.3 kJ to Mesh straps and W-straps. The performance of the straps that did not fail was a maximum absorbed energy of 9.3 kJ and 14.2 kJ for the Mesh straps and W-straps respectively. The testing successfully demonstrated the ability of Sandvik’s DTR to test not only rock bolts, but also surface support elements, creating new testing and research possibilities. The testing also provided important design guidance data that is not practicable to obtain using laboratory dynamic testing facilities.

Nov 29, 2022

By J Rutter, D Francois-Bongarcon, M Federov, N Odiar, M Scott

There are two fundamental methods for metalliferous sensing of primary crushed ore available for deployment at operations. These methods can be classed as surface measurement techniques (including XRF, LIBS, NIR, SWIR) or penetrative/semi-penetrative measurement techniques (including PGNAA, PFTNA, GAA, MR). While the individual sensing technologies exploit different physical phenomena to measure metal content, penetrative sensor measurements of grade are often regarded to be superior to surface measurement techniques due to the much larger sampling volume penetrative techniques provide. Surface sensing techniques often utilise simpler, established technologies that have considerable benefits in the speed of analysis, capital costs, ease of deployment, social license to operate and operational safety. This paper investigates whether surface sensing techniques achieve adequate sampling representativity of primary crushed rock mass to provide economic benefit over penetrative sensing technologies for bulk ore sorting applications. The paper details the methodology used to assess whether surface XRF measurements change throughout various stages of comminution, and increased surface exposure, from primary crushed ore (top size of -175mm) to finely crushed product for assay (top size -2mm). The methodology was applied to 2 ore mineralisation styles, across variable metals and grades, to identify any associated opportunities and limitations to surface sensing techniques. The results assist in developing a method to determine if surface sensing and measuring via XRF is an adequate representation of the rock mass for bulk ore sorting applications and identify any associated limitations in particle size distribution, mineralisation or natural deportment strength to guide suitable application of surface sensing techniques.

Nov 10, 2020

By A Horeth, E Duggan, B Versiani, A Gooch

Iron ore screening plant productivity is strongly affected by the performance of the shuttle operation, with the control system robustness and associated strategies having a direct impact on utilisation and throughput rates. A number of aspects intrinsic to the methods and technologies traditionally applied on the motion control of shuttles are often observed to decrease the efficiency of the ore distribution process across multiple screening modules, which ultimately impacts the plant’s production. Those include the number of operational scenarios that are unmanaged by conventional discrete control logics which may intermittently lead to undesired events, such as ‘high level alarms’ and ‘low level interlocks’ in the screening bins. This outcome usually demands excessive manual intervention by Control Room Operators. A Reinforcement Learning (RL) Artificial Intelligence (AI) solution was deployed to control the motion operation of the scalping and products screening shuttles in an iron ore handling plant. The RL algorithm was trained in advance to handle multiple operational scenarios and generate optimised outputs. In nominal operation, the shuttles are moved in a modulating and highly predictive fashion over the whole range of safely reachable bins. When the need occurs, the AI control agent deviates from that modulation behaviour, limiting its travel range or moving to other groups or clusters of available bins by employing ‘bin jumping’ or ‘ore break’ strategies. The RL platform capabilities include the ability to learn in real time to account for and auto-adapt to new operational patterns and process changes whilst applying improved strategies for shuttle dwelling times, target setting and speed control. The deployed Reinforcement Learning AI solution has better managed the existing challenges associated with the shuttle operation and control, and resulted in a more efficient ore delivery process, superior operations stability and increased production rates.

Nov 8, 2021

By D McCoy

Titanium feedstocks are the building blocks of the titanium value chain. They can be mined directly, as is the case for ilmenite, leucoxene and rutile, or manufactured from ilmenite by extracting various quantities of non-TiO2 components from the ore by chemical and/or thermal processes.While feedstocks can be grouped into categories of materials with similar characteristics, they are essentially unique products from very different mining locations around the world. In fact, no two feedstocks are exactly the same. As such, the variations between the available feedstocks, in combination with the permutations in processing technologies to turn the feedstocks into titanium pigment or metal, mean that choices between feedstocks are specific to the location in which they are utilised.In this paper, the authors examine the key requirements of titanium feedstocks to the TiO2 pigment and metal sectors. Apart from the well known differences between feedstock choices for the sulfate and chloride process, the more opaque considerations in feedstock sourcing are examined.

Oct 5, 2011

By N Jamson, T K. Rohde

The Mine is an underground zinc (Zn), lead (Pb) and silver (Ag) operation in central New South Wales (NSW). Broadly speaking the Mine has two domains that require rehabilitation, the mine industrial area (MIA) and the tailings storage facility (TSF). The MIA has been used for the handling and processing of ore and contains elevated sulfate, sulfide and metals (Pb, Zn). The TSF receives the by-products of processing, that is, potentially acid forming (PAF) tailings which also contain elevate sulfate, sulfide and metals. Typically, the rehabilitation of a TSF involves two controls. Firstly, controlling the potential for PAF tailings to form acid rock drainage (ARD) by limiting interaction with oxygen. Secondly, once the tailings are unsaturated, limiting interaction with water (usually as rainfall) to reduce the potential for ARD to be transported to the receiving environment. These two controls are often employed in the form of a cover.In semi-arid environments there are many Australian examples of covers that have been built to limit interactions of mine by-products with oxygen and water. Typically, the covers contain one or more layers and are built from soil and rock which may include run-of-mine rock. The Mine however has limited supplies of stockpiled soil; and run-of-mine rock is not generated in large volumes because it is used as backfill underground. A cover design strategy was developed to cater for these limiting factors. The strategy identified soil, ore and rock accretion (the accretion) below the MIA could be a potential source of borrow material for the cover. The purpose of this paper is to describe the cover design process, the method and results of large (2 m tall) column trials that were used as a cost-effective way to trial three cover options and finally, the paper describes the water balance that was developed from the column trial results and subsequent modelling using SVFlux.CITATION:Rohde, T K and Jamson, N, 2018. Making use of potentially contaminating mine waste in cover design, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 285–298 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By D Morton, G Wallace

"Evolution Mining is the sole owner of the Mt Rawdon open cut operation, located 75 km south-west of Bundaberg in Queensland, Australia (Figure 1). It is a massive, volcanically hosted, low-grade gold deposit that exhibits excellent characteristics conducive to low cost mining and treatment.In 2014, Mt Rawdon began investigating initiatives to deliver higher mill throughputs without any significant capital expenditure or modifications to the existing processing plant. Various studies have shown throughput increases are possible by applying more blast energy, essentially by reducing feed size through blasting and leaving less work for the comminution circuits (Brent et al, 2013; Ziemski, 2011; Workman and Eloranta, 2003).Given that 53 per cent of energy used on a mine site is consumed by the comminution circuit, with only two per cent being consumed by drill and blast (Smith, 2013), it makes logical sense for a mining operation to align their drill and blast with their processing plant. The term commonly used when exploring this relationship is a ‘Mine to Mill’ program.Over nearly 12 months, various blasting options and Mine to Mill methodologies were tested at Mt Rawdon. Throughout the journey, it was abundantly clear that the Mine to Mill initiative is not as simple as making one technical or physical change and expecting an improvement. Rather, true sustainable improvements demand a paradigm shift across both the mining and processing cultures, where all departments are aligned and working towards the one outcome. This true overarching Mine to Mill mentality, enabled by Vistis™ 250 high energy bulk explosive, ultimately led to a sustained increase in throughput and profitability of the Mt Rawdon operation.Citation:Wallace, G and Morton, D, 2016. High Energy Bulk Explosives and Mine to Mill Focus – the Mt Rawdon Story, in Proceedings Ninth AusIMM Open Pit Operators' Conference 2016, pp 60–69 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Nov 15, 2016

By M Zlatev, S Silge

Producers of primary resources such as iron ore face the challenge of processing crude materials with increasing levels of impurities, which may result in the requirement for wet processing. This results in a significant increase in water usage, power consumption and operating costs. Given the remote locations of most operations in Australia (Stewart et al, 2013; Prosser, Wolf and Littleboy, 2011), the required volumes of power and fresh water for wet processing can be very difficult to achieve.HAVER&TYLER is renowned across the world for their screening technology in wet and dry processes. Its innovative Hydro-Clean® system represents a cost-effective and eco-sensitive way to clean any crude materials and material blends with a grain size distribution of 0–150 mm that are contaminated with adhesive clay, slit and other impurities.CITATION:Silge, S and Zlatev, M, 2015. Iron ore washing – achieve more with fewer resources, in Proceedings Iron Ore 2015, pp 519–528 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By A Jewbali, R Perry, R Inglis, L Allen

"The use of conditional simulation to characterise mine plan uncertainty is increasing for the assessment of risk in mining projects. While the development of grade uncertainty profiles is relatively straightforward and can be validated using standard geostatistical techniques, the addition of geological uncertainty to evaluate total risk remains problematic. Some of the problems associated with geological uncertainty methods include the clustering of data in favourable geologic units, difficulty in training image definition and the inability to address change of support issues for categorical variables. Despite these obstacles, the importance of geological uncertainty as a contributor to total uncertainty has prompted Newmont to explore and evaluate the use of various techniques (and combinations of techniques) on different deposit types.Two orogenic deposits of different geological complexity were selected for the study: Subika, a shear zone-hosted deposit, and Merian, a deposit containing gold mineralisation associated with quartz vein zones and stockwork within which are found higher-grade quartz breccia zones. Newmont trialled various categorical simulation approaches to determine the applicability of these methods for each deposit type and the effect of parameter choice on the width of the uncertainty interval. Some of the techniques that were trialled include multiple point statistics methods, sequential indicator simulation using local probabilities as well as variations of these methodologies.The goals of this study included: gaining an understanding of which techniques may work best in which deposit types gaining an understanding of the intricacies of each method gaining an understanding of the effect that each method has on total uncertainty analysis.This paper presents a comparison of the various techniques and makes recommendations for their use in uncertainty analysis.CITATION:Jewbali, A, Perry, R, Allen, L and Inglis, R, 2014. Applicability of categorical simulation methods for assessment of mine plan risk, in Proceedings Orebody Modelling and Strategic Mine Planning Symposium 2014, pp 85–98 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Nov 24, 2014

By H Tran

Local communities are undertaking an increased role in mine project decision making processes, associated with growing pressure and expectations from regulators, financiers and the general public. This is particularly evident in international projects within developing economies. Environmental and social issues are often complex. Solutions demand difficult choices and trade-offs between sustainable development dimensions: economic growth, social equity and environmental integrity. Proactive stakeholder engagement can play a critical role in assisting decision-makers in determining the operational reality of sustainable development by jointly exploring project trade-offs between proponents and affected stakeholders. Good stakeholder engagement has other potential benefits, ranging from reduced financial risk due to regulator delays, legal disputes or negative publicity to increasing market share through good public image. Approaches to consultation and disclosure have changed from short-term regulatory based focuses, to longer-term, strategic tools for relationship building, proactive risk management and new business identification. Approaches to consultation form a significant opportunity to contribute to overall social sustainability. This paper discusses, based on authorsÆ experience, the broader concept of stakeholder engagement and its contribution to social sustainability of the mining industry. The focus is on key considerations for an effective stakeholder engagement. Three case studies outline how broad based, proactive stakeholder engagement can contribute to improved operation and overall sustainability. The case studies include: a greenfields project in Ghana; a long-term mine in Australia; and an open-pit mine in Vietnam.

Jan 1, 2009

By T Peters

The Kibali Gold Mine is currently comprised of several open pits, a 3.5 Mtpa underground mine and a 7.5 Mtpa processing plant. Development of the underground operation commenced in December 2012, with initial access established through twin surface declines, followed by the commencement of a blind sink 8 m diameter rock hoist shaft in March 2013. Stope production started in December 2014 with ore and waste trucked to surface. The 755 m deep blind shaft sink was completed in August 2015 together with the cutting and equipping of three main station levels. Two of these levels provide access for the establishment of the underground materials handling system as well as the main dewatering system for the mine. This paper covers the process of determining the optimal location of the Kibali hoisting shaft relative to project-specific critical factors, and then focuses on the design and implementation journey associated with the off-shaft development that essentially encompasses the Material Handling System (MHS) for the mine. The journey starts from the findings of the previous owners Feasibility Study (FS), a subsequent Optimised FS, followed by detailed engineering through to implementation. It was identified during implementation that a significant change in the designed off-shaft layout was required following detailed underground geotechnical and hydrogeological investigations. In addition, the paper provides details on the MHS performance since commissioning to steady state, and on key learnings relating to the overall project process.

Mar 29, 2023

By S Liu, N M. Rana, A Take, N Ghahramani, D Clohan, S McDougall, S G. Evans, H J. Chen

Tailings dam breaches have caused significant life loss, social, economic and environmental damage in recent years. The term "tailings-flow" refers to various forms of tailings outflow movement resulting from the breach of a tailings dam. These flows, comprising a mixture of tailings, water and dam materials, can take different forms, ranging from a debris flood to a flowslide, and can travel long distances and impact large areas. The inundation extents depend on the failure mechanism, tailings dam height, total released volume, sediment concentration (associated with the rheological behaviour of the flow) and downstream conditions (including topography, land cover and presence of a water body). Numerical runout modelling of tailings dam breaches is important for predicting the dynamics and extent of tailings-flows, which are crucial steps in tailings dam consequence analysis and risk management. This paper presents a comparison of numerical simulations of the 1994 Merriespruit tailings dam breach using three numerical models: DAN3D, FLO-2D and MADflow3D. Using compiled site condition information and data from the literature and public domain, model performance was evaluated primarily based on comparisons between the observed and simulated inundation extents. The main purpose of this preliminary model benchmarking exercise was to help us evaluate the capabilities and limitations of each model, and to identify opportunities for future model improvements as part of a broader research initiative known as CanBreach. This exercise also highlights the inherent complexity of tailings-flows and the importance of using judgement to interpret model input and results.

Jul 1, 2021

By D Corley, J Moore, M Grant, A, W R

Resource estimates are the corner stone of technical and investment decision-making. Prior to mining, resource estimation uncertainty has the greatest potential to lead to poor investment decisions, despite a significant component of resource estimation uncertainty being unknowable at this critical stage in the mining cycle. This presents a conundrum to the resource geologist in terms of risk evaluation and resource classification. Ahead of mining, there is normally considerable focus on drill hole spacing analysis to determine the ‘optimal’ drill hole spacing, taking grade and geological continuity into account; cost-benefit analyses balance improved resource definition against cost; the law of diminishing returns and the exponential cost increases acting together as spacing is reduced. Typically, a lower limit to the drill hole spacing is identified. After completing the resource drilling to an agreed spacing, resource estimation is then undertaken. At this point it is common to attempt to bracket the resource estimation uncertainty. In many cases conditional simulation is used, based on a modelled, but largely assumed, variogram model. It is also assumed that the histogram of the available drill hole sample data is representative of the in-ground mineralisation. The purpose of this paper is not to diminish the importance of drill hole spacing and simulation studies, but rather to illuminate an important aspect of estimation uncertainty that, although previously recognised, is typically overlooked – the question of how representative the available data set is in characterising the true (but unknown) distribution of mineralisation. To do this, we lift the lid on one of OceanaGold’s former operations, the mined-out Globe Progress Mine, by resurrecting a high quality, close-spaced, reverse circulation (RC) grade control data set. The Globe Progress Mine is within the West Coast Region of New Zealand, it was closed and transitioned to rehabilitation in 2016 and is now known as the Reefton Restoration Project. The exhaustive Globe Progress grade control data was used to repeatedly ‘redrill’ the deposit by extracting 35 m × 35 m spaced subsets from the original 5 m × 5 m spaced grade control data. Utilising closely spaced grade control data removed the need for assumptions regarding short range continuity, which are necessary with forward-looking analyses that are based upon broader spaced resource drilling. The extraction process used a nearest neighbourhood algorithm, repeatedly moving the origin in 5 mE, or 5 mN increments. Individual resource estimates were then completed for each of the extracted drill hole data sets (49 in total) as well as a grade control estimate based upon the exhaustive data set. Whilst the data unpinning each of the 49 estimates changed, the geological assumptions, variography, and modelling parameters remained constant. This approach was taken to isolate the impact of changing the input data. The 49 estimates were then compared against each other and the grade control estimate. The mean of all 49 sensitivity estimates was close to that of the grade control estimate in terms of contained gold, tonnes and grade. Whilst it is acknowledged that the grade control estimate itself is subject to some degree of estimation uncertainty, the close match between the average of the 49 estimates and the grade control estimate suggests that the resource estimation methodology is reasonable and appropriate. Whilst this comparison is important, the focus of this study is on the component of estimation uncertainty related to the underlying data, and this is reflected in the spread across the estimates. The spread across the 49 global estimates (highest to lowest) for this particular Mineral Resource Estimation Conference 2023 | Perth, Australia | 24–25 May 2023 142 case study was found to be significant (approximately 20 per cent in grade and metal) and that is attributable solely to the underlying data. This exercise quantifies a component of the estimation uncertainty that is inherent to all drill hole data and is distinct from the uncertainties associated with modelling methodology choices, sample and subsample quality and drill hole spacing-related interpolation uncertainty. Importantly, this uncertainty is unknowable prior to mining; we can only directly compare the resource drill hole data against grade control data after mining has taken place. For the case study, approximately 65 per cent of the estimates fell within 5 per cent of the grade control estimate for contained-gold, suggesting that for many projects the histogram of drill hole data is unlikely to differ noticeably from that of the in-ground resource. However, about 15 per cent of the estimates in this study differed by more than 7.5 per cent, suggesting that a not-insignificant proportion of estimates will be materially compromised. Whether or not the available drill hole data is representative comes down to the ‘luck of the draw’ and cannot be known at the time of resource estimation. Given the challenge of attempting to evaluate forward-looking estimation uncertainty, a component of which that can only be quantified retrospectively, what should we do as resource geologists? What are the implications for risk evaluation, resource classification and reconciliation? Furthermore, without rigorous post-mining data checks, resource geologists may conflate suboptimal modelling with the shortcomings of the underlying data. An example of this problem is discussed in the following section.

May 24, 2023

By Crawford M

During the initial development of Mount Isa Mines power was supplied from a temporary power plant situated near the Man & Supply Shaft. The main power plant was placed in service early in 1931 and then comprised two Babcock and Willcox boilers, fired by pulverised fuel, and two British General Electric Company's turbo-alternators of 5,000 kW. each. Both plants have been described by A. F. McAskill in the Journal of the Institution of Engineers, Australia.From 1931 power demand progressively increased due to greater production, further mine development in the harder sulphides increased pumping for mine drainage and additions to mill and smelter until, by 1935, the plant was inadequate for further output commensurate with a reasonable safety margin.Coincident with the added power demand, operating conditions involved a fuel problem which could not have been anticipated. The ash content of the fuel supplied gradually increased from 13% to 16-5%, while the melting point of the ash decreased with higher pyrite content.Temperature conditions in the furnace required careful control to cope with ash formation and slag accretions.Consequently brickwork, excessively stressed on water walls, was constantly under repair, and required suspension periods of 50% of operating time for cleaning and overhaul.Load conditions varied continually, therefore the high heat liberations in the furnace, necessary to accommodate peaks in fluctuating output, resulted in ash fusion.

Jan 1, 1939

By P Cesare, S Munro, D Wandel, R A. Bearman

Consideration of the processing plant operational envelope is a key factor in production scheduling,and therefore mine planning, for any mining operation. In many cases hard-wired or regressionbased tonnage-grade-recovery relationships are used as mine planning constraints and as a means of valuing the system output. In extensions of this type of approach, various regressions can be used to describe throughput limits, based on a number of global metallurgical parameters.The ultimate position for the optimisation of a mine plan and production schedule is to have a full process plant model running as an integrated part of the mine planning exercise. A plant model suitable for this needs to have all the required sensitivities to input parameters such asfragmentation, grade, mineralogy, strength and hardness. The model then needs to convert these to performance measures for the plant, which include recovery, throughput, product size distributions, energy consumption, water use and operating cost.In this paper an approach is outlined that takes this view and then goes beyond it to provide a full, time-based bottleneck identifi cation and valuation tool.Using such an approach it becomes possible to run mine plans and production schedules in windows of days, weeks, months and over the life-of-mine with a time-enabled process model acting as the active constraint. In this way virtual bottlenecks can be identifi ed for various mine plans and schedules well ahead of time. The value of de-bottlenecking can be defi ned, not just at a plant scale, but in terms of the overall mining operation, and the data can be used as the basis for capital investment decisions.CITATION:Bearman, R A, Cesare, P, Munro, S and Wandel, D, 2014. Incorporation of a full process plant model as an active constraint for mine planning and production scheduling, in Proceedings Orebody Modelling and Strategic Mine Planning Symposium 2014 , pp 121–128 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 24, 2014

By S S. Kanchibotla, E J. Sellers, L Julian, A Musunuri

Fume events in coalmines are typically associated with wet conditions, soft ground and deep holes. An ACARP research project used laboratory and field testing combined with literature reviews, numerical models and field investigations to characterise the influence of these conditions on the propensity for fume. This paper highlights the results for soft ground and wet conditions and proposes a proactive fume mitigation methodology. A simple numerical model is used to show how fume arises in soft rock that yields more under the loading of high-pressure, water-resistant explosive blends than for ANFO. The blends cool more rapidly after detonation into the lower temperature zone favourable for NO2 production. Low-pressure, high detonation temperature explosives are loaded or charged into soft ground. Water resistance must be considered because soft, faulted and fractured ground can lead to fume from degradation by water flow and non-ideal detonation of product in cracks.A suite of tests were developed to quantify ANFO and emulsion blend performance over time that can be carried out in a mobile laboratory on-site. Index tests such as viscosity measurement and water resistance in beakers are proposed to quantify long-term product performance because small components, such as surfactant, prill impurities and prill fines, contribute to inconsistent product performance. Water ingress experiments and detonation tests aligned with field investigations identified and characterised the role of groundwater in damaging ANFO and causing fume.Fume risk management is achieved using a proposed proactive fume mitigation methodology to characterise influences such as seasonal rain variation, groundwater flow hydrogeology, rock mass strength and structure well ahead of blast design. The design of blasts and selection of explosive products to consider expected conditions will reduce fume, improve efficiency in the mine and offer cost advantages.CITATION:Julian, L, Musunuri, A, Sellers, E J and Kanchibotla, S S, 2015. Mitigation of post-blast fume in soft ground and wet conditions, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 511–518 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By R Wynn, T J. Akroyd, C Costa

In an environment of lower zinc prices, falling revenues and reducing zinc feed grades, Century mine implemented a fast-tracked capital upgrade program in less than 15 months. The program was designed to increase ore milling throughput capacity by 20 per cent and optimise the capacity of the flotation plant to increase zinc recovery by approximately 2.5 per cent whilst maintaining final zinc concentrate grade.A key aspect of this program was minimising capital expenditure by better utilising existing capacity and only adding capacity where absolutely required to address critical processing bottlenecks. By gaining an understanding of plant process bottlenecks and future ore blends, and by carefully selecting appropriate technologies for particular specific flotation applications, maximum return on minimal capital investment was achieved.The close collaborative work achieved between the metallurgy processing department and other operational departments on-site was also critical to the success of this project. This work increased the mining and processing capacity of the mine and port site respectively, such that the full value of the process plant modification could be achieved.Capital payback on this investment was achieved in approximately three and a half months.This case study demonstrates the extra value to a mining business that can be achieved through fully understanding the mining/processing value chain and by careful targeted action to address critical bottlenecks in the processing chain from the mine through to the port site.CITATION:Akroyd, T J, Wynn, R and Costa, C, 2014. MMG Century Mine, a case study – maximising project net present value through targeted capital expenditure and process optimisation against a backdrop of falling metal prices and feed grades, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 417–426 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014