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By G Pattenden, R Hargreaves, P Pettit

"Even with the cyclic nature of mining, when it comes down to it, the bottom line is that whatever direction the commodity market is going there is always a desire to improve the economics of an operation in order to deliver a greater return to investors. Adapting to market pressures by introduction of an operational process change can often have a downstream impact. What may be less obvious is that reconciliation can play an important part in measuring the effectiveness of many operational changes. Through the adoption of best practice reconciliation and related comparisons, it is possible to measure the impact of changes across the mine value chain and identify variability that may have been introduced. Using analytical business improvement tools, examining and monitoring planned changes can be crucial in understanding whether the introduced changes have been effective and whether they have provided the expected result. Using several case studies, the authors will highlight the benefits provided by modern business intelligence tools, which can provide data validation and accurately report data trends related to both planned and unplanned change events.Citation:Hargreaves, R, Pattenden, G and Pettit, P, 2016. Measuring the Effectiveness of Change through Best Practice Reconciliation, in Proceedings Ninth AusIMM Open Pit Operators' Conference 2016, pp 71–83 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Nov 15, 2016

By R Winterberg

Concrete is a well established and reliable construction material for the permanent lining of tunnels, but shows some weak performance characteristics, which can be overcome by the addition of specialised fibre reinforcement. This paper addresses the particular performance design requirements of segmental linings, discussing the improvements of fi bres on concrete properties. Focus is made on the beneficial effects of fibre reinforcement on the cracking behaviour and the toughness performance, providing a safe and durable tunnel lining.Not only the mechanical performance of fibre reinforced concrete (FRC) for segmental linings, but also the durability of the linings has gained growing attention among the designers and consultants. Especially tunnel linings with exposure to media with corrosion potential, such as wastewater sewer tunnels or desalination plant outfall tunnels, have high requirements on their durability. The design of these structures must provide a comprehensive study of durability aspects. Fibre reinforcement can substantially improve the durability of concrete.Research has been carried out on the cracking behaviour of concrete. The beneficial effects of steel fibres on the cracking behaviour reduce the permeability by reducing the flow paths within the concrete. Crack bridging steel fibres create necking effects in bending cracks, leading to earlier closure of the cracks. Further, steel fibres create particular crack formations, which lead to a substantial reduction of the fl ow rates through separation cracks. The results also show that considerable cost savings can be achieved using FRC, as the thickness of the linings can be reduced.The durability design issues will be addressed and underlined by a case history on the Hobson Bay sewer tunnel in Auckland, New Zealand.

Mar 8, 2011

By M Johnson, M Horrigan

The scope of this report is to examine the aforementioned hypothesis by performing a detailed analytical comparison of a P&H electric rope shovel to an O&K diesel powered hydraulic excavator. In order to complement the integrity of the concluding results, two different size categories will be analysed in order to demonstrate that the findings can be extrapolated and applied to all the machinesÆ size classes. These two size classes are categorised by their bucket sizes and they are in the range of 43 - 58 cubic metres and 23 - 26 cubic metres. It should be noted that electric powered hydraulic excavators will not be considered in this report. In order to compare the electric and hydraulic types, the machine variants that will be analysed are commercial cost-effectiveness and operational flexibility. Although operational flexibility can be an ambiguous characteristic, a clear and thorough definition describing its exact meaning has been included. In order to simplify this study, all the data collected for this comparison have been for overburden removal, eliminating the variation that occurs with the movements of the shovel when selectively mining in the ore deposit. Thus, it ensures that all the data that is compared stems from a common origin for all the shovels. In other words the information will be compared when digging in the same material, loading into the same sized haul trucks, and when possible, with the same operators. Theoretical data received form the respective manufacturers, and actual data obtained from Mount Whaleback, was used for this comparison. This leads to the final comparison, where the operational flexibility and the cost-effectiveness are evaluated, with respect to their individual importance, ultimately influencing the final recommendation.

Jan 1, 2002

By E Asakpo, S Chaffer, A Heath

Newmont has had continuous production at their Ahafo operations, Ghana, since 2006. In 2013, Ahafo initiated an efficiency programme to improve mill performance and reduce energy consumption. Following this assessment, a Turbo Pulp Lifter (TPLTM) was installed in the Ahafo SAG mill in April 2015 to replace the existing radial pulp lifters. Plant operational data showed delivery of a power saving of 10 per cent, an improvement in throughput of 3.3 per cent, with no loss of grind size. Pulp lifter life was also doubled from 11 to 22 months.However, during subsequent relines when the grates were removed it was found that one in four of the outer pulp lifters were wearing at a faster rate than the remainder. This was investigated by Discrete Element Method (DEM) modelling, which predicted some overtopping and internal recycle within the pulp lifter. Significantly, the model predicted that the recycled material would pass back down every fourth outer pulp lifter, matching the field observations. Subsequently, the DEM investigation was continued and became an R&D project to improve the TPL design. The results are summarised here, leading to the development of the next generation Spiral TPLTM.CITATION:Heath, A, Chaffer, S and Asakpo, E, 2018. The development of optimised pulp lifter design for the Ahafo SAG mill using discrete element method modelling, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 585–594 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

By Bell I. F

In 1985, ZC Mines (now Pasminco South) had been unprofitable for some years due to a combination of high operating costs, low metal prices, low head grade and an aging and inadequate mining infrastructure. However, the resource of metal in the ground was still of world class, even after some 80 years of mining. A major study, which was to be of two years duration, was therefore commenced to establish a practical and profitable long term mining strategy and to cost the infrastructure options needed for its support and thus form the justification for a capital expenditure program to take the mine profitably into the 21st century and its second century of operation. This paper discusses the rationale behind the methodology adopted and the nature of the results achieved in one aspect of the study - the determination of the mineable resource and the relationship between the head grade/quantity of the economically mineable resource and the variables of cut-off grade, cost structure, annual production rate and metal prices/exchange rates. The basis of the study was the designing of some 5000 scopes to mine out the entire resource for a range of cut- off grades and the assembly of the detailed physical data thus obtained in a stope-by-stope data base for financial and other analysis. Those scopes which were shown to be economically mineable were then scheduled for two optimum annual production/cut-off grade/metal price combinations to provide life-of-mine cost and value of production cash flows.

Jan 1, 1992

By D Xu

BHP Billiton Iron Ore is one of the world’s premier suppliers of iron ore. It currently has operations in Western Australia and Brazil and also has some iron ore interests in West Africa.BHP Billiton’s Optimisation R&D team has developed a proprietary mine planning optimisation tool that uses a mixed integer linear programming (MILP). This tool is called Blasor and it is used to rapidly evaluate the resource development potential (RDP) scenarios for the company’s business development strategy. In addition it generates life of asset (LOA) mine plans for the company’s operations and growth projects. The Blasor optimiser maximises the discounted operating cash fl ow (DCF) as the objective function, subject to mining, processing and transportation capacity constraints and blended product quality constraints. The paper will outline how Blasor has been applied to the resource development potential (RDP) strategy scenario studies, growth project evaluations and LOA mine planning within BHP Billiton Iron Ore.The practical application of Blasor to resource planning optimisation within BHP Billiton Iron Ore has demonstrated the value of such a tool for optimising strategic directions through the evaluation of a number of carefully proposed scenarios and maximisation of operational decisions, such as cut-off grade, open pit development sequence, etc. Particularly for the company’s business development direction studies, Blasor plays the role of a fair valuation tool in that it discovers the most valuable resource development scenario, thus establishing a sound basis for comparing the economic merits of each scenario.

Jul 11, 2011

By R Klepper

Separation of leach residue suspended solids from pregnant liquor solution is an important step in hydrometallurgy flowsheets. Alternative flowsheet options are counter-current decantation (CCD) thickeners or counter current washing (CCW) horizontal belt vacuum filters. Extensive sedimentation and vacuum filtration simulations have been completed by FLSmidth on leach discharge slurries to indentify equipment capacity and performance. These data were used to compare Capex and Opex for CCD versus CCW alternatives. In addition, Capex and Opex for large horizontal belt vacuum filters with filtration areas greater than 250m2 are compared to current state of the art sizes of 150m2. This paper presents this information and discusses various advantages and disadvantages.

Aug 8, 2011

By H Arvidson, A Walker, N Pollock

Following the recent tailings tragedy in Brumadinho, the Investor Mining and Tailings Safety Initiative was formed representing institutional investors in the mining industry. This Initiative, led by The Church of England (CoE), requested data from 726 mining companies on each of their Tailings Storage Facilities (TSFs). What this exercise confirmed was that there was no public database of TSFs, and that there was a clear gap in tailings management systems within the disclosing companies. We present an approach using technology to support best practice TSF management, governance and disclosure which was originally submitted as part of University of Cambridge Post-graduate studies in Sustainability Leadership in January 2020. The aim of the paper is to discuss how technology could be used to deliver a Tailings Management Solution (TMS) that is aligned with the Global Industry Standard on Tailings Management (GISTM), and supports rigorous governance leading to disclosure. Subsequently the goals of the plan are aligned with that of the co-conveners of the GISTM (the International Council on Mining and Metals (ICMM), Principles for Responsible Investment (PRI) and United Nations Environment Program (UNEP)) which is to facilitate operators’ trajectory towards zero harm to people and the environment. Most of the focus to date around tailings management post Brumadinho has been on monitoring technologies, of which there are many. It is obviously important to acknowledge the critical role of monitoring technologies; however, our approach is agnostic to monitoring technologies and assumes that all of them are relevant. Our focus is on the data management, reporting and governance leading to disclosure of the information. Critical components of developing the TMS include adapting existing software products and solutions, recognising a system thinking approach is needed, strategic partnerships to deliver an accessible solution faster and more cost effectively, and, new ways of collaborating. The TMS should also accommodate relevant regional geotechnical codes and standards. The industry need for a TMS is well established and urgent, with significant pressure from regulators and civil society for the industry to address this significant issue.

Jul 1, 2021

By J MacNeil, R Dimitrakopoulos

As open pit mining of a deposit deepens, the cost of extraction may increase up to a threshold where transitioning to mining through underground methods is more profitable. This paper provides an approach to identifying an optimal depth at which a mine should transition from open pit to underground mining. The value of a set of candidate transition depths is investigated by optimising the production schedules for each depth’s unique open pit and underground operations. By considering the sum of the open pit and underground mining portions’ value along with the cost of transitioning corresponding to each candidate transition depth, the optimal transition depth can be identified. The optimisation model presented is based on a stochastic integer program that integrates geological uncertainty. As an input, the stochastic integer program utilises a set of several stochastic simulations that represent equally probable scenarios of the mineral resource. This group of simulations describes the uncertainty in the deposit, while the optimiser aims to maximise value based on discounted profits of both the open pit and underground components of the deposit.CITATION:MacNeil, J and Dimitrakopoulos, R, 2014. A stochastic optimisation formulation for the transition from open pit to underground mining within the context of a mining complex, in Proceedings Orebody Modelling and Strategic Mine Planning Symposium 2014, pp 363–368 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 24, 2014

By K Katov, S T. Ciutina, J D. Pyke

The development and optimisation of mill discharge trommels, and specifically their screen panels, can be a neglected area in the complex operation of a minerals processing plant. Trommels are often seen as a ‘set and forget’ component of the circuit, even when significant improvements in design are possible. A redesigned trommel and panel arrangement has simplified and added flexibility to the plant shutdown schedule at Kirkland Lake Gold’s Fosterville Gold Mine in Central Victoria.Prior to the trommel redesign, the shutdown frequency was determined by the expected life of trommel panels at 14 weeks. Planning downtime around this item led to higher maintenance costs and wastage in other areas of the plant. This was particularly disruptive with respect to mill lining change-outs, which were forced out of sequence and often changed prematurely. Fosterville Gold engaged Metso Australia Limited to propose a new trommel design that would better suit the site. The new trommel was engineered to balance simplicity with performance, and incorporated the latest in Modular trommel design, modelling and Finite Elemental Analysis (FEA). Modular Panels and Spiral Segments achieve significantly longer life, and allow in-situ panel change outs, flexibility in spiral and dam positioning and an improvement in classification performance. Trommel panel life has significantly increased from 14 to 71 weeks in the trommel’s highest wearing zone. The new design has eliminated some risks to safety by reducing manual labour and lifting requirements during shutdowns. There is greater flexibility with respect to shutdown requirements. The site is no longer at the mercy of trommel panel lifespan, which allows for better optimisation of wear components in the circuit. CITATION:Pyke, J D, Katov, K and Ciutina, S T, 2018. Modular SAG mill discharge trommel for maintenance flexibility and performance, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 613–620 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

By F Grobler

Many projects fail because project performance in unfavourable economic conditions was not anticipated at the investment decision stage. This type of failure may have been avoided through the selection of a strategy that enables the project to perform well under a range of possible future economic conditions (a ærobustÆ strategy); rather than an æoptimalÆ strategy for expected future conditions that will never eventuate. This paper describes a method of rapidly generating mine plans for a number of project strategies, and then evaluating it against a representative range of equally likely economic conditions. The key performance indicators derived for each strategy are the mean value and the distribution of values (variance). A prudent investor will identify prospective strategies not only on the merit of highest mean values (as a proxy for economic reward), but also on the probability of not meeting specified investment hurdles (a proxy for risk). A robust strategy will achieve its financial objective even under adverse economic variations. This paper focuses on the effect of commodity price uncertainty; particularly around the choice of mining and processing capacity levels. Results from enumerating 2000 prices scenarios against 63 strategy combinations show how processing and mining capacity can be manipulated to manage the risk-reward trade-off.

Sep 26, 2011

Sampling protocols and metallurgical flow sheets should be designed to suit the style of mineralisation in question. In support, the a priori need for evaluation programs is the characterisation of the mineralisation type(s) and domain definition. The proportion and size of gold particles has a direct impact on the effectiveness of sampling protocols and metallurgical processes employed. Within the coarse- to-fi ne gold spectrum, the samplability of a deposit ranges from relatively simple for fine-grained disseminated particles, through to difficult for coarse gold mineralisation. Conversely, metallurgical processing may be relatively simple for coarse gold ore and more difficult for very fi ne gold ores. Most deposits contain a proportion of both particle size types. The nature of mineralisation, mineralogy and associated gold particle sizing can only be determined by preliminary sampling to facilitate testing. Mineralogical studies, focussing on ore mineralogy and gold particle deportment, size and distribution are required as part of wider paragenetic and geometallurgical investigations. This paper discusses key issues and presents a methodology for the determination of gold particle size in coarse gravity-gold ores to support sampling optimisation and which also contributes to metallurgical characterisation.

Aug 1, 2010

By D Hillier, A Giblett, K Parker, V Ramsell

Kalgoorlie Consolidation Gold Mines (KCGM) operates the Kalgoorlie Super Pit open cut, Mt Charlotte underground mine, Fimiston process plant and Gidji Roaster facility for joint venture partners Newmont Mining Corporation and Barrick Gold. In 2004, the Fimiston plant was upgraded by the addition of gravity concentration to the Fimiston and Mt Charlotte grinding circuits, including the installation of a central intensive cyanidation reactor to process the gravity concentrates. The gravity project was justified after detailed analysis demonstrating an expected increase in overall gold recovery of approximately one per cent, in addition to reduced elution costs and reduced gold inventory in flotation concentrate stockpiles. The gravity circuits were commissioned in August 2004, and have since consistently recovered 10 to 20 per cent of the gold present in the KCGM ore, delivering a reduction in coarse gold losses equivalent to 0.45 per cent additional metal recovery and contributing to improved metal accountability.CITATION:Giblett, A, Hillier, D, Parker, K and Ramsell, V, 2012. The impact of gravity gold recovery at Kalgoorlie Consolidated Gold Mines, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 199-206 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

By S Juras

The terms measured resources and proven reserves denote the highest level of estimation confidence in all of the major classification schemes. But what do they really bring to today’s project or mine with respect to production planning and expectations? Initial reserve declaration does not need measured resources, just indicated resources. Economic viability of a project is assessed on total reserves with nary a bonus for the amount of proven reserves. Production plans are based on grade and tonnage goals that may only coincidently correspond to proven reserves. So are the measured and proven categories still relevant? Historically, and almost exclusively in underground mines, companies only allowed mining in areas of proven reserves. Some companies still follow that philosophy. But many others will mine a mixture of probable and proven reserves without hesitation. Also what of the undeveloped project in a new district – what is to be made of their declared measured resources and proven reserves? Measured resources are commonly set either by some type of proximity to data scheme or a matter of ‘feel’ based on the qualified person’s experience. The parameters for reserve conversion focus on the project as a whole and then a portion becomes classified as proven reserves almost solely based on whether the resource category is measured. So should the mining industry continue to use these categories of resource and reserve classification? This paper will present arguments about making these categories once again more relevant. A more disciplined usage of these categories may re-introduce their relevancy in public disclosures of resources and reserves. As well a more consistent usage in operations may lead to increased confidence in managing production targets and costs.

Aug 22, 2011

By A Clarkson

Cannington Mine is an underground silver lead zinc operation located in north-west Queensland which has been in production since 1997. Ore is primarily moved through an underground material handling system comprised of a crusher, conveyor and hoisting shaft. The Fowler Shaft was constructed in 1997 using a strip and line method with the intent for it to provide a means to hoist ore from the loading station 600 m below surface. The shaft also serves as the route of key services including high voltage power, mine dewatering and fresh air. Despite the adherence to a mining exclusion zone, large-scale change in geotechnical conditions around the shaft were first observed in 2015. Ongoing ground movement around the shaft lead to cracking and delamination of the concrete liner. Shaft management required the on-site team to measure deformation rates and magnitudes, forecast change, manage rockfall risk and deforming pipework, and ultimately, hoisting skip clearance. Monitoring techniques to observe and measure deformation were required to evolve with the magnitude of movement. Some techniques leveraged off modern technology while some of the most useful techniques were based on logic and first principles. All shaft deformation management strategies relied on the co-operation and alignment between Cannington’s Infrastructure Maintenance, Survey and Geotechnical Departments.

Mar 29, 2023

By S D. Fox, P B. Swart

Statistics showing that mine rehabilitation is falling behind rates of disturbance continue to be reported in the media. Unfortunately, most reported statistics do not account for the large growth-cycle that mining in Australia experiences, where there are typically significant new disturbances with large portions of these areas not being available for rehabilitation for a number of years. Many commentators assert that better planning is required to ensure that rehabilitation will be able to achieve a safe, stable, non-polluting landform that meets the agreed post-mining landuse.This paper focusses on the revegetation aspects of mine rehabilitation and in particular the matters that need to be addressed in the planning stage so that revegetation success is ultimately able to be demonstrated to regulators and other stakeholders.CITATION:Fox, S D and Swart, P B, 2018. Planning revegetation for relinquishment, in Proceedings Life-of-Mine 2018, pp 113–115 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 25, 2018

By D J Maconochie

The use of rock bolts as permanent support has been prohibited by client specifications in several recent large tunnel projects in Australia. The justification for this appears to lie in concerns with proper and verifiable installation procedures rather than concerns with the intrinsic durability of the corrosion protection systems. However, in civil tunnels, preventing the use of permanent rock bolts for long-term support results in the use of cast in place concrete lining which in some instances would otherwise be unnecessary.

Mar 8, 2011

By J Coombes

The JORC Code lists the three core principles of Transparency, Materiality and Competency as fundamental to how mineral estimates are publicly reported. But where the principles of Transparency and Materiality can be considered conscious choices underlying decisions at the point of disclosure, Competency is a self-declared position statement based on one’s confidence to defend a technical position (as well as the functional pre-requisites of institute membership and a minimum of five years relevant experience).Developing competency in the mining industry is an ad hoc process, generally left to the individual to chart through a process of osmosis from personal work experiences that lead to a sufficient level of confidence. Companies that actually present professional development programs leading to reporting competency are rare. And even once a person has followed a program, there is no specific outline of what constitutes technical competence.No doubt, there are persons signing off on mineral statements who would benefit from developing and/or updating their technical skills (they may not even be aware of unmastered skills). Equally, there are technical practitioners who are sufficiently competent, but lack the confidence to step up and publicly report their estimates. Confidence in one’s own abilities plays a significant role in deciding when one is ready for the responsibility of submitting mineral estimates for public consumption. In addition, a person’s organisational support, such as the availability of suitable peers and professional development programs, and opportunities to learn from a variety of technical projects contribute to developing relevant experience. Increased exposure in both technical breadth and depth enhance confidence in one’s ability and competence.The mining industry provides numerous opportunities through direct and indirect means to develop the competency underpinning a stable reporting code. This paper examines a theoretical framework and associated processes that could be used to examine how the mining industry, companies and individuals collaborate to develop this vague principle of competency. This paper seeks to initiate research with the express purpose of enabling more effective and efficient development of reporting competency in our industry.

Aug 22, 2011

By R G. Jeffrey

The Northparkes, Endeavour 26 orebody is a porphyry copperûgold deposit and comprises a moderately to well jointed rock mass characterised by gypsum veining, the intensity of which decreases with depth. The top 480 metres of the orebody is currently being mined by block caving, the undercut dimensions measuring 196 metres in length by 180 metres in width. Continuous caving was never achieved after the completion of the undercut thus cave inducement techniques were sought to maintain caving so as to safely sustain production. The use of hydraulic fracturing as a cave inducement tool was successfully trialled in December 1997 using existing exploration boreholes located midway up the current lift. Subsequent fracturing campaigns have enjoyed various degrees of success and have yielded in excess of seven million tonnes of ore at a significantly lower cost than conventional cave inducement techniques. Monitoring of both the hydraulic fracture system and the rock mass response has provided considerable insight into the geometry, growth and influence of hydraulic fracture networks above the Northparkes block cave, and has initiated additional research into the use of hydraulic fracturing in other mining methods.

Jan 1, 2000

By A K. Ghosh, J Chung, E Topal, M Asad

"Many open pit (OP) mines with considerable vertical extent are approaching the end of their life-of-mine; some of them are seeking the opportunity to make the transition from OP to underground (UG) mining. The decision on the best location for transition from OP to UG mining should be addressed at the strategic mine planning stage. Conservatively, the transition to UG mining is considered near or after the exhaustion of the reserve within the ultimate pit.However, if UG is evident and exclusively viable from the inception, defining the best location for the transition through a conservative approach may not be an optimal option to explore. This clearly establishes the need for a mathematical model that aims to maximise the project value and considers OP and UG mining with crown pillar (CP) requirement simultaneously. Underground mine layout varies from one UG mining method to the other, and consequently the variation in the location of transition is eminent. Thus, focus on the selection of UG mining method must be a part of this analysisThis paper presents an implementation of an integer programming (IP) based mathematical model that evaluates the changes in mining layout and the project value under possible variation in the transition point from OP to UG mining for stoping and block caving methods. An IP problem is a mathematical optimisation or feasibility method in which some or all of the variables are restricted to be integers. The outcome of the implementation reflects that mining strategies with OP transition to stoping and block caving methods generated higher values than OP-only mining strategy. The case study not only demonstrates the difference in mining layout for both stoping method and block caving method, but also reflects that a joint consideration of OP mining, UG mining and CP placement helps to achieve maximum project value and resource utilisation.Citation:Darbritz, J, 2016. Remediation of Wall Failure at Kalgoorlie Consolidated Gold Mines' Golden Pike Cut-back 2016, in Proceedings Ninth AusIMM Open Pit Operators' Conference 2016, pp 96–103 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Nov 15, 2016