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By W L. Daniels, C Stilson, C Zimmerman

Mineral sands mining for ilmenite, rutile and zircon has disturbed over 1000 ha of prime farmland in Virginia (USA) since 1997 and additional areas are likely to be disturbed in Virginia and North Carolina (USA) over the next 15 years. Full-scale mining operations at the Old Hickory Project in Virginia were initiated in 1997 by Iluka Resources Inc. and restoration protocols have continued to evolve in response to a variety of economic, technical and social issues. Early on, the return of these lands to agricultural row-crop production was complicated by vertical stratification of tails + slimes and lateral variability in soil physical conditions in the reclaimed pits and by limited topsoil return. Virginia Tech and Iluka have worked cooperatively with all stakeholders for over 20 years to review the pre-existing research base, conduct new and innovative site-specific research and thereby provide reasonable expectations of post-mining soil productivity levels. In 2004, Virginia Tech, Iluka Resources and a local leaseholder (Carraway-Winn family) agreed to jointly manage a 45 ha research demonstration farm where the long-term effects of alternative soil reconstruction practices are being rigorously monitored for both row crops (corn and wheat) and forage production. All mined land crop yields are also compared to an adjacent undisturbed exceptional quality prime farmland soil. Row crop yields between 2005 and 2010 were significantly above county average yields (regulatory target level) and approximately 75 - 80 per cent of undisturbed adjacent prime farmlands. The state regulatory authority has recently relaxed its position on the necessity of topsoil return versus use of topsoil substitutes based on appropriate on-site research results and the ability of the reclaimed soils to meet comparative local county crop yield targets. This cooperative effort allows all clientele groups to objectively assess the post-mining productivity of these mined lands while providing an invaluable educational opportunity for the mining industry. CITATION:Daniels, W L, Stilson, C and Zimmerman, C, 2012. Development of effective rehabilitation protocols for mineral sands mining in Virginia, USA, in Proceedings Life-of-Mine 2012 , pp 97-104 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 10, 2012

By T Sprague, D Pateman

"The Gosowong Gold Project is owned and operated by PT Nusa Halmahera Minerals (PT NHM), an Indonesian company 75 per cent owned by Newcrest. It is located on Halmahera Island, in the North Maluku Province of the Republic of Indonesia, approximately 2450 km north-east of the national capital, Jakarta (Newcrest, 2017).Kencana is one of two underground gold and silver mines at the Gosowong Operation where ground conditions vary from competent to very poor. Development headings occurring in poor rock mass conditions require high capacity ground support including long tendon cable bolts. Manual installation of cable bolts in these development headings has been a time consuming process due to borehole collapse, blockages requiring subsequent re-drilling and a minimum eight hour grout curing time interval. The installation of cable bolts including the setting, plating and tensioning can impact the critical path for development heading advance resulting in development cycle delays.A review was conducted by PT NHM on current industry practices for alternatives to manual cable bolting. PT NHM subsequently approached Minova to assist with the development and trialling of self drilling anchors (SDAs) installed using jumbos with a rapid setting pumpable resin, CARBOTHIXTM. A series of system development trials were conducted and a reliable bolting system was developed utilising the existing jumbo drilling fleet with minimal required modifications.The system developed was a ‘one pass’ bolting process to install and grout SDAs using a two component resin with a remote, mechanised system. Improvements achieved from the system include: eliminating hole closure issues and more immediate support in poor rock mass effectively reducing personnel exposure to poor ground conditions by removing the requirement to access the drive backs reducing grout set time with full installation times for 6 m SDAs averaging 25 min.The resin grouting system has now been successfully implemented to effectively manage areas of poor ground conditions and to accelerate advance rates in high priority headings.CITATION:Pateman, D and Sprague, T, 2017. Development and implementation of a long tendon bolting system utilising resin grouting technology, in Proceedings 13th AusIMM Underground Operators’ Conference 2017, pp 79–84 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Oct 16, 2017

By A Guillen, J-P ChilFs

Most 3D geological modelling tools were designed for the needs of the oil industry or detailed mine planning and are not suited to the variety of situations encountered in other application domains. Moreover, the usual modelling tools are not able to quantify the uncertainty of the geometric models generated. The potential field method was designed to build 3D geological models from data available in geology and mineral exploration, namely the geological map and a digital terrain model (DTM), structural data, borehole data and interpretations of the geologist. This method considers a geological interface as a particular isosurface of a scalar field defined in the 3D space, called a potential field. The interpolation of that field, based on cokriging, provides surfaces that honour all the data. The 3D model and its parts are always consistent with the observations. New developments allow the covariance of the potential field to be identified from the structural data. This makes it possible to associate sensible cokriging standard deviations to the potential field estimates and to express the uncertainty of the geometric model. It also, for the first time, gives a statistically optimal, geologically sound way of interpolating geology, other than directly joining the dots as you do with CAD. Practical implementation issues for producing 3D geological models are presented: how to handle faults, how to honour borehole ends, how to take relationships between several interfaces into account, how to model thin beds over many kilometres, how to optimise lithological properties and how to integrate gravimetric and magnetic data. We describe all geology surfaces and volumes using implicit functions. These are then rendered onto the required sections, plans, etc. The estimation of orebody grades and tonnes, using an unbiased and optimal geostatistical technique, makes use of the stratigraphically bound 3D geology model. An application to the geological modelling of the Hamersley iron ore district, Australia, is briefly presented.

Jan 1, 2009

By A Minchinton

With blasting, all far-field phenomena including, but not limited to, stress wave propagation, fracture, vibration and muck pile formation are intrinsically and irrevocably dependent upon near-field phenomena or mechanisms that we describe using physics-based mathematics typically transcribed into computer codes. The energetics involved in such near- to far-field transitions are not fundamentally relevant as they are simply progenitors of these processes.The notion of explosive energy as a descriptor for explosive or blasting performance is a case in point. These energies, which are generally used in blasting tables, are almost exclusively based on ideal detonation theory alone and do not include the influence of the rock, charge diameter, blasthole length and the late-time dynamic expansion that can be predicted using codes based on non-ideal detonation theory.With decoupled charges in presplits for example, the pressure drop between the charge and the blasthole wall can be simply described to first order using the energy relationship associated with adiabatic expansion. However, a more realistic mechanistic solution involves interacting fluids and turbulence leading to dynamic processes such as the channel effect.CITATION:Minchinton, A, 2015. On the influence of fundamental detonics on blasting practice, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 41–54 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By Kleine T. H

Blast design involves many engineering constraints and objectives. Some of the more important include the implementation costs, the desired fragmentation and shape of the muckpile. A spreadsheet has been developed to allow blast design options such as burden, spacing, blast hole diameter, decking and explosive type to be varied. As any option is varied the spreadsheet recalculates and graphs the expected implementation costs, fragmentation and muckpile shape in seconds.The spreadsheet extends the philosophy of simple robust fragmentation prediction (Cunningham, 1983) to include similar models for explosive detonation (with respect to explosive type, age, blast hole diameter and density) and muckpile shape (with respect to burden, spacing, charge location and weight). The new empirical models for explosive detonation and muckpile shape prediction have been calibrated successfully for one situation and are now undergoing further field trials.

Jan 1, 1992

By J Balzary, A Mohais

Dynamic market and operating conditions, coupled with an environment in which multiple objectives and trade-offs are common, pose major challenges for planners and schedulers working in any mining entity. Many mining companies recognise the need to shift from a siloed mining-focused push model to an integrated value chain, demand-driven approach, but there are still fundamental barriers in business process and the supporting technology preventing a consideration of end-to-end optimality.This paper presents some elements of experiences working with companies to adopt such advanced approaches. In addition to algorithmic elements, an approach to phased and gradual deployment of progressively more sophisticated optimisation models is described. From a practical software adoption perspective, it is believed that this last concern is also of primary importance. Next generation approaches to the optimisation of complex bulk commodity demand chains, namely iron ore and coal are presented, with case studies in the world’s largest integrated operations in Western Australia and Queensland from the raw material mined through to market. Utilising accurate simulation models supported by metaheuristic optimisation techniques, a range of ways to engineer a dynamic decision support framework that can adapt and change with the inevitable changes in commodity markets is explored. Objectives such as total revenue, margin, cost, NPV, throughput, asset utilisation, contractual penalties and bonuses, and energy consumption can be managed simultaneously across the mine, plant, logistics network, port operation, shipping and sales domains.CITATION:Balzary, J and Mohais, A, 2014. Consideration for multiobjective metaheuristic optimisation of large iron ore and coal supply chains, from resource to market, in Proceedings Orebody Modelling and Strategic Mine Planning Symposium 2014, pp 213–222 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 24, 2014

This paper presents an overview of a program PC-BC developed for application to the design and evaluation of block cave operations. Conventional mine planning software tools are not well suited to the evaluation of this type of deposit. The paper looks at the modelling approach as applied to a block cave mining project. The following steps are described:Initial preparation of data including block models, draw point footprint geometry and draw cone geometry. Computation of individual draw point reserves. Procedure for modelling of vertical mixing of material within each draw point and subsequent determination of the best height of draw for each draw point based upon an economic cut-off value. Smoothing of draw heights amongst neighbouring draw points to produce a realistic draw envelope. Mineable reserves within the envelope are then computed. Tools for preparation and evaluation of various production schedules. This includes definition of draw rates, and rates for commissioning new draw points. In an operating mine, the capture and analysis of daily draw tonnages is important. How PC-BC accommodates this is described as well as the processes for depleting the draw column reserves. In the 12 years since the program was first developed, it has been used on a number of projects for feasibility studies and operating mines. Some practical examples of the use of the program in these projects are presented. Finally, some commentary on the sensitivity of various parameters is presented. Particular emphasis is placed on the overall footprint design.

Jan 1, 2000

By D Liu, M Edraki, L Berry

The presence of clay minerals slows down the settling rate and mitigates compact consolidation efficiency in tailings dewatering. The increasing use of saline water in many plants, affects the dewatering performance and presents the mining industry with new concerns. Efficient tailings dewatering is a great challenge due to the complexity character of tailings, especially clay mineralogy, clay content, and water chemistry. In this study, existing studies of the effect of different affecting parameters, such as pH, ionic strength and polymer flocculants, on clay aggregation behaviours are reviewed. The settling behaviours of three types of commonly observed clay minerals in tailings, kaolinite, bentonite, and illite, are also investigated in saline water with different water salinity as a case study. The settling rates of clay minerals are found to be affected by water salinity, clay type, clay content and polymer dosage levels. High salinity water hinders the settling of kaolinite but assists the settling of bentonite and illite through formation of different aggregation structures.The current work has indicated that strategies to promote more rapid dewatering could include adjusting flocculant type or level, water salinity and salt balance, and tailings solid content levels. Implementing dewatering strategies may require a more detailed knowledge of the effect of surface chemistry on the nature and strength of the clay inter-particle forces. This study discusses the research gaps on how to better manage clay-rich tailings in saline water and identifies new research directions. The development of a water management model, supported through in-line monitoring data to predict and manipulate of the surface chemistry of the clay component of the tailings could be a new direction to manage the issues associated with clay minerals in the process of dewatering and tailings management. Mine planning (water use requirements, operating costs) could benefit from more detailed studies on dewatering of clay-rich tailings in saline water. CITATION:Liu, D, Edraki, M and Berry, L, 2018. Improving the dewatering efficiency of clay-rich tailings in saline water, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 476–484 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By J Ireland, S Rose

The main outcomes of mining grade control include defining the boundary between ore and waste and then categorising the ore according to which stockpile it should be sent. A typical workflow includes using general mine planning software (GMP) – such as SurpacTM, VulcanTM or CAE StudioTM – to create three-dimensional wireframes of mineralisation domains, which are used to flag the relevant samples of interest and constrain estimation during block modelling. Creating the wireframes is a time-consuming process, requiring reasonable software skills, patience and an eye for detail. The interpretations can be subjective; indeed, even the same geologist will give different shapes if presented with the same data at different times. The process can become particularly tedious when trying to carry out updates due to new data. It can also be difficult to test the effect of alternative interpretations or grade thresholds because of the time constraints in production.There are now several implicit modelling tools available, either as standalone programs or as add-on modules to existing GMP. In this paper, the authors develop a workflow using implicit modelling methods to show how grades and geology can be rapidly interpreted to provide effective domains for grade estimation. The paper includes case studies from open pit gold mines. The implicit modelling approach can save several days of interpretation work for each grade control drilling campaign.CITATION:Rose, S and Ireland, J, 2014. Implicit modelling applied to grade control data, in Proceedings Ninth International Mining Geology Conference 2014 , pp 115–122 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 18, 2014

By A Whaanga

The use of photogrammetry has greatly increased the accuracy of 3D mapping underground. However, this has not reduced the need or desire for geologists to produce plans and sections showing an interpretation of the mapped geology. At the Waihi Underground Gold Mine, a hybrid solution has been developed that utilises the accuracy of photogrammetry and mapping onto face photos with the CAD-based Deswik.MappingTM functions to create plan and section maps. These have the benefit of looking like traditional paper maps but are more spatially accurate and richly attributed with metadata that can be filtered and exported to downstream processes. Deswik.MappingTM is a tablet-based solution that allows the geologist to map digitally with a stylus. Automation is utilised for the updating of survey as-builts, approved designs, drill holes, geological mapping, vein interpretations and mine work areas, reducing the requirement to print out maps at various locations and scales. Having 3D mine software on a tablet device provides a wealth of features not available when using paper: scaling is a problem of the past; information can be turned on and off; features can be viewed in 3D; and measurements between points of interest can be calculated in 3D space, for example, between vein wireframes and drill hole sample information. A suite of custom scripts has been developed that take the spatially accurate, registered and attributed polyline data from photogrammetry scans and converts them to a geological mapping legend with vein textures, structural information, and lithological boundaries. These 3D maps can be plotted in plan or section view and satisfy the requirements of the most ardent paper map supporter.

Mar 22, 2022

This paper discusses the requirements for a successful simulation modelling study, and the steps involved in the modelling process. Advantages and disadvantages of simulation are described, and a case study highlights how not to go about it. Two other case studies, for a decline truck haulage and a block caving production operation, are used to illustrate the types of variables whose impact may be investigated. Typical results are presented to indicate the sorts of presentation styles the author has found useful for conveying study results to project sponsors. Standard spreadsheet charting techniques can be very useful in this respect, but the possibilities are limited only by the imagination of the study team.

Jan 1, 2000

By O A. Aladejebi, S Mitra, T Singh, D J. Pinson, S, S J. Chew, T Honey

Currently, many commercial sinter plants are exploring the potential addition of high-grade iron ore concentrates to improve the sinter grade. A better understanding of the ore blend, granule behaviour and green bed properties is critical to making this change and maintaining productivity in the sinter plant. This study compared the performance of a laboratory scale granulation drum to a commercial scale unit. The blend used was an Asia-Pacific style sinter blend containing iron ore concentrates. The operating conditions of the two granulation drums (laboratory and commercial scale) were fixed at the same Froude Number (0.00337), space factor (15 per cent) and residence time (4.5 mins). The granules were characterised by measuring their mean size, size distribution and green bed voidage. It was found that the laboratory scale granules were representative of commercial sinter plant granules at similar moisture content. When the moisture was fixed at ~6.9 per cent, granulation time had no significant effect. A further fundamental investigation was undertaken to measure the water holding capacity and intra-particle porosity of the individual ores used in this study. The kinetics of water absorption were measured which showed that water absorbs quickly into the ore particles within the first 60 seconds, slowing down until final saturation was attained after six hours. A linear relationship between the water holding capacity and intra-particle porosity was noted for different ore particle sizes. The results of this study provide a baseline understanding of the current commercial sinter blend and encourage exploring the specific effect of increasing the proportion of ultrafine concentrates in sintering in a future study.

Sep 18, 2023

By J Gould, T Elkington

Mine operation strategies are commonly optimised with a net present value (NPV) maximisation objective. There are well known properties of a typical mining project optimised for NPV, including high production rates and declining cut-off grade schedules. In practice, however, frequently there are operations that diverge from such NPV-maximising properties. Although a range of reasons for this can be at play, one possible explanation is that operators intuitively adjust their strategies to compensate for the flaws inherent to NPV maximisation. In particular, NPV analysis does not reflect the benefits of managerial flexibility inherent in a mining plan. Real options valuation (ROV) is an alternative approach that addresses this issue. We compare the properties of NPV and ROV optimisation solutions generated for the same scenario. Our simple case study demonstrates that the presence of real operating options in the optimisation model not only entails increased project value as expected, but also tends to encourage lower processing capacity (with lower associated capital cost), higher cut-off grades and greater use of stockpiles.CITATION:Elkington, T and Gould, J, 2012. Real option value optimisation, in Proceedings Project Evaluation 2012 , pp 35-40 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 24, 2012

By S Mundell, J Armstrong, M Evans

"Automation is a common goal within the coal industry for reasons such as efficiency, reliability and sustainability. However, it requires standards and frameworks so business systems can communicate effectively. Automation of sample analysis processes has been difficult to establish due to a lack of direct business system communication between commercial laboratories and mining companies. This has resulted in manual procedures that have contributed to problems relating to analysis instructions, sample identification, results formats and visibility of status.These problems result in loss of data and confidence in data validity, loss of process efficiency and inability to react to issues. An Australian Coal Association Research Program project (Evans, Armstrong and Arboleda, 2014) has addressed these issues through the Coal Quality Data Exchange methodology for direct business system communication between coalminers and commercial laboratories to optimise the transfer of coal quality data.The benefits to the coalminer of the framework are:increased clarity and auditability of what is being sent to the laboratory and what was requestedreduced potential for error introduced through manual transcription tasksincreased speed of loading of analytical results to the customer Geoscientific Information Management Systemimproved turnaround time for analytical resultsincreased knowledge about what took place in the laboratory with respect to the determination of the analytical resultsincreased visibility of the status of a ‘work order’. The benefits to the technology companies and commercial laboratories is a common framework on which to build a sustainable solution that gets away from the multitude of formats catered for today and time consuming manual processes. The common framework significantly advances the future possibilities for the automation of sampling and analysis processes in a production environment.CITATION:Armstrong, J, Mundell, S and Evans, M, 2014. Automating communications between laboratories and mines – a case from the coal industry, in Proceedings Ninth International Mining Geology Conference 2014 , pp 351–360 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Aug 18, 2014

By H S. Welideniya, K Ekanayake

Carbon rich graphite deposits found in Sri Lanka are of inorganic origin and they occur as narrow steeply dipping veins. The vein width of these deposits varies from a few centimetres to metres, with an average vein thickness of 1 m. It is believed that the carbon rich fluid intruded into fracture zones under high pressure and the temperature has crystallised into graphite. This process has also generated many minuscule graphite veins centred on main mineralisation, which has reduced the host rock overall rock mass rating. These discontinuities could also be considered as joints with graphite infill. Graphite mining at Bogala Mines, Sri Lanka is a unique example of narrow vein mining faced with numerous wall stability issues resulting from weak graphite infilled joints.The Bogala vein type graphite orebody has an average vein width of 1 m. Overhand cut-and-fill mining method is used for stoping. The stope consists of two boundary winzes for material handling, access and ventilation. Mining is done on the strike of the vein and the average mining slice height is 2 m. A void to the height of one mined slice is left below the mining level during mining. Waste rock resulting from vein blasting and mine development is dropped into this void as fill rock. Any void height left greater than a single slice height will increase stresses in the stoping zone. This will increase formation of rock blocks and their effective separation from wall rocks. Split miniscule veins occurring around main mineralisation intensifies rock block formation in an environment of mining induced stress release. Consequently, any rock blocks sliding into stopes on graphite infilled joints will behave under constant normal stiffness (CNS) conditions and their shear strength will converge rapidly towards remoulded shear strength of graphite alone. Unlike with general infill deposited in joints, graphite has a very low friction angle and with its slippery nature, a small thickness may affect in great deal to reduce joint shear strength.In addition to immediate filling of excavated voids, controlled vein blasting and spot bolting have improved mine safety. Furthermore, rock bolts connected to each other through iron plates and anchored to anchor bolts installed in non-fractured solid rock are practiced to stabilise rock falls and wedge failures in narrow vein graphite mining. These practices have significantly contributed to safe mining without any rock bursts and catastrophic failures.CITATION:Welideniya, H S and Ekanayake, K, 2012. Challenges faced by narrow vein graphite mining and influence of graphite infill on wall stability, in Proceedings Narrow Vein Mining 2012 , pp 71-76 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Mar 26, 2012

By Y K. Ji, B J. Chung

In recent years, the utilisation of ultra-fine ore in ironmaking has gradually increased due to the depletion of high-quality iron ore. The use of ultra-fine ore in the ironmaking process is typically energy intensive and leads to high CO2 emissions. The improvement of sinter reducibility is one of the methods used to reduce the environmental impact of using fine ore.In this study, a high-strength and high-reducibility sinter manufacturing process was investigated by controlling the sintering reaction. The key technology used in this method is the manufacture of mini-pellets by selective granulation equipment. The mini-pellets consist of iron ore, limestone and burnt lime and are designed to melt at temperatures below 1200°C. The molar ratio of CaO to Fe2O3 of the mini-pellets is 0.25~0.75. The 2~5 mm diameter mini-pellets are manufactured with burnt lime as the binding material.During the sintering of mini-pellets, goethite, which has relatively high reducibility, should be retained as residual ore in the sinter cake. The strength of the sinter cake was kept by the bonding reaction of the mini-pellets, which have a low melting temperature. This is the main principle of the reaction-controlled sintering method.The reaction-controlled sintering method manufactures a high-strength and high-reducibility sinter cake and increases sinter productivity by around 15 per cent using ultra-fine iron ore.CITATION:Chung, B J and Ji, Y K, 2015. Production of high-quality sinter by controlling the sintering reaction, in Proceedings Iron Ore 2015, pp 21–28 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By M Allen

By its nature, the mining industry is energy and emissions intensive. In the future, the world will still require the outputs of mining but the industry will need to adapt to the low emissions economy. Understanding the risks of climate change to a particular site or at a company level is key to managing this transition.CITATION:Allen, M, 2018. Assessment of climate risk in the Australian mining industry, in Proceedings Life-of-Mine 2018, pp 13–16 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 25, 2018

By R Hartner

Digital optical microscopy (DOM) and automated SEM-based (ASEM) mineralogy systems (MLA, QEMSCAN) have experienced significant developments within the last decade. However these developments have been independent from each other and the two mineralogical techniques have so far not yet been integrated to combine the strengths and technical benefits of both analytical platforms. This detailed comprehensive mineralogical information is critical support for geometallurgy.Major hardware and software advances in DOM in the last few years have provided important new capabilities with potential applications to automated mineralogy. These technological advances have been largely driven by sectors outside mining (eg medical pathology) and have not yet been widely adopted within the minerals industry. The advent of DOM offers significantly more automated mineralogy capabilities than traditional expert-mineralogist driven optical microscopy. This is based on advances in automated image acquisition, high resolution cameras for digital imaging, imaging of large areas through mosaic options, integration of multiple layers and application of advanced image analysis techniques.Ongoing research involves combining the outputs of DOM and ASEM-based microscopy to create new capabilities for integrated microscopy based on development of advanced cross-platform image fusion and data integration between DOM and ASEM (exploiting the benefits of both analytical platforms). This requires non-linear image registration and transfer of mineralogical identification from ASEM to DOM systems using sophisticated image manipulation and data analysis software.Examples will be given of image fusion and data registration for a range of different ore types. Image fusion techniques are demonstrated using a porphyry copper deposit sample where sulfides and precious metals are classified using the MLA and gangue mineralogy obtained from DOM images. Data integration enables creation of a library containing optical property variability information for minerals identified by the MLA; thus reducing the reliance on skilled mineral identification by supplementing human interpretation

Sep 5, 2011

By D David

Amongst those whose task it is to design tumbling mills and other comminution machines there is an almost religious divide between devotees of the Bond method and devotees of other methods developed in more recent times. For a decade or so the issue was between the Bond power-based methods and the JKMRC (JK) simulation based approach. The newest method to challenge the status quo is power-based and was developed by Steve Morrell. As the title suggests, this paper will take some liberty at concluding that Fred Bond and Steve Morrell may be separated by history, but not by their approaches to their individual contributions to the science of comminution. Another driver for the paper is that although it is good to have diversity of thought, the existing divisions are problematic for those of us signing public disclosure documents. If alternative design methods produce materially different outcomes for the mill duty, then at least one of them is wrong or being used incorrectly. At some point the unsustainable argument may need to be put in a court of law that we metallurgists have two or more materially different design methods, each of which is correct! Therefore, perhaps a resolution is needed before this occurs?The works of both Fred Bond and Steve Morrell are each directly related to their contemporary grinding mill design and operational environments. Both their approaches are empirical, borne of observing and measuring real world situations. Both worked with theories that preceded them, gathered their own data and then each saw shortfalls in the status quo.Fred Bond was an escapee from revolution, a victim of The Great Depression, and had several near death experiences during his early site-based career. Perhaps he was fortuitously rescued from himself when asked by Allis Chalmers (A-C) to set up its rock testing laboratory in Milwaukie in 1930. Fred’s testing led him to conclude that neither the Kick nor the Von Rittinger theories explained his measurements. His writings on the failings of these old theories caused a divide between devotees of the old and new methods at that time. After many years, and much thought and plotting of data (the old way!), he came up with his now-famous equations (and his Third Theory) which have stood the test of time, certainly in the world of Bond-era machines.Coming from England via several African diamond mines, Steve Morrell immersed himself into the comminution world of the JK in Brisbane about a decade after Fred passed on. The JK had developed its semi-autogenous grinding (SAG) simulation framework using its own pendulum breakage tester, itself a derivative of the twin pendulum impact device invented by Bond decades earlier. At the JK Steve developed his authoritative Tumbling Mill Power equations and was involved in real world analysis of comminution problems on the global stage. Steve’s JK experience coincided with the demise of the rod mill, the rise of autogenous grinding (AG) and SAG milling and a rapid expansion in concentrator capacity.Morrell left the JK to pursue his own interests, which included ongoing consulting work, now demanded by the comminution world. He then turned to investigating a growing list of discrepancies between the opinions of designers and theoreticians, and the factual outcomes. The Morrell Method of design arose from this re-examination of ore testing, real world operating data and these glaring and expensive discrepancies between design and outcome. The elements necessary for a relook at the world of rock breakage were in place!CITATION:David, D, 2017. Steve and Fred would have been mates – a comminution design evolution story, in Proceedings MetPlant 2017, pp 2–11 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 11, 2017

By P Ridley

EnergyAustralia’s Sydney Central Business District (CBD) cable tunnel network will form a loop 6.2 km in length. The 3.2 km long, 3.5 m, diameter city east cable tunnel (CECT) currently in design, will complete the loop in 2014. This paper discusses the ventilation design of the CECT, considering operation for four functions:1. normal (unmanned),2. access (manned),3. purge, and4. emergency fire modes.The dominant design criterion which determines the required ventilation capacity for CECT is the specification of an upper air temperature limits of 35°C (dry bulb) and 24°C (wet bulb) for manned access, during all ambient weather conditions and cable heating loads. Simplistic static heat transfer analyses do not yield a sufficiently accurate calculation of tunnel air temperature and humidity to provide a safe and yet economical design. The primary refinement in the analysis discussed in this paper is associated with modelling of the system’s dynamic behaviour.Our means of analysis is through a thermo-fluid-dynamic simulation of the interactions between the diurnally and seasonally varying loads (cable heat generation, ambient air conditions and groundwater inflow), tunnel airflow and the resulting tunnel air temperature and humidity. These simulations are validated using experimental data from the existing city south and city west cable tunnels.Fire life safety scenarios are also analysed and discussed in association with the ventilation design. Ventilation strategies are developed for dealing with such emergency fire situations.The understanding and insight provided by the work offers the ability to optimise ventilation plant provisions in future cable tunnels, particularly long and high energy density tunnels.

Mar 8, 2011