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By E Hondros

Innovation and Business Skills Australia (IBSA) commissioned The Boston Consulting Group (BCG) to undertake a study into how the role of AustraliaÆs senior managers is likely to change between now and 2020 and to identify the skills and attributes that will be needed to respond to those changes. This report builds on a previous study prepared by BCG in the early 1990s for the Industry Taskforce on Leadership and Management Skills (Karpin Committee), which provided a snapshot of the Senior Manager in 2010. The following powerpoint slides summarise the 2020 Vision û The Manager of the 21st Century û outlining how the role of AustraliaÆs senior managers is likely to change between now and 2020 and to identify the skills and attributes that will be needed to respond to those changes. The presentation is summed up in the following quote from Jon Nicholson û Senior Vice President of BCG: We believe that to succeed in the years up to 2020, executives will need to master a range of hard and soft skills. Amongst other things, they will require to manage multi-generaional teams, the creativity to measure staff performance on outputs rather than inputs, and a high degree of technical and functional expertise in addition to their general management credentials. This paper is available as a PowerPoint presentation only.

Jan 1, 2006

By G McKay, M Erskine, S Macklin

The City of Sydney is currently investing in a number of infrastructure projects that require tunnel excavations within the Triassic Hawkesbury Sandstone. It is generally accepted that this formation has high residual stresses of ‘tectonic’ origin, so much so that these stresses have been implicated in a number of well-known failures and problems for tunnelling. These include failure of ‘roof beams’ comprising discrete beds in the crown of tunnel excavations; stress-induced spalling and ‘slabbing’ of tunnel walls; shear displacement between beds causing the failure of rock bolts; strain in adjacent infrastructure and, the necessity for re-grouting of high conductivity fractures due to stress relief dilation after excavation. Whilst there is an extensive published database of in situ stress measurements comprising ‘hydrofrac’, ‘over-coring’ and ‘slotter’ stress measurements, these data indicate a considerable spread of results. The traditional approach to interpreting this data has been to attempt to fit linear correlations to stress versus depth data, based on personal experience and ‘back-analysis’ of monitoring data during construction. However, there are a number of such correlations in the literature and there is divergence of opinion regarding the assessment of ‘background’ in situ stress and appropriate upper and lower bound values for design. This paper provides a brief review of the published data; suggestions on an alternative ‘risk-based approach’ to assigning in situ stresses for design; and, proposals on how in situ stress tests may be conducted in future to improve the quality of the database available to designers.CITATION:Macklin, S, McKay, G and Erskine, M, 2014. A review of the in situ stress database for tunnel design in the Hawkesbury Sandstone, Sydney, New South Wales, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 171–178 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By I Treloar, T Elenbaas, E Isaaks

Critical reviews of grade control generally focus on blasthole sampling and the estimation of ore control block model (OCM) grades, with little or no attention given to dig-line design. For example, the estimation of block grades is deemed important as estimation errors lead to the misclassification of ore types and subsequent dollar loss. Recognition of the problem that the underestimation of block grades may be more or less costly than overestimation led to the application of loss functions to the classification of individual OCM blocks by ore type. The method is known as maximum profit selection (MPS). However, each OCM block may be misclassified a second time by dig-line design. Although each block may initially be assigned an optimum ore type by MPS, OCM blocks are seldom individually mineable by ore type. As a result, a common solution to this problem is the design of mineable polygons or dig lines loosely constrained by a minimum mining width. All material within a properly designed dig-line polygon can be mined and sent to a single destination such as the mill, stockpile or waste dump. These dig lines are often designed manually or by simple variations of computer-generated contour lines. They are generally suboptimal and result in additional misclassifications of ore types. This paper provides an algorithm for constrained optimum dig-line design where dig-line misclassifications are also evaluated through loss functions or MPS. Constrained optimum dig-line designs minimise the dollars lost by dig line misclassifications for a given minimum mining width constraint. A case study is provided illustrating constrained optimum dig-line design and subsequent benefits.CITATION:Isaaks, E, Treloar, I and Elenbaas, T, 2014. Optimum dig lines for open pit grade control, in Proceedings Ninth International Mining Geology Conference 2014 , pp 425–432 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 18, 2014

By D David

The development of Western Australian magnetite deposits has lead to the design of some of the largest grinding mills and plants in the world. One of the projects demonstrates the efficiency gains possible by developing a simple yet thorough test program for circuit design. By drawing on the experience of current magnetite operations in Australia and the Mesabi and Marquette iron ranges in the United States, a basic flowsheet was developed. Through comprehensive testwork with AG, ball and stirred milling the flowsheet was optimized to take full advantage of each grinding mill’s strengths to reach the required final grind size. Laboratory work was verified in the pilot plant to optimize the energy efficiency of each grinding step while ensuring adequate liberation at each step for sufficient gangue rejection. By using three stages of grinding, the ball mill can best be employed in ensuring all top size gangue material is liberated and removed in the second magnetic separation step. The inclusion of the IsaMill, with its inherent steep product size distribution, as the tertiary grinding stage ensured that maximum grade was achieved and simplified the downstream process while giving further improvements in total grinding capital and operating costs. In this way the combination of the two technologies downstream from the AG mill is far more efficient than either would be on its own by reducing the total installed power by 1/3 and annual grinding media cost by 2/3.

Aug 8, 2011

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

By C McGuire

As mobile equipment electrification in underground mining continues to gain popularity, control ofheat and humidity in the workplace is becoming a key driver in sizing of ventilation and mine aircooling systems. For design and sizing of ventilation and cooling systems to be accurate, and for themine mobile equipment fleet to be sized appropriately to meet production goals, vehicle productivitymetrics, heat modelling, and energy balances for electrified fleets need to consider operation througha realistic duty cycle that is reflective of various tasks performed during a shift.The authors conducted a real-world comparison of two 8 cubic yard (14 metric tonne) class Load-Haul-Dump (LHD) machines – one diesel and one battery-electric vehicle (BEV) – performingidentical muck-haul-dump operations on consecutive days at an underground nickel/copper hardrock mine in Ontario, Canada.The battery-electric LHD averaged 8.9 per cent faster cycle time than the diesel vehicle (gross,without accounting for charging time), and was able to transport 25 per cent more material per cycledue to a larger bucket capacity. When including the charging time, average net cycle times wereequivalent for the two vehicles over the 200 cycles. The BEV carried more payload over the eighthour period due to the increased capacity per cycle.The testing identified an approximately five-fold reduction in heat output from the BEV in comparisonto the diesel LHD on a basis of heat output per tonne of rated bucket capacity. Heat output from thefast charger was found to be approximately 4 per cent of the charging rate, with negligibletemperature change observed in the main drift. External noise levels in the mine were found to be14 dB lower for the BEV during transit and 11 dB lower during bucket loading. Fuel/energy costs forBEV electricity input were approximately four times lower per operating hour than diesel fuel costbased on typical 2021 electrical and diesel unit rates for a grid-connected mine in Ontario, Canada.

Oct 12, 2022

By H Q. Zhang, M C Chai, W Fu, H Y Chen, L M. Wei, Q J. Yang

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. The Fozichong deposit – located in the south-western segment of the giant Qinhang metallogenic belt, South China – is a large-sized lead-zinc polymetallic deposit. This deposit contains two main ore districts, termed as the Guyi ore district in the north and the Hesan ore district in the south respectively. We present an integrated data set on sulfide minerals, fluid inclusions and stable isotope (H-O-S-Pb) geochemistry to better understand the features and genesis of the Fozichong deposit.Field and paragenetic relationships indicate three mineralisation stages forming the early (Po+Sp+Gn+Ccp+Py+Di+Ep+Qtz), middle (Sp+Gn+Ccp+Py+Ep+Chl+Qtz) and late (Gn+Sp+Py+Qtz+Cal) sulfide assemblages respectively. Mineral chemistry – particularly S/Fe and Co/Ni ratios in pyrite, Zn/Fe, Zn/Mn and Zn/Cd ratios in sphalerite and Pb/Ag ratios in galena – indicates a magmatic association for the sulfide minerals.Quartz and calcite coexisting with the sulfide minerals of various stages host abundant fluid inclusions. Quartz in the early stage contains two- or three-phase CO2-H2O and liquid-rich aqueous inclusions, which have homogenisation temperatures of 162~365°C and salinities of 2.9~17.8 wt per cent NaClequiv, whereas quartz and calcite from the middle and late stages are dominated by two-phase, liquid-rich aqueous inclusions that have slightly lower homogenisation temperatures (153°C~320°C) and much lower salinities (1.0~6.0 wt per cent NaClequiv). Hydrogen isotopes (dD = -59‰~-41‰), analysed using fluid inclusion waters from quartz and calculated oxygen isotopes (d18OH2O = -5.47‰~4.00‰) for the equilibrated ore fluids, indicate that the ore-forming fluids may have been sourced from magma and mixed with groundwater in the late stages. Sulfide minerals have d34S values of 2.3‰~4.3‰, consistent with a magmatic-derived source for sulfur. Lead isotopes (206Pb/204Pb = 18.592~18.794, 207Pb/204Pb = 15.648~15.864, 208Pb/204Pb = 38.909~39.580) confirm that lead and, by inference, zinc were mainly derived from magmatic rocks, with subordinate contributions from sedimentary rocks.Various lines of evidence support that the formation of the Fozichong deposit has close genetic association with the granite porphyry intruded in the late Yanshanian period (106 Ma), and it can be classified as a magmatic hydrothermal type lead-zinc deposit. We propose that the Hesan and Guyi ore districts may represent the proximal and distal products of a magmatic – hydrothermal system respectively.CITATION:Fu, W, Zhang, H Q, Chai, M C, Yang, Q J, Chen, H Y and Wei, L M, 2015. Genesis of the large-sized Fozichong lead-zinc polymetallic deposit, Guangxi, south China – constraints from the sulfide mineralogy, fluid inclusions and isotope geochemistry , in Proceedings PACRIM 2015 Congress, pp 609–614 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

By G Collecutt, D Proud, D Humphreys

"The hazards associated with dust explosions are well known, and coal dust explosions present a significant hazard in the underground coal mining industry worldwide. In earlier work, we presented computational fluid dynamics (CFD) simulations and test results for coal dust explosions within a 2.5 m diameter circular gallery, along with CFD simulations and test results for the suppression of these explosions with finely atomised water sprays. In this paper, we present refinements to the CFD modelling that yield a significantly improved calibration with the test results, and proceed to investigate by CFD the requirements for suppression of a coal dust explosion in a typical underground roadway. This work was carried out under an ACARP project and we gratefully acknowledge their assistance. CITATION: Proud, D, Collecutt, G and Humphreys, D, 2015. Computational fluid dynamics modelling of coal dust explosions and suppression systems, in Proceedings The Australian Mine Ventilation Conference, pp 309–314 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Aug 31, 2015

By R Zhang, J Xu, X Lv, C Bai, S Zhang

This paper studies the grinding behaviour of vanadium-titanium magnetite concentrate in a ball mill. The grinding kinetics, surface morphology, lattice distortion, wettability and moisture capacity were analysed. Grinding kinetics equation was established based on population balances model with the size distribution data from a laser diffraction technique. The SEM photos of the ground concentrate showed that the surface gets rough with increasing grind time. Agglomeration of fine particles was enhanced when the grinding time reached 30 minutes. X-ray diffraction results showed that a loss in crystalline occurred with increasing the grinding time. The peaks of the X-ray diffraction patterns are significantly broadened with increasing grinding time. Wettability, characterised by contact angle between the material and water, improved due to the fact that the surface roughness increased with increasing grinding time. Moisture capacity of concentrate ascends abruptly in the first three minutes and then changed slowly with increasing grinding time. The water transfer coefficient in the particles increased rapidly in the first six minutes and then decreased quickly until grinding time reached 12 minutes.CITATION:Zhang, R, Lv, X, Bai, C, Xu, J and Zhang, S, 2013. Wet grinding of ?vanadium-titanium magnetite concentrate in a ball mill, in Proceedings Iron Ore 2013 , pp 511-518 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013

By A Bagis

Road tunnels are an accepted and effective transportation solution in urban areas to mitigate increasing traffic congestion and facilitate improved urban connectivity in a cost effective manner while meeting societal goals to reduce the impact of construction. In designing a tunnel system, there is a requirement to achieve an acceptable level of in-tunnel air quality, as well as meeting ambient air quality goals. In Australia, there is also a requirement for zero portal emissions which means that all pollutants must be emitted to the atmosphere via a ventilation stack.Traditionally, effective pollutant dispersion has been achieved by constructing tall ventilation stacks which disperse pollutants into the atmosphere at a high level. The dominant variable parameters in the effectiveness of the dispersion under the ventilation engineers control are the efflux velocity, the height of the ventilation outlet and the concentration of pollutants at the point of discharge. During off-peak operations the required ventilation exhaust rate can be reduced due to the decrease in traffic. This can lead to a drop in the efflux velocity from the stack and therefore the effectiveness of the dispersion. This potentially drives the need for a higher outlet, or an increased exhaust rate to achieve a higher efflux velocity with consequent effects on energy consumption.The paper proposes a method of varying the cross-sectional area of the ventilation stack with the use of motorised control dampers, thereby maintaining a sufficiently high efflux velocity throughout the 24 hour period independent of traffic conditions. This allows the use of a potentially shorter ventilation stack.

Mar 8, 2011

By P Holtham, J Meng, E Tabosa, W Xie

Turbulence and its distribution are of great importance in flotation, and have received considerable attention recently. However, there is no mature technique to measure turbulence in three-phase (liquid-solid-gas) industrial flotation cells due to the opaque, highly aggressive and abrasive nature of the slurry involved. Previous research has shown that the piezoelectric vibration sensor (PVS) is a promising tool for turbulence measurement in industrial flotation cells. The PVS is a robust device that converts mechanical vibration to electrical signal, from which turbulence information can be extracted. An improved calibration method has allowed development of a frequency model to calculate the force applied to the sensor. Experimental results and comparison with laser doppler anemometry (LDA) have shown that the PVS can measure fluid kinetic energy, which is related to turbulent kinetic energy, a parameter used in the literature to represent turbulence in flotation. Laboratory measurement in a two-phase (water and air) 60 L cell and with slurry in a 3.5 L cell gave good stable results and mostly consistent trends between the measured turbulence profile and cell operation. When applied in a 300 m3 industrial cell filled with water, the addition of air or slurry to the cell resulted in a shift in the turbulence profile. This is expected because a change in fluid density will change the force applied to the sensor. It is therefore concluded that the piezoelectric sensor is an easy-to-use and robust technique that is fully capable of measuring turbulence in industrial flotation environments.CITATION:Meng, J, Tabosa, E, Xie, W, Runge, K C and Holtham, P, 2014. Development and application of a piezoelectric sensor for turbulence measurement in industrial flotation cells, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 457–470 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014

By P Woodward, T Ly, N Muhamad

OZ Minerals' Prominent Hill copper-gold concentrator is located 650 km north-west of Adelaide in the Gawler Craton of South Australia. The concentrator was built in 2008 and commenced commercial production in early 2009. The Prominent Hill concentrator is comprised of a conventional grinding and flotation processing plant with a design capacity of 8 Mtpa. The flotation circuit includes six rougher cells, an IsaMill for regrinding the rougher concentrate and a Jameson cell preceding the three stage conventional cell cleaner circuit.Since its commissioning, the Prominent Hill flotation circuit has been the focus of a series of projects aimed at continual performance improvement. This has been achieved by a systematic approach of project identification, evaluation and implementation which has led to a progressive improvement in flotation performance. Innovations that have been successfully implemented include aspects of cell design and operation, and reagent suite optimisation.Improvements to the mechanical cells initially focused on the installation of a modified rotor-stator design in the rougher circuit, as recommended by Outotec. Isolated cells were fitted with this technology and proven to provide a benefit for copper recovery before the design was trialled in subsequent cells along the bank. Based on this success, further modifications were made to other aspects of the rougher and cleaner cells.Laboratory trials conducted at Prominent Hill involve a screening process identifying potential reagents from a list of products, which are then rigorously tested in the laboratory before one is selected for trial in the concentrator. Where these reagents have demonstrated a statistical improvement in performance they have typically been incorporated permanently into the flotation circuit. This paper discusses the process of continual improvement at the Prominent Hill flotation circuit and the optimisation achieved by the implementation of key initiatives.CITATION:Woodward, P, Muhamad, N and Ly, T, 2013. Optimisation of the Prominent Hill flotation circuit, in Proceedings MetPlant 2013 , pp 431-444 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 15, 2013

By D L. Reid, G Nwaila, J Petersen, J-P Franzidis, Y Ghorbani, M Becker, F C. de Beer, L C. Bam

Traditional methods of gold extraction have involved comminution and processing via cyanide leaching, all of which are associated with energy, cost and environmental implications. Subsequently, numerous opportunities for improvement and optimisation strategies in gold mining and processing have been explored, including heap leaching, which has significantly lowered comminution costs. This paper explores the effect of the more energy efficient high-pressure grinding rolls (HPGR) on the comminution behaviour (especially on the crack density) and cyanide leaching performance of laboratory reactors study on run-of-mine gold ore comprising the Ventersdorp Contact Reef (VCR) and the Elsburg Reefs (ER), sourced from Carletonville in the Witwatersrand Basin in South Africa. The ore was comminuted using HPGR at three different pressure settings (120, 90 and 60 bar). Large (-16/+11.2 mm) and small (-5.6/+4 mm) particles of the HPGR product where then mineralogically characterised using optical microscopy, quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) and X-ray computer tomography (CT) before cyanidation. The results of the leach experiments indicated a correlation between gold extraction, particle size and crack density. Mineralogical characterisation of the ore indicates that the Fe-sulfides present in the VCR are likely to be more reactive than those in the ER, thus having a more favourable influence on gold cyanidation. Overall, the results show promise for the heap leaching of Witwatersrand gold ores prepared using HPGR and demonstrate the value of a multi-disciplinary geometallurgical approach.CITATION:Nwaila, G, Becker, M, Ghorbani, Y, Petersen, J, Reid, D L, Bam, L C, de Beer, F C and Franzidis, J-P, 2013. Morro do Ouro geological model with a metallurgical view, in Proceedings The Second AusIMM International Geometallurgy Conference (GeoMet) 2013 , pp 75-84 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 29, 2013

By R Wynn, R A. Pax, S Mann, B Cornish

The semi-autogenous grinding (SAG) mill at the MMG Century operation has failing load cells that are essential to the control strategy used to stabilise the mill. Currently, mill-bearing pressure is used as a proxy for the load cells, but it has been found to be a noisy signal and lacking in useful sensitivity. It is also prone to variations and drift due to temperature. After consideration of a number of options, a non-contact acoustic array has been installed around the SAG mill to provide a more stable proxy load signal as well as other information about the internal operation of the?mill.The installation consists of 12 microphones to provide some detail into the operational differences that occur during normal operations at the MMG Century SAG mill. This acoustic approach acknowledges that operational grinding mills emit significant acoustic emissions that are a consequence of the dynamic environment prevailing inside them.Previous studies have attributed the acoustic noise to a range of events that occur inside these mills (Pax, 2011; 2012). Consequently, non-contact acoustic determinations of in-mill behaviour can provide powerful insights into the operation of the primary comminution tumbling mills. By measuring key microphone signal attributes at different positions around a mill, a holistic picture of mill internal operation can be developed.This paper will describe the installation of the 12 microphones and discuss the use of the acoustic load signals as a proxy for failing load cells. It will also present data from new observations of internal mill dynamics and the results of implementation of control using these acoustic signals. Key to the control approach has been the development of a logically coherent picture of the processes inside the mill.CITATION:Pax, R A, Wynn, R, Mann, S and Cornish, B, 2014. Implementation of acoustic arrays for semi-autogenous grinding mill?operation, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 273–282 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014

By R A. Pax, B Cornish

"Although it is well known and easily experienced that the feed size distribution influences the throughput and stability of operation of a semi-autogenous grinding (SAG) mill, the details are poorly understood since it is often only the input and output measurements that are used to identify unfavourable in-mill conditions. Load cells and power monitoring are sometimes used but are generally poor indicators of the mechanisms that lead to such unwanted conditions.At the MMG Century operation a 12-microphone array around the SAG mill using non-contact acoustic measurement methodology has been used to diagnose the in-mill conditions to facilitate improved throughput and stability of operation. Use of acoustic measurement and control has provided a demonstrated increased throughput of at least 20 per cent as well as improved stabilisation of the mill. Since the information derived from the acoustic noise from a mill allows discrimination of the behaviour of the steel balls and the rock, a number of in-mill conditions can be identified with signals that include toe and shoulder angles, water holdup and the ball to rock ratio.Feed size variations, measured online with an imaging system, have been used to determine their effect on the internal charge behaviour. It has been found that circumferential segregation of steel balls and rock occurs as well as poor mixing of large rocks. Both of these effects are not conducive to optimal breakage rates of different size fractions. Longitudinal segregation effects also occur. This paper presents and discusses these results and illustrates how the new acoustic knowledge can be used to manage and improve mill operation and stability.Citation:Pax, R and Cornish, B, 2016. Understanding Size Effects of Semi-autogenous Grinding (SAG) Mill Operation as a Pathway to Solving Feed Disturbances - Case Study using the MMG Century SAG Mill, in Proceedings 13th AusIMM Mill Operators’ Conference 2016, pp 321–330 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Oct 10, 2016

The transition from low stress to high stress conditions is a challenge eventually faced by most mines in Australia that extend to depths greater than (generally) about 1000 m. In areas with strongly adverse 'stress versus depth' gradients, such as some parts of Western Australia, significant stress-related problems have occurred at depths as shallow as 300 m below surface. The actual depth at which the 'transition' occurs is a function of the local pre-mining stress field, the strengths of the various rock types hosting the deposit and the layout and sequencing adopted in the mine. Stress-related damage can result in increased support costs, and delays associated with rehabilitation and disruption to production. In the worst case, where strong seismicity and associated damage occurs in active mining areas, 'exclusion' zones and 're-entry' protocols may be required. These can severely disrupt production. A key aspect of managing the transition is the recognition of the onset of stress-related ground behaviour. Damage mapping can be used to develop understanding of the relationships between mining activities and the local and regional response to them. Carefully documented case histories provide a basis for calibrating numerical models. This paper discusses some of the typical styles of ground behaviour observed in higher stress conditions in underground mines. A simple damage classification scheme is described to assist in 'damage mapping' of mine tunnels. An example of damage mapping is presented to illustrate an approach commonly used for recording stress-related damage.

Nov 25, 2010

By T J. M Harvey

This paper gives an overview of the ASHRAE LibHuAirProp, CoolProp and REFPROP software packages. These packages were predominantly developed for heating, refrigerating and air conditioning engineers and the refrigeration and steam power industries, although CoolProp and REFPROP also cover combustible gases. The main aim of this paper is to highlight the existence capabilities and status of the different packages and where they can be used. The paper gives typical examples of the use of these software packages, specifically as Excel add-ins, and provides a comparison of results of typical mine psychometric and gas drainage calculations using the packages and more traditional ventilation and gas drainage calculation methods. The paper also introduces a hybrid method that improves accuracy compared to traditional methods. In typical mine situations, the use of software packages is probably not required; however, with the increasing accuracy of instruments, potential greenhouse emission costs and the sale of mine gas, more accurate measurements and calculations can potentially save (or make) significant sums of money.CITATION:Harvey, T J M, 2015. The use of psychometric, thermodynamic and transport property software in mine ventilation and gas drainage calculations, in Proceedings The Australian Mine Ventilation Conference, pp 201–210 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 31, 2015

By D Stepanenko, G Stovpchenko, L Lisova, D Togobitskaya, L Medovar

Classical electroslag remelting of consumable electrodes is a drop-by-drop melt feeding through a slag layer into a renewing molten metal bath, slowly solidifying into a homogeneous, dense, defectfree ingot in a copper water-cooled mould. The new look at the additive nature of the electroslag remelting (ESR) process in a protective atmosphere allowed us to formulate the principles of a comprehensive thermodynamic-based model that can predict dynamic changes in slag and metal composition at certain ingot remelting. The model considers drastically different slag-to-metal mass ratios at the beginning and end of remelting and predicts gas, slag and metal composition in a chain of thermodynamic subsystems. Despite consisting of calcium fluoride and stable oxides, the ESR slag can oxidise main and active elements from steel and alloys (primarily aluminium, titanium and silicon) due to chemical reactions between slag and metal. ESR is not an electrochemical process in its nature. However, slags are ionic melts and deviation in their composition causes a change in their properties, affecting both operation mode and ingot quality. Another important understanding derived from the modern metallurgy technological route is that the ability to refine metal from impurities is not a priority for the ESR because consumable electrode has already passed all stages of refining and deep degassing at ladle treatment that changes ESR slags engineering principles. The critical importance became slag’s ability to generate process heat and keep the melting composition in the metal bath unchanged (except for non-metallic inclusions assimilation). Slag engineering for ESR required a compromise between chemical inertness to a metal composition and desired physical properties deriving from technological reasons. The Directed Chemical Bonds Concept (DCBC) in a multicomponent oxide system was used to build predictive models of electric conductivity and the melting temperature of fluoride-oxide slag based on their chemical composition. Both models help to design a customised composition of effective slags for steel and alloy groups or individual grades, and they are significant steps in the development of a comprehensive model of electroslag remelting.

Aug 21, 2024

By A Tawadrous, B Wheeler, D S. Preece, S A. Silling

The two key results of rock blasting are fragmentation and movement of geomaterials. Movement/flow of the blasted rock is often referred to as heave. Moving rock with explosives rather than mechanical equipment can improve mining efficiency. Such is the case with coalmine cast blasting. Controlling and directing rock movement through explosive deck delay timing can greatly improve ore recovery by segregating ore and waste. In both cases, understanding, predicting and controlling heave is an important element of successful blasting.Computer programs for predicting 2D blasting-induced heave have been used in mining for decades, helping to drive the innovation of new and more efficient mining methods, ie cast blasting. The past few years have seen the advent of 3D distinct element modelling of blast-induced heave. This is an important advancement because most blasting situations are three-dimensional in nature, especially when controlling the direction and intensity of rock movement through explosive deck delay timing.This paper documents the first full-scale blasting simulations in 3D with distinct element models that include hundreds of blastholes and in excess of a million particles, made possible with parallel processing. Surface mineral blasting is the focus of this study which treats the effect of blasthole delay timing on ore recovery. Ore waste and dilution resulting from typical row-on-row delay timing will be demonstrated. Also demonstrated will be the ore recovery possible with delay timing designs that significantly enhance ore/waste segregation. This type of high fidelity modelling and the use of electronic detonators makes possible the sculpting of rock blasting muck into separate piles of ore and waste.CITATION:Preece, D S, Tawadrous, A, Silling, S A and Wheeler, B, 2015. Modelling full-scale blast heave with three-dimensional distinct elements and parallel processing, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 127–136 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By M Hopkins, A Mutale, A E. Vidal da Silva

The Cliffs Nickel Mine extracts a narrow near vertical nickel vein using a mining method of underhand bench stoping with paste backfill. In 2014, at a depth of 400 m below surface, the Northern block of the mine began to experience squeezing within ore development. At first the deformation was localised, within 30 m of the stoping front, but later became pervasive extending across the Northern block and resulting in a hiatus in mine production. The global mechanism is a progressive pillar failure, where the inter-level pillars in advance of the production front could no longer withstand the induced load and progressively yielded. The local mechanism of failure was observed as crushing of the massive sulphide ore and ‘punching’ of the pillars into the ultramafic hangingwall exhibited as floor and sidewall dilation and unravelling of the mafic footwall. The cause of the global mechanism was attributed to a combination of factors, including: high overall extraction ratio, small vertical pillar heights between ore development, high stress in relation to the low rock mass strength, shallow stope front angle, and insufficient ground support capacity. Following the progressive failure, the remnant rock mass conditions across the northern block were severely degraded, with numerous falls of ground that led to a reassessment of the mine plan. Recovery of the Northern block started in 2016 as a staged process. Development of the safe recovery work methodology involved a number of considerations, such as: production sequencing, development access design, ground support, and development of specific procedural controls. The Northern block was then broken into smaller mining precincts based on tactical factors such as location, ease of access, scale of rock mass damage and nickel content. A specific ground support standard and work methodology are employed, while cycle sheets are used to ensure quality and completeness of work. Large intersections showing signs of deformation have either been bypassed or treated using Rocprops to maintain stability during stope production. This approach has been successful in safely regaining access and restarting production in areas that had previously been removed from the mining reserve.

Mar 15, 2021