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By J Greberg

This paper discusses the use of simulation in the mine planning process. A case study on the Newcrest Cadia East project is presented, and the challenges and possibilities for using simulation as a tool for mine planning and scheduling is discussed.The simulation study presented in this paper was performed during the project’s prefeasibility stage, and focused on the planning and scheduling of the development of panels in the future mine. The Cadia East project will be the largest underground operation in Australia and the first using panel caving. Simulation was used in order to optimise the development of panels; it was mainly used in order to verify the plans for the development process and allocate resources in an optimal way. The work was performed as an iterative process and adjustments to the plans were made according to simulation results. Bottlenecks were identified and different scenarios were tested.The results from the simulation study shows how different operational constraints affect the planned development process and how changes in priorities can be necessary in order to maintain a high development speed. Furthermore the study shows how changes in planned mine layout requires changed strategies, and how this was solved using the simulation tool.In this paper the authors critically discusses the use of simulation in mining operations: what are the limitations and challenges of using simulation as a tool for mine planning and scheduling, what are the benefits, and what do we aim for in the future?

Nov 22, 2011

By G R. Hancock, D Verdon-Kidd, M J. Saynor, J B. C Lowry, T J. Coulthard

The ability to simulate the stability of post-mining landscapes over time scales ranging from decades to millennia is a critical element in the assessment of closure designs for uranium mines. Landscape Evolution Modelling (LEM) technologies provide a means to simulate and assess the long-term geomorphic stability of a conceptual rehabilitated landform for periods of thousands of years. However, a major issue with simulations derived from long-term modelling are the limitations associated with the data inputs. Specifically, simulations which utilise historic rainfall data only represent the variability of rainfall events that have occurred over a relatively short period. Consequently, these simulations run the risk of not accounting for the full range of rainfall variability that might be expected over an extended period of up to 10 000 years. Therefore, for this study a probabilistic approach was adopted to generate a stochastic synthetic rainfall data set to produce a series of unique rainfall scenarios, each representing a simulated period of 100 years. Importantly, utilising such an approach allows uncertainty in predictions to be better accounted for and provides a range or probability of likely outcomes.In this study, the effect of ten individual rainfall scenarios are assessed in terms of their impact on the predicted erosion and denudations rates produced by the CAESAR-Lisflood LEM for a conceptual rehabilitated landform of the Ranger Uranium Mine (RUM) in the Northern Territory of Australia, focusing on the Corridor Creek catchment (Figure 1). While legislation requires this site to be erosionally stable for at least 10 000 years (Commonwealth of Australia, 1987), here the focus is on the first one hundred years of landscape evolution, as this is the period in which erosion is expected to be higher, with limited vegetation cover or pedogenic development in the initial decades after rehabilitation. It is also the period where the drainage pattern is set.CITATION:Lowry, J B C, Verdon-Kidd, D, Hancock, G R, Saynor, M J and Coulthard, T J, 2016. Application of synthetic rainfall data to long-term modelling of a rehabilitated landform, in Proceedings Life-of-Mine 2016 Conference , pp 75–79 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jun 28, 2016

By R Yang

This paper presents a fragmentation model for large production blasts in an open pit or underground environment. The paper shows that the particle velocity is directly related to pressure, strain, and strain rate and so it can be considered as driving force and mechanism of rock fragmentation. This is supported by the fact that a vibration with a larger peak particle velocity (PPV) generates larger disturbance in rock and so finer fragmentation or more blast damage than a low PPV. The crack distribution in rock from impact is based on findings from previous researchers (Seaman, Curran and Shockey, 1976; Liu and Xu, in press). The fragmentation size is calculated at three-dimensional grid points within a blast. The fines and oversized blocks are calculated explicitly – the fines generated close to blastholes and big blocks far from boreholes are modelled naturally. The multiple blasthole fragmentation (MBF) model takes surveyed irregular geometry of the free face of a blast as the calculation boundary. The MBF can model fragmentation with over one million grid points. Examples of the model’s field comparison are also included.The PPV at a calculation grid is estimated based on the same approach used for the near field non-linear vibration model (Yang and Scovira, 2007). The method is based on the dominant charge for a calculation grid point, non-linear charge weight superposition within a charge and from multiple charges, strain wave broadening, and amplitude attenuation with distance from a charge segment. The blasthole confinement affected by earlier firing charges is also taken into account.The MBF model inputs from blast design, such as: location and orientation of each blasthole, stemming length, blasthole diameter, multiple decking, bench height, initiation sequence, etc. It models the effect of the delay and its scatter in each blasthole on fragmentation and has a statistical modelling capability for geological random variation on attenuation of particle velocity wave. The wave reinforcement due to instantaneous waves arriving or diminishing cooperative contribution due to long delay intervals between charges is also simulated.The results are displayed in 3D volumetric plots, contour of fragmentation in cross-sections, and size passing curves for a whole blast or a region of the blast.CITATION:Yang, R, 2015. A multiple blasthole fragmentation model – its concept, formulation, capability and field comparison examples, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 177–186 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By J E. Everett

Maximising ore tonnage at a selected target grade requires that appropriate ore identification criteria be established. Iron ore mining block models may consist of many millions of estimated blocks, each block corresponding to the selective mining unit (SMU), with grade interpolated from drill hole data. Each block can be considered as a potential ore candidate. Analysis of such a huge database can require large computational resources, especially for sensitivity analysis requiring multiple computations. However, an alternative streamlined approach is possible, where the data are compressed to an appropriately smaller and representative subset. The consequent data reduction not only makes it feasible to consider the simultaneous analysis of multiple pits but also considerably speeds up computation, enabling sensitivity analysis of the potential ore tonnage as a function of the required grade. Ore identification criteria can be successfully established using appropriately chosen reduced data comprising less than one per cent of the blocks. The ore identified is virtually indistinguishable in tonnage and grade from the ore that would be selected using the entire block model.Two methods of data reduction are tested: sampling (using a proportion of unaltered blocks) and binning (consolidating groups of blocks to a single average grade). The source blocks are first sorted (such as by location, analyte grade, principal component score, random order or value) before sampling or binning. In this study, the sorting options considered were by location and Fe grade. The effectiveness of each method was evaluated using the block model subsets to select the maximum tonnage of ore at a specified target grade. Block model data from an anonymous Pilbara iron ore project with about one million blocks averaging 1.132 kt were used. The blocks are from multiple resource models, to be blended to a single product. Sampling is shown to be superior to binning because sampling preserves the full variability while binning, although matching the mean block grades reduces their variability.It was found that the appropriately sampled data sets (sorted by location) gave results virtually identical to the results for the full data set, even when the samples comprised less than one per cent of the original blocks. The reduction in computer time to identify maximum tonnage at a specified grade was approximately proportional to the sample percentage. The increase in computation speed greatly facilitated sensitivity analysis. A sampled data set of one-eighth the total block model was used to investigate the effects of changing each of the component grades around the original grade specification. The results of this sensitivity analysis are discussed, and illustrate the potential benefit of carrying out sensitivity analysis in determining feasible and marketable product grades.CITATION:Everett, J E, 2015. Block model data reduction and sensitivity analysis, in Proceedings Iron Ore 2015, pp 263–270 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By B Wong, R G. Coleman

In flotation, the selection of the size, number and type of cell for a particular duty depends on two important factors. Firstly, the required flotation residence time and secondly, the physical constraints of how much concentrate can be recovered for a given froth surface area and concentrate lip length. The residence time is influenced by ore type and characteristics such as liberation, kinetics and reagent dosage. The amount of concentrate that can be recovered for a given froth surface area and lip length depends on ore type and other characteristics such as particle size, specific gravity and mineral grade. Residence time is determined through a combination of laboratory-scale test work and design scale-up factors. However the critical froth transport parameters such as froth carry rate and froth lip loading cannot be determined in a laboratory. This is because the froth is scraped during a laboratory flotation test and thus does not exhibit natural behaviour, and it is not possible to scale-up froth transport distance or air rate. These values are generally compared via calculation to rule-of-thumb maximum values to establish if these values will be exceeded by the flotation cell selection.This paper first reviews these critical froth transport parameters and then discusses actual parameter values across diverse operating sites, with varying cell duties, cell sizes and types, orebodies and particle sizes. These values are compared against the industry rule-of-thumb to test the applicability of the rule-of-thumb to actual performance. Options are also presented for adjusting these parameters in operating flotation cells.CITATION:Coleman, R G and Wong, B, 2018. Flotation launder design and the measurement of critical froth transport parameters, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 353–362 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

By J Zhang, O Ostrovski, C Zhang D Cai, Q Wang

The conventional CaO-SiO2-based mould fluxes are not suitable for high-Al steel casting because of the strong reaction between silica in the flux and aluminium in the steel strand. In the process of casting of high-Al steel, flux composition changes; with the decrease of the silica concentration and increase of alumina. Knowledge and understanding of the effect of the Al2O3/SiO2 ratio on flux structure and properties are useful for flux design for the high Al-steel continuous casting. This paper investigated the effect of the Al2O3/SiO2 ratio on structure, viscosity, phase composition of fluxes quenched at different temperatures and heat transfer of CaO-Al2O3-SiO2-B2O3-Na2O-Li2OMgO- F fluxes. It was found that flux melting temperature increased with the increase in Al2O3/SiO2 ratio. Viscosity of the flux melts increased significantly with the increase of the Al2O3/SiO2 ratio from 0.7 to 1.2, reaching the maximum value, and then decreased with further increase of the Al2O3/SiO2 ratio. Raman spectroscopy analysis revealed that the change of the Al2O3/SiO2 ratio led to the change of aluminate and silicate structural units. The turning point for viscosity was attributed to the change in the degree of flux polymerisation. X-ray diffraction (XRD) analysis showed that increasing Al2O3/SiO2 ratio increased crystallisation tendency of the fluxes. Heat transfer measurement by infrared emitter technique (IET) revealed that increasing Al2O3/SiO2 ratio led to the decrease in heat flux which is correlated well with the increased crystallinity of the flux. The results suggested that the flux with Al2O3/SiO2 ratio 4.3 is the best candidate among the studied CaO-Al2O3-based mould fluxes for casting of high-Al steel.

Aug 21, 2024

By Sparrow G. J

In a recently completed AMIRA project, 20 samples were searched for gold mineralisation using the automated location facility (ALF) for rare phases on a scanning electron microscope in the CSIRO Division of Mineral Products, Melbourne. The samples were submitted by mining companies in Australia, and Papua New Guinea, and included crushed ore samples, cyclone overflow and underflow products, a flotation concentrate, and 12 tailing samples. Their gold contents ranged from 600 to 0.2 g/t An. Native gold and gold minerals including a gold telluride, gold-silver tellurides, and a gold bismuth mineral, were located in the samples as free grains and associated with other minerals such as pyrite, magnetite, hematite, ankerite, copper sulphides, silicate minerals, and quartz. In the highest grade samples, both micron sized and 200 ¦m grains of gold were found with ALF. It would be difficult to locate such d wide size range of gold in a manual search. Gold mineralisation was located in the tailing samples assaying 0.4 g/t An and higher. In several tailing samples coarse grains of native gold over 40 p.m in size were located. One grain was estimated to have contributed 40 per cent of the gold in the sample. As well as locating gold mineralisation, the ALF examination resulted in the identification of uranium, mercury, and bismuth minerals in the samples. Knowledge of the distribution of these minerals in processing streams could be important in the operation of a concentrator.

Jan 1, 1992

By C M. Standen

The SAG mill at Rasp Mine has undergone a number of liner design modifications since commissioning in 2012, making liner wear and failure difficult to predict from historical data. During 2017, several instances of liner failure or near failure were experienced resulting in unplanned downtime for emergency relines or to patch liners in the lead up to a planned shutdown. The strategy for relining mills is often to minimise the frequency of relines (and subsequent shutdown costs) by extending liner life, achieved through design modifications. However, it was observed that as the Rasp SAG mill liners wear, mill performance declined with power draw increasing and throughput declining. Opportunity and inefficiency costs start to erode the revenue per additional tonne milled for a given set of liners, and in turn the benefit of delaying relines. As such, optimising the frequency of relines becomes a trade-off between reline costs and opportunity/inefficiency costs in delaying relines. The aim of this paper is to demonstrate a frame work for analysing costs using a marginal economic analysis with the assumption that the Law of Diminishing Returns can be applied to the life of mill liners. The SAG mill operating variables can be modelled to determine their impact on costs and an optimal reline point can be defined where the total costs are minimised. This prevents unexpected failures due to accelerated wear by providing justification to reline earlier and thereby allowing efforts to be focused on sustaining milling performance.CITATION:Standen, C M, 2018. An economic approach to optimising mill reline frequency – a case study of SAG mill relines at Rasp mine, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 197–206 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

By M D. Griffith

Oct 12, 2022

By A Flatten, F Reusch

Recent advances in the disciplines involved in simulating large mining operations provide increasingly precise and accurate methods for the study of cave mechanics; however, in large regional-scale models, hydrological aspects are often neglected or studied independently from the mechanical problem. There exists a great demand for a unified approach to study and simulate both the mechanical and hydrological phenomena that allows for a more detailed understanding of the effects of groundwater flow, dewatering and the impact on block cave mining operations.This paper presents a numerical framework that combines three-dimensional regional-scale hydrological simulation techniques for groundwater flow, together with non-linear continuum–discontinuum rock mechanics models, provides such a unified modelling approach. The underlying simulation technique is based on a coupled parallel solution formulation adopting single-phase fluid flow formulations into a discontinuous, strain softening and dilatant finite element model. This approach is adopted for the presented case study of a realistic block caving example in a simplified unidirectional coupling formulation, to investigate the effects of the mechanical analysis on the hydrological response. Here, particular emphasis is on the non-linear coupling of the deformable and strain-softening solid skeleton and fluid phase; eg the change of hydraulic properties with evolution of damage in the rock mass and large-to-intermediate scale structures due to ongoing caving operations. The importance of discontinuum structures is discussed, as mining-induced fault reactivation significantly influences the hydrological response.CITATION:Flatten, A, Reusch, F and Beck, D, 2016. The application of hydromechanical mine-scale modelling for large block caving operations, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 341–348 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By R Hughes

"Spring Creek Mine uses high pressure water to extract the thick Main seam in the Upper Rewanuicoal measures. The extraction method results in the creation of large voids which collapsespontaneously. This can result in the displacement of large volumes of methane, which may create a signifi cant hazard if not correctly managed. A system of automatic dilution doors is employed to mitigate this risk. This paper describes the evolution of the system and gives some examples of its eff ectiveness."

Jun 1, 2012

The constructionhunnelling industry in Hong Kong has taken an upturn during the last few years due to the commencement of works to relocate the International Airport to Chek Lap Kok Island. The Airport Core Program consists of ten individual projects including roads, landfill, bridges and tunnels to build the airport and link it to the mainland of Hong Kong. Part of one of these projects is Cheung Ching Tunnel located on Tsing Yi Island. The proposed tunnel consists of a 1.6 km twin tube road tunnel through the island's central ridge, taking three lanes of traffic each way. Each tunnel is 16 m wide - (the widest road tunnel in Hong Kong) and are 10 m high. ICI Explosives (China) saw an opportunity to supply bulk explosives to the Cheung Ching tunnel and contacted ICI Australia to determine availability of a bulk system for tunnel blasting, and assist in its introduction. This paper discusses the methodology behind developing that bulk system to suit a large tunnel drill and blast operation. It also looks at the problems encountered along the way, from the development of the product to the application of the system in the tunnel and the eventual success of introducing a bulk system into a large tunnelling project.

Jan 1, 1994

Computer software has been developed to link real-time information generated by underground mine ventilation airflow monitoring sensors into a network simulation program to undertake network simulations and allow interpretation of key system data and operational changes. Results were used in the development of a computerised monitoring and simulation system to provide immediate or real-time data on air behaviour within each branch of an underground mine ventilation network through linking of sensors to the ventilation network simulation software. The outcome of the project is an online system that can report changes in the mine ventilation system, allow causes of changes to be isolated and rectified, improve balancing of available air throughout the mine, allow improved approaches to regulator setting and dispense with much of the labour used for underground ventilation measurement. The work activities in both coal and metalliferous Australian mines have involved examination and modelling of regulators, software modification and considerable mine site testing and optimising activities. There is some discussion on approaches to control of flow through ventilation systems with increased information. New systems will be part of a total mine information management system. They will have to be cost effective and justified by gains in productivity. New systems will need to provide simulation of contaminant production such as diesels, vehicle heat, strata heat, radiation, blast fumes and other gases. More robust real-time ventilation simulation systems will be required. Personnel and vehicle identification and production tracking will be collected to provide integrated ventilation system monitoring and control. This paper examines a study to gain greater understanding of computerised real-time airflow monitoring and control within the mine production system to provide immediate simulated information in each branch of an underground ventilation network and to allow interpretation of key system data and operational changes. A case study implementing a real-time airflow monitoring and control is discussed. Approaches to control of flow through ventilation systems with increased information are discussed. The concept of a system that can be linked to or be part of a total mine information management system is developed. Such a system can form the base for mine automation that allows mines to incrementally and cost effectively implement monitoring and control to further seek gains in productivity.

Jan 1, 2005

By L R. Sousa, M He

Rock burst is common in deep underground excavations and is characterised by a violent ejection of block rocks from excavation walls. It is critical to understand the phenomenon of rock burst and particularly the failure mechanism. Laboratory experiments are one of the ways. For that purpose, a rock burst laboratory test system was developed at the State Key Laboratory for Geomechanics and Deep Underground Engineering at the China University of Mining and Technology, Beijing. A true triaxial test system, designated the Deep Underground Rock Burst Analogue Test Machine, was developed, which can transfer a stress state from three-direction-compression on six surfaces to the compression on five surfaces with one set free. The rock burst experimental system comprises an acquisition of acoustic emission signals, a high-speed recording in order to accurately record the kinetic characteristics of rock fragments ejected during a rock burst event and the possibility of infrared thermography showing the surface temperature of the samples. In this paper, analyses of typical results from rock burst tests are presented with a description of the obtained results. The mechanisms of rock burst are illustrated, and a rock burst classification is proposed based on these laboratory tests. For the control of rock burst, the constant resistance, large deformation (CRLD) bolt or anchor is presented for accommodating the large displacement of surrounding rock masses and absorbing the impact of the sudden release of rock burst while outputting a constant resistant force in response to the external load. The CRLD bolt or anchor has had practical applications in underground mines. Finally, in situ tests performed in a tunnel at Qingshui coalmine, China, are analysed in detail.CITATION:He, M and Sousa, L R, 2014. Experiments on rock burst and its control, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference , pp 19–32 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 5, 2014

By L Kormos, V Lawson, G Hill, G Marrs

"In sulfide nickel deposits throughout the world, pentlandite and pyrrhotite are commonly found together along with varying amounts of chalcopyrite and platinum group minerals (PGMs). The mafic or ultramafic host silicates associated with the sulfide mineralisation commonly exhibit a complex assemblage of magnesium bearing silicates, many of which themselves contain significant nickel. Four types of ore are proposed, each presenting their own processing challenges. These are: economic grades of Ni, Cu and PGE (platinum group element) in a pyrrhotite-bearing sulfide deposit, with low pyrrhotite to pentlandite ratios  economic grades of Ni, Cu and PGE in a pyrrhotite-bearing sulfide deposit, with moderate to high pyrrhotite to pentlandite ratios uneconomic high pyrrhotite: low tenor deposits low-grade low sulfide, high MgO ± PGE deposits that can sometimes be economically mined and processed.The grades and recoveries of nickel concentrates produced from sulfide ores can be significantly impacted by the ore mineral texture, the nickel tenor of the sulfides, and the polytype of pyrrhotite which may be either hexagonal (non-magnetic) or monoclinic (magnetic). The mineralogy of the silicates is also of great importance, especially the magnesium silicates and those which tend to produce particles which are asbestiform or which affect slurry viscosity. Other magnesium silicates such as serpentine carry nickel in solid solution, limiting the recovery entitlement of nickel by flotation because serpentine is not amenable to sulfide flotation mechanisms. Differences in plant flow sheets and reagent assemblages are required to effectively separate these minerals.Experience from a variety of plant operations and from extensive flow sheet development programs are discussed. Examples are given of where significant improvements in nickel circuit performance can be made by adjusting plant physical processing conditions or process chemistry to compensate for measurable ore properties and characteristics.CITATION:Lawson, V, Hill, G, Kormos, L and Marrs, G, 2014. The separation of pentlandite from chalcopyrite, pyrrhotite and gangue in nickel projects throughout the world, in Proceedings 12th AusIMM Mill Operators’ Conference 2014, pp 153–162 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Sep 1, 2014

By S Long, D Carnovale, L Louwrens

The Mt Wright underground mine (MTW) is located near the town of Ravenswood in north Queensland and is operated by Carpentaria Gold – a wholly owned subsidiary of Resolute Mining Limited.The Mt Wright mine has gone through many stages, from the conception and implementation of the world first ‘sub-level shrinkage’ stoping (SLS) with continuous fill mining method in 2010, through to steady state production. These have been outlined in detail in papers presented by Mackay (2011) and Mackay, Long and Koen (2014) at previous Underground Operators Conferences.Since the last paper was presented, MTW has experienced significant change in two key areas.The first significant change was the discovery of a previously unknown hazard in the form of flat rilling events (FREs) from closed drawpoints (DPs). These events are believed to be unique to MTW and pose a significant risk to both the safety of personnel and the business as a whole. The paper will discuss this hazard and the evolution of the controls and practices that have been introduced to mitigate the risk posed by the identified hazards. The material involved in these events is extremely dry, fine and hot.The second significant change is an altered stress regime bought on in part by a change in the production front orientation and a general deterioration in ground conditions in some areas of the mine. This has caused some production interruptions at MTW. The second half of the paper will describe the challenges encountered, the mechanisms behind these challenges and the strategies implemented to safely return MTW production to planned levels.It is believed that other operations can learn from the issues mentioned above, and the paper has been written with this in mind.`CITATION:Long, S, Carnovale, D and Louwrens, L, 2017. Mt Wright – managing unique risks, in Proceedings 13th AusIMM Underground Operators’ Conference 2017, pp 295–304 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 16, 2017

By J J. L du Plessis, A Spaeth

The objective of this paper is to demonstrate the efficiency of machine-mounted active explosion suppression systems (AESS). Their proven effectiveness against methane explosions is highlighted, as well as their additional potential when used as an early warning system should frictional sparks occur during the coal-cutting operation at the coalface.Methane and coal dust explosions remain one of the primary and unpredictable risks in underground coal mining. Although technologies such as proactive ventilation, methane monitoring and wet-head cutting systems are widely used as preventative measures, there are no fail-safe controls able to reduce the risk to zero. None of these controls is designed to be able to counter the negligence associated with human error or to deal with rapidly changing face conditions which could lead to flammable gas ignitions. Machine-mounted AESS have been installed on various continuous miners as an additional control to further reduce the risk of ignitions and to act as a safety shield when all the other precautions taken have failed. This was the primary motive for the development of AESS. As an additional feature, the ExploSpot® AESS is being enhanced to identify frictional ignition sources at the coalface that reach a predefined monitoring level. This functionality may serve as a further effective preventative measure.As part of ensuring coalmine operational safety, the detection of frictional ignitions can play a huge role in creating heightened awareness of potentially dangerous situations. By being able to process the frictional spark burning pattern, the AESS could support the decision-making process regarding whether to continue the coal-cutting operation, whether there is a need for maintenance or whether the operation should be stopped completely due to the increased risk of a flammable gas ignition and an ensuing explosion.CITATION:Spaeth, A and du Plessis, J J L, 2015. Enhanced risk reduction using early warning technologies embedded in active explosion suppression systems, in Proceedings The Australian Mine Ventilation Conference, pp 315–322 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 31, 2015

Historic mining across the Bendigo goldfield reached an average mining depth of 750 m over an area of about 16 km by 4 km, with two shafts exceeding 1400 m. Mining ceased in the mid 1900s due in part to increased dewatering and ventilation demands. Water extraction technology of the day, combined with multiple mine ownership, did not allow uninterrupted and thus economic mining activity to prosper. Today Bendigo Mining Limited (BML) is targeting gold-bearing reefs beneath the water-filled historic mine workings. To ensure mining activity can proceed without the risk of water inrush, historic workings are being dewatered by submersible pumps in historic shafts and through a series of underground drain holes intersecting old workings. Due to the high heads involved, individual drain hole development requires rigorous safety control implementation and assessment prior to drilling. Water extracted via drain holes is pumped to the surface through a series of pipe lines and rising mains in conjunction with two staged pumping stations. Both stations are equipped with high-speed centrifugal pumps, each capable of pumping 40 L/s at a static head of approximately 300 m. BML, which operates beneath and within a large city, is confronted with unusual environmental and social challenges compared to many within the mining industry. The raw mine water, which contains elevated salt levels, is piped through residential areas and must comply with strict controls to prevent impacts on the surrounding environment. The final delivery point is BMLÆs water treatment plant at the north end of the city. The water treatment plant utilises chemical pretreatment and reverse osmosis. It is able to process 7 ML of mine water per day at full production. The product is approximately 5 ML of reusable irrigation quality water, which is made available to the Bendigo community for public gardens, sporting facilities and rural irrigation. The 2 ML of brine is directed to a purpose-built evaporation pond facility located 7 km north of the water treatment facility.

Jan 1, 2008

By J Robinson, L D’Uva

"The Gold Fields group and Gekko Systems have successfully worked together on multiple projects, including at the St Ives, Agnew and Granny Smith operations in Western Australia, and the Damang operations in Ghana, with gravity recovery design, technology installation and optimisation the key driver on each occasion.In 2014, Gold Fields Australia identified an opportunity to challenge the historical thinking at Granny Smith and reassessed the benefit of upfront gravity gold recovery. The historical approach had been to employ gravity on the tailings stream of the carbon-in-pulp (CIP) circuit, recovering sulfide minerals into a concentrate from spiral concentrators for further liberation of gold via a regrind circuit.Gekko was engaged to assess the implementation of a gravity circuit within the grinding area, and to perform a comprehensive gravity recoverable gold test program. Test data was fed into the AMIRA P420 BCC Gravity Model to confirm the gravity recovery potential of the ore, and for process design basis generation. Height, space and capital limitations proved to be a design challenge. However, collaborative learnings throughout the project ensured the design and operation of a reliable and economic gravity gold circuit. Ultimately, the Granny Smith gravity circuit was a success, satisfying all the project objectives and yielding consistent, measurable benefits. On average, the gravity circuit recovers 33 per cent of total gold, resulting in an increase to overall gold recovery by 0.7 per cent.This paper highlights the key project drivers for Gold Fields, and the development of the Granny Smith free gold gravity circuit. It details application of test work and modelling, and the challenges and learnings encountered during the design, installation and commissioning stages. This paper seeks to demonstrate that continuous improvement in a long standing operation can be beneficial to overall circuit flexibility and increased ounce production.Citation:D'Uva, L, Robinson, J and Bell, T, 2016. Defying Gravity - Brownfield Continuous Improvement, in Proceedings 13th AusIMM Mill Operators’ Conference 2016, pp 135–144 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Oct 10, 2016

By C M. MacRae

The characterisation of high-P iron ores by field emission gun electron probe microanalyser (FEGEPMA) was carried out to determine elemental associations in iron oxides sensus lato and, using this knowledge, to speculate on possible P incorporation mechanisms in goethite. Quantitative data was collected from two goethite-rich bulk ores and results showed that in both samples goethite was the main repository for phosphorus. The P-rich goethite also contained elevated levels of both aluminium and silicon.To understand the mechanism of P incorporation in goethite, high-P grains were located by coarse mapping of polished blocks with the FEG-EPMA. Analysis of element distribution maps collected on the P-rich grains showed that low-P regions within grains were typically associated with low-Al and high-Si, whereas high-P regions were associated with high-Al and low-Si. Based on follow-up quantitative analyses, a coupled substitution mechanism for phosphorus incorporation within goethite was proposed: 2Si4+ = 1P5+ + 1Al3+. Additional quantitative analyses on further examples indicated the mechanism was only valid for Si contents in goethite of <1 wt per cent.Preliminary transmission electron microscope (TEM) studies confirmed the presence of P, Al and Si in goethite.

Jul 11, 2011