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This paper discusses the prediction of subsidence over partial extraction systems in thick coal seams. A model based on empirical techniques using influence functions is developed to calculate the surface ground settlements above extraction panels. Independent of the influence function, two field parameters, the subsidence factor and the angle of draw (limit angle) are required to define the model. Both these parameters are best observed from critical or super critical subsidence areas. However in thick seams, extraction widths are typically sub critical and therefore it was necessary to refine an estimation process for sub critical conditions. Partial extraction systems in NZ are characterised by variability with respect to extraction thickness and depth. As extraction proceeds along a panel, conditions deteriorate once the critical span width is exceeded and therefore percentage extraction decreases. A further variable was introduced to the modelling which allows for varying extraction sequences. Two comparisons with field observations, one over a partial extraction panel, the other over abandoned workings, showed the method gave good agreement to measured subsidence values.

Jan 1, 2002

By N Haque

Base metal ores contain low levels of toxic/hazardous elements such as arsenic, antimony, bismuth, cadmium, lead and mercury. Given the large tonnage of base metal ores mined and processed each year globally, the accumulated mass of minor elements introduced into the biosphere is large and could be expected to have a significant environmental impact. Life cycle analysis (LCA) is a methodology that has been developed to assess the environmental impacts of material supply chains over their entire life cycle. Assessing the toxicity impacts of metallic wastes and incorporating these impacts into LCA methodology is not a simple task given the complexity of the issue. However, research and methodology development is in progress internationally to address this. Despite limitations concerning the lack of a coherent framework for characterising the toxicity impacts of metals, including issues such as bioavailability, a study was carried out to give first estimates of the relative toxicity impacts of various waste streams from metal production processes. The wastes considered were: red mud; sulfide tailings (copper, nickel, lead/zinc); lead/zinc slags; synthetic rutile residue; iron oxide residue; and copper slags and anode slimes. These toxicity estimates can be considered the æworst caseÆ scenario for these wastes, where all the metals present are bioavailable. Combining estimates of the amounts of the various waste streams produced in Australia each year with the toxicity results showed that despite their relatively low human toxicity impact per unit mass compared to some other waste streams, red mud and the various sulphide tailings had the highest annual human toxicity load on the environment, along with copper smelting slag and dust. Data from the pH dependent leaching test reported in the literature were assumed to represent first approximations of metal bioavailability and used to compare the two approaches to estimating the toxicity impacts of red mud.

Jan 1, 2009

L&M have been involved on the Shotover since 1980 when we joined Jack and Barney Ryan, who had started in 1972 with gold at $45 per ounce after a successful career as roading and demolition contractors in Christchurch. The first 85 tonne plant was a typical NZ trammel-riffle table plant with an armour plated hull for surviving Shotover floods, and was fed by a 53 tonne UH20 excavator. All this gear had to be carted in over the Skippers road on a small truck or sledge for the heavy loads. This operation was successful and generated the cash flow to sample the lower section of river and plan a second plant. To reduce fine gold losses this was planned to be a jig recovery plant and also included a vibrating screen which saved space and weight over a trammel. There are five flowlines of primary jigs and one secondary, followed by two Knudsen bowls for cleanup.

Jan 1, 1985

By E Topal

Stopes are used in several underground mining methods. Boundary determination of these stopes is generally based on simple rules of thumb. While several stope boundary optimisation techniques are available, they fail to guarantee true optimum results. The first part of this paper reviews some important stope boundary optimisation studies and proposes a new algorithm to optimise stope boundaries and layouts for underground operations. The second part applies the proposed algorithm to a block model to test its ability to produce optimum results and demonstrate its applicability in a number of different scenarios. The results demonstrate that the proposed algorithm can find optimum stope boundaries and layouts in three dimensions for different stope sizes and economic conditions.

Jan 1, 2009

By Kuganathan K, Potvin Y

Enterprise Mine at Mount Isa is to expand ore production from the current 1.4 to 3.5 mtpa by mining the 3500 Orebody, from which production is scheduled to start in February 1998 making this the deepest underground mine in Australia with its lowest mining horizon at nearly 1.6 km below surface. The following fill requirements were defined for the 3500 Orebody during the feasibility study: 1. a minimum filling rate of 250 ma/h, 2. a curing time of 28 days, and 3. minimum free fill water. This paper mainly describes the investigation of high density and paste fills for the 3500 Orebody. The investigation covered all the key issues relating to fill option selection, including design criteria, material supply and demand assessment, drainage modelling, tailing dewatering method, mix design and a pump loop test. Results of the investigation indicate that both high density fill and paste fill are technically feasible. The investigation has led to the selection of a blended tailing paste for the 3500 Orebody as the paste option has significant advantages over high density fill in stope filling rates and fill reticulation. The blended tailing for paste fill is finer than Isa deslimed tailing but coarser than full plant tailing. The paste fill selected has minimum binder and tailing dewatering requirements while a relatively high filling rate is achieved.

Jan 1, 1998

By L Manca, P B. Hills, D Tyler, N Pollington

This paper describes a collaborative project undertaken by Newcrest Mining Limited (Newcrest) and pitt&sherry to identify, develop and then implement global best practices to manage the exposure to inrush (dry and mud) hazards in underground mining operations. An extensive literature review was undertaken to identify past experience globally and the current state of knowledge and practice in managing inrush hazard. A key requirement of the literature review was the development of a list of guiding questions which would form a framework for approaching operators to discuss the topic, capture recent learnings and understand current operating practices to allow the development of a best practice solution. An initial cohort of 14 mines across four continents chose to contribute and detailed interviews were carried out by the project team. The outcome from the literature review, interviews with participating mines and various internal discussions was a comprehensive summary document detailing Basic versus Best Practice management of the inrush hazard. This document is being used as a gap analysis tool by Newcrest to assess and guide the management of inrush hazard at their existing and future operations. The summary document has also been provided to the participating mines for their consideration. The project is iterative and will continue to evolve as new experiences, knowledge and practices come to light.

Mar 15, 2021

By A McGann, P J. Coghill, D Miljak

"It is widely accepted that bulk ore sorting could provide a step change in processing of low-grade ores. For this to be achieved a rapid, accurate bulk sensor of grade is required as well as sufficient natural variation of grade in the ore stream. CSIRO trialled a magnetic resonance (MR) sensor capable of measuring chalcopyrite, and by inference total copper grade, on the 1300 t/h Ridgeway portal conveyor. The gauge produced an unprecedented set of data down to a 1 t scale for months at a time. This paper analyses the measured variation and compares it to a simple model derived from the bore core data and mixing within the block cave mine.The model of the small-scale (<1000 t) variation is developed using fractal methods which have successfully been used in the past for copper porphyry deposits showing a power law or near power law distribution of copper grade and vein sizes. These fractal distributions have two features highly favourable for segregating ore, a large proportion of low-grade pods and the large-scale spatial clustering of grade. We show the presence of fractal ordering in bore core data at short range in the Cadia Ridgeway porphyry deposit and measure its persistence in the crushed rock produced by the Ridgeway block cave mine over one month. The model is then extended to demonstrate the effect of varying head grade, mixing and pod (or diversion) weight on bulk sorting efficiency.CITATION:Coghill, P J, Miljak, D, McGann, A, 2016. Modelling Grade Variation in Crushed Ore at Cadia Ridgeway and Its Potential Consequences for Bulk Ore Sorting, in Proceedings The Third AusIMM International Geometallurgy Conference (GeoMet) 2016, pp 77–88 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Jun 15, 2016

By D R. Venkatesulu, N K. Nanda

Due to increased production of steel in India, the thrust is now on iron ore producers not only to enhance productivity from existing mines, but to look also into alternative resources, like lean grade iron ores such as banded haematite quartz (BHQ)/banded haematite jasper (BHJ), which are available in abundance but not yet utilised for want of suitable process technology. In this context, BHJ ore from the Bellary-Hospet sector was collected and subjected to detailed physical, chemical and mineralogical characterisation and beneficiation studies. The as-received sample was found to occur physically as alternating layers of haematite and jasper. The chemical analysis of the sample was 41.20 per cent Fe, 39.10 per cent SiO2 and 0.86 per cent Al2O3. Based on the mineralogical observation, haematite was found to be the lone ore mineral and jasper was the major gangue mineral. The microscopic observations revealed that the ore minerals liberate at a top size of 0.150 mm. Guided by the characterisation results, indicative tests were conducted using gravity and magnetic separation equipment, namely, Floatex«, gravity slime table and wet high intensity magnetic separator (WHIMS). The results indicate that it is possible to upgrade the sample by both gravity and magnetic separation techniques. However, the WHIMS results indicate that jasper grains report to the concentrate at higher gauss intensities. Therefore, based on the encouraging gravity separation results and the availability of new design spirals for treating fine particles, the applicability of gravity spirals for beneficiating BHJ in the liberation size range of -0.150 mm was studied. The sample was ground to a top size of 0.150 mm and was subjected to preconcentration using wash waterless spirals. Tests were conducted at different feed rates, pulp densities and splitter positions. The results indicate that it is possible to upgrade the sample from a feed grade of 41.20 per cent Fe to a preconcentrate ranging from 46 per cent to 62 per cent Fe with a yield ranging from 19 per cent to 55 per cent. The obtained preconcentrate was then subjected to a cleaning stage by using a combination of wash water and wash waterless spirals. The test results indicate that it is possible to obtain a final concentrate assaying 65.75 per cent Fe and 4.75 per cent SiO2 with a yield of 25.9 per cent and an iron recovery of 41.31 per cent. It was concluded that further test work is necessary to increase the recovery and improve the product specification.

Jan 1, 2009

Thallous chloride and cadmium metal were recovered from a thallium-cadmium concentrate by a method suited to the treatment of small batches. Differences in oxide solubility and control of pH were employed to separate the thallium and cadmium. The cadmium metal produced by zinc reduction analysed better than 99.95 per cent Cd and thallous chloride of high purity was precipitated from solution.

Jan 1, 1969

By H Y. Niu

The coal left in the goaf is easily submerged by groundwater damage. During the mining process of the underlying coal seam, it is necessary to drain the water in the overlying goaf. The coal sample is prone to spontaneous combustion after being soaked in water and air-dried. To explore the effect of micro-functional group transformation of water-immersed coal samples on the spontaneous combustion characteristics of coal samples during the low-temperature oxidation process. Using the experimental method of infrared spectroscopy, the migration law of special functional groups under different oxygen concentrations of water-soaked coal samples was analysed. By means of thermal analysis, the endothermic and exothermic properties of the functional groups in the water-soaked coal samples were studied. The results show that: the higher the oxygen concentration, the more oxygen-containing functional groups in the water-soaked coal sample, compared with the 18 per cent oxygen concentration, the 14 per cent oxygen concentration has a small increase, and the chain length is shortened. The temperature increase together with the oxygen concentration content determines the functional group content, the pyrolysis process produces some functional groups. The lower the oxygen concentration, endothermic rate decreases and endothermic temperature increases, the higher the ignition temperature of coal oxy-combustion, the lower the total heat release, the higher the burnout temperature, and the faster the oxygen-absorbing weight gain and the conversion of functional groups. Below 14 per cent oxygen concentration, the oxidative combustion process will be greatly reduced. The results provide a theoretical basis for preventing long-term water-soaked coal body oxidative spontaneous combustion in shallow buried coal seams.

Oct 12, 2022

By H F. Yu, S Ueda, J Diao, W F. Gu, Y Sasaki, H Qin

The main reason for the underutilisation of steelmaking slags is their instability, which is influenced by their complex phase structure. Recycling and sustainable steelmaking slag face challenges due to the presence of magnesium oxide (MgO), a crucial component in steelmaking slag. This study investigates the phase evolution of steelmaking slag during the cooling process with different MgO contents, using high-temperature experiments and FactSage™ software, ver 8.1, (by Thermfact/CRCT and GTT-Technologies) thermodynamic equilibrium calculations. X-ray diffraction (XRD) and scanning electron microscope - energy dispersive x-ray spectroscopy (SEM-EDS) analyses identified main phases in steelmaking slag, including Ca2SiO4 (C2S), RO (MgO-FeO solid solution), Ca2Fe2O5 (C2F), and Ca3SiO5 (C3S). The study reveals that RO phase increases as the MgO content increases. C3S precipitates from steelmaking slag with a 12 mass per cent MgO content at a reduced temperature of 1400°C. It is important to note that C3S remains in the steelmaking slag even after slow cooling. This may be due to the substitution of Ca2+ in C3S by Fe2+ and Mg2+ ions. Intriguingly, the precipitation of f-CaO in steelmaking slag with 10 mass per cent of MgO content occurred after one year, while there was no manifestation of f-CaO precipitation in the steelmaking slag with 12 mass per cent of MgO content even after one year. This discrepancy suggests a potential stabilising effect of an appropriate amount of MgO in steelmaking slag. However, it is crucial to emphasise that this inference lacks supporting data, necessitating further research to validate this hypothesis. The significance of this work is in uncovering the complexities of steelmaking slag behaviour, providing essential insights for optimising recycling processes. The research sheds light on the factors that influence the phase composition and stability of steelmaking slag, contributing to the utilisation of steelmaking slags, promoting environmental sustainability, and enhancing the overall efficiency of metallurgical processes in the current industrial landscape.

Jun 19, 2024

By T M. Campos, H A. Petit, L M. Tavares, R Olympio

Much practical experience has been gathered in the last 30 years of application of high-pressure grinding rolls (HPGR) integrated with ball milling in size reduction of fine iron ore concentrates. The company Vale S.A, in Complexo de Tubarão (Brazil), was one of the pioneers applying the technology prior to pelletisation with an outstanding size reduction energy efficiency in the circuit and a significant increment in the specific surface area of the product. Recent studies by the authors demonstrated benefits of modelling and simulation to improve the performance of HPGRs in this particular application, with the model being able to describe HPGR performance under different operating conditions and under variations of feed size distribution. Despite these important advances, this modelling approach has only been used offline and under steady-state conditions. The present work applies the modified Torres and Casali model proposed by the authors in pseudodynamic simulations. The ability of the model to predict the characteristics of the product in real-time is evaluated using data available online for the pellet feed preparation circuit. Results demonstrated the model capabilities to map the physical operation and give a realistic representation of the process. Additionally, the model is demonstrated to be able to support the pellet feed production by providing extended real-time information of the process, making it a useful tool for improvement of the operational strategies and process stability.

Aug 24, 2022

At Cliffs Natural Resources Ltd (CNR) crushing and shipping sample stations, precisions are estimated for the sampling, preparation and measurement stages of iron ore sampling in accordance with ISO 3085 (2002). In this Standard, gross duplicate samples are prepared at each of the three stages, yielding eight measurement assays. Appropriate calculations of the differences between assay pairs are then made to estimate precision of each stage of sampling. The International Standard for checking precision in iron ore sampling, ISO 3085 (2002) prescribes a method for identifying outliers that is ambiguous and possibly inappropriate. The procedure also makes an unnecessary implicit assumption, that the differences between assay pairs are normally distributed. The Anderson-Darling statistic is used to demonstrate that in some cases the assay pair differences have distributions significantly different from normal. When applied at CNR as specified, the Standard leads to precision estimates well below the expected values, thus overestimating the sampling method's capability and limiting the opportunity for real process improvement. This paper suggests an improved method of estimating sampling, preparation and measurement precision. A bootstrap procedure is used to estimate confidence limits for the calculated precision estimates. The proposed method would be suitable for testing blasthole precision. The discussion is supported by extensive simulation modelling of realistic data.

Mar 1, 2010

A combination of new radiometric age dates, local field relationships and the regional tectonic history indicate that the low sulphidation, fault breccia-hosted, epithermal gold-silver mineralisation at Umuna is related to continental rifting processes rather than subduction induced deformation and magmatism. K-Ar and Ar-Ar age dating of secondary sericite associated with the gold-silver mineralisation indicates that the alteration crystallised between 4.0 and 3.2 Ma, whereas relative age relationships and SHRIMP II U-Pb dating of the abundant Boiou porphyry intrusions on Misima confirm that the calc-alkaline plutonism is significantly older (8.1 f 0.4 Ma) and related to a different tectonothermal event. The Woodlark Basin sea floor spreading centre occurs to the north of Misima and has continued to propagate westwards, into the continental basement of the Papuan Peninsular, since the end of the Miocene. The westernmost tip of sea floor spreading centre is presently to the east of the D'Entrecasteaux Islands but would have been to the east of Misima roughly 4 Ma. Many of the young tectonothermal features in the D'Entrecasteaux Islands (hydrothermal activity and associated epithermal mineralisation, metamorphic core complex exhumation, detachment faulting, peralkaline volcanism, half graben type basin formation) can be attributed to major extensional deformation ahead of the propagating rift system. Similar tectonothermal features on Misima are temporally associated with the epithermal gold-silver mineralisation at Umuna, suggesting that the D'Entrecasteaux Islands are a modern day tectonic analogue for Misima at the time of precious metal mobility and deposition. The rapid exhumation of high grade metamorphic rocks and localised

Jan 1, 1997

By G Lane

This paper discusses the factors that contribute to the cost effective design of a concentrator. Concentrator design and layout outcomes are functions of the team (engineer’s and owner’s) participating in each particular project. The benchmark for relatively modest projects was set in the 1980s and 1990s during the ‘gold boom’ when numerous cost effective plants were designed and constructed on a lump sum basis in a very competitive market. A number of factors contribute to lack of transference of the lessons learnt in gold plant design to concentrator design including established paradigms in the design and layout of concentrators, lack of experience in cost effective design, operator’s preferences for flowsheet and layout and simple lack of appreciation of the impact of plant footprint on materials quantities and resultant capital costs.Experiences with recent copper concentrator projects (both small and large) are used as case studies.

Aug 8, 2011

By D E. Thorp

The mining and concentration operations of New Zealand Steel have been carried out initially from the Waikato North Head (WNH) deposit since 1969 and subsequently from the Taharoa deposit since 1972. Over the years the WNH operation has produced about 1.2 million tonnes of concentrate which has been converted into steel, while total exports to the Japanese Steel Industry from Taharoa reached five million tonnes in February of this year. Recent expansion plans both in domestic steel production and in the ironsand concentrate export market have made it necessary for the company to look closely at, among other areas, the mineral processing of the titaniferous ironsands in both deposits. This paper deals with the recent test work carried out at WNH and Taharoa on the use of the cone concentrator unit as a primary gravity concentrating unit ahead of the magnetic separation stages and as a cleaner concentrator following the primary magnetic separation.

Jan 1, 1977

By G Malherbe, J Gonzalez, D C. Franklin, J Bassan, C T. Farrelly

To respond to ever-increasing challenges, mining companies have been experimenting with new business models and technologies in order to speed mine development, production, processing and transport. The various experiments involve mobile access to data, intelligent sensors, advanced analytics, virtual collaboration, virtual reality, automated equipment, remote operations centres and strategic partnerships. A synthesis of all these components creates a ænetwork effectÆ that can dramatically improve the overall effectiveness the entire operation. The concept of the Network Centric Mine borrows from a variety of industries, including defence, aerospace, aviation, petroleum, utilities and manufacturing. Central to the concept are improvements to the way we connect people, process, information and technology, resulting in a more highly collaborative business model, with roles and processes designed to take advantage of new technology. The components of the mining operation act as a connected network aimed at a common goal, regardless of the boundaries of organisation and location.The design of this new organisational ecosystem needs to take into account the recent advances that enable the æplug and playÆ integrated collaborative environment, including cloud computing, mobile devices and social networking, as well as advances in augmented reality, robotics, geo-location, digital labelling, simulation and analytics. However, the most consistent lesson from other industries is the need to properly enable the behaviour and process changes necessary for success.Benefits from adopting a network centric approach include the more effective use of scarce expertise, improved data and information analysis, reduced process variance, and more informed and faster decision-making. The future of mining will see more technology savvy workers who will drive the adoption of new processes. The operations will shift from a relatively static and disparate set of functions, to a digitally aware, dynamic, automated, integrated and interactive environment, with increased agility, lower operating costs, higher productivity and improved safety.CITATION:Farrelly, C T, Malherbe, G, Gonzalez, J, Bassan, J and Franklin, D C, 2012. The network centric mine, in Proceedings International Mine Management 2012, pp 143-160 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 20, 2012

By M Vendrup, T C. Christensen, C Dube

The adsorptive and granulate forming MetClean™ process has been used at many locations in Northern Sweden, Norway, Denmark, France, Spain, Mongolia, Japan and Australia. It has been pilot tested and used in full scale treatment plants to remove metals from:mine watersleachate from solid waste in incineration flue gasleachate from fly ash damsleachate from landfill and waste ponds.The following paper provides details of pilot and plants tests on the effectiveness of MetClean™ in removing arsenic, antimony, barium, cadmium, copper, molybdenum, nickel, radium, uranium, vanadium and zinc. Results show that MetClean™ may reduce the concentration of these metals in treated effluent water to the one part per billion (ppb) range.The paper also finds that, for specific metals, the optimal adsorption condition depends on the:pH levelmolar relation between the specific targeted metal and the addition of iron (II) or manganese (II)type of oxidation agentssalinity levelpresence of other metals.The most effective pH level varies according to the targeted metal but falls within the pH 5 to pH 11 range. A compromise pH level may be set when more than one metal is targeted for removal at the same time and through only one process step. The removal efficiency of one or both metals may be affected by operating at a compromise rather than optimum pH level.The MetClean process generates non-hazardous solid waste. Waste can then be disposed of more easily than brine or sludge.CITATION:Christensen, T C, Vendrup, M and Dube, C, 2015. Pilot tests for heavy metals removal in mine water, in Proceedings MetPlant 2015, pp 404–415 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 7, 2015

By A H. Bagherieh, S Mesroghli, H Jorjani, S Chehreh Chelgani

The rare earth elements (REEs) assay and recovery in leaching processes is being determined using expensive analytical methods, ICP-AES, and ICP-MS. This paper presents a neural network model to predict the effects of operational variables on the lanthanum, cerium, yttrium, neodymium recovery in the leaching of apatite concentrate. The effects of leaching times: ten to 40 min, pulp densities: 30 to 50 per cent, acid concentrations: 20 to 60 per cent and agitation rates: 100 to 200 rpm were investigated and optimised on REEs recovery in laboratory at a leaching temperature of 60¦C. The obtained data, on the laboratory optimisation process were used for training and testing of a neural network. A feed-forward artificial neural network with 4-5-5-1 arrangement, was capable of estimating the REEs leaching recovery. Neural network predicted values were in good agreement with the experimental results. The correlations of R = 1 in training stages, and R =  0.971, 0.952, 0.985 and 0.98 in testing stages were results for Ce, Nd, La and Y recovery predictions respectively and that theses values are considerably acceptable. It was shown that the proposed neural network model accurately reproduces all the effects of operation variables, and can be used in the simulation of a REEs leaching plant.

Jan 1, 2008

By J Dyt, S Lyons

In the mining industry, crusher-related incidents have led to 15 reported deaths in Australia, New Zealand, and the USA between 1998 and 2007 (NSW Government Resources Regulator, 2024). The majority of these fatalities occurred during routine crusher maintenance tasks. A survey of quarry and mine site maintenance staff was completed to ascertain what they thought of such safety device to understand if beneficial and if so reasons if unused. Overall, findings show, staff perceived risks differently, cost, familiarity, device awareness and not front of mind, influenced adoption. This underscores the importance of asking the right questions involving maintenance and safety staff to lead to more proactive risk assessment.

Apr 16, 2024