Search Documents

By P B. Hills

Increasingly over the past couple of decades, the importance of understanding the in situ stress regime in underground hard rock mines has become accepted by all. Providers have responded to this requirement and various techniques for undertaking the measurements have been honed while others have slipped from use. It is a simple, though not inexpensive task to engage a provider to undertake the require measurements, and a comprehensive report will ensue. So, what has actually been obtained? What should the geotechnical engineer do next? What tools are necessary to do so? Regardless of the method of measurement, the report will describe the location of the measurement site and describe the basis of the methodology used in undertaking the measurements and a log of the measurement program. Finally, it will include the results, which should incorporate the normal and shear stress components of the full stress tensor. Ground control management plans (GCMP’s) and stress summary reports and spreadsheets prepared by site geotechnical engineers always include the magnitude, trend and plunge of the principal stresses. Remarkably few site-based summaries include the full stress tensor. This is a significant gap as the full stress tensor is vital for any further data manipulation. However, without the algebraic tools to undertake those manipulations, their value is diminished. This paper seeks to provide a checklist of ideas to be considered. It provides commentary on the options available to dissect the stress measurement report and ensure that the maximum possible value is derived from it. The manipulation and presentation of component stress data is also discussed. The various methods of stress measurement are not the focus of the paper but some of the strengths and weaknesses of them over which the site geotechnical engineer has some control, are highlighted.

Nov 29, 2022

By N Anderson

The world-class Golden Mile gold deposit in the Eastern Goldfields of Western Australia is part of the Kalgoorlie Consolidated Gold Mines (KCGM) operation, which is wholly owned by Northern Star Resources Limited. Current mining operations across the Golden Mile is dominated by the large Fimiston Open Pit, which is over 4 km long, 1 km wide and 600 m deep. It is part of a larger mineralised system that stretches over 8 km and includes the Mt Charlotte Underground Mine, which is also operated by KCGM, as well as numerous historical open pit and underground mines. This mineralised system has been continuously mined for over 125 years and is set to continue well into the future. The Golden Mile deposit is in the Norseman Wiluna Greenstone Belt which is made up of a series of mafic volcanic and sedimentary rocks that have been structurally deformed and intruded by granitic rocks. There are two main styles of mineralisation across the Golden Mile. Firstly, the Fimiston style, which consists of shear hosted Golden Mile lodes with abundant sulfides and tellurides and secondly, the Charlotte style that comprises younger stockwork veins. Fimiston style mineralisation is the primary style of mineralisation within the Fimiston Open Pit. Historically, in excess of 3500 m of underground development and over 755 stopes were mined prior to the consolidation of the area and the commencement of Fimiston Open Pit operation. Old underground workings, known as voids, are either empty or backfilled and extend to more than 1.2 km below surface. Although they are a routine part of mining operations at KCGM, voids pose a significant challenge for the geology team in terms of planning and executing exploration and grade control drilling, geological modelling, grade and tonnage estimation, drill and blast design and execution, marking up ore block designs, mining, and reconciliation. This paper will discuss the various challenges faced by the geology team due to the presence of voids, solutions used to overcome some of these challenges and the results of these activities.

Mar 22, 2022

By E Macmillan

For any processing plant there will be deleterious elements or minerals which affect production or quality, and a strategy to predict their occurrence and mitigate their impact is required. An early objective of the Olympic Dam geometallurgy program was prediction of the acid consumption and gelling behaviour of the ore, which affects leach recovery, throughput and circuit availability. The geometallurgical test program measured the response of a wide range of ore types, and then relationships between mineralogy, metallurgy and chemistry were developed. Thus the drivers of acid consumption and triggers for gelling events could be described in ways that were meaningful to plant operations.To enable optimisation of the mine planning and ore blending processes, the parameters driving metallurgical response must be translated to the block model. Data support is critical in populating a block model. Assay information is easily obtained, but mineralogical and metallurgical information is more expensive and time consuming to collect. Hence population of a block model with mineralogical and metallurgical values using a conventional geostatistical approach is not always possible.An alternative approach employed at Olympic Dam was the development of a suite of assay-to-mineral algorithms. These algorithms were calibrated using all available mineralogical information, and this enabled the calculation of mineral abundances for more than 1.5 million assayed samples. Estimation of the minerals in the block model, and the generation of acid consumption values for each block could subsequently occur.The use of back-calculated mineralogy from assays as part of process model generation is an innovative tool which can be used for mine planning and optimisation and to ensure the plant does not receive any unwelcome surprises. Ultimately, one purpose of geometallurgy is to predict potential processing issues and their drivers so that these can be mitigated. A strategy to achieve this is outlined hereafter.

Sep 5, 2011

Many young mining engineers do not consider consulting as a possible job, believing that many years of working on-site is required to achieve practical experience, develop expertise and acquire industry contacts. However, mining consultancies employ engineers with varying levels of experience, including part-time university students, graduates and engineers who are relatively new to the industry. This paper outlines the role of a young engineer in a large mining consultancy and the benefits to both the consultancy and the client of having a mix of consultants with a diverse range of experience. From the authorÆs perspective, the work experience, lifestyle and rewards of mine consulting are compared to site based work, including a discussion on whether consulting is able to offer the professional development that a young engineer needs.

Jan 1, 2009

By E Niva

The IsaMillÖ is challenging the way that plants are designed and operated. This paper challenges existing designs of concentrator flow sheets, particularly focusing on magnetite circuits.   From what has started out as a small scale ultra fine grinding mill in the pharmaceutical and pigment industries, it has been redesigned and improved upon for mineral processing, and has been the mainstay of fine grinding applications for over ten years. These applications have required energy efficient grinding to succeed, and have been predominately in the base metals industry.   Further development of the IsaMillÖ has now resulted in the machines being able to treat larger tonnages, with higher capacity motors. This development, along with the introduction of purpose designed ceramic media, has allowed the mill to treat courser feed sizes. At the same time, the mill still offers highly efficient grinding, and has enabled it to be operated in coarser tertiary and secondary grinding applications.   The acceptance of the mill in coarser applications, predominately in base metals and PGM applications, has enabled the IsaMillÖ to be a serious contender for beneficiation in other minerals. One such application is the potential for IsaMillsÖ to be part of magnetite flow sheets, which are being considered in Australia to meet the growing iron demand of China. The high energy efficiency of the IsaMillÖ compared to conventional technologies, as well as the smaller infrastructure requirements, provides a great opportunity to reduce the power intensity of magnetite circuits.   This paper will examine the use of IsaMillÖ technology in conventional grinding applications, including recent testwork in a primary grinding base metal circuit, as well as testwork on magnetite ore comparing a lab scale IsaMillÖ with a lab scale Tower Mill.   The growing demand for minerals over the next decade, coupled with higher energy cost, will result in energy efficient technology, such as the IsaMillÖ, being included in standard circuit design.

Jan 1, 2008

By C McCracken, R Landers, B Hesse

Minnovare identified the potential to improve production drilling outcomes in underground long-hole stopes through the adaptation of new technology which was under ongoing development. An approach to Evolution Mining resulted in the companies agreeing to a collaborative agreement to further develop the technology for use on underground long-hole drilling equipment. During a period of six months in FY2018, a series of trials were conducted to compare drilling accuracy using two different methodologies and the subsequent impact this had on ore dilution. Testing was conducted at Cracow underground gold mine in Queensland, Australia. The drill rig’s existing setup/alignment process was compared to the new technology system with the following observations: • Using the existing process only 20% of holes surveyed recorded toe points within the +/ 300mm (11.8in) tolerance blast-hole deviation. • The new technology was proven to limit rig setup/alignment error, reducing average blasthole deviation and increasing the number of holes drilled within tolerance by 160%. The increased accuracy reduced stope dilution by reducing over-break of subgrade ore: • Stopes drilled using the new technology recorded 62.6% less average dilution. • This contributed to an overall reduction in dilution for the full year (FY18) of 5 percentage points compared to FY17 - from 22% to 17% (a net decrease of 22.7%). • With the system implemented as standard practice following results of the FY18 trial and continued success, overall dilution for full year FY19 showed continued reduction to 12% Evolution has continued use of the new technology at Cracow, where the improved accuracy has allowed the extraction of narrower stopes where drilling accuracy is critical. Evolution has also deployed the technology at the Mungari operation and has stipulated that the contractor use the technology at the Mt Carlton operation, which is currently under development. Future implementation of the Development Optimiser system should be verified by commencing additional trials to include a larger data base for validating the initial trial results.

Mar 15, 2021

By K Smith

This paper presents an assessment of the Robertson (2010a) method within the CPTu inversion parameter framework of Been et al. (1987), using CPTu calibration chamber data presented by Jefferies and Been (2015) and in other literature to assess the validity of the method, with particular focus on applicability of the method to TSFs (i.e. its applicability to loose silts and silty sands). The assessment demonstrates that although the method estimates values of k consistent with calibration chamber data, the method estimates values of m that are generally 1.5 to 2 times greater than calibration chamber data. As a result of this, the method generally overestimates Ψ for values of Ψ less than 0, and underestimates Ψ for values of Ψ greater than 0. This may result in both overly conservative assessment of materials as potentially liquefiable and unconservative predictions of material behaviour for loose materials.

Jul 1, 2021

By A Esfahanipour, M Osanloo

Determination of cut-off grade?strategy is one of the most important stages of open pit mine planning and design. It is the parameter directly influencing the financial, technical, economic, legal, environmental, social and political issues in relation to mining operation. Choosing the optimum cut-off grade strategy that maximises the economic outcome has been a major topic of research workers for nearly one century. Many researchers have contributed in devising methods and algorithms, such as dynamic programming, linear programming, optimal control and so on for various aspects of its determination. In this paper, a non-linear mathematical programming for cut-off grade strategy optimisation is presented, considering the three main stages of mining operation introduced by K F Lane. In this model maximisation of net present value of mining operation, under the three constraints of mining stagesÆ capacities, considered as the optimisation criteria. Due to the discrete representation of the mining resource, the proposed non-linear formulation is approximated by a non-linear signomial geometric programming. According to non-convexity and the complexity of the proposed model, an augmented Lagrangian genetic algorithm was used to find the optimum cut-off grade strategy under varying and fixed price circumstances. To validate the proposed non-linear model efficiency, the results were compared with the results obtained by the K F Lane methodology. It was found that the proposed non-linear model works efficiently in the determination of cut-off grade strategy. According to the simplicity of the structure of non-linear programming modelling in comparison with dynamic programming it is hoped that, further development of this model would certainly provide the ability of considering managerial and technical flexibilities as well as incorporating more real mining conditions in the determination of cut-off grade strategy optimisation.

Sep 26, 2011

Resue or split face firing has the potential to separate ore and waste rock into separate muck piles within a stope. Thus split face firing has the potential to reduce dilution of the ore stream to be transported to the surface for subsequent processing. It also potentially reduces the total amount of broken rock needing to be transported out of the mine as the waste material is physically separated from the ore as part of the blasting process. Waste can therefore be used directly from the stope to backfi ll other mining areas. This paper reports on the results of split face firing trials at the Hillgrove mine in NSW and analyses the results of these blasts.

Aug 1, 2010

By P Mulvey, M Stuckey

"Inter-aquifer leakage due to fractures caused by coal seam gas extractions or longwall mining is an important issue for both the gas and coal industries. Currently, predicting stress induced macro-porosity associated with hydraulic fracturing, depressurisation via dewatering or collapse of overlying seams to infill a void left by longwall mining, is problematic. If fractures can be located the fracture can be sealed. Locating fractures is difficult. The non-geophysical approaches to locate fractures has been to consider the mixing of different waters, particularly that of more recent shallower groundwater with older deeper groundwater, via differences in radio-isotopes integrated with geochemical models to predict likely mixing of waters. This approach is applicable under appropriately complex settings; however, it is an expensive technique and is based on the assumption that the daughter isotopes are equally non-reactive which may not always be the case.Potentially a cheaper and faster technique is to consider integrating geochemistry (mineral weathering) and hydrogeology. The chemistry of groundwater, controlled by the weathering of primary rock?minerals and?formation of secondary minerals, can not only be differentiated between geological strata but also within strata as different stages in weathering results in differing impacts on water quality (ie different reactants).Field analysis of pH, electrolytic conductivity (EC), oxidation reduction potential (ORP) and dissolved carbon dioxide together with laboratory analysis of dissolved constituents characterise the chemistry of the water. Collection of rock samples at the time of drilling for bore installation can provide the (only) opportunity to assess the media in which the groundwater resides and migrates through. An assessment of aquifer matrix chemical makeup, via bulk sample chemical analysis, X-ray diffraction (XRD) and petrographic analysis can achieve this.The chemistry of groundwater is dependent on the water velocity. Water at deposition and post-diagenesis dissolution of minerals by hydrolysis and oxidation will result in equilibria of the dissolved phase with the solid phase. Post-depositional fractures caused by either tectonic activity or weathering alter the rate of weathering and thereby the geochemistry. Slow water flow in microfractures results in water in equilibrium with the rock minerals. Faster flow in larger fractures results in water being in disequilibria with rock minerals.Fractures can alter groundwater chemistry by two pathways: changing groundwater velocity, which changes the rate of hydrolysis or oxidation mixing water from different geological strata.Both pathways cause subtle changes in the water chemistry.It is however, the dissolved phase chemical data, which can be observed over time at individual locations and/or at a point in time along a flow path, which allows the hydrogeologist to ælook up-gradientÆ and locate the zone of leakage. Hence, influences on rock/groundwater chemistry, from anthropogenic sources to natural mixing of waters, can be assessed via appropriate interpretation of geochemistry, hydrogeochemistry and flow data.This paper will use the example of the geochemical and hydrogeological characterisation of aquifers within the Hawkesbury and Bulgo Sandstone of the Southern Coalfields to the south of Sydney in New South Wales to demonstrate this approach.CITATION:Stuckey, M and Mulvey, P, 2013. Looking for fractures - integrating geochemistry with hydrogeology to find inter-aquifer leakage above dewatered or collapsed coal seams, in Proceedings Water in Mining 2013, pp 99-108 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Nov 26, 2013

By K Ehrig, C Lower, V Liebezeit, M Smith, E Macmillan

"Minerals, minerals, minerals. Elements occur in the earth as minerals. If local physical, chemical and structural conditions are conducive to concentrating these minerals to sufficiently high abundances in the earth’s crust, a mineral deposit will form. If technology is available to extract metals from the minerals economically, then you have a mineral resource that will be mined and processed. Determining which minerals are present and quantifying their abundances, textural characteristics (grain size and shape) and how they are intergrown with each other is the realm of the mineralogist. Geologists use this mineralogical data to understand how the mineral deposit formed, how to find high-grade zones within the deposit and where to find other mineral deposits. Metallurgists use this data to design, operate and optimise processing facilities to extract metals from the minerals. The types, quantity and precision/resolution of the mineralogical data required by geologists and metallurgists are different, but are not mutually exclusive of each other. Fortunately, measurement technology is available that is relatively rapid, high volume and low cost, thus enabling ore and gangue mineral characterisation at a historically unprecedented scale of a mineral resource.CITATION:Ehrig, K, Liebezeit, V, Smith, M, Macmillan, E and Lower, C, 2014. Geologists and the value chain – how material characterisation by modern mineralogy can optimise design and operation of processing facilities, in Proceedings Ninth International Mining Geology Conference 2014, pp 5–14 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Aug 18, 2014

The Imperial Smelting Process (ISP) for the simultaneous smelting of zinc and lead was developed at Avonmouth from the 1930's with activity intensifying in the late 1940's/early 1950's. Present operations are based around the No.4 furnace which was built in 1967. Development during the 1980's has been driven by the need to sustain operations at low metals prices and has been aimed at reducing manning whilst increasing output. Although hit by several major plant disruptions, progress has been steady, culminating in a ú10 million capital programme in 1988?89 to upgrade the operation. The most important technical developments, reflecting the needs of the 1990's have, in the sintering area, included improvements to feed conditioning and sinter quality, a 20% uprate in production capacity by debottlenecking, and pilot work leading to the installation of a Boliden-Norzink mercury removal plant. In the smelting area the ISP furnace has been rebuilt, with a redesigned bottom section to eliminate earlier operating sensitivities, and to achieve higher blowing capability, and at the zinc refinery the columns have been rearranged for more flexible operation and higher capacity.

Jan 1, 1989

By T M. Brettell, D Sidea

The CSA Mine is located in Cobar, New South Wales and is operated by Glencore. Large scale underground production started from 1965, with zinc, lead, silver and copper extracted in the past. The current operations focus on copper, with a silver co-product.From 2014 to 2016, Cobar Management Pty Ltd (CMPL) undertook a major capital project to upgrade the primary ventilation system at the CSA Mine. This involved the development of ten raises using full-face raise boring from surface to a depth of 1450 m. The total length of the raises was approximately 2500 m. Geotechnical conditions were identified as a key project risk during the early planning stages of the project. Timely quantification of the geotechnical risks was required to minimise project delays and cost overruns. Geotechnical investigations were planned and conducted for each raise prior to pilot drilling and full-face back reaming.Nine of the ten raises had final wall camera and laser baseline surveys completed following full-face reaming. The surveys were conducted progressively, allowing ongoing back analysis and calibration of geotechnical evaluations as the project advanced.This paper presents the design and planning process of the raise bored excavations. It details the geotechnical investigation work undertaken to mitigate the geotechnical risks and the challenges and learnings from the project including the benefits of close collaboration between the parties involved.CITATION:Sidea, D and Brettell, T M, 2017. The CSA ventilation upgrade – geotechnical challenges and learnings, in Proceedings 13th AusIMM Underground Operators’ Conference 2017, pp 341–352 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 16, 2017

By R Carstens, L Munsamy, L Prinsloo, C Huang, C Zhang, R Liang, I Canbulat

With recent advances in machine learning, data-based automated decision-making has been proven successful with promising outcomes in many industries. Its application in the mining sector can be ground-breaking; particularly the data-driven analytics that can support decision-making in the mine and consequently enhance mine safety, efficiency and sustainability. However, the current data science applications in the mining industry are mostly noncomprehensive, especially inadequate in evaluations, thus often requiring further study to be potentially beneficial to operations. Furthermore, it was found that existing literature paid limited attention to understanding the role of such techniques. Hence, in this paper we aim to build an end-to-end machine learning powered data-driven framework for intelligent geo-hazard analytics to support decision-making for underground mining data management, where multiple types of data are managed in an integrated database to support the unified machine-learning model. Here we present the framework as data-driven workflow processes, including data gathering, data preparation, data processing and data presentation. In addition, we present an application scenario of the proposed framework, where falls of ground (FoG) is managed with the historical FoG investigation reports, related panel hazard ratings, compliance data and rock mass characteristics. A demonstration can be dynamic forecasting of high-risk areas for FoG based on both spatial and temporal factors, including a 3D data visualisation. Such a scenario shows the potential of the proposed framework to establish connections among various data fields across a diverse category of data. Furthermore, the results offer important insights for ground instability management and can potentially optimise the underground operation flow.

Nov 29, 2022

In dense medium processes for the beneficiation of minerals the consumption of medium (generally ferrosilicon) represents a major component of the operating cost. This provides a strong incentive for improvements in heavy medium recovery circuit design and operation. A major thrust in heavy medium plant design over the past decade has therefore been towards circuits which reduce medium losses. In this paper recent trends in plant design are examined in relation to the factors infl uencing circuit performance and medium losses. Operational details ' which have a significant effect on losses are discussed and illustrated by means of plant and pilot plant test data, with particular emphasis on the performance of wet drum magnetic separators. While the emphasis is on reducing the consumption of the high-cost ferrosilicon medium used in minerals beneficiation, most of the principles described in this paper are equally relevant to the design and operation of magnetite recovery circuits for coal preparation plants.

Jan 1, 1987

By D A. Sketchley

The Merlin Zone, a 2008 high-grade Mo-Re discovery, is a part of the Mount Dore Deposit in the Eastern Succession of the Mount Isa Inlier in Queensland, Australia. Hosted by carbonaceous metapelites and phyllites, the Merlin mineralisation comprises molybdenite veins, breccia infillings, stylolitic fracture fillings, and disseminations. Because rhenium is geochemically similar to molybdenum and commonly associated with it, global production of rhenium has been mostly a by-product of molybdenum refining. The high-grade rhenium in the Merlin Zone is an exciting discovery that is expected to become a direct source of rhenium. At the time of discovery, quality assurance (QA) procedures for rhenium were not in place at the Merlin Zone; therefore, they needed to be developed.The Merlin Zone was discovered using reverse circulation drilling, which led to concerns about molybdenite loss due to poor sample recovery. The twinning of the discovery hole with diamond core demonstrated a two-fold increase in molybdenum grade over several tens of metres. Consequently, the resources of the Merlin Zone were defined using assays from diamond drill core.Early analytical work, which was initially done only for molybdenum, comprised geochemical analysis with an aqua regia digestion, which have poor precision and can be biased low. Although initial testing for rhenium used similar procedures to those for molybdenum, a scarcity of commercial rhenium reference materials led to a validation process using neutron activation analyses and different digestions. This resulted in introduction of four-acid digestion assays, development of matrix-matched reference materials, and improvements to the quality of molybdenum and rhenium assays for reporting resources. Coarse and pulp duplicates were used to check for sampling bias and to ensure that levels of precision were adequate for the style of mineralisation and analytical methods. In addition, the direct and consistent geochemical correlation between molybdenum and rhenium provided another method for checking analyses.

Aug 22, 2011

By T Barto, D Thomson, T Norgate, C Doblin

Collaboration between CSIRO Minerals and SunSalt Pty Ltd, a salt producing company located in rural Victoria, has resulted in a commercial process to recover magnesium sulfate (commonly called Epsom salt) from the saline waters of the Murray Basin. The feed for this process is bittern; the liquor remaining after halite (common salt) has been harvested from the saline water by evaporation.SunSalt produces salt and bitterns from three locations, namely Hattah (Victoria), Mourquong (NSW) and Wakool (NSW). The small size and considerable distances between these operations makes it uneconomic to build a stationary processing plant to extract value-added products, in particular Epsom salt, from the bitterns of the three operations. This fact led SunSalt to build a containerised mobile plant that could be moved to each site to process the bitterns at the end of the salt harvesting period.Epsom salt is extracted from the bittern by further evaporation, refrigeration and recrystallisation. In this process the bittern is diluted with five per cent volume of fresh water to minimise precipitation of residual halite in the bittern. Cooling the diluted bittern to between -5 and -10¦C precipitates up to 70 per cent of the magnesium sulfate, which is recovered as 85 to 96 per cent purity Epsom salt by filtration. This product is marketed as an industrial grade Epsom salt. Higher purity (up to 99.9 per cent) Epsom salt (USP or BP grade refined product) is made from the industrial grade product (raw Epsom salt) by recrystallisation.The containerised mobile plant was commissioned in December 2002. The raw Epsom salt generated in the mobile plant is refined to a higher purity Epsom salt in a separate plant located in Mildura. The Mildura plant was commissioned in December 2003.The CSIRO-SunSalt collaboration has demonstrated that the saline waters can be processed into a useful resource, and in addition could create jobs and a new skill base in regional Australia. The production of Epsom salt locally in Australia, which is worth currently about $A600 per tonne, removes the need to import over 3000 tpa from overseas with a net positive impact of $A2 million on the balance of trade.

Jan 1, 2004

By P Klaric

Drive stability is critical in block/panel cave mining. The production levels of these mines are required to remain operational for the entire life-of-mine which can be in excess of 30 years. It is therefore necessary to produce high-quality drives to ensure sustainable mine productivity. In order to improve the quality of drives and pillars, this gold mine instigated a project to optimise their development blasting. The initial aim was to reduce the level of overbreak in development mining, which was averaging approximately 18 per cent. The benefits of controlling overbreak not only included an increase in the integrity of the drives but also a decrease in load and haul and ground support costs. Through focusing on the optimal blasting of the perimeter holes, overbreak was reduced to 4.5 per cent. The project’s focus then moved to drill and charge designs for development faces. In optimising these designs, it was anticipated that improvements in the development mining cycle would be achievable.CITATION:Klaric, P, 2015. Improving drive stability through efficient development blasting design and practices, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 327–332 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By J Deraisme, P Epinoux, O Bertoli

"Société le Nickel exploits the Dôme lateritic nickel orebody at its Tiébaghi operations in New Caledonia. The site geology has an obvious bearing on recovery and metallurgical performance, with controls that are extremely complex at all scales, including lithology, oxydo-reduction conditions, mineralogy and multivariate geochemistry. In this context, establishing an adapted recoverable resource estimation method that is efficient and transparent proves an interesting challenge. The method must address the key notions of: support effect – the exploration data set can only warrant the estimation of large panels of 20 × 20 × 3 m3 that are much larger than the selective mining units (SMUs) of 5 × 5 × 3 m3 information effect – the selection at the production stage uses estimates based on information that is much denser than that available for mine planning.The problem is rendered more complex in this type of deposit by the fact that the additive variables used for the estimation (metal accumulation and ore tonnage) are not the ones used to establish the selection at the mining stage (ie the nickel grade of SMUs, which is the ratio of accumulation on tonnage). Eventually, the selection criteria not only involve Ni grades, but also other elements such as Al2O3, Fe2O3, MgO and SiO2.The solution presented in this paper is to construct an SMU multivariate simulation in the saprolitic horizon and construct an efficient post-processing aimed at producing multivariate recoverable resource estimates. The efficiency constraints imposed by the number of blocks to be simulated (1.5 million) lead to resorting to direct block simulations. The underlying multivariate discrete Gaussian model, which had its validity tested beforehand, is put to good use to mimic the selection process that happens at the mining stage by offering the ability to simulate a composite value located at random within each block.The paper also presents the application of a scenario reduction algorithm to pick a representative subset of a few simulations to help appraise the risk attached to the downstream (reserve optimisation and mine sequencing) phases of the project. The original version of the paper (see Deraisme, Bertoli and Epinoux, 2014) used an early version of the scenario reduction plug-in (named S2RM) built in Isatis® software, where measuring the distance between the initial set of scenarios and the reduced set was based on Ni only. The implementation presented here is for the second generation of S2RM, where measuring the distance between the initial and the reduced set of realisations is based on all study variables. The benefits of the measure adapted to the true multivariate nature of the problem are highlighted in this updated version of the paper.CITATION:Bertoli, O, Deraisme, J and Epinoux, P, 2014. Multivariate block simulations of a lateritic-type nickel deposit and post-processing of a representative subset, in Proceedings Orebody Modelling and Strategic Mine Planning Symposium 2014, pp 99–108 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Nov 24, 2014

By Johnston RRM

There have been many published mathematical models that, to varying degrees of sophistication, attempt to describe dynamic thickener behaviour. CSIRO has undertaken to develop a model under industry sponsorship. Recently developed instruments such as the floc density analyser and natural gamma-ray gauge have enabled new data to be collected from plant thickeners for model validation and development. The principles behind the use of the natural gamma-ray gauge are described and the possibilities for its use as a control instrument in the bed have been examined. A simple nomograph illustrates how the gamma-ray gauge data can be used to predict steady state underflow consistency and bed Position.

Jan 1, 1991