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By A Muhairini, M Eggers, J Smith, H Baxter

Detailed geochemical analysis of cored and non-cored drill hole data was used to characterise and model the Cenozoic detrital valleys of several deposits within the southern Pilbara region, Western Australia. The purpose of this modelling was to better characterise and understand the relationships between the various geotechnical units comprising mixtures of rock and soil for the purposes of slope stability and depressurisation studies.This paper presents data from several valleys where geological, geomorphological and climatic processes have resulted in the deposition of heterogeneous detrital rock and soil sequences. Seven primary detrital units are recognised as occurring within all the valleys studied, suggesting that the geological processes involved in the erosion and deposition of the units were widespread. Geochemical assessment of cored and non-cored data suggests correlatable geochemical signatures can be recognised for each of the units; however, local variability in the groundwater history of individual valleys is demonstrated by late-stage carbonate precipitation recognised both in the core and through the geochemical signatures, which has resulted in alteration of the parent rock/soil material. This paper discusses how the carbonate alteration may lead to improvements in rock/soil mass strength of a clay unit by comparing laboratory strength test samples of the same parent material with varying degrees of precipitate alteration to those with no discernible carbonate alteration. Following from this, correlations with geochemical assay results have been derived, whereby zones of more favourable strength conditions may be modelled through assessing areas of analogous geochemistry.The paper demonstrates how geochemical assessment can lead to improved geotechnical and hydrological modelling for a detrital valley system without the need for significant coring and laboratory testing. This in turn leads to improved confidence in the slope design and depressurisation recommendations for a slope.CITATION:Baxter, H, Eggers, M, Muhairini, A and Smith, J, 2015. The effect of carbonate alteration on detrital mass strength and implications for geotechnical slope design, in Proceedings Iron Ore 2015, pp 429–436 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By E Villaescusa, A Kusui, R Talebi, R Hassell, C Arcaro

Northern Star Resources (NSR) operates several seismically active mines as part of its Kalgoorlie Operations. In order to successfully continue mining at depth in increasing stress conditions, strategies need to be developed to reduce, control and manage the impact of seismicity causing damage to the rock mass. Consequently, a research partnership was developed with the WA School of Mines (WASM) through Mining3. The main aim of the project was to develop appropriate ground support standards that could withstand the expected dynamic response with minimal to no rehabilitation required for the life of that excavation. The project utilised a design methodology for determining the required energy demand based on detailed geotechnical mapping, probabilistic analysis of wedge formation and an estimate of rock ejection velocity based on uniaxial compressive strength of the intact rock (Villaescusa et al. 2016). The ground support scheme consists of high tensile chain link mesh, resin encapsulated de-coupled posimix bolts and plain strand cable bolts, in one, or multiple passes together with plain shotcrete. Implementation of the design posed several challenges including how to install the chain link mesh, maintaining the required productivity, ensuring quality control, and understanding the interaction of the several ground support components within the scheme. The implementation of the system within a trial area was successful from development mining to open stope extraction. The most significant field verification of the system occurred with near field M+1.9 seismic occurring in proximity to an operating long-hole drill. Despite large displacements exceeding 0.5m in places, there was no significant ejection of rock or failure of the ground support system. Following the successful trial, the ground support design methodology and standards have been implemented across several NSR sites. The system forms the basis for the successful extraction of resources in future high seismic risk areas.

Mar 15, 2021

By Rolfe PR, Ellis BA, Clements RJ

Associated Minerals Consolidated Limited (AMC) is constructing a 112,500 tonne/yr synthetic rutile plant at Narngulu, near Geraldton in Western Australia. Design of the plant is based on the technology developed by AMC and utilised in its two existing plants at Capel in Western Australia. Ilmenite Feedstock for the plant will be sourced from AMC's mine at Eneabba and coal obtained from the Collie deposits. The plant is scheduled to come on stream in the second quarter of calendar 1987. The rationale of the decision to construct the Narngulu plant is examined against the background of the world market for high-Ti02 content feedstocks. Also provided is a detailed description of the plant and an examination of the technology used in process Design.

Jan 1, 1986

By I Canbulat, J Oh, A Mcquillan, D Payne

This paper presents a new risk assessment tool for coal mine excavated slopes. This new empirical-statistical Slope Stability Assessment Methodology (SSAM) is intended for use by geotechnical engineers at both the design review and operational stages of a mine’s life to categorise the risk of an excavated coal mine slope. A likelihood of failure is determined using a new slope stability classification system for excavated coal mine slopes developed using a database of 119 intact and failed case studies sourced from open cut coal mines in Australia. Consequence of failure is based on slope height and stand-off distance at the toe of the excavated slope. Results are presented in a new risk matrix, with slope risk being divided into low, medium and high categories. The SSAM is put forward as a new risk assessment tool to assess the potential for, and consequence of, excavated coal mine slope failure. Unlike existing classification systems, assumptions about the likely failure mode or mechanism are not required. Instead, the SSAM applies an approach which compares the conditions present within the excavated slope face, with the known past performance of slopes with similar geotechnical and geometrical conditions, to estimate the slope’s propensity for failure. The SSAM is novel in that it considers the depositional history of strata in an excavated slope and how this sequence affects slope stability. It is further novel in that it does not require explicit measurements of intact rock, rock mass and/or defect strength to rapidly calculate a slope’s likelihood of failure and overall risk. Ratings can be determined entirely from visual observations of the excavated slope face. The new SSAM is designed to be used in conjunction with existing slope stability assessment tools. CITATION:Mcquillan, A, Canbulat, I, Payne, D and Oh, J, 2018. New risk assessment method for coal mine excavated slopes, in Proceedings The Fourth Australasian Ground Control in Mining Conference (AusRock), pp 473–495 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 30, 2018

By F Kock, Y Sulianto, T Trott, B G. Putland, D Morgan

"Northparkes installed and commissioned a secondary crushing circuit in 2010 to debottleneck the semi-autogenous grinding (SAG) mill constrained grinding circuits. Following further improvements to the circuit (inclusion of a double deck vibrating screen), the project successfully delivered finer feed to the SAG mill. The result of this project was an increase in the milled tonnes from 5.6 Mt/a in 2012 to 6.0 Mt/a in 2013.The increased throughput rates introduced new challenges with the circuit becoming power limited. How to best optimise the available comminution power, while delivering the optimal particle size to the flotation circuit was made the key optimisation objective. To achieve this objective, Northparkes initiated a project that included engaging comminution experts. Recommendations included changes to the SAG mill including mill lifter design, increased grinding media charge levels and reduced grinding media size with aim of producing a finer grind size.Northparkes implemented these recommendations along with some other changes to SAG discharge grates and the mill discharge vibrating screen. This achieved a substantial reduction in the flotation feed particle size distribution (approximately 20 microns) by utilising increased average SAG power utilisation, in turn resulting in a two per cent increase in copper recovery.With power utilisation now maximised, the next phase of optimisation has moved to the throughput-grind-recovery relationship and the cost benefit analysis of installing additional grinding power.Citation:Sulianto, Y, Trott, T, Morgan, D, Bell, T, Kock, F and Putland, B, 2016. Optimisation of Installed Mill Power Post-installation of Secondary Crushing Circuit at Northparkes Mines, in Proceedings 13th AusIMM Mill Operators’ Conference 2016, pp 331–338 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Oct 10, 2016

By A Huebner, A Noack

Companies all over the world are very sensitive concerning their IT and network security. In most network connected technical installations and machines however, network security is not taken into account to a significant extent: insecure protocols are run, unencrypted information is exchanged freely and even broadcasted wirelessly and networked machines are accessible via insecure file transfer protocol (FTP).What happens in case of malfunctions of such technical installations? Who is responsible? Who can be held liable in case of accidents? The first computer worm for automation systems (æSTUXNETÆ) (Symantec, 2010) was discovered during 2010.The paper is intended to create sensitivity among decision makers for potential security and resulting safety leaks and points out the current status quo in technical network security. It outlines best practices for secure networking and procedures for remote access and remote software updates on stationary equipment and mobile mining machinery. It describes how to ensure authentic and genuine configurations and software targets and how to ensure secure communication for autonomous and remote controlled equipment. For such equipment in particular, the following statement should apply: æThere is no safety without network securityÆ.

Sep 26, 2011

By B J. Hutchison, S Gannon, J Chambers, D Oko-oboh

The Kanmantoo copper mine is located in the Adelaide Hills area of South Australia and is owned and operated by Hillgrove Resources (HGO). The mine is a drill and blast, truck and shovel operation mining sulfide (chalcopyrite) ore located in chloritised andalusite biotite schist. The initial Kanmantoo open pit operation occurred in the 1970s, before falling copper prices closed the mine. In 2010 the mine was reopened by HGO and the Kavanagh cutback of the Kanmantoo pit was undertaken. The Spitfire, Nugent and Emily Star satellite pits were also mined through to 2015 before the latest steep wall Giant pit design was developed to take mining out to 2019.There are no major fault structures and only two significant shear zone structures exposed in the open pit walls. The main Garnet Andalusite Biotite Schist (GABS) unit is quite competent so the pit designs have therefore mainly been controlled by four distinct joint sets. This paper is a case study on the influence of the joint regime on the wall stability of the main GABS unit and how a better understanding of the joint regime and the use of rock reinforcement has allowed the steep wall design to be adopted.The paper also describes the remote geotechnical mapping and slope monitoring techniques used to manage the rockfall risks associated with the steep walled slope design.CITATION:Hutchison, B J, Chambers, J, Gannon, S and Oko-oboh, D, 2017. Case study of joint structure and the design and performance of open pit walls at the Kanmantoo copper mine, in Proceedings Tenth International Mining Geology Conference 2017, pp 355–364 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 20, 2017

By D Tanzil, H Jones

Every mine will close! Charting a profitable course through mine operations to acceptable mine completion requires that risk and opportunity management planning of the mine life begin as early as possible in the life cycle. Management targets and metrics are required to identify and navigate the course to successful mine completion based on economic, social and environmental criteria. This paper outlines the application of The Metrics NavigatorÖ principles to the life cycle of a mine site. In general, metrics are required to make key strategic ideas apparent, transforming those ideas into a manageable set of quantitative measures that guide communication and decision making. For example, the chemical industry has established metrics that focus on the life cycle impacts of its products and eco-efficiency of their processes. Other industry sectors have focused attention on workplace and community well-being outcomes. These management metrics are necessarily organisation-specific, aligned to stakeholdersÆ expectations and the strategic outcomes sought, as well as the cause-and-effect relationships underlying key issues. Recently, the Global Environmental Management Initiative (GEMI), a consortium of multi-national companies, developed The Metrics NavigatorÖ. The guidance document provides a structured process for assessing and developing metrics for key environmental, social, and economic issues based on business and stakeholder perspectives. It incorporates best practices learned from the chemical and other industry sectors and has since been applied to develop metrics that guide life cycle strategies. The paper examines how the life cycle of a mine site could benefit from experiences in other industry sectors where sustainability metrics have guided strategy. It considers the potential application of The Metrics NavigatorÖ process to the life cycle of a hypothetical Australian mine site using the processes that have been successful in other industry sectors.

Jan 1, 2009

By B Broad

"Establishing ventilation in the early stages of a new mine is an essential step to achieve scheduled outcomes that ultimately drive the financial success of an operation. If the primary ventilation is not in place in time to support a contractorÆs work output, then the ore delivery is likely to be severely impacted. Options to increase ventilation in order to address shortfalls are limited. This in turn can lead to reduced revenue generation at a time when a mine is at its highest capital outlay. This can have implications for any company, but even more for an explorer moving to producer. The ventilation put in place to cover the start-up period is also unlikely to cover any extended or increased load required to meet schedule delays.The following paper examines two issues in relation to ventilation with a focus on small to medium projects where the company is establishing a mine using a mining contractor. The issues being: potential impacts on the contract and tender process when using a mining contractor key mine design considerations, such as æcrunch timeÆ, as they interact with ventilation achieving a successful ramp up.A recommendation is made for higher levels of detail around secondary ventilation leading up to the primary fan installation. The information should be included as part of the tendering process and preliminary project execution planning. Understanding the æcrunch timeÆ concept can lead to strategies, as well as back up plans, to minimise any negative impact.By understanding key risks around primary ventilation establishment for a new mine, detailed design work can be completed where it is needed most. Value is added by reducing uncertainty and a payback with better contract terms and a more robust ramp up plan. This will improve the economic return for the company and reduce the risk.CITATION:Broad, B, 2013. Contract considerations and other critical ventilation aspects in achieving a new mine ramp up, in Proceedings The Australian Mine Ventilation Conference, pp 207-214 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Jul 1, 2013

By C Simpson

In 2011 the forecasted world demand for iron ore continues to grow, and during this time Australia is looked upon as a reliable supplier of high quality ore. The expansion of the current Australian mines is unlikely to meet the forecast demand. New mines are therefore being actively explored for and when discovered, are quickly being developed into mines in order to meet the world’s hunger for steel.The Solomon Project area is a large new iron ore discovery, located in the central Hamersley Ranges of the Pilbara province in Western Australia. The first Fortescue exploration drill holes commenced on the project in 2007 and to date three billion tonnes (Bt) of iron ore have been defi ned within the project area. Fortescue is fast-tracking the development of the ‘Solomon Stage 1’ project, with rail and mine construction commencing during 2011, and ore to be railed to Fortescue’s existing shipping operations at Port Hedland commencing in 2012. At a designed production rate of 60 Mt/a, the Solomon operation will be one of the biggest production centres of iron ore in the Pilbara.Deposit types include the three dominant mineralisation styles of the Pilbara province, being bedded iron deposits (BID), Channel iron deposits (CID) and detrital iron deposits (DID). All these mineralisation styles are present in large concentrations within the Solomon project area, and when mined will produce two product streams. These are a single product of CID, and a combined product from a blend of BID and DID material.This paper defines the geological characteristics of the Solomon iron deposits as recognised through the exploration and development of this vast resource over the three years since exploration commenced on the project.

Jul 11, 2011

By Y S. Zhang

Natural phenomena and human engineering construction activities had great influence on the geosciences space. Natural disasters, particularly mine disaster and other geological disasters happened frequently, which brought great losses both in people’s lives and economics, therefore, to explore the essential causes and mechanisms of disaster by some useful approaches is the most important step in mine disaster prevention. In a variety of methods, building an aground-underground seamlessly integrated model, and then analysing the formation and development mechanism of mining disaster based on this model is a useful way. In this paper, we studied an aground-underground seamlessly Integrated modelling method, and correspondingly given an aground-underground seamlessly integrated 3D spatial model, CSG+CD-TIN+GTP-TTS, by which we can carry out analysis of surface subsidence and underground laneway distortion efficiently, finally preliminary applications verified the effectiveness of this method.

Nov 22, 2011

By T G. Vizcarra, T J. Napier-Munn, A T. Karbowiak, M G. Hart

Squeezing extra performance from existing equipment (‘sweating the assets’) is key to continuous improvement initiatives, particularly during times of cost cutting where the option of spending additional capital to facilitate circuit upgrades can be severely constrained. A common challenge, however, is identifying the best combination of settings for different process variables, as their effects can be camouflaged by interactions with other process variables and, of course, noise in historical data.This paper describes a recent investigation at Boyne Smelters Limited to identify strategies to coarsen the product of its dry, fixed-speed, open-circuit AG mill, without the need for installing pre-screens prior to the mill. The product is used as insulation material for the reduction of alumina to aluminium, and an excessively fine product was inhibiting the ability of the cover material to dissipate heat from the underlying anodes. The approach was to undertake a series of experiments, designed according to statistical criteria, to elucidate the effect of key process variables (feed blend and power draw) upon the product sizing. The results provided clarity about what strategies would encourage the production of a more desirable mill product (with some surprises). The study is a good example of how properly designed experiments can identify hidden potential in processing circuits, thereby mitigating the need for capital-intensive upgrades.CITATION:Vizcarra, T G, Hart, M G, Karbowiak, A T and Napier-Munn, T J, 2018. Getting the most from existing processes: using cleverly designed experiments to optimise the line 3 AG mill at Boyne Smelters Limited, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 207–216 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

By H Lemos, E Nunes, D Jacobson, R Costa, L Ono, A Alves, H Delboni Jr

Oversize rock breaking and metal tramp removal are key issues for reducing primary crusher downtime, as well as improving the safety associated with its operation. Remote operation of such tasks would thus not only increase productivity, but also reduce the risks related to work in confined spaces, fall risks, and overhead hazards. These issues are particularly relevant in high-capacity operations such as iron ore mining, where large machines are in continuous operation. This article describes the architecture, construction and advanced testing of a novel remotely operated robotic mechanism for assessment and removal of metal tramp from primary crusher chambers. The system essentially includes a robotic-arm equipped with a hydraulic clamp tool for handling oversize material, as well as an oxy-flame module for cutting metal pieces entrapped within the primary crusher cavity. The first industrial unit was delivered to a large iron ore mine in Brazil, where the installation and testing is scheduled within the coming months.

Nov 8, 2021

By B Murphy, T Mattsson, R Crosbie, T Maksimainen

"An Outotec e500 TankCell, with 500 m³ of actual flotation volume, was commissioned at the Kevitsa Cu-Ni-PGE concentrator in northern Finland during 2014. This flotation cell was implemented at the head of the existing copper circuit as the first Cu rougher flotation cell. This was the first flotation cell of this size to be run under production conditions by any supplier anywhere in the world.The cell has been in continuous operation since start-up in October 2014 and has provided improvements in metallurgical performance at very low specific power consumption. On average, the cell has recovered 71 per cent of copper contained in the 0.37 per cent Cu flotation feed at a concentrate grade of 17 per cent Cu. The specific power consumption for the cell (excluding blower power) is typically around 0.4 kW/m³.After start-up, the impeller speed and superficial gas velocity were varied and the impact on metallurgical performance measured. In this paper a review of the cell operation at Kevitsa is given. Furthermore, the impact of mixing and gas dispersion on metallurgical performance is presented.Citation:Crosbie, R, Mattsson, T, Murphy, B and Maksimainen, T, 2016. Metallurgical Performance of Outotec's e500 TankCell at the Kevitsa Cu-Ni-PGE Concentrator, in Proceedings 13th AusIMM Mill Operators’ Conference 2016, pp 127–134 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Oct 10, 2016

By A Karrech, G M. Hassan, A Varghese, E Lessing, S Martins

Pumps play a critical role in mining operations, and their energy consumption and environmental impact are significant. This paper addresses the need for a holistic approach to sustainable pump deployment by expanding on previous work presented at IMPC Asia Pacific 2022 and World Mining Congress 2023. The research takes a significant step forward by outlining a structured approach to estimate and demonstrate sustainability tailored for operational slurry pumps. It details the calculation methodologies used to quantify the carbon dioxide emissions from electricity, wear materials and transport, as well as sealing water usage. To enhance practicality and usability, a simplified visual representation—called sustainability metrics—has been developed to monitor overall efficiency. The sustainability metrics consist of the availability, pump efficiency, and water utilisation efficiency. The proposed methodology is integrated with Pumps Condition Monitoring Service to maximise benefits. Three case studies, from iron ore, copper, and nickel operations globally, were employed to evaluate the proposed methodology. The findings demonstrate the critical role of sustainability calculations in understanding pumps operation. These calculations improve awareness of the pump’s role in the sustainability journey and enable effective monitoring. The studies highlight that continuous monitoring paired with effective prescriptive maintenance strategy can significantly reduce power and water consumption while maximising pump availability. The case studies also reveal significant shortcomings in current operational practices and non-optimal maintenance regimes, emphasising the need for practical recommendations to maximise savings and optimise pump performance. In the context of increasing climate change awareness and the imperative for global decarbonisation, this research highlights the necessity of critically assessing methods and operations to drive sustainability in the mining industry. By adopting a holistic approach to sustainable pump deployment, mining operations can effectively reduce their environmental impact while enhancing operational efficiency and economic viability. The proposed methodology and case studies provide valuable insights and practical recommendations for mining companies seeking to achieve sustainable practices and contribute to a decarbonised future.

Sep 1, 2024

By B Lumsden, R Smiles

Independence Group’s Jaguar Mine treats a polymetallic ore producing a copper concentrate and zinc concentrate. Effective separation of the sulfides requires relatively fine grinding with flotation feed P80 of about 75µm. Zn losses to final tails are greater than 60 per cent and <32 µm. When magnetic conditioning was first installed in 2010 it showed about an 8 per cent reduction of zinc in final tail and on some ores a similar benefit for silver as well. Current testwork is showing about a 12 per cent reduction in zinc and silver in final tail, consistent with the original testwork. Sizing of the final tail during the tests showed that the reduction of zinc and silver losses were only in the <32 µm fraction, as would be expected from an aggregation process. However, the most surprising result was about a 4 per cent reduction in zinc and silver in the plant feed with a >99 per cent statistical certainty. The reduction in zinc and silver in the feed is also only in the <32 µm fraction. Therefore, because the magnetic conditioning of Zn flotation feed cannot impact plant ore feed grade the hypothesis is that the magnetic conditioning is reducing the fine mineral from downstream processes, like filtering and thickening, returning to the plant feed in the recycled process water. This hypothesis is consistent with plant observation of dirty concentrate thickener overflow and measurements of solids in the overflow, as well as the average % Zn grade in cyclone overflow that correlates with the magnetic conditioning ON and OFF days. This paper presents these plant test results.CITATION:Smiles, R and Lumsden, B, 2018. Improving fine sulfide mineral recovery in Independence Group’s Jaguar Mine zinc circuit, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 433–440 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

By B Taylor

Although the underground mining environment is arguably safer now than at any time in history, as underground mining operations across the globe increase in-depth, magnitude, and complexity, protecting workers from harm becomes increasingly challenging. In deep, stressed, seismic mines the development face is one of the most hazardous work areas. The active face is usually the furthest extent of the underground workings, so ventilation can be difficult to maintain, exposing workers to high temperature and humidity while working on foot and doing manual labour. While mechanisation has made many tasks easier in modern times, the reality of underground mining is that development charge-up workers still spend long periods directly exposed hazards at the face. In 2019, Orica and Epiroc partnered to co-develop the world’s first fully mechanised development charging unit using fully wireless initiation, called Avatel™. Built on Epiroc’s M2 Boomer carrier platform, the system is designed to allow one person to charge a development face from the safety of a fully enclosed cabin, thereby reducing exposure to hazards at the face. The system was prototyped in Europe before entering commercial introduction in 2022. This paper reviews earlier attempts to mechanise underground charge-up and describes the development journey and engineering challenges of building a mechanised development charging machine.

Mar 29, 2023

By P F. Hodkiewicz, J de Lacey, M Stewart, R Lane

"Implicit modelling is an approach to spatial modelling in which the distribution of a target variable is described by a unique mathematical function that is derived directly from the underlying data and high-level parametric controls specified by the user. This modelling approach may be applied to discrete variables such as lithology (after converting the discrete codes to numeric values) or to continuous variables such as geochemical grades. This paper discusses the estimation of continuous (grade) variables using implicit modelling.One of the underlying engines of implicit modelling for producing this mathematical function description is the radial basis function (RBF). In essence, the RBF is a weighted sum of functions positioned on each data point. A system of linear equations is solved to derive weights and the coefficients of any underlying drift model coefficients. Once derived, the RBF may be solved for any unsampled point or averaged over any volume to provide an estimate of grade. It is possible, for example, to query the RBF on a regular grid to derive an estimate of block grades. Given the ease of creation of an RBF, and its ability to predict grade, the question arises as to how the grades derived from the solution of an RBF compare with grade estimates derived from conventional geostatistical interpolation methods (eg ordinary kriging (OK)).The purpose of this paper is to describe in lay terms: the basic structure of an RBF the role of parametric choice in the solution of RBFs and how this influences the character of the solution the fundamental similarities and differences between RBFs and conventional geostatistical estimators.Using a high-resolution conditional simulation, we show that in many situations RBF and OK estimates are very similar.CITATION:Stewart, M, de Lacey, J, Hodkiewicz, P F and Lane, R, 2014. Grade estimation from radial basis functions – how does it compare with conventional geostatistical estimation?, in Proceedings Ninth International Mining Geology Conference 2014 , pp 129–140 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Aug 18, 2014

By F Clark, J T. Carswell

Ore definition for final stope planning is often a challenging prospect in underground (UG) gold mines which exhibit high geological and grade variability. Unlike the grade control (GC) scenario in an open pit (OP), the ability for the mining geologist to plan a sampling campaign which effectively characterises the underlying mineralisation is fraught with difficulty. UG sampling patterns are strongly clustered and typically not dense enough to characterise the spatial and statistical properties. Very commonly, sample volumes are not large enough to provide a reliable grade estimate of the surrounding rock. These factors critically affect our ability to accurately map out ore positions and estimate metal quantities.At Sunrise Dam, traditional UG sampling and modelling techniques have proven to be an unreliable strategy for successful stope planning and extraction. The problem was first observed during the final cut-back in the open pit for which the mineral resource model was constructed from UG diamond drilling. Open Pit grade control reconciliations were strongly positive for both tonnage and grade compared to the resource model. Underground workings missed significant quantities of ore which was laterally defined by open pit reverse circulation (RC) GC drilling. Upon examination it was realised that the cause of the problem was one of inadequate sample density and sample support, the implications of which potentially affected the entire UG mine.As part of a broader study into underground grade control procedures, detailed reconciliation of initial stope production from the GQ domain also pointed to inadequate sampling as a major constraint to effective grade control and reserve conversion.To overcome this deficiency, dense 115 mm wet RC grade control drilling and conditional simulation modelling has been successfully implemented with the intent to replicate the grade control process in the open pit. The increase in sample density and sample volume has proven to be a very effective tool for mapping out highly complex mineralisation. A marked improvement in stope definition, reserve conversion and Mine to Mill reconciliations has been demonstrated on the back of an innovative approach to UG grade control.CITATION:Clark, F and Carswell, J T, 2014. Using reverse circulation drilling to improve sampling in a complex underground gold operation – an innovative approach to underground grade control at the Sunrise Dam Mine, Western Australia, in Proceedings Ninth International Mining Geology Conference 2014 , pp 143–152 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 18, 2014

By M Doran

The Olympic Dam mine utilises 1.1 m to 1.4 m diameter raise bores for generating the initial slot void for most production stopes. Slot raise bores generally span two development levels ranging from 30 m to 50 m in height. Raise bores are reamed upward and typically leave a cap of rock equivalent to two times the raise bore diameter on the drill level (minimum 3 m). This provides safe access over the cap for subsequent production activities. It is therefore critical to ensure robust falling object protection for personnel accessing underneath, and in the vicinity of the raise bore void on the lower level. Recently, a number of mesh failures have occurred at Olympic Dam as a result of falling rock from the underside of the cap and raise walls. In addition, as Olympic Dam transitions to deeper and more challenging ground conditions, rockfall-off onto the raise bore protection mesh is anticipated to increase in frequency. This paper discusses the evolution of raise bore protection mesh used at Olympic Dam and presents results from recent site-based drop testing. This impact testing was carried out using a built for purpose object to replicate point loading and shear failure of mesh wires. Testing was also carried out on an improved mesh design which utilises two layers of Geobrugg high-tensile MINAX mesh. Results from the drop testing suggest an improvement in performance of the raise bore protection mesh is realised with the updated design.

Mar 29, 2023