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By M Graham, R Brunning, C Andringa-Bate, S Westergren

In 2010, Rio Tinto Iron Ore’s operations commenced the planning and design of a sampling and analysis system for the new 50 Mt/a Cape Lambert Port B (CLB) facility. Current sampling systems at the ports consist of automated robotic, mass-based sampling protocols employed at Dampier, and semi-automated, time-based sampling systems operating at Cape Lambert Port A.The new sampling system at CLB has brought together a fully automated sampling and analysis system utilising time-based sampling, with the capacity to sample ore products of medium quality variation as defined in ISO 3082 (ISO, 2009). The CLB system is required to sample at shiploading rates from 6000 t/h to 13 440 t/h and provide full load-port analysis. The sampling approach is to proportionally extend primary increments (of varying mass relative to shiploading rate) to a standard length using variable speed aero-belt conveyor systems. This enables a fixed number of secondary cuts to be achieved for all primary increment masses and to be delivered to the automated cell. The cell is required to be capable of concurrently processing four individual shipments, each containing multiple cargoes.Achieving the target sampling precision for all export cargo sizes has culminated in the planning, design and construction of the largest automated iron ore port laboratory in the world. The CLB sampling and analysis cell was commissioned in Q3 and Q4 2013. This paper discusses the sampling philosophy and commissioning outcomes.CITATION:Brunning, R, Andringa-Bate, C, Graham, M and Westergren, S, 2014. Cape Lambert Port B shiploading, sampling and analysis, in Proceedings Sampling 2014 , pp 79–90 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 29, 2014

By A D. Wulfse, C M. D Barton

Underground fractured aquifers in the Ernest Henry deposit are to a large extent controlled by deposit scale brittle structures. The underground mine has been subdivided into nine water zones based on hydrogeological characteristics, including conductivity and connectivity, within the mining areas bound by these structures. The nine water zones and the hydrological characteristics of the associated structures are utilised for risk assessing mine development and for targeting diamond drilling dewatering activities. Wireline and conventional underground diamond drilling techniques have been used throughout the network of underground aquifers with the aim of dewatering areas within the mining footprint. These dewatering drilling campaigns have historically been highly successful at lowering aquifer water levels throughout the underground workings. As part of recent mine expansion activities, diamond drilling has intersected high pressure (>507 psi), high temperature (>50°C) and high flow water (>3 L/sec) in as yet unconstrained underground aquifers. Groundwater is typically conducted through rubble and clay rich faults, further hampering progression of drilling. Drilling through fractured aquifers at depth presents both mine planning as well as safety challenges. Recent drill holes have been delayed or abandoned when aquifers hosting this high pressure, high flow water have been intersected, risking mine planning deadlines. Recent technological innovation developed to control groundwater outflows from the diamond drill hole whilst drilling has been trialled at the Ernest Henry Mine. This case study focuses on the utilisation of alternative drill methodologies to allow the current drilling campaign to continue without delay, whilst also improving safety conditions encountered on the drill site.

Mar 22, 2022

By P Holtham, R Dunne, D Stoll

Flash flotation is a process designed to remove coarse, liberated, fast floating minerals from hydrocyclone underflow. Irrespective of liberation, coarse particles would normally remain in a grinding circuit until they are reground fine enough to report to the hydrocyclone overflow. Additionally, minerals of high density also report to hydrocyclone underflow despite being fine in size and/or liberated because hydrocyclones separate on the characteristics of both particle size and density. Dense particles continually reporting to the hydrocyclone underflow can lead to over-grinding and the production of ultra fine particles. These particles exhibit slow flotation kinetics and thus are difficult to float in conventional flotation circuits. Therefore, removing coarse, liberated particles from the hydrocylcone underflow by flash flotation has the potential to improve recovery and can improve dewatering unit operations and reduce grinding costs.The impact on the overall performance of the flotation circuit by removing coarse, fast floating minerals prior to conventional flotation is not well understood. Ultimately, predicting the overall recovery improvement provides the justification for the installation of a flash flotation cell within the milling circuit. This paper will describe attempts to estimate flash flotation recovery improvements to the overall circuit using kinetic data from simplified batch cell flotation tests combined with limn-based modelling techniques.CITATION:Stoll, D, Dunne, R and Holtham, P, 2012. Modelling the impact of flash flotation from batch cell flotation tests using limn, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 179-184 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

By Y Li, S Ramazan, E Topal

A mine waste dump progression plan can provide a clear outlook of the mining operation. To produce such an output requires detailed placement schedule of the mined material, including the volume (or tonnage) and the allocated dumping location. However, current practise mainly focuses on the ore production, over-simplifying the waste material scheduling. As a result, a rock dump is often treated as a single point in long-term planning, making it difficult to predict the waste dump progression pattern over the life-of-mine. Without such a guidance, it is almost impossible to carry out progressive rehabilitation on the waste rock dumps. The lack of dumping schedule could cause delay in development construction, ie tailing storage facility and run-of-mine pad. Other downstream effect due to the over-simplification is inaccurate estimation of required truck hours, which could have huge financial impact on the operation.In this paper, mixed integer programming (MIP) models of different objective functions, ie maximise truck productivity by minimising the overall haulage distance, minimise required truck deviation between adjacent years, and a hybrid between the two objectives, are utilised to generate the long-term optimum rock placement schedules under the criteria of satisfying site specific conditions. All three MIP models are implemented in a large scale open pit mine. The numerical solutions from the models forms three different rock placement schedules, based on which, the yearly truck requirements are easily calculated and compared. The graphical results show the three corresponding waste dump progression patterns over the life-of-mine, providing the optimised long-term forecast of the operation.CITATION:Li, Y, Topal, E and Ramazan, S, 2014. Optimising the long-term mine waste dump progression and truck hour schedule in a large-scale open pit mine using mixed integer programming, in Proceedings Orebody Modelling and Strategic Mine Planning Symposium 2014 , pp 335–344 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 24, 2014

By S J. Schafrik, C Keles, C Schlosser, E S. Gilliland, A K. Louk, N S. Ripepi, S Keim, J Amante, E Diminick

Three legacy coalbed methane production wells have been converted to injection wells for a one-year carbon dioxide (CO2) injection test to evaluate the potential for CO2 storage in the coal reservoir and the potential for enhanced gas production at offset wells. The injection reservoir is composed of 15–20 individual coal seams with an average thickness of 30 cm (1.0 ft), spanning a depth range of approximately 240 (800 ft) to 670 m (2200 ft).The monitoring program for this test includes gas and water sampling of the three injection wells, three dedicated monitoring wells and approximately 20 offset production wells. Key technologies used for monitoring the study area include time-lapse GPS and interferometric synthetic aperture radar (InSAR) acquisitions for surface deformation measurement, a 28-station buried passive microseismic monitoring array, real-time downhole pressure and temperature sensing and perfluorocarbon tracer fluids, which will be injected with the CO2 stream. The schedule for the monitoring program includes pre- (baseline), during- and post-injection data collection. This schedule will allow data to be analysed for time-lapse changes and trends, which are important for understanding the migration of gas and fluid phases in the reservoir – including CO2, methane, other hydrocarbons and water – and for observing the changing distributions of reservoir pressures and stresses.The results of the monitoring efforts for this study have implications for monitoring mining operations. The combined use of GPS and InSAR geospatial data to evaluate elevation changes across and beyond the study area may prove to be an accurate option for measuring surface deformation, including mining-induced subsidence, in unstable terrain. Long-term microseismic monitoring using high-sensitivity instruments has several applications in mining operations, including rock stability monitoring, production monitoring and miner location detection during emergencies. Tracer studies and short-term microseismic monitoring used to assess methane extraction can also be used to develop and optimise degasification systems for underground coalmines.CITATION:Gilliland, E S, Ripepi, N S, Schafrik, S J, Schlosser, C, Amante, J, Louk, A K, Diminick, E, Keim, S, Keles, C and Karmis, M, 2015. Monitoring design and data management for a multiwell CO2 storage/enhanced coalbed methane test in a stacked coal reservoir, Buchanan County, Virginia, USA, in Proceedings Third International Future Mining Conference, pp 47–56 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 4, 2015

By J M. F Clout

The Roy Hill Project is an independent integrated port, rail and mine development in the Pilbara region of Western Australia. The bankable feasibility study for the project was completed in January 2011 by Roy Hill Holdings Pty Ltd, a wholly owned subsidiary of Hancock Prospecting Pty Ltd. The Project will deliver 55 Mt/a of premium quality iron ore to a rapidly growing market with a mine life of over 27 years. This study is based on exploiting a 1.2 Bt bedded resource of microplaty haematite-rich Marra Mamba, from which 562 Mt of reserves has been delineated to date. A further 1.1 Bt resource of detritals and low grade bedded is proposed to be mined once the bedded high grade resource is depleted. Roy Hill lump and fi ne ore products will compete strongly with other Pilbara products. As a low cost producer, Roy Hill is on track to capture four per cent of the global seaborne traded iron ore market. The project decision to proceed is targeted for Q2 2011 to enable first ore on ship by Q2 2014.

Jul 11, 2011

By T Baumgartl, J Burgess, B Emmerton, P D. Erskine

Large-scale open cut mining in the Bowen Basin has been undertaken for over 40 years. During this period, improved mechanical capability and economics have allowed extraction to greater depths, resulting in post-mining landforms of increasing height. Rehabilitation practitioners face significant challenges in stabilising these landforms and require a comprehensive understanding of the Bowen Basin Coal Measures strata likely to be disposed of during mining. Knowledge regarding the potential behaviour of differing spoil materials (following disturbance) provides a rationale to maximise short- to medium-term surface stability of constructed landforms by identification, salvage and advantageous reuse of cladding resources as a means to minimise erosional risks.CITATION:Emmerton, B, Burgess, J, Baumgartl, T and Erskine, P, 2016. Bowen Basin coalmine spoil classification for improved mine rehabilitation outcomes, in Proceedings Life-of-Mine 2016 Conference , pp 142–147 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jun 28, 2016

By C te Kloot, Z Liu

Blast performance and the resulting drawpoint condition and volume of oversize has the potential to impact operator safety and mine productivity. Underground measurements showed that approximately 14 per cent of production rings in the Ernest Henry Mine (EHM) sublevel caving (SLC) operation had either overbreak in the brow or left collars. There were also oversize rocks reporting to approximately 30 per cent of drawpoints, which accounted for over 7 per cent of total production and significantly impacted production rates. A series of trials were conducted in 2015–2016 at EHM to test changes to certain charge parameters in an attempt to optimise blasting results and, in particular, reduce oversize and overbreak. The detailed analysis conducted included field observations, hole surveying, blast monitor analysis and blast modelling. There were a total of nine charge parameters tested in the project, which fell into two major categories: energy distribution and inter-hole delay. These were based on observations made in establishing baseline data and those parameters most likely to have a significant impact on overbreak and oversize.Key results from the project included oversize reduction and improved brow conditions when energy distribution was reduced through changing charge lengths in certain holes in the standard charge plan. Similar benefits were also seen when the inter-hole delay between blastholes was reduced from 50 ms to 25 ms. Based on these results both changes were made to the standard production ring charge plan at EHM.Moving forward, the aim is to continue monitoring the results from the changes made on all levels to ensure efficiencies are being realised and sustained. A 3 per cent improvement in oversize as a percentage of total tonnes and improved brow conditions not only has a positive impact on production rates, but removes people from any potentially hazardous situations and contributes to a safer working environment.CITATION:te Kloot, C and Liu, Z, 2017. The evolution of production blasts at Ernest Henry Mine, in Proceedings 13th AusIMM Underground Operators’ Conference 2017, pp 33–38 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 16, 2017

By J Butler, N Patel, S Narendranathan, S Rastogi

The Yallourn Mine (YM) commenced mining of brown coal in the 1920s under operation by the State Electricity Commission of Victoria (SECV), prior to it becoming privatised in 1996. The present owners of the YM, Energy Australia Yallourn (EAY), acquired the site in 2000 and intend to continue operations until scheduled closure in 2028. Brown coal extracted from the YM is fed into the Yallourn Power Station which supplies approximately 22 per cent of Victoria’s electricity. Water within the YM is collected and stored in the Township Field Fire Service Pond. Water levels within the Fire Service Pond (FSP) may fluctuate considerably depending on the requirement for storage at the site. With due consideration to the stability performance of mine batters adjoining the FSP, the authors performed slope stability assessments to evaluate the risk and consequence of batter instability during the potential pond filling as it approaches the ‘critical pool’. The critical pond is defined as the level at which the driving forces (destabilising forces) are at their greatest and the resisting forces (lake forces, friction) are at their lowest. This assessment was undertaken using the Mine Geotechnical Risk Index (MGRI) approach.

Aug 2, 2023

The major greenhouse gas emissions from coal combustion are leading certain people to argue for uranium mining and nuclear power to meet these challenges. Although there is considerable rhetoric around promoting nuclear power as 'green' due to its relatively lower greenhouse intensity, a careful study of the data is required to properly underst and the sustainability of uranium mining and nuclear power and whether it can or should have a role in future energy supply scenarios. This paper presents detailed research and analysis on uranium mining, focusing on known economic resources, production, solid waste and water management, pollution issues as well as energy and greenhouse aspects. A particular focus will be on Australia and its operating and prospective uranium mines. Overall, the paper raises fundamental issues concerning the long-term sustainability of uranium mining and nuclear power and documents the greenhouse intensity of uranium production and the nuclear fuel chain.

Jun 1, 2010

By G Hancock, A Kemp, I Taylor

The mine site is situated south east of Port Hedland in the Pilbara region of Western Australia. A detailed engineering design was undertaken for six irregularly shaped waste rock dumps at the site. The design was undertaken to ensure long-term stability of the dumps and optimise material movements for closure construction. The Watershed Erosion Prediction Program (WEPP) and SIBERIA landscape evolution modelling was undertaken for the landforms using regional and site-specific material characteristics to provide an indication of the maximum allowable slopes and corresponding slope lengths for long-term stability.The majority of the waste materials present in the waste rock dumps are considered likely to be subgrade banded iron formation (BIF) and chert, which is generally competent material. The presence of a large number of dolerite dyke swarms indicates appreciable volumes of dolerite were produced as waste from the pits. Geological records also indicate that the dolerite is logged as being heavily kaolinised in the geological logging, hence kaolinite is very likely to be present within the waste dumps on-site. This material has an elevated risk of being highly erodible/dispersive. Clays and shales are also likely to be present in the dumps and are considered to be less competent material (relative to the BIF/chert).The final design configuration of the largest existing ‘unplanned’ waste rock stockpile is compared to a hypothetical continuous ten degree outer embankment alternative. This paper will present a brief description of the alternatives for closure of three waste dumps in close proximity to each other and how the detailed design based on site-specific materials and conditions compare to an alternative approach blankly assuming that most materials will be erosionally stable at less than ten degrees.CITATION:Kemp, A, Taylor, I?and Hancock,?G,?2014. Landform design for Pilbara mine site – why plan and design waste rock dumps for closure based on site-specific conditions?, in Proceedings Life-of-Mine 2014 , pp 47–54 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 16, 2014

By L Gobbo

X-ray diffraction (XRD) provides useful information about the composition of an ore sample in terms of quantification of crystalline phases and amorphous content. The use of new, fast detection systems implemented in CubiX FAST industrial diffractometers creates the opportunity to use this technique in exploration and modern process control. Besides the chemical composition of iron ores, their phase composition is also an important factor for exploration, quality control and processing. In the analysis of iron ore, XRD can identify the phases containing iron, such as haematite Fe2O3, magnetite Fe3O4, and goethite FeO(OH), and any other mineral phases present, especially silicas. Quantitative analysis is possible by various classical methods such as straight line or polynomial calibration with standards, but modern quantification analysis techniques such as Rietveld analysis or full pattern autoscale analysis are attractive alternatives, as they do not require any standards. These methods offer impressive accuracy and speed of analysis. Another analysis technique offering great benefit to ore exploration and process control is cluster analysis. This technique greatly simplifies the analysis of a large amount of data, eg from drill core samplings, and automatically sorts closely related scans of an experiment into separate clusters and marks the most representative scan of each cluster as well as outlying patterns. This can facilitate multi-dimensional compositional mapping of ore deposits, identifying regions of favourable mineral composition and allows fast and reliable tracking of the process. It is the most economic procedure to have automatic data evaluation without involving any dedicated personnel in the process. Details of the techniques used, sample optimisation methodologies, results, data precision and limitations will be discussed. The approaches have enormous potential as an inexpensive, reliable tool, useful in the characterisation of iron ore materials in an industrial environment.

Jan 1, 2009

By E Widzyk-Capehart, T Bednarz, O Daud, N Cutmore

The interest of industry, in particular future mining, is pointing towards the use of novel visualisation systems to improve the operational efficiency of user interfaces. While the technologies used to enhance operators’ experience are advancing, the implementation of novel visualisation paradigms within mining operations is trailing behind other industries, particularly health and aviation. In this work, we present a number of initiatives and use cases of immersive virtual and augmented reality systems that can fit within the mining context. These ideas represent a step towards new platforms that might increase the efficiency and safety of mining operations through applications such as 3D panoramic video monitoring technology with annotated information coming from big data analytics and visual analytics processing engines. However, while the technologies are used in a variety of training settings, their application in the working environment is lagging behind. This paper presents examples of scientific visualisations that could be applied in a mining context to extend the possibilities of operators’ cognitive abilities and working efficiency. They are intended to foster a discussion within the mining community to move beyond the training realm and into the operational environment.CITATION:Bednarz, T, Widzyk-Capehart, E, Daud, O and Cutmore, N, 2015. Effective immersive visualisation systems for mining applications and beyond, in Proceedings Third International Future Mining Conference, pp 31–36 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 4, 2015

By D Reid

Characterisation of non-plastic segregating tailings presents a number of challenges: the material cannot typically be sampled in an undisturbed state, remoulded samples exhibit different behaviour to undisturbed samples, penetration test interpretation methods suffer from uncertainty in their application to many tailings and the tailings gradation changes considerably over relatively small lateral distances and depth. In addition, the process liquor of many Western Australian tailings contains large quantities of salt and other dissolved solids, which can further complicate laboratory test programs. To provide an insight into the variability at a typical gold tailings facility, four gradations of the material were tested to obtain critical state parameters. Historic surficial tube samples were collated and organised by gradation to establish the range of densities typical after settling and air drying. These were then compared to laboratory-accessible densities. Finally, tube samples were tested in the laboratory to observe if the large-strain material behaviour was consistent with the inferred critical state parameters for similar gradations. Site pore fluid was used in the testing of the tube samples in an attempt to assess if the pore fluid modified the critical state conditions of the material.The tube samples tested all exhibited strongly dilative behaviour in undrained shear. Of the four samples tested, only one exhibited behaviour consistent with the inferred location of the critical state line relevant to the material’s gradation. The reasons for the unexpected behaviour of the other three samples include layering within the samples, the potential influence of large quantities of salt in the pore fluid and likely differences in the gradation of the fines components of samples taken from mid-beach and the decant area.CITATION:Reid, D, 2015. Observations on the behaviour of a gold tailings with hypersaline pore fluid, in Proceedings Tailings and Mine Waste Management for the 21st Century , pp 191–200 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 27, 2015

By C K. Boafo, J Visser

Obuasi Mine in Ghana, with more than 100 years of mining history, developed from a surface operation into a deep >2000 m underground gold mine. The challenge is to extract value from narrow veins left after extensive mining in the wider ore zones of the mine. Since the merger of AngloGold and Ashanti Goldfields in 2004 the mine strives to achieve optimum extraction through an integrated Mineral Resource management process from geological modelling, resource evaluation to mine design and scheduling. The shear hosted gold deposit displays complex secondary shears of variable thickness and continuity. There is an ongoing process of changes taking place in the way that geological modelling and resource estimation is done. Recent developments include the use of computerised systems that support the whole resource management chain from resource modelling to reserve optimisation. The change in thought and technology now allows for targeting narrow veins previously ignored in optimisation and mine design since moving into mechanised mining. The increased knowledge and confidence in the resource models now allows for flexibility in mine design, selection of mining method and scheduling and extraction of the reserves. The focus area for change is the way the orebody is evaluated and extraction designed. Since 2005 major changes were made to the process. This paper considers the historical approach of resource management. It looks at the individual process changes and qualifying the way ahead.

Jan 1, 2008

By E C. F Hamman

Sunrise Dam Gold Mine is a large open pit mine 730 km NE of Perth, Western Australia. Contract mining commenced in the open pit in September 1996 in lake clays and saprolites with the first fresh rock mined late 1999, and the underground starting the first decline in October 2003. By May 2007, over 150 million cubic metres of material had been mined and the pit was 360 m deep with 80 m remaining before reaching the planned final depth in early 2008. A final cut-back in the northwest will commence in late 2007 with open pit mining in the Mega Pit expected to conclude in late 2010. The challenges of developing the pit can be divided into three phases:Soft materials û mining was in multiple staged pits and cut-backs in lake clays, saprolites, weathered material. The varying characteristics had a significant impact on mining methods and slope stability. Structural û mining was gradually exposing more fresh rock and the drive was to understand how major structures and lithological contacts impact on local and large-scale stability. This had a significant influence on mine design and scheduling. Slope angles û achieving the final slope angle is critical. This is done through application of high standards of final wall establishment and proactive geotechnical hazard identification and management. This includes dealing with the rapid rate of descent, interaction with underground excavations and managing rock fall risk. The paper discusses each of these phases, highlighting the geotechnical controls implemented to date, looking at their success and impact on mining.

Jan 1, 2007

By P Crittenden

Thiess Pty LtdÆs Australian Mining business unit used 7.6 PJ of energy in the 2007/2008 financial year. This represented more than 85 per cent of Thiess Pty LtdÆs total energy use and therefore meant that the Australian Mining business unit is required to conduct energy efficiency assessments and report publicly on the outcomes by December 2008 under the Federal GovernmentÆs Energy Efficiency Opportunities (EEO) Act. Thiess Pty Ltd has a policy commitment to sustainable development throughout its operations. This includes minimisation of its carbon footprint and the Australian Mining business unit has a strong focus on efficiency in all of its operations. It approached the energy efficiency assessment as an opportunity to further improve and build on its energy efficiency and greenhouse gas reduction focus in the business. As a mine contractor, Thiess faced a number of challenges in designing an assessment process that would be both effective and efficient to deliver. For example, unlike most other companies involved in the Energy Efficiency Opportunities program, the energy use associated with the Australian Mining business unit is not fixed to any single geographic location in Australia. Mining vehicles are moved from site to site according to the specific requirements of mine owners and the timing associated with the commencement and completion of contracts. Thiess departed from a traditional æsite by siteÆ based assessment and designed a ærepresentative assessmentÆ approach that involved detailed investigation of data across all sites and a focused assessment on a single site.Data and analysis was an essential part of the assessment and indicators at company, mine and site level were essential in identifying opportunities and tracking progress. Forty-six potential energy saving opportunities were identified and four of these are currently being implemented. The projects being implemented are: payload management, automating mobile lighting equipment, plant idle time management, and turbo idle downtime. The potential savings from the four major projects that have been identified are approximately 150 800 GJ/annum, equivalent to 10 600 tonnes of CO2-e/annum with a simple payback period of less than two years. Beyond the fuel savings however, there are a number of other benefits from the assessment, including operational efficiency, reduced maintenance costs and even a potential reduction in the number of vehicles required to complete the work. The EEO assessment has significantly increased the importance and urgency of energy efficiency and facilitated the sharing of good practice across all Thiess operations. Not only have four projects been adopted for immediate implementation but a further pipeline of projects is available for future possible implementation. This case study describes: how Thiess conducted its assessment including the use of energy data and indicators, the opportunities identified that are currently being implemented, and the lessons learnt and how other organisations can use these to improve their approach to energy efficiency assessments. This case study is a more comprehensive version of a case study developed for the Commonwealth Department of Resources, Energy and Tourism. The assessment results reported in this case study are drawn from the Thiess Energy Efficiency Opportunities Report 2008.

Jan 1, 2009

By D Wimpenny

The Bogong Power Development Project in Victoria, Australia involved the construction of a 15 m long mass concrete plug up to 9 m in diameter within the head race tunnel. The plug is critical to theperformance of the scheme as it permanently seals the head race tunnel under approximately 300 m head of water.The location of the plug in the headrace tunnel was determined by a programme of in situ rock stress testing using both hydrofracturing and over coring stress testing methods.In recognition of the importance of the plug, the Head Contract specification requires that its temperature during hydration be controlled using an embedded cooling system. In addition, contact grouting and curtain grouting around the plug cannot commence until thermal contraction was substantially complete.This paper describes the use of bespoke fi nite element software to model the temperature rise in the plug and design mitigation measures to control temperature rise in the plug. These measures include restricting the concrete placing temperature to 10°C, incorporating 39 per cent fly ash in the concrete and installing embedded cooling circuits.Site trials were undertaken to calibrate the model for the proposed concrete mix. The cooling system comprised 25 mm ID pipes forming twelve separate circuits that fed 7°C water from a single chiller unit. The cooling system reduced the peak temperature in the plug to approximately 30°C and the associated risk of early-cracking. The time before contact grouting could commence was shortened to less than two weeks from casting.

Mar 8, 2011

By I C. Carrasco, V G. Mirada, J F. D Domingo, F S. Leite

This paper investigates ore loss and dilution produced by rock movement in bench blasting. A total of four blasts, in which electronic detonators have been used, were monitored in Cobre Las Cruces Open Pit Mine (FQM Ltd) in Gerena (Sevilla, Spain). Rock motion has been obtained in 137 points of the free face and 6 points inside the block. Multiple liner regression has been applied to predict rock motion and estimate ore dilution as a function of hole coordinates, rock contacts, powder factor/hole, amount of explosive per blasthole, burden, spacing, hole length, stemming length, explosive energy, hole row, subdrilling, blast sequence, stiffness ratio, blasthole distance to free face, rock density and Young’s modulus. The model is statistically significant with a determination coefficient over 0.8. Rock motion measurements in 31 more points have been used to validate the model and to show a reduction in ore dilution.CITATION:Domingo, J F D, Leite, F S, Mirada, V G and Carrasco, I C, 2015. Dilution, ore grade and blast movement calculation model, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 71–78 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By A D. Caccioppoli

Grade control systems within Rio Tinto Iron Ore have proven to be robust, when mining full benches. The Hope Downs 1 operation hosting two Marra Mamba Iron Formation deposits (North and South Deposits) presents a new challenge, where increased mining selectivity due to moderately plunging N-verging folds has made flitch mining necessary in the South Deposit. Poor flitch blasthole sample duplicate results in South Deposit over a 12 month period, compared to North Deposit, have highlighted concerns with grade predictions. In contrast a new grade control methodology (grade splitting) was proposed to alleviate blasthole sampling bias, utilising geological mapping and mineralogical logging, currently practised throughout Rio Tinto Iron Ore Pilbara operations, to estimate theoretical grades for each flitch from a single blast cone assay. To assess this method, reverse circulation holes (RC) were twinned to blastholes establishing an ‘actual’ grade. These blastholes were assayed using current flitch sampling techniques where: flitch positions were estimated, flitch positions were marked with paint, and a full cone sample was taken for ‘grade splitting’. Using these data sets multiple grade predictions were produced, then analysed using Half Absolute Relative Difference (HARD) statistical analysis. In addition to testing these grade control methodologies two other findings were ascertained: an inherent bias in blasthole assays exists particularly in the top flitch, where an average absolute difference of 0.6 per cent in SiO2 and 0.42 per cent Al2O3 was measured; and assays derived where kaolin rich soft shales are intersected were less representative. This is likely to be due to these materials not being properly represented in blast cones. Grade splitting accurately estimated block chemistry, except for a slight under-prediction in Al2O3 and P compared to current grade control methodologies. This method is a viable alternative where grade distribution is stratigraphically controlled.

Aug 22, 2011