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By A L. de Ambrosis, S J. Clarke

In the non-codified realm of tunnel design there are issues which are sure-fire instigators of controversy. This paper presents a discussion regarding one particular issue which in the authors’ experience often results in comment and debate. This issue only forms part of the rock load assessment process, but it is specifically addressed with the intention of presenting a rational basis for design, which may result in broader acceptance within the tunnel design community.The issue considered relates to the characterisation of in situ rock stresses for the design of tunnel support in the Sydney Basin. A summary is given of the literature on the topic, with emphasis on the main sources of uncertainty and contention. A design approach is proposed, with particular focus given to the numerical modelling of in situ ground stresses and the approach used to ensure that the adopted stress regime is consistent with the assumed ground model. The resulting variability in the initial stress field is discussed and comparisons made to the test database.CITATION:de Ambrosis, A L and Clarke, S J, 2014. Characterisation of in situ stresses for tunnel lining design in the Sydney?Basin, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 247–252 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By J Boshoff, D Reid

It has been recognised worldwide that the liquefaction risk of unconstrained tailings stacks or cyclone underflow embankments requires careful consideration. The stability of a tailings deposit where the perimeter embankments are made up of hydraulic fill is often governed by post-liquefaction stability.Cyclones are frequently used around the world to classify tailings into a coarse underflow for building a tailings impoundment wall and a finer fraction that is disposed of into the basin. The shear strength of the tailings that form the outer embankment of a tailings storage facility (TSF) and the location of the phreatic surface are the two most significant factors influencing the structural integrity of the facility. The coarse underflow is placed in such a way as to contain the overflow, which is finer, has low strength and is often poorly consolidated.A cyclone field trial was undertaken at a gold mine in Western Australia to assess the feasibility of using the cyclone deposition method to optimise and increase the capacity of an existing tailings cell. The aim of the cyclone trial was to collect information to demonstrate to the client and the regulators that cyclone deposition was a feasible option for raising TSF embankments. The cyclone trial provided an opportunity to assess the cyclone under field conditions and the quantity and quality of the underflow fraction produced on-site. A variety of methods were used to assess the flow liquefaction susceptibility of the tailings underflow sample produced during the cyclone field trial.The field trial, laboratory testing and analysis will be discussed in this paper.CITATION:Boshoff, J and Reid, D, 2015. The resistance of cyclone underflow material to flow liquefaction, in Proceedings Tailings and Mine Waste Management for the 21st Century , pp 151–156 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 27, 2015

By M Higgins

Measurement while drilling (MWD) techniques can provide a useful tool to aid drill and blast engineers in open cut mining. By avoiding time consuming tasks such as scan-lines and rock sample collection for laboratory tests, MWD techniques can not only save time but also improve the reliability of the blast design by providing the drill and blast engineer with the information specially tailored for use. While most mines use a standard blast pattern and charge per blasthole, based on a single rock factor for the entire bench or blast region, information derived from the MWD parameters can improve the blast design by providing more accurate rock properties for each individual blasthole. From this, decisions can be made on the most appropriate type and amount of explosive charge to place in a per blasthole or to optimise the inter-hole timing detonation time of different decks and blastholes. Where real-time calculations are feasible, the system could extend the present blast design even be used to determine the placement of subsequent holes towards a more appropriate blasthole pattern design like asymmetrical blasting.

Jan 1, 2001

By M D. Griffith

Oct 12, 2022

By N M. Player, R P. Varden, E Jones

"An effective geotechnical design provides an accurate and appropriate assessment, balanced with a mining company’s risk profile. Justifying the cost of slope assessment requires an understanding of the input sensitivities, and resultant risk, to achieve a slope of a required functionality. As a project progresses from Scoping to Feasibility, the geotechnical risk becomes better resolved through increased expenditure on drilling, testing, analysis and modelling as long as the input data is appropriately spatially distributed. Providing accurate and appropriate geotechnical assessments in the early stages provides confidence in all following stages, especially where initial analysis indicates difficult geotechnical conditions. It is also in the early stages of project definition that there is most opportunity to maximise the value of the deposit through investigations into optimal mining methods.This paper examines the advantages of geotechnical engineering input through a project study period. Early geotechnical involvement allows the Scoping and Pre-Feasibility Studies to be more effective. Operational risks can then be better understood and dealt within the Feasibility Study phase, also ensuring that the correct risks and management controls are put in place.With commodity price pressure and cost of resource recovery in a downturned industry, reducing the risk to cash flow, resource recovery and safety should be a primary goal for all mining companies. Reduced risk can be effectively achieved through geotechnical design of slopes to achieve a required performance as part of an integrated study to the Reserve definition and mine design.Citation:Varden, R P, Player, J R, Player, N M and Jones, E, 2016. Justifying Slope Design Risks and Costs, in Proceedings Ninth AusIMM Open Pit Operators' Conference 2016, pp 185–201 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Nov 15, 2016

By S Pradhan, A Kuras, R Mahajan

This paper describes the design of the precast concrete segmental lining for the 13.1 m internal diameter and 450 mm thick, 2.4 km long mainline tunnels for the Waterview Connection project in Auckland for the New Zealand Transport Agency.The design and detailing of this segmental lining presented some noteworthy challenges, including an alignment that has sections of low cover in soft ground. Key points of interest are that this precast segmental lining is the largest to ever include steel fibres as the primary method of reinforcement and the lining includes cams on circumferential joints to control ring deformation.The paper describes some of the key design decisions that were made in a collaborative manner with the construction team, tunnel boring machine manufacturer, segment manufacturer and the designers.CITATION:Mahajan, R, Kuras, A and Pradhan, S, 2014. Design of segmental lining for Waterview Project, Auckland, New?Zealand, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 289–294 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By D Nieuwkerk, V J. Absolon

"Screw press technology is an innovative approach to tackling the growing pressure to conserve water and minimise the environmental impact of mineral tailings disposal. The principles of the technology have been known for a considerable period of time in non-mining applications such as water treatment, wastewater (municipal sludge), as well as in the paper and chemical industries for dewatering solids, particularly those containing clays.The screw press represents a viable niche technology for filtering fine and high-clay tailings, without the prior thickening stage, and is capable of producing a filtered product that is sufficiently consolidated and dry enough to provide a product suitable for conveying and dry stacking.The Ishigaki screw press was introduced in 1990 and key features are: continuous operation and excellent availability low wear to plant acceptable flocculant consumption low carbon footprint and low noise levels fully automatic.These features lead to simpler plant layouts, easier maintenance, smaller spares inventories, reduced wear, smaller footprint and overall lower capital and operating costs.The amenability of a particular tailing stream to treatment by screw press technology may be determined by test work. Two pilot plant studies are described where this technology has been applied in the mineral industry being flotation tailings from a rare earth (RE) mineral concentrator and coal tailings. In addition, preliminary details are given of an ACARP sponsored research program titled ‘The application of screw press filtration in tailings dewatering’.CITATION:Absolon, V J and Nieuwkerk, D, 2014. Innovative use of screw press filtration in tailings dewatering plant design, in Proceedings 12th AusIMM Mill Operators’ Conference 2014, pp 449–456 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Sep 1, 2014

By M A. Llano-Serna, D J. Williams, L Bu

Tailings dam failures continue to occur worldwide at an unacceptable rate, averaging two events annually over the last 100 years. Furthermore, tailings dams continue to grow in size, increasing the potential release of tailings and water should they fail. Tailings are generally deposited in a slurry state, with the potential to flow if containment is lost. Understanding the generation and propagation of excess pore water pressure on failure is critical to predicting the flow and run-out of tailings. This paper presents numerical modelling using the material point method indicating that tailings run-out processes may be self-enhanced by the excess pore water pressure induced during the collapse of the containment. Moreover, it is shown that geomorphological features, such as the slope and its surface roughness downstream of the tailings dam, influence the pore water pressure dynamics upstream of the advancing toe.CITATION:Llano-Serna, M A, Bu, L and Williams, D J, 2018. Excess pore water pressure induced during tailings run-out, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 377–383 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By A Sadri, S Smith

In the metal and mineral industry, different empirical techniques are used to estimate the remaining thickness of the lining within an operating furnace. The disadvantage and costly factor when using these methods is that production needs to be halted. Hatch has developed an accurate and reliable technique based on stress wave propagation principles to determine the condition of the remaining lining whilst the furnace remains online and operational.The technique involves test data collected and compiled to generate 3D imagery used to assist operators and maintenance planning personnel with valuable information showing areas of metal penetration in the lining, remaining lining thickness, exact location of voids, cracks, poor contacts and deterioration due to chemical attack. In this paper, the principals of the AU-E technique will be explained both theoretically and practically. In addition, the use of ultrasound technology for determining the condition of copper cooling elements will be briefly addressed.

Jan 1, 2006

By C Fischer

The introduction of digital communications technologies into the underground mining industry, in both coal and hard rock mining, has enabled high bandwidth applications to be applied in the mining industry. Digital networks based on 802.11 b/g/n open Wi-Fi standards have allowed numerous applications to be run over a single communication backbone. One of the many important applications is the tracking of personnel and equipment via RFID Tags. This tracking application has formed the basis of a Proximity Detection System or Collision Avoidance System (Schiffbauer and Mowrey, 2001; Kent, Fischer and Schiffbauer, 2011) thereby improving safety and increasing control in the mining environment. This paper discusses the growth of digital technology as the backbone for communications in underground mining applications. This growth has allowed the ‘convergence of technologies’ (occurring in the general business world) to be available to mine operators in general and underground mine operators in particular. Mine Site Technologies’ involvement with major mining companies and mining equipment manufacturers (OEMs) in developing and supplying their communication systems is also discussed.The latest technical requirements and specifications for communication systems for underground and open cut mines will be reviewed.

Nov 22, 2011

By R M. Stephenson

Large diameter raise boring is a common raise excavation method in the Australian mining industry. Geotechnical investigations were conducted on several large diameter raise bore projects at Gwalia Mine to assess the potential for instability and potential back-reaming problems. A thorough geotechnical analysis and subsequent back-analysis was conducted on a vent raise excavated at 5.5 m diameter and 810 m length.The geotechnical investigation for the vent raise included collection of data from an acoustic televiewer survey that was conducted on the pilot hole. The survey results provided structural data and an insight into the effects of stress on the pilot hole. Structural analysis was conducted using a combination of information obtained from the acoustic televiewer survey and geotechnical logs of the diamond drill core drilled close to the site.Further information was collected from drillers’ plods from pilot hole drilling and back-reaming to conduct a back-analysis of the completed shaft, and this was compared with the structural analysis.The key finding from this review was that the acoustic televiewer survey of the pilot hole accurately identified locations with blocky conditions. This is an important supplement to the information available from the main geotechnical investigation hole, as this was offset from the shaft location over most of its path.CITATION:Stephenson, R M and Sandy, M P, 2014. Structural analysis of acoustic televiewer logs for large diameter raise bored shafts, in Proceedings 12th AusIMM Underground Operators’ Conference 2014 , pp 89–96 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Mar 24, 2014

By A Roshal

It is anticipated that many future uranium mines in Australia will be using the in situ leaching mining process. It is fair to say that close to one third of uranium production will be generated by this method, whilst the other two thirds will fall on the uranium generated from hard rock mining and other mining methods, such as traditional open cut mining. For other types of deposits the in situ leaching mining method will remain the best technological, commercial and environmental alternative. It is important to identify and prevent all risks involved in uranium mining. The expertise in this subject is limited. Over the years there was only one mine using the in situ leaching process for uranium extraction in Australia. Computer simulation of propagation of leachate during and after the uranium in situ leaching is a crucial factor, not only for addressing the environmental concerns, but also for the most efficient recovery of the deposit. The decontamination can be modelled for a period of up to 100 years, with the acid neutralisation forecast for a period of up to 400 years. The results of the modelling are paramount for definition of the reserves, efficiency of the mining method and the environmental impact statement. The accuracy of the hydrogeological modelling and carefully selected environmental management program enables a mining company to quantify and minimise the impact of the mining activities on the regional aquifer and to prevent environmental disasters. In the study, the completed hydrogeological model allowed the client, the authorities and the community to make an informed decision about the environmental impact of the in situ leaching of uranium. In particular, the model proved that neither during the mining, nor during the neutralisation the toxic elements would interact with the local catchment area.

Jan 1, 2008

By M Salu, G J. Kay

"As underground mines increasingly face the challenge of maximising production without losingfocus on safety excellence, the ability to predict the eff ectiveness of mine seals and stoppings andthe identifi cation of defects plays an increasingly important role in mine ventilation management.While technologies for sample testing installed seals provides signifi cant assurance, the difficulty of conducting tests in operational environments, combined with the production impact of destructive testing procedures, has led to the development of a new method for non-destructively testing ventilation control devices (VCDs). This paper addresses the challenges of in situ testing and reviews the approaches previously employed to verify the quality of VCD installations. It then describes a new testing methodology jointly developed by Whitfield Minerals PTY Ltd and Parsons Brinckerhoff (PB) and the range of tests that have been carried out in the laboratory, above ground, at trial underground sites and in active coal mine operations. Although this is a new approach to testing underground VCDs, the method employs recognised testing equipment in a new application. The aim of the new non-destructive technology is to not only verify the thicknessand therefore overpressure rating compliance, of new VCDs, but to allow mine operations t oidentify and locate defects in installed VCDs without causing damage to the material structure.Currently it is difficult, time-consuming and costly to carry out physical sampling and testing ofevery VCD. Therefore, a reliable and accurate means of non-destructively testing concrete andplaster seals in situ will provide substantial operational and safety benefi ts to the underground coal mining industry."

Jun 1, 2012

By D Johns, L Murray

This paper discusses pore pressures in the embankments of tailings dams by comparing real world data with common design assumptions. Assessment of pore pressures has implications on material behaviour interpretation from CPT investigations and, therefore, on the design. For example, the assumption of hydrostatic pressure is conservative for limit equilibrium stability analyses but may be un-conservative in assessing the potential for contractive behaviour and strength loss during shearing. This paper presents some real world data, the investigation methods to determine the pore pressures, and subsequent interpretation of CPT data and material parameters such as the state parameter. It also examines the design implications of assuming a hydrostatic pressure distribution, by comparing results from that assumption with those obtained using the real pore pressures.CITATION:Johns, D and Murray, L, 2018. Characterisation of pore pressure in tailings dams and the implications for design, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 239–249 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By R Dunne, W McCallum

Continuous improvement might be defined as seeking incremental improvement over time through improved equipment, processes, technology and the efforts of people. Most people working in ore processing facilities embrace the general principles of continuous improvement. However, given the industry-wide issues with skilled personnel and the constantly changing environment in ore processing facilities, it is often difficult to identify improvements in a facility over a given time period. The driver for these outcomes is the use of basic principles and technology to achieve best practice targets. The process involves four stages: develop standards of practice to define best practice in specific areas; write procedures to guide the organisation towards these best practices; implement the procedures and develop a review process to provide a method of measuring performance against best practice.By reviewing performance against best practice on a regular basis, the organisation measures progress towards the best practice targets and the incremental improvement between these regular reviews is a measure of continuous improvement.This paper provides the background for developing standards of practice for metal accounting, metallurgy and metallurgical management. The paper also describes how standards of practice can be used to develop continuous improvement and the skills set of the departmentÆs leadership team.CITATION:McCallum, W and Dunne, R, 2012. Metallurgical management tools for continuous improvement, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 225-230 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

By A Millar, B Wraith

Process plants are characterised by variability of performance over a wide range of time-scales; reflected in fluctuations in metal recovery, concentrate grade, plant throughput and reagent costs. In turn, these fluctuations impact financial metrics such as operating costs and revenue. The primary cause of plant variability is variation in the physical, lithological and mineralogical characteristics of the ore fed to the plant. The variability of the ore is driven by the intrinsic heterogeneity of the geology and mineralogy of the orebody, the mining method and mine production plan, the capacity to stockpile and blend, as well as the plant flow sheet and the level of plant automation. Whilst the impact of ore variability on process plants is universally recognised, it is rarely quantified in financial terms. Consequently, opportunities to reduce its impact are often overlooked due to the lack of a basis for a quantifiable cost-benefit analysis to justify improvement initiatives. This paper will present case studies using production data from the Renison tin concentrator and a zinc concentrator. These case studies demonstrate that as the standard deviation of plant head grade increases (as a proxy for ore variability), plant metal recovery subsequently reduces. The metal recovery is then converted into plant revenue losses, to quantify the economic impact of ore variability. The Renison case study demonstrated that whilst a very rare occurrence, revenue losses were as high as 34 per cent (relative to the baseline) when standard deviation was at its highest. The zinc concentrator case study demonstrated that revenue losses were as high as 6 per cent (relative to the baseline) when standard deviation was at its highest. Options are available for reducing and managing ore variability in the process plant. These options include changing mining practices so that the ore is fed to the plant with less variability, more advanced process plant control systems and the use of predictive geometallurgical models.

Aug 24, 2022

By J Ashford, Minniakhmetov

Geostatistical simulations are the best practice for uncertainty quantification in non-linear systems. Simulations are currently undertaken on an ad hoc basis in the mining industry due to high requirements in computing environments and advanced geostatistics. In contrast to the estimation process, multivariate simulations can be performed using different methods, tools, and computational environments, similar to data science. For large companies with multiple commodities it is important to have a standard framework to test, build, and run workflows using different methods, applications and computational environments. This work presents an auditable, modular and scalable framework to create geostatistical simulation workflows where the workflow is abstracted from the implementation. Key aspects: automation – workflows should be able to run automatically given updated data (if hands on modelling is not required); auditability – workflows should document key considerations and parameters; modularisation – workflows should permit swapping out components, for example substituting domaining in Leapfrog software with automated domaining using machine learning scripts; scalability – easy, repeatable, portable deployments on diverse infrastructure (for example, experimenting on a laptop, then moving to an on premise cluster or to the Cloud); reproducibility – parameters should be archived to permit re-running and reproduction of workflows in future years; and sensitivity analysis – any component of a workflow should be able to run with multiple scenarios of parameters and data to enable global uncertainty quantification and sensitivity analysis. The presented framework can be used to create different workflows for geostatistical simulations in multiple assets to quantify uncertainty in the value chain for resource categorisation, reserves uncertainty, value of information and robust mine planning amongst others.

Mar 22, 2022

By D Kay, M Lovitt

Mass Blasts are generally required at the completion of longhole stoping cycles to maximise the recovery of ore from a specific orebody. During the course of mining, the practice is to leave pillars of ore to support the opening left by extracted ore and to mitigate stresses from working areas of the stope. These pillars usually contain ore that has been included in the resource evaluation and is highly valuable to the mining operation. Due to their stressed nature, the removal of pillars by conventional blasting techniques, through small blasts, can result in pillars being reduced beyond their critical size and ultimately failing, rendering the ore unrecoverable. The AurionGold Kanowna Belle Gold Mine operates a Mine to Mill philosophy. This philosopy requires the fine tuning of blasting to provide the best possibe ore feed at the highest grade for mill productivity. This means that ore to the mill must be well fragmented from blasting that provides high extraction rates from draw points, with minimal dilution from overbreak or fall off, and sized to maximise SAG mill throughput. The AT04 Mass Blast contained significant ore reserves which were required to meet gold production targets. KBGB needed the AT04 Mass Blast to perform as well as if not better than conventional stope blasts to maintain mill production. This paper describes the circumstances, planning philosophy, techniques, including the use of Electronic Initiation Systems and Bulk Emulsion Explosives, and results that provided a highly successful outcome.

Jan 1, 2002

Blasthole cone samples are used for grade control in most of the iron ore mines of the Pilbara of Western Australia. This method of sampling is straightforward when the target sampling interval matches the mining bench height but is problematic when the blasted bench is 'flitch' mined in two or more passes. Crucially, the sampler needs to decide which part of the blast cone represents the upper and lower flitches to be mined. This sampling selection decision is usually made by assuming a certain proportion represents the subdrill component of a sampling face in a blasthole cone and the two flitches are split equally from the remaining portion. In this study of a West Australian channel iron deposit, sampling experiments were carried out to determine the actual proportions of a sampling face in a blasthole cone by spray painting the blast cones at flitch and subdrill boundaries during the drilling process. Measurements were then taken to assess the differences between assumed sampling face proportions and actual proportions. A set of paired samples was also collected from a number of blastholes with one set using the assumed proportions of each flitch for each sample, while the other set sampled the actual proportions, which were identified from the cone painting process.

Mar 1, 2010

By A Purton, C Taylor, E Conroy

The spatial modelling of geometallurgical domains is an important step in the characterisation of an ore deposit allowing for the quantification of various rock types, their differing rock properties and the overall value of a project. The traditional approach to modelling such features is through the use of deterministic models, where a single estimate of the extents and structure of the ore deposit is mapped out by geologists based on available data and their interpretation of the geological processes. Any uncertainty in the layout of different domains is not accounted for and heterogeneities of chemical and physical properties of the orebody are likely underestimated. Spatial machine learning techniques can be used to derive geometallurgical categories, or classes, from multiscale, multiresolution and high dimensional measured rock properties. Subsequently, geostatistical simulations of these classes can be applied to obtain multiple equiprobable realisations that define the layout of the geometallurgical classes at unknown locations between boreholes, or domains. In-turn these realisations can be used quantify the uncertainties in the location of boundaries between different domains. The development of a workflow for defining geometallurgical domains and later geostatistically simulating them across the Orebody H; a complex stratabound Bedded Iron Ore deposit located in Western Australia’s Pilbara region is demonstrated. This could be used to identify zones of high uncertainty where collection of additional data might help mitigate or minimise risks and in turn improve forecast production performances.

Mar 22, 2022