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By G Simpson, S Dressler, A E. Levett

Tailings storage facilities often represent a mining operation’s most significant liability, posing serious environmental, social and safety risks. Almost all mining operations dispose of wet tailings (Valenta et al, 2023), which represents a risk of failure due to the potential for a rapid strength reduction of the unconsolidated materials leading to static liquefaction and subsequent dam wall failure. As a waste stream, tailings disposal, decommissioning and relinquishment aim to be inexpensive processes, ruling out many highly engineered solutions. Advantageously, tailings consolidation does not need to be immediate, opening the door for relatively passive, inexpensive consolidation methods that aim to gradually increase the strength of tailings over extended periods (ie years). In this paper, we present the prospect of novel in situ tailings stabilisation, learning from studies that have investigated the most erosion-resistant landforms on Earth.

Aug 2, 2023

By Beattie T

For many years explosive sensitized explosives were assessed using the ballistic mortar. The standard test used lOg of explo- sive initiated with a detonator. Over the past 30 years many non- explosive sensitized explosives and blasting agents have been developed. Most of these new explosives and blasting agents cannot be tested in the ballistic mortar as they are not initiated by a detonator. It is also known that all explosives have a criti- cal diameter. When the cartridge diameter is less than the criti- cal diameter a stable detonation cannot be produced and the explosive fails to propagate. For many blasting agents the criti- cal diameters are greater than 50mm and such large diameters cannot be tested in the ballistic mortar. The underwater test allows explosives to be tested in diameters greater than the critical diameter and to be adequately initiated with suitable boosters. The effects of the explosive on the water are easy to measure and the test provides a safe, convenient and reproducible means of assessing explosive performance. The reaction products are allowed to expand to a low final pressure. The underwater test can therefore be used to give a measure of the total expansion work of explosives. The detonation of an explosive induces a shock wave in the surrounding water. The profile of the shock wave can be meas- ured 3-6m from the charge and the energy in the shock wave cal- culated. Measurements over a range of distances show that the shock wave is attenuated as it travels through the water and the attenuation is different for each explosive. This makes it difficult to estimate the energy dissipated in the water between the charge and a single gauge. The reaction products continue to expand and displace water. The bubble continues to expand until the kinetic energy of the water is zero. The gas pressure in the bubble is now lower than the hydrostatic pressure and the bubble radius is a maximum. The higher external hyrdostatic pressure causes the bubble to implode. The bubble energy is the work done displacing the maxi- mum bubble volume against the hydrostatic pressure and can befound from the bubble period. It is not always easy to find a large enough pond for the bubble to expand undisturbed by the water surface and the containing boundaries. This makes it difficult to determine the bubble energy accurately in shallow Ponds.

Jan 1, 1988

By Z Terzic, M Schult, D Chu, S Macklin

The East West Link road tunnels are proposed to provide a connection between the CityLink toll road and the Eastern Freeway north of the Melbourne CBD. The alignment passes from Moonee Ponds valley beneath the Upfield Line railway cutting, Royal Park, the historic Melbourne Cemetery and beneath Alexander Parade rising to an eastern portal at Hoddle Street. The western (Royal Park) part of the alignment passes through the folded and faulted Silurian Melbourne Formation, which has been subjected to deep weathering since the Triassic.The Melbourne Formation in the Royal Park area is mainly characterised by interbedded sequences of siltstone and fine-grained sandstone. The beds are often graded and a clear boundary between the siltstone and fine-grained sandstone rock can be difficult to distinguish. Variation in lithology and the presence of structural geological features such as folds and faults have resulted in an irregular weathering profile within the Silurian rock; nonetheless the formation typically becomes less weathered with depth.Due to difficulties in obtaining reliable laboratory strength and stiffness relationships with weathering grade, in situ testing methods such as downhole shear wave velocity and high-quality pressuremeter testing are a useful aid to assessing appropriate geotechnical parameters for design.This paper presents an analysis of the variation in shear modulus of the Melbourne Formation, determined at small-strain (from downhole seismic data) and at ‘engineering scale’ strain (from pressuremeter tests) for extremely weathered (XW), highly weathered (HW) and moderately weathered (MW) rock. Estimates of small strain shear modulus (Go) obtained a range between 400 to 3400 MPa for these weathering grades. By comparison against the pressuremeter test data, reduction factors to be applied to these Go values to estimate shear moduli at engineering strain levels typically range between 0.10 and 0.35.The downhole geophysics undertaken in the Royal Park boreholes also suggests that there is an inversion in velocity between approximately 15 and 27?m depth below the top of the formation. This is thought to be related to the effects deep Plio-Pleistocene weathering, iron cementation of joints and increasing frequency of ‘non-healed’ joints in the transition from MW to slightly weathered (SW) rock.CITATION:Macklin, S, Schult, M, Terzic, Z and Chu, D, 2014. Strain-dependent stiffness of the weathered Melbourne Formation, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 179–188 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By Linge H. G

The effect of sodium pyrophosphate and several polyacrylate deflocculants (Freevis 502, 528, 529 and 532; and Maxfloc 1015) on the gold loading on Calgon GRC22 and Norit R035l5 carbons was tested and found to be insignificant in a pulp free enviroument. These deflocculants can therefore be used in plants processing viscous gold pulps without fear of fouling the carbon.

Jan 1, 1990

After a short presentation of the Division of Mining at the Royal Insti- tute of Technology, Stockholm, Sweden, the author presents some of-the fill research carried out at the Division. Literature surveys and testing methods and equipment are described. The use of flocculants' in hydraulic filling has been tested both in laboratory and in mines and the results are very promi- sing. Finally compressibility investi- gations and some finite element calcu- lations are presented.

Jan 1, 1973

By J A. M Luz, A T. Bernardes

HukkiÆs law is an empirical law, which does not take into account several events of energy loss during the fragmentation processes. Since experimental results are very difficult to obtain, for a large range of fragment sizes, the verification of the law is very difficult. The relation between fractures and fragmentation processes with fractal geometry was proposed some decades ago. Empirical laws known in this context show basic features of fractal geometry, mainly self-affinity and power law behaviour. Thus, in this work a model was developed to simulate the fragmentation process and to check the relation between energy consumption and fragment sizes. The model is represented on a regular lattice. Links can represent pathways for fracture processes. The events of fragmentation have energy given by a probability distribution function. In the model there is no mass loss. Propagation of fractures occurs as self-avoiding random walks on the regular lattice.

Sep 26, 2011

Large deposits present computational challenges to todayÆs commercial orebody modelling systems that are based on conventional block models. We describe a system that is specifically engineered to model and visualise large deposits. Central to the system is linear octree encoding of conventional block models and real-time conversion of three-dimensional (3D) meshes to linear octrees. We provide both methodological treatment and practical experience in implementing such a system. A commercial implementation is also presented to demonstrate the validity of the approach.

Sep 26, 2011

By M Burdick, A Harding, M Krulc, M Chappell

Substantial schedule advantages can be made on projects if cross-passage construction can occur at the same time as tunnel boring machine (TBM) operation with little or no impact on TBM logistics. However, this approach can prove difficult to achieve with many of the more cost-effective means of supporting the segmental lining during cross-passage break-out. This paper discusses the constraints and shortcomings of conventional approaches, and describes how a cost-effective solution involving a shotcrete shell and opening constructed inside the segmental lining was designed and constructed to deliver cost and time savings on Seattle University Link contract U220.The paper explains the spatial and schedule constraints on the TBM tunnelling and cross-passage construction, and how a shotcrete solution was arrived at in preference to traditional approaches. As the solution was novel the design had to be robust, and the paper explains how this was achieved through a combination of 3D finite element modelling and closed form solutions. Following a description of the trials to verify that the structure could be demolished post-cross-passage completion, the paper describes how the shell solution was constructed, used and demolished safely to leave the lining surface in a clean and undamaged state fit for tunnel operation.CITATION:Harding, A, Chappell, M, Burdick, M and Krulc, M, 2014. Opening supports to segmental linings – a novel shotcrete support solution, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 267–274 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By S J. Henderson

Pumped co-disposal of coal processing waste was promoted in the 1990-2000s as a low-cost highperformance alternative to tailings dams. In particular it would avoid high up-front capital for rejects trucks and dam embankments, and would produce a combined waste deposit with better geotechnical properties than either coarse rejects or tailings. Overall, the promise was not delivered; in particular, upon discharge the waste segregated by size, and operators responded by moving the coarser waste to contain the finer waste. In consequence, not only did design analysis lag behind construction, but some of the initial expectations persisted with the result that analyses did not fully represent what was occurring on the ground. After more than twenty years inspecting, designing and tending Co-Disposal Areas (CDAs), it is apparent that they are essentially upstream constructed tailings dams with some more favourable aspects but also a few unique quirks. Although waste management technology has moved on somewhat, the high cost of changing CHPP waste circuits means that most mines with pumped codisposal will continue to discharge mixed waste slurry into CDAs. It is therefore worthwhile to share some lessons in the hope of promoting sounder design, operation and rehabilitation. These include: • Discharged waste does not form a homogeneous wholly competent deposit but instead comprises materials ranging from sandy gravel to silty clay with the distribution determined by movement of the discharge and decant structures; • CDAs circulate and contain a lot of water; • As a result of the first two points, some areas of the CDA comprise saturated fine waste that is no different from tailings and, like tailings, often behaves in an undrained manner; • Seepage is inevitable and desirable because strength improves as water is removed. However, stability is strongly impacted by pore pressures and in design these need to be rationally rather than optimistically considered; • As CDAs are built to about 40m or higher, strength-deformation characteristics of the foundation become more important; • Even if geomechanically stable, CDAs will need covers to prevent salts and acids from reaching the surface; and • Erosional stability of the cover material(s) will probably dictate maximum slopes for rehabilitation.

Jul 1, 2021

By M Bellamy

The DeGrussa copper deposit was discovered by Sandfire Resources in April 2009. Construction of the 1.6 Mt/a concentrator, open pit and underground mining operations commenced in March 2011 with first concentrate production achieved in October 2012. Over the next ten years, DeGrussa grew to include both the DeGrussa and Monty underground mines, establishing itself as one of the world’s premier copper producers with total production of 663 000 t of contained copper by the time the mine closed. Final ore was trucked from Degrussa on 5 October 2022. This paper examines the mine closure experience from both a planning and operational perspective. The paper provides an overview of the site’s mine planning process including the factors involved in determining the end of the mine life and how this was tracked and communicated in the lead up to the end of mining operations. It will also look at some of the specific operational aspects involved in maintaining steady state production all the way through to the last day while facing increasingly challenging conditions. These factors, along with the external factors faced by most of the industry such as labour shortages and COVID related disruptions, contributed to making it an interesting journey to the end of operations at DeGrussa.

Mar 29, 2023

By H Zhai, C Zhang, I Canbulat, K Yui

Sedimentary rock is a lithology that is commonly encountered in mining practices. Their properties, especially the resistance against weathering, are often of critical importance to long-term engineering stability due to their ubiquitous existence on the earth’s crust. The weathering of rocks is a complex process that involves physical degradation, chemical and biological erosions. In this study, the impact of physical weathering on four common sedimentary rocks, namely sandstone, siltstone, limestone and shale, are simulated in the laboratoryoratory environment taking into consideration the impact of preservation condition, temperature and time. In order to optimise the design of the experiment, Taguchi’s design of experiment method is implemented based on the L16 orthogonal array and selected simulation conditions. The weight and dimension variation, fracture intensity, slake durability, and uniaxial strengths of specimens are then tested to quantify the impact of weathering under various conditions. The results indicate that weathering significantly influences the strength of shale, siltstone and limestone but not sandstone. The impact of weathering on dimension variation is insignificant. For soft rocks, most physical weathering took place after second cycle of simulation, resulting in strength reduction up to 100 per cent (disintegration) but generally in a range from 28 per cent to 32 per cent. Additionally, time is the most important factor contributing to the physical weathering of weak rocks, followed by residual, preservation conditions and temperature. Last but not least, some shales, depending on the content of clay minerals, tend to develop significant fracturing or even disintegrate under the influence of weathering.

Nov 29, 2022

By R Austerberry, S Green

The discovery of the Cuffley Lode at Mandalay Resources Costerfield Operations provided an opportunity to extend mine life via mining the offset depth extension of the previously worked Alison Mine. Access from the existing Augusta Mine placed the initial Cuffley underground workings at approximately 250 metres depth from surface. As the new orebody transitioned towards production, a secondary means of egress needed to be established. The depth of the initial capital development presented a challenge in establishing a secondary means of egress that could be confidently relied on. The availability of land to locate a surface shaft collar further reduced available options and geotechnical drilling further limited suitable shaft locations. Time limiting factors such as permitting and having a secondary means of egress in as soon as possible, further highlighted that an innovative secondary means of egress was needed. A consideration of using an emergency gig lowered by a suitable sized crane supplied by an external crane contractor was investigated and found to be a suitable outcome. This Emergency Gig was deployed via the Cuffley Return Air Raise. When trialled, the emergency gig was found to provide a reliable, repeatable extraction method with an acceptable level of risk. Issues discovered during such trials further improved the process to a point where this extraction method became the adopted secondary means of egress for additional lodes that existed at depth. When assessing possible methods of secondary means of egress, the use of a third-party crane and custom designed and fabricated emergency gig should not be discounted. Where a crane can be sourced within an acceptable timeframe, the emergency gig extraction method provides a reliable safe and cost-effective means of secondary means of egress, especially when multiple shafts are to be developed. Local laws may negate the ability to employ such a system, although it is believed with good communication and well-constructed risk assessments, this system can be safely deployed.

Mar 15, 2021

By J Maxlow, M J. Woods, M P. Sandy

The Newcrest Mining Limited Telfer operation comprises both open pit and underground operations producing gold and copper. The underground operation is made up of three production areas, the sublevel cave (SLC), M Reefs narrow vein open stoping and Western longhole open stoping areas. With stoping situated on the abutments of a mature and active sublevel cave, the interaction between mining areas is often complex. This is particularly evident in the M Reefs orebodies with high levels of extraction in all four reefs, and reliance on pillars to maintain local and global stability. A key concern was the potential for a cascading pillar failure to develop and rapidly progress through the M Reefs stoping area. The monitoring plan needed to capture any change in overall stability and identify if deformation was caused by pillar failure within the M Reefs and hanging wall closure, or shear on the reefs caused by SLC influence.

Nov 29, 2022

By K T. Mandisodza, T J. Cartledge

The principal objective of Geotechnical Engineers supporting operating mines is to provide safe working conditions and ensure that pit designs are geotechnically optimised to site conditions and pre-defined stability requirements. Pit slope designs are delivered in advance of pit excavations. Making changes to these designs is usually slow to enact and involves a layered sign-off before implementation, leading to unwanted delays in their adoption and subsequently increased production pressures. When unexpected ground conditions are encountered during the mining process, or short-term mining schedule requirements demand it, changes to these designs may not be easily feasible in certain situations. It is when these scenarios arise that Geotechnical Engineers need to be proactive and consider unconventional options to deliver safe operating conditions while satisfying short-term requirements to the mine schedule. Essentially, the geotechnical short-term strategic designs double-pronged approach supports the mine schedule while providing safe conditions and minimising geotechnical risks for people and equipment. Common short-term strategic geotechnical designs include; slope buttressing, over-steepening cut slopes to increase reserve recovery through unplanned or emergency cutbacks, and accepting risk threat and operating under unstable slopes. When implementing strategic design options, the Geotechnical Engineer must consider the broader implications for such designs. They must think of the plan’s long-term effects on the mine schedule and pit wall stability. Initiating aggressive designs to recover additional reserves to satisfy a short-term scheduling demand could result in-pit wall instability or suboptimal pit layout. Before and during the implementation phase, the Geotechnical Engineer must communicate and engage with relevant stakeholders to ensure that the plan is executed accordingly and geotechnical risks are effectively managed. Proactiveness to ground response and implementation of risk management strategies will improve safety performance and optimise mining schedules.

Jun 22, 2022

By G McCullough, B Mutsaers, J Jessop

"*This is an abstract only* Geometallurgical initiatives have demonstrated considerable value to operations that have trialled them. However, it is extremely difficult for these initiatives to become properly embedded into the operations and for that value to be realised on an ongoing basis.This paper will explore some of the historical reasons why this is the case. Some of these reasons include the limited tools available to manage an integrated operation. These, in turn, have resulted from poor communications infrastructure, inadequate sensor capability and the way technical mining software has evolved over the last 30 years.This paper will then investigate how the evolution of technology in recent years can help overcome these constraints and compare progress with similar industries.CITATION:McCullough, G, Mutsaers, B and Jessop, J, 2013. Obstacles to embedding geometallurgy decision-making into operations and how to increase maturity of this critical capability, in Proceedings The Second AusIMM International Geometallurgy Conference (GeoMet) 2013, pp 139-140 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Sep 29, 2013

By C Wu, H Chen

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.The Halasu porphyry copper belt, located in the East Junggar basin bounded by Chinese Altay to the north and the Tianshan mountains to the south in the Central Asian Orogenic Belt, is one of the major porphyry copper belts in Xinjiang province, north-west China. Combined with previous studies in this area, the magmatism can be divided into three periods: pre-mineralisation activity of 390 Ma syn-mineralisation activity of 380–370 Ma post-mineralisation activity of 360–330 Ma.Through the comparison of zircon chemistry from ore-bearing and barren syn-mineralisation intrusions, negative correlation was identified between Ti-in-zircon temperatures and oxygen fugacity, corresponding to the fact that late-stage syn-mineralisation granitoids contain high water content, high oxygen fugacity and low temperatures with higher mineralisation potential. In addition, the relative low initial 87Sr/86Sr ratios, high eHf(t) and eNd(t) values and mantle Pb isotope characteristics in this study support that the magma forming these intrusions was probably derived from juvenile crust generated during subduction-accretionary processes.CITATION:Wu, C and Chen, H, 2015. Zircon trace elements and Sr-Nd-Pb-Hf isotope systematic of the Halasu porphyry Cu belt, north-east Xinjiang, China, in Proceedings PACRIM 2015 Congress, pp 637–640 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

By D Olwagen, C Stanton, J Gerber

From December 2013 to February 2014 the Southern Middleback Ranges magnetite concentrator went through a successful optimisation process that included the installation of extra grinding power to treat a wider range of ore types. After the initial improvements, sampling surveys were conducted to identify the mineral deportment through the concentrator. Samples collected during the survey were analysed using X-ray fluorescence, quantitative X-ray diffraction and QEMSCAN™ to cross-validate the analysis. Certain streams were also put through a laboratory-scale Davis Tube Recovery washing process to produce clean concentrates for analysis. The QEMSCAN™ analysis identified various metallurgical characteristics (mineral association, particle sizes, grain sizes, particle densities, etc) and these were evaluated for each separation and comminution stage to both understand the processes involved and identify opportunities for improvement. Key findings from the investigation indicated the importance of understanding the elemental deportment of target elements throughout the various minerals. The standard practice of tracking iron deportment through assay provided misleading results on losses to tail through the plant. The investigation provided insight into both wanted and unwanted minerals and the efficiency of each separation stage. The efficiencies of separation are critical due to their impact on downstream capacity, and the investigation provided insight into where opportunities exist to extract more benefit. The findings of the geometallurgical analysis have been implemented on the concentrator, and improvements in the rejection of non-magnetic minerals have been seen.CITATION:Gerber, J, Stanton, C and Olwagen, D, 2015. Using geometallurgy during process optimisation activities at the Southern Middleback Ranges magnetite concentrator, in Proceedings Iron Ore 2015, pp 561–566 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

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

By C E. Woolley, H Jebaliya, J Foster

The East wall of the Kalgoorlie Consolidated Gold Mines Fimiston Open Pit (KCGM Superpit) has a history of wall instabilities impacting mining operations; the most significant of which occurred in May 2018, when more than 1 Mt of rock dislodged over six, 30 m high bench stacks and impacted the pit floor. Since 2011 approximately 1.250 Mt of material has fallen from the East wall at Fimiston Pit across three failure events (2011, 2018 and 2020). Each failure has been associated with major structures intersecting the pit walls: the Fiji Fault, the Australia East Secondary Splay Fault and the EWD3 Fault. In each instance the trigger for failure has been transient pore pressure in the pit walls. Northern Star will mine a cut back behind the failure area over a vertical distance of 180 m. Cut back mining will include the extraction of a remaining in situ wedge, which is assessed as kinematically able to fail, and a subvertical failure backscarp in Stage 1. A substantial amount of rill material from the 2018 and 2020 failures will be extracted in Stage 2. This paper presents the methodology in use to mine Stage 1 of the cut back, safely, through this potentially high-risk area, detailing the specific mining methodology employed, the controls put in place and the monitoring required. Day-to-day monitoring will be undertaken using the already installed slope stability radar and will feed into a daily assessment of activities which may be undertaken in the cut back area. Initial activities will focus on eliminating the potentially unstable wedge and vertical backscarp with use of innovative drill and blast techniques/products and the extensive use of remote capable equipment to limit personnel exposure.

Jun 22, 2022

By R Marchant, D Willingham

"Predictive maintenance (also known as PHM or equipment ‘health monitoring’) refers to the intelligent monitoring of equipment to avoid future equipment failures. In contrast to conventional preventive maintenance, the maintenance schedule is not determined by a prescribed timeline; instead, it is determined by analytic algorithms, such as machine learning, using data collected from equipment sensors and/or via simulation.Predictive maintenance offers the following benefits for operators and equipment manufacturers:reduction of equipment downtime by identifying issues before failure, thereby enabling convenient scheduling of equipment service and extending equipment lifetimeautomatic determination of the root cause of the failure, enabling appropriate service to be performed without utilising resources to determine a diagnosis avoidance of costs of unnecessary maintenance and unexpected failures improved safety and product quality.Algorithms and data are critical to predictive maintenance success. Sensor data preprocessing is performed using advanced statistical and signal processing techniques. In the case that data isn’t available for the full range of operating modes, operating scenarios can be simulated. Machine learning techniques are then used to estimate equipment health. Once tested, predictive maintenance algorithms may be operationalised in an IT environment such as a server or cloud. Alternatively, algorithms may be implemented in an embedded system directly on the equipment, allowing for faster response times and significantly reducing the amount of data sent over the network.In this paper, we use both historical and simulated data of the plant under various modes of operation including run to failure, and we then leverage machine learning techniques in MATLAB to estimate degradation and remaining useful life. This technique, of combining both simulation models and machine learning, in the areas of predictive maintenance and equipment health monitoring has been adopted by Safran, makers of aircraft jet engines, since 2007. They now have over 160 modules developed (Lacaille and Aurelie, 2015).Citation:Willingham, D and Marchant, R, 2016. Predictive Maintenance Using Simulation and Machine Learning, in Proceedings 13th AusIMM Mill Operators’ Conference 2016, pp 279–284 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Oct 10, 2016