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By B K. Hebblewhite, G Sharrock

The strength and deformation properties of a rock mass are important parameters influencing the design of civil and mining excavations or structures. The mechanical behaviour of jointed rock masses are controlled by the characteristics of discontinuities and the strength of intact rock bridges between discontinuities. To date, analytical, empirical and experimental methods have not captured the key mechanisms controlling the mechanical properties of actual rock masses with non-persistent joints. The emergence of the synthetic rock mass (SRM) in 2007 provides a promising approach for this purpose. In this paper a rock mass with non-persistent joints is analysed with the SRM model based on PFC3D. The influence of joint geometrical parameters on the uniaxial compressive strength (UCS), rock mass deformation modulus (Em) and failure mode is studied. Joint parameters include joint orientation, persistency, spacing and step angle. Prismatic numerical samples with dimensions 300 mm × 150 mm × 50 mm were generated and a sensitivity analysis of each joint parameter on UCS and Em was undertaken. The results show that of the parameters tested, joint orientation has the greatest influence on UCS. Minimum UCS occurs when the angle between the major principal stress and joint surface is approximately 60°. The joint step angle was found to have a significant effect on failure mode and a joint step angle of 90° is the most favourable joint orientation for step-path failure. The importance of joint step angle is highlighted in the discovery of a failure mode bifurcation point at joint step angles of 60° and 90° for joint orientations of 75° and 90°, respectively. For these parameters the failure mode transitions from block rotation to a new failure mode where the coalescence of cracks results in the formation of new small regularised blocks.

Sep 26, 2011

By B Oostendorp, R van der Merwe, P

In order to assess whether polysaccharide depressants are strongly or weakly and reversibly bound to the surface of talc, a series of experiments was conducted on New York talc in which the floatability of the talc in a microflotation cell was determined. The talc was conditioned in solutions of carboxymethyl cellulose (CMC) or guar gum in 10-2 ionic strength Ca(NO3)2 or Mg(NO3)2. The talc was then washed with four successive aliquots of water, or cation solution, to try to remove the polymer and the flotation response of the talc was assessed. CMCs of different charge (DS) were used to assess the effect of charge on the strength of bonding. The results show that CMC and guar gum could be removed to a large extent from the talc surface by washing with water (the floatability was restored), however very little could be removed from the surface by washing with cation solution. The higher charge CMC was easier to remove from the talc planes in the absence of cations than the lower charge CMC. Thus CMC bonding to talc has been shown to be irreversible or very slowly reversible only if cations are present, implying that cations are necessary to keep the polymer bound to the surface of the planes to effect depression. The presence of ions in solution also had the effect of maintaining surface coverage of the talc by guar gum.

Jan 1, 2005

By G Hill, D Grant, M Tyler

Located approximately 570km NNW of Adelaide in South Australia, the Olympic Dam mine (OD) is the world’s fourth largest remaining copper and gold resource and the largest uranium resource. Discovered in 1975 and going into production in 1988, the operation consists of a fully vertically integrated underground mine, mineral processing plant, copper smelter and refinery, as well as associated infrastructure. BHP achieved production of 203,000 tonnes of copper cathode plus associated by-products in financial year 2016. The immense size and high-grades of the Olympic Dam resource offer a range of growth pathways, making closure timing estimation and planning a challenge. Current estimates put the OD resource at approximately 79 million tonnes of copper. Major factors influencing the closure timing estimation, as a result of the large resource and grade tonnage profile, include the mining method that may be used and the downstream processing method, ultimately influencing such things as the total disturbance area and the extent of infrastructure to be demolished at the end of mine life. In addition, factors such as the mining and processing method and production rate have a direct impact on larger rehabilitation items such as the total number of tailings cells required.CITATION:Grant, D, Tyler, M and Hill, G, 2018. Olympic Dam mine closure planning process, in Proceedings Life-of-Mine 2018, pp 43–45 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 25, 2018

By J Meinhart, J Rodler, I Katolicky

The ever increasing number of vehicles is leading to slow-moving and even stationary traffic sitting longer in traffic jams over extensive city areas. This traffic situation causes a sharp increase in pollutant emissions from vehicles, and high levels of pollution usually result throughout the built-up area. Reducing the pollution level by using traffic routing measures to speed up the flow of traffic in the existing street network is only possible in exceptional cases.In many cases the only option for achieving a significant improvement in traffic conditions is to shift the traffic underground using a road tunnel or underpass. Such tunnel routes suck off the traffic from large sections of the city, thereby easing the overall traffic flow. Thus on the one hand it produces a sharp reduction in pollution levels in the area of the tunnel route, but on the other hand it can result in locally increased exhaust pollution levels from longer tunnel systems that require mechanical ventilation. The air extracted by the ventilation system is blown out into the atmosphere either directly through the tunnel portal, or via a venting tower. Pollution can therefore occur in the area surrounding such exhaust air outlets.Thus if a tunnel is planned in a city, then closer investigation is required of both aspects: the reduction in pollution in the area of the tunnel route thanks to relocating the traffic and easing congestion, and the increased short-range pollution around the tunnel portals (shafts).

Jan 1, 1999

By P Khalkho, M Singh

Rock masses when subjected to uniaxial or triaxial cyclic loading (eg in hydraulic running tunnels, during retrieval and injection of oil and gas from storage underground caverns and haulage roads), the material has a tendency to fail in fatigue. In order to design safe and reliable underground structures, the determination of brittleness under such loading conditions becomes a pre-requisite. Brittleness influences strongly the failure process and makes the rock mass behaviour complex under different tunnelling and mining activities. Brittleness Index is a term to quantify the brittleness feature of a specimen. In the present study, an attempt has been made to quantify the brittleness of jointed specimens using different brittleness criteria. The joints of the model jointed specimens were oriented at an angle of θ=15° normal to the loading direction, each having three different JRC’s=2–4, 12–14 and 14–16. The specimens were tested under triaxial conditions in incremental complete cyclic test scheme performed at displacement-controlled mode. Different brittleness criteria were used ie stress-strain dependent brittleness index, Young Modulus approach and energy-balance based mechanism. It was observed that energy-balance based mechanism which consider the post failure behaviour is more descriptive to reflect the whole variation of brittleness from sheer brittleness to ductility.

Nov 29, 2022

By B Zhou

Geophysical borehole logging, which measures various in situ petrophysical parameters, can be used not only for qualitative interpretation such as strata correlation, but also for geotechnical assessment through quantitative data analysis. It can play an important role for safe and productive mining operations. Here we provide various applications of geophysical logs such as the estimation of the strength of intact rock or unconfined (or uniaxial) compressive strength (UCS), automated lithological/geotechnical interpretation, geophysical strata rating and orebody delineation and grade estimation. These derived parameters could provide input to control of geological and geotechnical models. This could assist site geologists and planning and production geotechnical engineers to predict and manage mining conditions on an ongoing basis. Both conventional logs such as density, natural gamma and sonic, and less common logging data such as full waveform sonic and televiewer data are examined for different applications. Although the examples used here are mainly for coal mining applications, but they can be equally applied to hard rock metalliferous mining such as iron ore mining.

Nov 8, 2021

Gold mineralisation at Wapolu lies within an exposed arcuate zone at the decollement contact between a basement dome of high grade metamorphics and an overlying ophiolite sequence. This contact was originally a thrust fault which has since become a decollement zone for gravity sliding in association with basement doming. Hydrothermal models for the gold mineralisation postulate an epithermal system in which fluids were channelled up the decollement with boiling of those fluids causing hydrothermal brecciation and subsequent gold deposition. The alteration assemblages, fluid inclusion data and geochemistry indicate that the upper levels of the system are exposed.

Jan 1, 1987

By P Marianelli, J Theiler, B Beamish, A Spillman

The presence of reactive pyrite in waste rock contributes to the hazard of spontaneous combustion in emplacement facilities as it acts as an initiator of self-heating at low ambient temperatures. Organic carbon also present in the waste rocks acts as a fuel at elevated temperatures above 120°C and can lead to thermal runaway resulting in eventual ignition. A new laboratory test method (adiabatic incubation testing) is now available that can identify the presence of reactive pyrite and quantify the self-heating behaviour of the waste rock. McArthur River Mine has a waste rock profile that contains pyritic shale units, which have created spontaneous combustion events in the past. A systematic sampling and testing program is underway to characterise the spontaneous combustion hazard likelihood of the McArthur River Mine waste rocks to provide a sound database for future mine planning of the waste removal and emplacement. This paper presents some initial outcomes of this program and shows the leading practice in spontaneous combustion hazard assessment and management that has been adopted at McArthur River.CITATION:Beamish, B, Marianelli, P, Theiler, J and Spillman, A, 2018. Spontaneous combustion hazard assessment of McArthur River Mine waste rock, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 422–426 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By M I. Pownceby, J Manuel, S Suthers, A Poliakov, E Donskoi, N Ware

"The mining industry is constantly seeking methods for optimising the exploitation of mineral resources, such as iron ore, in a sustainable and eco-efficient manner for economic and social benefit. When faced with resources that have mineralogical or textural complexity, poorer grades or geological variability, it is particularly important to apply a comprehensive geometallurgical approach to the development of the mining operation, from resource definition through to processed product. Integral to this approach is the quantitative characterisation of representative samples across the whole orebody.A key factor that associates the geological characteristics of iron ores to their processing response is ore texture. While the classification of samples on the basis of chemical or physical properties alone is often not sufficient to predict their processing behaviour, classification and quantification of texture types can be effectively correlated to metallurgical performance in processes such as blending, beneficiation, pellet making, sintering and ironmaking. This paper describes some of the research conducted by CSIRO pertaining to the design and rationale of a texture-based classification system for Australian iron ores; some of the tools developed and used to apply such classification; and the application of the generated data to quantifying, modelling and predicting sintering behaviour and performance in the blast furnace.CITATION:Suthers, S, Pownceby, M I, Manuel, J, Ware, N, Donskoi, E and Poliakov, A, 2016. Geometallurgical Characterisation of Australian Iron Ores – from Ore to Processed Product, in Proceedings The Third AusIMM International Geometallurgy Conference (GeoMet) 2016, pp 351–360 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Jun 15, 2016

By H Zhang, S Li, J Song, Z Lv

In this paper, a method for extracting and refining metallic molybdenum using low-temperature ZnCl2- NaCl-KCl molten salt was proposed. The electrochemical behaviour of molybdenum ions in ZnCl2- NaCl-KCl molten salt was investigated in detail, and pure metallic molybdenum was collected on the cathode. The reduction and diffusion processes of Mo(V) ions in ZnCl2-NaCl-KCl molten salt were determined through a series of electrochemical methods. The diffusion coefficients and nucleation modes of Mo(V) ions were also studied, and electrolysis was conducted for a prolonged period at a constant current density. The results indicated that the electrode reduction of Mo(V) ions in ZnCl2- NaCl-KCl molten salt proceeds through a three-step reaction: Mo(V) → Mo(IV) → Mo(III) → Mo at 250°C. The Mo(V) → Mo(IV) reaction was reversible and diffusion-controlled, with a Mo(V) diffusion coefficient of 6.02 × 10-6 cm2 s-1. Additionally, the nucleation mode of Mo(V) ions was instantaneous nucleation. The products electro-deposited were confirmed of metallic molybdenum with a particle size of less than 1 μm.

Aug 21, 2024

By I Levy

At our Monkland Mine at Gympie, we operate a deep, narrow vein gold mine using hand held equipment, rail mounted haulage and narrow shafts. This is in many respects the old-fashioned way and is well suited most of the orebody geometry exposed to-date. We have also commenced some long hole stoping and we use alimaks for some jobs. The heart of our particular mining style is the employment and retention of experienced miners with remuneration based on productivity. We do our planning/monitoring/supervision down to the level of daily individual productivity. In focussing on cycles per se, we have chosen not to talk about drill and blast cycles or cycles for mine development, stope preparation or drawdown and haulage. Instead we have stepped right back from the operation as presently run and have adopted a very broad view of the mining cycle. We will in this presentation intertwine the ebb and flow of, exploration, project sponsorship, development, production and cash returns to owners. The time line considered spans both history and predicted future.

Jan 1, 1998

By Wyborn L. A I, Idnurm M, Hinman M. C

Comparison of the Proterozoic Apparent Polar Wander Path (APWP) for Australia with the corresponding geology of northern Australia suggests that a number of discrete interplate tectonic events, manifested on the APWP as bends or inflections, may have controlled sedimentary basin evolution, ore fluid production and the timing of mineralisation. Similar features in the Phanerozoic APWP for the North American plate appear to correlate with major orogenic events, basin deformation, movement and 'entrapment' of hydrocarbons and minerals. Interplate tectonic events cause intraplate deformation which in turn controls the subsidence/uplift and sedimentation histories of the basins. Interplate events are thus responsible for creating, deforming and destroying sedimentary basins and the associated petroleum and mineral systems. The basins of northern Australia show remarkable similarities in the successions of volcanic and sedimentary deposits. Unconforrnities of regional or sometimes only local extent have been mapped between the major sedimentary sequences and it is predicted that interplate tectonic events corresponding to bends or inflections on the APWP directly reflect the processes that have produced these widespread unconformities. These processes are also likely to have controlled the geometry and character of the fluid migration pathways and hence the mineralising events. Palaeomagnetic studies of Proterozoic rocks in sedimentary basins provide a tool for predicting the timing of regional mineralisation events, particularly for low-temperature mineral systems. The techniques, when coupled with systematic regional basin analysis, using petroleum exploration techniques, may identify a number of new mineral 'plays' in northern Australia. Prominent inflections in the APWP occur at approximately 1700, 1670, 1650, 1600, 1540, and 1480 Ma. Each of these may be related to a regional compressional deformation, important mineralising event, or significant change in style and type of sedimentation. Most appear to be associated with magnetic overprints. Some of the inflections between 1400 and 540 Ma may also mark significant events in the evolution of Meso- and Neoproterozoic basins. Further work is required to correlate inflections in the APWP with alteration events in order to understand their regional significance.

Jan 1, 1994

By K Nakashima, K Aya, T Sumita, N Saito

Electro slag remelting (ESR) is one of the methods used to produce high-cleanliness steel. In the ESR method, the product steel electrode is immersed in flux, and the electrode is melted by the Joule heat of the flux generated by high current. CaF2-based melts are mainly used as fluxes, but the electrical conductivity of CaF2-based melts varies widely among researchers and measurement methods. Therefore, this experiment aims to measure the electrical conductivity of CaF2-based melts based on the van der Pauw-Ohta method, which does not require the cell constant that is a fundamental error factor in electrical conductivity measurement at high temperatures. The measurement temperature was set at 1450–1600°C, and dehydrated Ar flowed through the furnace at 200 mL/min. Electrodes were fabricated by Pt-30mass per cent Rh alloy, and the electrodes were connected to an impedance analyser using a four-terminal probe. The electrodes were immersed in the melt, and the impedance and phase angle were measured by AC frequency sweep (50 Hz to 200 kHz). The electrical conductivity was then calculated by utilising the impedance’s real part values when the impedance’s imaginary component was zero. The electrical conductivity showed a positive temperature dependence. The electrical conductivity of 60(CaO⋅Al2O3)-40CaF2 melt increased with increasing temperature but was found to be roughly one-third of those of the previous studies. In the conductivity measurement of 60(CaO⋅Al2O3)-40CaF2 melt, the AC frequency with a phase angle of 0° was found to be different depending on the temperature and immersion depth. By sweeping the frequency, the impedance at the phase angle of 0° can be obtained, which enables us to measure the electrical conductivity more accurately.

Jun 19, 2024

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 Lawson F

Chrome chemicals are commercially produced by the alkali roasting of chromite ores with sodium carbonate. Results of tests conducted in a laboratory furnace indicated that the sodium carbonate reacted rapidly with part of the gangue material to form a metastable intermediate that later reacted further with the chromite. For the conditions used, the recovery of water-soluble sodium chromate was able to be described empirically as yield % = a tn with a = 0.24 T - 241.3; n = 3.90 - 3.12 × 10-3 T and t is the reaction time in hours.The major rate limiting step in the overall reaction sequence appears to be the rate at which oxygen can get to the reaction sites across the liquid film coating the solid reactants.Sodium sulfate alone was found to be an unsatisfactory source of alkali for reaction with chromite. However when limestone also was added in quantities sufficient to allow the reaction CaCO3 + Na2SO4 + H20 ? Ca SO4 + 2NaOH + CO2 to take place, the results obtained were comparable to those found when sodium car-bonate was used.For chromite particles in the size range -124 + 105 µm, the use of stoichiometric excess of sodium carbonate did not appear to increase the yield or the reaction rate significantly. However, with smaller sized particles, - 53 µm, increased yields of water-soluble chromate were obtained when roasted with more than the theoretical quantity of sodium carbonate.

Jan 1, 1984

By E Forbes, G V. Franks

"This study investigates the dual function of a temperature responsive anionic co-polymer of poly (N-isopropyl acrylamide) (PNIPAM) as a selective flocculant/flotation collector. PNIPAM is used for separating hematite from 50:50 mixtures of hematite and quartz, at a variety of particle sizes. The performance of PNIPAM in this system is compared to that of conventional flotation collectors: sodium oleate and sodium dodecyl sulfate. The results of the study demonstrate that anionic PNIPAM used at 50¦C (above the lower critical solution temperature (LCST)) is the most effective flotation collector for hematite particles in the size range between 10 and 20 ¦m. This is attributed to the increased probability of both particle/bubble collision and particle/bubble attachment through the formation of hydrophobic hematite aggregates. Anionic PNIPAM used at 50¦C also produced the highest hematite recoveries for very fine hematite particles (circa 1 ¦m). However this recovery was completely unselective. This lack of selectivity is partially attributed to the activation of quartz particles by PNIPAM, but is thought to mainly occur as a result of entrapment of quartz particles within the matrix of hematite aggregates.CITATION:Forbes, E and Franks, G V, 2013. Selective separation of hematite from quartz by flotation using a temperature responsive polymer, in Proceedings Iron Ore 2013, pp 381-390 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Aug 12, 2013

By Grobler H. P, Chitombo G. R

Production blasting of Dc Beers Consolidated Mines Limited, Koffiefontein and Finsch Mines involves both uphole trough rings of 9 to I I holes and near vertical 360 degree compound rings of 42-54 holes. The rate of production from these stages is dependent upon being able to achieve a specified fragmentation size range and this has driven the derivation of blasting practices to consistently achieve this target fragmentation. At the Dutoitspan Mine, in Kimberley, where mining of the kimberlite pipe is by block caving, 100 per cent extraction of the undercut level by ring blasting is essential. If this is not achieved, pillars are formed which not only inhibit the efficient initiation of the caving process, but also concentrates load onto the extraction level, causing damage to draw points and pillars. These two case studies demonstrate the importance of achieving optimum blasting performance for downstream mining efficiency; ie fragmentation for increased productivity at Koffiefontein Mine and 100 per cent undercut extraction for efficient initiation of the caving process at the Dutoitspan Mine. The case studies also serve to highlight the long road towards blast optimisation taken by De Beers Consolidated Mines Ltd (Koffiefontein. Finsch, Premier and Kimberley Mines) since 1989.

Jan 1, 1995

Based on a principle developed at a South African Mine, the CSIR developed a device with which the alignment of guide rails in mine shafts could be measured. Originally the technique could only be used to obtain guide misalignment values at the bunton sets. At the time this was considered adequate since it was assumed that guide realignment could only be done at the support points anyway. The technology was developed further and now it is possible to obtain æcontinuousÆ guide profiles from the measurements. Software was developed with which a guide realignment schedule can be drafted and the shape of the realigned guides can be predicted. A measuring system based on this technology is being used to conduct guide alignment measurements in shafts. The data is then analysed and a realignment schedule is recommended in consultation with the mine. Such a schedule may be prioritised so that the worst sections in the shaft are dealt with first. The measurement hardware and analysis software are described. Examples are presented that illustrate the principles and highlight measurement errors. A case study illustrates measurements recorded in a newly equipped shaft. A repeat measurement, 18 months later, shows the effect of recommended realignment as well as the change in guide alignment over this period.

Jan 1, 2005

The need to solve the problems associated with spontaneous combustion, system of ventil- ation and methane drainage in gassy coal mines has brought about the development of mining and degassing methods which has made possible up to 80% gas recovery in retreating longwalls. Beneficial results also were obtained mostly in the double or multiple-entry systems, but for single-entry systems and for a seam thickness exceeding 3 m, gas recovery rate is still very low. With some single-heading systems, such as those where a return roadway is not maintained in the goaf behind the face line, a new methane drainage technology is practiced. Attempts were made to extract methane from roof holes drilled from offsets in the ribside of the longwall block. The inclinations and lengths of the boreholes were planned and designed on the basis of the geological and mining condit- ions encountered at the time and every second hole was terminated precisely at the point where the previous hole intersected the immed- iate roof goaf area above the face. There are mathematical relations approp- riate to the design of the above drainage systems to give optimum methane recovery under the given conditions. Some examples of drainage have reached 87% recovery and have attained 94% CH4 purity.

Jan 1, 1982

Giving the keynote address in the final session of a conference dealing with closely related topics has a disadvantage in that much of what can be said has been said. It also has an advantage, however, because it presents the speaker with the opportunity to integrate and analyse the material presented by the various speakers. I would like to look to the near future in Aust- ralia and the United States of America, to the risks, problem areas, and changes of a rapidly evolving post-industrial era-an era we are begin- ning to experience where industry no longer `calls the tune'. We miners have been quick to point out and emphasize, that ours is a `high-risk' industry in the world of business and commerce. Yet, clearly those who have survived, and been successful, have learned to anticipate and cope with risk and change. This ability has been a distinguishing feature of the industry's leaders who, in market studies and commodity selection, exploration and development, mine planning, metallurgical pro- cessing, and general administration and operation 1. identify areas of risk or inevitable change, 2. analyse, test and quantify those factors of risk or change, and 3. design methods, systems, equipment to elim- inate, moderate, or control or economically compensate for predicted risks or changes.

Jan 1, 1978