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By T Napier-Munn, E Louwrens, L Keeney

Geometallurgical characterisation of ore deposits is accepted practice in some parts of the mining industry today. Its primary aim is to provide constrained inputs that reflect inherent geological variability and its impact on metallurgical performance for the deposit. Geometallurgy improves project value because it suggests more valuable alternatives for scheduling and processing through an increased knowledge and understanding of the interactions of rock properties and extractive technologies. Lower project cost (both capital and processing) and improved recoveries are the result from closer tailoring of the mining and mineral processing strategies to the characteristics of the resource (Dunham, Vann and Coward, 2011). Tailings storage facilities (TSFs) can be seen as potential resources and it is argued that fundamental geometallurgical characterisation as applied in ore deposit characterisation should also be applied to planning the retreatment of TSFs. This paper will describe a research project at Julius Kruttschnitt Mineral Resource Centre assessing if geometallurgical principles and methodologies can successfully be applied to TSFs as they have been to primary deposits. The project is establishing a new standard method of tailings evaluation which will include a 3D spatial model of the tailings resource. Initial domaining of the TSFs was done using principal component analysis followed by k-means cluster analysis based on chemical assays from drill core samples. The subsequent characterisation of the drill core samples has involved chemical, mineralogical and metallurgical profiling, with a range of metallurgical tests being conducted on the samples. This characterisation step is followed by class-based analysis, predictive modelling and process performance domaining with the ultimate objective of establishing a 3D spatial model incorporating geochemical, mineralogical and metallurgical performance data. This approach, which takes into account processing performance permits a more realistic (as compared to doing limited chemical assays and metallurgical testing) economic evaluation of the potential of reprocessing the tailings material. It is believed that the approach is generic and can be applied to other TSFs being considered for reprocessing. The present case study has also established the gold, copper, magnetite and cobalt deportment for an iron oxide copper-gold deposit tailings resource.CITATION:Louwrens, E, Napier-Munn, T and Keeney, L, 2015. Geometallurgical characterisation of a tailings storage facility – a novel approach, in Proceedings Tailings and Mine Waste Management for the 21st Century , pp 125–132 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 27, 2015

By J Mauk, J Rowland

The Karangahake epithermal Au-Ag mine consists of two main lodes, the Maria and the Welcome/Crown hosted in Miocene andesites. Mineralisation is strongly constrained to major structures and is genetically linked to dynamic tectonic processes. Two main periods of faulting are represented in the deposit: 1. NE striking right-lateral/normal oblique linked spatially and temporally with the mineralising system, and 2. ESE striking right-lateral/normal oblique post-mineral faulting that displaces the lodes. Paleostress analyses performed on a limited kinematic data set indicate NW-SE extension during the formation of the vein system. Veins and lodes strike NNNE and accordingly contain a strike-slip component. The kinematics of vein formation at Karangahake is broadly consistent with that of other deposits within a NNE-trending belt of deposits. Oblique shear on deflecting structures will create zones of compression and dilation. Dilatant zones created on steep structures create fluid pathways potentially focussing large volumes of fluid from deep parts of the system into dynamic structures.

Jan 1, 2003

By Holcombe R. J, Dobos S. K, Little T. R

Blue amphibole-bearing rocks in the North D'aguilar Block of southeast Queensland occur either as relict pods and lenses within regionally extensive greenschist facies phyllites and schists or as blocks entrained in serpentinite-matrix melange. Epidote + crossite-bearing varieties predominate and formed under conditions consistent with underplating and high P:T metamorphism in a subduction-related tectonic environment. Neither lawsonite nor jadeite has been observed and metamorphic conditions are estimated at 380-4500C for pressures of 0.5-0.8 GPa. High P:T metamorphism occurred during the earliest stages of deformation and was superimposed upon protoliths of inferred Late Devonian - Early Carboniferous age, including mafic volcanics, tuffs and coarse volcaniclastic breccias as well as pelagic and henipelagic sediments, all of which have undergone varying degrees of over-printing to the greenschist facies. Greenschist facies metamorphism occurred during the second phase of deformation and was associated with the formation of mainly flat-lying or subhorizontal structures; it followed the cessation of subduction and occurred in response to either thermal relaxation during uplift or the imposition of regional heating induced by crustal thickening and/or synkinanatic granite emplacement. Uplift and cooling of the high P:T rocks was completed by 260-265 Ma and may have occurred in response to the same extensional processes which gave rise to the onset of rifting in the adjacent Esk Trough.

Jan 1, 1990

By G Chitombo

Mass mining methods have become the mining industry’s preferred way of extracting most of the world’s most important metal and mineral commodities. Given the rapidly increasing global demand for commodities, the requirement to increase the contribution of some of these (eg copper and gold) from underground sources also continues to grow. In the case of copper this contribution is needed by a number of major producers to supplement production from their ageing deep open pits. Satisfying this increased demand will require the design, construction and operation of more effective, higher capacity and larger scale mines which, in turn, will require enhanced mass underground mining techniques such as block caving (BC), panel caving (PC) and sublevel caving (SLC).It is now widely accepted that future discoveries of orebodies, which will be developed using these methods, are almost certainly to be much deeper than the deposits presently being mined in this way and made more challenging because of the likelihood that the associated grades may be much lower than currently mined. The design and mining of future large-scale cave mines (supercaves) will become crucial in order to extract full value from such deposits. An essential prerequisite of this will be a much improved knowledge of the deposit, ie Total Deposit Knowledge. In this context, Total Deposit Knowledge is the characterisation of the ore deposit and its surrounds at all scales and includes; rock type (lithology), the spatial orientation of a range of geological features or discontinuities, rock mass fabric knowledge, metal grade and distribution data, geometallurgical data (including alteration), geo-hydrology, permeability and porosity. This is the information that will be used, as now, to delineate geological and geotechnical domains and construct models, but with outcomes superior to those presently available. From this information better-informed feasibility study design decisions and performance predictions must be made. In summary more geological information and analysis is required and this needs to be aligned to potential mining and processing requirements much earlier in the project than commonly occurs.

Aug 22, 2011

The last decade has seen a dramatic change in the. size and complexity of mining and mineral processing projects in Austral- asia. Major projects of today are vastly different from major projects of the 19.50's. This change has in turn resulted in a change in the role-of consultants whose contributions have been increasingly in the provision of specialist services and less in the form of overall project design and construction supervision. It is anticipated that, the specialist function will continue to represent the principle mode for consultant participation in major, projects. However, by means' of international affiliation, the development of comprehensive engineering and project management capabilities and possibly as a result of Government intervention, it is expected ,that local consultants will assume an increasing degree of participation in.the overall project design and supervision Function.

Jan 1, 1975

By S Farrokhpay, M Zanin

Although it is well understood that in flotation collection zone and froth zone are deeply interconnected, and reagents (and in particular collectors and frothers) cannot be selected without considering their synergistic effect, this concept is rarely applied in plant practice. The feed mineralogy also has an important role in how particles and reagents interact in flotation, which is sometimes overlooked by operators. In this work, a combination of batch flotation tests and froth stability measurements was used to optimise the collector and frother scheme for the flotation of a copper ore. The methodology was applied to an Australian copper plant which was experiencing high variability in froth stability in the roughers when the feed ore mineralogy was changing. It was hypothesised that chalcopyrite in the feed in combination with isobutyl-xanthate had a destabilising effect on the froth phase under the reagents scheme used. Froth stability was restored if a shorter chain length, less hydrophobic, xanthate was employed. It is apparent that the hydrophobicity of adsorbed films at the solid/liquid/air interfaces has a critical role in enhancing or reducing froth stability. Unstable froth causes a reduction in copper recovery in spite of a high collection zone flotation rate. The case study suggests that collection zone and froth zone can rarely be optimised independently of each other. With the laboratory procedure adopted, a more suitable reagents scheme was determined to respond to changes in the feed mineralogy, avoiding fluctuations in plant performance due to unexpected froth instability.CITATION:Farrokhpay, S and Zanin, M, 2012. Synergic effect of collector and frother on froth stability and flotation recovery - An industrial case, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 145-150 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

The Mt Lyell Mine at Queenstown, Tasmania was re-opened in 1995 by Copper Mines of Tasmania Pty Ltd, a wholly owned subsidiary of Mt Lyell Mining Co Ltd. The re-opening followed over 100 years of copper and gold mining at Mt Lyell. Major changes in practice were implemented across the site. Preventing further damage to an already disturbed environment was a major priority. Sublevel caving, at a lower cut-off grade, replaced open stoping for the deep underground mining. Development and later stoping are handled by a contractor, National Mine Management Pty Ltd, in the largest underground contract awarded at the time. Large scale sublevel caving was new to Mt Lyell and not widely practised in Australia, requiring studies and systematic development of the method, particularly in drilling and blasting. Rehabilitation and upgrading of mine infrastructure have been and will continue to be a challenge. The mine has, since 1995, returned to being a stable producer with potential for growth.

Jan 1, 1998

By T Huynh, V Matanitobua, J Zheng, B N. Noller, J C. Ng, H H. Harris

A risk assessment was undertaken of the aquatic ecosystem and bioaccumulation of metals and metalloids in fish at the Leichhardt River, Mount Isa, Queensland. Residual contamination of metals and metalloids in Leichhardt River sediment was assessed and arose from mine practices using river discharge in the 1940s. The ecological risk assessment of sediments involved comparison of the concentrations of heavy metals and arsenic with those of the ANZECC/ARMCANZ (2000) Interim Sediment Quality Guidelines (ISQG). Results indicated that all sites including the background site exceeded one or both the ISQG-high and ISQG-low trigger values based on total concentrations. A lesser number of sites exceeded the ISQG-low trigger values following the 1 M hydrochloric acid extract step, which was used as an indication of bioavailability. An additional risk from particulate matter in river sediment is that acute human toxicity from the consumption of fish contaminated with metals and metalloids is unlikely. The potential risk was assessed by comparing with the maximum levels set by FSANZ (2010) for fish consumption by children and adults. In general, the liver of the fish have higher heavy metal and metalloid concentrations compared to the muscle. Frequent or regular consumption of fish from the Leichhardt River that exceed maximum levels (ML) of heavy metals and metalloids is not recommended. Risk analysis showed that an adult can consume up to 5 kg of fish fillets every day from fish caught at the man-made Lake Moondarra downstream on Leichhardt River and still be within safe consumption levels whilst a child can eat up to 1 kg daily.CITATION:Noller, B N, Ng, J C, Matanitobua, V, Harris, H H, Zheng, J and Huynh, T, ?2014. Assessment of ecotoxicology and health risk from bioaccumulation in fish of heavy metals and metalloids from historical mine practices in the Leichhardt River, Queensland, Australia, in Proceedings Life-of-Mine 2014 , pp 337–348 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 16, 2014

Distillation of the large and growing greenhouse literature indicates that: ò Global warming has occurred over the past century or more; ò Build-up of CO2 (and lesser greenhouse gases) in the atmosphere is a fact; ò This build-up is likely to cause further global warming. It does not appear possible to conclude that the observed C02 build up and observed global warming are linked; nor is it yet possible to forecast global or regional climate variation with conviction. The dominant greenhouse gas is C02 with about half the warming potential of those gases emitted by man's activities; and about 80% of anthropogenic C02 emissions are from the burning of fossil fuels. Fossil-fuel C02 emissions arg divided about equally between the developed countries of OECD and the rest of the world. However C02 output growth over the past decade was about 4% for OECD and some 40% elsewhere. Population growth and pressure for better living standards will ensure continued higher growth outside OECD. Uncertainty about the impact of increasing C02 emissions on climate, and the long lead-times involved in limiting the increase in atmospheric C02 concentrations, are good reasons for taking action now. Australia accounts for about 275 million tonnes a year or just over 1% of the CO2 emitted from the world's consumption of fossil fuels, and the fight to control global emissions will be won or lost elsewhere. Australia's participation will be by wise conselt and by example. In view of the uncertainties involved, it appears premature to take actions that might place an additional financial burden on our hard-pressed country. However, much can be done now that makes good economic sense and has the added benefit of limiting the growth in Australia's CO2 emissions. Natural gas emits less C02 per unit of energy when burned than either coal or oil. Furthermore, new gas-fired power stations utilise energy at considerably higher efficiency than is the case today with coal or oil. Because of much lower capital costs, there is a compelling economic case for permitting natural gas to compete freely with coal in the Australian power generation market.

Jan 1, 1989

I would like to start by thanking The AusIMM and CSIRO for organising this excellent conference and inviting me to give a keynote address. Today I will focus on some broad observations of our industry, and leave the technical discussion to my colleagues who are presenting specific papers covering a wide range of topics. In preparation for this paper, I did a little research into the early history of the Pilbara iron ore industry. I was fascinated to read a quote attributed to Harry P Woodward, the Government Geologist in the late 19th century, before Federation. Mr Woodward described the Pilbara as an iron ore country and observed that æthere is enough to supply the whole world should the present sources be worked outÆ. Mr WoodwardÆs prediction could be viewed as wishful thinking and certainly at Hamersley Iron I would gladly envisage the Pilbara supplying the worldÆs entire iron ore needs! In reality, Western Australia accounted for 162 million tonnes or 36 per cent of seaborne trade in 2001. An impressive effort, but not quite the total world supply as Mr Woodward imagined. But we shouldnÆt dismiss these historical musings out of hand û perhaps we could see it as a challenge for the industry to æwork outÆ the present sources. We all know there is abundant iron ore in the Pilbara, and I expect it is only a matter of time until our collective technical expertise and sheer hard work will enable us to utilise its greater range of ore types. Opening up new markets will be a key pathway to creating additional value from the Pilbara ores. Today I will examine the state of play of our industry and the major influences that shape our business at present, before considering what the future might hold for us. I canÆt guarantee the accuracy of my crystal ball, but the stability and long-term nature of our industry does enable some reasonable hypotheses on where we are heading. I will also spend some time examining the way in which the iron ore producers are working to maximise the value of their resource base and obtain more from their existing capital assets.

Jan 1, 2002

By Hall S, Upton D

WMC Resources Ltd nickel operations have expanded significantly over the last three years. Production capacity has increased at mine/concentrate, smelting and refinery processes to such an extent that WMC now ranks within the top three or four producers of nickel metal in all forms. The stainless steel industry remains the dominant user of nickel. WMC's forecast is for stainless steel production to grow at 2.8 per cent per annum off of the 1995 peak, with much slower growth in the short-term as the stainless steel inventory overhang unwinds, followed by a return to higher trend growth rates. WMC's forecast for the long-term growth in demand for primary nickel is three per cent per annum off the 1995 peak; again, slower growth in the short-term before a return to higher long-term trend rates. This projection is towards the optimistic end of the range of industry experts. It equates to a requirement for new primary nickel of 25 000 to 30 000 tonnes of annual capacity each year.

Jan 1, 1996

As the mining sector increasingly embraces the sustainability agenda, and implements thorough environmental reporting in support of its case for a continued æsocial licence to operateÆ, there is a need for ever-clearer metrics for key areas of impact. It is clear that natural waters are both the predominant pathway and main recipient of the environmental impacts of mining. A new approach to summarising the impacts of mining operations on water quantity and quality is proposed, adapted from an existing generic framework, which is increasingly used to quantify the æwater footprintsÆ of cities and nations. This includes both direct water use and ævirtual waterÆ use, implicit in goods and services used by the mine. In contrast to the existing formulation of æwater footprintÆ, it is here argued that it makes hydrological sense to express the water footprints of mines in areal terms, as equivalent catchment areas. It is also important in the mining sector to capture systematic changes in the scale of impact, which can be anticipated and predictively quantified over the full life cycle. This includes the essentially infinite post-closure phase, during which æremanent water consumptionÆ occurs, either through physical water loss (eg by evaporation from pit lakes) or by ongoing contamination of sizeable flows of natural waters. Methods for assessing the water footprints of mines are now available, and the time is increasingly ripe for them to be applied in earnest in environmental reporting. An example application to a mine in a humid subtropical area of South America is presented. In that case, the mine site itself extended over 106 ha, whereas the maximum water footprint exceeded this by a factor of 27. Although the water footprint can be expected to decline by a factor of ten immediately after closure, sustained evaporation from pit lakes and tailings dams with water covers will gradually increase the remanent water consumption rate, such that the final post-closure water footprint remains about 25 per cent of that encountered during the peak of mining.

Jan 1, 2006

The Hall-Heroult process is likely to be the dominant method of aluminium production for the remainder of the century. The characteristics of the operation of a modern smelter are described and attention drawn to their disabilities which are due chiefly to the small production capacity of individual cells.The principal components of the Hall-Heroult cell- the electrolyte, the anode and the cathodes are discussed in order to identify the problems of scale-up. The factors influencing current efficiency and energy consumption are analysed and lead to the conclusion that the greatest potential for energy saving lies in reducing the anode to cathode distance (ACD).The most promising direction for major change is in the application of a new titanium diboride-carbon composite for coating of the surface of the cathode carbon. It improves the wetting of the carbon by aluminium and should permit the use of sloping cathodes and anodes. The deep metal pad would thereby be eliminated and, in the absence of magnetic perturbations, the ACD could be substantially decreased.

Jan 1, 1987

By Sibson RH

The gold province of Otago occupies an area of upwarped basement, the Otago Schist, comprising predominantly quartzofeldspathic and volcanogenic metasediments. This assemblage is the product of collisional tectonic deformation and associated metamorphism, mainly to lower greenschist facies, during the Rangitata Orogeny (200-100 Ma). Historically this region has produced 240 tonnes of gold, 4% (10 t.) of which was from the mining of Cretaceous gold- quartz mineralised vein systems. Auriferous vein systems in the Otago Schist are mainly hosted within NW trending normal fault-fracture arrays, however NW trending reverse fault-hosted vein systems also occur. We propose that the Late Cretaceous-mid Tertiary Otago Schist structure represents a regional anticlinorium containing flexural folds of at least two wavelengths. The anticlinorium structure has been quantified by determining variations in angular discordance between schistosity and the Otago Peneplain, a Late Cretaceous-mid Tertiary erosion surface covering most of the Otago district. A structural model for the evolution of the post-collisional anticlinorium requires the cooling surficial zone (carapace) of a retrograding metamorphic belt to behave as an elastic lid. Erosion of topographic load on the carapace drove isostatic uplift, which was greatest in the tectonically thickened core of the orogen. In this way differential uplift produced flexural deformation in the elastic carapace, expressed as a large scale arching of the orogenic belt. Flexure created tangential longitudinal strains in the outer-arc, leading to extension and the formation of mineralised normal faults. These structures are separated by a neutral surface from shortening and associated mineralised reverse faults in the inner-arc. Our structural model predicts that the distribution of auriferous lodes should be localised about zones of maximum flexural curvature, where the tangential longitudinal strains are highest. As a result, NW-SE hinge regions separating schistosity dip domains in the Otago gold province may have new found significance as potential exploration targets.

Jan 1, 1995

By Churchill M

One of the significant changes which has occurred in the flotation sector of the minerals industry, over the last two decades, has been the successful development of the very large flotation machine. The last twenty years has seen the volume of the individual cell, available to the industry, increase by a factor of ten. Today, new mills, and existing mill modernization plans, can consider individual cell volumes as large as 85 m3 with the certainty that the metallurgical performance capability of the large machine is inherently as efficient as the smaller machine. The large flotation cell offers benefits to the user such as reduced floor space, lower total power, process control simplification, and reduced maintenance. However, the flotation machine size selection process, based on overall installation economics, must include such factors as process tonnage, flotation kinetics characteristics, and metallurgical performance objectives. This paper discusses the flotation machine size and circuit arrangement selection based on both metallurgical performance and economic considerations. A computer based flotation kinetic analysis technique, which has proven valuable in quantifying the metallurgical response of flotation circuits having different cell sizes and number, is utilized to illustrate the selection of cell size and arrangement best suited to a client's Requirement.

Jan 1, 1991

By J van Niekerk

The BIOX« process for the treatment of refractory gold ores and concentrates has been commercially in operation for 18 years. A total of six BIOX« operations have been successfully commissioned since the commercialisation of the process. Four of these BIOX« plants are still in operation today. There has been a renewed interest in the process the past few years with two BIOX« plants, the Suzdal plant in Kazakhstan and the Fosterville plant in Australia, scheduled for commissioning during 2004. Four new projects are also in various stages of development and are currently scheduled to be commissioned during 2005 and 2006. Research into the process are currently focussed on the two highest operating cost items for the commercial operations, namely power for agitation and air dispersion and cyanide consumption during leaching. Laboratory aeration and agitation testwork using the A340 up-pumping agitation system has shown that similar mass transfer rates can be achieved at slightly higher agitator power. The up-pumping system, however, eliminates the need for a separate blower and sparger system as air is introduced into the slurry from the slurry surface. The use of the thermophile bacteria as the final oxidation step during biooxidation has shown great promise. Reductions in cyanide consumption of up to 50 per cent were achieved when using the combination mesophile and thermophile process compared to standard BIOX« product solids. The combined process takes advantage of the milder oxidising conditions of the well known BIOX« process for the bulk of the oxidation and then uses the high temperature thermophile bacteria to complete the oxidation. The ASTERÖ process for the biological degradation of cyanide and thiocyanate containing effluent solutions has been proven to be efficient and stable. The process uses an activated sludge system with a residence time of approximately six hours in the sludge reactor. Heavy metals and metal cyanide species have also been shown to be removed successfully from solution.

Jan 1, 2004

By S D. Dessureault

The largest surface coal mine in North America requires complex materials handling infrastructure to fulfil the highly variable quality specifications of its contracts. These diverse demands, reflected in the arrival of numerous customer trains every day, necessitate the integration of information in every stage of production. To meet this goal, quality measurement, train line-up and mine planning processes are being integrated into local and remote control rooms. The effectiveness of such a system can only be measured by comparing decisions that are made with, and without, each of the individual integrated control systems. Traditionally, mine controllers use their experience, intuition or a variety of trial-and-error spreadsheets to determine the ideal materials handling flows needed to achieve the correct quality. These balanced decisions are complex since many factors must be considered such as the mine plan, fleet costs, quality variability and others; consequently mine controllers usually have widely varying success between crews.An evaluation model was developed to assess the impact of a decision support system (DSS) integrated in a control room for controlling the coal blending process. To this end, an ARENA-based simulator representing the whole production process can be used to pull performance and current materials handling settings directly either from the real-time systems in the mine, or from historical data. In this way, the same shift (breakdowns, cycle rates, etc) can be simulated and performance compared. Different settings of the DSS, in terms of what information is displayed and the methods for doing so, can be tested for effectiveness. The historical data are extracted directly from a corporate data warehouse, without altering the everyday working databases. At the same time, the simulator writes its results back into the same data warehouse structure, allowing the same KPI reports to be used to measure simulated shifts.

Sep 26, 2011

By Boontanjai C, Boyapati ER

Reagents used for batch flotation tests were Aeroxanthate-343 & 350, Dow Z-6, & reagent-4037 (from Benambra) as copper collectors; Na2SiO3 & Na2S2O3as gangue depressants; lime & HCl as pH regulators; and pine oil & MIBC (methyl isobutyl carbinol) as flotation frothers. A Denver Sub A flotation cell of capacity 250 gms was used for the batch flotation experiments. Atomic absorption spectrophotometer was used for copper assays and microscopy for selectivity and liberation studies. Melbourne tap water was used throughout the experiments. Unless otherwise stated, the following parameters apply to the flotation experiments: flotation impeller speed - 1300 rpm, pulp density during flotation- 22%, reagents addition - in 4 stages, total conditioning time for collectors - 8 minutes, total flotation time- 9 minutes. A variable quantity of copper mineral collector according to the test in question was added, then conditioned the pulp for 2 minutes. The froth was removed by hand, scraping the full length of the cell at constant depth every 10 seconds. No frother is required for this copper tailing flotation. Four concentrates were collected after addition of collector and conditioning at 2,4,6 and 9 minutes. The pulp volume was maintained at a constant level to yield a constant froth depth.

Jan 1, 1990

By D J. Fray

In this work, a fused salt electrochemical process was investigated experimentally for production of metals and alloys directly from respective solid oxides by electro-deoxidation. Direct electrochemical reduction of the oxides was carried out in molten CaCl2-based chlorides in an electrolytic cell, incorporating an oxygen-evolving inert anode, over the temperature range of 850 - 950¦C. The technical viability of the process was demonstrated by the electro-deoxidation of pure oxides and oxide mixtures including NiO, Nb2O5, Nb2O5/TiO2 and Nb2O5/SnO2 to produce nickel metal, niobium metal, NbTi alloys and the intermetallic compound, Nb3Sn. Compared to the conventional metallurgical processes for producing these metals and alloys, this new electrochemical process appears to be much less energy intensive, with lower costs and no direct greenhouse gas emissions from the electrolytic reduction process. The present electrolytic reduction process has the potential to be scaled up for the green extraction of a number of non-ferrous base metals and processing of many advanced alloys.

Jan 1, 2006

By C Zhang, G Si, J Oh, X Zhu

The presence of rock joints has a huge impact on the strength, deformability, and permeability of fractured rock masses by providing surfaces of weakness on which further deformation are more prone to occur, and by serving as the major channels of water flow due to low matrix permeability. In earlier studies, water flow-through rock joints is often assumed as laminar flow between two ideal smooth parallel plates, and the well-known cubic law was derived and widely used to characterise the hydraulic behaviour of rock joints. However, natural rock fractures are irregular and of spatially varied aperture. Thus, the concept of equivalent hydraulic aperture was introduced to modify the cubic law. Numerous works have been conducted on the relation between hydraulic aperture and mechanical aperture incorporating various geometrical parameters. The surface roughness is one of the most sensitive factors for water flow-through rock joints. The aperture distributions are irregular in natural roughed fractures relative to the parallel plates. Barton et al (1985) and Olsson and Barton (2001) incorporated the joint roughness coefficient JRC in evaluating hydraulic aperture and proposed an empirical equation based on fluid flow tests. However, their equations do not conform to the dimensional consistency. Many other researchers (Zimmerman and Bodvarsson, 1996; Xiong et al, 2011; Li et al, 2019) considered aperture distributions in their equations. But the aperture distributions change during shear was always neglected. The contact of rock joints also has a significant impact on the hydro-mechanical behaviour of rock joint, since fluid tends to flow-through a rough joint along connected channels while bypassing the contact obstacles with tortuosity. Nonetheless, previous research mostly considered joint roughness or aperture changes based on 2D joint profiles, while the contact and tortuosity based on 3D surfaces were often overlooked. Only a few works have been made on quantifying the effect of contact area on flow behaviour (Walsh, 1981; Zimmerman et al, 1992; Zimmerman and Bodvarsson, 1996; Yeo, 2001), and mostly ignored contact area change induced by shearing and the associated impact on flow behaviour. Summarily, the quantification of fracture geometry effects on water flow in single rock joints still needs further investigation, especially when considering coupled shear-flow processes. This paper, therefore, aims to study the impacts of contact area and aperture distributions of the single rock joint on the flow behaviour. The evolutions of contact area and aperture distributions induced by shear are considered. Then, an improved model for estimating the hydraulic aperture with the mechanical aperture incorporating the above factors is developed. Finally, a series of shear and shear-flow tests are conducted on artificial joint samples and the model performance is verified by comparing against the results of experimental tests.

Nov 29, 2022