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By Y Peng, C Burns, Y Mu, R A. Lauten

In both laboratory flotation experiments and from analysing the composition of the lead concentrate at the Boliden Tara lead-zinc mine in Ireland, it has been found that F-250 may replace cyanide as a pyrite depressant. Replacement or reduction of the cyanide consumption is highly desirable from a safety perspective given the toxicity of cyanide. Scrutiny of results from the plant trial indicate that F-250 is less efficient as a cyanide depressant when the flotation feed contains high levels of pyrite. Statistical analysis of the results does not capture this trend, illustrating a need to collect more data at higher pyrite ore levels. A recent model proposed for biopolymer-induced pyrite depression is reviewed and discussed next to the suggested mechanism for pyrite depression via cyanide. Review of the interactions causing pyrite depression point to different manners in achieving depression. In light of the less efficient F-250 pyrite depression at high pyrite levels, it is speculated if the two depressants may act synergistically at high levels of pyrite in the feed. CITATION:Lauten, R A, Burns, C, Mu, Y and Peng, Y, 2018. Pyrite depression at Boliden Tara using F-250 – a biopolymer, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 385–392 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

Traditional in situ fan flow test methods under accepted standards require determinations to be made of both static pressures and total pressures during testing. This is to determine the resultant velocity pressures, which are vital in the accurate determination of the final fan airflow. These crucial velocity pressure (Vp) determinations are normally determined using simple manometric instrumentation such as an electronic manometer or an inclined liquid filled manometer. There is relatively little noise or fluctuation in the static pressure determinations and they can be quite easily and accurately recorded. There is almost always considerable fluctuation in the velocity pressure determinations though due to the highly turbulent and irregular velocity profile normally found in such in situ installations. This velocity turbulence means that the recording of such data is subject to random human error as the observer tries to average such fluctuations mentally during the observation period. Worse than this, and in the extreme, the recording of such velocity pressure data could actually easily be misreported if, for some reason, persons chose to do so.The author has devised a field method using highly accurate quartz crystal logging barometers to objectively record these velocity pressures. The method eliminates the ability to either mistakenly or intentionally misreport these crucial velocity pressures and is carried out in parallel with the recognised methodology, so result comparisons can be drawn. As such, a far greater level of confidence can be achieved in the final flow performance results than using the traditional more subjective method. Further to this it is difficult and almost impossible to refute the results using this ancillary substantiation method.The accurate determination of fan flows due to the impost of the carbon tax has taken on much more significance given the financial impacts in Australia at this time. The methodology detailed herein can be applied equally for both fan flow compliance testing and the verification of mine airflow data for greenhouse gas emission evaluations.The paper utilises the results of one 24-point pitot traverse to demonstrate the various findings. These include the very wide range of velocity pressures, which were logged at most of the measuring stations. It also illustrates how the method is utilised and compares the results derived from both this method and the more subjective traditional method along with the benefits of logging the velocity pressure results during the testing process.CITATION:Rowland, J A, 2013. Removing some subjectivity from traditional BS 848 and ISO 5802 in situ fan flow tests, in Proceedings The Australian Mine Ventilation Conference , pp 155-162 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 1, 2013

By K Banerjee, C Dube

Veolia Water Technologies was contracted by a global coal mining company to design a retrofit acid mine drainage treatment facility using DenseSludge™ technology on a former coal refuse disposal site. The project constraint was to reuse current facilities in order to reduce additional capital work cost and avoid additional footprint requirements while improving treatment performance and reducing sludge production and chemical consumption. The initial installation of 454 m3/h served as a pilot plant to demonstrate the benefits of the process and ultimately provided design criteria for the new facility. The pilot demonstrated the benefit of the technology by reducing sludge volume by 90 per cent compared to conventional processes currently in use. The sludge that is reinjected into the mine contains less water, which reduces the volume of water that returns to the mine pool for treatment and mine water balance. Furthermore, the pilot plant reduced lime usage compared to conventional processes by operating at a lower pH set point, demonstrating steady pH control and stoichiometric lime utilisation.CITATION:Dube, C and Banerjee, K, 2015. Sludge conditioning technology to reduce sludge and the cost of acid mine drainage treatment, in Proceedings Tailings and Mine Waste Management for the 21st Century , pp 105–110 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 27, 2015

By M Astorga, J Jackson, J Gaunt

The Ban Houayxai mine (BHX) is a relatively low-grade, low-cost, open pit gold-silver deposit in Laos operated by Phu Bia Mining, a subsidiary of PanAust. The ore production rate at BHX is 4.5 Mt/a, with direct tipping to a semi-autogenous grinding/ball mill circuit with a carbon-in-leach process plant. Approximately 100 000 oz of gold is produced per annum.The operation is located in mountainous terrain with minimal run-of-mine stockpiling. This results in limited capacity for blending from stockpile, with the mill instead reliant upon direct feed ex-pit. Since commissioning in 2012, the plant has seen significant variation in milling rates due to variability in the feed properties of the oxide, transition and primary ores. As part of an ongoing continuous improvement program, an integrated approach was initiated, focusing on maintaining and enhancing production in the future as the proportion of harder primary ore increases. This will specifically focus on direct blending from the loading face using the ore properties and blast fragmentation to maintain mill throughput.This approach was based on the concept of physical assets management, commencing with improving information and knowledge of the condition of the orebody through modelling the characteristics, variability and performance of the feed for processes relevant to throughput. These models are used to support both mine and process plant production planning.The key ore feed characteristics and parameters modelled for the life-of-mine are blastability index, powder factor, crushability or impact resistance and grindability. These predictive spatial models were based on the data from diamond drill holes used in resource definition and geotechnical drilling programs by integrating geotechnical, geological, geochemical and metallurgical data.At the early stages of implementation, the models are being utilised for ore blending decisions to provide guidance and support for budgeting, long-term mine planning, blast design for mill feed and providing the mill with an expectation of performance.CITATION:Jackson, J, Gaunt, J and Astorga, M, 2014. Predicting mill ore feed variability using integrated geotechnical/geometallurgical models, in Proceedings Orebody Modelling and Strategic Mine Planning Symposium 2014, pp 165–176 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 24, 2014

By O Ishiyama, L Lu

Sintering is the most economic and widely used agglomeration process to prepare iron ore fines for blast furnace use. Due to the depleting reserves of traditional high-grade iron ore, there have been considerable changes in iron ore resources available throughout the world, especially in steel mills in East Asia. Corresponding to the changes in the availability of iron ore resources, the amount of impurities in iron ore has been slowly increasing. Some of these impurities have been found to have deleterious impacts on sinter quality and sintering performance. In the meantime, an increasing number of large blast furnaces with inner volumes of more than 5000 m3 have been built that require more sinter and are often more demanding in terms of the quality requirements of the ferrous materials. Finally, sinter plants are facing increasing pressure due to more stringent regulations regarding their environmental impact. This paper gives an overall review of a variety of technologies developed worldwide to tackle the changing raw material characteristics and mitigate emissions from sintering operations.CITATION:Lu, L and Ishiyama, O, 2015. Recent advances in iron ore sintering, in Proceedings Iron Ore 2015, pp 61–68 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By V Novoselov, R Sabirov

Flotation processing technology of water-soluble minerals has made it possible to realise, since the 1960s, the wide scale industrial processing of potash and potassium-magnesium ores (about 200 million tonnes per year) as well as to create the multi-tonnage worldwide production of sylvite (KCl) for industrial and agricultural application. In this paper the particularities of the effect of reagents (blinders, collectors and frothers) during cation flotation in saturated saline solutions are outlined. New reagent modes for activating the effects of alkylamines during the flotation of KCl and the perfecting of technological flow sheets for processing potassium ore have been developed. The results of research on the reverse flotation of carnallite ore, with the help of alkylmorpholine û a new developing technology for benefication carnallite as raw material for the production of metal magnesium and fertilisers are listed. Examples are given of the industrial applications of processed reagent modes at potash flotation factories in Russia.

Jan 1, 2005

By R Peiffer, L van Wyk

The Port of Port Hedland is the largest bulk export terminal in the world and is one of Australia’s most important pieces of economic infrastructure. BHP is the largest Port user to support the export of iron ore products from mines located within the Pilbara region of Western Australia (WA). BHP’s priority is the safety and well-being of its workforce and the communities where it operates. In a recent regulatory application to increase export capacity, BHP committed to the deployment of wind fences to reduce wind erosion from stockpiled ore. Wind erosion from stockpiles was identified through inverse modelling as the most significant dust source compared to other sources such as stackers, reclaimers, shiploaders and transfer stations. The primary cause of dust emissions from stockpiles is dust lift-off during high wind conditions. BHP proposed the installation of wind fences across its Port Hedland operations, targeted at reducing emissions from wind dependent sources, primarily stockpiles, by reducing the wind speed downwind of the wind fence. Modelling predicts that installation of the wind fence will significantly reduce emissions from stockpiles, particularly at BHP’s western operations (Finucane Island). To be effective in shielding stockyards and reducing wind speeds, the wind fences are located upwind and as close as practical to the open stockyards. BHP’s wind fence design incorporates learnings from other existing installations and has been tailored for Port Hedland’s cyclonic conditions. The wind fence will be higher than the stockpile height, with a mesh porosity of approximately 50 per cent. The mesh porosity allows some of the wind to pass through the mesh. This reduces the wind turbulence downstream of the wind fence, as opposed to a solid wind fence, which increases downwind turbulence, resulting in increased dust.

Sep 18, 2023

In practice a sampling solution is a compromise of many requirements: the sample should be representative; the sampling system should also be reliable, less than 95 per cent availability restricts the use of the assayed sample for process control purposes; no sample is the worst sample, and investment costs and installation space/layout are frequently a restriction. For instance, online X-ray analysers for process control introduce a delimitation error by the nature of X-ray physics. Thus only in special cases a relative accuracy better than three per cent relative, as one standard deviation, is achieved. A sampling system for process control needs not to be, as representative, for so many sample properties, as one for composite laboratory analysis samples. Sampling system maintenance is also an important issue. There are many sampling systems in the industry which have been difficult to maintain and are in disuse for lack of resources or incentives to keep them running. Pierre Gy developed the most generally accepted sampling theory. One of the main principles is that all particles in a one-dimensional process stream should have equal chances of being included into the sample. A correctly designed and operated transversing cutter comes close to this goal but has limitations in temporal representativity. For slurries an acceptable solution in many cases is to use a fixed vertical cutter(s) in a position where the slurry is well-mixed by turbulence and other means. For online analysis, reliability problems are mostly related to faulty design or installation of the piping system to the analyser. Properties of material processed, process flow sheet and piping details before and after the sampler have to be taken into account when deciding on which sampling arrangement is appropriate. Guidelines and some solutions to these issues are presented in this paper.

Mar 1, 2010

By A E. Waltho, W J. Shaw

Predicting the physical characteristics of various ore types has for long been a difficult problem during mining. Grade control practices tend to concentrate on the chemical grade of the ore. Estimation of physical characteristics such as beneficiation behaviour is commonly limited to the simplistic application of historical averages. Large amounts of geochemical data are often gathered during the exploration and mining stages of a project, especially in ferrous and base metal deposits. In addition to the elements of principal economic interest, samples are often analysed for suites of gangue constituents to determine whether the mineralisation lies within target specifications. This multi-element data is often put to no other use than this simple chemical classification, yet it may present the geologist or metallurgist with valuable insights into the mineral content and physical characteristics of the deposit. Normative mineral estimates have been used as a method for characterising igneous rocks for almost 100 years. The method establishes and applies a set of sequential rules, by which the chemical components of a sample are assigned to mineral components. Provided that it is possible to make some realistic assumptions about the mineral species likely to be present in a rock unit or deposit and their paragenesis, this approach can be extended to a variety of mineral deposits. The geochemical data that are routinely collected when, for example, drilling iron ore and base metal deposits, can be used to derive estimates of normative mineral content. These estimates can be used to characterise physical or metallurgical aspects of the ore, such as density, beneficiation behaviour and metal recovery. This paper examines the application of normative mineral estimates to a variety of practical resource characterisation problems. The potential for predicting the lump and fines proportions of iron and manganese ores is also discussed.

Jan 1, 1999

By S Goff

The Northern Sewerage Project (NSP) is a $650 M infrastructure project that will increase the capacity of the sewerage system for Melbourne’s growing northern suburbs while also helping to protect the Merri and Moonee Ponds creeks by significantly reducing the number of sewage overflows that can occur after heavy rainfall. The NSP consists of two stages: Stage 1 (NSP1) will be owned and operated by Melbourne Water Corporation, and Stage 2 (NSP2) will be owned by Yarra Valley Water and operated by Melbourne Water Corporation.Glass-fibre reinforced plastic (GRP) was used on both NSP stages, however, since Stage 1’s schedule for installation of GRP was slightly ahead of Stage 2’s, this paper will only focus on Stage 1’s use of GRP.NSP1 involves the construction of 7.9 km of new sewer tunnel ranging in diameter from 1.6 to 2.5 m, five main access shafts at depths of up to 65 m, and connections to the existing sewerage system including several access manholes. Construction began in 2007, and project completion is expected in 2012.The original design for NSP1 specified the use of high-density polyethylene (HDPE-) line precast concrete pipes as the final tunnel lining and HDPE-lined reinforced concrete for the access shafts and manholes. During construction, the rising cost of precast concrete pipes and the introduction of an additional GRP pipe supplier in the market justified a review of the tunnel final lining material. The contractor-proposed GRP pipe alternative was accepted for the final tunnel lining based on time and cost savings that were possible without compromising the design intent. After gaining experience with GRP through this design change, Melbourne Water Corporation reviewed and accepted GRP as the final lining for five smaller connection manholes. The use of GRP for the manholes was particularly inventive as the redesign made use of the approved tunnel GRP pipes as both a structural and corrosion-resistant lining.This paper discusses the use of GRP on NSP1; how the change in material, from concrete to GRP, affected the design philosophies assumed during detailed design; and how construction methods were modified to handle the less rigid GRP material. Details on the structural, hydraulic and durability considerations for the design are included, as are details about the time and cost savings and the quality and safety improvements that were achieved during construction.

Mar 8, 2011

By S Lehane, S Pearce

The characterisation and assessment of waste rock has been the subject of considerable research, and many guidance documents have been published both internationally and within Australia. While these documents provide detailed information on how to characterise waste rock, there is not a great amount of detail on how to determine the optimal waste management options from an operational viewpoint. For example, typical questions that a mine operator would seek answers to include: What placement method should be used (eg end tipping versus paddock dumping)? What is an optimal tip head height for waste placement in a storage facility? How should sulfide grade control be carried out?Defining the contributing factors to waste management and waste material placement and assessing the contribution of each variable directs these assessments towards a semi-qualitative and quantitative methodology. Quantitative methodologies show an increase in the confidence of these assessments by providing logical, measureable assessments.As part of a strategic assessment for waste management at an active mine site, a detailed risk-based investigation of the influence of variables common to waste placement was completed. These variables included placement method, placement height, sulfur grade and material conditioning (eg compaction) on the associated risks of waste material storage. The assessed risks include temperature assessments (potential for thermal take-off as a result of spontaneous combustion), toxic gas production and flow and acid production potential. Applying a numerical modelling approach to the assessment of the different waste material placement strategies allows for the variation in risk to be graphically presented and communicated through risk matrices and histograms.CITATION:Pearce, S and Lehane, S, 2015. Quantitative risk assessment tools to assist with waste management and placement guidelines, in Proceedings Tailings and Mine Waste Management for the 21st Century, pp 353–364 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 27, 2015

By R Dunne, W McCallum

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

Oct 29, 2012

By J A. de la Torre, I R. Cerna, G K. Karadjian

The La Colorada underground mine in Zacatecas, Mexico is a mechanised cut-and-fill silver mine with a capacity of 1250 t/d. The project focused on training the mine’s experienced operators for a fleet of underground trucks, through the use of a training simulator. The project was run by the simulator vendor, in collaboration with the mine’s maintenance, safety and production management.A training program was created targeting maintenance reduction, productivity improvement and increased utilisation and availability. Operators were first acclimatised to the simulated environment, had their current performance baselined, then received targeted coaching, with the process repeated to reinforce learnings. Concurrently, production, maintenance, and safety data was being measured in the real world to measure skills transfer. Due to limited telemetry available from the equipment, many of the data points for the project were sourced from maintenance logs, and accounting data.Equipment failure data measured from unscheduled maintenance records showed an overall 6.5 per cent decrease in unscheduled maintenance following the implementation of the training program. This rate of reduction correlated with the significant decrease in equipment abuse behaviours measured within the simulator during this period. Additionally, overall maintenance activities showed a significant decrease, confirming that reductions in unscheduled maintenance were not achieved through increases in scheduled maintenance. The reduction in equipment damage also increased availability and utilisation of the truck fleet. This highlights that the maintenance improvements not only reduced maintenance costs, but made the fleet available for more production. Moreover, the variability of the operator performance was decreased by 86 per cent, and the difference between their best operator and the worst is less than the baseline; this showed a gap where machine abuse, productivity and cost are impacted directly.This project illustrated that even small-scale mining operations with an experienced operator workforce can achieve positive return on investment (ROI) from simulation-based training. It also highlights that in the absence of equipment telemetry, alternative data sources such as accounting data and maintenance logs can be used to quantify ROI from training.CITATION:Karadjian, G K, de la Torre, J A and Cerna, I R, 2017. Innovations in underground hard rock operator efficiency – through simulation-based training technologies and processes, in Proceedings 13th AusIMM Underground Operators’ Conference 2017, pp 53–58 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 16, 2017

By M P. Sandy, V Louchnikov, V Eremenko, M Orunesu, O Watson

"Surface support is a key component of most ground support systems which are applied as a means of reducing the risk of rockfall occurrence and maintaining serviceability of mine development. Surface support has two primary functions: distributing the applied load throughout the system by providing connection between rock bolts retaining smaller rocks that unravel between rock bolts.Confinement is also provided to the rock mass, which may increase its capacity to resist further degradation or loosening.Surface support has been routinely installed in most underground mines around the world for many years, yet the operators are still not always certain which type is best suited for deformable ground conditions. A number of factors need to be taken into consideration prior to selecting the type of surface support liner, such as its capacity, availability, practicality of installation, manual handling and loading conditions (static or dynamic) to ensure the system’s optimal performance in terms of safety and costs.This paper presents an overview of the surface support types currently used in underground mines in Australia. Shotcrete, weld mesh, high-tensile chainlink mesh, reinforced weld mesh and high energy absorption (HEA) mesh are discussed. A detailed description of each system is provided in terms of capacity, energy absorption, installation cycle and costs. The cost of each system has been normalised to the units of energy absorbed. The information presented in this paper can be used by underground operators as a reference guide when deciding on suitable surface support type for deformable ground conditions.CITATION:Louchnikov, V, Sandy, M P, Watson, O, Orunesu, M and Eremenko, V, 2014. An overview of surface rock support for deformable ground conditions, in Proceedings 12th AusIMM Underground Operators’ Conference 2014, pp 57–66 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 24, 2014

The importance of proper planning, preparation, and execution of a steady state sampling campaign for metallurgical plant assessment must not be underestimated. Careful planning can increase the amount and reliability of information from an optimum number of samples and fully utilize available plant data. It requires specification of the data required, determination of run duration sampling frequency, the selection, modification and testing of sample points and cutters, as well as organisation and briefing of plant and sampling personnel. Preparation immediately prior to sampling, the conduct of the sampling campaign itself and procedures to handle the collected samples and information are discussed. Cutter design, fabrication and use are described in detail, and typical sampling situations, for ball mills, classifiers, pipes, launders, flotation cells and thickeners are considered individually. Measurement of pulp flow rate can often resolve difficult mass balance problems, and discussion of convenient techniques is included.

Jan 1, 1976

Naturally occurring rutile contains approximately 96 per cent titanium dioxide (Ti02), whereas the product from the ilmenite reduction - aeration upgrading process, "sub- rutile", contains only about 92 per cent Ti02. Therefore, there is an-incentive to lift the quality of sub-rutile by removing transition metal impurities, in order to supply a more valuable and marketable product, particularly for the chloride-route pigment producers. Previous studies have shown that the sub- rutile residual iron content (of approximately 4 per cent) and residual manganese content (of approximately 1.5 per cent) are chemically bound within the titanium-oxygen mineral lattice, and are most difficult to remove by simple leaching methods. In attempts to improve their eventual removal, a simple process modification has been successfully investigated in laboratory scale trials. Transition metal sulphides have been formed in the reduced ilmenite by using a "sulphur-doping" technique during reduction (metallization) conducted at controlled temperatures. These compounds give rise to greatly enhanced dissolution of the unwanted transition metal constituents during the sub- sequent aeration and acid washing steps. Thus, the manganese content of the final sulphur- doped, reduced-aerated, acid washed product can be reduced by about 90 per cent to 0.2 per cent, and the iron content by about 70 per cent to less than 1.5 per cent, in comparison with those levels remaining after unmodified pro- cessing. Additions of sulphur as low as 2 per cent of the weight of the ilmenite have proven satisfactory. Preliminary studies reveal that the modified process is economically feasible. These results suggest that the sulphur content of the Collie coal char used in an unmodified reduction step must exert some influence on the eventual removal of iron and manganese during aeration and acid washing.

Jan 1, 1973

By S Ellis

In January 2008 Chirano Gold Mines Limited committed to expansion of the Chirano Gold Project from its existing design capacity of 2 Mtpa ROM ore to a new design value of 3.5 Mtpa. In addition to increased throughput, the design had to contend with increasing ore hardness and competency, while at the same time make cost effective use of existing equipment with minimum disruption to existing production. The solution adopted involved some novel approaches including tertiary crushing and operation of the SABC circuit in overflow ball mill mode and parallel elution with a common acid wash column. This paper describes the approach taken to the design of these elements to achieve a cost effective and safe capacity expansion.

Aug 8, 2011

By Y Xu, T Rowles, B Dareeju, A Dissanayake

Recent updates on tailings dam design guidelines require analysis of undrained (short-term) stability with the application of the SHANSEP model. The SHANSEP model, which was originally developed for alluvial soils, predicates that the Undrained Shear Strength (Su) increases with increasing effective stress. Residual soils by their nature do not necessarily follow this relationship. This paper examines an alternate method to define Su over a range of effective stress conditions for residual soils. Residual soils, formed by weathering of their parent rocks, are generally micro-structured in nature. The microstructural features, such as interparticle bonding, play a fundamental role in stress-strain behaviour of the residual soils. As interparticle bonding is independent of effective stress and void ratio, the undrained shear strength of residual soils is expected to be less dependent on effective stress than alluvial soils, especially at low stress levels. A series of triaxial tests conducted on residual soils, however, indicated that the undrained shear strength and the undrained shear strength ratio (Su/σv’) are to a degree dependant on effective stress. It was found that the undrained shear strength ratio is significantly higher under low stress levels and progressively reduces with increasing effective stress. Based on the laboratory testing data, a strength function with varying undrained shear strength ratios can be developed for the residual soils under the stress range anticipated for a design of a tailings dam. This includes capping the input undrained strength at lower effective stresses based on the drained (effective) and minimum undrained strength. The Factor of Safety (FOS) calculated for the embankment utilising the traditional limit equilibrium (LE) method indicated the application of undrained strength function for the residual soils can provide a significant optimisation for the embankment design compared to adopting a constant undrained shear strength ratio or constant undrained shear strength in the design.

Jul 1, 2021

By Lawson E, Purkiss S. A R, Van Ashwegen p C

It is only in the past decade or so that industrial exploitation of biological resources and techniques has become regarded as a distinct discipline. Commonly referred to as Biotechnology, it embraces biochemistry, microbiology and the engineering sciences and is mainly aimed at the biological conversion of suitable raw materials into desired end products. The catalytic agents are more often than not bacteria although other micro-organisms such as fungi are used. The range of micro-organisms used is wide and the choice depends upon the desired end product, which in turn depends upon the metabolic attributes, genetically engineered or otherwise, of the cells. The metabolic diversity of micro-organisms has been applied to processes such as antibiotic production, food processing, brewing and chemical production, and of course extraction of metals from ores. Metabolic diversity is, to a certain extent, based on nutrition, which, in its simplest form, can be divided into energy source, carbon requirements and nature of the electron donor producing reducing power to the cells. The source of energy may be light, in which case the organisms are phototrophic (eg green plants, algae). The carbon requirements and reducing power may come from organic sources. These organisms are then called heterotrophic (eg man and most bacteria, including the well known Escherichia colt). However, there is a group of bacteria whose energy metabolism depends upon chemical redox reactions, use inorganic carbon (CO2) and obtain their reducing power from reduced chemicals such as metal sulphides. These are known as chemolithotrophs. They play an important role in mineral recycling in nature and are also ideal for extraction of metals from ores. This is because they are extremeophiles being acidophilic (grow at very low pH) and sometimes also thermophilic (grow at very high temperatures). These bacteria operate in such hostile environments that competition, or contamination, by other organisms does not occur. Extraction of metals from ores by chemolithotrophic bacteria is commonly referred to as biohydrometallurgy. Other related areas are bioadsorption of metals from dilute solution,- microbial treatment of metal contaminated wastes and removal of toxic chemicals produced or used during mineral processing. This paper basically reviews the work that Gencor has undertaken in the field of biohydrometallurgy and the advancements it has made in commercialising the technology, but also touches on certain long-term areas of research that are currently under investigation.

Jan 1, 1995

By Gillies A. D S, Just G. D

Coal washability data can be used for assessing coal quality. However, the techniques of using these data to solve quality problems differ from one mine to another and certain problems may never really be investigated due to limitations of the available techniques. One promising way to overcome these limitations is by correct application of geostatistics.A geostatistical study on coal washability data was undertaken based on a data set of closely spaced in-pit bore cores. These bore cores were analysed consistently over a relatively simple geological area. The average distance between the drill holes was about lOOm. There were 78 drill holes available for the area after deleting the erroneous bore cores. During the study, nine extra closely spaced drill holes were drilled within a single mining block.A procedure to construct two coal quality models, a kriging or cokriging model and a simulation model, was proposed. The modelling results for the data above are discussed and results of a mine scheduling exercise based on the models developed are included.

Jan 1, 1992