Search Documents

By R Vleggaar

In addressing a short-term operational need for the relocation of a tailings storage facility reclaim pond, a mine has achieved a host of water management objectives. Through effective planning and adoption of a strategic æwhole of mine lifeÆ approach, the mine has achieved significant environmental, social and economic benefits. A review of all water management aspects across the site identified a host of other interrelated water issues and concerns which, if dealt with individually, would prove too costly for individual operational departments. When considered as a whole, however, the issues became opportunities and provided the stimulus for integration of the site water management system. The development of site water and solute balance models provided the tool by which a number of water management options/strategies could be evaluated. The conceptual design and costing of the proposed water infrastructure further facilitated the evaluation of the multiple benefits to be gained from each option. A business case could then be made to mine management for the preferred option. The recommended water management strategy finally recommended to the mine not only provided a tailings storage facility (TSF) reclaim pond, but also provided for:increased wastewater recovery from the TSF, the capture of all waste rock dump run-off, additional water harvesting from local creeks, increased wastewater reuse, improved environmental water management, infrastructure that could be used by the local community after mine closure, and overall cost savings. This paper illustrates how effective water management planning can provide both short-term economic and environmental benefits, as well as long-term social benefits.

Jan 1, 2006

Shortly after the outbreak of war in September, 1939, it became apparent that considerable quantities of certain metals and alloys which at that time were not being produced in Australia would be required in increasing amounts for the prosecution of the war effort.Australian industry had relied on overseas sources of supply for the relatively small quantities of many special metals which were needed under peacetime conditions. As the war progressed so great became the demand for mooy of these alloys in Great Britain and other allied countries that it was necessary for them to place an embargo on the export of these materials, and thus it soon became evident that if Australia's production of munitions was to expand and develop it would be necessary for her to become independent of overseas sources for many of these essential 'items. The shipping position also became very acute, and this, accentuated the difficulties of obtaining these alloys. Because of the conditions outlined aqove, the manufacture of over thirty different metals and alloys .was undertaken at Newcastle during the past decade. It is with two of these that this paper proposes to deal. They are tungsten powder and ferro-silicon.TUNGSTEN POWDERTungsten is a rare and comparatively new metal. It is used extensively in the production of high speed tool steel, some grades of which contain up to 22% tungsten. Such articles as twist drills, reamers, milling cutters, and lathe tools are made from tool steel, and the demand for these during the war years was greater than ever before. The use of tungsten in the manufacture of high speed steel was first developed in 1914 by the Germans, and when it was discovered that they were using tungsten bearing steel for the production of munitions there began a world-wide search for ores of this rare metal.

Jan 1, 1947

By P J. Colbert, P D. Munro

OZ Minerals' Prominent Hill copper-gold concentrator in South Australia was built in 2008 with commercial production commencing in early 2009. In addition to recovery of valuable minerals, the flow sheet for this iron oxide-hosted copper-gold deposit has to address the issue of producing a good quality saleable copper concentrate by high selectivity against non-sulfide gangue. Detailed mineralogical studies integrated with the metallurgical test work highlighted that liberation of fluorine-bearing minerals and subsequent very efficient rejection in cleaner flotation was necessary to produce a commercial quality copper-gold concentrate. Bench scale laboratory metallurgical tests and mineralogical studies identified the need to regrind rougher concentrate to a P80 of 20 -25 microns or finer for adequate liberation of the fluorine-bearing minerals. Satisfactory separation of the fluorine-rich gangue material from the valuable copper sulfides requires highly efficient cleaner flotation. This is done by a combination of washed froth cleaning and conventional dilution cleaning. Proven equipment developed to meet similar taxing liberation and separation duties for the treatment of the refractory zinc-lead-silver ores of the Carpentaria-Mount Isa Mineral Province have been selected. The combination of Xstrata Technology's IsaMillÖ and Jameson Cell technologies addressed both the liberation and separation issues in the Prominent Hill concentrator. The energy efficient IsaMillÖ technology both regrinds the rougher concentrate while its inert grinding environment prevents contamination of mineral surfaces with 'debris' ensuring subsequent optimum flotation performance. Heading up the cleaner circuit with a 'scalping' Jameson Cell followed by conventional flotation equipment allows this section to take advantage of the Jameson Cell's high intensity flotation environment and froth washing capability to achieve maximum concentrate grade (at minimum fluorine levels) while maximising recovery through the use of conventional flotation machines. This paper looks at the development of the Prominent Hill flow sheet from the initial mineralogical and laboratory test work to the design, scale-up and early operation of the Prominent Hill regrind and cleaner flotation circuits. The mineralogically-based approach of domaining metallurgical ore types combined with the axiom of size-by-size mineral particle behaviour by liberation class gave a clear understanding of the liberation and separation issues involved in the processing of Prominent Hill ore. Technologies developed to meet much more onerous liberation and separation duties for the treatment of the refractory zinc-lead-silver ores of the Carpentaria-Mount Isa Mineral Province were successfully used to improve concentrate quality by rejecting non-sulfide gangue containing impurities. An IsaMillÖ and a Jameson Cell are included in the circuit for fine grinding and for additional concentrate cleaning. Plant performance since commissioning has justified the approach for metallurgical test work and equipment choices for the flotation circuit.

Jan 1, 2009

The purpose of this paper is to present a detailed account of the development of the Blasthole Diamond Drilling method of stoping now used at the property of Big Bell Mines Limited, in Western Australia.The ore body is one of the large low grade gold deposits of this State, being a continuous lens 1,850 ft. long and ranging in width from 15 ft. at the ends to 120 ft. at the widest part, the average width being 59 ft. It was first worked in 1913 by a local syndicate, and up to 1924, when operations ceased, 64,448 tons of 3.4 dwt. ore were mined from a shallow open cut. Between 1928 and 1932, 15 deep diamond drill holes were put down to test the ore body at vertical depths ranging from 100 to 700 ft. On the information gained from these drill holes, Premier Gold Mining Co. Ltd. began underground explQration. A level was driven at a depth of 253 ft. and crosscuts put out to the full width of the, orebody at intervals of 100 ft. along the strike, all ore broken being put through a sampling plant. On completion of this sampling,' Big Bell Mines Limited was formed as the operating company, and a plant with a capacity of 1,000 long tons per day was erected and mining and milling operations were commenced in 1937. Ore was first mined from glory hole stopes, 65 ft. long, separated by 35 ft. pillars, by benching using conventional steel with changes up to 20 ft., all broken ore being hauled to the main shaft on the...

Jan 1, 1948

By M Wilkes, C-Q Liu

Microbial oxidation of refractory sulphide ores (particularly gold and copper ores) are well-established techniques that are increasingly employed because of their low capital and operating costs and environmental benefits. CSIRO has established a multidivisional project, the æBioMineral Processing InitiativeÆ, with the goal of generating new and improved high temperature micro-organisms for biological oxidation of these refractory ores. The project is currently focused on the discovery/generation of novel hyperthermophiles for the bioleaching of copper from chalcopyrite. As part of this project we are investigating the practicalities of genetic modification of iron/sulphur oxidising micro-organisms. The molecular biology of iron/sulphur oxidising acidophiles is still in its infancy. This work is aimed at improving our knowledge of vectors, promoters, selectable markers, gene transfer and expression in these organisms. The Acidithiobacillus ferrooxidans genome is currently available and genomics is proceeding at a rate where in the next few years we can expect at least one or two relevant microbial genomes to be sequenced each year. New genes that impart useful characteristics to iron/sulphur oxidising acidophiles will be available from published genomes and the study of newly isolated hyperthermophiles. We need to be in a position to clone and express those genes. This paper will describe the isolation, transfer and expression of thiocyanate hydrolase genes in Escherichia coli and At. ferrooxidans. Most common antibiotics are not effective against iron/sulphur oxidising acidophiles. Also, the use of antibiotics or their resistance markers outside of a laboratory setting would not be appropriate. Resistance to thiocyanate should be a useful selectable marker, without implications for human or animal health. Additionally, thiocyanate resistant iron/sulphur oxidising acidophiles might have application in gold bio-oxidation plants in arid areas where reuse of contaminated tailings water is desirable. The cloning of thiocyanate genes in broad host range plasmids under the control of E. coli and At. ferrooxidans promoters and the expression and phenotypic effects in both species will be described.

Jan 1, 2002

By A Tomsett, R Kidd, Z Casley

Bivariate recoverable resource estimation aims at predicting the recovered metal for a secondary variable when a cut-off is applied to a primary variable. The choice of a consistent geostatistical model is advisable to allow a robust estimation from exploration data of the primary and secondary metal recovery functions on a generic selection block (selective mining unit û SMU) within large panels. Ore processing decisions at Lihir Gold LimitedÆs Lihir Gold Mine are based on the gold and sulfur estimates of SMUs from production (grade control) data. The predictive model from exploration data at Lihir is based on the estimation of a recoverable resource for gold by Uniform Conditioning (UC), with an estimate of the sulfur grade being provided by Ordinary Kriging of panels. While univariate UC is adapted to the diffusive nature of the gold mineralisation (Ladolam orebody) at Lihir, the independent estimation of sulfur, through ordinary kriging, fails to capture the potential spatial correlation that exists between gold and sulfur mineralisation. This paper presents a practical implementation of bivariate UC, which better represents in the resource model the spatial correlation between gold and sulfur. Incremental economic gains through improved definition of material categories and scheduling are investigated, and the particular impact on the process of geological interpretation and domaining is emphasised.

Jan 1, 2009

By D Morris

This presentation discusses a water filtration technology termed Fabric Media that is somewhat novel to the Australian market place and reports several recent mining industry installations. Like many novel household cleaning products, the Fabric Media technology applies the science of active washable micro fibres as the means of capturing contaminant solid particles. The simple Fabric Media water filtration product offers several attractive attributes when compared to the more traditional media bed filtration processes such as sand filters, and barrier filters such as micro membranes. A micro fibre based filtration media enables both superior adsorption for the contaminant and wash ability. Stronger adsorption capture enables a much higher flux and greater solids loading density for the filtration task, meaning that lower cost and smaller footprint equipment is available. For Fabric Media water filters, a textile weave is selected that minimises the flow backpressure for a given particle size separation. Thus for an equivalent filtration performance this provides a much lower operating energy requirement, generally between 50 and 80 per cent less than for a sand filter. A Fabric Media is not abrasive to itself or to the filter tank. The filtration performance remains constant and predictable. The equipment life is much longer and the asset value of the new filtration equipment should maintain throughout the project life. Fibres are extremely mechanically robust and chemically inert. Fabric Media survives repetitive exposure to a rapid mechanical washing event providing high wash efficiency with minimum equipment off-line time for the backwash. Dislodging captured contaminants by a high-speed mechanical agitation enables a minimum off-line time during backwash events. The vigorous backwash destroys adhering flocculant and eliminates the formation of mud balls, which can permanently foul sand filters. The mechanical agitation wash of the Fabric Media water filter ensures complete removal of grease and biofilm, which can adhere and block a membrane surface. In comparison to sand filters and micro filtration membranes, the Fabric Media product is applicable to a significantly wider range of solids concentrations without permanent damage. The technology is very forgiving to excursion in plant control and is therefore considered a very operator-friendly concept.

Jan 1, 2006

By B Veera Reddy

For thick seam extraction, the Blasting Gallery (BG) method is ideal for obtaining the maximum percentage of extraction at fast rates. The continued use of this mining method is threatened by strata control and spontaneous heating problems. The strata control problems are managed, to some extent, by supporting the roof with cable bolting and roof bolts of 2.5 m length and with regular induced blasting. However, a number of BG panels were sealed off prematurely due to spontaneous heating problems, losing 1.12 million tonne of coal. The use of compressed CO2 for controlling mine fires is not uncommon in the coal mining industry, but its use is something new for controlling active spontaneous heating in a BG working panel goaf. This method was attempted at the BG I/8 panel of the Godavarikhani (GDK) 8 Incline, Singareni Collieries Company Limited (SCCL). The spontaneous heating was effectively controlled and the remaining coal in the panel was completely extracted by continuous flushing of carbon dioxide (CO2) into the goaf for 40 days. One thousand and twenty four CO2 cylinders, each of 45 kg at 80 bar pressure were flushed into the goaf at the rate of 25 to 30 cylinders (350 m3 of CO2) per day. A quantity of 35 510 tonne of coal was extracted during the period from 30 July 2002 to 7 September 2002. The main objective of this paper is to present the complete process of controlling the spontaneous heating by CO2 flushing and to report on the study of the behaviour of gases and their analysis. The unique experience of controlling the active spontaneous heating in the working Blasting Gallery I/8 panel goaf at GDK 8 Incline with CO2 flushing (till the completion of the panel) will go a long way in establishing a working procedure for handling fire/spontaneous heating problems in BG panels.

Jan 1, 2005

By B Hall

In feasibility studies the choice of optimum cut-off grade is typically based on an evaluation of tonnage grade curves and manual design of stopes at one or two cut-off grades. In the industry these stope designs are usually based on break-even cut-off grades, but there is little consensus on what cost and price assumptions ought to be included. A new tool for automated stope design has been developed that generates sets of stope shapes for a nominated range of cut-off grades, or depending on the nature of the mineralisation, cut-off values based on net smelter return calculations in the block model. The stope design procedure includes constraints in stope and pillar geometry for the selected mining method and can be used to evaluate sublevel interval and sensitivities to other design parameters in the specific geological and geotechnical environment. These ænested stopesÆ are analogous to ænested pitsÆ in open cut design, and can be used as a key input in the æhill of valueÆ methodology for the evaluation of the optimum cut-off grade in underground design. The results of many consulting studies indicate that a break-even cut-off grade will not be the optimum cut-off grade. A particular benefit of the new stope design tool is that the design rules used to establish stope shapes in the feasibility study can then be used in mine production, in an optimal and repeatable method. This methodology is being advanced in the AMIRA P884 PRIMO project, which is a new research collaboration coordinated by AMIRA International. The project has brought together active research groups in Australia and Canada, with the goal of developing a flexible framework and set of software tools for optimisation in underground mine design.

Jan 1, 2009

By Ross J. F

A pillar 'is a block of coal left in the first working of a coal seam for the purpose of supporting the superincumbent strata in such a manner that the winning out roadways will be safe to traverse by men and by the coal transport system.PRINCIPLES OF PILLAR EXTRACTION.The size of a pillar is chiefly dependent on the depth of cover, and in a lesser degree on the nature of the coal, or the condition in which the seam has been laid down. In a seam at 1,100ft. depth of cover, and assuming a spec'ific gravity of 2.5 overall for the cover strata, a pressure of 1,200lb. per sq. in. is the loading on the top surface of the coal seam before mining begins.When mining commences, and as the pillars are formed, an increased load is imposed on the coal left in the pillars, according to the percentage of coal extracted in the first working. Thus, if 25% extraction is taken in the first working, the load on the pillars is theoretically increased from 1,200lb. per sq. in. to 1,600lb. per sq. in. over the area mined. If this state of things went on indefinitely it would not be possible wholly to extract a pillar because of the extreme pressure tliat would be thrown on the diminishing portion; but, fortunately, another element, that of time, enters into and assists the process of extraction.If the superimposed strata were of an entirely plastic nature, this time factor could not operate, as the cover weight would settle instantly on the remaining portion of the p'illar and finally overwhelm it. The cover strata above a pillar generally have a certain rigidity which does not allow the superimposed weight to settle instantly on the pillar fraction, and it requires a period of time to elapse before the extra weight is felt by the pillar.The time factor varies widely, and is governed entirely by local conditions; it can only be determined by experience gained on the spot or in close proximity to the area of operations. It is dependent on the strength of the strata and its characteristics under bridging conditions.It is, therefore, logical to assume that the more rapidly a pillar can be extracted the greater will be the safety factor and also the percentage of recovery of coal.Up to the present time, the operation of the extraction of pillars in this country has been, with a few exceptions, a manual one, and before mechanization of Collieries can be fully accomplished, the process will have to be performed mecharrically.

Jan 1, 1947

The decrepitation technique is a rapid means of measuring abundances, temperatures and to some extent the fluid compositions, of fluid inclusions in transparent and opaque minerals. The method has been used to investigate the hydrothermal fluid systems associated with gold mineralisation in the Tennant Creek, Pine Creek and Halls Creek Goldfields. At the Enterprise Mine, Pine Creek, several different stages of quartz veining are distinguished and within these, gradational changes in fluid temperatures and compositions help to define the centre and nature of the thermal system responsible for the mineralisation. In the surrounding Pine Creek region and at Tennant Creek and Halls Creek, the results were applied on a regional scale to characterize outcrops and aid in the discrimination between potentially mineral- ized and barren outcrops. The decrepitation method involves the heating of a small (lgm) sample of crushed and sized grains up to as high as 800 degrees celsius. During the heating the fluid inclu- sions within the grains develop sufficient internal pressure to physically burst, the temperature of such bursting being dependent on the type of fluid and the prevailing tem- perature at the time the inclusion was originally trapped. The resulting tabulation of the number of inclusion bursts per 10 degree temperature interval is plotted as a histogram of decrepitations versus tempera- ture and called a decrepigram. The decrepi- grams frequently show several distinct peaks at different temperatures which are caused by different populations of inclusions in the sample. The areas of the peaks indicate the abundances of inclusions in each population while the shape and mean temperature of the peak provides a guide to the type of fluids involved. Of particular importance in this study is the presence of decrepitation peaks at fairly low temperatures (around 2000 C. These are characteristic of C02 rich fluids which build up internal pressure very quickly when heated. The Enterprise Gold Mine at Pine Creek comprises a number of overlapping quartz vein systems hosted by Burrell Creek Formation sediments. The geology of this mine has been described at this conference by Dann and Delaney, who have defined several distinct stages of quartz veining based on structural, mineralogical and physical features of the veins. For this decrepitation study, 19 quartz samples from the mine and environs, including some from each stage of veining were collected. These results suggest that there are 4 major vein types, within 3 of which additional small variations can be discerned which are due to gradational changes in the temperatures and fluid compositions in the mine area.

Jan 1, 1984

By L C. Thompson

Biomineralisation is the process by which microorganisms mediate and catalyse inorganic reactions so as to form new mineral assemblages. The goal of biomineralisation as a remediation tool is to control microbial processes and their environment so as to sequester and immobilise specific toxic metals within exceptionally strong bonds of neo-formed mineral assemblages. In this way, the bound metals are no longer mobile within a geological time-scale. Applied biomineralisation uses microorganisms, which are isolated from a metal waste environment and are selected for their ability to rapidly catalyse neo-mineral development from dissolved or leachable metals. A typical waste environment will contain microbes that contribute to the mobilisation of metal contaminants as well as microbes that possess the potential for remineralising available metals. Selection and augmenting the correct combination of bacteria and eliminating the competing mineral degrading reactions are the key to applying biomineralisation as an in situ remediation process. Applied biomineralisation harnesses the microbesÆ ability to stabilise toxic soluble metals into non-mobile mineralassemblages. This paper will discuss and demonstrate the biomineralisation process through several case studies including the Summitville mine site in Colorado, the McCoy-Cove mine in Nevada, the Argonaut mine in California, and an historic lead site in Crooksville, Ohio.

Jan 1, 2004

It is recognised by the current JORC (1999) code that resource classification involves the interaction of numerous qualitative and quantitative criteria such as data quality, geological continuity and grade continuity. No prescribed criteria and rules will work for all situations or even between different ore types within the same deposit. Also these criteria and rules are sometimes applied without a clear understanding of their appropriateness, accuracy or correct implementation. For these reasons case studies are useful to evaluate and compare criteria commonly used to assist in resource classification. In this paper blasthole data from a selected area of Joffre Member hosted ore of the Brockman Iron Formation at the Mt Whaleback orebody are used as the basis of a case study for the above-mentioned purposes. Iron grade, in per cent, is interpolated from a blasthole dataset into a block model using ordinary kriging. Samples are then removed from this blasthole dataset to produce a random sample grid, a semi-random sample grid and a regular sample grid. Using nearest neighbour, inverse distance squared, ordinary kriging and sequential gaussian simulation, block iron grades are estimated using these three blasthole data subsets as inputs. This provides four groups of estimates with the ordinary kriging estimate based on the complete blasthole dataset being considered to represent the true estimate of iron grades. Also generated during this process are estimates of the error for each block. These error estimates range from the simple, such as drill spacing, through to more advanced methodologies such as kriging efficiency and simulation. These estimates of grade and grade estimation error are then compared to the true estimate using graphs and statistics. In order of increasing accuracy the block grade estimation and simulation methods were nearest neighbour, inverse distance weighting, ordinary kriging and finally conditional simulation. The simulation in some instances doubled the accuracy of individual block grade estimates when compared to nearest neighbour and inverse distance weighting estimates. It was found that many methodologies for estimating the error of individual blocks performed equally well with only methods such as average drill hole spacing and classification by search ellipse pass number performing poorly. An approach on how to convert the abovementioned error estimates of individual blocks into a meaningful JORC classification is also discussed. Although advanced non-linear resource estimates are applicable, most iron ore mines are still using relatively straightforward methods. The use of blasthole data and some simple linear interpolation methods and simple linear based error estimates makes this study repeatable for most iron ore sites and their resource geologists. This style of investigation is recommended as a useful approach for the Competent Person to apply to their deposit and thus better select, implement and understand the criteria used for resource classification and provide more consistency and confidence in the resource classification process.

Jan 1, 2002

The Kyaukpahto gold deposit is located at latitude 23¦ 47Æ 55" N and longitude 95¦ 56Æ 35" E in the Kawlin-Wuntho district, Sagaing Division, Myanmar. Gold mineralisation is hosted in sandstone of the Male Formation (Eocene) and occurs as stockworks and disseminations. The high-grade gold mineralisation is locally concentrated in a breccia zone. The gold deposit is closely associated with a NNE-SSW trending fracture system that forms tensional open fractures. These tensional zones are thought to be directly related to the Sagiang transfer fault system that experienced several hundred kilometres of northward dextral movement during the post-Upper Miocene. Major sulfide minerals are pyrite and arsenopyrite with minor galena, chalcopyrite and sphalerite. Gold mineralisation is associated with intense silicification, sericitisation and argillic alteration. Primary Type I fluid inclusions in the quartz from the mineralised zone are 5 to 15 ¦m across and yield homogenisation temperatures of 239¦ - 310¦C and salinities of 1.2 - 10.9 wt per cent NaCl equivalent. Laser Raman spectroscopic analysis indicates the presence of CO2 and CH4 in Type II fluid inclusions. Sulfur isotope analysis of disseminated pyrite in the ore zone by the laser ablation method indicates d34S values from -5.48ë to +5.53ë. The geology, alteration, ore mineralogy, fluid inclusion microthermometry and sulfur isotope data of the Kyaukpahto deposit are consistent with an epithermal ore deposit model for the deposit. However, the presence of CO2-liquid bearing fluids and the detectable CH4 in the gaseous phase of the fluid inclusions conflict with a typical epithermal origin for the Kyaukpahto deposit. The host siltstone and mudstone sequence, trace element geochemistry, and the disseminated nature of sulfide and gold mineralisation are also common characteristics of a sedimentary rock-hosted gold deposit, and these features may indicate a Carlin-like affinity. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

By T Davis

The 500 orebody in the upper levels of Mt Isa Mines in north-west Queensland was mined by sublevel caving and block caving from 1962 to 1969. The hot and reactive rock mass of this orebody provided significant mining challenges including ground temperatures above those resulting from the geothermal gradient. Recently Xstrata Copper has been studying the potential to mine this orebody by modern caving techniques. Part of the study process has included re-accessing the ore zones for diamond drilling and trial development. A cross-cut trial drive, the first primary development into the orebody in more than 30 years, encountered a temperature increase in development holes from low sixties to almost 80¦C in less than 10 m advance. The issues associated with managing this risk include sourcing suitable quantities of reactive ground explosives for a single small heading and the temperature limitations of the explosives and detonators. Risk management outcomes included controls to mitigate the safety and reliability risks relating to misfires. The control that dealt directly with the challenge of continuing development in elevated temperature ground was to cool the holes before and during charging. The most effective and practical cooling medium proved to be water. Rapid rock temperature recharge time meant cooling had to continue as close to firing as possible. Reticulation systems were constructed to allow cooling to take place up until withdrawal for firing. No misfires occurred with the cooling system and additional controls in place. This proved that developing safely and effectively in the elevated ground temperatures of the 500 orebody is practicable.

Jan 1, 2008

By J Player

Big Bell Mine started experiencing relatively large mining related seismic events, and accompanying rockbursts, from February 1999. Twelve rockbursts damaged access development from February 1999 to June 2000, with severe damage extending for up to 100 m along footwall drives. Five seismic events associated with the rockbursts were recorded by the AGSO, measuring 1.9, 2.2, 1.7, 2.4 and 2.2 on the Richter scale. These events affected 485 and 460 footwall drives in August and November 1999 and 535 footwall drive in June 2000 (drive level nomenclature is equivalent to the depth below surface and RL). After the third event (July 1999) it was apparent that the seismicity was not a once-off phenomenon. This (sudden) onset of seismicity required management to implement a series of precautionary measures:to ensure the safety of the workforce, to maintain continuity of production, and to reduce rockburst damage rehabilitation. The measures included extended re-entry periods and exclusion zones in high-risk areas, improved rockburst resistant support systems in areas prone to damaging seismic activity and improved support systems in areas prone to shakedown damage. A full-scale minewide ISS seismic system was ordered in October 1999 and commissioned in February 2000. A portable eight-channel CSIR-Miningtek system was installed at short notice as an interim measure in August 1999. This CSIR system covered the northern producing stopes, where the majority of the rockbursts had occurred. The objective of the seismic monitoring was to monitor relative activity and to determine trends with regards to time and location. MAP3D numerical modelling was used to investigate the relationship between seismicity and various combinations of stress components to assess the relative seismic risk in both current and proposed working areas. This information is used to determine where and at what stage in the mining cycle the rockburst resistant support is required. Analysis of the seismicity has determined two distinct modes of seismicity û small-scale localised, high frequency events in high stress areas and larger events related to shear along previously intact foliation surfaces. This paper includes a summary of the seismic history, seismic data analysis, support system design, mine design adjustments and management action to minimise the effects of seismic activity at Big Bell Mine.

Jan 1, 2000

Underlain by and intruded into the sedimentary rocks of the Transvaal Supergroup the Bushveld Complex is the largest known layered intrusion in the world and contains one of the richest ore deposits on earth. It has been the world's major source of Platinum Group Metals (PGM) since the mid-1900s with Chromite and PGMs the two most economically important components of the Bushveld Complex. The lower group (LG), within the critical zone, consists of seven chromitite layers and it is within this sequence of chromitite layers, the most important target of the lower chromitite group is found, ie the LG6 chromitite unit. The LG6 chromitite unit consists of a chromitite duplex composed of the lower LG6 chromitite layer (Steelport seam), averaging 1 m thick, overlain by a 0.66 m waste parting and a thin 0.34 m thick LG6a chromitite layer (leader layer).Two mining methods are commonly applied in the Bushveld Complex to extract the LG6 chromitite layer package. One method consists of footwall development utilising rail bound equipment to gain access to the orebody and then extracts only the LG6 chromitite layer by means of hand held rock drills and scraper winches. The second method is the use of mechanised equipment to access the orebody on the plane of the ore utilising bord and pillar mining method, which extracts the full mineral resource, ie the LG6 and LG6a layers. Conventional narrow vein stoping is often selected due to the large conventional mining skills base found in South Africa, the perceived cost and dilution implications of utilising mechanised equipment, and the difficulties of using mechanised equipment at dips above 12¦. The driving factor for mechanised mining is the perceived ability to access the orebody quickly and inexpensively, and extract the entire mineral resource package (LG6 and LG6a) while limiting capital expenditure and improving safety.This paper investigates these two commonly applied approaches, highlighting the benefits and problems associated with the two approaches. Comparisons will be made of the two mining methods and recommendations given for the mining engineer to consider before selecting the appropriate mine design.

Dec 6, 2010

By R Piper

The Yabulu Nickel Refinery commissioned in 1974, processes lateritic ore via a modified Caron process to produce high quality nickel and cobalt products. The Greenvale orebody provided the sole source of feed to the plant until 1990 and with well-blended mineralogy, it resulted in stable and predictable plant performance, allowing the operating focus to be on reducing energy consumption and increasing ore throughput. This approach provided better economics than pursuing increased reduction efficiency. From 1990, increasing quantities of lateritic ore were imported from Indonesia, Philippines and New Caledonia. This introduced considerable variation in ore blends and instability in plant operation but also provided the opportunity to treat higher grade ore blends which yielded higher reduction efficiencies. Ore reduction is conducted using 12 Herreshoff multiple hearth reduction furnaces, using heavy fuel oil as reductant. The æROASTERÆ Project was approved in November 2000 with the primary objective of improving Nickel reduction efficiency by: Stabilising Roaster Operation via a structured program including focused maintenance efforts, capital equipment upgrades, new process measurements, process re-design and improvements to operating skills and process troubleshooting. A structured technical program including laboratory and plant studies using one plant furnace as a pilot unit to develop improved knowledge of how the reduction process proceeds in the Herreshoff furnace. Armed with this knowledge, optimised process conditions and a reduction process model were developed contributing to a significant demonstrated reduction efficiency improvement. Technical input to the project was provided by QNI with Hatch providing the engineering and project management for the $8.5 M capital work. Execution of the work included extensive consultation with the plant operators and close cooperation between the Hatch project team and QNI operations personnel ensuring installations were completed with minimal production disruption. A strong focus on safety management resulted in a number of brownfields project relevant safety initiatives being implemented resulting in project completion without a serious injury.

Jan 1, 2002

By A M. van Niekerk, W Mey

Coal mining has an impact on the water management of the water scarce Upper Olifants River Catchment. A prefeasibility study was carried out by Anglo Coal and Ingwe Collieries Limited to establish the water supply and demand in the catchment. A geohydrological model was used for the coalfields to determine the stored water and excess water available. Two distinct collective and treatment systems were proposed for the Witbank and Middelburg municipalities to treat excess water from the Anglo Coal and Ingwe Collieries Limited. The Emalahleni Water Reclamation Project for Witbank was initiated first. Water management and treatment experience gained at Anglo Coal was the cornerstone to develop the collection, treatment and distribution system. A full enquiry was issued to Keyplan, Veolia, Bateman Africa and IST Technik to construct, commission, operate and maintain a 20 ML/day desalination plant to treat acidic, saline mine waters to a South African National Standard (SANS) 0241 Class 0 potable water. After the technical and financial adjudication, Keyplan were awarded the contract. An integrated regulatory process was adopted through consultation with all the relevant regional and head office staff of the Department of Minerals and Energy, Department of Water Affairs and Forestry and the Mpumalanga Department of Land Affairs via an authorityÆs steering committee. A rock engineering evaluation was done to select both the plant and waste disposal sites as all possible sites are undermined. Various contracts are required with the individual mines for water supply, the Emalahleni Local Municipality for the delivery of potable water and for the disposal of wastes.

Jan 1, 2006

By Buizen M

An investigation into the mechanics of sub-surface deformation caused by caving of the extracted area behind retreating longwall faces has been completed by the Subsidence Engineering Section of the New South Wales (NSW) Department of Minerals and Energy. Changes in strata bulk permeability were also measured by standard packer tests undertaken before and after mining. The strata movement was measured by a multi-wire borehole instrumentation system consisting of mechanical anchors installed at different horizons in a borehole extending from the surface to the coal seam. The mechanical anchors were collected to suspended weights on the surface by stainless steel multi-strand wires. The movement of these weights was monitored as the longwall face approached and retreated past the borehole. The anchors did not move significantly until the face went past the borehole. For subcritical extraction geometry with the extraction width to mining depth ratio of 124, the caving zone extended to roughly 9 times the extracted seam thickness above the seam roof. Tensile strains within the overburden tended to be much more closely related to stratigraphy than to the proximity to the extracted seam roof. Larger tensile strains were associated with layers of sandstone, siltstone and conglomerate, whereas layers of mudstones, claystones and coal underwent much smaller strains indicating subsidence in blocks. A beller correlation was observed between pre-mining Rock Quality Designation and permeability than between rock type and permeability. This correlation was less evident in the post-mining core logs. There was an overall increase in bulk permeability after mining.

Jan 1, 1990