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By C DahnTr-Lindqvist

The Kiruna mine produced about 19 Mt processed iron ore in 1999 using sublevel caving. General failure in the hangingwall has been widely studied and its mechanism is rather well understood. Failure in the footwall is more recent and not perfectly explained. Plane shear failure and Hoek and BrayÆs circular failure charts were successfully used to match the first surveyed failure surfaces. The footwall is not free yet but covered by a caved waste rock abutment whose exact behaviour is poorly known. Based on new field data and numerical models (FLAC), the following paper presents recent improvements in understanding the Kiruna mineÆs footwall failure process.

Jan 1, 2000

By Preston JC, Richards DJ

A multicommodity exploration programme was mounted in the 1970s by CRA Exploration Pty. Limited over a major part of the southern Murray Basin in Victoria. Commodities sought were brown and black coal, gold, uranium, diamonds, titanium and zirconium rich heavy minerals, and base metals. An area of 40 000 km2 was held under exploration licences by the Company. Exploration techniques used were literature research, airborne magnetics and gamma ray spectrometry, drilling, and geophysical well logging. Targets were defined in both the Tertiary basin sediments and the underlying Palaeozoic sedimentary and igneous rocks. Although exploration is continuing, large resources of brown coal and low grade titanium rich heavy minerals have already been discovered. Exploration for uranium was abandoned in accordance with statutory requirements. The search for significant resources of the other commodities has not been successful.

Jan 1, 1986

By D J. Williams, E M. Rykaart

Soil cover systems are routinely used to reduce acid rock drainage (ARD) from mine waste rock dumps and tailings impoundments. A technology for the analysis, design, instrumentation and monitoring of barrier-type (oxygen limiting) and store/release-type covers has rapidly developed and the number of covers under construction has grown extensively during the past ten years. Mine operators are currently investing in this relatively new technology with the expectation that these covers will reduce long-term liability with respect to acid generation, drainage and treatment costs. While the design life for cover systems may extend into hundreds of years, we have less than ten years of construction experience and proven performance. Some cover designs appear to be functioning well; however, the performance of many more is now being called into question. The paper presented herein evaluates the integrity of cover systems from a global perspective. Soil cover systems for the control of ARD are being constructed at mine sites located within high rainfall equatorial regions, deserts ranging from low to high latitude, humid temperate regions, and cold-continental climates. While the technology for analysis and design of soil cover systems is well developed, factors that compromise the performance of cover systems (in addition to the paramount issue of climate) relate to material selection and availability, cost and construction practices. Long-term performance is also strongly affected by physical stability (ie erosion), volume change (ie cracking, desiccation, settlement and freeze/thaw cycling), vegetation, soil evolution and ecological stability. This paper provides a review of the application of soil cover systems for the control of ARD. Cases where cover systems have been constructed with both success and failure are illustrated. General criteria and recommendations for cover selection, design, construction, and maintenance are provided.

Jan 1, 2003

A fundamental component of grade control at Tarmoola Mine has been the monitoring of assaying through quality assurance programs. The programs have concentrated on issues related to accuracy and precision of leachwell and fire assay techniques, sample preparation and grade variability within a sample. An outcome of monitoring has been identification of shortcomings in the application of assaying techniques to Tarmoola ore types that contain coarse particulate gold. Leachwell has shown satisfactory precision since introduction as the primary assay technique in October 1998 but leachwell accuracy and recovery through comparison with fire assay techniques has identified bias. A bias toward higher fire assays in grades above 2 g/t invoked an investigation into the cause of the discrepancy between leachwell and fire assay. Testwork evaluated Leachwell assay recovery by varying leach time duration, which showed that by increasing the leach time improved recovery significantly. Monitoring of leachwell against fire assay had shown that a leachwell (200 g) with a one hour leach has under-called grade when compared with fire assay by up to 18 per cent, on average, for Tarmoola ore types. Alternatively, optimisation of the leachwell assaying technique using a 200 g pulp and a two hour leach has returned, on average, higher assays than fire assay by up to eight per cent. Testwork on screen fire assays, duplicate assays and fire assay to extinction has demonstrated assay variability associated with coarse, particulate gold. The variability and distribution of gold in Tarmoola ore types has emphasised the importance of high quality sample preparation for leachwell assaying to ensure liberation of gold to leaching solutions. Assay quality assurance protocols are vital to assay data integrity and enable confidence in delineation of ore-waste boundaries and provide early recognition of problematic assaying periods and isolation of grade control practices, which depart from performance standards critical to the operation.

Jan 1, 2000

By Y M. Wang, W Z. Liu, L F. Li, X L. Zhang

Based on the blasting crater theory, the equation between k under typical cases and burden line, charge height was obtained by open pit bench blasting analysis model. The model was calculated with mine production blasting. The blastability coefficient k and the best range of blasting burden line were specially emphasised on determination of lateral crater tests.CITATION:Wang, Y M, Liu, W Z, Zhang, X L and Li, L F, 2015. Application of lateral crater test in open pit blasting parameters optimisation, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 463–468 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By C G. Ferguson, S L. Makin

The Cawse nickel project is a new generation pressure acid leach (PAL), solvent extraction and electrowinning process used to produce LME grade nickel metal and cobalt sulphide concentrate containing 40 per cent cobalt by treating nickel and cobalt oxide ores from a lateritic ultramafic profile. The project is located 50 kilometres NW of Kalgoorlie in Western Australia. The commercial success of the Cawse nickel operation is dependent in part upon the ability of the principal ore type to be beneficiated. A simple process of rejecting lower grade material on the basis of particle size achieves this. The process is called upgrading and allows subgrade material to become commercial ore grade and also allows higher ore grades to be processed in the early parts of the operation. The success of the upgrade process is dependent upon the physical and chemical properties of the ore being processed and the nickel grade of the ore. The upgrade ore type represents >80 per cent of the Cawse nickel resource and is hosted mostly within a limonite unit, represented by goethitic clays in the upper saprolite zone. In the upgrade processing circuit the ore is crushed and slurried. It is then passed over a series of screens that remove all material over 0.5 mm. This ensures that coarse material is removed from the main ore stream. Upgrade is reliant on selectively rejecting lower grade or barren material, which can include silica, magnesite and relict saprock. To predict leach feedgrade, the grade control estimates the head grade and upgrade percentage for all ore delivered to the run of mine ore pad. To do this reverse circulation (RC) drill holes are logged for ore type, assayed for a range of elements and undergo simulated upgrade testwork. The percentage and grade of material rejected through the upgrade circuit has the most influence on upgrade per cent. This reject is determined by the physical properties of the rock mass and drum scrubber parameters. The correlation between nickel upgrade and reject can be established to predict upgrade from the known mass reject. Parcels of upgrade ore milled to date closely follow projected correlation trends. Upgrade circuit results have been excellent, with average nickel grades upgrading by 34 per cent, cobalt by 23 per cent, with 55 per cent mass passing.

Jan 1, 2000

The theme of this paper is the development of-the project feasibility study which includes discussion of the work which is carried out in preparing the project feasibility study, the necessary evaluations and structures that are employed to ensure that not only does the feasibility study itself stand up to scrutiny and is sound, but also that the investment the company is proposing to develop, "the project", is an investment decision which will represent good returns to the company. This theme is particularly relevant when there are competing divisions within the company and only limited cash resources are available to make the correct investment decision. Thus various potential investments may be evaluated against each other to determine which project will be given the go ahead for development. This paper will particularly focus on the various investment analysis techniques that are used and discuss the work that is required in preparing the project feasibility study and specifically the interaction of the project team members and the thought process that must be undertaken to complete the project feasibility study. Finally comments will be made on tax planning issues particularly with respect to taxation of gold production to be introduced in January 1991. Some ideas are presented which may help and possibly improve the financial position of the projects being reviewed. Further, it is suggested that the thought process which goes with the financial engineering aspects of a resource project can be widened to take account of taxation issues and tax planning to ensure the rise of the project feasibility and hence the decision to proceed to development by the project sponsors.

Jan 1, 1990

The successful operation of diesel equipment underground does not entirely depend on selection of robust, reliable, easily maintained machines. Results are also heavily influenced by the following factors: Design and condition of the operating area. Skill of operators. Correct maintenance facilities. Experience, skill and initiative of maintenance personnel. If the mine layout does not allow access to a central workshop area, the effect of any shortcomings will be magnified. The best results will only be obtained by close co-operation between mining and maintenance departments right from the initial planning stages.

Jan 1, 1977

By J Isles, S King, A Valenza, R Lawolo, J Evert

PT Nusa Halmahera Minerals (PT NHM) is an Indonesian joint venture company owned by a subsidiary of Newcrest Mining Limited (75 per cent) and PT Aneka Tambang (Persero) (25 per cent). PT NHM operates two underground gold mines, Kencana and Toguraci at the Gosowong mine site in North Halmahera District, North Maluku Province, Indonesia.The Toguraci underground mine development commenced in 2011 with ore production commencing in 2012. Water temperatures ranging from 50°C to 80°C were encountered in the Toguraci open pit associated with the structures containing the gold bearing veins and are believed to be fed from a relic volcanic system one to two kilometres below the mine. Underground development and production has continued to intersect these structures with the result that an integrated programme of geological, hydrogeological modelling and operational project work has been required to dewater the mine ahead of the descending stoping fronts.This paper will detail these programmes.CITATION:Lawolo, R, Isles, J, Evert, J, Valenza, A and King, S, 2017. Hot water management at PT Nusa Halmahera Minerals’ Toguraci Mine, in Proceedings 13th AusIMM Underground Operators’ Conference 2017, pp 191–198 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 16, 2017

By S Wright, W Bruckard

The current status of battery collection and recycling schemes in Australia are explored in light of current developments in product stewardship and increasing pressure to decrease materials going to landfill by originating equipment manufacturers. Used consumer batteries, both single cycle and rechargeable contain a mixture of valuable metals and potentially toxic materials that may become a resource/revenue stream to offset the cost of disposal/recycling. Although the volume of batteries discarded in Australia is modest compared to other global population centres, the expected increase in battery use with increasing equipment portability and future developments in the automotive industry, provide an opportunity to recycle. The requirements for a battery recycling facility in Australia and the most promising processing platforms that may exploit the resource with enough flexibility to cope with battery developments and market trends, are explored.

Jan 1, 2006

By D Rubery, C Croker

The Boddington Gold Mine (BGM) is located 120 km south east of Perth, Western Australia. The operation is managed by Worsley Alumina Pty Ltd and mined by contractor Henry Walker Eltin (HWE). The mine has been operating since 1987 with ore extracted from a series of pits along strike. Ore is contained within the basement rock, which is overlain by a cap rock layer and transition zone. Cap rock and basement zones require blasting.As the mine neared completion, a high-grade deposit was discovered within 50 m of an existing Western Power substation and 100 m from the processing mill. The substation provides power to the Boddington area and is a back-up power supply to the city of Perth. Due to the delicate nature of the transformers located at the power station, overhead power lines and the mill, blasting in the area was considered very high risk. As such blasting needed to be controlled for flyrock, airblast and most importantly peak vibration and frequency limits which had the potential to damage the transformers.The mine was due for closure in March 2001. The decision to mine the pit was based on its high grade, ability to be blended with lowering grades from other pits and changing of the processing technique with the expansion. This decision extended the life for a further six months.Due to the high potential risks a detailed risk assessment was conducted by Orica, Worsley and Henry Walker Eltin. The completed assessment and the major design parameters were presented to Western Power for approval. The ability to reduce the blasting risk was focused on limiting of vibration through controlling maximum charge initiated per delay, blast timing and firing direction, and other innovative control measures. OricaÆs SHOTPlan« and Sabrex« computer modelling packages were used to predict the outcome of blasts.The success of this project has opened the doors for other high risk blasting projects, which otherwise may be left unmined.

Jan 1, 2002

By C Moorhead

The classification of Mineral Resource estimates for reporting in accordance with the JORC Code is a statement of the Competent PersonÆs confidence in the estimate and an attempt to convey that confidence to the various users of the resource estimate. In general the classification process is either largely subjective, relying on the Competent PersonÆs experience, or relies on statistical measures derived from the estimation process. These statistical measures may not necessarily relate to the overall confidence in the resource which must also take account of the confidence in the geological inputs to the estimation. Several authors, including Jackson et al (2003) and Dominy, Noppe and Annels (2004), have addressed methods of including consideration of geological data and its reliability into the classification process. Henry and Parker (2005) have discussed a quantitative measure for classification of Measured and Indicated Resources related to mine production parcels. These methods rely on the availability of sufficient information for the application of geostatistics, data evaluation techniques or repeated interpretation of data to provide an indication of confidence. They are suitable for very advanced projects. In 2005, using a modification of the financial audit æcontrol and quality criteriaÆ principles, then widely accepted within Newcrest Mining Limited (Newcrest), the principal author developed a scheme which categorised the classified resources into æcontrolÆ and æqualityÆ (or risk) categories. Control covers all aspects of the data collection, the geological interpretation, the data analysis and the modelling of tonnage and grade; it is also influenced by the documentation of the estimate. The quality criteria are a subjective measure of risk associated with the estimation of the resource and refer to the risk that the tonnage and grade are not realised and the consequences if decisions are made on the basis of these estimates. By evaluating the generally accepted level of risk attributed to these quality ratings by Competent Persons within Newcrest, a graphical representation of the confidence in the resource ounces was prepared for communication of the expected confidence in the resource statement.

Jan 1, 2009

Two events during the past decade have combined to effectively alter the role of the geologist working in Papua New Guinea. The gold boom of the 1980s resulted in a substantial increase in the general awareness at village level of mining companies, gold and landowner issues, and as a consequence of the Bougainville tragedy, landowners are also very much aware of the potential problems of a mining operation in their area. Landowners know they have the power to remove a company from a project area, and government has shown itself to be virtually powerless and unable to help the company effectively. During a considerable proportion of a project's development time, the project geologist is viewed in the eyes of the local community as the 'company'. Good landowner relationships are nurtured over a reasonable time period and the input of the geologist is significant in determining the eventual fate of company-landowner relationships. The initial impressions of the company, gathered by the local community, will have a far reaching impact on the nature and direction of their future exchanges with the company.

Jan 1, 1991

By G Noonan, S Thomas, M Limbert

Stuck drill rods (often referred to as bogged rods) in production ‘upholes’ are a common problem in the underground mining industry. Bogged and broken off drill rods have the potential to fall out of the hole without warning, posing a serious hazard to personnel and equipment below.Current industry practice to alleviate this hazard can be to either grout the hole in order to lock the drill rods in place, or to ‘plate over’ the hole with a rock bolt. Each of these operations seriously delays mine production as both require demobilisation of the production drill and mobilisation of alternative personnel and equipment to address the hazard. Both methods have been assessed for safety and efficiency and were found to be expensive, time consuming and in the case of plating over, ineffective.To address the safety and efficiency short-comings of the traditional practices, the long hole plug (LHP) has been developed to safely secure the lost rods in the hole. The LHP when struck by falling drill rods behaves similar to an expansion shell anchor transferring the axial forces from the falling drill rods horizontally into the rock mass. It is installed using standard production drills allowing work to safely continue with little interruption.Extensive testing has been carried out on the LHP in the laboratory and underground at the Rosebery mine on the west coast of Tasmania, Australia. Testing has included static pull testing, full scale drop testing and underground trials.The outcome of this work has proven the LHPs ability to add safety, volume and cost benefits to the Rosebery underground operation and it is currently in use at that site. It enables proven elimination of a common workplace hazard immediately, thus eliminating delay on the mine’s production cycle.CITATION:Thomas, S, Noonan, G and Limbert, M, 2017. Long hole plug – addressing the hazard of bogged rods in ‘upholes’, in Proceedings 13th AusIMM Underground Operators’ Conference 2017, pp 305–310 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 16, 2017

By K B. Quast

During the prefeasibility stage of the mining cycle for a gold deposit, an evaluation of the ore leaching characteristics from various defined areas is essential prior to plant design. There are a number of simple laboratory tests which have proven successful in establishing gold and silver leaching kinetics, carbon adsorption and fouling, as well as elution characteristics. A number of case studies of carbon-in-pulp (CIP) simulation are presented which show excellent agreement between calculated and assayed gold and silver grades in feed and adsorbed on carbon which validate the methods used.

Jan 1, 1998

By Blackwood R. L, Crichton G. P

In recent years, the value to Australia of the introduction of a system of resource rent taxation on the mining industry has been frequently debated. The forms that this rate of return based tax could take, and the impli- cations on government revenue and mining com- pany profitability have been discussed at some length. Further, the selective application of this taxation scheme to certain mining industry sectors has received considerable attention. This study takes the form of a survey of the taxation history of one significant Australian mining venture, the Mount Lyell Mining and Railway Company. The conditions faced by this company during its history are used as a base for the imposition of rent taxation schemes. Comparisons are drawn between the historical taxation liability of the company and that which would have been incurred if a resource rent form of taxation had been in existence. From the results of the study, it can be concluded that while the company can be con- sidered to have been a successful enterprise during most of its history, it has not achieved a level of profitability which would warrant the collection of any form of excess profits Tax.

Jan 1, 1979

By J Ross

The foundation of effective leadership is communication. You can have all the leadership theories, models and training you want, but in the end it is all about leaders talking to, listening to and understanding the point of view of those below and above them.The foundation of effective safety is peoples’ behaviours. Every incident, every near miss and every safe act comes down to what one person does and how that affects themselves and others. We tend to focus these behavioural considerations on the people at the ‘coal face’, those most in harm’s way. But it is the individual behaviours of everyone in the organisation, particularly those at the top, which are just as (if not more) important. The foundation of effective safety leadership in the mining industry is that it starts at the top, with the individual behaviours of leaders. The behaviours of each and every leader will be reflected in their teams. And where their teams are made up of leaders, these leaders will pass these behaviours on to their teams and so on. It’s the sum total of what people see their leaders do and what they do as a result, that creates the ‘culture’ of the business – and it’s this culture that makes or breaks how safely people work.

Mar 21, 2011

The presence of undetonated explosives in a rock face after firing constitutes a hazard which can result in a fatal or serious accident if undetected before drilling commences.Most accidents caused by drilling into explosives are the result of failure to examine the working face properly and lack of care in subsequent drilling operations; it is not always realized that explosive may be left in the butts of holes or may be driven into cracks or crevices in the rock.Obviously the best means of preventing accidents of this nature is to adopt methods of drilling, charging and firing which will reduce the hazard to a minimum.There are three ways in which undetonated explosives may be left in the rock face, namely:1. Misfires.2. Cut-off shots.3. Incomplete detonation or failure of the charge to propagate throughout.MisfiresNo attempt will be made in this paper to deal fully with the question of the prevention of misfires, as apart from the fact that most of the preventive methods are well known, it is believed that if the miner receives his explosives and means of initiation in good order, and proper care is taken in their use, the failure of a charge to fire will be a rare occurrence. The provision of central fuse capping stations on mines has gone a long way towards the elimination of misfires caused by the mishandling of safety fuse anddetonators.

Jan 1, 1956

Resources and reserves are critical inputs into the determination of an operating mineÆs financial results and balance sheets, but how well understood is this fact. Do the investors, directors, accountants and geologists/engineers responsible for preparing or relying on relevant aspects of the end results properly understand the inputs and outputs and the associated risks that may be established. The first step is to understand how financial reports are impacted. The most obvious, and best known, impact is in the calculation of depreciation and amortisation charges against long term assets. In addition, however, there is a requirement to regularly determine whether asset book values are impaired û this is nearly always performed globally by the preparation of a discounted cashflow model for a mine which is usually based on a mine life as determined from the resource and reserve statement û the particular driver here is normally the short and long term production plans. A key aspect of the short term production plan is that it would normally not assume that the reserve and resource statement implies consistent grade, stripping ratios, etc. However, outside of the early years of a plan, more generic assumptions of these variables are often made in conjunction with the reserve and resource statement. Depending on the timeframe of the detailed production plans, this can have a large impact on a projectÆs net present value. Other financial balances that may also be impacted include restoration and rehabilitation provisions, retrenchment provisions and deferred or equalisation stripping accounts. The age old question of whether all reserves should be used or whether some or all of the resources should be included for financial reporting purposes has never been adequately resolved. It is our view that there should be no prescriptive answer to this question but judgement of all professionals involved in the process needs to be included. Furthermore, the company needs to be able to support their conclusions with well thought out and appropriate answers. This may not be in line with the approach that certain accounting standard setters may be proposing or taking, and this paper will outline the current status of global requirement and the likely future directions. Whether reserves or resources are utilised, does not change the key requirement that those preparing or using reserve and resource statements need to understand key aspects. For example: geologists/engineers do they know how reserves or resources will be used? have they imparted information on variability of key drivers such as grade or depth or dilution? do they know that major financial/business altering decisions may be made based on the analysis? accountants do they understand where the numbers have been derived from and the assumptions that may have been made in their determination? do they understand the degree of accuracy (or inaccuracy) that may exist particularly with resources)? do they understand the history of resource reconciliations and what it may mean for the future? directors do they understand the processes undertaken by the company to prepare the financial report and the interaction between the geologists/engineers and accountants? do they understand the potential sensitivity of results to the input variables? Financial reporting is extremely reliant on the use of the reserves and resources, however, the geologists/engineers, accountants and directors do not always understand the interactions between themselves which may lead to misleading public reporting. More education and communication between various parties is needed.

Jan 1, 2002

By D Teyhan, J Kirsch

Traditionally, most Australian iron ore mining operations have been surface-based. Processing plants were designed to handle dry ores. In recent years mining operations in the Pilbara have progressively moved below the water table exposing wet, sticky ores which have caused lost efficiency in screening operations as particles tend to agglomerate and adhere, blinding screening media. Miners and vibrating screen manufacturers have experimented with a shift from linear motion to elliptical motion screens. Elliptical motion conveys and lifts particles. Effective on flat deck (horizontal and inclined) or sloping decks it can be configured to provide a controlled transport rate, applying pressure in all directions to maximise screening efficiency. In practice, elliptical motion screens have proven to be effective in dislodging sticky particles from screening media, reducing blinding rates and improving screen efficiency. Moisture and clay content change during the life of a mine. These changes are sometimes the effect of seasonal rainfall, in other cases due to increased groundwater and clay content as mining operations go deeper. To compensate for such changes and optimise screen efficiency, changing the ‘shape’ of elliptical screen motion is required. This has traditionally required shutting down processing plants and making mechanical screen adjustments. Plant downtime is costly and machine adjustment has been a ‘trial and error’ practice. This paper will explore the results of a field trial that is currently underway in Brazil of a next generation elliptical motion screen design that allows operators to make changes to exciter rotational direction, speed and screen stroke angle, through electronic drive phase control. The machine’s electronic drive system synchronisation is enhanced for stability with a unique mechanical timing system. Operating at up to 6 g, screen adjustments can be made on the fly without stopping production. Early trial results are showing up to 50 per cent improvement in screen efficiency compared with traditional elliptical motion machines under certain feed conditions.

Aug 24, 2022