Search Documents

By Brown N. R

This paper attempts to highlight some of the problems encountered in the economic exploitation of the deeper coal seams by opencast mining methods. The major cost elements of three methods of overburden removal are examined in relation to the overall cost of winning coal from deeper-lying coal seams. The three overburden removal methods examined are dragline stripping and two systems combining dragline stripping with shovels and trucks at varying depths of overburden. A dragline is, undoubtedly, the most cost effective system of overburden removal for depths of up to 30 metres but it is suggested that, when dealing with incremental overburden depths in excess of 30 metres, engineers should consider carefully the possibility of using a shovel and truck operation, or other system, to augment the use of a dragline.

Jan 1, 1986

By Thomson I. R R, Friday R. G, Palmer W. T

The paper introduces the problems encountered in designing open stopes and briefly examines the factors that determine the final stope dimensions achieved after mining is completed. A case study is presented where monitoring of a stope was considered necessary due to the expected formation of a highly stressed crown pillar above the stope. The influence, on the mining approach adopted, of a yielding crown pillar is discussed. Monitoring and numerical modelling were used to develop an understanding of the behaviour of the particular stope as mining progressed. A comparison between the measured displacements and the numerical predictions at an interim stage of mining was carried out to assist in choosing the final sequences involved in completing the stope.

Jan 1, 1981

By D Kepert, C Simpson, D Edwards

Channel iron deposits (CID) currently supply over 40 per cent of the seaborne iron ore trade out of the Hamersley Province. The two well documented producing systems (Robe and Marillana palaeochannels) were both discovered during early reconnaissance mapping principally by BHP Billiton (BHPB) and Geological Survey of Western Australia (GSWA) during the mid 1950s to early 1960s. Both crop out extensively over the majority of their length. Hot on the heels of Fortescue Metals Group 2004 - 2005 discovery of approximately 2.6 billion tonnes (Bt) of undercover iron ore mineralisation in the Chichester Range, the Fortescue Exploration Department turned its attention elsewhere throughout the Hamersley Province. Reappraisal and analysis of publicly available data and ground truthing of developing models led to the recognition of the Solomon palaeochannel system. Subsequent exploration defined a world-class Resource of some 1.9 Bt of iron ore mineralisation of which the great majority is buried CID. Apart from the Marillana CID system, the Solomon region is the only major CID with significant tonnes of sub two per cent alumina CID with over 500 Mt delineated to date. Exploration has also outlined significant supergene bedded and detrital iron ore mineralisation. Ongoing drilling is expected to increase the resource base both in terms of tonnes and confidence. This paper outlines the principal contributing factors which led to the discovery of the Solomon CID and compares its geology with the Robe and Marillana palaeochannel systems.

Jan 1, 2009

By D A. Sketchley

The Merlin Zone, a 2008 high-grade Mo-Re discovery, is a part of the Mount Dore Deposit in the Eastern Succession of the Mount Isa Inlier in Queensland, Australia. Hosted by carbonaceous metapelites and phyllites, the Merlin mineralisation comprises molybdenite veins, breccia infillings, stylolitic fracture fillings, and disseminations. Because rhenium is geochemically similar to molybdenum and commonly associated with it, global production of rhenium has been mostly a by-product of molybdenum refining. The high-grade rhenium in the Merlin Zone is an exciting discovery that is expected to become a direct source of rhenium. At the time of discovery, quality assurance (QA) procedures for rhenium were not in place at the Merlin Zone; therefore, they needed to be developed.The Merlin Zone was discovered using reverse circulation drilling, which led to concerns about molybdenite loss due to poor sample recovery. The twinning of the discovery hole with diamond core demonstrated a two-fold increase in molybdenum grade over several tens of metres. Consequently, the resources of the Merlin Zone were defined using assays from diamond drill core.Early analytical work, which was initially done only for molybdenum, comprised geochemical analysis with an aqua regia digestion, which have poor precision and can be biased low. Although initial testing for rhenium used similar procedures to those for molybdenum, a scarcity of commercial rhenium reference materials led to a validation process using neutron activation analyses and different digestions. This resulted in introduction of four-acid digestion assays, development of matrix-matched reference materials, and improvements to the quality of molybdenum and rhenium assays for reporting resources. Coarse and pulp duplicates were used to check for sampling bias and to ensure that levels of precision were adequate for the style of mineralisation and analytical methods. In addition, the direct and consistent geochemical correlation between molybdenum and rhenium provided another method for checking analyses.

Aug 22, 2011

Underground mine ventilation is now com monly simulated on a digital computer. Such a programme, incorporating natural ventilation has been modified by others to account for methane emission and elevated local tempera- tures. At Wollongong University, the pro- gramme was further developed and extensive interactive graphics incorporated such that any view of the three dimensional mine could be viewed, and superimposed upon that view are areas where a nominated parameter has exceeded a particular value - generally at a nominated time after a particular event and usually a fire/explosion of one type or another. A further programme was developed such that up to 20 'times' could be examined at a particu- lar location after say, a fuel rich fire at some other place in the mine. The output from this programme includes a plot of methane 1, smoke 1, temperature, pressure and air flow versus time - a most useful graphic to observe the limits of safe attendance in a particular Airway.

Jan 1, 1983

By J A. Sanchidrián

The general ranges of validity of some distribution functions are assessed from their behaviour with 119 sets of fragmentation data from bench blasting obtained by sieving. The emphasis is on determining the lower size/passing limit that the size-scaled Rosin-Rammler, Grady and Swebrec functions, and their bi-component versions, can represent with reasonable precision. By fitting these functions to the data using different weights, the accuracy of the fit varies in the different size/passing zones, so that an overall knowledge of the capacity of the function is obtained across the whole size range, from the coarse zone to the fines. Reasonable ranges of use of bimodal Rosin-Rammler and extended Swebrec (all of them five-parameter, bi-component distributions) are, in terms of percentage passing p, 99 > p > 2 per cent (up to 100 per cent for the extended Swebrec), or 90 > p > 0.5 per cent, in which the expected error of the calculated size is below 15 per cent in the extremes of the range, and less than five per cent in most of the central range; maximum errors (ie errors that will only rarely be exceeded) are typically less than 50 per cent in the central range, and up to about 100 per cent in the extremes. Ranges of use for the Swebrec and the size-scaled Rosin-Rammler (three-parameter distributions), with only slightly larger errors than the bi-components, are 100 > p > 5 per cent or 80 > p > 2 per cent. The classical two-parameter Rosin-Rammler can be used in the range 95 > p > 20 per cent or 90 > p > 10 per cent, with expected and maximum errors less than about 15 per cent and 100 per cent respectively.CITATION:Sanchidrián, J A, 2015. Ranges of validity of some distribution functions for blast-fragmented rock, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 741–748 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By I T. Ross

Sampling drawpoints in block cave mines has been a contentious issue for many years. Doubts have been expressed as to the validity of the process used at most mines. This paper outlines the sampling practice commonly in use, discusses the resulting issues associated with reconciliation and drawpoint closure decisions. The paper also looks to the future and highlights issues for some block cave mining operations currently planned to have in the order of one thousand active drawpoints. It is likely that these operations will require a new approach to drawpoint sampling. There are several potential technologies currently available although some appear to be better suited than others to replace the current approaches. CITATION:Ross, I T, 2012. Sampling in block cave mines, in Proceedings Sampling 2012 , pp 81-86 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 21, 2012

By B Young

Variable bench heights, interaction with underground workings and a steeply dipping orebody are challenges faced daily by geologists at Xstrata Zinc’s Black Star Open Cut (BSOC) Zinc/Lead/Silver mine in Mount Isa, Queensland.BSOC has been in operation since late 2004 and was developed to extract the surface extents of the Zn/Pb/Ag mineralisation mined in the underground lead mine. To date many large scale stopes and extensive development drives have been intersected and successfully mined. The stratigraphically hosted orebodies strike in a north-north westerly direction, dipping ~75° west. Ore production from the pit is currently at 4.5 Mt/a.Historically, sampling was conducted using a multiple spear technique from blasthole cuttings. This method proved to be relatively reliable when blasting benches at a consistent height, but a requirement to vary bench heights to safely collapse and then mine through underground workings reduced sample representivity to unacceptable levels.The purchase and commissioning of a production rig which had been converted for reverse circulation (RC) has allowed for the flexibility of a small rig, with the capacity to easily drill 48 m holes while ensuring sample quality. Sample quality is not the only benefit of introducing RC grade control. By collecting grade control data well in advance, informed decisions can be made by planning, drill and blast and mining departments weeks beforehand, rather than hours before firing. Additionally, seeking operational value to offset higher drilling costs has proved positive with benefits including increased confidence in orebody wireframes, accurate tonnage and grade for proceeding five benches along with the ability to representatively test metallurgical response on a tight grid spacing.

Aug 22, 2011

The purpose of this paper is to look at the costs of tailings disposal, and in particular the comparative costs of different disposal methods in different situations. Costs are often the hidden design parameter. We know that they are important but sometimes feel that it is not very respectable to talk about them in public. It is better from a public relations point of view for it to appear that the decision-making process is driven by environmental factors or best practice rather than looking for the cheapest option. But this presumes that the two are mutually exclusive and this need not be so. These issues are discussed later in the paper. It is also commonplace for the scale of the mining operation to change with time, typically involving increased throughput rates and total tonnage. New ideas in tailings disposal make their appearance. The regulatory attitude can change. Having made a decision about the disposal method at the time of original feasibility study and design it is easy to suppose that the mine is æstuck with itÆ. But that also need not necessarily be so. Careful costing of options may reveal that a switch in method could be cheaper in the long run. The designer will often tend to think in terms of initial earthworks and site development costs. Aspects of power consumption, labour, and periodic campaigns to move tailings pipelines and carry out embankment raises are either overlooked or not given the same emphasis. This can distort the evaluation process. It is productive to think in terms of dollars or cents per tonne as a basis of comparison, not just the total sums. Tailings disposal can cost from as little as 10 - 20 ó/t to over $1.00/t which is a big range. There may be good and unavoidable reasons for the high figure but there would need to be to justify being so far over the industry average. At the same time, mining and processing costs, at least for gold, are around $15 - 20/t. Viewed from this perspective tailings disposal will always be a relatively small component of the annual budget.

Jan 1, 2000

Most compact bucket wheel excavators in use are in the small to medium range. Large compact bucket wheel excavators compete directly with con- ventional longer boom excavators which have operational advantages over the large compact. There are, however, situations where the large com- pact excavator is viable. In the development of these large compacts there are a number of technical features to be addressed. In addition the SECV now propose to expand the concept to a large compact bucket wheel excavator with a bridge and loading unit for their Loy Yang Open Cut.

Jan 1, 1989

By B Harvey

Achieving community and stakeholder endorsement during life-of-mine planning and implementation requires a business-connected approach, as opposed to charitable giving, disconnected offsets and environmental adventurism.CITATION:Harvey, B, 2014. Extractive companies, development and environmental agendas, in Proceedings Life-of-Mine 2014 , pp 19–22 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 16, 2014

By H Tran

Local communities are undertaking an increased role in mine project decision making processes, associated with growing pressure and expectations from regulators, financiers and the general public. This is particularly evident in international projects within developing economies. Environmental and social issues are often complex. Solutions demand difficult choices and trade-offs between sustainable development dimensions: economic growth, social equity and environmental integrity. Proactive stakeholder engagement can play a critical role in assisting decision-makers in determining the operational reality of sustainable development by jointly exploring project trade-offs between proponents and affected stakeholders. Good stakeholder engagement has other potential benefits, ranging from reduced financial risk due to regulator delays, legal disputes or negative publicity to increasing market share through good public image. Approaches to consultation and disclosure have changed from short-term regulatory based focuses, to longer-term, strategic tools for relationship building, proactive risk management and new business identification. Approaches to consultation form a significant opportunity to contribute to overall social sustainability. This paper discusses, based on authorsÆ experience, the broader concept of stakeholder engagement and its contribution to social sustainability of the mining industry. The focus is on key considerations for an effective stakeholder engagement. Three case studies outline how broad based, proactive stakeholder engagement can contribute to improved operation and overall sustainability. The case studies include: a greenfields project in Ghana; a long-term mine in Australia; and an open-pit mine in Vietnam.

Jan 1, 2009

For over 50 years R W Miller & Co Pty Ltd operated old coal properties abandoned by former owners as uneconomic, some of which dated back to the last century. The companyÆs ability to survive with what were relatively poor quality coal resources required a small efficient management organisation. In 1970 R W Miller was involved in negotiations with other coal companies through coal sales contracts to develop private coal areas under the provisions of the old Coal Mining Act (1906) and these efforts led to the development of Lemington colliery. At the same time development of the Ironbark colliery holding near Newcastle commenced. In 1971, R W Miller approached the New South Wales Government for a resource replacement area to prospect for coal in the Upper Hunter Valley. Authorisation No 33 was finally granted on 30 September 1975, but the company found the area was inaccessible as most of the surface was owned by the Australian Army. Later R W Miller was granted Authorisation 66 of 2167.5 hectares at Mount Thorley near Singleton on 1 November 1976. The development of this coal mining project coincided with the second OPEC oil crisis in 1978 and a short-term boom for coal resources and the unrealistic expectations generated by the boom. This paper gives a broad outline of the development of the Mount Thorley project between 1976 to 1986 including the feasibility study and the many governmental and industrial delays that resulted in a three-year time overrun in the project development period.

Jan 1, 1998

By Waghorne E. P

The State Electricity Commission of Victoria is Australia's largest single coal producer. Approximately 19 Mt of coal will be produced in 1989 from the SEC V's newest mine, Loy Yang Open Cut (LYOC), which com- menced overburden stripping operation in October 1982. When the adja- cent Loy Yang Power Station is completed in the late 1990's, LYOC will supply between 35 to 45 Mt/a, depending on power station performance and demand of coal for non-power generation uses. LYOC has been a major challenge for the SECV. It is the biggest single open pit coal mining development undertaken in Australia, with a whole of life capital cost approaching A$1 billion. The mine has supplied a very rapidly growing demand for coal from the expanding power station while developing in breadth, length and depth. Coal demand has consistently been above the figures anticipated during the initial planning because of the substantially improved performance of the 500 MW units of the Loy Yang A Power Station. The superior performance of the LYOC and power station has generated additional electrical energy during the first 5 years of power station operation compared with the initial planning targets- at almost no additional capital cost. This has been a major benefit to the SECV. LYOC will continue to present major challenges for the SECV, particularly in achieving overburden removal and coal reserve targets as development of the open cut continues to full depth over the next 15 years.

Jan 1, 1989

By R D. Morri, D J. Alexander

The design and optimisation of mineral flotation circuits is currently performed using a combination of laboratory, pilot plant and full scale testing. Owing to the variable nature of flotation circuits and the complex nature of the flotation process, it is difficult to interpret the data collected from flotation testwork. JKSimFloat is a computer modelling package which is being developed to interpret flotation testwork data collected at the various stages of the mining cycle. The parameters derived from the program can be used to assess potential circuit configurations in both the design of new flotation circuits and in the refinement of existing operations. The aim of this paper is to outline the modelling methodology used in JKSimFloat and to outline how it can be used effectively to model data collected from either the laboratory, the pilot plant or the existing flotation circuit. The use of flotation model parameters in circuit evaluation will be demonstrated via the use of a case study based on data collected from ComincoÆs Red Dog lead flotation circuit.

Jan 1, 1998

By J deVries, A Broodryk, P Kyselica, K McLean

Gwalia gold mine is located close to the town of Leonora in the Goldfields region of Western Australia, some 830 km from Perth. The mine is wholly owned by St Barbara Ltd, an Australian Securities Exchange listed gold producer and explorer. The Gwalia mine is a deep, all-trucking mine and is serviced by a 10 km long decline from surface. Mining is currently 1540 m below surface. Reserves extend to 1820 m below surface and are open at depth. The mine produces in excess of 200 koz of gold per annum.The Leonora area is hot and arid, with a mean annual rainfall of 230 mm and a 95 per cent mean daily maximum temperature of 20.3°C wet-bulb and 35.6°C dry-bulb.The primary ventilation system comprises a 490 kg/s surface exhaust fan, which draws air down a parallel intake system consisting of the decline, and a dedicated fresh-air intake system extending to the bottom of the production zone. Cooling is provided via a surface bulk air cooler serviced by an ammonia refrigeration plant that delivers 150 kg/s of chilled water to the bulk air cooler.The refrigeration plant and bulk air cooler were installed in 2008. The design allows cooling to be increased over time by installing an additional refrigeration plant in a lead lag configuration with the current refrigeration plant when required.Since 2008, expansion and increased depth reached a point where the underground heat load exceeded the installed capacity of the existing 4.0 megawatt rated (MWR) refrigeration plant. In order to maintain the mine design conditions underground, upgrading of the existing refrigeration system was required to bring the cooling capacity to 7.5 MWR.Two expansion options were considered: the addition of an ammonia vapour-compression refrigeration machine similar to the existing one or a lithium bromide absorption refrigeration system using waste heat from the site power station. The original design and layout of equipment on-site meant that either could be used, allowing an assessment of the merits of both when additional cooling was required.The decision was made to install a lithium bromide absorption system on the lead side of the existing ammonia refrigeration plant. This arrangement provides considerable economic benefits, including reductions in site-generated electrical power, generator fuel consumption and carbon dioxide emissions.This paper details the planning, design, installation and commissioning of the absorption chillers.CITATION:Broodryk, A, deVries, J, Kyselica, P and McLean, K, 2015. The design, installation and commissioning of an absorption refrigeration system at Gwalia gold mine in Western Australia, in Proceedings The Australian Mine Ventilation Conference, pp 193–200 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 31, 2015

By B W. Atkinson

Full-stream mechanised sampling apparatus, that collect a full cross-sectional increment from the complete screen discharge, will always be the preferred option for sampling screen overflows. However, the reality is that provisions for automated sampling are rarely, if ever, provided at the discharges of individual screens within beneficiation plants.Sampling from the discharge of high capacity vibrating screens, especially multi-slope screens, is subject to sampling bias, due to the stratification of the ore that occurs on the vibrating screen deck. The stratification in the vibrating bed translates to a stratified falling stream at the discharge end of the screen, typically with smaller particles at the back of the falling stream and large particles at the front of the falling stream (Figure 1).The chemical and physical characteristics of heterogeneous ore (mineral or coal) particles vary significantly with particle size. If samples do not correctly reflect the source material size distribution, they will be biased and the resulting analytical/assay data will not reflect the actual physical nor chemical characteristics of the source material.Prior published data for coal preparation research (Australian Coal Association Research Program) has demonstrated that a bias appears to exist for samples collected from high capacity multi-slope screens.A new form of sampling scoop has been developed with the aim of overcoming this issue.Bias was evaluated at a coal preparation plant by comparing the desliming screen overflow size distribution to that for æreferenceÆ coal preparation plant feed samples collected using the recognised stopped-belt technique. The study procured 20 sets of comparison samples in order to ensure statistical relevance.Two forms of sampling device were employed for the multislope screen discharge.A conventional square aperture scoop was demonstrated to exhibit a significant coarse bias, in that the resulting samples exhibited a significantly coarser size distribution compared to the reference samples. In other words it was evident that the conventional scoop æfavouredÆ material from the front of the falling stream.A new æcollapsibleÆ sample scoop was evaluated in parallel, and its samples were found to exhibit no relevant bias.CITATION:Atkinson, B W and Swanson, A R, 2012. A new method for sampling from high capacity screens, in Proceedings Sampling 2012 , pp 89-94 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 21, 2012

By J Rutter, S Dunham

Technological advances in sensor and material handling technology has enabled a step change in mine operations performance. Sensors capable of monitoring the grade of broken rock mass can be mounted on shovels, truck loading units or conveyors allowing highly precise ore/waste decisions to be made on small parcels of rock, increasing selectivity. This increased selectivity has the potential to remove sub-economic material from the product stream prior to incurring ore treatment costs. Bulk ore sorting is capable of intervening at <10t “pods” on Run Of Mine conveyors, or alternatively at per bucket loading (5-100t) or truck scale (30-350t) parcels of ore. This Grade Engineering technique being developed by CRCORE (Rutter, 2017) can improve mill feed grade, remove deleterious materials and ensure that the high capital intensity ore treatment facility is presented with the best ore feed strategy. While this technology can improve mine economics, estimating the performance of a bulk ore sorting system is challenging. Traditional resource estimation practices such as Ordinary Kriging and Inverse distance weighting (IDW) are based on weighted averages, a process that smooths the grade profile, reducing modelled variance and dispersion. Its purpose is to generate a globally unbiased result but is less suited to generating a model of adequate granularity to enable confidence in local grade heterogeneity. This is an essential component for bulk ore sorting success. Estimating ore sorting performance requires knowledge of the grade-tonnage curve at the scale of the sensor diversion unit (SDU). Evaluation based on an estimator that smooths the SDU distribution will not correctly predict ore/waste separation or economic performance. Alternatives to traditional linear geostatistics have been tested on a variety of mineralisation styles. Additionally, a number of heterogeneity metrics have been developed to assist with evaluation and assessment. The difference between estimation for grade (metal) and modelling for traditional mining block models, versus methods used for predicting heterogeneity and variability are explored.

Nov 10, 2020

By Dolan P

Various operating practices have been developed over many years to ensure safe and efficient production from the 1100 orebody. Some of these practices are described.

Jan 1, 1982

By R Durchholz, A-J Heiertz, R Schmitz

Mining of lignite is the largest bulk materials handling activity in Europe. In order to mine this lignite, with an average calorific value of only a third of bituminous coal in an economical way, highly efficient opencast mining technology is mandatory. The total continuous mining of overburden and lignite was introduced more than 60 years ago and was subsequently developed stepwise into the largest mass transport system of the world. In 2011, the Inden Mine, one of three RWE Power mines, stripped 90 Mbcm of overburden to produce 22 Mt of lignite. In total, nearly 100 Mt of Lignite was produced from the three mines of RWE Power in Germany. Beside bucket wheel excavators (BWE), several high-performance in-pit crushing and conveying (IPCC) systems, which allow the adoption of continuous mining systems, even for typical shovel and truck (S&amp;T) operations, are available today. RWE Power assists operators considering a change from the S&amp;T to IPCC technology, both in the planning process involving large-scale belt conveyor systems and later with operational know how transfer. In a number of cases, the challenges associated with this system change have been addressed and solved successfully. One key challenge is managing the development of skills for operating the belt conveyor systems efficiently. This paper compares the effectiveness of S&amp;T to different configurations of continuous mining operation for an up to 170 m deep mine with a total annual output of 117 Mbcm. From the mine operatorÆs point-of-view, the quantity and skill level of staffing required for operation and maintenance are discussed in detail. The main conclusion of this paper is the larger the operation becomes and the longer the mine life is, the earlier fully continuous mining systems should be planned and implemented.CITATION:Schmitz, R, Durchholz, R and Heiertz, A-J, 2012. Change challenges for large open pit mines, in Proceedings Eighth Open Pit OperatorsÆ Conference , pp 103-110 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 18, 2012