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By H Chalcraft, T D. Mullen

Conditions encountered at a recently completed brownfields mining project provided valuable insight into, and development of, techniques for working in and around known underground mining voids in an open cut environment. The careful application of underground blasting principles to a pit environment and successful excavation whilst maintaining appropriate stand-off distances were two primary areas of innovation enabling the success of the project.Mary Mac Hill is a gold deposit situated less than 2 km south-west of the town of Laverton, Western Australia. It is owned and mined by Crescent Gold Limited. Previous underground mining by various other mining companies has left an extensive network of underground horizontal development, subvertical stopes and shafts, some of which daylighted at surface. This was identified as potentially posing substantial risks, which would prevent the application of conventional mining methods. Two major stopes were located under a hard banded iron ridge topped by a peak of cap, connected variously by narrow drives and vertical development. Due to the proximity of the first of these stopes to the surface, its dimensions and governed by procedures and advice provided by externally engaged engineers, Crescent Gold could not access the area of the ridge immediately overlying the stope using conventional open cut mining methods. This was the first of many hurdles surmounted in mining this deposit.The following report outlines how the challenges this geometrically complex deposit presented. Solving these problems enabled the team to mine the contained gold ore to a completed design, without subjecting personnel or mining equipment to harm due to a void breach incident. This paper outlines the numerous complications and difficulties Mary Mac Hill posed and explains the strategies developed to overcome them. The report also presents technical mass blasting details explaining two of the critical crown pillar blasts.CITATION:Mullen, T D and Chalcraft, H, 2012. Mary Mac Hill - The challenges and strategies of successful open cut mining: A complex underground gold deposit riddled with a network of complicated voids, in Proceedings Eighth Open Pit OperatorsÆ Conference , pp 89-96 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 18, 2012

Soil improvement technologies have been widely employed over the recent decades to overcome tunnelling problems in difficult grounds, their range of application growing proportionally to the technological development. The constant advancement in the different mechanical (flexible and more powerful equipment) and electronic (enhanced reliability and direct quality control) aspects of these technologies, fostered the confidence of engineers and tunnellers and, ultimately, allowed the entire tunnel industry to approach difficult excavations in a safer and cost effective manner.This paper outlines the main features of commercially available soil improvement techniques, with particular emphasis on permeation grouting and jet grouting. These two technologies, developed concurrently in Europe and Japan, and there customarily adopted in the design of underground structures, have known extensive and extreme applications worldwide in recent years. Case histories and current practice of soil improvement techniques, as they apply to tunnelling, are also rendered.

Jan 1, 1999

By B Chapman, R Nievergelt, J Hill

A major component of Sydney’s new South West Rail Link project is the Hume Highway Underpass (HHU), an 80 m long twin track mined tunnel excavated at a depth of just 5 m below the pavement of the Hume Highway; one of Australia’s busiest road corridors.In order to ensure a safe and efficient construction of the underpass without disruption to the Hume Highway traffic, design of the HHU required specific focus on the prediction and control of ground movements. This paper describes the design and construction solutions adopted in response to these challenging constraints. The paper also provides discussion on the observed behaviour of the underpass during construction and the results of a back analysis that was undertaken during construction.CITATION:Hill, J, Nievergelt, R and Chapman, B, 2014. Design and construction of Sydney’s South West Rail Link Hume Highway Underpass, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 375–386 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By C D. Pocock

Maintaining catch berm capacity in open pit mines through controlled blasting prevents production delays associated with managing risks associated with wall instability. A method has been developed to quantify the drill hole deviation of presplit holes at Century Mine. Different controlled blasting techniques are used to control wall quality and decrease the risk. The performance of presplit drilling, in terms of deviation from design has been investigated. A methodology has been developed to quantify the drill hole deviation in three dimensions. This methodology was converted into a series of algorithms capable of handling an extensive range of data. The methodology was applied to a case study at Century Mine to evaluate the performance of drilling on two presplit blasts. Overall, 67 drill holes were investigated in the case study. The drill hole deviation was quantified in terms of three parameters: skewness, linearity and drill hole deviation parameter. Methods for quantifying each parameter were developed. Skewness, a measure of the amount of curvature and linearity, was defined as the measure of the consistency of the gradient of the drill hole. Drill hole deviation parameter is defined as the average measured deviation of the surveyed drill hole position from the design position. Acceptable drill hole deviation tolerances for each of the defined parameters were developed by analysing drill hole deviation parameters with respect to implications to catch berm capacity. Verification of the methodology was confirmed through the comparing of the completed drill hole deviation results using both visual inspection and cross analysis for each of the three methods. Holes with an R squared value of less than 0.97 for skewed deviation were classified as having skewed deviation, while holes with a difference in gradient of 3.5 were classified as having linear deviation. The results show that 76 per cent of the drill holes had deviation. Of this, 19 per cent were skewed, 57 per cent had linearity and 12 per cent contained both skewed and linearity deviation.

Nov 8, 2011

By M Andrew, H Reynolds, R Mills

As the global mining industry continues to grapple with ‘black swans’ (high consequence / low frequency events) for health, safety and environmental losses, the focus is shifting from risk assessment of these events to risk management using selected purposeful controls that reduce the risk.Fundamental to critical control management (CCM) is a soundly based rationale for selecting the right controls for each and every risk. The approach should be based on a thorough understanding of the dynamics of the event: What causes it? How frequently will it occur? How likely is the consequence to be realised? This is typically done through a bowtie and methodical numerical risk analysis. Core to this step, then, is the structure and content of the bowtie; specifically, the analytic architecture that is used to construct the bowtie. Different architectures yield different constructions, and bowties are no different.Although bowties for operational health and safety (OHS) hazards appear to have a common architecture, they are not generic. It is important to stress that they contain site specific information, are prepared by site based operational teams, and vary from site to site to reflect each site’s operational conditions. They are often a product of the knowledge and understanding of the operational teams involved, may be prone to human error, and potentially miss latent hazards that may have been embedded early in the planning, design or construction phase of a mine or facility, or within the mining equipment. Overcoming these deficiencies through constant re-evaluation of the risks, and challenging the content on the bowtie will help to minimise the chance that something will be missed.This paper will cover key themes in bowtie architecture, introduce the concept of barrier models for high consequence event (HCE) bowties and present a relevant case study to illustrate the issues that determine quality in bowtie construction and critical control (barrier) selection and management.CITATION:Mills, R, Andrew, M and Reynolds, H, 2016. Can we stop a black swan breeding? Advances in bowties and critical control management, in Proceedings International Mine Management Conference, pp 105-114 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jun 22, 2016

By C Dell

Hillgrove, situated on the New England plateau of New South Wales, is an area rich in history and resources. Key resources are predominantly antimony, gold and scheelite and the area surrounding the historical field is environmentally sensitive and topographically challenging. Since acquiring the Hillgrove leases, Straits Hillgrove Gold has undertaken a significant exploration program on these historical mining areas with the goal to return the field to production. This exploration program has enabled Straits to significantly increase the resource base and has subsequently enabled the planned redevelopment of Hillgrove to be realised. In October 2006, installation of mining infrastructure and the initial stripping of existing development had commenced. To successfully redevelop Hillgrove, Straits has had to adopt a highly mechanised, trackless, diesel mining operation which will see the production rate commence at an initial rate of 250 kt/a of ore from a narrow vein environment. This ore will be processed on site to produce antimony metal, gold bullion and a scheelite concentrate.

Jan 1, 2008

By I Douglas, L Allen

Localised indicator kriging was developed following a similar approach used by Marat Abzalov (2006) in his paper titled æLocalised uniform conditioning (LUC): A new approach for direct modelling of small blocksÆ. Abzalov introduced the idea of mapping panel distributions from uniform conditioning onto selective mining unit-sized blocks that were created using ordinary kriging. This concept of remapping panel distributions was applied to multiple indicator kriging histograms.At Newmont a program was developed that made the remapping of MIK histograms to SMU sized blocks extremely efficient and was subsequently tested on several gold deposits. The results have been encouraging as the localised indicator kriging (LIK) method has eliminated many issues that have plagued both ordinary kriging and multiple indicator kriging. Use of localised indicator kriging methodology limits the smearing of high-grade and the over-smoothing of grade that is common and difficult to control in OK but retains the ability for localising grades. LIK also simplifies change-of-support corrections, eliminates un-mineable slivers of low or high-grade when dealing with small tonnages, and allows for the mapping of linear and non-linear estimates into the same block.

Sep 26, 2011

By R Gilbertson, N Freeman

Metallurgical accounting is key to the control and production planning process of any mining operation. This is even more crucial for complex operations involving mining, concentration, smelting, refining and marketing. The tracking of multiple metal product and contaminant components through the operation can improve process predictability and inventory management. Appropriate use can be made of æhigh quality dataÆ for strategic reserve utilisation, mining operations, milling operations, etc. This information enables the optimisation of all aspects of the mining and processing operations. This case study discusses a metal balance implementation for WMCÆs Olympic Dam operations; a large integrated mining, concentration and refining operation, which used an existing off the shelf statistical data reconciliation package developed for the oil industry. It was extended to track and balance the metal co-products across the entire integrated mining, mineral processing and refining plant. The key benefits discussed are tight integration with existing data collection systems, formalisation of previously informal processes, and leveraging the development and support available for a widely used package. The project provided a solution for the site metallurgical balance spanning the mine and processing plant. The solution facilitates a bridge between the planning and production worlds, using a common data model across the site.

Jan 1, 2002

By J Carswell, K McTyer

The Pajingo gold operation in Queensland is approximately 50 kilometres south of Charters Towers and 134km south-west of Townsville. The resource was discovered in 1983 and first open pit gold production began in 1986. The mine traditionally employed a bottom-up sequence – a combination of modified and traditional Avoca methods with run-of-mine waste backfill. This practice caused many high-grade crown pillars to be left in place, yet accessible. In recent years, these crown pillars have been extracted by injection grouting of rockfill. This process facilitated blind up-hole open stoping. To date, thirteen separate injection campaigns have been completed, of which ten were deemed successful. In general, the two key technical difficulties in this mining technique are: maintaining a consistent high-quality ground consolidation of the rock fill material; and controlling the drill and blast practices during stoping. Here, effective drill-and-blast control was found to be essential to achieve the dual aims of 100% extraction, and maximum sill pillar stability to minimise dilution. During stoping, the technical performance of the consolidated rock-fill was recorded; both to verify the design, and to identify operational improvements. The results showed that Pajingo has realised both reduced production down-time through use of early strength gain grout, and more rapid and thorough grout consolidation through changes to the emplacement method. The optimisation of consolidated rock fill has led to several quantifiable benefits to the mine, including: profitable extraction of previously sterilised crown pillars resulting in both increased ore reserves and production profile; improvements to the stability of grouted stope crowns, thereby reducing safety and production related; risks associated with open up-hole stopes; reduction in cost and time constraints, with respect to the grouting of loose fill; and reduction in grout curing time – from 14 days to 8 days – thereby minimising production down-time. This paper is a case study of the evolution and optimisation of the up-hole open stoping mining method at Pajingo. The challenges and successes are discussed in terms of their key mining outcomes. CITATION:McTyer, K and Carswell, J, 2018. Evolution of rock fill consolidation at Pajingo Gold Mine, in Proceedings The Fourth Australasian Ground Control in Mining Conference (AusRock), pp 66–77 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 30, 2018

By P Lukic

The definition of the working sections that will be used in a mine is usually initially made in the field by the geologist supervising the drilling program. These initial definitions are often made on the basis of rules of thumb such as æcoal less than 30 cm thick cannot be mined separatelyÆ; æpartings more than 30 cm thick will be mined separatelyÆ; and æif a coal seam is less than 50 cm thick and the parting above or below is thicker than the coal, the coal will be wastedÆ. These decisions are also often made based on the requirement for a minimum sample mass for analysis, and the desire to collect data at the minimum resolution to conserve the exploration budget.In many cases the geological models based on this data are produced at a resolution that is inadequate to allow the mining engineer to produce a mine plan that will maximise project value. This problem is generally unrecognised.Where data is collected to a higher level of resolution the subsequent processes employed in the production of geological models and mine plans often discards the inherent value that is hidden in this data. Again this problem is generally unrecognised.This paper highlights this problem and then presents a methodology that ensures that the optimal working section is selected and compares the outcomes of applying this methodology versus adherence to the usual rules of thumb.

Sep 26, 2011

By T Seifert, P Krolop, K Niiranen, S Gilbricht

The Per Geijer iron oxide apatite deposits (IOA) display significant potential mineral resources for Luossavaara-Kiirunavaara AB (publ), known as LKAB. LKAB continuously mines magnetite/hematite ores in northern Sweden for almost 130 years. The Per Geijer deposits reveal a high phosphorus content and vary from magnetite-dominated to hematite-dominated ores, respectively. Furthermore, they show a large variation in texture, mineral composition, and relation to wall rocks. The high phosphorus concentration of these ores results from highly elevated content of apatite as gangue mineral. Reliable, robust, and qualitative characterisation of the mineralisation is required as these ores inherit complex mineralogical and textural features. For this purpose, comminution tests at laboratory scale in combination with scanning electron microscopy-mineral liberation analysis (SEMMLA) were carried out. Based on this work, significant information on the modal mineralogy and degree of liberation of minerals of economic interest (eg magnetite, hematite, and apatite) were obtained. Results show that there is a difference in the degree of liberation of magnetite and hematite between ore types. This seems to be dependent both on the size fractions and the dominance of each iron oxide in the individual ore type. The amount of gangue minerals seems to have no significant impact on the degree of liberation after comminution. Apatite is generally best liberated in ore types associated with silicates, regardless of magnetite or hematite dominance. Based on the results of this study it can be inferred that a high degree of liberation of the minerals of economic interest can be achieved. However, results need to be verified with further beneficiation steps such magnetic separation, apatite flotation and possibly reverse silicate flotation.

Nov 8, 2021

By S L. Martin, M Wimberger

The binary indicator coding of assay and lithological data according to a single criterion or multiple criteria is a powerful technique for representing mineralised shapes through the modelling of probabilities. This can be as simple as using a single indicator to model the probability of occurrence of a condition, usually a grade threshold or a lithology, but it can also be used with a number of categories. Case studies are presented to show the power of this approach, where the geological controls on mineralisation or on the distribution of a rocktype or alteration, often coupled with mineralisation, are unclear. The categorical approach is often used as a de facto grade filter in disseminated or stockwork mineralisation. The ultimate expression of the indicator formalism is in multiple indicator kriging (MIK), where a conditional distribution of probabilities is generated for each estimation panel. This has applications in recoverable resource estimation, as the input for continuous or categorical simulation, where the distribution of sample grades is multimodal, or when there are superimposed mineralisation events with different orientations. However, in some cases, MIK is being used as an excuse for ignoring a quality geological interpretation. Examples from the public domain show the abuse of the categorical and MIK approaches to modelling probabilities, together with a plea for greater consideration of the geology.

Mar 22, 2022

By Little T. N

The Western Australian School of Mines is continuing to investigate the blasting techniques and mining strategies that are used for ore/waste separation (or high grade/low grade ore separation) or to prevent ore and waste mixing. The aim of all the mining strategies is to produce an optimum product. The optimum product is one which contains no diluent and undergoes no mixing of the various identified ore and waste blocks and is fully recovered at the minimum overall operating cost. The current study includes the use of computerised Knowledge Based Systems (KBS) technology to assist the user with the blast technique selection and blast design process. These aspects are highly dependent on the geology. (geometry, rock mass properties, grade distribution), explosive performance and the expectations of the mining company in terms of production rates and equipment utilisation. Most of these factors are not well defined and nor are they easy to quantify. However, a large amount of knowledge does exist and is available in the following forms: rules of thumb, empirical formulae, engineering judgement and past experience. KBS techniques are well adapted to handle such"forms of knowledge. The primary objective of this paper is to illustrate an approach for the use of Knowledge Based Systems during the analysis and interpretation stages of the blast design process. In particular, the components and methodology of the developed system are described for selective open pit gold mining. The Knowledge Based System developed was written using the declarative programming language PROLOG.

Jan 1, 1990

BHP Steel International's Newcastle blast. furnaces have operated since their caimissioning on cake based on local low rank coals. In the early 1960's Newcastle coke was believed to be the weakest in the world. Newcastle coke now supports a blast furnace operation with a productivity of 2.1 t/d.rn IV, a fuel rate of 490 kg/t and a coke rate of 415 kg/t. This coke is nuudv from blonds of lcxni and southern Sydney basin coals with blend Ro nex in the range 0.94 - 1.01. Blast furnace performance in periods of differing coal blends is conjured. The relationship between coal aril coke quality indices and blast. fin-mice perforrnarcc.e is discussed as well as the relevance of conventional coke tests. New BHP coke tests are referred to.

Jan 1, 1987

By L Y. Yang, Z Wang

This work presents the fundamental properties of CITIC magnetite concentrate and its performance in pelletising and sintering. CITIC concentrate has been widely used in pelletising to produce pellets for blast furnaces. It is also used in sintering to benefit from its sintering performance. CITIC concentrate has excellent balling properties owing to its size distribution, particle surface properties, large specific surface area and balling index, leading to strong green pellets and product pellets. When used in sintering at appropriate levels, sinter bed permeability improves, productivity is increased while coke consumption reduces, and sinter strength improves.

Nov 8, 2021

By N Power, R Hassell, E Jones

Wiluna Mining Corporation are progressively re-entering the old Wiluna underground mining complex. The existing underground was abandoned in 2013 by previous owners and left to flood with water levels reaching above the East Pit portal and Happy Jack Pit portal and up to 300 m below surface in the Bulletin underground. Re-entering the mine commenced in 2017 with dewatering of the Bulletin decline. The underground development had been previously supported with friction bolts, with weld mesh in places. Until mid-2021 rehabilitation requirements were based on an external visual inspection of the installed ground support scheme. However, several incidents involving falls of ground due to corroded bolts have occurred during this time, showing that this approach was inadequate. The challenge the operation faced was should the entire decline be rehabilitated, the implication being not only a large rehabilitation cost but also the impact of severe delays to the mining schedule. The question was asked can the operation better understand the level of corrosion damage and potentially optimise rehabilitation requirements. A proposal to use a systematic approach to assess corrosion by environmental condition mapping, visual external corrosion assessment, and internal corrosion assessment via borehole camera inspections was provided and accepted by Wiluna Mining Corporation. The objective of this work was to produce a three-dimensional map showing the degree of corrosion on the reinforcement systems in the capital infrastructure, this would then be used to risk assess and prioritise rehabilitation requirements. This paper summarises the approach, methodology and results that provided the Wiluna mine planning team with information to enable planning of resources and budget to justify priorities of rehabilitation.

Nov 29, 2022

By Morrison R. D, Davis J. J, Fraser B, Kojovic T

1991 saw the completion of a three-year $1.1 million research and development program in mineral sands beneficiation, funded in two associated projects by the Australian mineral sands industry through AMIRA, and carried out by the Julius Kruttschnitt Mineral Research Centre. It is believed to be the largest R&D project in mineral sands ever conducted by a university research group. It covered dry plant operation, and delivered several products to the industrial sponsors, including: ò A detailed characterisation of the radiation properties, mineralogy and size distribution of inhaleable dust arising in dry plants. ò New process models of magnetic and electrostatic separators. ò New on-line instruments for elemental assay (in association with AMDEL) and bulk conductivity measurements of dry process streams. ò Demonstration and evaluation of the Magstream magnetohydrostatic separation technology.

Jan 1, 1992

By B Jones, M Chappell

Permanent rock bolts used to support rock tunnels are required to perform for the design life of the structure as a minimum. Quality of installation is critical to the performance over the life of the rock bolt.This paper will present the findings from an in investigation into the integrity of rock bolts installed in an underground hydroelectric power station cavern and access tunnel. The 25?mm diameter rock bolts were installed 50 years ago, tensioned and post cement grouted. Due to a major machine upgrade the whole facility was subject to an asset survey. The owners are responsible for managing the risks associated with the failure of these rock bolts and ensuring the structural integrity of the tunnels and caverns is maintained to continue operations, protect machinery, assure production and more importantly maintain a safe working environment for all employees and visitors.To help manage risk a proactive approach is desired. To this end a test schedule using a non-destructive testing (NDT) system was carried out by Independent Integrity Testing Pty Ltd (i2t). The system used in this application was RokTel™. The system operates by applying a small axial impact to the rock bolt end and measuring the resultant acceleration response. The rock bolt characteristics affect the acceleration response.The data output from the system is analysed principally using Fourier Analysis (FFT) and sinusoidal waves. The energy generated in the bar, the rate of damping and changes in frequency are all assessed. Testing was carried out on 70 rock bolts within the tunnel and cavern. A selection were then over cored, photographed and documented. The data gathered from the testing is then correlated with physical evidence to establish a calibration for the remainder of the rock bolts and assess if this is a viable method for identifying defective elements, and what degree of accuracy can be achieved. The findings will assist with the future assessment of similar hard rock underground?facilities.CITATION:Jones, B and Chappell, M, 2014. The use of non-destructive testing to identify defective rock bolts – a case study, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 275–280 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By S Maritsa, D Simbi, E K. Chiwandika, S M. Masuka

The steel industry is facing challenges on a global scale that include depletion of resources, huge energy consumption, and the emission of CO2. The demand for iron products is increasing due to the increased infrastructural development. Zimbabwe produced cast iron from scrap metals. However, there is currently a shortage of scrap, and yet Zimbabwe is rich in limonite ores that are currently being underutilised. The possibility of using limonite ore as a sustainable feed for pig iron production was investigated by preparing some limonite ore carbon composite pellets. The results showed that the addition of coal to the limonite ore and calcium carbonate mix to form the composite pellets resulted in a decrease in the drop number as well as the dry compressive strength of the composite pellets. This research aims to improve the physical properties of the green pellets by the careful addition of hydroxyethyl cellulose as a binder that was found to improve the physical properties of the green pellet. This is important for materials handling during the production process of the composite pellets. Results showed that the drop number was substantially improved by the addition of 0.4 wt per cent hydroxyethyl cellulose while the dry compression strength improved from 2.5 kg/pelIet to around 23 kg/pellet irrespective of the amount of binder added. The binder improved the physical strength of the iron-carbon composite pellets enough to allow for large-scale production of the pellets that can be an alternative and sustainable feed for cast iron production. However more results on the indurated compression strength and other properties such as the reduction degradation index, swelling index, and the reducibility test are required.

Jun 19, 2024

By A Roshal

It is anticipated that many future uranium mines in Australia will be using the in situ leaching mining process. It is fair to say that close to one third of uranium production will be generated by this method, whilst the other two thirds will fall on the uranium generated from hard rock mining and other mining methods, such as traditional open cut mining. For other types of deposits the in situ leaching mining method will remain the best technological, commercial and environmental alternative. It is important to identify and prevent all risks involved in uranium mining. The expertise in this subject is limited. Over the years there was only one mine using the in situ leaching process for uranium extraction in Australia. Computer simulation of propagation of leachate during and after the uranium in situ leaching is a crucial factor, not only for addressing the environmental concerns, but also for the most efficient recovery of the deposit. The decontamination can be modelled for a period of up to 100 years, with the acid neutralisation forecast for a period of up to 400 years. The results of the modelling are paramount for definition of the reserves, efficiency of the mining method and the environmental impact statement. The accuracy of the hydrogeological modelling and carefully selected environmental management program enables a mining company to quantify and minimise the impact of the mining activities on the regional aquifer and to prevent environmental disasters. In the study, the completed hydrogeological model allowed the client, the authorities and the community to make an informed decision about the environmental impact of the in situ leaching of uranium. In particular, the model proved that neither during the mining, nor during the neutralisation the toxic elements would interact with the local catchment area.

Jan 1, 2008