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By C K. McKenzie, P Popov, B E. Papillon, I Kharitonenko

Flyrock produced by blasts in surface mining and quarrying is a major hazard that can result in serious injuries or property damage. This paper presents a fully integrated and automated approach for reviewing blast outcomes from a wide variety of rock blasting environments from the perspective of flyrock safety associated with blasthole collar ejections. The process is applied at a corporate level for an explosives service provider handling up to 100 blasts per day from mines, quarries and construction sites throughout the US.Flyrock risk minimisation has inspired research and the associated development of a reliable flyrock model to estimate flyrock ejection velocities and the resulting maximum projection distances of fragments. In spite of significant achievements in this area, flyrock incidents continue to occur, mostly due to implementation mistakes. An efficient preventive measure is continuous blasting process improvement that relies on on-site video recording, storage, automatic analysis and classification of the recorded blasts followed by the automatic generation of reports.In this paper, a novel blasting video analysis system that is capable of processing a large quantity of video records is presented. Blast analysis and parameter measurement are fully automated and are carried out using videos recorded with a conventional consumer camera. The blast video recording process does not require the use of surface markers, range poles or objects of a predefined size for scaling purposes.Although automatic video analysis is commonly used in many application areas, such as video surveillance, traffic monitoring and robotics, the algorithms that have been developed to recognise and track solid objects with well-defined shapes, textures and colours are not efficient at dealing with blasts, which, by their nature, have dynamically changing parameters. Moreover, very strong camera vibration caused by blasts that cannot be totally compensated by camera image stabilisers may cause conventional computer vision algorithms to fail.This paper presents novel computer vision methods developed for automatic tracking of the trajectory from a blast ejection point to the highest point reached by blast particles and the ejection velocity. The system also uses colour and motion analysis to detect the emission of toxic fumes during a blast. The solution is vibration tolerant and can differentiate foreground and background data, even in the presence of camera vibration. Moreover, the blasting video analysis method can automatically categorise correctness of the measurements and therefore indicate cases when additional visual inspections may be required to verify reports generated automatically.CITATION:Kharitonenko, I, McKenzie, C K, Papillon, B E and Popov, P, 2015. An automated system for flyrock and fume monitoring of blasts, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 417–424 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

The industrial practice of separating finely' around valuable minerals from associ- ated gangue materials by froth flotation is well known. Despite the obvious importance of this industrial process, the predictive tools for plant engineering evaluation of flotation process variable changes are still in a developmental stage. Consider, for example, the situation where an operating engineer is faced with evaluating a change in an existing chemical reagent scheme, possibly based on batch laboratory data. When all is said and done, the engineer must still perform detailed physical testing of the proposed reagent change on the actual equipment in plant use to be confident even of the direc- tion of change of plant results, let alone the economic viability of the change. The theory behind chemical reagent behaviour in froth flotation has been studied extensively, e.g., (Aplan {1980}, Fuerstenau {1976}, Fuerstenau {1962}, and Somasundaran {1980}), and, certainly, important progress has been made. Unfortunately, the nature of the flotation process, with its complicated heterogeneous surface chemisty activity operating on highly variable and difficut to characterize ore surfaces, coupled with com- plex mass and momentum transfer phenomena, :;l riously compromises the plant scale predictive capability of theoretically based models.

Jan 1, 1978

By A Tawadrous, B Wheeler, D S. Preece, S A. Silling

The two key results of rock blasting are fragmentation and movement of geomaterials. Movement/flow of the blasted rock is often referred to as heave. Moving rock with explosives rather than mechanical equipment can improve mining efficiency. Such is the case with coalmine cast blasting. Controlling and directing rock movement through explosive deck delay timing can greatly improve ore recovery by segregating ore and waste. In both cases, understanding, predicting and controlling heave is an important element of successful blasting.Computer programs for predicting 2D blasting-induced heave have been used in mining for decades, helping to drive the innovation of new and more efficient mining methods, ie cast blasting. The past few years have seen the advent of 3D distinct element modelling of blast-induced heave. This is an important advancement because most blasting situations are three-dimensional in nature, especially when controlling the direction and intensity of rock movement through explosive deck delay timing.This paper documents the first full-scale blasting simulations in 3D with distinct element models that include hundreds of blastholes and in excess of a million particles, made possible with parallel processing. Surface mineral blasting is the focus of this study which treats the effect of blasthole delay timing on ore recovery. Ore waste and dilution resulting from typical row-on-row delay timing will be demonstrated. Also demonstrated will be the ore recovery possible with delay timing designs that significantly enhance ore/waste segregation. This type of high fidelity modelling and the use of electronic detonators makes possible the sculpting of rock blasting muck into separate piles of ore and waste.CITATION:Preece, D S, Tawadrous, A, Silling, S A and Wheeler, B, 2015. Modelling full-scale blast heave with three-dimensional distinct elements and parallel processing, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 127–136 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By T M. Nester, D J. Reardon, A N. Page, B J. Barsanti

The load capacity of a friction bolt has long been regarded as 4 t/m of embedment for ground support design analysis and supported by in situ pull test results. In recent years, the authors have observed lower pull test results or inconsistent results which were rarely sighted in the early 2000s. The lower pull test results indicated in some cases that reliable friction bolt capacity (≥90 per cent of results) is closer to 3 t/m of embedment with some geotechnical engineers adjusting the ground support parameters in the design work accordingly. This can be in contrast with other mines which reliably obtain 4 t/m (or greater) using the same suppliers bolt in similar ground conditions. This raised several questions: • What is the effect of poor installation (bolt twist or bolt hole deviation)? • Does the performance of friction bolts vary in different rock masses? • Does bolt performance vary between suppliers? • What effect does increased jumbo feed/percussion/rotation settings have? • Have the bolt dimensions or steel strip width changed? • Have the physical bolt properties changed? • Have the steel properties changed? This paper was aimed to answer as many of these questions as possible and discuss each variable in detail. This project included friction bolt trials at various mine sites across Australia, multiple friction bolt manufacturers, steel manufacturers and laboratory analysis. The paper also includes discussion on what the authors consider best practice for pull testing. It should be noted, the terms ‘friction stabiliser’ and ‘split set’ used in this paper are used in a generic manner and is not linked to any specific ground support supplier. Whilst its acknowledged within the industry the term split set and friction stabiliser is used interchangeably, the authors acknowledge that the term split set is a trademark of Split Set Mining Systems and has been used in context in this paper.

Nov 29, 2022

By F Musa

One of the main energy efficiency opportunities identified from the majority of mine site energy audits is to optimize the comminution circuit to reduce energy consumption through improved throughput and product size distribution. Typical analysis reviews comminution process efficiency/inefficiency i.e. utilization of grinding mills, process bottlenecks and product vs. target size, to identify instances of overgrinding or undergrinding. From this, it is possible to establish the potential improvement that could be gained through formal plant optimization and what the optimization program would entail. It can also sometimes reveal immediate opportunities for process improvement. This paper presents steps that can be taken to optimize the efficiency of comminution circuits.

Aug 8, 2011

By P Gleeson, J Coombes, P Suresh, T McLennan

The last 20 years have seen a dramatic rise in the use of 3D visualisation and modelling for geological data, but there has been relatively little effort to do the same for the variogram models that underpin the standard estimation algorithms used by the mining industry.For kriging, one of the most used geostatistical estimation methods, specifying a variogram model is a critical part of the modelling process. Experimental variography is the primary method for approximating the theoretical variogram function from the available sample data, and then determining an appropriate variogram model from the approximations.The traditional tools used for experimental variography are limited to looking at subsets of the data and are often presented without reference to geographic space and geology. It can be difficult to know what input data is being used for a particular experimental variogram, and whether there is enough support in the experimental variograms to propose an appropriate model.To overcome these limitations, an innovative approach called situational variography has been proposed that visualises variograms in 3D alongside contextual geological and geometric data. Presenting variograms in this manner aids understanding of how the spatial variance relates to the underlying data.A 3D extension of the 2D radial variogram maps will be investigated which allows for dynamic exploration of the full experimental variogram cloud. These 3D experimental variograms are much easier to visualise situationally.A workflow for situational variography will be outlined and the advantages of the situational approach will be illustrated using a porphyry copper deposit.CITATION:Gleeson, P, McLennan, T, Suresh, P and Coombes, J, 2017. Situational 3D variography – determining the variogram in the context of geology, in Proceedings Tenth International Mining Geology Conference 2017, pp 191–198 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 20, 2017

By F Flitti, M Haest, O Dominguez, D Mittrup, G Hird

The automated geology interpretation (AGI) tool has been developed in BHP Billiton to automate stratigraphy logging of drill holes, using any available quantitative data sets. At present, AGI is set-up to utilise geochemistry and mineralogy from infrared spectroscopic data to predict stratigraphy. Once the AGI tool is calibrated, results show that the tool is capable of automatically defining stratigraphy across all of the deposit types, encountered by BHP Billiton Iron Ore in the north-west of Western Australia. Accuracy of AGI at predicting stratigraphy is on average better than 75 per cent, with average accuracies exceeding 85 per cent for some deposit types. The AGI tool can deliver fast, accurate, consistent and objective geological interpretations.AGI is currently being implemented in BHP Billiton Iron Ore Exploration to streamline the drill hole logging process and allow geologists to spend less time defining stratigraphy at the drill hole level and more time investigating stratigraphy in 3D. This will deliver improved geology models, with significant downstream benefits in terms of better resource models, more accurate mine plans, higher plant efficiencies and more consistent ore products, driving productivity in BHP Billiton Iron Ore over the next decade.CITATION:Mittrup, D, Flitti, F, Hird, G, Haest, M and Dominguez, O, 2015. Semi-automated geological interpretation using assay and infrared spectroscopic sensing parameters towards improvements in geological modelling, in Proceedings Iron Ore 2015, pp 313–318 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By M Steinberg, M Amarant

Upstream Classifier are well-known in the iron ore industry for at least 15 years. At present, more than 60 units are in operation in Western Australia. The advantage of this technology is their capability to produce three products with one equipment – iron ore concentrate, iron ore middlings for further processing and slimes (tailings). The principal of this beneficiation process – upstream classification and upstream separation – will always remain. However, the optimisation of the classification and separation efficiency of the equipment itself is a continuous process driven by enhanced automation and instrumentation, design changes and the use of upstream and downstream information and requirements. Besides efficiency, the safety, maintenance and replacement conditions are very important subjects for the operation of an iron ore mine. The aim of this paper is to present a new allflux® upstream classifier design, which has been developed together with several iron ore producer from Western Australia. The new design benefits from its sustainability approach by dividing the entire equipment into small reusable parts. As a result, maintenance is minor, replacement much faster, lifetime much longer and costs much lower. Furthermore, it demonstrates new features to prevent hazardous working conditions such as confined space as well as new fixing devices to speed up the replacement of certain items and parts.

Sep 18, 2023

By K Clode, J Al-Shdifat, S Daykin

Planning for a circular economy allows for previously untapped market opportunities to be explored, resulting in new, innovative revenue generating opportunities, while also reducing environmental impacts. In particular, rare earth elements (REE) are in rising demand as they are key components of over 200 products across a wide range of applications (Xie et al, 2023) including renewable energy technologies. There is a geographical disparity in deposits, with China being the top producer, generating 70 per cent of global production in 2022 (Laboure, 2023). This single dominating source has created supply chain concentration and hence supply risks for other nations, providing a driver for finding alternative sources, such as mine-influenced water (MIW) and tailings. In this study, Isle presents a robust due diligence methodology for undertaking a global horizon scan into REE recovery technology, for a large mining company, from tailings decant water on a specific site. Previous studies of the tailings decant water at this site had shown potentially significant concentrations of both heavy and light REE, but challenges such as high flow, very low pH and high concentrations of iron had previously made recovery unfeasible. Due to these challenges, the horizon scan focused on technologies that had the potential for selective recovery, despite the challenges with water quality, and considered a range of Technology Readiness Levels (TRLs). This included an adsorption-based process that has the potential to selectively separate individual REE, and a polymer based selective flocculation technology.

Sep 1, 2024

By J Taylor, A Dubowik

To increase the efficiency and improve the quality of diamond drilling at Olympic Dam, mine geologists have adapted and modified common practices in order to overcome the challenges imposed by such a unique environment. Mine geologists have to take into account both the complex geology during the diamond drill hole design phase, as well as incorporating diamond drilling into the larger-scale scheduling process already employed at Olympic Dam. This study seeks to explore how such modifications have evolved over time.The geology of Olympic Dam influences the design process of diamond drill holes, particularly due to the variation of lithology and alteration, as well as the presence of magnetite and major structures within the orebody. Exclusion zones are used to manage interactions with existing and planned mining activities, and their size is dependent upon the geology of the area. Specific deviation checks are used to monitor the deviation of diamond drill holes with respect to these?zones.The highly interactive environment of Olympic Dam requires unique planning for diamond drilling, resulting in the production and implementation of both long- and short-term schedules. Long-term schedules are targeted at determining drilling locations and ensuring drilling is completed prior to stope planning, while short-term schedules aid in enabling access to ensure timely set-up of drill sites. Estimated drilling rates, determined by expected lithologies and historical data, feed into the short-term schedule to assist in managing the operation and minimising the downtime of diamond drill rigs. A mine geologist is appointed as a diamond drill coordinator to organise and manage diamond drilling at a scheduling and operational level, streamlining the entire process.Analysis of historical data shows a strong correlation between implementation of the aforementioned practices and improved drilling rates. This study shows the importance of adapting universal tasks to particular environments and circumstances. Mine geologists at Olympic Dam continue to acquire knowledge to further improve the modified drilling practices as operational requirements, production pressures and economic factors change.CITATION:Taylor, J and Dubowik, A, 2014. The evolution of diamond drilling practices at Olympic Dam, in Proceedings Ninth International Mining Geology Conference 2014 , pp 271–280 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 18, 2014

By P Marlow

Raiseboring is an attractive method of constructing shafts, being safe, fast and comparatively cheap. But this means back-reaming through weathered ground. However in the gravels and weathered near-surface rocks typical of the Western Australian goldfields, back reaming large diameter shafts through to the surface is risky and conventional sinking from surface has normally been required.An alternative construction approach has recently been used to stabilise the weak surficial materials and allow raiseboring through to the surface. The method is based on first installing rings of non-contiguous reinforced bored piles around the shaft perimeter, for temporary support, then back reaming shafts at full diameter through to the surface. Immediately after the reaming head is removed, the weak exposed materials are supported using remotely sprayed fibrecrete.The method has been successfully applied to four shafts since July 2007; 3 m and 4 m diameter shafts at Trident Mine, a 3 m diameter shaft at Wattle Dam and a 4.5 m diameter shaft at Athena Mine.Bored pile layout designs have varied from eight to 24 piles, of diameters 120 to 270 mm, in one or two rings. In one case, the top 10 m of the proposed shaft was pregrouted. Subsequent surveys have confirmed that fallout occurred in some shafts, out to the ring of piles, implying that the piles inhibited collapse.The practical implementation of the method was not always easy and many valuable lessons have been learnt. This paper documents key aspects of the method and the critical elements for its application.

Mar 21, 2011

By J Coombes

The JORC Code lists the three core principles of Transparency, Materiality and Competency as fundamental to how mineral estimates are publicly reported. But where the principles of Transparency and Materiality can be considered conscious choices underlying decisions at the point of disclosure, Competency is a self-declared position statement based on one’s confidence to defend a technical position (as well as the functional pre-requisites of institute membership and a minimum of five years relevant experience).Developing competency in the mining industry is an ad hoc process, generally left to the individual to chart through a process of osmosis from personal work experiences that lead to a sufficient level of confidence. Companies that actually present professional development programs leading to reporting competency are rare. And even once a person has followed a program, there is no specific outline of what constitutes technical competence.No doubt, there are persons signing off on mineral statements who would benefit from developing and/or updating their technical skills (they may not even be aware of unmastered skills). Equally, there are technical practitioners who are sufficiently competent, but lack the confidence to step up and publicly report their estimates. Confidence in one’s own abilities plays a significant role in deciding when one is ready for the responsibility of submitting mineral estimates for public consumption. In addition, a person’s organisational support, such as the availability of suitable peers and professional development programs, and opportunities to learn from a variety of technical projects contribute to developing relevant experience. Increased exposure in both technical breadth and depth enhance confidence in one’s ability and competence.The mining industry provides numerous opportunities through direct and indirect means to develop the competency underpinning a stable reporting code. This paper examines a theoretical framework and associated processes that could be used to examine how the mining industry, companies and individuals collaborate to develop this vague principle of competency. This paper seeks to initiate research with the express purpose of enabling more effective and efficient development of reporting competency in our industry.

Aug 22, 2011

By D Henderson, M Germain

The beneficiation of iron ore deposits to yield haematite and magnetite concentrates for steel making processes typically require the use of one or a combination of wet processing techniques based on gravity, magnetic or froth flotation processes. With the need for more cost-effective technologies with a lower water demand, a re-examination of dry processing techniques has been initiated. For example, a dry processing capability may offer an advantage where suitable quality and quantity of process water hinders the development of a particular resource. This paper describes recent laboratory test work for the production of high grade concentrates using dry electrostatic techniques for -300 ¦m haematite and magnetite ores and compares them with magnetic separation techniques.

Jan 1, 2009

By D Shuen, R Sales, D La Rosa

Semi-autogenous grinding (SAG) mill control is complex and depends on many dynamic process variables. Good control strategies ensure that a mill is operating as close to optimal as possible, resulting in significant economic benefits to an operation. Pueblo Viejo, a gold mine in the Dominican Republic, has been actively improving their control strategies since start-up in 2012, and one of these initiatives was to install an acoustic monitoring system on the SAG mill. The data from the system is used to optimise the mill’s performance by limiting the time the mill is either running too quiet or too loud. The lower limit is an indication that the charge in the mill is too high for efficient breakage or that the mill speed is too low and grinding media are not striking the toe of the charge. Conversely, when the acoustic emissions from the mill are too high, this can indicate that the balls are striking above the toe of the charge, resulting in inefficient grinding and excessive liner and lifter wear. Adjusting mill operating conditions to keep acoustic emissions in the ‘sweet spot’ between these limits results in more efficient grinding.Pueblo Viejo installed a Metso SmartEar™ to monitor the acoustic emissions of their SAG mill in January 2013. This system has been installed on many mills around the world and is specifically designed for optimising SAG mill control. One system output is the impact counter which measures steel-on-steel impacts on the mill shell. The impact counter uses both frequency and time domain analysis to approximate the number of ball impacts per minute. This method of analysis excludes parts of the sound signal not associated with steel-on-steel impacts and gives an accurate measure of this critical control parameter. After the acoustic system was installed, Pueblo Viejo collected data to determine the upper and lower limits for the impact count variable. The live data is available to the mill operators and it is used as one of the key operating variables to control the mill.Through continuous improvement and the use of advanced technologies like SmartEar™, Pueblo Viejo are improving the control and operation of their SAG mill, resulting in reduced liner wear, more efficient mill performance and optimised energy consumption. This paper discusses the installation of the system, and the measureable benefits obtained by using acoustic monitoring to control their SAG mill.CITATION:Shuen, D, Sales, R, Wortley, M and La Rosa, D, 2014. The benefits of using SmartEar™at Pueblo Viejo, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 297–304 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014

By J D. Illescas, S N. Arnold, D R. Shaw

Ion exchange (IX) as a primary production technique has been applied commercially since the 1950s; its application in the uranium industry continues to be widespread and is utilised to a lesser degree in the gold industry. The majority of ion exchange applications, outside of gold and uranium, have primarily been for secondary metal recovery and impurity removal. Newer developments in the application of ion exchange, as well as changes in regulatory requirements, are bringing about the wider use of ion exchange as a primary production technique not only for high value metals such as uranium, platinum group metals (PGM), refractory metals and rare earths, but also looking at base metals such as nickel and copper. The ability to build lower-cost, safer, less polluting processing plants with smaller footprints is driving a greater interest in IX, with the main competitors remaining solvent extraction and carbon-in-pulp/leach. This paper discusses a number of areas where IX has been applied and its advantages compared with other techniques.CITATION:Shaw, D R, Arnold, S N and Illescas, J D, 2012. Ion exchange in hydrometallurgy - Secondary metal removal or primary production technique?, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 17-22 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

By E Acu±a, B Prosser, R Alvarez, K Wallace

This paper describes the ventilation analyses performed for the access tunnels at the New Level Mine project (NLMP) at CodelcoÆs El Teniente operation outside of Rancagua, Chile. This new mine is anticipated to reach a final production of between 137 and 180 kt/d. Production from the NLMP is scheduled to start in the year 2017. The main access tunnels (MAT) are approximately 9 km in length, with one for personnel and supply access and the second one for ore extraction through a conveyor system. These two tunnels are a critical component of the initial stage 1 development and will be constructed independently of the existing mine workings. The tunnels were originally designed to be constructed with two tunnel boring machines. However, later analyses changed the construction approach to a conventional drill and blast technique. Because the design included two mid-tunnel ramp-to-surface connections, conventional mining methods would allow for development of the tunnels with multiple working faces to achieve a more rapid schedule. This paper presents the initial baseline considered for the ventilation design and the optimisation methodology applied by Codelco to minimise the airflow and pressure requirements of the ventilation system. Modifications to the design resulted in the addition of strategic airways and raises that could provide a saving of approximately 1 MW, when compared to the original design.CITATION:Acu±a, E, Alvarez, R, Wallace, K and Prosser, B, 2013. Ventilation considerations for the new level mine project access tunnels, in Proceedings The Australian Mine Ventilation Conference , pp 203-206 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 1, 2013

By S Mitchell

Jetcrete Australia Pty Ltd, shotcrete contractor took the initiative in 2008 to discontinue the use of ‘road registerable’ concrete trucks for all underground works in Australia and internationally.The rationale for this decision was basic, safety. Historically these vehicles have been and still are involved in far too many accidents; this obvious trend needs to be addressed by engineering out the root cause of the problem which in this case is suitability for purpose.Road registerable concrete trucks have been widely used for the delivery of concrete in Australian mines for many years prior to and after the inception of wet shotcrete as ‘in cycle’ ground support in underground excavations around 1992. With this inception came a wide interest in the shotcrete process and an influx of new shotcrete contractors, all using road registerable concrete trucks to deliver the large volumes of Shotcrete required for these services and in turn largely increasing the use of these vehicles underground. The road registerable concrete trucks were difficult to control and each trip underground required the operators to maintain good management of the inherent risks. We virtually had no reasonable alternative for the industry and could only encourage the operators to drive with soft controls such as, reducing overall speed to a maximum of 15 km per hour when declining, regardless of the road conditions, coming to a complete halt prior to turning into any sharp corners, remaining in the same gear both inclining and declining.

Mar 21, 2011

By Sorokin M, Komkov A, Fyodorov A

The Vanyukov Process is a high-intensity smelting system that has been proven over the last 20 years for various metallurgical operations including the smelting of copper, nickel, copper-zinc, antimony concentrates, municipal waste treatment and pig-iron production. Extensive pilot plant tests on copper and copper-nickel concentrates have provided information for the design of the commercial furnaces. The thermodynamic analysis, design idea and the data obtained from commercial furnaces have shown that Vanyukov Process would be the best choice to smelt copper-nickel and nickel sulphide concentrates as well as oxide nickel ores.

Jan 1, 1996

By P Craig, M Holden, C Zhang, D Foster, J Oh, S Saydam, J Liu, H L. Ramandi, S Akdag

High stress in rock masses can cause significant instability problems such as squeezing deformation in soft rock and rock bursts in hard rock. The support system applied in burst-prone areas in high-stress conditions is required to be able to carry high load and accommodate large deformation of the rock mass without experiencing any serious damage. Yielding support systems are promising to provide support for both squeezing and burst-prone rock mass encountered in mining or tunnelling at depth. They are ideally strong and stiff initially and then ductile after yielding (Potvin and Hadjigeorgiou, 2020). With respect to support design, a ground support system has to create a safe working environment under both static and dynamic loading conditions by providing the functions of reinforcing, retaining, holding and connecting elements (Cai and Kasier, 2018). Rigid rock bolts and cable bolts perform reinforcing and holding functions of a ground support system. In highly fractured ground or with large excavation spans (eg at roadway intersections or in caverns), unstable ground depth can exceed the length of typical rigid rock bolts (ie greater than ~3.0 m). In such cases, flexible cable bolts are needed to tie the reinforced and retained rock mass back to deeper and more stable rock. The flexibility of cable bolts allows anchor lengths greater than the tunnel opening that would otherwise restrict rigid bolts. Cable bolts also offer higher strength to weight ratio, with tensile strengths 2–3 times that of standard rebar bolts. This high strength comes at the cost of lower strain tolerance, typically around 5–7 per cent at break. Despite the lower strain tolerance, cable bolts are often used as dynamic support in demanding burst-prone ground conditions. The lower strain tolerance is compensated by allowing sufficient free length for stretching or incorporating a yielding device. There are a number of dynamic cable bolts available on the market and a number of testing campaigns have been undertaken to quantify the dynamic performance of these cable bolts. This paper reviews the existing range of dynamic cable bolts and discusses the potential areas for improvement and further research.

Nov 29, 2022

By L Lachance, F Flament, D Leroux, S Gariépy

The pervasiveness of poor sampling practices in and around mineral processing plants could seem intriguing in view of the various documented evidences both for causes and consequences. To this extent, this paper revisits the well-documented but lesser-known fact that failure to care sufficiently about how samples are selected and managed is the mother source of almost all sampling biases. The authors believe that the potentially huge leverage between causes and consequences as well as the diversity of people involved in sampling call for a globally integrated solution rather than for a point solution. Such a globally integrated solution has already been put forward by the AMIRA P754 Metal accounting – code of practice and guidelines (AMIRA, 2007) that inherently requires accuracy to be targeted, measured, reported and managed. Furthermore, always in order to avoid a point solution, several layers of protection against biases must be put in place with each one involving a different ownership whenever possible. This is exactly the role intended by the supervisory bias detection method described in this publication. It is based on the continuous monitoring of the expected value of reduced residuals obtained from statistical data reconciliation conducted in a metal accounting context. This supervisory bias detection method is developed in full details after which Monte Carlo simulations are done on a mineral processing plant example for showing how it can be successfully applied for detecting hidden biases.CITATION:Lachance, L, Leroux, D, Gariépy, S and Flament, F, 2014. Detecting sampling biases in metal accounting, in Proceedings Sampling 2014 , pp 109–120 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 29, 2014