Search Documents

By A. C. Johnstone

The aim of the study is to determine if pit lakes are a sustainable coal mine closure option in South African. The water balance, chemistry, limnology, and bacterial population of three selected pit lakes were investigated. The lakes are in the three major coal basins of South Africa and are associated with different lithologies and mining methods. The major factors driving the water balance of the pit lakes are direct rainfall, runoff, inflow from old mine workings, and groundwater infiltration, with the major losses being evaporation or discharge onto surface. The study indicated that pit lakes can be designed as ’terminal sinks’ to provide a sustainable mine closure option. The pit lakes sampled have an alkaline pH, and mostly a sodium/calcium sulphate water with total dissolved solids content of less than 3000 mg/l. The phytoplankton and microbiological data indicates that the pit lakes support aquatic life. The study shows that correctly designed pit lakes can be an environmentally sustainable closure option for South Africa’s coal mines. A suggested design manual has been developed to assist mine owners and regulators in developing sustainable coal mine pit lakes as a closure option.

Oct 1, 2021

By D. A. Cowen

Toll and custom treatment of base metal concentrates have been performed for decades as mines and concentrators are developed distant from capital and, energy-intensive smelting and refining facilities. Commercial treatment terms have been developed and refined for over a century, and are negotiated taking into account a complex array of quality and economic factors. Treatment of third-party concentrates in the South African platinum industry is a comparatively recent development, brought about by the opening up of mineral rights and operations being developed that are smaller than the critical size required to sustain capitalization of smelting or refining plant. Published commercial terms have not been demonstrated to reflect the complexities and subtleties of base metal concentrate markets. This paper outlines some key elements and parameter ranges of base metal concentrate treatment contracts, and applies similar principles to typical Merensky and UG2 platinum group element (PGE) concentrates to determine potential value distribution between the mining and treatment parties in tolling arrangements.

Jan 1, 2012

By J. A. Sweet, T. BACHMANN, G. E. Sandoval, T. M. Hauyon, F. A. Contreras

In many respects a porphyry copper ore concentrator plant can be considered as a simple system. Chalcopyrite typically liberates well at relatively coarse sizes, and even low grade ores are amenable to upgrading 20 to 30 times to produce concentrate grades in excess of 25 % in very simple Rougher- Regrind-Cleaner+Scavenger flotation circuits. The flotation response of chalcopyrite has been well characterised in many fundamental and applied research studies and the conditions necessary to depress pyrite and other floating gangue species are well understood. But what happens to the particle surfaces when you have a 50 km pipeline between the grinding circuit and the flotation plant? How does the seasonal variation in water quality affect your ability to control pulp chemistry? What impact does the relative concentration of the different sulphide species have on their separability? Why do two plants that receive nominally the same ore produce consistently different results? And most importantly, what do you need to do to improve the performance of both plants? To answer these and other questions, a focussed sampling and analysis programme was carried out at the Las Tórtolas flotation plants in 2018 and 2019. The work included full down-the-bank sampling, hot floats, the use of radioactive tracers for determining residence time distribution profiles, gas dispersion measurements, detailed mineralogy by size across the circuits and multiple regrind surveys. This comprehensive study was augmented by analysis of historical mineralogy, geometallurgy and operating data using modern data science techniques, and has provided the foundation for current and future optimisation initiatives. Some of the findings and their implementation will be presented in this paper. Keywords: Circuit optimization, Residence time, Gas dispersion, Pulp chemistry

Jan 1, 2020

By R. Xie, J. Liu, Y. Zhu, Y. Li

The surface chemistry features of spodumene and feldspar were investigated by XPS, zeta potential measurements and first principle calculation. The results indicated that the zeta potential of feldspar was more negative than that of spodumene. The most possible active sites on spodumene and feldspar were Al sites and O sites. However, the number, type and activity of these sites were different. The flotation behaviour of five new collectors (cationic collector decyloxy-propyl-amine (DPA), anionic collector α-bromododecanoic acid (α-BDDA), N-Dodecyliminodiacetic acid (DIDA), and mixed collector DPA-BDDA and DPA-DIDA) were investigated through micro flotation experiments and analysed based on the surface chemistry features of spodumene and feldspar. The results revealed that cationic collector DPA processed a high collecting capacity for both minerals. The highest recovery of spodumene and feldspar was 91.60% and 95.30% respectively. The anionic collector α-BDDA and DIDA showed poor flotation behaviour. The recovery of spodumene and feldspar when using α-BDDA as collector was less than 5% and when using DIDA as collector was less than 1%. For the mixed collector DPA-BDDA, the recovery of spodumene and feldspar was 82.27% and 32.61% respectively at pH 4.5. For mixed collector DPA-DIDA, the recovery of spodumene and feldspar was 35.69% and 9.08% respectively at pH 5.8. The results indicated that the cationic collector had high collecting capacity, but low selectivity. The collecting capacity of anionic collector for spodumene and feldspar was poor at the same concentration compared with cationic collectors. Mixed collector DPA-BDDA showed good flotation behaviour and selectivity on spodumene. The ―COO- in mixed collector might improve the selectivity. However, too much ―COO- would increase the electrostatic repulsion, which might cause low selectively and poor recovery. Keywords: Spodumene, feldspar, surface chemistry features, mixed collector, flotation

Jan 1, 2020

By van der Merwem J. N.

"Coal pillars are prone to scaling over time, and are progressively reduced in size and consequently subjected to increased load and reduced strength. The effective factor of safety therefore reduces. Databases of failed and stable pillars cannot, therefore, be regarded as definitive.More than a decade has passed since the first attempt to predict the lifespan of pillars. This paper presents a review based on the new database and pillar strength equations. The methodology for the analysis is based on the fact that pillars scale. The ultimate safety factor (defined as the ratio between strength and load at the time of failure) is derived, followed by an estimate of the rate of pillar scaling, which results in an estimate of the expected time of failure.It is suggested that the predicted lifespan should not be used as an absolute indicator of expected pillar life, but rather as an index – the pillar life index (PLI) – to complement the safety factor and related probability of failure when evaluating pillar stability. A pillar with a predicted lifespan of less than 500 years would be regarded as being in danger of imminent collapse, while a lifespan of at least 1 000 years should be required for long-term purposes.The differences between this analysis and that published in 2003 constitute a strong case for regular reviews of all the empirically based stability indicators, namely the safety factor, probability of failure, and the PLI. Reviews at 10 year intervals appear to be required.The constants in the proposed method are valid only for the Witbank No. 1, 2 and 4 seams and the Highveld No. 2 and 4 seams.IntroductionIt is well known that over time, coal pillars are prone to scaling, and thus are progressively reduced in size and consequently subjected to increased load and reduced strength. The effective factor of safety therefore reduces and it is quite possible for failure to occur after a long time interval. In fact, scrutiny of the database of failed pillars indicates that failure occurred after periods ranging from 2 to 49 years, and not immediately after mining.The factor of safety for pillars at the time of failure is not the same as that immediately after mining. The concept of the safety factor is based on the pillar strength obtained by statistical analysis of pillar dimensions immediately, or within a month after mining, when the surveys are conducted. Strictly speaking, the safety factor as commonly used is valid only immediately after mining, and it continues to reduce thereafter. The ideal situation would be to base analyses of pillar strength on pillar dimensions at the time of failure, but that is simply not possible because the real dimensions cannot be measured at that time."

Jan 1, 2016

By B. P. Watson, D. P. Roberts, R. A. Lamos

The Upper Group 2 (UG2) chromitite reef is a shallow-dipping stratiform tabular orebody in the South African Bushveld Complex, which strikes for hundreds of kilometres. Mining is extensive, with depths ranging from close-to-surface to 2 500 m. Pillars are widely used to support the open stopes and bords. Little work has been done in the past to determine the strength of pillars on the UG2 Reef and design was done using formulae developed for other hard-rock mines. This has led to oversized pillars with consequent sterilization of ore. In this paper we describe a back-analysis of stable and failed UG2 pillars on the Bushveld platinum mines, and provides a strength formula for UG2 pillars. The formula may be used cautiously on all Bushveld platinum mines with similar geotechnical, geometrical, and geomechanical conditions to the pillars in the database.

Aug 1, 2021

On behalf of the Council and staff of The South African Institute of Mining and Metallurgy, it is my privilege to wish all members and subscribers a very Happy Christmas and a Prosperous New Year.

Jan 1, 1988

By M. Wrobel, J. Hammerschmidt, M. Runkel

Fluid-bed technology is a key pyrometallurgical step for processing a vast number of ores and concentrates. Over the past 50 years, considerable research and development efforts have been made by Metso Outotec to expand the application window of this technology. This paper illustrates different processing routes where fluid-bed technology plays an important role in the production of the copper. The fluid-bed processes utilized are partial, sulfate-producing, and dead roasting. The focus of this paper considers the advantages of the dead-roasting process. This “zero waste” process can provide copper oxides, steam, electrical power, and sulfuric acid for new and existing solvent extraction–electrowinning plants. In a case where an operation is running out of oxidic ores and concentrates, fluid-bed roasting can be applied to close this gap and provide the required copper oxides in a sustainable way.

Jan 1, 2023

By H. Han, Z. Gao, Y. Gao, W. Sun, J. Wang

Strategic Ca-bearing minerals like scheelite and fluorite are usually separated by flotation, yet the separation is quite difficult due to their similar surface Ca active sites. Compared with the conventional strong collector sodium oleate (NaOL), lead nitrate-benzohydroxamic acid (Pb-BHA), complex collector shows a better selectivity for scheelite, yet its high cost hinders its wide application. Therefore, a novel collector (Pb-BHA-NaOL complex) was initially developed in this work to overcome the abovementioned dilemma. The flotation results of a single mineral showed that Pb-BHA-NaOL had a better selectivity for scheelite than Pb-BHA. Under the conditions of sequential assembly of Pb, BHA and NaOL at the molar ratio of 240:120:1 and pH 9.0, selective separation of scheelite from fluorite could be achieved without adding any depressants. In addition, for the same preferred scheelite recovery, Pb- BHA-NaOL could also save approximately 20% Pb and BHA compared with Pb-BHA. The analyses of the zeta potential measurement and X-ray photoelectron spectroscopy indicated that Pb-BHA-NaOL showed stronger adsorption on scheelite relative to fluorite. Meanwhile, Pb-BHA-NaOL showed more adsorption modes and higher utilisation of Pb and BHA on scheelite than Pb-BHA, which was due to the accelerator, NaOL. Keywords: Scheelite, fluorite, lead nitrate, benzohydroxamic acid, sodium oleate, flotation

Jan 1, 2020

By D. N. Golenkov, N. I. Lomaka, A. V. Kozub, T. V. Ignatova, E. V. Shelepov, D. O. Sharkovskiy, A. V. Chanturiya, R. I. Ismagilov

The modern Russian iron ore mining industry is faced with multiple challenges from everincreasing requirements of steel-making, the value of iron ore concentrates, depletion of high-grade ore reserves and complications of the mining and geologic environment’s necessity to process low-grade ores with complex material composition and low valuable mineral content; with finely disseminated aggregates of metal and non-metal minerals responding similarly to processing. The upgrade of the existing operations’ fine wet screening was implemented by Metalloinvest; as well as the design of a process flowsheet for concentration oxide ferruginous quartzites with low concentrating ability. The scientific basis for improvement of low grade ore concentrating efficiency and the upgrade of market product quality is supported by an in-depth study of ore characteristics, application of high performance equipment for separation of fine-grained mineral aggregates and use of depressor selective to ferruginous minerals in the flotation process. The benefits of wet fine screening have been proven by industrial scale tests; as well as the feasibility of significant upgrades in product quality which have been confirmed as a result of the tests. A road-map for the upgrade of an existing process for the concentration of unoxidised ferruginous quartzites deposited in the Mikhailovskoye ore field was developed, based on the industrial scale test of a fine screening process. With reference to the ability for concentration, three major ore types oxidised ferruginous quartzites were defined as a result of comprehensive geological mapping and process sampling: oxidised ferruginous quartzites with good concentrating ability: over Fe67% grade of concentrate with ca. 80% iron recovery; oxidised ferruginous quartzites with moderate concentrating ability: Fe65-67% grade of concentrate with 70-72% iron recovery oxidised ferruginous quartzites with low concentrating ability: below Fe60% grade of concentrate (cannot be processed into desired grade market product). A process flow diagram combining magnetic separation and flotation has been designed and recommended for implementation based on the in-depth research of defined Mikhailovskoye deposit iron oxide types, including grain size, chemistry, petrographic, mineralogy, hematite and magnetite grain size distribution and liberation analysis.

Jan 1, 2020

By R. B. Khumalo, T. Chauke, T. Mtshali, F. K. Mulenga, B. Makgate, N. M. Chiloane, T. Moyane, V. C. Madanda

While high production rates are important for the profitability of a mine, the influence of geotechnical engineering cannot be ignored. In block caving, a high-stress level is required for cave propagation; this is one of the core elements for ore recovery. Therefore, stress distribution and geological structures play a major role in the planning and layout design of the mine. This paper explores the influence of stress and geological features on the design of the mine from the feasibility study phase. The geology and stress measurement of the mine were determined through logging and overcoring, respectively. This study found that while production rate is the primary operational consideration, the long-term layout design of the undercut face advance, face angle, drawpoint spacing, and undercutting sequence is mainly governed by the stress orientation and major geological structures. Moreover, widely spaced drawpoints result in isolated draw zones, consequently, resulting in ore loss and early dilution whereas closely spaced drawpoints affect the stability of the major apex pillar. This paper also provides insight into how operations can leverage stress distribution to optimise mine layout and safety in massive mining methods.

Nov 24, 2025

By F. Navarro, F. Soto, G. Díaz, E. Jélvez, G. Morales, N. Morales

The increasing availability of tools on the web provides a great opportunity for the research community to boost investigation by accessing computational resources from all over the world. For example, data analytics libraries implemented in languages like Python can be accessed through many open and commercial platforms, therefore providing researchers with a common set of tools or shared datasets. Unfortunately, that is not the case with research in resource assessment and mine planning, where the most standardised tools are commercial applications designed to work on the desktop, but there are not many standard platforms for research. As a result, researchers from different groups often need to start from scratch in order to develop their work, and rarely share implementations details. Similarly, apart from a few publicly available examples, there is a lack of common datasets that are validated and can be used to compare results between different approaches. In this paper, we introduce a platform that provides tools for resource assessment and mine planning, which can be accessed remotely utilising Jupyter Notebooks. In its current version, the platform provides (i) definition and implementation of basic structures for managing samples and models (loading, saving, adding or removing columns, etc.), (ii) definition of experimental and modelled variograms for spatial continuity analysis, (iii) definition of standard interpolation methods in resource evaluation (inverse distance and kriging), (iv) definition of standard problems in mine planning (ultimate pit and precedence constrained production scheduling), (v) generation of 2D standard graphs like grade distribution, conditional means, tonnage-grade, and production plans (vi) a set of datasets, which can be used for case studies, and (vii) a set of notebooks with examples and documentation. In this paper, we introduce the platform and show some examples that illustrate some of the possibilities that it has for research and education in the area of resource assessment and mine planning.

Sep 1, 2021

By S. J. Thomas, P. A. Lilly

With support from the Australian mining industry and the Federal Government, three Australian universities are collaboratively developing flexible-format, web-based course content and delivery in rock mechanics for undergraduate mining engineering students. This paper describes the educational philosophy behind the development and summarises other salient features of the Program. Mit der Unterstuetzung von der austlalischer Bergbauindustrie und der Bundesregierung, drei austlalische Universtaeten in Zusammenarbeit entwickeln flexibel Netzgengruendet auf Lehrganginhalt und Lieferung in Felsgestein fuer Bergbaustudenten. Dieses Schreiben erlautert das Unterrichtsphilosophie hinter der Entwicklung und Zusammenfassung anderer Hauptpunkte von diesem Programm" Avec l'assistance de l'industrie miniere australienne et du gouvernement federal , 3 universites Australiennes collaborent a la mise en place d'un programme de mecanique des sols pour etudiants- ingenieurs en mines. Ce programme serait a la fois flexible et accessible par Internet. Ce document decrit la philosophie pedagogique de ce projet et en souligne les characteres importants.

Jan 1, 2003

By A. Haque

The shear behaviour of infilled joints produced from ordinary gypsum plaster (gyprock) and bentonite was investigated in the laboratory under Constant Normal Stiffness (CNS) conditions. Shear tests were performed on saw-tooth profiles having Joint Roughness Coefficients (JRC) of 4.75 and 9.25 under an initial normal stress (sno) of 0.30 to 1.10 MPa, and at a normal stiffness (kn) of 8.5 kN/mm. Test data under the same sno and infill thickness to asperity height ratio (t/a) were analysed for two different sets of JRC. The peak shear stress plotted against the t/a ratio under constant sno revealed an increase in peak shear stress with the increase in JRC, up to a t/a ratio of about unity. The effect of roughness on the peak shear stress was observed to be minimal when the t/a ratio exceeded 1.40. A mathematical model for the prediction of peak shear stress due to the increased infill thickness has been developed based on a hyperbolic stress-strain relationship and energy balance principles. The model predictions are in good agreement with the laboratory observations. Le comportement de cisaillement des joints remplis produits à partir de plâtre ordinaire et de bentonite a été étudié dans le laboratoire sous des conditions de rigidité normales constantes. Des essais de cisaillement ont été réalisés sur des profils en dents de scie ayant des coefficients de rugosité des joints (CRJ) variant de 4,75 à 9,25 sous un effort normal initial (sno) de 0,30 à 1,10 MPa, et une rigidité normale (kn) de 8,5 kN/mm. Le résultat des essais conduits sous la même contrainte et épaisseur de remplissage au rapport aspérité/hauteur (t/a) ont été analysés pour deux ensembles différents de CRJ. La variation de l'effort de cisaillement maximal contre le rapport t/a sous une contrainte normale constante a indiqué une augmentation de l'effort de cisaillement maximal avec l'augmentation du CRJ, jusqu'à un rapport de t/a proche de l'unité. L'effet de la rugosité sur l'effort de cisaillement maximal a été minimal quand le rapport t/a a excédé 1,40. Un modèle mathématique pour la prévision de l'effort de cisaillement maximal dû à l'épaisseur accrue du remplissage des joints a été développé sur la base de la variation entre contraintes hyperboliques et déformation et sur des principes de bilan énergétique. Les prévisions du modèle sont en bon accord avec les observations de laboratoire. Das Scherverhalten in mit gewöhnlichem Gips und Bentonit gefüllten Klüften wurde im Labor unter Bedingungen konstanter Normalsteifheit (CNS) untersucht. Scherversuche wurden durchgefürt für Sägezahnprofile mit Werten des Fugenrauhigkeitskoeffizienten (JRC) von 4.75 und 9.25 unter Normalspannungs-werten (sno) von 0.30 bis 1.10 MPa, und bei Normalsteifheit (kn) von 8.5 kN/mm. Testresultate für gleiche Werte von sno und Verhältnis Fülldicke zu Rauhigkeit (t/a) wurden untersucht für zwei verschiedene Werte von JRC. Die Beziehung zwischen maximaler Schubspannung und und t/a Verhältnis unter konstantem sno zeigte einen Anstieg der maximalen Schubspannung mit zunehmendem JRC, bis zu einem t/a Verhältnis von etwa 1.0. Der Einfluss der Rauhigkeit auf den Maximalwert der Schubspannung war minimal solange das t/a Verhältnis den Wert von 1.40 überstieg. Ein mathematisches Modell wurde entwickelt für die Vorhersage der Schubspannung die von zusätzlicher Fülldicke erwartet werden kann, ausgehend von einer hyperbolischen Spannungs-Dehnung Beziehung und dem Energiegleichgewichts-prinzip. Die Modellvorhersagen zeigten gute Uebereinstimmung mit den Laborbeobachtungen.

Jan 1, 2003

By F. W. Petersen

The Conference Minerals & Materials '96 was held in Somerset West, South Africa, from 31st July to 2nd August, 1996. It was organized by the Universities of Stellenbosch and Cape Town, the Cape Technikon, and the Western Cape Branch of The South African institute of Mining and Metallurgy (SAIMM). The three-day Conference was attended by 180 delegates, representing countries such as Australia, South Africa, United Kingdom, Finland, Sweden, Germany, Poland, Zambia, and Zimbabwe. The programme and associated exhibition were well organized, and each of the delegates received two volumes of proceedings containing the 77 papers presented at the Conference.

Jan 1, 1996

By G. M. J. van Heerden, R. C. W. Webber-Youngman

"This article describes the re-engineering principles applied in the design of a personnel transportation system for the Bafokeng Rasimone Platinum Mine in the Rustenburg area of South Africa. It incorporates conveyor belt travelling, chairlift operation, and also includes consideration of proposed changes/modifications to the existing conveyor belt infrastructure.The purpose of the project was to identify, through a process of evaluation, the appropriate option and/or combination of transportation options that would be safe in terms of personnel transportation as well as cost-effective. Alternative measures for transporting personnel (not using belt riding) would have a significant positive spin-off, increasing the availability of the belt and thereby increasing production. This paper explores the feasibility of interventions that would improve safety through eliminating risk associated with personnel transportation as well as contributing towards improving the mine’s position on the cost curve.The design in consideration at the Bafokeng Rasimone Platinum Mine consists of two shaft systems, namely the North Shaft and South Shaft, each comprising twin decline shafts. One of the decline shafts is equipped with a conveyor belt for rock and personnel transportation, and the other with a winder for trackbound material transport. The conveyor belt has been used for personnel transportation since the commissioning of the shafts. The conveyor belt is equipped with platforms for personnel getting off and on the belt and a number of safety devices designed to ensure safety while travelling on the belt. Intensive training in the practical aspects of belt riding is given to every person, and unsupervised riding on the belt is permitted only once belt riding competence is demonstrated. Despite this, the safety results were poor, with 106 injuries between 2006 and May 2013. Fortunately, no fatalities were reported during this period.An investigation of alternative means for personnel transportation or engineered solutions to the current conveyor belt infrastructure in the safest, most effective, and most economical way was therefore needed. There was a major risk of safety-related stoppages being imposed following another belt accident/incident. This would prevent the mine from transporting personnel underground by belt and result in major production losses. From the commissioning of the Phase 2 shaft deepening project on both shafts, dedicated chairlifts have been used for personnel transportation as opposed to the conveyor belt installed in the Phase 1 area. The chairlifts have been in operation since 2004 and no chairlift-related incidents have been recorded thus far. According to safety statistics, it is clear that the chairlift is the safer method for the transportation of people in the shaft.To fulfil the objectives/scope of this study, it was recommended that both primary (new chairlift decline with infrastructure) and secondary options (modifications to the current conveyor belt infrastructure) be considered for implementation on both the North Shaft and South Shaft to reduce or eliminate accidents/incidents as a result of belt transportation. The associated capital expenditure would be approximately R200 million. Considering the future impact on the business as a whole, this would definitely be capital well spent."

Jan 1, 2016

By A. Tosun

"The size distribution of the muckpile formed as a result of open pit blasting operations has a considerable effect on the efficiency of loading, hauling, and crushing. Various researchers have developed specialized computer software that uses image analysis methods for determining the size distribution of the muckpile. However, these methods have some limitations. One of the most important of these limitations is that the very fine fragments in the muckpile cannot be used in the size distribution calculation. In this study, 18 test blasts in total were carried out in two limestone quarries belonging to Batiçim Corp. in Izmir, Turkey. A new model was developed in order to ensure that very fine fragments are used in the size distribution calculation. The size distributions of the test blasts were calculated by both the Wipfrag computer program and the new model. Correlations were established between the muckpile size distributions determined by both methods and the parameters determining the efficiency of the loader. IntroductionThe size distribution of the muckpile formed as a result of open pit blasting operations has a considerable effect on the efficiency of loading, hauling, and crushing. Various researchers have established certain correlations for predicting the efficiency of the operations according to the muckpile size distribution so that production can be carried out economically (Tunstall and Bearman, 1997; Nielsen and Kristiansen, 1996; Workman and Eloranta, 2004; Michaud and Blanchet, 1996; Frimpong, Kabongo, and Davies, 1996; Osanloo and Hekmat, 2005; Molotilov et al., 2010). In these studies, the 50% passing size (X50) is generally used. These methods rely on the correct measurement of the size distribution of the muckpile formed by the blast. The most reliable measurement method would be to subject the entire muckpile to a sieve analysis, but this is obviously impracticable. Therefore, computational method based on image analysis have been developed. These include IPACS (Dahlhielm, 1996), Tucips (Havermann and Vogt, 1996), Fragscan (Schleifer and Tessier, 1996), Cias (Downs and Kettunen, 1996), GoldSize (Kleine annd Cameron, 1996), Wipfrag (Maerz, Palangio, and Franklin, 1996), Split Desktop (Kemeny, 1994), PowerSieve (Chung and Noy, 1996), and Fragalyst (Raina et al., 2002). In these methods, the size limits of the fragments forming the material are determined by image analysis on photographs of the muckpile. However, the computer software has some limitations. It does not take into account the third dimension of the muckpile, nor the size distribution of very fine fragments. In particular, the fragment size ranges below 2.5 to 3 cm cannot be determined, and therefore these cannot be included in the muckpile size distribution. However, the muckpile formed by a bench blast contains a wide range of particle sizes (Tosun et al., 2015)."

Oct 1, 2018

By K. Woodward, Y. Potvin, B. McFadyen, M. Grenon

Open stoping has become a popular mining method in hard rock mines, not only due to the safety of the method as a non-entry approach, but also because of the high extraction rate and low costs. At mine sites, stope performance is evaluated by calculating stope overbreak using the stability chart. However, limitations of the stability chart regarding the precision of the predictions, nonconsideration of factors such as the influence of blasting, and the exclusion of underbreak have led to non-optimal designs. The capabilities of today's computers have increased the amount of data being collected and the power of models being built. This article presents a step towards a new stope design approach where stope overbreak and underbreak are measured and georeferenced using octrees at an approximately cubic metre resolution and predicted using multivariate statistical models (partial least square, linear discriminant analysis, and random forest). Results show that overbreak and underbreak location along the design surface and their magnitude are predicted with good precision using a random forest model. These predictions are used to build the expected geometry of the open stope. The resolution of the data and the use of multivariate analysis has enabled the prediction of variation in stope performance along the design surface, going well beyond the simple qualitative per stope face prediction provided by a traditional stability chart approach.

Jun 5, 2023

By A. Doroudgar, H. Noferesti

Unstable rock failure or rock bursting is one of the most dangerous problems in deep hard rock mines. This type of failure, that occurs uncontrollably, is associated with a significant release of strain energy from the surrounding rock. In this study, the numerical simulation of unstable rock failure was carried out using the three-dimensional explicit Lagranian finite-volume finite difference method to identify the onset and location of unstable failure events in the model. On this basis, a numerical simulation of mine pillars with width-to-height ratios of 0.5, 2 and 3 was performed. A criterion was developed, based on the calculation of the elastic strain energy, to determine the prone areas for the initiation of rockburst in the models. The results of this study showed that, in softer loading systems, due to large amounts of stored elastic strain energy, an unstable equilibrium is established, which leads to the rapid transfer of strain energy to the rock in the form of violent failure. It was also found that the unstable failure starts at the corners and free surface of the model. The new criterion developed in this study may help predict the occurrence of rockbursts in slender pillars and the design of pillars to control human and financial losses caused by this phenomenon.

Nov 27, 2024

By Paul B. Crawford, Gerald N. Pitts

"A new method is introduced for the simulation by computer of the flow of liquid underground. The method has application in simulating, for example, liquid withdrawal systems, injection systems or injection-well systems. The computer simulation of liquid flow permits the utilization of the known properties of the rock in developing a model of the permeable rock mass.The flow properties of the rock at a specific site arc generated statistically using a random number generator. After defining in this manner the rock properties of each element in the computer grid, the streamlines or flow paths of the liquid are traced using the new method. The simulation is designed especially for computers. The meandering character of the liquids paths is displayed clearly as the fluid moves underground, thus providing the technical information required for the control of the movement of liquid."

Jan 1, 2014