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By Jean Michel Marino, Jean-Pierre Slama

"The computer methods used by the French Commissariat a l'Energie Atomique, which are applicable to any type of ore deposits, are:(i) Ore reserve estimation. The data are either the core analyses or gamma leggings. To determine the spatial distribution of the ore, three different methods of interpolation are used. Two of these are based on the least-squares theory and the third one is an application of the regionalized variable theory. The interpretations of the orebody by the geologists are introduced in the computer program as often as possible.(ii) Optimal open pit design. From the spatial distribution of ore, the three-dimensional outlines of the optimal pit are determined by a geometrical algorithm which allows different slopes varying with the azimuth.Finally, the optimization of annual successive plans arc discussed."

Jan 1, 2014

By J. L. Human, N. Fernandes

The rockfall hazard is the major contributing agency to fatal accidents in South African platinum mining operations. The majority of these accidents occur in close proximity to the working stope face. The collapse of fractured or blocky ground between individual temporary support units or the closest permanent support line to the stope face has not yet been adequately addressed. A large-scale stope support system testing facility funded by the Safety in Mines Research Advisory Committee (SIMRAC), has been designed and constructed to test support systems and stimulate innovative thinking by mining personnel, support manufacturers and suppliers by providing a facility where the interaction of stope support systems, a rigid stope face and a discontinuous hangingwall beam can be observed during quasi-static and dynamic conditions. Tests have been carried out on various types of stope support systems, focusing on the temporary support systems used in the immediate stope face area. The interlinking of the temporary support units with mesh or safety netting has been explored in the prevention of falls of ground between support units during gravity driven falls of ground. These tests illustrate the facility?s ability to be used to stimulate innovative thinking and provide a testing ground for the development of temporary support systems in order to reduce the risk off all of ground injury to mining personnel at the stope face.

Jan 1, 2004

By H. W. Glen

The use of a personal style (mainly active voice and first person) makes technical writing more pleasant to read, and helps the writer to express his meaning clearly and to avoid many of the stylistic errors normally encountered in that type of writing.

Jan 1, 1979

By K. Dagdelen , S. K. A. Owusu

Uncertainty with regard to estimated grades and tonnages of a mineral deposit demands risk assessment in order to build investor confidence and attract the interest of other stakeholders in the success of a project. Uncertainties associated with Mineral Resource estimates can lead to unreliable production schedules and unpredictable cash flows. However, the techniques used in the mining industry to determine these uncertainties are inconsistent, because the important decisions taken in the process are solely dependent on the responsible Competent Person (CP), without limitations. This leads to disparities between different CPs’ results, using data-sets from the same drill-holes. The various standard codes for public disclosure provide guidelines and recommendations for the classification of Mineral Resources and Reserves but do not provide details on, for example, the amount of geological and geostatistical information needed to qualify for each category of Resources and Reserves. The parameters used to generate the classification categories are subjectively assumed by the responsible CP. In this paper we investigate the impacts of different CPs’ judgements on resource classification, using the same data-sets. The results underpin the need for the mining industry to develop a uniform Mineral Resources and Reserves classification framework that can minimize or avoid significant discrepancies that lead to potential misleading public disclosures.

Aug 8, 2024

By W. P. Nel

The introduction of the Higher Education Qualifications Framework (HEQF) and the updated Higher Education Qualifications Sub-Framework (HEQSF) has caused many South African university departments to rethink their programme qualification mixes (PQMs). In addition to the requirements stated in the HEQSF, a number of other factors have to be taken into consideration by a university department. These factors include, for example, the standards generated by the Engineering Standards Generating Body (ESGB) and subsequently approved by the Engineering Council of SA (ECSA) and the need to prepare students for various categories of professional registration with ECSA. This means that a university department has to choose the correct mix of Learning Programmes (LPs) from the HEQSF menu (which consists of 13 types of LPs). Preparing students for ECSA registration is aligned with the mission of universities, which is to teach and undertake research. However, research and the LPs associated with research go beyond the requirements for current ECSA registration. Assuming that universities offering engineering LPs would elect to prepare students for both ECSA registration and teach them to produce research outputs, which is mostly done at Master and Doctorate levels (NQF Levels 9 and 10), then it follows that academics are more interested in NQF Level 5 to 10 pathways (abbreviated as ?L5-10?) rather than the shorter pathways required towards professional registration. (For example, ECSA requires an NQF L5-L7 pathway for registration as a candidate professional technologist. This specific pathway may consist, for example, of two LPs, namely the 360-credit Diploma and the Advanced Diploma.) A L5-L10 pathway is a combination of LPs that will prepare the learner with a NSC (or equivalent qualification at level 4) to Doctoral level (level 10). Universities may choose at least four major pathways from the HEQSF menu in order to educate and develop students from NQF Level 5 to 10. However, various pathways towards registration in the category of candidate with ECSA are also embedded into these four NQF L5-L10 pathways, where each consist of a unique combination of LPs. Each of these pathways has an opportunity cost, and economic reality means that smaller departments may have to choose between the four pathways. Of all the many factors involved in PQM decision-making, the focus of this paper is on the HEQSF requirements, ECSA standards, and ECSA registration and how these, together with the various qualifications and educational LPs provided for by the HEQSF may impact on the PQM decision taken by engineering departments and schools at South African universities. The proposed four NQF L5-L10 ?pathway tool? for PQM decision-making may be useful for pointing out the advantages, disadvantages, and applications of the various pathways and combinations of pathways. Rather than deciding from a menu of thirteen qualifications and associated LPs, this article proposes that decision-making be undertaken on the basis of a menu of four main articulated ?NQF L5-L10? pathways (which also include one or more of the ECSA?s pathways for professional registration). The proposed ?NQF L5-L10 pathway? tool is an attempt to move one step closer to the aim of achieving a structured decision-making approach for designing a PQM at departmental level.

Jan 1, 2014

By K. Aoki, Y. Mito, S. Shirasagi

The authors developed the TBM Excavation Control System (the TBM Navigator), in order to realize the advanced observational construction. During the excavation using this system, the rock strength value is immediately calculated from the TBM driving data as an index of rock properties, and the drill energy coefficient is also calculated from the drill logging data that is carried out using the probe hole ahead of the tunnel face. In this study, a new, geostatistical simulation-based method is proposed for the automatic prediction of the rock properties ahead of the tunnel face with good precision, using both the drill logging data and the TBM driving data. The applicability of this method is validated through the prediction at the actual tunnel excavation that passes through the faults. Les auteurs ont mis au point un Système de Contrôle de forage avec la machine à pleine section (Navigateur de la machine à pleine section), en vue de réaliser un système de surveillance plus efficace. Avec ce système, la résistance de la roche est immédiatement calculée, au cours du forage, à partir des données de conduite de la machine, comme indice des propriétés de la roche, et le coefficient d'énergie de la foreuse est également calculé à partir des données de log de forage collectées dans un trou de sonde foré dans le front de taille. Dans cette étude, on propose une nouvelle méthode basée sur la simulation géostatistique qui permet de prévoir d’une manière automatique, des propriétés de roches se trouvant derrière le front de taille avec une précision satisfaisante, à l’aide des données de log de forage et celles de conduite de la machine à pleine section. Cette méthode s’est avérée suffisamment précise au cours du forage d’un tunnel réel qui traversait une zone de failles. Die Autoren entwickelten das TBM Ausschachtungssteuerungssystem (den TBM Navigator), um noch besser überwachte Bauarbeiten zu ermöglichen. Unter Einsatz dieses Systems wird die Gesteinsfestigkeit während der Ausschachtungsarbeiten unmittelbar aus den TBM Antriebsdaten als ein Index für die Gesteinseigenschaften berechnet. Gleichzeitig wird auch der Bohrenergiekoeffizient aus den Bohrlogdaten berechnet, die an Hand der Probebohrung am Stirnende des Tunnels erhalten wurden. In der vorliegenden Studie wurde ein neuartiges, auf geostatistischen Methoden basierendes Verfahren für die automatische und angemessen genaue Vorhersage der Gesteinseigenschaften am Stirnende des Tunnels vorgeschlagen, für das sowohl die Bohrlogdaten als auch die TBM Antriebsdaten verwendet werden. Die Anwendbarkeit dieser Methode wird durch die Vorhersage bei einer tatsächlichen, durch Verwerfungen verlaufenden Tunnelausschachtung bewiesen.

Jan 1, 2003

By M .. Hori, H. Onishi, Y. Goda

The split-lining structure was newly developed for the air-tight lining of the underground compressed air storage cavern. This structure consists of separated reinforced concrete (RC) segments and air-tight membrane. It is most important for the Compressed Air Energy Storage Gas Turbine (CAES-G/T) system to develop the economical lining. In order to verify the applicability of split-lining structure, CAES-G/T pilot plant was constructed and operated for 6 months. We confirmed the practical usefulness and safety of this system through the operation. This paper presents the mechanical behaviour of surrounding rock mass and the lining structure observed through the operation of CAES-G/T pilot plant. Nous avons mis au point une structure de revêtement modulaire pour le revêtement des cavernes souterraines hermétiques à pression. Ce revêtement est composé de segments de béton armé et de membranes hermétiques. Il était très important, pour le CAES-G/T (Compressed Air Energy Storage Gas Turbine), de développer un revêtement économique. Afin de vérifier l’aptitude d’application de notre revêtement modulaire, nous avons construit un système pilote CAES-G/T et nous avons effectué des essais de fonctionnement pendant six mois. Ces essais nous ont permis de confirmer l’utilité et la sécurité du système. A travers le présent rapport, nous rendons compte de la structure de ce nouveau type de revêtement et du comportement mécanique de la masse rocheuse environnante que nous avons pu observer au cours desdits essais. Als luftdichter Druckbehälter wurde eine gegliederte Belagsstruktur für tief unterirdisch liegende Felshöhlungen entwickelt. Diese Struktur ist aus Stahlbetonabdeckung und luftdichter Plane aufgebaut. Bei der Entwicklung des Pressluftgasturbinen – Stromerzeugungssystems (CAES-G/T) war es die wichtigste Aufgabe, einen wirtschaftlichen Belag zu entwickeln. Deswegen wurde zum Nachweis der Effektivität der gegliederten Belagsstruktur eine Pilotanlage errichtet und 6 Monate lang betrieben. Durch den Betrieb konnten wir die Praktikabilität und Sicherheit des Systems bestätigen. Dieser Aufsatz ist ein Bericht über das Verhalten der durch Betrieb der CAES-G/T Pilotanlage beobachteten Belagsstruktur und umliegenden Felsmasse.

Jan 1, 2003

By F. H. Cornet, D. Ask, O. Stephansson

We have conducted a stress analysis of overcoring stress measurements undertaken at the Zedex Test Site (ZTS) in the Äspö HRL, Sweden. Two different types of overcoring cells have been used at the site: the 9-gauge Borre Probe (CSIR-type) and the 12-gauge CSIRO HI cell. Inversion programs based on the least-squares criterion were developed and calibrated. The primary and secondary stress field in the ZTS were back-calculated using strain data from individual cells as well as from combining data from both cells. We propose that the combination of strain data from the two cells significantly improves the determination of the stress field. A striking result is the good agreement between the re-analysed overcoring data and the existing hydraulic fracturing data. The deviations for the horizontal stresses between the re-analyzed overcoring data and the existing hydraulic fracturing data are approximately 3 MPa. The deviation in the orientation of maximum horizontal stress is approximately 10-20°. Nous avons analysé les résultats de mesures de contrainte par surcarottage réalisées sur le site Zedex, du laboratoire souterrain HRL d’Aspö, en suède. Deux types de cellule de mesure ont été utilisés sur ce site : la cellule à 9 jauges (du type CSIR) et la cellule à 12 jauges (du type CSIRO HI). Un programme d’inversion mettant en œuvre une norme par moindres carrés a été développé et validé. Les champs de contrainte primaires et secondaires du site Zedex ont été évalués d’une part en considérant chaque mesure isolément, d’autre part en intégrant l’ensemble des données de déformation dans une inversion unique. Nos résultats suggèrent que l‘association des diverses mesures dans une intégration unique améliore nettement la détermination du champ de contrainte. Un résultat intéressant est le bon accord entre ces nouveaux résultats et les résultats des mesures par fracturation hydraulique. Les écarts sur l’amplitude des contraintes horizontales est de l’ordre de 3 Mpa, les écarts sur les orientations de l’ordre de 10-20°. Auf dem Zedex Test Gelände im Äspö Festgesteinslabor (HRL) wurde eine Spannungsanalyse mittels Overcoring Spannungsmessungen durchgeführt. Hierzu wurden zwei verschiedene Methoden verwendet: das 9-kanal Borre Gerät (CSIR- Ausführung) und die 12-Kanal CSIRO HI Zelle. Inversionsprogramme, die auf dem “least-squares”- Kriterium basieren, wurden entwickelt und kalibriert. Das primäre und sekundäre Spannungsfeld des Zedex Test Geländes wurde sowohl aus Verformungsdaten individueller Zellen als auch aus Kombination beider Zellen ermittelt. Wir nehmen an, daß die Kombination der Messergebnisse beider Geräte die Bestimmung des Spannungsfeldes signifikant verbessert. Überzeugender Beweis hierfür ist die gute Übereinstimmung der überprüften Overcoring Daten und Ergebnisse aus existierenden Hydraulic Fracturing Versuchen. Die Abweichungen der horizontalen Spannungen aus beiden Datensätzen ist etwa 3 MPa und Abweichungen der Orientierung der größten Horizontalspannung liegen bei etwa 10-20°.

Jan 1, 2003

By H. Willenberg, J. S. Coggan

ABSTRACT: Although individually both continuum and discontinuum numerical analyses provide useful means to analyze rock slope stability problems, complex failures typically involve mechanisms related to both existing discontinuities (i.e. discontinuum) and deformation and brittle fracture of intact rock (i.e. continuum). One such example is the 1991 Randa rockslide in the southwestern Swiss Alps, where failure involved several complex mechanisms, which require the consideration of progressive failure and rock mass strength degradation. This paper presents results from a series of hybrid finite-/discrete-element models directed towards the explicit modelling of brittle fracturing in natural rock slopes, enabling the modelling of progressive failure, from initiation, through to the development of catastrophic failure, transport and deposition. RÉSUMÉ: Si les modélisations numériques de type continu ou discontinu fournissent des outils utiles pour l’analyse de problèmes de stabilité de pentes rocheuses, elles montrent de sérieuses limitations lorsque des mécanismes de rupture complexes impliquent des processus liés autant aux discontinuités préexistantes qu’au développement progressif de nouvelles fractures. Ceci se retrouve typiquement dans l’exemple de l’éboulement de 1991 à Randa dans les Alpes suisses du sud-ouest, où la rupture a impliqué plusieurs mécanismes complexes nécessitant la prise en considération de la fracturation progressive ainsi que de la dégradation de la résistance des masses rocheuses. Cet article présente des résultats provisoires d'une série de modèles hybrides orientés vers la modélisation explicite de la fracturation de pentes naturelles, permettant la modélisation de fractures progressive de leur initiation jusqu’à leur développement, leur rupture catastrophique, leur transport et leur déposition. ZUSAMMENFASSUNG: Obwohl numerische Kontinuum- und Diskontinuum-Berechnungen einzeln nützliche Ergebnisse zur Stabilitätsanalyse von Felshängen liefern, sind komplexe Felsrutschungen typischerweise mit Mechanismen verbunden, die sowohl durch bestehende Trennflächen (s.a. Diskontinuum-Ansatz) als auch durch die Deformation und das Versagen intakter Felsbereiche (s.a. Kontinuum-Ansatz) bedingt werden. Ein Beispiel für einen solchen Sachverhalt ist der Bergsturz von Randa 1991 im südwestlichen Teil der Schweizer Alpen, bei dem die Rutschung mehrere komplexe Mechanismen umfasste, so dass “progressive failure” und Verminderung der Gebirgsfestigkeit in Betracht gezogen werden müssen. Dieser Artikel beschreibt vorläufige Ergebnisse einer Reihe von hybriden Modellrechnungen (Finite-/Diskrete-Elemente). Diese haben zum Ziel, explizit das bruchhafte Versagen natürlicher Felshänge zu modellieren, wobei das progressives Versagen im ganzen modelliert wird, von der Anfangsphase über die Entwicklung zum katastrophalen Versagen und den Transport und die Ablagerung der Rutschmassen.

Jan 1, 2003

By J. -H. Wu, S. Nishiyama, Y. Ohnishi

The behaviors and stress distributions of the inclined jointed rock masses with different dip angles obtained from DDA are compared to the results of laboratory tests. By calculating the block stress distributions, it is confirmed that DDA can reproduce the arching around the trap door when lowering the trap door. The shapes of arching change with the angles of inclined layers. In addition, the earth pressures acting on the trap door shows non-symmetrical distributions when the layers are not horizontal. The stress concentration occurs in one side of the rock masses close to the trap door. Furthermore, the surface settlements are also related to the inclined angle, and the loosening zone in rock masses can be different from Terzghi’s theory [1]. Since, simulations have good agreements with the laboratory test , it demonstrates the applicability of DDA to explain the mechanical behaviors of tunnel, such as arching phenomenon, non-symmetrical earth pressure distributions acting on the trap door, and the surface settlement profile in the jointed rock masses. Dans cet article est décrite l’étude numérique du perçage d’un tunnel dans un massif de couches rocheuses jointes inclinées. La simulation à l’aide de l’Analyse de Déformation Discontinue (DDA), en faisant varier l’angle d’inclinaison des couches de roche, nous apporte des résultats en termes de distributions de contraintes et de comportement des couches, résultats qui sont ensuite comparés avec des résultats de tests en laboratoire. Les résultats confirment le fait que la DDA est capable de reproduire le phénomène d’arcage autour de la trappe lorsque la trappe s’abaisse. Les formes d’arcage varient selon l’angle d’inclinaison des couches de roche. Par ailleurs, lorsque les couches ne sont pas horizontales, la distribution de pression agissant sur la trappe est assymmétrique. La concentration de contraintes se produit du coté proche de la trappe. De plus, les tassements de surface dépendent eux aussi de l’angle d’inclinaison. En conséquence, les résultats de simulation sont en accord avec les tests en laboratoire, ce qui prouve que la DDA permet d’expliquer des comportements mécaniques du tunnel tels que l’arcage, les distributions assymmétiques de pression du sol sur la trappe, ainsi que le profil du tassement de surface dans la masse de roches jointes. Dieser Beitrag beschreibt eine numerische Studie über Tunnel im geklüftetem Fels. Das Verhalten und die Druckverteilungen in den unterschiedlich geneigten und geklüfteten Felsenmassen wird mit Hilfe des Discontinuous Deformation Analysis Programms (DDA) simuliert, und mit Laborversuchen verglichen. Die Resultate bestätigen, dass DDA der Gewölbewirkung im „Trapdoor“ Experiment gut reproduzieren kann. Die Form des Gewölbes, ändert sich mit unterschiedlichen Neigungswinkeln der Schichten. Bei geneigten Schichten entstehen unsymmetrische Druckverteilungen. Auch die Oberflächenabsenkung ist von dem Neigungswinkel abhängig. Die gute Übereinstimmung der Simulationen mit den Laborversuchen zeigt, dass die DDA-Methode gut geeignet ist, um das mechanische Verhalten von Tunneln, wie z.B. den Effekt der Gewölbewirkung, die unsymmetrischen Druckverteilungen bei geneigten Schichten, oder die Oberflächenabsenkung in geklüfteten Felsenmassen, zu erklären.

Jan 1, 2003

By R. G. Cawthorn

The earliest authenticated scientific report of the occurrence of platinum in rocks from the Bushveld Complex appears to be by William Bettel on 10th November 1906. Thereafter, prospecting of the chromite-rich rocks for platinum proved frustrating. I suggest that the resurgence of interest shown by Dr Hans Merensky in 1924 resulted from his realization that newly-panned platinum had a different grain size from that in the chromite layers and indicated a different source rock, which he located and it became known as the Merensky Reef.

Jan 1, 2006

By B. Derin, T. Uzunoglu, O. Yücel

In this study, reduction behaviours of Turkish chromite concentrate (48 % Cr2O3, 13.30 % FeO, 18.33 % MgO, 12.37 % Al2O3, 5.76 % SiO2) and nickel oxide by Fe-C alloy in graphite crucible were investigated. In the first stage of experiments, steel scraps were melted in graphite crucibles and were saturated with carbon at 1600 °C and 30 min. In the second stage, mixtures of different amount of chromite concentrate, nickel oxide and flux additives (CaO,SiO2 and CaF2) were charged into the graphite crucible containing the Fe-C alloy and heated to 1600 °C for different reduction times (0-180 min) under argon gas. The highest Cr and Ni con-tents in alloys were found as 11.41 and 14.37 % and the highest Cr and Ni recoveries were found as 88 and94 %, respectively at 180 min.

Jan 1, 2007

By D.W. Gentry

1. Book reviews Mine investment analysis, by D.W. Gentry and T.J. O'Neil. Society of Mining Engineers (Caler No. D, Litleton, CO 80127, U.S.A.). US$50.Finance for the mineral industry, by C.R. Tinsley, M.E. Emerson, and W.D. Eppler. Society of Mining Engineers (Caler No. D, Litleton, CO 80127, U.S.A.). US$50. 2. Mintek reports The folowing reports are available from the Council for Mineral Technology, Private Bag X3015, Randburg, 2125 South Africa. They are free of charge to South African addressees, but there is a handling charge of US$25 per copy for reports sent to overseas destinations. Report M291D Removal of pebbles and pre-crushing of selected feed material in autogenous milling, by D.I. Hoyer. First issued Nov. 1986, reissued Apr. 1988. 16 pp Report M350 A survey of miling and mil-lining practice on South African gold mines, by M.S. Powel. Jun. 1988. 30 pp Report M356 The distribution of cobalt in mineral constituents of the Merensky Reef and UG-2 Chromitite Layer of the Bushveld Complex, by G. Smits. Jut. 1988. 13 pp Report M359 The development of a mobile laboratory for the monitoring of gold and cyanide in alkaline cyanide solutions, by R.V.D. Robert, C. Pohlandt-Watson, H.J. du Plessis, and G.D. Marshal. Aug. 1988. 17 pp. Productivity and technology The Metalurgical Society and Geselschaft Deutscher Metalhuten-und-Bergleute are sponsoring the Symposium on Productivity and Technology in the Metalurgical Industries, which is to be held in Cologne, West Germany, from 17th to 22nd September, 1989.Non-ferrous smelting Commemorating a centenary of lead smelting and refining at Port Pirie, the Conference on Non-ferous smelting wil be held at Port Pirie from 17th to 20thSeptember, 1989. International trade fairs From 20th to 26th May, 1989,4 major international trade fairs wil be held in Disseldorf, West Germany.

Jan 1, 1988

By P. H. S. W. Kulatilake, B. Malama

To simulate brittle rocks, a mixture of glastone, sand and water was used as a model material. Thin galvanized sheets were used to create joints in blocks made out of the model material. To investigate the failure modes and strength, both the intact material blocks as well as jointed model material blocks of size 35.6 × 17.8 × 2.5 cm having different joint geometry configurations were subjected to uniaxial and biaxial compressive loadings. Results obtained from the intact model material blocks are used to validate a new intact rock failure criterion for biaxial loading. Results obtained from both the intact and jointed model material blocks are used to develop a strongly non-linear new rock mass failure criterion for biaxial loading. In this failure criterion, the fracture tensor component is used to incorporate the directional effect of fracture geometry system on jointed block strength. The failure criterion shows the important role the intermediate principal stress plays on rock mass strength. Zur Simulation spröder Gesteinsarten wurde ein Modellmaterial aus Dentalgips, Sand und Wasser hergestellt. Daraus wurden Blöcke gegossen, in denen mittels dünnen, galvanisierten Blechen Trennflächen erzeugt wurden. Die Blöcke mit Abmessungen von 35.6 × 17.8 × 2.5 cm wurden in einaxialen und biaxialen Druckversuchen belastet. Es wurde das Versagensverhalten und die Festigkeit von intakten Blöcken sowie durchtrennten Blöcken mit unterschiedlicher Trennflächengeometrie untersucht. Aus den Ergebnissen der Versuche an intaktem Material wurde ein neues Versagenskriterium für biaxiale Belastungen validiert. Die Ergebnisse der Versuche an intakten und durchtrennten Blöcken wurden verwendet, um ein neues stark nicht-lineares Versagenskriterium für geklüftetes Gebirge unter biaxialer Belastung abzuleiten. Darin wird der Bruchtensor verwendet, um den Einfluss der Trennflächengeometrie auf die Festigkeit zu erfassen. Das Versagenskriterium stellt heraus, welche Bedeutung die mittlere Hauptspannung für die Gebirgsfestigkeit hat. Un mélange de platre dentaire, de sable et d’eau a été utilisé pour développer un matériau analogue des roches fragiles. De fines feuilles galvanisées permettent de créer des discontinuités représentatives des discontinuités naturelles dans des bloques fabriqués avec ce matériau analogue. Les modes de rupture et la résistance, tant pour le matériau intact que pour le matériau avec ses discontinuités, ont été étudiés sur des blocs de 35.6 × 17.8 × 2.5 cm soumis à des efforts de compression uniaxiaux et biaxiaux. Différentes configurations de géométrie de discontinuités ont été considérées. Les résultats obtenus à partir des blocs intacts permettent de vérifier un nouveau critère de rupture pour les roches intactes soumises à des efforts biaxiaux. Les résultats obtenus, tant avec les blocs intacts qu’avec les blocs avec discontinuités, sont utilisés pour développer un nouveau critère de rupture, fortement non linéaire, pour les massifs rocheux soumis à des chargements biaxiaux. Dans ce critère de rupture, un tenseur de fractures est introduit pour caractériser les effets directionnels de la géométrie des systèmes de discontinuité sur la résistance des blocs avec discontinuités. Ce critère de rupture démontre le rôle important de la contrainte principale intermédiaire sur la résistance des massifs rocheux.

Jan 1, 2003

By T. Saito, S. Murata

An original concept of JRC-diagram that can evaluate JRC and its size-effect by using a fractal model was proposed. In order to confirm the applicability of the JRC-diagram, first, JRC of the tensile fracture surfaces of a granite and a sandstone were evaluated by both the JRC-diagram and Barton's JRC-profiles, and then, it was compared with the JRC inversely calculated from the peak shear strength that is obtained from the shear test for each fracture using Barton's empirical equation. As a result, JRC evaluated by the JRC-profiles was much smaller than the inversely calculated JRC. On the other hand, it became clear that JRC evaluated by the JRC-diagram is almost the same with the inversely calculated JRC, if the size of interlocking is evaluated correctly. Therefore, for the JRC evaluation, it is thought that the JRC-diagram is more applicable than the JRC-profiles. Als ein neues Verfahren zur Bewertung des Rauheitsindexes JRC für die Bruchfläche von Felsenschichten anhand eines fraktalen Modells, wobei auch der Maßeffekt berücksichtigt wird, wird ein JRC-Diagramm vorgeschlagen. Um die Angemessenheit der Bewertung vom JRC mit diesem JRC-Diagramm festzustellen, wurden die JRC-Werte an einer Bruchfläche zwischen Granit und Sandstein sowohl mit dem JRC-Diagramm als auch mit dem herkömmlichen JRC-Profilverfahren bewertet. Anschließend wurden die durch die beiden Verfahren ermittelten Werten mit den JRC-Werten verglichen, die von den Schertestergebnissen mit Hilfe von Bartonschen Erfahrungsformel zurückgerechnet werden können. Daraus ergab sich, daß das JRC-Profilverfahren ziemlich kleinere JRC-Werte gibt als bei der Zurückrechnung, während die JRC-Werte durch das JRC-Diagramm unter entsprechender Bewertung des Ineinandergreifungsmaßes an der Bruchfläche beinahe gleich sind wie die zurückgerechneten Werte. Diese Tatsache weist darauf hin, daß das JRC-Diagramm eine bessere JRC-Bewertungsmethode als das JRC-Profilverfahren darstellt. Nous avons proposé le diagramme JRC, nouvelle méthode d'évaluer JRC qui est un indice de rugosité superficielle d'une fracture de roche à l'aide du modèle de fracturation, compte tenu de son effet d'échelle. Pour vérifier la validité de JRC évalué au moyen de ce diagramme, nous avons évalué JRC d'une fracture de roche, granite et grès, par le diagramme JRC et le profil JRC, méthode conventionnelle, et les résultats ainsi obtenus ont été comparés avec la valeur de JRC calculée en sens inverse à l'aide de la formule empirique Barton sur la base des résultats de l'essai de cisaillement des fractures. Il en résulte que la valeur de JRC obtenue par le profil JRC était assez faible en comparaison avec la valeur calculée en sens inverse alors que celle de JRC obtenue par le diagramme JRC correspondait approximativement à la valeur calculée en sens inverse à condition d'évaluer l'échelle d'endentement d'une fracture. Par conséquent, nous considérons que le diagramme JRC est une meilleure méthode d'évaluation de JRC par rapport au profil JRC.

Jan 1, 2003

By J. Du, V. Shukla, C. R. Kumar, U. Shivangi, D. P. Chakraborty

During the processing of iron ores, a large quantity of low-grade tailings containing abundant iron values in fine particle size range is produced. Due to the increasing demand in the high-grade ores for metallurgical operations and the stringent environmental conditions imposed on mining activity, it is essential to utilise the waste tailing pond slimes. Recovery of iron values from these tailing ponds not only enhances the life of the existing operating mines, but also enables achievement of a sustainable process. Iron ore tailing/slime (-150 μm) is produced after scrubbing and wet screening of a low-grade iron ore. Tailing beneficiation of iron ore has been addressed either by flotation or wet high intensity high gradient separation. The present paper aims to recover iron values from discarded slime containing assay ~56% Fe, ~6.5% SiO2, and ~7.0% Al2O3 from the Noamundi processing plant by using a high gradient magnetic separator (HGMS). In this process, tailings are effectively processed with a vertical pulsating high gradient magnetic separator to produce a relatively high-grade iron concentrate. The results of investigation indicate that this novel process is capable of producing an iron concentrate assaying ~ 60% Fe and ~3.25% alumina with a yield of ~55 % on weight basis and recover > 65 % iron bearing particles from the tailings. More importantly, the corresponding tailing contained ~45% Fe. It was concluded that this novel process may be effectively used to recover iron values from low-grade hematite tailings. Keywords: Iron ore slime, Fe recovery, HGMS, yield, Noamundi

Jan 1, 2020

O.F.S. Branch, Welkom Minutes of a Committee Meeting held in the V.LP. Lounge of the Welkom Club on Tuesday, 26th June, 1973, at 5.00 p.m. Present Mr C. J. Isaac (in the Chair), Mr D. A. Smith, Mr G. Young,

Jan 1, 1974

By A. K. Biswas

Reviewer: R. H. Eric This edition is organized in twenty-three chapters, and contains exactly 500 pages including three appendices and an index. The first and second editions were published in 1976 and 1980 respectively, and both contained nineteen chapters. The second edition brought the operating data and process descriptions up to date. The third edition covers comprehensively the changes that have taken place in the primary copper industry over the past two decades. For example, reverberatory furnaces now make up only a third of the major primary smelting furnaces, compared with about three-quarters in the 1970s. Control of air and water pollution and recycling are given much more emphasis, along with novel and emerging technologies.

Jan 1, 1995

By J. P. Josien, Didier C.

ABSTRACT: France now faces the closure of most of its mining sites. Surface instability risk may sometimes remain, especially where large underground voids exist. This paper illustrates the importance of failure mechanisms identification in order to define properly how to manage the residual risk. RESUME: La France fait aujourd’hui face à la fermeture de ses exploitations minières. Des risques d’instabilités de surface peuvent persister, notamment lorsque des vides résiduels existent au sein des travaux souterrains. L’article illustre l’importance que présente la nature des mécanismes de rupture potentiels dans le choix des mesures compensatoires à adopter pour gérer le risque résiduel à long terme. ZUSAMMENFASSUNG: In Frankreich stellt sich derzeit das Problem der definitiven Schliessung des meisten Bergwerke. In manchen fällen ist die Stabilität der Oberfläche nicht garantiert, speziell wenn unter Tage nicht verfüllte Hohlräume verblieben sind. Dieser Bericht zeigt die Wichtigkeit, bei der Auswahl geeigneter Langzeit-Risikomanagementmethoden, der verschiedenen Mechanismen mit denen ein eventueller Bruch an die Tagesoberfläche geraten kann.

Jan 1, 2003

By T. H. Yang, Q. K. Wang, T. Song, J. W. Zhou

The grinding circuit can be one of the most important mineral processing circuits in plants. Along with the application of large-scale milling machines, the design and optimisation of the operation strategy for grinding circuits is more complicated. An in-house grinding process simulation tool was developed to mass balance, model fit and simulate crushing, grinding and classification circuits. An industrial grinding and classification circuit in a copper mine was modelled, and the modelling parameters were verified by a particular group of plant survey data. To justify the prediction ability of the fitted models, the model predictions under different operation conditions were compared with another group of plant survey data. Then the model predicted the effects on the circuit of changing operating conditions. Circuit analysis of the comminution process for water feed to a SAG mill, water feed to sump, the rolling speed of a SAG mill and the percentage of ball filling in a SAG mill was put into practise, based on the simulation results. The simulation results can be used to help plant operators understand the features of the comminution process and may help to build a knowledge library for process control. Keywords: Process modelling, grinding, comminution, circuit analysis

Jan 1, 2020