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By Z. Szczepanik, D. Milne, K. Kostakis

Abstract This paper presents the results of a series of creep tests performed on a total of nine samples of Lac du Bonnet granite from the Underground Research Laboratory near Pinawa, Canada. Each of the nine samples were subjected to stresses in excess of 80% of the average uniaxial compressive strength of the granite and were maintained at that level of constant loading for periods of time ranging between a few minutes and several months. Acoustic emission was recorded in order to monitor the development and accumulation of brittle microfracture damage in the samples throughout the long-term loading. According to previously published theoretical predictions and field results, as well as similar experimental results of creep tests in granite, samples should fail when loaded to 70% of their UCS for an extended period of time. Six of the samples did not fail when subjected to stresses in excess of 80% of their UCS over periods of several months and were subsequently subjected to uniaxial compression to failure. The average strength of the samples that had previously been subjected to long-term loading were comparable to the average published strength of this rock. Three of the nine samples had increased end confinement and these three samples failed under long term loading. Résumé Cet article présente les résultats d'une série d'essais de fluage de roche exécutés sur neuf échantillons de granite de Lac du Bonnet, du laboratoire souterrain de recherches près de Pinawa, Canada. Chacun des neuf échantillons a été alors soumis aux charges au-dessus de 80% de la résistance à la UCS moyenne du granit et a été maintenu à ce niveau du chargement constant pendant des périodes s'étendant entre quelques minutes et plusieurs mois. L'émission acoustique a été enregistrée pendant les essais afin d'obtenir des indications des dommages pendant le chargement à long terme. Selon des résultats théoriques précédemment édités et les résultats expérimentaux semblables des essais à long terme en granite, échantillons devrait échouer si chargé à 70% de leur UCS pendant une période prolongée. Six des échantillons n'ont pas cassé quant ils ont été soumis aux charges au-dessus de 80% de leur UCS et ont été plus tard soumis à la compression uniaxiale à la rupture. La force moyenne des échantillons qui avaient été précédemment soumis au chargement à long terme étaient comparable à la force éditée moyenne de cette roche. Trois des neuf échantillons avaient augmenté le confinement de fin et ces trois échantillons ont cassé sous le chargement à long terme. Zusammenfassung Dieser Artikel beschreibt die Resultate von Kriechversuchen, die an neun Proben aus dem Lac du Bonnet Granit des "Underground Research Laboratory" bei Pinawa in Kanada durchgeführt wurden. Jede der neun Proben wurde Drücken unterworfen, die mehr als 80% der einaxialen Druckfestigkeit des Granites entsprechen. Diese Drücke wurden für verschiedene Zeitspannen von wenigen Minuten bis zu einigen Monaten auf einem konstanten Niveau gehalten. Während der gesamten Langzeitbelastung wurden akustische Emissionen aufgezeichnet, um die Entwicklung und gesamthafte Beschädigung der Proben durch Sprödbruch aufzuzeichnen. Entsprechend bisher veröffentlichter theoretischer Vorhersagen, Feldversuchen und auch experimentellen Resultaten von Kriechversuchen an Granitproben wäre ein Versagen der Proben zu erwarten gewesen, wenn sie über längere Zeit einer Last von 70% ihrer einaxialen Druckfestigkeit unterworfen werden. Wider Erwarten trat bei sechs der Proben kein Versagen ein, als sie mit über 80% ihrer einaxialen Druckfestigkeit über mehrere Monate belastet wurden; daher wurden sie im Anschluss bei einaxialer Kompression zum Versagen gebracht. Die mittleren Festigkeiten der im Langzeittest verwendeten Proben sind vergleichbar mit den normalerweise für diesen Gesteinstyp angegebenen Festigkeiten. Drei der neun Proben versagten unter der Langzeitbelastung; diese drei Proben hatten eine erhöhte Endflächenreibung.

Jan 1, 2003

By G. van Aswegen

Seismic monitoring became commonplace in the deep South African gold mines in the early 1990’s. The discipline has, to a large extent, developed beyond the ‘research’ stage, and a ‘Guide to Seismic Monitoring in Mines’ has been accepted by the Department of Minerals and Energy1. Although ongoing research is a requirement for the achievement of all the objectives of seismic monitoring in mines, sufficient knowledge exists to apply seismic monitoring for routine seismic hazard assessment as an aid to risk management. The design and management of seismic monitoring systems can be tested against requirements spelled out in the ‘Guide’. Assuming the seismic monitoring system performs as per requirement, the best practice for routine seismic hazard assessment in mines includes • Long term seismic hazard assessment: through back analysis of seismic data and correlation with numerical modelling output, reasonable tests for planned mine designs are possible. • Medium term seismic hazard assessment: o Spatial analysis through contouring of seismic strain related parameters, with superimposed contours or event plots of stress related parameters allow the delineation of potential instabilities in space. o Quantitative and statistical analyses of seismicity in smaller spatial units (usually encompassing production sites) allow the comparative seismic hazard rating of different areas/sites so that rock engineering input and risk management can be optimised • Short term seismic hazard assessment relies mainly on time history analyses of particular seismicity parameters. The temporal patterns are controlled by a combination of temporal and parameter filters, the optimisation of which determines the success rate.

Jan 1, 2003

By C. A. Garzonio, A. M. G. Affuso

The paper describes the analyses and the tests carried out on representative slabs of white Carrara marble which have highlighted the correlation between the micro fabrics and physical and mechanical parameters. The aim is to determine the conditions which indicate the triggering and evolution of the deformation phenomena. La note écrit l’analyse et les epreuves effectuée sur un echantillon représentatif de nombreuses dalles en marbrede Carrara. Les études montrent la correlation entre la minéralogie et les paramètres physiques et mecaniques. Le but est déterminer les conditions qui indiquent l’amorçage et l’evolutions des phénomènes de déformation. Diese Arbeit gibt eine Beschreibung der experimentalen Untersuchungen und der Analysen über die Marmorplatten von Carrara. Daraus resultiert, dass die Charakterisierung der Mineralogie und die Porosität der Gesteinsmaterialien die physikalische mechanische Degradation beurteilen und die Krümmungen bestimmen.

Jan 1, 2003

By J. Kortnik

Mining has always been, and still is, an activity which is vital for the development of mankind. This is because a predominant proportion of industrial products and energy is produced from raw materials that are excavated using mining methods. The need for environmental protection and the close proximity of urban settlements and mines in Slovenia have necessitated ever stricter requirements for the excavation of raw materials and the introduction of more environmentally-friendly mining methods. This is achieved by implementing a closed eco-technological cycle of raw material excavation within the scope of mining methods. In surface mines, this means prompt reclamation of the degraded surfaces, and in underground mines the use of methods with minimized impact on the surface and on underground water. In underground mines, mining methods with backfilling installed according to the multi-barrier disposal system are the only ones that allow the possibility of implementing a closed eco-techno-logical cycle of excavating raw materials. Various industrial waste materials are also included in the backfilling material in order to improve its strength properties. Backfilling consisting of several different waste materials is produced in the form of a composite. Before backfilling consisting of waste material composites can even begin to be used in mines, an environmental impact assessment of its suitability for mines needs to be made. In order to make such an assessment, a pressure leaching cell and an open diffusion cell were made, i.e. a pressure leachate test and a sorption test were developed. The two cells and the developed tests will enable the study of the influence of backfilling on the environment if installed in an underground mine. The pressure leachate test performed with the use of the pressure leaching cell simulates leaching from a consolidated backfill during the seeping of underground water into the backfilling material under pressure. The sorption test performed in an open diffusion cell simulates the flow of eluate leached from the backfilling material through the rock/geotechnical barrier. The two tests were developed in such a manner that they are performed either in succession immediately after one another, but they can also be performed separately at a certain time interval. The paper presents an assessment of the suitability of backfilling made of different waste material composites. Keywords: environmental impact assessment, multi-barrier disposal system, waste material composites, pressure leachate test, sorption test, pressure leaching cell, open diffusion cell, eco-technological cycle, mining methods with backfilling.

Jan 1, 2003

Work undertaken in the field of cut-off grade optimization has not advanced much beyond the work undertaken by Lane in 1988. His definitive work is based on the calculus of the Net Present Value criterion which is the most widely understood, consistent, and appropriate method by which sequential cash flows arising from the extraction of mineral reserves from an exhaustible resource can be represented. Although the mathematics is not complex Lane’s method is not a widely appreciated or applied approach to maximizing the value of a mining operation through selection and balancing of operational cut-off grades. Three stages in a mining operation namely, mining, processing and marketing were defined by Lane and the economics of each stage are identified and isolated to provide an optimum cut-off for each stage. Points of intersection along the present value curves for each stage of a mining operation are used to identify balancing cut-off grades at points where the capacity of the mining, processing and marketing stages is fully utilized and the Net Present Value of the operation is optimized. Data that simulate a small, deep-level Witwatersrand-type gold mine with an average grade of 6 g/t Au and a logrithmic variance of 1.2,are applied to the model to illustrate the benefits of representing cut-off grades in terms of present value curves for different segments of a mining operation. Keywords: Cut-off grade, Net Present Value, grade-tonnage curve, balancing cut-off grade, mining, processing, marketing.

Jan 1, 2003

By A. K. Singh, R. Singh, P. K. Mandal

On the basis of in situ study of pillar loading at different sites, an attempt is made in this paper to visualize the development of mining induced stress under varying geo-mining conditions. Field study demonstrated interesting interaction between size of pillar and nature of roof rock mass under the influence of increasing dimension of the excavation. Stiffness of pillars/overburden, extraction ratio and depth cover are observed to be the important parameters for the estimation of mining induced stress over the pillar. These parameters influence, both, the value of ultimate induced stress (vertical) and its range of influence ahead of the face line. Further, it is observed that the change in width/height (w/h) ratio of a pillar has got considerable influence over the nature of mining induced stress over it. Impact of highly dynamic nature of mining induced stress over the natural supports is observed to be the most serious factor for the safety of working under a hard and massive roof rock mass. On the basis of these observations, a conceptual model of interaction between the natural support and overlying strata is discussed in the paper. ZUSAMMENFASSUNG: Aufgrund ist in situ Studium von Säule Beladung an verschiedenen Stellen, ein Versuch in diesem Papier gemacht, die Entwicklung des Bergbaus vostellen sich, Spannung unter Änderung von Geo Bergbau von Bedingungen hat veranlaßt. Feld Studium hat interessante Wechselwirkung zwischen Größe von Säule und Natur von Dach Felsen Masse unter dem Einfluß von Vermehrung Dimension des excavation vorgeführt. Steifheit des Säulen Overburden, Herausziehung Verhältnisses und Tiefe sind beobachtet bedeckt, die wichtigen Parameter für die Schätzung des Bergbaus zu sein, Spannung über der Säule hat veranlaßt. Diese Parameter beeinflussen, beide, der Wert allerletzter veranlaßter Spannung (senkrecht) und sein Bereich des Einflusses voraus von der Gesicht Linie. Weiter ist, es beobachtet, daß die Änderung in Breite Höhe (W H) Verhältnis einer Säule beträchtlichen Einfluß über der Natur des Bergbaus erhalten hat, Spannung hat darüber veranlaßt. Schlag sehr dynamischer Natur des Bergbaus ist Spannung über den natürlichen Stützen beobachtet hat veranlaßt, der ernsteste Faktor für die Sicherheit des Arbeitens unter einer harten und massiven Dach Felsen Masse zu sein. Aufgrund dieser Beobachtungen, ein begriffliches Modell der Wechselwirkung zwischen der natürlichen Stütze und der überlagernde strata ist im Papier diskutiert. RESUME: En se basant sur dans l'étude de situ de chargement de pilier aux sites différents, une tentative est faite dans ce papier pour envisager le développement de creuse la tension persuadée sous varier de conditions de geo creuse. L'étude de champs a démontré l'interaction intéressante entre la taille de pilier et la nature de masse de rocher de toit sous l'influence d'augmenter de dimension de l'excavation. La raideur de piliers overburden, la proportion d'extraction et la couverture de profondeur est observée pour être les paramètres importants pour le jugement de creuse la tension persuadée par-dessus le pilier. Ces paramètres influencent, les deux, la valeur de tension persuadée ultime (vertical) et sa gamme d'influence en avant de la ligne de face. Plus, il est observé que le changement dans la largeur hauteur (le w h) la proportion d'un pilier a reçu l'influence considérable par-dessus la nature de creuse la tension persuadée par-dessus il. L'impact de nature extrêmement dynamique de creuse la tension persuadée par-dessus les soutiens naturels est observé pour être le facteur le plus sérieux pour la sûreté de fonctionnement sous une masse de rocher de toit dure et massive. En se basant sur ces observations, un modèle conceptuel d'interaction entre le soutien naturel et les couches recouvrant est discuté dans le papier.

Jan 1, 2003

By M. L. Smith, G. Karunatillake

Lead-zinc production at MIM, Mount Isa includes three mines, a lead concentrator, zinc filter plant and lead refinery. Lead production is vertically integrated with lead-silver bullion shipped from Australia to London for refining. Zinc is sold as a concentrate. All three mines have reached varying states of maturity mining a multitude of orebodies having significant variation in grades and metallurgical recovery for three metals. Based on current levels of measured resources, the remaining project life is at least ten years. The objective is to schedule production over the life of all three mines so as to maximize the present value of the complex. Additional scheduling complexity arises out of the implementation of long-term schedules, capital expansion projects for both mining and processing, the presence of substantial inferred reserves and interactions with MIM copper production. A large-scale, time-dynamic, life-of-complex Mixed Integer Program (MIP) production schedule was formulated to optimize lead/zinc cash flow based on a detailed life of project production scheduling study. The requirements for such a study are detailed herein. The operational feasibility of the MIP solution is compared against a non-optimal approach to strategic life-of-mine scheduling. The strategic planning emphasis placed on the MIP is compared to the implementation of a life-of-mine schedules at Mount Isa using spreadsheets and other popular commercial mine schedulers.

Jan 1, 2003

By H. H. Einstein

This paper reviews how uncertainty has been dealt with over the past 40 years using the decision making cycle as a frame of reference. The review of the phases of this cycle, as applied to rockmechanics and rock engineering, namely characterization, performance analysis, updating and decision making shows that in each, progress has been made over the past 40 years, although most of the basic concepts existed already in the 1960’s. Characterization is the area in which the greatest scientific steps were taken, this phase and performance analysis also gained from the tremendously expanded computational capabilities which allow one to use both more complex and more practically oriented models. The greatest practical advance is without using any doubt in risk based decision making although its acceptance shows interesting differences between different professions. Dans l’article suivant on utilise le cycle de décision pour illustrer le développement du traitement des incertitudes en mécanique des roches et en construction en roche dans les quarante années passées. La revue des phases du cycle de décision montre qu’on a fait du progrès dans chaque phase du cycle de décision, c’est à dire dans la caractérisation, dans l’analyse et la prédiction du comportement, dans l’actualisation et dans l’acte de décision, même si les concepts fondamentaux existaient déjà dans les années 1960. Les plus grands avancements scientifiques se trouvent dans le domaine de la caractérisation tandis que l’analyse prédictive profitait du développement de l’informatique qui a mené à des modèles plus complexes mais aussi plus pratiques. Le plus grand progrès est sans doute dans le domaine de l’acte de décision sur la base des risques. Ce procédé est devenu assez commun même s’il y a encore des différences d’acceptation entre différentes professions. Im vorliegenden Artikel wird der Entscheidungszyklus gebraucht, um darzustellen wie sich derUmgang mit Unsicherheiten im Felsbau während der letzen 40 Jahre entwickelt hat. DerÜberblick über die Phasen des Entscheidungsprozesses zeigt, dass bei der Anwendung in derFelsmechanik und im Felsbau, in allen Phasen d.h. bei der Charakterisierung, bei der analytischenVorhersage, beim Aktualisieren und bei der Entscheidungsfindung Fortschritte gemacht wurden,obwohl die grundlegenden Konzepte bereits in den 1960er Jahren existierten. Im Gebiet derCharakterisierung gab es wohl die grössten wissenschaftlichen Entwicklungen, während dieanalytische Vorhersage vor allem von den Fortschritten der Informatik profitierte, welchekomplexere wie auch praktischere Modelle möglich machte. Der grösste Fortschritt ist ganz sicherin der Entscheidungsfindung zu beobachten, wo Risikobetrachtungen gang und gäbe sind, obwohlhier noch einige Unterschiede zwischen verschiedenen Berufsgattungen zu finden sind.

Jan 1, 2003

By A. J. Basu

New technologies, such as computer based learning, wireless computing, internet2, online courses, distance learning, and in general multimedia applications are being implemented in the higher education sector in an increasing manner. However, these implementations are not coherent, and lack standards. However, one example of the existing standards is the development and implementation of the virtual learning environments. These technology tools help in delivering the eLearning objectives. There is a major initiative in Europe (eEurope action plan) in promoting eLearning towards creating a knowledge-based society. Technology implementation is the major driver for achieving the eLearning objectives. A two-year pilot project on implementing technology tools including virtual learning environment (VLE), video-conferencing, and simulation and visualization was carried out for providing a blended learning environment for undergraduate and graduate students in Mining Engineering (undergraduate) and Mineral Deposit Evaluation (M.Sc.) course at the Imperial College London. The pilot project was funded by the Imperial College Centre for Educational Development (ICCED). The project did contribute towards activities for creating an institute-wide eLearning strategy in line with the eEurope action plan.

Jan 1, 2003

By P. Syrjänen, Lovén. P.

Because geostatistics together with block modeling has not been studied in detail before in the rock mechanics, a two-year research program to investigate the practical use of geotechnical modeling was started in Finland in 1999. According to research work results block modeling gives good estimate of overall rock mass quality but it can not identify individual structures like faults and narrow weakness zones. Weakness zones and faults should be mapped from drill cores, surface mapping, geophysical methods etc. and manually generate 3-D structural model. Rock mechanical 3-D modeling can be used for preliminary stope dimensioning and preliminary reinforcement design. Detailed design needs rock quality mapping from drifts during excavation work. La géostatistique associée à la modélisation par blocs n'ayant pas été étudiée en détail jusqu'à présent dans la mécanique des roches, un programme de recherche sur deux ans visant à examiner l'utilisation pratique de la modélisation géotechnique a été lancé en Finlande en 1999. D'après les résultats des travaux de recherche, la modélisation par blocs donne une bonne estimation de la qualité générale de la masse rocheuse mais elle ne permet pas d'identifier les structures individuelles comme les failles et les zones géologiquement dégradées étroites. Ces zones et failles devraient être cartographiées à partir de carottes de sondages, d'une cartographie de surface, de méthodes géophysiques, etc. et générer manuellement un modèle de structure 3D. La modélisation mécanique des roches en 3D peut être utilisée pour un dimensionnement de la chambre et un plan d'armature préliminaires. Un plan détaillé nécessite l'élaboration d'une cartographie de la qualité des roches des galeries lors des travaux d'excavation. Da man früher Geostatik und Block-Modellieren in der Gebirgsmechanik nicht detailliert untersuchte, wurde 1999 in Finnland ein zweijähriges Untersuchungsprogramm in Angriff genommen. Aufgrund der Untersuchungsergebnisse ergibt das Block-Modellieren eine gute Beurteilung der gesamten Gebirgsmassenqualität, kann jedoch einzelne Strukturen wie Verwerfungen und kleine Schwachzonen nicht identifizieren. Schwachzonen und Verwerfungen müssen demnach aus Bohrkernen, oder mit Hilfe von Oberflächenkartierung, geophysischen Verfahren usw. ermittelt und danach ein 3-D-Strukturmodell manuell erstellt werden. Felsmechanisches 3-D-Modellieren ist für die vorbereitende Abbaudimensionierung und für die vorbereitende Bewehrungsplanung verwendbar. Ein detaillierter Entwurf benötigt die Kartierung der Gesteinsqualität aus den Gesteinsstrecken während der Ausbrucharbeiten.

Jan 1, 2003

By V. N. Medvedev, A. M. Bryukhanov

Stationary mine air control equipment enables monitoring of CH4 concentration only in sensor locations. CMC-4 individual indicator built into a caplight has been developed in Ukraine, extending CH4 monitoring to manned job sites. Major technical characteristics of the indicator are demonstrated. It features two operation thresholds: 1st threshold 1.0 to 2.0% vol. 2nd threshold 1.5 to 2.5% vol. Basic absolute accuracy ± 0.2% Caplight battery is a common power supply for the lamp and CH4 indicator, providing at least 10 hours of the system non-stop operation. Average pre-failure life is at least 10,000 hrs. It features: an explosion proof design and intrinsically safe test circuit; a small-sized sensor as an integral part of the caplight; a hybrid microcircuit to facilitate functioning of methane monitoring unit. The CMC-4 indicator weight is the weight of the caplight itself and equals 2.4 kg. A two-threshold design makes possible to distinguish between methane sources: slow accumulation due to diffusion or sudden rushes due to a gas-dynamic event. CMC-4 indicators in addition to stationary equipment minimize the risk of CH4 explosion underground determined as a product of accident intensity by calculated time interval.

Jan 1, 2003

By J. Cygankiewicz

Efficient prevention of mine fires is impossible without predicting the self heating processes in the given geological and mining conditions. The respective forecasting method is presented in this paper based on the following assumptions: - factor deciding on fire hazard in the underground workings is the process of heating of coal from the primary rock temperature to the critical temperature when the heating rate growth rapidly - another important factor is the fire incubation time defined as time needed to achieve the critical temperature. This time is determined by balance of heat and mass in the heated coal - contact of crushed coal with oxygen in air cause some exothermic processes as : physical and chemical sorption of oxygen , oxidation reaction and evaporation of humidity Heated coal transfers its thermal energy to the environment by conductivity to the rocks and by convection to the flowing gases. The heating is possible if thermal energy generated from coal is greater then the share transferred to the environment. The paper presents the laboratory method of measurement of heat generation in adiabatic conditions. Also the mathematical model with examples of computation enabling to forecast the self heating process of crushed coal is presented.

Jan 1, 2003

By J. E. Quintanilha de Menezes, L. Ribeiro e Sousa, I. Ferreira

The Paradela dam has a spillway that makes it possible to discharge a maximum flow of 400 m3/s, the water discharges being on the river Sela, about 2km upstream the river Cávado. After the first use of the spillway, some landslides have occurred on the right bank of the river Sela as a result of the erosion generated on its base about one hundred meters near some houses of a small village. This paper presents a study performed for the slope stability where finite element results are taken into account. A monitoring program was established that essentially consisted of measuring sub-horizontal displacements in points located in boreholes at different depths and also phreatic levels. Some monitoring results are presented. Le barrage de Paradela a une décharge d’eau avec un débit maximal de 400 m3/s sur le fleuve Sela dans un endroit situé environ 2km sur l'amont du fleuve Cávado. Après la première utilisation de cette décharge, quelques glissements se sont vérifiés sur le versant droit du fleuve Sela résultant de l’érosion générée sur sa base dans une zone à 100 mètres de quelques maisons d’un petit village. Ce travail présente une étude réalisée concernant la stabilité du versant avec la considération des résultats des éléments finis. Un programme d’auscultation a été mis en place pour mesurer les déplacements sub-horizontales sur des points situés en forages à des différentes profondeurs. Quelques résultats de cette monitorization sont présentés. Der Ueberlauf des Padela Dammes ermoeglicht das Ablassen einer max. Wassermenge on 400 m3/s in den Sela Fluss, ca. 2 km flussaufwaerts des Cávado Flusses. Nach Inbetriebnahme des Ueberlaufes traten in ca. hundert Meter Entfernung zur Wohnbebauung eine Dorfes Erdrutschungen am rechten Ufer des Sela Flusses auf, die auf Erosionen am Flussbett zurückzuführen waren. In der vorliegenden Studie wurde die Boeschungsstabilitaet unter Beruecksichtigung von Berechnungsergebnissen der Finiten Element Methode untersucht. Es wurde ein essprogramm ausgearbeiten, das im Wesentlichen auf Messungen der Untergrundverformungen in verschiedenen Bohrlochteufen sowie auf Grundwassermessungen beruht. Im Folgenden sind einige Messergebnisse dargestellt.

Jan 1, 2003

By T. S. Golosinski

The paper reviews current status of online education related to mining, and reports on the online Master of Engineering programme in Mining Engineering that is offered at the University of Missouri-Rolla since 2001. Keywords: Online education, learning, teaching, mining engineering, mining education online

Jan 1, 2003

By M. J. Sapko

The Pittsburgh Research Laboratory (PRL) of the National Institute for Occupational Safety and Health (NIOSH) recently conducted full-scale explosion experiments; these experiments evaluated the strength characteristics of various seal designs used for safely isolating worked-out areas in underground coal mines. Large-scale explosion tests were conducted within the multiple entry section of PRL's Lake Lynn Experimental Mine (LLEM) employing the only currently accepted test method endorsed by the Mine Safety and Health Administration (MSHA) for seal design in American mines. These explosion tests are labor-intensive, expensive to conduct, and can interfere with other critical underground safety and health research programs conducted by NIOSH. Therefore, the PRL has developed an alternative seal evaluation method, based on a hydrostatic pressure loading concept, that can facilitate the in-situ testing of seals in an operating mine. Two chambers within LLEM and one within the Safety Research Coal Mine (SRCM) were used for hydrostatic pressure loading various seal designs. The results from tests in these chambers compare favorably with those from the large-scale explosion tests in the multiple entries. Preliminary size-scaling relationships for predicting the strength of standard seal designs as a function of entry size is also presented. In addition to testing seal designs at the required 20 psi static pressure level, the new facilities also allow for the determination of the seal's ultimate failure pressure. This new approach shows promise as an alternative evaluation method for improving mine sealing technologies which, in turn, will enhance the safety of the underground personnel.

Jan 1, 2003

To the members of The South African Institute of Mining and Metallurgy We have audited the annual financial statements of The South African Institute of Mining and Metallurgy set out on pages 451 to 460 for the year ended 30 June 2002. These financial statements are the responsibility of the Institute?s Council. Our responsibility is to express an opinion on these financial statements based on our audit. Scope We have conducted our audit in accordance with statements of South African Auditing Standards. Those standards require that we plan and perform the audit to obtain reasonable assurance that the financial statements are free of material misstatement. An audit includes: ?examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements, ?assessing the accounting principles used and significant estimates made by management, and ?evaluating the overall financial statement presentation. We believe that our audit provides a reasonable basis for our opinion. Audit opinion In our opinion, the financial statements fairly present, in all material respects, the financial position of the Institute at 30 June 2003 and the results of its operations and cash flows for the year then ended in accordance with South African Statements of Generally Accepted Accounting Practice. Auditors 29 July 2003 Council?s approval of the annual financial statements The annual financial statements for the year ended 30 June 2003 set out on page 451 to 460 were approved by the Council on 26 July 2002 and are signed on its behalf by:

Jan 1, 2003

The nature of metallurgical engineering?applying and optimising chemical and physical processing of ores into useful materials?is reviewed. Important trends that shape the context in which metallurgical engineers practise are identified ? increased global production of primary metals, declining prices, environmental constraints, and increased property requirements of materials. A successful department of metallurgical engineering is one which employs a team of academic leaders to develop graduate engineers who are productive across the full range of metallurgical processing. Keywords: metallurgical engineering, primary metals, commodity prices, processing

Jan 1, 2003

By J. Wills

The use of drilling rigs to increasingly mechanize stope drilling has been acknowledged as important for the S.A. mining industry in it ís efforts to tackle the challenges of low productivity, AIDS and an ageing driller workforce. The spin-offs of increased safety, cost-effectiveness and better mining performance provide advantages to all?from the driller to the shareholder. However, implementation or product rollout has varied from outright success to dismal failure. A study of various cases by Novatek and Anglogold TDS showed clear reasons for these differences. Whereas the successes were characterized by clear objectives, accountability, user buy-in, a commitment to make the technology work and no-nonsense reporting, these were typically absent in failed implementations. The attitude at unsuccessful mines was to ?trial? the equipment?even subconsciously, a ?trial? is a test where failure becomes an acceptable outcome. During the study it became clear that mining management are not adequately trained to manage the often-tricky rollout process. They are often also not empowered or clearly mandated to deal with the organizational, human and technical issues that must dovetail to create a success. The output of the study was to develop a basic rollout process that could be used to formally manage the implementation of new drilling technology. Creating an alignment between the mine, workforce and supplier promotes a win-win situation that will not otherwise spontaneously arise.

Jan 1, 2002

By G. M. J. van Heerden

Paper written on project work carried out in partial fulfilment of B. Eng (Mining Engineering) degree The Union Section of Anglo Platinum is situated ±18 km west of the town of Northam on the north-western rim of the Bushveld Igneous Complex. Both the Merensky and UG2 reefs are mined. Support of the Merensky stoping areas with rock bolts is specifically problematic due to the stoping width restrictions varying around 90 cm. The installation equipment of in-stope rock bolts and the effectiveness thereof in the Merensky stoping areas was critically evaluated. In order to do this a background research on the need for better on-the-face support had to be conducted. The need for improving the rock bolt drilling and the equipment had to be investigated and the financial implications and justifications for the improved equipment examined. To conduct the search an overall study was done on the rockfalls and safety aspects throughout the platinum industry in South Africa and specifically Union Section. It was found that most of the rock falls in the Merensky stoping areas of which ± 70% are less than 1.2 m in thickness generally occurs within 4 m from the face and causes ± 60% of the in-stope injuries. Serious shortcomings had been identified with respect to the airleg, rock drill machine and the drill steels used in the drilling of the rock bolt holes. Through experimentation, using a testing frame built for this purpose on surface and with the co-operation of mine staff and suppliers, a number of possible modifications were identified and tested. This resulted in the final product with which it was possible to drill a 1.2 m hole in the hangingwall of the stopes ranging with an angle to the hanging from 90° for a 90 cm stoping width and 67° for a 80 cm stoping width. It is confidently concluded that this system will effectively improve the total face support and result in a substantial reduction of rock falls and consequently the occurrence of injuries and fatalities in the Merensky stoping areas. The installation of rock bolts on the face with the modified drilling equipment will increase the direct support, but the system has a potential of a substantial reduction in the profile stick support density and an increase in productivity in the stoping areas due to fewer occurrences of rock falls. It was finally concluded that effective modifications to the drilling equipment for rock bolt in-hole drilling could be made and the installation thereof in the stope face is adequately justified.

Jan 1, 2002

By M. D. Mwema

Copper oxide ores deposits in the Katanga province of the Democratic Republic of Congo (DRC) contain at variable level cobalt oxide minerals. In contrast to copper oxide minerals which readily dissolve in the sulphuric acid solution, the cobalt oxide bearings are difficult to dissolve, especially if cobalt is present in the third oxidation state (Co2O3). This species become soluble after reduction of Co+3in Co+2. In practice, the use of reducing agent is therefore necessary in order to transform the insoluble minerals into soluble cobalt sulphate species. The following reducing agents are currently used at the Shituru plant: ferrous ions, which are present in leach solutions, pulverised copper or sodium meta bisulphite (MBS). Due to the high consumption of reducing agents (0,8 t MBS/t of solubilized Co; 1,2 t Cu/t-Co), cobalt production is expensive. The use of sulphur dioxide as reducing agent was then investigated in order to reduce operating cost. This reagent also presents the advantage of sulphuric acid production during the leaching process. It has been added in the leaching vessel (tank). From the laboratory and industrial tests, selective leaching of cobalt (78%) has been performed. The cobalt leaching kinetic depend on sulphur dioxide dosage. Dissolution of copper, iron and manganese remained very low. No emanation of SO2 gas was observed during the process.

Jan 1, 2002