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By S. Pathak, B. Nilsen

Abstract: In recent years, probabilistic approach with the calculation of probability of failure instead of a factor of safety against failure is emerging in practice. The main objective of the paper is to discuss a probabilistic approach in rock slope stability analysis for Himalayan conditions. Due to the fragile geology brought about by the tectonic movements along the hill slopes, dramatic variations of the topography and intensive surface runoff during every monsoon season, serious slope failures occur frequently in Himalayan region. Slope failures have also been triggered by seismic activities. The probabilistic approach is applied to stability analysis for a road cut along the Desander back slope of the Kali Gandaki hydropower project in Nepal. It is concluded that the probability approach offers a more accurate grasp of the actual condition than any factor of safety. Zusammenfassung: In den letzten Jahren ist es mehr gewöhnlich geworden, ein stochastisches Verfahren und eine Berechnung von der Wahrscheinlichkeit eines Zusammenbruchs statt einer Berechnung von Sicherheitsfaktoren zu verwenden. Das Hauptziel dieses Artikels ist das stochastische Verfahren in Stabilitätsanalyse von Gebirghängen, welches an Himalayische Verhältnisse angewandt worden ist, zu diskutieren. Wegen der spröden Geologie die durch tektonische Bewegungen entstanden ist und den dramatischen topographischen Variationen sowie viel Oberflächenwasser während des Monsuns, kommen in der Region des Himalayas oft mehrere erhebliche Abhangszusammenbrüche vor. Abhangszusammenbruche ist auch von seismische Aktivität ausgelöst worden. Das stochastisches Verfahren ist auch benutzt worden, um die Stabilität von einem Wegschnitt in dem Desander Gebiet von dem Kali Gandaki Wasserwerk-Projekt zu analysieren. Die schlussfolgerung ist, dass die Ergebnisse eines stochastisches Verfahren die wirkliche Verhältnisse eines Abhangs besser beschreibt als der Sicherheitsfaktor. Résumé:- Ces dernières années, une approche probabiliste basée sur le calcul d’une probabilité de cassure au lieu d’un facteur de sécurité préventif d’une cassure est de plus en plus utilisée. L’objectif principal de ce papier est de discuter une approche probabiliste de la stabilité de versants rocheux en himalaya. Due à la fragile géologie causée par les mouvements tectoniques sur les versants de collines, aux dramatiques variations de topographie, ainsi qu’au lessivage intense du relief à chaque mousson, de sérieux glissements de terrains se produisent fréquemment en Himalaya. Les glissements de terrain sont aussi déclenchés par l’activité sismique. Cette approche probabiliste est appliquée aux analyses de stabilité d’une section de route le long du versant arrière Desander du projet « hydropower » du Kali Gandaki au Népal. On en conclut que l’approche probabiliste offre une estimation plus précise des conditions actuelles que n’importe quel facteur de sécurité.

Jan 1, 2003

By D. -H. Park, G. -j. Kim, Y. -J. Park, C. -S. Hong, S. -Y. Choo

To evaluate the quantitative tunnel behavior influenced by characteristics of discontinuity, this pa-per executes the parametric study using 2 and 3-dimensional DEM analysis. First of all, this study finds that displacement and the stress of shortcrete are proportioned to frequency of joint and rockbolt axial force is adversely proportioned too. Secondly, it is found that the most sensitive in-put parameter used in Barton-Bandis(BB) model is residual friction angle. Finally, when joint sets are encountered at tunnel excavation face, to identify the most critical joint orientation is very crucial for a stability of tunnel. La thèse a pour but d’étudier les influences sur la stabilité du tunnel, au niveau du réseau de la discontinuité et de la valeur de sa nature aquis par le projet récemment exécuté en vue de mener à l’analyse quantitative de cette stabilité, en appliquant chaque différent paramètre comme la fréquence de diaclase, la constante de résistance des modèles de Barton-Bandis(BB) ainsi que la relation entre le sens d’excavation du tunnel et le réseau de diaclase en 3 dimensions. En fait, cette étude nous a montré que la fréquence de diaclase s’accroît proportionnellement au déplacement et à la contrainte du béton projeté. L’angle de friction résiduel s’est montré le plus sensible à la stabilité du tunnel parmi les modèles de BB. Aussi à travers l’analyse à 3 dimensions, il s’est vérifié que si l’angle de pente du groupe de diaclase est horizontal entre l’axe du tunnel et la direction, il donne une influence importante sur le comportement du tunnel. En particulier, l’influence était la plus importante sur un fond rocheux dont la diaclase horizontale est grande. Um das quantitative Verhalten des Tunnels zu bewerten, eroertert dieses Papier eine parametrische Studie mit Hilfe der DEM Analyse. Auch wird hier eine zweidimensionale Analyse von Ver-bindungen verschiedener Frequenzen in der Gesteinsmasse, eine sensitive Analyse von allen der im Barton-Bandis-Modell (BB) genutzten Parameter und eine Dreidimensional-Analyse mit ver-schiedenen dreidimensionalen geometrischen Veteilungen von Verbindungen ausgefuehrt. Erstens: Die Studie findet heraus, dass Vedraengung und Druck im Shortcrete proportional zur Frequenz von Verbindungen und Axialkraft der Steinbolzen antiproportinal ist. Zweitens: Es wird herausge-funden, dass die am meisten Sensitiven der im BB-Modell angewendeten Eingaben die am Ende uebriggebliebenen Reibungswinkel sind. Und schliesslich wird herausgefunden, dass wenn Ver-bindungsteile an der Tunnelaushoelungsoberflaeche ausgemacht werden, fuer die Tunnelstabiltaet die Identifikation der meist kritischen Verbindungsorientierung sehr bedeutungsvoll.

Jan 1, 2003

By G. du T. Judeel

An investigation was carried out to determine whether a numerical model could be constructed that would produce results that realistically represent actual ground deformations in and around a vertical shaft. The ground deformation was brought about by the partial extraction of the shaft pillar. A special characteristic of the rock masses, affected by the shaft pillar extraction, was that the shaft was located in poor quality rock masses. After the extraction of a portion of the shaft pillar, excessive deformations occurred at the shaft/reef intersection. Therefore, a decision was taken to extract the entire shaft pillar protecting the shaft by a proposed waste-cut across the shaft. The effects of stress and displacement on the shaft were investigated by using inelastic numerical modelling in different stages. A calibrated numerical model was constructed producing modelled results comparable to the actual displacements along the shaft. Des recherches ont été poursuivies pour déterminer si on pouvait construire un modèle numérique qui donnerait des résultats représentant avec réalisme les déformations réelles du terrain à l’intérieur et autour d’un puits vertical. La déformation du terrain était entraînée par l’extraction partielle du massif de protection. Une caractéristique spéciale des masses rocheuses, affectées par l’extraction du massif de protection, était que le puits était situé dans des masses rocheuses de qualité inférieure. Après l’extraction d’une portion du massif de protection, des déformations excessives se sont produites à l’intersection du puits avec le filon. Par conséquent, la décision a été prise d’extraire le massif de protection en entier par une coupe de déblais à travers le puits. Les effets de contraintes et décalage furent étudiés en utilisant une modélisation numérique inélastique à des stages différents. Un modèle numérique calibré fut construit, donnant des résultats modelés comparables aux décalages réels le long du puits. Eine Untersuchung wurde durchgeführt um festzustellen, ob ein numerisches Modell konstruiert werden könnte, das Resultate produzieren würde, welche realistisch aktuelle Bodendeformationen in und um einen vertikale Schacht darstellen. Die Bodendeformation resultierte teilweise aus der Extraktion des Schachtpfeiler. Eine spezielle Eigenschaft der Gesteinsmassen, beeinflußt durch die Schachtpfeilerextraktion, war, daß der Schacht in Gesteinsmassen geringer Qualität situiert war. Nach der Extraktion eines Teils der Schachtpfeiler, traten übermäßige Deformationen am Schacht/Riff Kreuzungspunkt auf. Folglich wurde die Entscheidung getroffen, die gesamten Schachtpfosten zu extrahieren und den Schacht mittels eines geplanten Verlustschnittes quer zum Schacht zu schützen. Die Auswirkungen des Druckes und der Versetzung auf den Schacht wurden unter Anwendung unelastischer numerischer Modelle in unterschiedlichen Stadien untersucht. Ein kalibriertes numerisches Modell wurde konstruiert, welches berechenete Ergebnisse mit den tatsächlichen Versetzungen entlang des Schachtes vergleicht.

Jan 1, 2003

By K. Eckert, A. E. Sommer, S. Heitkam

One highly relevant challenge in flotation is the recovery of fine particles. Due to their low inertia, these particles are mostly pushed aside by rising bubbles. Consequently, they typically exhibit low probability for bubble-particle collision and thus, a poor recovery rate. In this work, the trajectories of fine particles in the vicinity of rising bubbles were investigated. The measurements considered a chain of millimetric bubbles in a rectangular container filled with deionized water. The flow field near the bubbles was measured by tomographic particle image velocimetry (TPIV), employing fluorescent tracer particles of 33μm diameter. Subsequently, trajectories of larger particles and bubble-particle collision events are recorded with 4D particle tracking velocimetry using a high temporal and spatial resolution. The results reproduce the well-known collision of particles on the leading edge of a rising bubble. Additionally, collisions on the tailing edge were observed in cases with a low Stokes number. The TPIV results demonstrate, that the high turbulent kinetic energy in the bubble wake allows particles to divert from the fluid streamlines and collide with the tailing edge of the bubble. The tailing edge collision probability increases with the bubble Reynolds number and decreased particle inertia. Overall, the investigation shows that the collision of fine particles in the bubble wake should be considered for the development of further collision probability models. Furthermore, the importance of turbulence on the fine particle flotation was demonstrated. Keywords: 4D Particle tracking velocimetry (PTV), tomographic particle image velocimetry (TPIV), fine particle flotation, collision probability, bubble-particle interaction, wake induced collision

Jan 1, 2020

Discussion of the previous paper E. N. H. MOLLOY The first 22-foot-diameter Aerofall mill was installed at Mangula in 1957. This was fitted with cast-iron trunnion'! located to the mill shell with 2-inch-diameter mild-steel bolts. O.F .S. Branch Minutes of the General Meeting held at the Welkom Club on Wednesday, 2nd June, 1976, at 4.00 p.m. Mr G. J. C. Young (Chairman of the O.F.S. Branch) was in the Chair. Also present were:

Jan 9, 1976

By J. D. Koch

A 'project' is defined here as a process in which an idea is developed from its inception until either it is discarded or the product of the idea has been accepted by the ultimate user. The phases in a project, particularly the early phases, are examined, and project organization is described and contrasted with a functional line-management type of organization. Emphasis is placed on comprehensive definition, which is vitally important to the achievement of the goals of time, cost, and quality set for a project.

Jan 1, 1981

The first commercial Corex Plant in the world capable of producing liquid iron from a variety of low-grade coals was commissioned in 1990 by Iscor at its Pretoria Works. The Plant has an annual production capacity of 300 kt of liquid iron. Because the compulsory use of coke is eliminated, the new method offers an economic and revolutionary alternative to liquid-iron production. Coke used in traditional blastfurnaces is manufactured from high-grade coal of which the available sources in South Africa are limited.

Jan 1, 1991

By A. W. Bryson

Electrolytic precipitation of ammonium diuranate by A. W. BRYSON. Ph.D. (Member) Continuous precipitation of ammonium diuranate from a solution of uranyl sulphate and ammonium sulphate in the cathode compartment of an electrolytic cell has been investigated. It is found that the rate of precipitation and the settling rate of the precipitate can be correlated with the current consumed per unit volume of catholyte solution. The weight fraction of uranium in the dried solid product appears to be constant over the range of operating conditions used.

Jan 9, 1975

By H. H. Bird

The crux of reliable estimates of ore reserves lies in a comprehension of the related geological events and their controls on the formation and distribution of the economic mineralization, and on the rock types, lithology, and structures. Furthermore, mine geometry is based on the shape of the ore body, the types and distribution of the economic minerals, and the ground conditions. Asian mining The Institution of Mining and Metallurgy has been invited to organize an international conference on the occasion of the Asian mining 81 international exhibition.

Jan 1, 1980

By A. O. Filmer

A study of the dissolution of gold from a pyrite concentrate and from various calcines is reported. The percentage extraction of gold was found to decrease with increasing sulphur content in the material leached because of the porosity of the materials, and particularly because of the passivation of the anodic dissolution of gold when the gold was In contact with other conducting minerals. This is explained in terms of the current-potential curves for the oxidation of gold and the reduction of dissolved oxygen.

Jan 1, 1982

By B. Gilbertson

This paper presents a method that enables one to estimate the risk-adjusted discount rate. that should be used In project discounted cash-flow analysis. The risk-adjustment process is carried out via the capital asset pricing model of modern finance theory, in which the appropriate measure of risk is the beta coefficient of the project concerned. The resulting discount rate thus depends on the properties of the project Itself, and not on the nature or cost of the capital of the firm considering the investment.

Jan 1, 1980

By D. G. Hulbert, D. Tudors, M. L. Coetzee, I. K. Craig

The paper describes how a multivariable control scheme was developed and implemented for the run-of-mine milling circuit at a gold mine belonging to Vaal Reefs Exploration & Mining Company Limited. The key variables that are controlled are slurry level in the sump, mass of material in the mil, and product size. The control scheme has resulted in reliable control of the dynamics of the plant, and has provided a good basis for the optimization of plant operation by the selection of suitable set Points.

Jan 1, 1990

By A. C. Lawrence, B. Econ, D. Com

The importance of human factors in mining productivity by A. C. Lawrence, D. Corn., B. Econ. (Member) The paper outlines some of the views on the relationship between work attitudes and performance, and examines evidence derived from relevant research done in the mining industry. It is suggested that higher productivity within any given system of mining can be attained if attention is paid to the four factors that represent the CORE of human work performance: Competence, Opportunity (or Organisation), Recognition (or Rewards), and Expectations (or Enrichment).

Jan 7, 1974

By C. A. Cousins

Platinoids in the Witwatersrand system C. A. Cousins. (visitor) Study of the composition, nature and mode of occurrence of platinoid minerals in the conglomerates of the Witwatersrand System leads to some interesting conclusions. Genetic evidence strongly favours a placer origin, while comparison with modern alluvial platinoids supports this view but also indicates that they are very mature alluvials. The compositional patterns and distribution of the platinoids in the Witwatersrand basin suggest the water was saline. Study of the mineralogy was greatly facilitated by the electron-probe.

By E. L. Atkinson, G. W. Leach

The paper discusses the reasons for the introduction of load-haul-dump (LHD) units into Greenside Colliery, and the circumstances leading to the replacement of conventional mechanized equipment on a trial basis in the mining operations on No. 2, 4, and 5 seams. An outline is given of the factors governing the selection and introduction of these units into coal mining, and the associated mining and engineering aspects involved in the optimization of their use. Operating statistics comparing the performance of conventional and LHD equipment are included.

Jan 1, 1979

By W. Wittke, D. Schröder, H. Polczyk

ABSTRACT: The Urft dam, the Diemel dam and the Eder dam are three old masonry damslocated in Germany. The paper describes the rehabilitation measures and the correspondingstability analyses carried out to adjust the dams to today's standards. Remedial works such as theexcavation of inspection galleries, the installation of a grout curtain with a downstream drainagescreen as well as the installation of pre-stressed permanent tendons were carried out. In all threecases the stability of the upgraded dam could be proven on the basis of finite element analyses. ZUSAMMENFASSUNG: Die Urft-, Diemel- und Edertalsperre sind drei alte deutscheSchwergewichtsmauern aus Bruchsteinmauerwerk. Im Beitrag werden Instandsetzungsmaß-nahmen und Standsicherheitsnachweise beschrieben, die erforderlich waren, um die Staumauernan den heutigen Stand der Technik anzupassen. Hierzu wurden Kontrollgänge aufgefahren,Dichtungsschleier mit luftseitiger Dränage sowie vorgespannte Daueranker hergestellt. In allendrei Fällen konnte unter Berücksichtigung der Instandsetzungsmaßnahmen die Standsicherheit derMauer auf der Grundlage von Berechnungen nach der Methode der finiten Elemente nachgewiesenwerden. RÉSUMÉ: Les barrages de Urft, Diemel et Eder sont trois barrages-poids vieux allemandsconstruit de maçonnerie de moellon. Dans cet article, opérations de remise en état et preuves destabilité sont décrits, qui étaient nécessaires pour adapter les barrages à l'état de la techniqueactuelle. À cet effet, des galeries de contrôle étaient creusés, voiles d'étanchéité avec des drains àla face aval et tirants précontraints permanents étaient fabriqués. Dans tous les trois cas, tenantcompte des opérations de remise en état, la stabilité de la barrage pouvait être prouvée à partir decalculs selon la méthode des éléments finis.

Jan 1, 2003

Abstract A new approach is introduced for study of the behaviour of geotechnical strength parameter prior to slope analysis to ascertain whether strength parameters of slope materials are homogenous or heterogeneous at different mine depths. The strength parameters used for the study are uniaxial compressive strength, tensile strength and shear strength. The analysis is based on statistical analysis of variance technique for one-way classification. The application of the technique is given through a case study in an openpit mine. Auszug Eine neue Annäherung wird für Studie des Verhaltens des geotechnischen Stärke Parameters vor Steigunganalyse eingeführt, um zu ermitteln, ob Stärke Parameter der Steigungmaterialien homogenous oder an den unterschiedlichen Grube Tiefen heterogen sind. Die Stärke Parameter, die für die Studie verwendet werden, sind einachsige zusammenpressende Stärke, Dehnfestigkeit und Scherstärke. Die Analyse basiert auf statistischem varianzanalytische Technik für Einwegklassifikation. Die Anwendung der Technik wird durch eine Fallstudie in einer openpit Grube gegeben. Abstrait Une nouvelle approche est présentée pour l'étude du comportement du paramètre géotechnique de force avant l'analyse de pente pour établir si les paramètres de force des matériaux de pente sont homogenous ou hétérogènes à différentes profondeurs de mine. Les paramètres de force utilisés pour l'étude sont résistance à la pression uniaxiale, résistance à la traction et résistance au cisaillement. L'analyse est basée sur statistique la technique de l'analyse de variance pour la classification à sens unique. L'application de la technique est donnée par une étude de cas dans une mine à ciel ouvert.

Jan 1, 2003

By M. Kilfoil

Many minerals processing operations result in crushed rock being mixed with a liquid. Sometimes, the rock particles have to be dried before the next process begins and there may be a considerable distance between the equipment carrying out these processes. Bateman Engineered Technologies (BET) developed, patented and commercialized a method of simultaneous pneumatic conveying and drying. A joint project to assist with optimizing the process is under-way. Part of it is a numerical simulation of the process. The simulation is done using a dedicated program written in MATLAB, (commercial software which is widely used in engineering). It accounts for heat and mass transfer as well as particle transport. The main part of the program consists of a loop containing a series of equations which are evaluated sequentially. During any particular iteration, the properties are changed one at a time. Since the properties are changing relatively slowly, this method gives good results. The outputs of the simulation are consistent with the operational experience of BET’s engineers. The output is very comprehensive and all numerical. Since the program is currently being used for research purposes, flexibility is very important. Thus the output is converted into a spreadsheet file. Variations in the output quantities are displayed graphically using MS Excel. Some simulation could have been done using computational fluid dynamics (CFD) software. The advantages and disadvantages (technical, financial and skills requirements) of the two approaches for this particular type of simulation are compared briefly. Keywords: Pneumatic conveying, Heat and mass transfer, Computer model

Jan 1, 2003

This paper examines manning best practice in the Australian mining industry, comparing the mining of gold with mining of other commodities. In particular, the paper considers a range of mining operations and their manning levels as measured by operational benchmarking. The benchmarking results presented cover 7 open pit and 14 underground studies of gold mines in Australia from a database of over 50 studies. The data were collected as part of AMC?s benchmarking and operational improvement studies conducted between 1999 and 2009. The results examine overall manning levels in mining, processing and administration functions. Manning levels for a range of mining methods, including open pit and underground methods, are segmented. Productivity measures such as ore tonnes per man day and metres developed per man day are presented and where direct relationships can be established, the relationships are described. The proportion of supervisory to operations personnel and labour costs as a percentage of total operating costs is highlighted. Minimum manning requirements for the range of mining methods are indicated, irrespective of the size of the operation. The benchmarking results provide guidance by indicating a range of manning numbers and trends which are likely to be appropriate for the scale and type for a range of mining operations. When combined with benchmarked productivity and cost data, manning results help identify potential areas for business improvement, driving gains in the efficiency of labour. Finally, the paper considers perspectives on best practice for manning and the limitations in application of this type of analysis in a global context.

Jan 1, 2009

What is the role of The South African Institute of Mining and Metallurgy at a time when so much is developing and changing in South Africa? The minerals industry is represented through employers, employees, government, education, research, public views, and even pure political interests. The role of the Institute is to represent the mining and metallurgical profession. In this role the Institute has aligned itself with Associated Scientific and Technical Societies, the Council of Scientific Societies and the Engineering Association. The Institute is also active on the Engineering Council of South Africa.

Jan 1, 1996