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By E. V. Lilford

A number of countries have introduced codes governing the valuation of mineral assets and securities. The African continent will follow suit in due course considering the importance of the global minerals industry as it relates to the attraction of foreign investment. South Africa is to introduce the Petroleum and Minerals Development Bill legislating the involvement of previously disadvantaged individuals and communities in the country?s minerals industry. One of the challenges facing the successful implementation of such codes and bills lies with the abilities of independent valuators to value mineral properties and projects on a consistent basis. Certain valuation principles and methodologies are applicable in all jurisdictions in the minerals industry. These valuation tools and principles are considered and developed in this report. They have been discussed and developed to encourage minerals valuators to consider and consistently apply the most applicable valuation methodologies.

Jan 1, 2002

By A. E. Lewis

The emphasis of this paper is on the characterization and testing of the slag produced by a secondary lead refinery. This work forms part of a broader investigation aimed at reducing loss of valuable product from the process as well as minimizing the environmental impact of the process wastes. It was this work that led to a critical examination of the standard waste classification tests. Characterization of the slag was carried out using a number of complementary techniques. In the broader context, the slag characterization aided in identifying process deficiencies and thus was a critical tool in suggesting potential for process optimization. For this study, the slag characterization provided a relatively comprehensive picture of the composition and properties of the slag, which facilitated understanding the behaviour of the slag under batch test conditions. On the basis of quantity of hazardous components alone, the slag is hazardous according to South African Acceptable Risk Limits (ARL). However, when both the quantity and the leach potential of the hazardous components is taken into account, standard waste tests carried out by three independent agencies indicate that the slag should not be classified as hazardous according to local regulations. Also, according to United States Environmental Protection Agency (US EPA) limits, which are independent of the quantity of the waste, the slag would not be classified as hazardous. The standard waste tests used by the independent agencies was the Toxicity Characteristic Leach Procedure (TCLP), a test which was developed by the US EPA to classify hazardous wastes. One of the requirements of this batch test is that it should be quick, simple to carry out and that the results should be reproducible. Previously, the applicability of the TCLP test to mineral processing and metallurgical wastes has been challenged on a number of points. Additional testing of the slag was carried out using both the TCLP and the Synthetic Precipitation Leach Procedure (SPLP) recommended by the American National Mining Association as being more appropriate for mineral processing wastes. The particular physical and chemical characteristics of the secondary lead slag highlighted additional limitations of both the TCLP and SPLP tests as standard laboratory batch procedures. Keywords: environmental protection, secondary lead processing, slag, leach testing, TCLP, SPLP, ARL, hazardous waste, batch tests

Jan 1, 2000

By J. Autio, H. Malmlund

The excavation damage zone (EDZ) caused by drill and blast excavation consists of intense damage adjacent to the remaining half barrel of the blast hole, new fracturing induced by the blast and reactivation of pre-existing fractures. The properties of intense microfracturing adjacent to the half barrels of remaining blast holes are based on study of rock samples from ZEDEX-tunnel and it’s extension at Äspö and the Research tunnel at Olkiluoto in Finland. The new and reactivated fracturing is based on results of mapping of slots cut in the rock in ZEDEX-project. The zone of increased porosity adjacent to half barrels, which penetrates to a depth of some centimeters was studied by using novel 14C-PMMA method. The penetration of the radial fractures, which is an order of magnitude deeper, was studied by mapping using color penetrant. Results of EDZ studies carried out at Äspö HRL in Sweden and in Research Tunnel at Olkiluoto show that the properties of EDZ can be affected significantly by engineering design. The result imply that the additional pore volume caused by distinct fracturing around the blast holes caused by state-of-the-art smooth blasting technique could be of the same order as that of the damaged zone adjacent to the surface of the half barrels. Durch Bohr- und Sprengarbeiten entstandene Eigenschaften der Auflockerungszone: Die durch Bohr- und Sprengarbeiten entstandene Auflockerungszone besteht aus einem großen, an das Resthalbrohr des Bohrloches angrenzenden Schaden, neuer Rissbildung und einer Reaktivierung der bereits existierenden Risse. Die Eigenschaften einer immensen, an die Halbrohre der Restbohrlöcher angrenzenden Mikrorissbildung beruhen auf einer Studie über die aus dem ZEDEX-Tunnel gewonnenen Gesteinsproben und deren Fortsetzung im Untertage-Labor Äspö (Hard Rock Laboratory, HRL) in Schweden und im Forschungstunnel bei Olkiluoto in Finnland. Die neue und reaktivierte Rissbildung basiert auf den Auswertungsergebnissen der Schlitze, die bei dem ZEDEX-Projekt ins Gestein geschnitten wurden. Die Zone der vermehrten, an die Halbrohre angrenzenden Porösität, die in ein paar Zentimeter Tiefe eindringt, wurde anhand der neuen 14C-PMMA-Methode untersucht. Das Eindringen der etwas tiefer gelegenen radialen Risse wurde anhand eines farbigen Eindringungsmittels untersucht. Die in Äspö und Olkiluoto durchgeführten EDZ-Studien zeigen, dass die EDZ-Eigenschaften wesentlich durch Engineering Design beeinflusst werden können. Das durch Bohrarbeiten verursachte Hohlraumvolumen der Rissbildung um den Tunnel herum ist ähnlich wie das Hohlraumvolumen der Bruchzone um die Bohrlöcher herum. Caractéristiques d’une zone endommagée par le creusement résultant d’un creusement par forage et dynamitage: La zone endommagée par le creusement résultant d’un creusement par forage et dynamitage présente un endommagement intense adjacent au demi-cylindre restant du trou de mine, une nouvelle fracturation et la réactivation des fractures préexistantes. Les caractéristiques de la microfracturation intense adjacente aux demi-cylindres des trous de mine restants reposent sur l’étude des échantillons de roche en provenance du tunnel ZEDEX et de son extension au laboratoire souterrain d’Äspö (« Hard Rock Laboratory » ou HRL) en Suède et du tunnel de recherche d’Olkiluoto en Finlande. La fracturation nouvelle et réactivée repose sur les résultats du placement des rainures sur la roche dans le projet ZEDEX. La zone de porosité accrue adjacente aux demi-cylindres et pénétrant à une profondeur de quelques centimètres à fait l’objet d’études recourant à la nouvelle méthode 14C-PMMA. La pénétration des fractures radiales, considérablement plus profondes, a été étudiée par placement en utilisant un agent pénétrant coloré. Les résultats des études EDZ effectuées à Äspö et à Olkiluoto montrent que les caractéristiques de l’EDZ sont susceptibles d’être affectées de manière significative par la conception technique. Le volume vide de fracturation résultant du dynamitage autour du tunnel est du même ordre que celui de la zone concassée autour des trous de mine.service.

Jan 1, 2003

By L. Lehasa

The purpose of the project was to investigate the challenges faced by Khutala Colliery pertaining to underground road construction and maintenance. Furthermore the influence of these challenges on productivity and safety requirements were taken into consideration. The operating standards required for the construction and maintenance of the 2 seam road transport infrastructure was investigated, together with reasons why the standards of operating procedure are not met. The Code of Practice put in place by Khutala Colliery was used to view the standard operating procedures. Leading practices on underground road construction were researched. The project aims to discover the gaps that Khutala Colliery must bridge to implement enhanced practices with regards to underground road construction. During the period of study, observations were carried out to determine whether the road construction standards of operating procedure were being adhered to at all times for both road construction and road maintenance. Khutala Colliery has put in place a traffic management plan, which includes safety practices and work policies that must be adhered to while travelling on underground transport roads.

Jan 1, 2012

By T. J. Kolokoto

This paper is based on a project conducted at Khomanani 2 shaft, Anglo American Platinum Limited. The main objective was to find an alternative support element in stopes to address the falls of ground (FOG) problem experienced at this shaft. Literature review was the major method used in the investigations. Resin bolts or any 1.5 m in-stope roofbolts were considered. The shaft was making use of 0.9 m long friction bolts, and these could not prevent the FOG experienced. Observations indicated that the FOG resulted in fall-out thicknesses averaging to 1.1 m, which is greater than the supported length of the friction bolts. The implementation of 1.5 m long bolts was recommended as a result of the project. These bolts will be able to address the fall-out thickness and provide sufficient support resistance to mitigate FOG. The chosen support element will result in a relatively small increase in support costs.

Jan 1, 2013

By A. T. Haile

Detailed monitoring of the response of the rock mass between rockbolt reinforcement units subjected to a simulated seismic source has been successfully conducted. This work has shown the increase in amplification of the Peak Particle Velocity (PPV) with distance from a rock bolt unit, and, a minimum PPV for rockburst damage for the given site characteristics. This understanding, at this site, will allow the design of a suitable rock bolt spacing to prevent unravelling of the rock mass between the rock bolt units for a given level of seismicity. Or, alternatively, an estimation of the requirement for a suitable fabric support system, for the anticipated level of seismicity, can be made.

Jan 1, 2001

By J. F. Papp

In the United States, chromium has been consumed in three major markets: chemical, metallurgical, and refractory. The predominant end use for chromium in the United States is in the metallurgical market as an alloying element in the production of stainless steel. In addition to being a major stainless steel-producing country, the United States is a major world producer of chromium-containing chemicals and has used substantial amounts of chromite ore for refractory applications. Chromium use is not easily further subdivided within the chemical and refractory industries because there is insufficient publicly available information to do so; however, chromium use can be subdivided among metallurgical industry uses based on the American Iron and Steel Institute (AISI) reported shipments of stainless steel by market classification (agricultural, aircraft, automotive, etc.). It is the goal of this study to determine the distribution of U.S. chromium apparent consumption among major markets in the United States. The distribution is expressed in the form of dimensionless fractions that are computed based on documented chromium consumption by major market. The distribution of chromium among markets within the metallurgical market is computed in a similar manner. Distribution factors are first computed for the major markets, then for markets that are subdivisions of the metallurgical market. The distribution of chromium among major markets has changed substantially over the time period of analysis. The fraction of chromium consumed by the metallurgical market has increased while that of the chemical and refractory markets has declined. Within the metallurgical market, the service industry market accounts for the greatest fraction of chromium consumption followed by transportation. Electrical, machinery, and fabricated products markets account for a substantial share of the metallurgical chromium consumption.

Jan 1, 2004

By J. T. Jordaan

Paper written on project work carried out in partial fulfilment of B. Eng (Mining Engineering) degree This paper addresses the critical parameters that need to be considered when designing a mechanized bord-and-pillar mining layout for a narrow tabular steep dipping orebody. These parameters are : ?Reef dip ?Reef width ?Geological structures within the orebody ?Physical dimensions of the selection of machines ?Gradeability of the selection of machines. The main objective in designing such a layout is to maximize machine efficiencies whilst minimizing dilution. This methodology was then applied in the design of a mechanized bord-and-pillar mining layout for a given piece of ground (Vlakpoort and Moddergat) using a given selection of machines. This piece of ground contains the PGM bearing UG2 Reef with an average thickness of 124 cm and dipping at 18°withadverse strike and dip changes. Two bord-and-pillar layouts were designed for this area. Layout 1 is characterized by the use of strike conveyors to convey ore on strike with an average LHD hauling distance of 35 m. Layout2 uses LHDs for all on strike conveyance of ore with an average hauling distance of 75 m. These two layouts were then technically and financially compared. It was concluded that layout 1 is theoretically superior but layout 2 was chosen due to its greater flexibility and probability of operational success. Layout 2 was also compared to conventional mining and it was concluded to be more economically feasible. However the latter is a proven mining method in these conditions and has a lower risk operational failure. Bord-and-pillar mining has some favourable promises such as improving labour difficulties, lowering operating costs and providing safer working conditions. The success of mechanized bord-and-pillar mining in narrow tabular steep dipping orebodies will depend on the extent of the research and development efforts which need to create and innovate technologies to overcome some of the current limitations stated in the above-mentioned parameters.

Jan 1, 2003

By K. Schwerdtfeger

Data are presented on the effect of iron oxide on the electrical conductivity of CaO-SiO2-FeO-Fe2O3melts, and on limiting current and impedance in direct current or alternating current charge transfer at iron electrodes. The strong influence of iron oxide content can be utilized for in situ determination of total iron oxide content and Fe3+/Fe2+ratio. The possible probe designs are presented and the principles and procedures of the measurements are explained. Keywords: in situ probe for iron oxide determination in steelmaking slags, electrical conductivity of CaO-SiO2-FeO-Fe2O3slags, direct current over voltage and alternating current impedance at iron/slag electrodes.

Jan 1, 2004

By S. Jeon, J. Kim, H. Lee

Though the importance of the engineering rock mass properties such as deformation modulus, cohesion and friction angle is emphasized, the researches on the reliability of these values are rarely performed. By using modified Takagi-Sugeno (TS) fuzzy inference system, a fuzzy model was developed based on the data obtained from domestic tunnel construction sites, and the ability of prediction was compared with the empirical equations conveniently used for estimating these values, which finds that fuzzy model is better than empirical equation. Sufficiently large database, however, is required for training the fuzzy model for more accurate prediction. Obwohl die Wichtigkeit der technischen Eigentümer der Felsenmassen wie zum Beispiel Verformungsmodulus, Bindekraft und Reibungswinkel betont werden, wird die Forschung auf der Zuverläßigkeit dieser Werte selten durchgeführt. Mit modifiziertem Takagi Sugenos (TS) Flaumigenschlußsystem wird die Flaumigenmodelle von den Daten, die von inländischen Tunnelbaustellen erhalten werden, entwickelt. Zum Schätzen dieser Werte ist es viel günstig, Flaumigenmodell zu benutzen, als zu adoptieren die empirische Gleichung für die Fähigkeit der Voraussage. Genügende große Datenbank wird aber zum Ausbilden flaumigen Modells für genauere Voraussage erfordert. Quoique l'importance sur la caractéristique d'ingénierie de la masse de roche comme le module de déformation, la cohésion et l'angle de friction, soit soulignée, la recherche sur la confiance de ces valeurs est rarement effectuée. Avec le système modifié de Takagi-Sugeno(TS) fuzzy inférence, le nouveau modèle fuzzy s'est développé. Après avoir estimé sa valeur, nous pouvons savoir que ce modèle fuzzy, basé sur les données venant du chantier de construction de tunnel national, est mieux que l'équaton empirique. Pourtant plus de données de base sont indispensables pour produire le modèle fuzzy plus précis.

Jan 1, 2003

By T. O. Hagan

Analyses of accident records show that a better understanding of very basic strata control principles and practices, by production personnel, will improve worker safety. Workers, lack of knowledge, with respect to aspects of strata control, increases their exposure to such strata control risks. The primary objective of the Safety in Mines Research Advisory Committee (SIMRAC) project 02 02 07 was to develop tools for the transfer of strata control knowledge. Four such tools were developed, three of which focused on illiterate underground mine team members who are not yet able to take advantage of the Mining Qualifications Authority (MQA) learning process (see project outcomes 2, 3 and 4 below). The tools were designed to equip these workers with sufficient knowledge and ability to work safely underground until such time as they can take advantage of the MQA system. Project outcomes: 1 A four-minute video using animation to illustrate the causes and prevention of falls of roof in South African collieries. 2 Software to demonstrate the capability of reconstructing, interactively, accident scenes and actions that have taken place underground in stopes. 3 A strata control bridging course for illiterate mine team workers. 4 Small-scale wooden models that will be used to design life-size mock-up facilities to assist with the above mentioned bridging course. 5 Workshops and presentations to demonstrate the outcomes 1to 4 above.

Jan 1, 2005

By T D. Sullivan

Risk lies at the heart of all mining and nowhere more so than in pit slope design. Mining is principally about two areas of risk; safety and economics. This paper addresses the main elements of pit slope design and presents a view of the state of the art in terms of safety, design, prediction of performance, success and pit slope management. There has been a recent trend for serious injury and fatalities due to stability in open pit mines. The causes and contributing factors are analysed in relation to geotechnical knowledge, pit slope design and management. Currently there is no standard classification system for mine slope designs and it is considered doubtful if a universal system is possible. Designs are usually formulated in accordance with many different methodologies, various engineering principals and a number of different philosophical approaches, with results often presented in terms of Factors of Safety or Probabilities of Failure. However wide experience has demonstrated that even with apparently detailed engineering investigation and analysis at Feasibility Level, at the Operating Stage mine slope angles are regularly subject to large changes. The general experience is that these changes are ± 5° and 16° overall, which is considerably outside the accepted order of accuracy. For large deep mines these are huge changes and represent significant risks to the operations. The current state of practice in pit slope design is examined for two stages, feasibility and operating.

Jan 1, 2006

By D. Janicijevic

This paper describes the process of scraper winch pull force measurement and shows the results of the actual winch pull force in extreme stall situations as well as during the face and gulley cleaning. It was found that by slowing down the motor and causing it to slip, torque up to 3.5 times higher than the nominal can be developed, resulting in the same increase of winch pull force. On the other hand, measurements of the actual force needed for cleaning of the face and the gully have shown that the currently used winches are too powerful. The extra torque that can be developed by the already too powerful winch motor poses a significant danger and necessitates the implementation of measures that will eliminate this risk.

Jan 1, 2008

By D. Vogt, T. Hattingh

"This paper argues that the technology change to mechanization is also going to require a change in people. It presents a model for technological progress and adapts it to the mining industry. It then goes on to motivate the need for mines to become learning organizations in order to achieve maximum value from their people as they become less labour-intensive. In an important sense, mechanization is as much about knowledge as it is about technology.The change when a mine introduces mechanization or a level of automation is not simply one of technology but also a stage in the development of mining from ‘art’ to ‘science’. ‘Art’ describes a state of technology characterized by tacit knowledge, an understanding that comes only from experience, and has no formal procedures and little structure. In contrast, ‘science’ represents a state of technology where all the component processes are understood in detail, all knowledge is explicit, and processes and structures are formal.Studies of other industries, including metal part manufacture and aviation, show that each stage in the progression from art to science changes the nature of the organization and requires a different mix of skills from the workforce. Perhaps the most important change is the increase in knowledge and decision-making required as the technology gets closer to science.There is anecdotal evidence that South African underground hard-rock mines are not learning organizations. Mines by their nature are capitalintensive with long lead times from investment to returns, so there is reluctance to change from the original plans or to encourage staff to think independently. Particularly as mines move from art to science, this reluctance must be overcome.The important lesson for engineers involved in introducing mechanization is to understand that success or failure will be determined by the people involved, and not solely by the technology. The process will almost certainly require a culture change on the mine. We recommend that the mechanization team includes an expert in human and organizational behaviour to ensure that a receptive workforce and management are in place to accept the new technology when it arrives."

Jan 1, 2016

By W. Dziurzynski, S. Nawrat, A. Krach

The paper presents research on the influence of the goaf methane inflow on a fire. The problem was investigated by a computer simulation of a fire developing in a goaf. A relevant mathematical model of the fire was selected, which considered both burning of coal and methane. The combustion process is very sensitive on the oxygen and methane concentrations, which was indicated on graphs of the fire temperature evolution. Examples of computer simulation for various location of the fire were considerd. Analysys of results confirms the influence of the content of the goaf methane on development of fires.

Jan 1, 2003

By J. A. Cox

The Ashanti mine is located within the Lower Proterozoic Birimian of Ghana, and covers a concession of 474 square kilometres at its Obuasi operations which comprise large scale underground, surface and tailings treatment facilities. The mine had operated for a century at the end of 1997 and had produced nearly 25 million ounces of gold, a significant proportion of which came from the underground operations. This paper covers the strategy under which exploration for both surface and underground mineral resources was instrumental in enabling the expansion programme to go ahead together with the methodologies and results that have developed in the exploration area over the last five years. Within capital expenditure constraints, the objective on surface is to replace oxide depletion with a secondary objective of discovering new sulphides in areas other than the main trend. In the underground, the exploration strategy is directed at replacement of both underground and surface sulphide depletion, minimising finding costs and assisting the development of long lead time infrastructure. The exploration application describes the methodologies in use for both surface and underground exploration that have been developed in recent years in conjunction with a description of a major review conducted in 1995/96 of the exploration database using an integrated approach, geochemistry, geophysics, remote sensing and structural geology. A revisit of soil geochemical data in particular, and modification of exploration methodology led to the success in finding relatively significant new oxides in 1997.

Jan 1, 1999

By H. Ozturk

In this paper, the computer program ‘SHAFT’ developed for estimation of support requirements for circular mine shafts is introduced. Theory of support design is based on the analytical solutions of circular excavations under non-hydrostatic loading (Detourney and St. John1), and Lame’s thick-wall cylinder theory (Timoshenko6). For rock mass strength property determination Hoek-Brown failure criterion (Hoek et al.2) is used. Mainly two types of support, concrete and steel are taken into consideration as a support member. Program is written in Quick Basic language. Input parameters of the program are shaft radius, number of zones having the same properties along the shaft depth, and depth, unit weight, horizontal to vertical stress ratio, GSI, and uniaxial compressive strength of intact rock of each zone, and compressive strength and safety factor of support member. Output of the program is the graphical representation of shaft with the required support member and thickness throughout the depth of the shaft.

Jan 1, 2003

By W. Zhu

ABSTRACT: This paper presents further developments of the principle of Construction Process Mechanics of rockmasses, The principle of loading variations analyses in space-time is systematically described. To demonstrate the applicability of the theory and method, the effect of the construction process of two practical engineering cases are analysed. ZUSAMMENFASSUNG: Das Mechaniksprinzip vom Konstruktionsprozess des Massenfels wird in diesem Aufsatz weiter Entwickelt.. Das Prinzip von Variationsladungsanalyse mit dem Zeit-Raumseffekt wird systematisch erklaert. Um die Anwendungsmoeglichkeit der Theorie und der Methode zu anschaulich darstellen, das Mechanikseffekt des Konstruktionsprozess wird fuer zwei praktische Anwendungsbeispielen zergliedert. : RESUME: Dans ce papier le development se fait pour principles de la mechanique de process de construction . Le principle de variable analyse considerant effet de temps et de Space est present ´e . Pour demonstrer l´appilicabilite de le theorie et la methode , l´èffect de processe de construction pour ce deax examples sont analysés .

Jan 1, 2003

By Nobuzwe Makhotla, Sasha Boskovic, Steve Hearn

"Mineral separation efficiency in flotation depends, to an extent, on the type of frother used. Huntsman develops and manufactures unique frothers which are suited for mineral processing applications. This paper discusses the Huntsman approach to understanding the industry’s flotation frother requirements to optimise frother selection and introduce the Huntsman’s POLYFROTH® frother range. Specific case studies where the frothers are used are discussed. INTRODUCTION Froth flotation is a process of using bubbles to separate minerals based on their relative affinity for water. Bubbles are induced in the slurry through aeration. Chemistry is used to aid the flotation process and chemical reagents are added to enhance the separation process. The flotation reagents include frothers, collectors, surface modifiers and pH regulators that control physical and chemical conditions of solid, air and liquid phases, respectively. As described by Harris (1976), the key effect is that of bubble size control by way of preservation of the generated bubble size, which is attributed to the coalescence inhibition by the presence of the frother on the bubble surface. Following this, the frother must stabilize the froth phase. Frothers are also added to create optimal conditions for bubble creation and stability by decreasing the surface tension of the water. Depressants may be added, depending on the ore treated, to assist the hydrophilic particles to stay in the water phase. Clay particles may need to be dispersed to prevent them from attaching to the bubbles. Hydrophobic particles attach to the bubbles and are carried to the surface of the slurry where froth is formed. It is important for these bubbles to have the mobility to carry the mineral to the launder where the concentrate is collected. Types of Frothers There are generally three main groups of frothers used in froth flotation. Alcohol Type These frothers have a molecular structure that usually includes 5 to 8 carbon atoms in a hydrocarbon chain and their solubility in water is limited. Methyl isobutyl carbinol (MIBC) belongs to this category and is widely used in the industry. The weaker alcohol-type frothers are more selective and typically suited to finer particles. There are three sub-categories under this group: aliphatic, cyclic and aromatic alcohols."

Jan 1, 2015

By Y. Sagawa

The Hishikari Gold Mine consists of epithermal vein type Au-Ag deposits, each of which has several veins standing almost in parallel each other and inclining 70 to 90 degrees. The veins have 1 to 3m widths and are extracted mainly by drifting and bench stoping with waste rock fill. The Hishikari has tried to optimise the stope dimensions by the Potvin’s Stability Graph Method, which is well known as an easy and effective tool to design appropriate stope dimensions. The method, however, has some limitations of application due to its simplicity so that it has been used only in limited cases. The authors developed a new numerical approach, based on 2D FEM solu-tion for the stability analysis. As a result, it has been possible to solve the Hishikari situation. The authors also introduce the concept of the design approach and compare the results obtained by us-ing the approach with the database of the Stability Graph Method for validation. La mine d’or Hishikari se compose de gisements d'Au-AG avec des types de filons épither-maux dont chacun a plusieurs veines qui sont presque parallèle les unes par rapport aux autres et sont inclinées de 70 à 90 degrés. Les veines ont de 1 à 3 m de largueur et elles sont principalement extraites en creusant et en abattant des bancs de roches encaissantes. Hishikari a essayé d’optimiser les dimensions du chantier d’exploitation avec la méthode de graphique de stabilité de Potvin, bien connue comme un outil facile et efficace pour avoir des dimensions de chantier d’exploitation appropriées. Toutefois, la méthode a certaines limites d’application dues à sa sim-plicité de sorte qu’elle a été utilisée seulement dans des cas limités. Les auteurs ont développé une nouvelle approche numérique, basée sur la solution 2D FEM, pour l’analyse de stabilité. Par conséquent, il a été possible d'expliquer la situation de Hishikari. Les auteurs présentent le concept de l'approche et ils comparent les résultats donnés en l'employant avec la base de données de la méthode de graphique de stabilité pour la validation. Die Hishikari-Goldmine besteht aus Au-Ag-Ablagerungen mit epithermalen Adern, die jeweils mehrere Adern aufweisen, die mit einer Neigung zwischen 70 und 90 Grad nahezu parallel zueinander verlaufen. Die Adern haben eine Breite von 1 bis 3 Metern und werden überwiegend durch Vortrieb von Stollen und Bergversatz abgebaut. Hishikari hat versucht, die Abmessungen des Abbauorts durch das Potvins Stabilitätskurvenverfahren zu optimieren, das als einfaches und effizientes Mittel für die Erzielung angemessener Abmessungen des Abbauorts bekannt ist. Das Verfahren weist jedoch aufgrund seiner Einfachheit einige Anwendungsbeschränkungen auf, so dass es nur in einigen Fällen benutzt worden ist. Vor diesem Hintergrund haben die Autoren einen neuen numerischen Ansatz entwickelt, der hinsichtlich der Stabilitätsanalyse auf der 2D-FEM-Lösung beruht. Dadurch wurde es möglich, das Problem von Hishikari zu lösen. In diesem Dokument stellen die Autoren die Grundlagen des Ansatzes vor und vergleichen die erzielten Resultate durch Benutzung der Datenbank des Stabilitätskurvenverfahrens zur Validierung.

Jan 1, 2003