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By P. E. L. Balestra, A. O. Filmer

The kinetics of the reactions involved in the non-oxidative dissolution of nickel concentrate in hydrochloric acid were studied by electrochemical and powder-leaching methods. It was found that the rate of non-oxidative dissolution increases with a cathodic shift in the mixed potential, which can be achieved by an increase in the nickel-to-sulphur stoichiometric ratio at the reaction surface. An unactivated concentrate with a sulphur content of 36 per cent exhibited a mixed potential of +O,3V (SCE) and could not be leached satisfactorily in 3 M hydrochloric acid at 60°c. When activated material (18 per cent sulphur) was leached, it had a mixed potential of -O,3V, and high iron and nickel extraction rates. Results reported by other workers on the non-oxidative dissolution of sulphides are explained in terms of the mixed potentials at which dissolution occurs.

Jan 1, 1981

By M. David

This paper addresses the problem of technological transfer in geostatistics. Expert systems have become popular in certain fields because the needs of the industry are not provided for by traditional concepts and systems of education. The explicit knowledge approach in developing expert systems is presented through two experiments. The first describes a dedicated system written in GOLDEN LISP and the second a shell, using INSIGHT2, which has more general applications. Using expert systems forces on the user a new approach to parameter definition, and as an example an original method for the research of any anisotropy axes is developed which might well be useful in traditional programming. Two examples of application to a coal and a gold deposit are given.

Jan 1, 1987

By M. Kannenberg

When coal properties are estimated geostatistically for mine planning in the hardcoal industry, there is one important supposition which influences the reliability of prediction of economically profitable parts of the deposit. This is the fact that activities in hardcoal exploration and mine planning are characterized by distinct levels of information and knowledge upon which decisions of economic import must be based, for example, whether exploration should proceed or not, or which methods and strategies should be used to maximize search efficiency. To get more reliable results for mine planning, in particular, advanced kriging methods (e.g. conditional simulation) have to be introduced and checked for their reliability in historical analyses (post-mortem studies). By using this feedback, kriging results from underground samples or production data can be compared with results gained by advanced geostatistical methods from exploration boreholes.

Jan 1, 1987

By C. S. Oteo, H. Suárez, P. de la Fuente

ABSTRACT: In the south of the Island of Gran Canaria (Spain) there appear layers of swelling clays inside volcanic formations of a fonolitic type, down to depths as low as 500 m, with thicknesses of 1 to 3 m. Two tunnels (each of length 1,500 m) have been built in these zones (ignimbrites and swelling clays), work on which started in the ‘70s. The construction has been influenced by phenomena of expansivity and decompression. Presented below are the problems that arose, the field and indoor studies conducted and the numerical optimisation of the lining. ZUSAMMENFASSUNG: Im Süden der Insel Gran Canaria (Spanien) kommen im Inneren vulkanischer Formationen phonolithischen Typs in Tiefen von bis zu 500 Metern 1 bis 3 Meter dicke Blähtonschichten vor. In diesem Gelände aus Schmelztuff und Blähton begann man zu Beginn der siebziger Jahre, zwei Tunnel von jeweils 1.500 Metern Länge anzulegen. Die Bauarbeiten standen unter dem Einfluss von Dehnungs- und Dekompressionserscheinungen. Der folgende Text enthält eine Darstellung der aufgetretenen Probleme, der durchgeführten Feld- und Laborstudien und der numerischen Optimierung der Tunnelauskleidung. RESUME: Dans le sud de l’Ille du Gran Canaria (Espagne) on a détecté des couches d’argile gonflante dans l’intérieur des formations de roches volcaniques fonolitiques, à la profondeur autom des 500 m, avec épaisseur de 1 à 3 m. On a perforé deux tunnels (de longueur 1.500 m chaque un) dans cettes zones (igniumbrités et argiles gonflantes), chantier qui comenza pendant les 70’. La construction on a influencé pour des phénomènes d’expansivité et de décompression. Dans cette communication on présente les problèmes presentes, les études de chantier et théoriques realicés et l’optimisation numérique développé pour dimensionner le revêtement.

Jan 1, 2003

By A. Nicotra, E. H. Roux, J. H. du Plooy, D. H. de Jagger, P. De Waal, G. J. van der Linde

This paper reviews the geology, history, current beneficiation practices, uses, marketing, and future outlook of phosphate in South Africa. The vastness of the reserves, and the industry's efficiency and competitiveness in world terms, are highlighted.

Jan 1, 1989

By use of a finite-difference model of an experimental galvanic cell, the effect of a resistance in the metalic conduction path on the potential and current distributions in the cell was predicted. The model predictions were compared with experimental measurements of potential profiles (measured by use of a scanning reference electrode) and galvanic currents. The predictions agreed well with the experimental measurements. Apart from this model, which is applicable in macroscopic cells (Le. with an electrolyte of low conductivity), a calculation procedure was developed to predict the effect of an external resistance on the galvanic current in a microscopic cell (high conductivity). The responses of the galvanic currents in the microscopic and macroscopic cells to changes in the external resistance were compared. From the similarity of the responses, a simple practical procedure for the evaluation of the external resistance (meter resistance) that can be tolerated is proposed.

Jan 1, 1989

By R. M. G. Machunter

The dynamic behaviour of plant circuits and the available instrumentation determine the control strategies that are appropriate for the duty of the mineral separation plant. Although steady state modelling is appropriate to provide the main requirements of grade and throughput capability of a plant, it is the dynamic characteristics that determine the tolerance of the plant to disturbances and also its controller ability. This paper explores these issues with respect to the additional use of dynamic modelling to achieve these objectives.

Jan 1, 2007

By M. L. Smith

A new approach to strategic planning, the Life of Business Optimisation System (LOBOS) optimises production systems from the scale of stopes in a single mine to an entire business strategy consisting of multiple mines and products competing for capital and processing capacity. LOBOS has optimised cash flow for a wide variety of operations, including large metalliferous or coal mines and as an aid to high-level strategic business optimisation solution to multi-mine/processing/product complexes. This paper discusses the application of optimisation technology to strategic planning with an emphasis on project evaluation with examples on the application of LOBOS to a variety of recent projects.

Jan 1, 2007

By G. Ferrara

The mathematical framework of a well-established model proposed earlier by the authors for the screening process is briefly recalled. Some numerical methods for the application of the model, concerning numerical solution of the equations and parameter estimation, are indicated. Some applications of the model to improve screening operations, sizing of screen, simulation of screening and of integrated plant operations are discussed, and the computer software to be used for these purposes is described in detail.

Jan 1, 1987

By D. Francois-Bongarcon

The ?Poisson effect? is defined and characterized. It takes place even when the material to sample is not liberated. Gy, Pitard, Ingamells, and others, including the author, recommend that a minimum average number of particles of mineral of interest characterize the recommended sample size. How many? Recommended numbers range from 6 to 40 particles depending on authors, corresponding to standard deviations of 41% to 16%. Some guidelines are proposed, and the often alleged ?double-Poisson? effect is examined.

Jan 1, 2009

By D. F. Howarth, F. F. Roxborough

Some important aspects of the design of rock-cutting systems remain relatively unexplored. Two areas of practical significance in this context form the subject of this paper: cutting in jointed or fissured rock, and groove-deepening. A series of controlled laboratory experiments on the performance of disc cutters in jointed rock showed that the spatial and geometrical configuration of jointed rock masses needs to be taken into consideration in the design of mechanized rock excavating systems. One series of experiments showed that, under favourable geometric conditions, the energy required to cut in a jointed rock mass is at least half that required to cut otherwise intact rock. Groove-deepening-the progressive deepening of a groove by successive passes of a cutter-is a potential operational feature with most mechanized rock-excavating systems. Laboratory experiments revealed an important fundamental cycle of events associated with disc cutters when progressively deepening a groove in intact rock. Furthermore, in contrast to pick cutting, groove-deepening by discs is shown to be an efficient operation and one that should not necessarily be avoided. This can be directly attributed to increased interaction between the disc cutters as the result of an increase in magnitude of the lateral forces generated as a groove is deepened.

Jan 1, 1982

By J. Gholamnejad

Determination of the optimum cut-off grades is one of the most important aspects of mine production planning. A cut-off is a grade below which we choose not to process material. This material is treated as waste and dumped. Dumping waste is accompanied by the rehabilitation cost which will affect the overall cost of final production and also the optimum cut-off grade. Rehabilitation cost is the cost per ton of rehabilitating material of a particular type of rock after it has been dumped as waste. One of the most popular algorithms for determination of the optimum cut-off grade is Lane?s method. Lane formulated the cut-off grade optimization, but he did not consider rehabilitation cost during the optimization process. This cost item should be evaluated first, and then considered during the cut-off grade optimization process. In this paper the rehabilitation cost is inserted directly into the cut-off grade optimization process using Lane?s theory. The cut-off grades obtained using the suggested method will be more realistic than ones using the original form of Lane?s formulations.

Jan 1, 2009

By Gernot Beer, Christian Dünser, Marcos Noronha

The main findings of the joint research initiative “Numerical Simulation in Tunnelling” and a follow-on project on efficient numerical simulation models for tunnelling are presented. Die wichtigsten Resultate des Forschungsschwerpunkts „Numerische Simulation im Tunnelbau“ und einem Folgeprojekt über effiziente numerische Simulationsmethoden werden präsentiert Les résultats les plus importants du point principal de la recherche "simulation numérique dans la construction de tunnels" et un projet consécutif sur des méthodes de simulation numériques efficaces sont présentés

Jan 1, 2003

By C. M. Suhr

n order to validate the borehole analysis valuation procedure commonly used in the South African gold mining industry, a simulated orebody was used to create borehole values which would serve as data for the procedure. After confirming the distribution, calculating the variance size of area relationship, estimating the block variance, and calculating a profit measurement for each set, comparisons were made to the known population parameters. Results show only one overall bias (in the estimation of the lognormal third parameter), which is carried throughout the analysis. The remainder of the analysis is unbiased, validating the procedure.

Jan 1, 1987

By J. -M. Chautru

A geostatistical simulation of a typical mining site for polymetallic nodules in the North Pacific Ocean is presented. This is the first stage in the design of an industrial mining system. Two variables which have a major effect on the orebody's economic potential are considered, namely: the maximum slope of the ground inside a mining block of 50 x 100 m; and the average quantity of nodules on the same support. Two geostatistical problems have emerged in this study. The first is due to the lack of a change of support model for the maximum of a variable. A provisional solution, considering an experimentally accessible 'equivalent' support, is proposed. The second is due to a non-linear link between the two variables. To be able to take this into account in the simulation, we propose a new method based on the decomposition: X = E(X/Y) + Residue (X). Satisfactory results were obtained with this approach.

Jan 1, 1987

By I. Zemanek, A. Rozsypal

Mrazovka tunnel was excavated under one building whose subsurface space was not possible to reinforce against additional settlements induced by digging. In the presented contribution the risk analysis, warning levels and results of deformation measurements are described. Lespace souterrain d‘un des bâtiments sous lequel le tunnel Mrazovka a été creusé n‘a pu être renforcée contre l‘affaissement supplémentaire provoqué par l‘emplacement du tunnel. Le matériel présenté décrit l‘analyse des risques, le niveau des limites et les résultats des mesures des déformations. Der Untergrund eines der Gebäude, unter dem der Tunnel "Mrazovka" ausgeschachtet wurde, war es nicht möglich, gegen nachträgliches Setzen zu versteifen, hervorgerufen durch die Untertunnelung. Im vorliegenden Beitrag sind Gefahrenanalyse, Grenzwerte und Ergebnisse von Deformationsmessungen beschrieben.

Jan 1, 2003

By J. Palarski

Long waling is used in most Polish coal seams, with backfilling to support the roof, to create an artificial hanging wall to prevent movement if the rockmass, and to eliminate the fire hazard in abandoned mine workings. This paper discusses the results if tests conducted on 7 different backfill mixtures, and gives equations for the estimation if the flow if backfill slurries through gravitational pipelines.

Jan 1, 1994

This paper details the preliminary design work carried out before and during the implementation of an extensive backfilling programme on Cooke 3 Shaft, Randfontein Estates Gold Mining Company (Witwatersrand) Limited. The design work is of relevance to any system utilizing a cementitious binder, and the quality control aspects are of particular significance. Problems associated with correlating laboratory results to actual field results are also briefly discussed.

Jan 1, 1988

By W. K. Brinsden

The Australian Institute of Geoscientists (AIG) held their fifth successive annual seminar at Observation City, Scarborough, in Perth on 15th November, 1990. The title of the seminar was 'Strategies for Grade Control'. The Seminar attracted 158 delegates, including 10 speakers. In addition to geoscientists, the attendees included mining engineers, metallurgists, and mining analysts. The welcoming address was given by Rob Duncan, Chairman of the Westem Australian Branch of AIG, who said there is a strong demand for this type of seminar in Western Australia (WA). It helps geoscientists to keep up with former colleagues and to keep abreast of technical developments.

Jan 1, 1991

By C. Kliem

Geological, tectonic, geochemical and geophysical data were utilized for the mineral resource assessment of the Biga Peninsula in NW Turkey. During the deductive phase of the project multivariate statistical methods were applied to accentuate characteristic parameters which sufficiently describe the different types of Pb - Zn mineralization. The parameters most likely to be indicative of mineral occurrences were determined. In the following prognostic phase these parameters were further statistically treated to determine favourability indexes for the occurrence of a deposit within each cell of the training area. Preliminary results of probabilistic, univariate and multivariate methods are presented.

Jan 1, 1987