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By B. Z. Weiss, N. R. Comins, F. Blum

The effect of microstructure on the deformation and fracture properties of 3CR12 steel was investigated at different strain rates in the temperature range -196 to 200°C. The yield stress of the as-received steel, showing a banded dual-phase microstructure, was much lower than that of the flake-like dual-phase microstructure produced by heat treatment. The heat treatment also resulted in an increase in the volume fraction of martensite. The fracture toughness of the as-received 3CR12, on the other hand, was significantly higher than that of the heat-treated material. These changes in both yield stress and fracture toughness were attributed to the effect of microstructural parameters on the constraints imposed on the deformation and subsequent failure of the ferritic phase in the as received and heat-treated steels. The exceptionally low resistance to crack extension in a plane parallel to the roiling plane of the as-received material was ascribed to the delamination process, which is typical for controlled-rolled steels. The yield stress and fracture toughness were found to depend on temperature and strain rate. The appearances of the fracture surfaces were found to be consistent with the mechanical properties.

Jan 1, 1992

Scrap printed circuit boards were selectively smelted at 1 200°C to produce a metallic alloy having three phases. These phases were identified as a lead-rich phase, a low tin content alpha bronze phase, and a high tin delta phase. Electrochemical leaching studies on this alloy were done in 1 mol/dm3 sulfuric acid or in 2 mol/dm3 hydrochloric acid (adjusted to an ionic strength of 3 mol/dm3). The lead rich phase was more strongly passivated in sulfate media, and in this medium the high tin content delta bronze was more resistant to corrosion than the lower tin alpha bronze phase. In chloride medium the lead phase and both bronze phases corroded readily, but with current densities about an order of magnitude lower than in sulfate medium (static conditions) for the bronze phases. The high tin delta bronze phase was found to form a passivating layer in sulfate media. A similar layer was not seen in chloride medium. The leaching studies in sulfate medium also showed the existence of an alpha bronze phase of lower tin content in the centres of the alpha phase grains. This phase was quite resistant to leaching in sulfate medium.

Jan 1, 2009

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 M. S. Janssen, J. L. Taylor, M. A. Ford, E. B. Viljoen, H. A. Simonsen

The Stilfontein and Buffelsfontein Gold Mines, near Klerksdorp in the Transvaal, had accumulated a large amount of uranium-containing residue and, when the price of uranium rose in the 1970s, consideration was given to the possible recovery of this uranium. Preliminary tests showed that concentration of the uranium prior to leaching would not be economic. However, the pyrite in the residue could be concentrated by flotation, and the flotation concentrate could be roasted to pro¬vide both enough acid for leaching the uranium and a calcine from which the gold could be recovered. The feasibility study showed that a uranium operation of 270 kt per month would be most economically attrac¬tive, and a plant of that size was accordingly designed and built. In the first six years of its existence, the plant treated over 20 Mt of residue and produced about 3,5 kt of uranium oxide. During that time, the plant was con¬tinually being improved to make it more reliable and cost-efficient. This paper analyses the operation of the plant during its first six years from the viewpoints of its mechanical, process, and economic performance. The criteria on which the selection of the process was based are reviewed and compared with the actual performance of the plant, emphasis being placed on the leaching, solid-liquid separation, recovery, and purification stages.

Jan 1, 1987

By F. G. Hill

The paper reviews the restrictions imposed by the Department of Mines (now the Department of Mineral and Energy Affairs) on the surface use of ground that has been undermined at shallow depths (down to a depth of244m). The reasons for the restrictions are discussed, with special reference to the early records kept by the Department of Mines on subsidence and fracture of the surface. A discussion of the nature of the strata overlying the ore-body, and the effect of undermining, is followed by a detailed account of investigational work, particularly since 1970, on the stability of shallowly undermined ground. The significance of the data collected during the investigations is considered next, with special reference to the social and economic implications. These are so farreaching, that it is proposed that the already flexible approach of the Department of Mineral and Energy Affairs in considering what structures may be built on undermined ground should become even more flexible. To this end, the appointment of a Commission is proposed to collect as much information as possible on the stability of ground undermined at shallow depth, and to revise the current overrestrictive conditions or guide lines that are in use.

Jan 1, 1981

By A. M. Engelbrecht

Paper written on project work carried out in partial fulfilment of B Eng. (Chemical) Membrane processes are vital to a diverse range of technical and biological systems, which also feature in mineral processing applications such as the treatment of mine effluent and extraction of metals. In this study, the use of cellular automata to model a semi-permeable membrane that separates two compartments is considered. Cellular automata are simple models that enable the analyst to represent well-understood local effects, such as the chemical or steric interaction between molecules themselves and between molecules or particles and their environment, which can lead to very complex behaviour on a macroscopic scale. Various physical phenomena, including reverse osmosis, were simulated. Initial results for the effect of temperature, membrane structure and chemical properties of the solutes on the performance of the membrane appear promising. Keywords: cellular automata, dynamic modelling, filtration, membrane fouling, osmosis.

Jan 1, 2007

By E. Uslu

The kinetics of the reduction of chromite from the LG-6 layer of the Bushveld Complex in Fe-Cr-C alloys were studied in the temperature range 15OO°C to 1680°C under an inert argon atmosphere. The rotating cylinder technique was used, and the rotational speed of the chromite cylinder ranged from 0 to 1000 r/min. The melt consisted of 30 to 80 per cent chromium and 2 to 8 per cent carbon. The initial chromium-te-iron ratios of the melts varied between 0,42 and 4,95. The reduction of chromite spinel was analysed in terms of the decarburization of the metal. It was found that decarburization increased with an increase in the temperature, the carbon content of the bath, and the rotational speed of the cylinder up to 400 r/min, after which it remained almost constant. Decarburization also increased with an increase in the chromium content up to about 50 per cent chromium but, at higher chromium contents, it decreased. In the early stage of the reduction, up to about 30 minutes of reaction time, the liquid-state mass transfer of oxygen was found to be the most likely rate-determining step. The apparent activation energy was calculated to be 84,864 kJ per mole of oxygen. In the later stage, diffusion of iron and/or chromium in the solid state is the most likely rate-determining step. The apparent activation energy for the diffusion was calculated to be 471,18 kJ/mol.

Jan 1, 1991

By C. R. S. Needes, M. J. Nicol, G. T. W. Ormrod, N. P. Finkelstein

The industrial application of a dioxide electrode uranium by C. R. S. NEEDES, Ph.D. (London) (Visitor), M. J. NICOL, Ph.D. (Rand) (Visitor), N. P. FINKELSTEIN M.Sc. (Rhodes), Ph.D. (Liverpool) (Fellow), and G. T. W. ORMROD (Visitor) A correlation between the potential of a U02 electrode and the rate of recovery of uranium has been proved in laboratory and plant trials. When the recovery rates change because of variation in the concentrations of Fe(III), Fe(II), SO4 'and H+, a positive correlation is observed. However, an 2- increase in the concentration of phosphate in solution produces an increase in the U02 electrode potential but a decrease in the rate of leaching of U02. The correlation between the U02 electrode potential and the rate of leaching of U02 is then negative. It is concluded that, as a control device, the electrode cannot compete with the platinum electrode for use on certain plants. Nevertheless, the U02 electrode will act as a useful warning device if the total concentration of iron in solution decreases to below a level concomitant with the economic recovery of uranium. Furthermore, because of the positive correlation between the U02 electrode potential and the phosphte concentration, the electrode will also be of value in the detection of an increase in the phosphate level in solution. When it was incorporated in a suitable industrial probe, the electrode was found to be able to withstand the rigours of the leaching conditions in a large pilot-plant pachuca, and only failed after six weeks' operation.

Jan 11, 1975

By J. A. Voster

Premier Mine (a part of De Beers Consolidated Mines Ltd) which is situated 38 km to the east of Pretoria, has the largest known diamond pipe in South Africa. The mine started operations in1903. The Premier Mine kimberlite pipe is unique in that it is intersected by a 75 m thick gabbro sill at a depth of 400 m below surface. The current mining method used is mechanized panel retreat caving, which has been successfully used to extract ore from the different mining blocks. All caving at Premier Mine is below the sill and failure to exercise good draw control could cause the early ingress of gabbro waste. Draw control at Premier Mine is crucial as it aids in preventing conditions of isolated draw, which results in the early ingress of waste, compaction of the kimberlite and the loss of ore reserves. To assist, an underground vehicle monitoring and control (VMAC) system was installed to enable the effective management of the draw control function. The system has evolved graduallyin collaboration with a local developer. The data accumulated is used to decide the most effectivedraw point loading pattern in order to achieve sound draw control principles. This is achieved as each load can be related back to the draw point of origin. The VMAC data recorded also relates back to specific load-haul-dumps (LHDs), tunnels, ore passes, as well as indications of dates, times and payloads recorded. An interface exists between the VMAC and a draw control linear program. Premier Mine’s VMAC system is not a ‘dispatch’ system but rather a draw control system that caters for Premier Mine’s specific block cave requirements. Premier Mine has realized that successful automation is not dependent on technology alone but rather on the successful implementation thereof.

Sep 1, 2001

O.F.S. Branch Minutes of the Committee Meeting held in the Committee Room at the St. Helena Club at 4.45 p.m. on Wednesday, 3rd September, 1975. Book reviews JONES, M. J. (ed.). Minerals and the environment. London, Institution of Mining and Metallurgy, 1975. Mining Companies of the world.. 1974/75. London, Mining Journal Books Ltd (15 Wilson Street), 1975. £12. 303 pp. NIM reports Report no. 483 Summary of the mineralogical investigation of pegmatites. (11th April, 1969; re-issued October 1975). Report no. 1697 A petrographic and mineralogical investigation of silica samples from the farm Elandskraal 470JQ, Rustenburg district. (24th Jan., 1975; reissued October 1975). Report no. 1761 The determination, by atomicabsorption spectrophotometry, of minor elements in anode sludges and residues. Report no. 1762 The determination, by instrumental neutron-activation analysis, of some elements in the NI M ROC standard reference materials. Report no. 1770 The spectrophotometric determination of vanadium in chromiumbearing materials. Foundry conference An international foundry confcrence, spomored and organized by South African Institute of Foundrymen, will be held in Johannesburg from 23rd to 27th February, 1976. The themes for each day are follows: Coordination chemistry A symposium on coordination chemistry in extractive metallurgy is to be held in Kelvin House, Johannesburg, on 18th and 19th March, 1976. Practical jet cutting The third international symposium on jet-cutting technology to be organized by BHRA Fluid Engineering will be held in Chicago from 11th to 13th May, 1976, in conjunction with the lIT Rese:uch Institute of Chicago. Hydraulic transport The fourth international conference on the hydraulic transport of solids in pipes (Hydrotransport 4) is being organized by BHRA Fluid Engineering.

Jan 12, 1975

By S. R. Stadler

Koffiefontein Mine commissioned a distributed antenna system as an underground communication backbone for the DISPATCH® production management system during September1999. STAS Ltd, the supplier of the Distributed Antenna System developed the System for an Integrated and Automated Mine (SIAM). This communication system, in conjunction with DISPATCH®, fulfils Koffiefontein Mine’s present and future requirements for accurate draw control, increasing productivity and improving working conditions. The DAS as SIAMnet communication network was selected by the mine, because of its superior data transmission rate of up to 1.5Mbps at 860MHz, video and Ethernet transmission facilities, and future enhancement abilities. The results of the commissioning tests confirmed the quality and integrity of the data and voice communication. The initial installation enabled 9000 metres of underground production tunnels with voice communication inclusive of 3700 metres having data communication. This article discusses the requirements and selection of the telecommunication system for an underground mine. A description of the installed distributed antenna system follows with a summary of the commissioning tests. A discussion of the reliability of the components is followed by conclusions with suitable recommendations. Keywords: distributed antenna system, underground mining, telecommunication system.

Sep 1, 2001

By A. Mainza

It is common practice in the mineral processing industry to use hydrocyclones for particle classification. However, classification in the UG2 platinum circuits using the hydrocyclone poses major challenges due to the differences in density between silica and chromite, the two major components of this ore. Silica,-the PGM carrying component, has an average density of 2.7 and the barren chromite component has an average density of 4.5. When conventional and flat bottom cyclone are used there is a misplacement of particles due to differences in density leading to inefficiencies in the classification by size. As a result of the density effect, coarse silica reports to the overflow, resulting in loss of recovery, and fine chromite reports to the underflow, resulting in loss of milling capacity and unnecessary production of fine chromite. A classifier based on a different concept was required in the classification of UG2platinum ore. The three-product cyclone, which is a hydrocyclone with two concentric vortex finders to produce three distinct products, has been tested in the UG2 ore application and indications are that misplacement of particles due to differences in the component densities can be minimized through the use of this unit. Industrial and pilot plant trials were conducted and indications are that the three-product cyclone can be installed to selectively produce a middlings stream that can be screened using Pansep screens to provide a screen oversize, which is predominantly coarse silica that can be preferentially reground to recover the PGM values contained in the coarse silica.

Jan 1, 2004

By Steve Konieczki

[ ] Great Basin Gold Ltd. (GBG) owns the Hollister Mine and operates it through the wholly owned subsidiary Rodeo Creek Gold, Inc. The property is located in northern Nevada on the Carlin Trend gold belt within the historic Ivanhoe Mining District. The mine is located on the western edge of the Northern Nevada Rift, a major north-northwest trending structural zone that has localized middle Miocene volcanic rocks and numerous epithermal gold deposits. The precious metal deposits are low-sulfidation epithermal systems characterized by banded quartz veins with electrum and silver selenides. The Hollister Mine will employ the selective underground mining method of cut and fill. This will be combined with split shooting (resuing mining method) to optimize recovery and reduce dilution. The focus of mining will be on extraction of ?ounces? from the narrow-veins rather than trying to maximize tons. The initial drifts will be excavated along the strike of the vein and then capped with a substantial concrete sill pillar. Back stoping with hand held drills will be used to selectively mine the vein. The stopes will be backfilled with waste rock material. With every lift, an 18 inch concrete cap will be poured onto the backfill waste rock to prevent gold values from being lost into the fill. Targeted ore production rate will be over 400 tons per day. With current ore reserves, project life is estimated to be around eight years; however, Hollister geologists view the site as one of the most prospective systems for bonanza vein deposits in Nevada. Approximately $14

Jan 1, 2008

By Y. -H. Chang, Y. -J. Jou, T. -S. Ueng, I. -H. Peng

In order to systematically study the size effect on the shear strength of rock joints, this study used the computer-aided-manufacturing system to reproduce the artificial rock joints for saw-toothed joints, Barton's standard joint profiles of JRC = 4~6 and 18~20, and natural rock joint profiles. We divided, enlarged, reduced, and assembled these joint profiles to obtain joint specimens of various sizes ranging from 75 mm to 300 mm in length. The shear strengths of these joint specimens were tested under different normal stresses using a direct shear test apparatus. The surface conditions of the joints at failure were also examined. The size and geometry effects on the shear strengths of these joints of various sizes and configurations were evaluated based on the test results. Um die künstlichen Trennflächen für reguläre dreieckige Trennflächen, Bartonsche standardmäßige Querschnitte der Trennflächen von JRC = 4~6 und 18~20 und natürliche Querschnitte von Trennflächen wiederherzustellen, benutzt diese Forschungsarbeit das Computergestützte-Erstellungssystem, damit die Maßstabswirkung auf die Scherfestigkeit von Trennflächen systematisch untersucht werden kann. Die Querschnitte werden geteilt, vergrößert, verkleinert und zusammengesetzt, um Trennflächenproben in Längen variierend von 75 mm bis 300 mm zu erhalten. Die Scherfestigkeit dieser Trennflächenproben wird unter unterschiedlichen Normalspannungen mit einem Direktscherversuchsgerät getestet. Die Querschnittszustände der Trennflächen bei Versagen werden ebenfalls untersucht. Nach den Untersuchungsergebnissen werden die Maßstabs- und Geometriewirkung auf die Scherfestigkeit dieser Trennflächen verschiedener Größen und Konfigurationen ausgewertet. Pour étudier systématiquement l’effet de la dimension des fractures des roches sur leur résistance au cisaillement un système de creation de fractures artificielles à l’ordinateur a été employé. Des fractures artificielles triangulaires, profils de fractures de Barton avec JRC = 4~6 et 18~20, et profils de fractures naturelles ont été reproduits. Les profils des fractures ont été arrangés de manière à obtenir des échantillons de longueur entre 75 et 300 mm. Une boîte de cisaillement a été utilisée pour étudier la résistance des fractures au cisaillement, sous plusieurs conditions de contraintes normales. Les conditions superficielles des fractures après rupture ont été étudiées. Les résultats de ces essais, effectués sur plusieurs échantillons de dimensions et configurations variées, ont contribué à établir l’influence des dimensions et de la géométrie des fractures sur leur résistance au cisaillement.

Jan 1, 2003

By J. L. Louw

The utilization of centralized blasting systems is progressively becoming a feature of the South African mining industry, owing to increased pressure from the Department of Mineral Resources (DMR) to ensure safer blasting conditions. The purpose of a centralized blasting system (CBS) is to ensure reduced blasting-related incidents and to improve the underground working environment for the mine?s employees. The brief from Samancor Western Chrome Mines (WCM) pertaining to this study was to explore?at a conceptual level?all variables pertaining to the implementation of the CBS. Studies have indicated that Sasol?s SafeBlast? was preferred due to low overall risks and user-friendliness. Empirical observations, however, indicated that attention should be given to the current shaft-clearing procedure and to the installation of additional transformers. This is required to co-ordinate the power supply from 2 level to 10 level with the required supply of the network slave station. A cost analysis indicated that an electronically initiated CBS will result in a R24 cost increase per panel, which relates to a mere 1% cost increase per panel. This cost, in addition to the R1.1 million capital cost, proved to be negligible in comparison to the possible direct and indirect costs incurred by the mine in the event of a blasting-related incident. It was found that Samancor should conduct further studies incorporating the necessary requirements to ensure a successful transition, while considering all stakeholders on the mine. This study proved that the transition to a CBS would ensure safe and efficient blasting at Samancor?s Mooinooi Mine.

Jan 1, 2012

The annual General Meeting of the Branch was held in the St. Helena Club on Wednesday, 4th August, 1971 at 8.00 p.m. Mr N. A. Honnet (Immediate Past Chairman) was in the chair. There were also present Mr V. C. Robinson, President of the South African Institute of Mining and Metallurgy. Nine Fellows: Messrs J. R. F. Handley, C. J. Isaac, J. Lorenzon, J. M. Meyer, C. Mostert, D. A. Smith, S. L. S. Swart, I Thomas and R. G. Williams. Five members: Messrs R. Campbell, A. H. Edwards, K. Pearce, G. P. Rundle and R. B. Sutherland. Five graduates: Messrs J. E. Andrews, E. J. Shillaber, M. H. Smith, T. R. Stromsoe and D. J. van Niekerk. Two associates: Messrs A. Paschalides and D. S. Robinson. Eight visitors. Total present: Thirty-one. MINUTES OF THE PREVIOUS GENERAL MEETING As the minutes of the General Meeting held on the 16th June, 1971, had not been published in the Journal, the Chairman moved that the adoption and discussion thereof be deferred to the next General Meeting. This motion was adopted unanimously. The minutes of the General Meeting held on the 10th February, 1971, were taken as read. The adoption, which was proposed by Mr D. A. Smith and seconded by Mr J. M. Meyer, was carried unanimously. At Mr Honnet's request, Mr V. C. Robinson took the chair during the presentation of the Chairman's Annual Report. CHAIRMAN'S ANNUAL REPORT 1970/71 1970/71 Committee-Office Bearers: Chairman - J. N. Saunders Vice Chairman - G. Y. Nisbet Immediate Past Chairman- N. A. Honnet. Due to the sudden retirement of Mr J. N. Saunders, the committee, at a meeting on the 3rd February, 1971 elected Mr G. Y. Nisbet as Chairman with Mr J. M. Meyer as Vice Chairman. After the transfer of Mr Nisbet to C.D.M., the committee, as a meeting on the 12th May, 1971, decided that Mr Meyer hold the Chair in an acting capacity for the remainder of the year. Committee members: Messrs C. J. Isaac, J. G. Kirchener, L. O. W. Leimer, R. S. Pearson, I. G. Thomas and A. von Holdt. Transfers of several office bearers and committee members resulted in Messrs J. M. Meyer, D. N. Smith and G. C. J. Young being co-opted onto the committee.

By T. Tholana, P. N. Neingo

"A mineral resource constitutes the principal underlying asset of a mining company, and must be exploited and managed in such a way that maximum value is derived from it. Various asset management frameworks applicable to physical assets are available. This paper focuses on the extension of an asset management approach, particularly the Publicly Available Specifications (PAS) 55 asset management framework and the International Organization for Standardization (ISO) 55000 series of standards, to mineral assets. It is concluded that PAS 55 and the ISO 55000 series of standards can be extended to manage mineral assets, resulting in an integrated approach to sustainably optimize value from the company’s mineral assets. The benefits include improved returns on mineral assets, maximum mineral asset utilization, creation of an organizational culture focused on quality and continuous improvement, and assurance to stakeholders that the mineral assets are being efficiently managed over their entire life-cycle. In the context of this paper, a ‘mineral resource’ refers to both Resources and/or Reserves as classified by the SAMREC Code. IntroductionMining involves the extraction of valuable mineral resources from the Earth’s crust. A mineral resource is unique among natural resources in the sense that it is a wasting asset, which means that its value depreciates continuously with extraction. In addition, it is often impaired from time to time as commodity price changes (Macfarlane, 2011a). Since a mineral resource is a wasting asset there is a single opportunity available to optimize value from its extraction. Mine planning involves identifying a strategy to exploit the mineral resource in a way that maximizes value at an acceptable risk level throughout the life of mine (LOM). This optimum extraction strategy changes as economic conditions change, particularly commodity prices, as well as with improvements in orebody knowledge as mining progresses. It is the mineral deposit that competitively distinguishes two different mines and dictates the location of a mine; hence the adage ‘the orebody dictates’. Therefore, a mineral resource is the primary tangible asset possessed by mining companies and must be managed in such a manner that maximizes its value at an acceptable risk level (Macfarlane, 2011a)."

Jan 1, 2016

By Z. Hou

ABSTRACT: Short-term strength, damage and healing boundaries for rock salt are experimentally determined and integrated into the Hou/Lux-MDS damage-healing model. This model can be used to describe the mechanical behaviour of rock salt during a damaging process (under high stress to strength ratios) as well as during a healing process (under very low stress to strength ratios with high confining pressure). The development of the damage and the stress to strength ratio in the excavation damaged zone (EDZ) of a storage cavern under a minimum internal pressure as well as the development of the healing of damage and the stress to strength ratio under a subsequent maximum internal pressure are investigated project-related. The results of the investigation make it possible to shift the permissible minimum pressure boundary down, allowing the optimisation of decisive economic characteristics of storage caverns. RÉSUMÉ: Le comportement court terme, l’endommagement et les conditions de colmatage pour le sel gemme ont été étudiés expérimentalement et intégrés dans le model endommagement-colmatage Hou/Lux-MDS. Ce modèle permet de décrire le comportement mécanique de sel gemme pendant le processus d’endommagement (sous fort rapport contrainte-résistance) et le comportement du processus de colmatage sous très faible rapport contrainte-résistance avec forte pression de confinement. Le développement d’endommagement et le rapport de contrainte-résistance dans une zone d’endommagée (EDZ) d’une cavité de stockage avec un maximum de pression de soutènement ont été étudiés. Les résultats de cette étude permettent de conclure qu’il est possible de baisser la pression de soutènement, et par conséquent d’optimiser les caractéristiques économiques décisives des cavité de stockage. ZUSAMENFASSUNG: Für Steinsalz werden Festigkeits-, Schädigungs- und Verheilungsgrenze experimentell ermittelt und in das Schädigungs-Verheilungs-Modell Hou/Lux-MDS integriert. Damit kann das mechanische Verhalten von Steinsalz sowohl bei einem Schädigungsprozess (mit hohen Ausnutzungsgraden) wie auch bei einem Verheilungsprozess (mit niedrigen Ausnutzungsgraden) beschrieben werden. Projektbezogen werden die Schädigungs- und Ausnutzungsgradentwicklung in der Auflockerungszone einer Speicherkaverne unter einem minimalen Innendruck sowie die Verheilungs- und Ausnutzungsgradentwicklung unter einem anschließenden maximalen Innendruck untersucht. Die Untersuchungsergebnisse erlauben, die zulässige Minimaldruckgrenze nach unten zu verschieben, so dass entscheidende wirtschaftliche Kenngrößen von Speicherkavernen optimiert werden können.

Jan 1, 2003

By T. R. Marrero, J. W. Wilson

The transportation, by water that flows through a pipeline, of coals in the form of water-impermeable cylinders is discussed, and shown to have distinct advantages over other forms of coal transportation, including significantly reduced costs for larger throughputs. The description of the concept comprises various aspects of the system, such as methods for the manufacture of coal logs, their injection into the pipeline, the manner in which they are conveyed in the water in the pipe, and the methods used for their preparation as feed material to electric power stations at the end of the pipeline. It is pointed out that the technology involved in the transportation of coal in the form of logs via pipelines is applicable also to other minerals and commodities.

Jan 1, 1993

By H. Van Aswegen, C. V. B. 0unningham

The need for the more accurate measurement of blasting results has increased substantially with the proliferation of the types of explosives available to mining operations in South Africa. The primary object of blasting is the production of broken rock of a specific size distribution. A method for the measurement of size distribution, more popularly known as fragmentation, is being developed at Sishen Iron Ore Mine, and the object of this paper is to describe the method briefly and so encourage an exchange of views on reliable methods. Once the fragmentation of broken rock can be assessed reliably, meaningful conclusions can be drawn from blasting trials. It will then be possible for equipment productivity to be related to muckpile properties, with the accompanying advantages.

Jan 1, 1986