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By A. T. Visser

"SynopsisAlmost 20 years have passed since the cutting-edge research by Thompson and Visser on the design and management of opencast mine haul roads was conducted in South Africa. This system is based on three principles, namely the structural ability to support the ultra-heavy truck loads, the selection of vehicle and environmentally friendly riding surface, and an appropriate level of maintenance to counteract wear and tear. Obviously, proper layout and geometry are essential.These principles have been implemented worldwide, and it is useful to review the lessons learned. The objectives of this paper are to present a critical review of the status of mine haul road design and management, and the impact that these principles have made on operations, particularly the cost-effectiveness. The paper briefly reviews the principles of the haul road design and management and the extent to which they are applicable. Case studies of a number of implementations are presented to demonstrate that the principles are sound and have been applied effectively. For example, at an international operation the transport cost of coal was 40% more expensive than anticipated in the feasibility stage, and this made the mining operation uneconomic. Correction of this problem resulted in a viable enterprise. Although designed for opencast operations, the principles are equally valid for underground operations, and initial development work will be discussed.The main conclusions are that the research approach is valid and its effectiveness has been demonstrated in a number of applications. The anticipated financial benefit has been derived, and has made the mining operations that used the principles more effective. Of major importance is the application of opencast haul road design principles to the future thrust of using driverless vehicles in opencast and underground mining, where the road quality is not negotiable as there is no driver that can avoid obstacles or severe road deterioration.IntroductionAlmost 20 years have passed since the cutting-edge research by Thompson and Visser on the design and management of opencast mine haul roads in South Africa (Thompson and Visser, 1996a, 1996b, 1998, 1999, 2000a). This system is based on three principles, namely the structural ability to support the ultra-heavy truck loads, the selection of vehicle and environmentally friendly riding surface, and an appropriate level of maintenance to counteract wear and tear. Obviously, proper layout and geometry are essential."

Jan 1, 2015

The practice of pumping gases which inhibit combustion for purposes of controlling or extinguishing mine fires is now universally accepted. The practice has been used many times in coal mines in India and the experiences are reviewed. The procedures relating to a membrane based nitrogen generator and to a combustion gases generator are described. The physical properties, practical requirements and economic implications of using different gases is briefly reviewed. Some aspects of the practice as related to mine fires in certain collieries in other countries are dealt with.

Jan 1, 2000

By C. N. Harman

Steel is the most versatile material which has made the progress in every aspect on this earth possible. There are hundreds of varieties of steel because for each application it has to be made with specific properties to get the most optimum usage. It is well known that the basic constituent of steel is iron. But it is the proportion of other elements in it, which give each type of steel certain specific properties. These elements are added in liquid iron inform of Ferro alloys to get the desired composition and properties. Thus, Ferro alloys are important additives in the production of steel. It can be said that no steel can be made without use of one or more of the several Ferro alloys. They form the backbone of steel. Thus, the Ferro alloys industry is vitally linked for its growth and development to that of the steel industry. Ferro alloys industry in India has never been globally competitive, despite its rich ore deposits and low-cost manpower, essentially due to a) Insufficient availability and high cost of electric power b) Increasing ores and reductants cost c) Non-availability of low ash, low phos. coking coal in the country for the production of desired coke with low ash, and low phos. contents, making import of such coke at a high cost imperative d) High-cost and insufficient infrastructural facilities (both road and rail) for rapid transportation of ore from mines to plants e)Stiff competition from producers and exporters of Ferro alloys in other countries like South Africa, Kazakhstan, China, Russia, Australia etc. due to global trade agreement which has made drastic reduction in customs duty on imports necessary. f) Wide fluctuations in the International price of Ferro alloys depending on demand versus supply. To over come these challenges plus adhering to stringent pollution control norms innovations are inevitable in the process technology, and plant equipment design, along with frequent changes in product mix, to be more cost-effective. An attempt is made in this paper to address the innovations that took place in the past and those that further need to be made, considering the future of this industry.

Jan 1, 2007

By W. Stumpf

Mill log analyses and complementary hot deformation studies were carried out on the as-cast structure and on a hot rolled structure of the same low carbon steel (SAE 1006) that had been processed according to the direct or hot charge route in a compact strip plant. The main softening mechanisms during hot rolling were found to be complete dynamic recrystallization during each pass above about 1000°C for the as-cast structure with an austenite grain size of 277µm and, secondly, incomplete static recrystallization after each pass with a finer austenite grain size of about 26 µm and tested below 1000°C. A two-stage hot working mechanism has also been found by others on a similar steel also processed by the hot charge route and this may appear to be a characteristic of this type of material. Constitutive constants determined from hot working studies were combined with other constants from the literature and incorporated into a grain size development model that correctly predicts the final ferrite grain size in the hot rolled strip steel. The predicted incomplete static recrystallization during the last three finishing passes in the plant appears to result in some retained strain in the hot rolled austenite as it transforms to ferrite on the run-out table. Analyses with the model predict relatively little sensitivity of the final ferrite grain size to process and product variables such as temperature and strain per pass for the last three passes and also the starting austenite grain size in the slab. Keywords: Low carbon steel, hot rolling of strip steel, rolling mill log analyses, austenite grain size, ferrite grain size, grain size modelling.

Jan 1, 2003

By A. M. Ghodgaonkar, P. J. Bhonde, R. D. Angal

Primarily ferrochrome is used to introduce chromium into steels and alloys. Chromium enhances hardness, hardenability, corrosion, abrasion and wear resistance of the steel. High carbon ferrochrome is one the cheapest sources of chromium, which finds large consumption in foundries and steel plants. However, carbon leads to problems viz. weld decay and sensitization of steels at elevated temperature causing catastrophic failure. Thus high carbon ferrochrome which otherwise enjoys financial edge over its low carbon grade is not suitable for final alloying or adjustment of chromium content. Subsequently, its addition burdens a steel maker. Hence, metallurgists around the globe have researched on finding out suitable technique for refining of ferrochrome. Traditional production methods of low carbon ferrochrome have drawbacks i.e. high refractory consumption, losses of chromium in slag and fumes etc-. Later these were overcome by adopting relatively new methods namely, metallothermic reduction, triplex process, vacuum technique to directly produce extra low carbon ferrochrome. Authors have carried SWOT analysis of the aforementioned techniques in the literature. Key Words: Ferrochrome, carbon content, low carbon grade, chromite, sensitization

Jan 1, 2007

By S. Sarac

In this study, a statistical model is suggested in order to determine the methane emission from a working seam. In the proposed method, methane concentrations which are systematically measured in return airway are the sample values, and the calculated statistical parameter is the upper confidence limit of the average of these values. At any given time, the probability of methane concentration in the return airflow to be lower than the calculated upper confidence limit value is 97.5%. The statistical method has been applied to the panel 206 of Armutcuk Mine, Turkish Hardcoal Enterprises. The calculated methane emission value for the considered shift was 15.18 m3/t.

Jan 1, 2003

By M. du Plessis

This paper describes the evaluation of a limit equilibrium model to simulate the behaviour of crush pillars in platinum mines. An analytical model was derived to calculate the residual average pillar stress (APS) values of the crush pillars. The values predicted by this model were compared to the numerical values obtained from TEXAN simulations. In general, the limit equilibrium model appears to be very attractive for simulating pillar failure as the gradual crushing of the outside of the pillar and the transfer of stress to the intact core can be replicated. The value of the TEXAN crush pillar model was further demonstrated by simulating an idealized layout with crush pillars between two adjacent panels. The simulations illustrated that oversized pillars will not crush close to the face and this may lead to seismic failure in the back area. An important finding of the study is that closure measurements may prove to be a very valuable diagnostic measure in crush pillars layouts. Distinct differences in magnitudes of closure were simulated for a scenario where the pillars crush as expected, compared to the scenario where an oversized pillar is left. Experimental closure data collected in a crush pillar stope provided further evidence regarding the value of closure measurements in these layouts.

Jan 1, 2011

By A. Burger Pintér

To be meaningful the sharing of ideas about the National Environmental Management Act (NEMA) and social issues within the context of Mining and Metallurgy (M&M) requires an honest scrutiny of the M&M/social environment relationship, both past and present. It is not a secret that this relationship has been and is fraught with difficulties. Thus from all perspectives (M&M, society and environmental and social consultants) such a dissection, that highlights the realities, both good and bad, is uncomfortable. For this section of the colloquium to have any value, the honest but difficult approach needs to be taken.

Jan 1, 2000

By D. Pohl

The past decade has seen rapid expansion in the West African mineral exploration environment. This expansion has been largely driven by changes in ?Political climate ?Fiscal and legal regimes ?Exploration approaches ?West African geology. Major regional mapping and geochemical surveys by the UNDP, and the BRGM in the late 1970s and early 1980s laid the foundation for the rapid development of mineral exploration and resources during the past decade. An additional driving impetus was the discovery by native artisanal miners of many significant new gold occurrences at Libiri, Essakan, Bouda and Tirahori, during the great droughts of the late seventies and early eighties.

Jan 1, 1998

Sishen Iron Ore Mine previously used only A-grade material (>60% Fe in situ value) from the pit for beneficiating in the DMS plant to a final product grade of 66% Fe in lump and 65% Fe fine ore. The B-grade (between 50% and 60% Fe) and C-grade material (between 35% and 50% Fe) were stockpiled separately, owing to the inability of the existing DMS plant to beneficiate material at densities higher than 3600 kg/m3. The ability to beneficiate the B-grade material at densities higher than 3600 kg/m3 was evaluated, and air-pulsed jigs were found to be techno-economically feasible and value maximizing. The beneficiation of B-grade material would add to the existing DMS production of 28 Mt/a, with no additional mining cost and only limited costs for the handling of waste and B-material. The objective of the Sishen Expansion Project (SEP), i.e. the jig plant, was to produce 10 Mt/a of saleable product with six modules to the set physical and chemical specifications by 2009. During the start of construction, it was decided to add another two jig modules to the plant to increase production to 13 Mt/a. During commissioning and ramp-up the shortcomings and advantages of the jigs were fully experienced and understood, resulting in many changes to optimize jigging performance..

Jan 1, 2014

By FJ Fourie

This paper describes the concept and development of the use of a uni-delay shock tube system in the timing and initiation of the development rounds, specifically in flat development. It was extended from stoping and now constitutes the only initiation system is use at Kopanang mine. The two explosives initiation systems in general use in underground mines are the conventional fuse-igniter cord system, and the more modern Long Period Delay shock tube system, better known as the numbered LP system. Both are well accepted but have many drawbacks which can result in poor breaking and substantial wastage of the blasting material. Both of these deficiencies cause an increase in the cost of a blast. Hitherto, the limited number of delays available has complicated the use of shock tubes in development blasting. Over eighteen month period to the end of 2007, a project team comprising members from Kopanang Mine and AEL developed a method for the use of a uni-delay shock tubes to time any development round. These uni-delay shock tubes are better known as Reef Masters® or EZ-Stopers® depending on the supplier, and the system has particular application in flat development. During the project, two new shock tube system components were designed, tested and manufactured; namely Splitters and Starter Packs. The system has been successfully tested and implemented in both on-reef and off-reef development ends. At Kopanang, it has now been rolled out across the entire mine. Other AnglogoldAshanti mines are conducting trials and implementations into production sections. Initial results indicate improvements in the ground conditions and excavation profiles. The cost of blasting is showing a downward trend. The authors consider that the system is a tool for use in further blast optimization and will contribute to rationalization of the explosives commodities basket on mines.

Jan 1, 2008

By V. Labiouse, M. Jaboyedoff

GIS documents are of great interest for a quick and low-cost determination of areas endangered by rockfalls. They allow (i) the detection of potential instabilities from steep slopes and cliff areas, and (ii) the preliminary estimation of potential run-out areas by means of a so-called cone method. After the presentation of the tools used to compute these areas, the paper focuses on two methods developed for a preliminary hazard mapping, one at regional scale and the other at local scale. Mittels GIS-Dokumenten können von Steinschlag bedrohte Gebiete schnell und kostengünstig ermittelt werden. Die sogenannte Kegelmethode erlaubt die Erkennung potentiell instabiler Zonen von Steilhängen und Felswänden sowie eine erste Einschätzung der möglichen Reichweiten. Nach der Vorstellung der zur Berechnung der bedrohten Gebiete benötigten Hilfsmittel stellt der Artikel zwei Methoden zur vorläufigen Gefahrenkartierung in lokalem und regionalem Maßstab vor. Les SIG sont très intéressants pour une détermination rapide et peu onéreuse des zones affectées par des chutes de blocs. Ils permettent une détection des zones potentiellement instables et une estimation sommaire des zones de propagation des blocs par une méthode dite des cônes. Après la description des outils utilisés pour définir ces zones, l’article expose deux méthodologies élaborées pour un zonage préliminaire du danger, l’une à l’échelle régionale et l’autre à l’échelle locale.

Jan 1, 2003

This paper reports on recent field observations on the performance of support systems under different corrosion environments in Canadian underground mines. Phenomenological data are used to gain a better understanding of the main causes of corrosion in underground metal mines. Preliminary field data collected from five metal mines have been complemented by atmospheric and water sample analysis as well as fractography and metallographic studies. This has identified dominant factors that control the corrosion of support systems. The data are analysed in order to develop a support strategy for mines operating in corrosion environments.

Jan 1, 2008

By G. Swan, E. Nordlund, P. Zhang

"SynopsisThe most widely used support design damage criterion for rockburst-prone mines is based upon kinetic energy, which is proportional to the square of the ejection velocity and is commonly expressed in terms of peak particle velocity (PPV). Field monitoring and back-analyses have shown that ejection velocities of the order of 10 m/s and higher can result from seismic events of moderate magnitude. Such velocities are much higher than those predicted using PPV obtained from scaling laws. It has also been found that the peak ground motion (i.e. PPV) on the surface of an excavation is preferentially amplified (by four- to tenfold) compared to the motion in solid rock at a similar distance from the source. However, the wave propagation and interaction processes involved within the fractured rock in generating high ground motion are very complex and are not well understood at this time.In this paper, velocity amplification was investigated by modelling the dynamic interaction between fractured rock and a free surface using a 2D discontinuum-based numerical program, UDEC (Universal Distinct Element Code). A 1D model with a fractured zone was used to represent the fractured rock. Velocity amplification, quantified by PPV, predicted at the free end of the model was 2.0–3.6 times higher than the input velocity. It was found that the wave frequency, fracture stiffness, fracture spacing, and thickness of fractured zone are the main factors that affect the velocity amplification. The results have proved that the interaction of the seismic wave and multiple fractures near the free surface strongly influences the ground motion.IntroductionSince mining-induced seismicity is almost inevitable in deep mines, ground support is generally employed to mitigate the risk of seismically-induced damage. The most widely used support design criterion for seismicallyprone mines is one that seeks to maximize the absorption of the kinetic energy (plus potential energy if a gravity component is considered) of key rock blocks. Based on this criterion, design methods for rock support were first proposed by Wagner (1984) in South Africa and later improved, among others, by Roberts and Brummer (1988) and Kaiser et al. (1996)."

Jan 1, 2015

By P. G. Terrazas Prado

This paper presents the results of research on the development and application of a custom-made truck cycle and delay automated data collection system (TCD-ADCS) in a surface coal mining. Truck cycle and delay field data are locally stored in trucks and then synchronized and replicated through a wireless network into a centralized server containing an already-developed integrated production management system (IPMS). The system relies on motion sensing and distance travelled in order to automatically define the cycle starting/ending points, cycle time, position, and delay time. Connectivity and communication between loading equipment and trucks are also established. Communication between the equipment operators and TCD-ADCS system is via a user-friendly graphic interface. The hardware used for the development of this system consists of a rugged touch-screen personal computer, 2.4 GHz radio transmitter antenna, and a commercial GPS receiver. The system was developed, tested, and deployed at a surface coal mine in the USA. Keywords surface coal mining, truck and shovel, data collection, information systems.

Nov 1, 2013

By K. Ford, R. Urquhart, D. Hobbs

CIS countries are home to some of the world's largest producers of chrome, manganese and silicon ferro alloys and leading suppliers to world export markets. The region's ferro alloys production is rising faster than demand from its domestic steel industry - unit alloy consumption in domestic steelmaking is in fact falling as process efficiencies improve - and there is significant spare capacity available to increase production. CIS producers enjoy certain strategic advantages in the production of ferro alloys - for example, captive ore sup-plies, low power and labour costs - but must also meet certain challenges - such as lower labour productivity and greater distance to market than some of their competitors. CIS producers are ambitious but new investment is needed to upgrade some aging plants and overhaul outdated process technologies if they are to be more competitive with the world's leading producers and address the environmental issues that are now moving up the agenda. This paper describes the structure of the region's ferro alloys industry and discusses its advantages and disadvantages by alloy and by country. It considers how the ongoing process of restructuring and new investment in the industry might move forwards, based on its strengths and weaknesses, technical and environmental factors and the strategies of the main players. It asks how the industry might maximise its substantial potential - in particular, for the production of chrome and manganese ferro alloys - and examines the implications this holds for all global ferro alloys players.

Jan 1, 2007

By M. S. M. Aljuhani

In this paper, one of the human factors that affect productivity in an underground gold mine in Saudi Arabia was investigated and analysed for the purpose of improving productivity. The human factor that was investigated is labour utilization and labour productivity. In the selected mine, labourer?s performances were measured carefully. It was found that in this mine, workers spend only 65% of the shift time in a productive work, and they spend 35% of the shift time in non-productive activities. As a result, recommendations were presented to enhance productivity in the selected underground gold mine by enhancing labour utilization.

Jan 1, 2002

By M. Bwalya, L. Mabokela, L. C. Woollacott

This paper presents a study on the ability of the King stratification modelto describe density stratification patterns that are achieved under idealizedconditions. Tests were conducted in a batch jig using artificial particles inseven density classes. All particles in a density class had essentially thesame density, size, and shape. Tests were conducted for particle systemsinvolving from two to seven components. Good agreement was obtainedbetween measured and modelled data to an extent that gave strongendorsement of the mathematical appropriateness of the core equation inthe King model. Somewhat ambiguous results were found with regard toclaims about the independencies of the single experimentally-determinedparameter required by the model.

Jan 1, 2015

By G. de B. van Niekerk

This paper briefly outlines some mining technology that is used with success in Australia but is not yet fully utilized in South Africa. The following aspects are discussed: improved rotary-drill bit performance, use of trucks and load haul- dump units underground, long-hole raising, blasting techniques, and the use of butterfly roofbolt plates for support.

Jan 1, 1989

By G. Tranell, L. Kolbeinsen, S. Gaal, J. Safarian

The effect of carbon material properties on the rate of MnO reduction from ferromanganese slag by solid graphite was investigated. A sessile drop technique was used to study the reduction rate of a synthetic slag containing 45 wt% MnO at 1500 and 1600 ºC. Different types of graphite substrates were used and the con-tact angle between slag droplets and substrate were measured in-situ. Moreover, the slag droplet volume during the interaction with the graphite substrates was calculated and normalised. The mathematical relationship between the slag density during the reduction and the normalised slag droplet volumes during the reduction were derived and the MnO reduction curves were then calculated. A method for measuring the slag reactivity of solid carbon was defined and used to qualify the propensity of the different graphites to react with the liquid slag. Some supplementary studies such as manganese evaporation measurement and EPMA analysis for determining the extent of MnO reduction were also carried out. It was observed that there is nota significant difference in the wetting angle of the graphite substrates by the slag, and the wetting is not changed within the temperature range of 1500-1600ºC. However, the changes in the contact angle during the slag reduction at 1600ºC are more than at 1500ºC. The kinetics of MnO reduction is dependent on the type of graphite and it is more dependent on the graphite properties at lower temperatures. On the other hand, the dominant properties of graphite on the reduction rate vary with temperature. A multivariate analysis on the graphite properties and the parameters related to the slag reactivity indicated that the kinetics of MnO reduction is mainly dependent on the temperature, and then on the graphite properties. It was also found that at1500 ºC the surface area and the CO2 reactivity are the most important graphite properties for the slag reduction, suggesting that the reactivity of carbon is rate controlling at 1500 ºC. However, the porosity related parameters are the most important graphite properties at 1600 ºC, suggesting that CO gas desorption is rate controlling at high temperatures.

Jan 1, 2007