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By M. O. Makwarela, M. W. Erwee, K. Bisaka

"Energy efficiency in mining and minerals processing forms part of Mintek’s long-term research strategy which includes a specific programme designed at overcoming the challenges faced by the South African pyrometallurgy industry.The electric smelting industry is currently severely constrained by the global economic downturn as well as by the availability and increasing cost of electricity. Efficient utilisation of electricity through energy recovery systems and improved smelting process flowsheets can significantly contribute towards creating sustainable operations.Apart from efficient engineering design and solid process control, smelting of either cold or hot pre-reduced ores has been shown to decrease furnace electricity consumption by more than 40%. Various methods of solid-state reduction tests have been carried out at Mintek in order to select the most appropriate process option in the context of the South African industry. This paper summarises a subset of the results obtained, specifically on pre-reduction tests done on South African chromite and manganese ore pellets.In this set of tests, it was found that the use of an organic binder, together with B2O3 as flux, promotes manganese ore pre-reduction, but retards the pre-reduction of chromite. By pre-reducing the manganese ore feed, significant cost savings can be achieved in subsequent smelting processes and there is potential to minimise manganese losses as a result of fuming, due to possible lower operating temperatures."

Jan 1, 2016

By P. O. Sandvik, George Erdosh

"AbstractThe Cargill phosphate deposit, located 32 kilometers southwest of Kapuskasing, Ontario, was discovered by the Resource Development Group of International Minerals & Chemical Corporation in 1975 and has been evaluated through an extensive program of 190 drill holes, numerous chemical analyses, metallurgical tests, and engineering and economic studies.The Cargill alkalic complex, comprising principally car-bonatite and pyroxenite-amphibolite rocks, was intruded in to the rift system of the Kapuskasing High during late Precambrian time about 1,800 million year s ago, near the intersection of northeast- and northwest- trending faults. The Cargill complex is one of at least ten known alkalic complexes in or close to the Kapuskasing magnetic-gravity-high system and is expressed by an elongated, northeast- oriented, three-part magnetic anomaly 7.2 kilometers long by 2.8 kilometers wide . Weathering and leaching under assumed temperate to cool, moist climatic conditions , and controlled by faulting, shearing and/or initial petrographic variations within the carbonatite , developed a small, locally confined karst system in the car bonatite rocks and resulted in a thick enriched leached carbonatite zone, capped by troughs and sinks, filled with a residuum of apatite, goethite, clay and other minerals stable in the near -surface, oxidizing environment. Overburden is 5 to 165 meters thick."

Jan 1, 1977

"As mine head grades decline and orebodies become more complex, traditional mineral processing techniques and flowsheets to achieve saleable concentrate become more difficult to design and construct. Mines with lower quality concentrates or concentrates with penalty elements are particular under threat. The economics of these operations are far more susceptible to metal price, concentrate treatment terms and the availability of other, cleaner concentrates. Additional value may be realised for these orebodies through improved recovery by producing a low grade middling concentrate for further processing, in conjunction with a saleable concentrate.The most cost effective way to reduce impurity levels is to do so as early as possible in the mining value chain. Technologies such as fine grinding and fine particle flotation are well established as effective methods for impurity rejection in mineral processing. What is normally overlooked is how a hydrometallurgical process could also be integrated in the overall flowsheet to achieve higher overall recovery at the mill. In the base metals environment, this is mainly because hydrometallurgical processes are associated with production of metal or use of expensive and toxic precipitating agents once the minerals of interest are solubilised. These processes can be very expensive, particularly with rising power costs and poor economies of scale in capital costs associated with low production rates from middling streams.Glencore Technology (GT) has recent experience in the treatment of middling and low grade concentrate streams as well as tailings streams to compliment a concentrator flowsheet in a refractory gold and base metals setting. The value proposition is the isolation of a low grade middlings concentrate from the primary circuit or the tailings stream for upgrading to an intermediate product with an equal or higher grade than the primary concentrate to allow blending for sale. This allows plants to operate on a more favourable part grade-recovery curve while avoiding the expense of metal production. For existing operations this is particularly attractive since it can be added on with no process interruptions.Two case studies are examined showing flowsheets and costings to arrive at the value proposition of the GT low grade treatment flowsheet."

Jan 1, 2017

"IntroductionIn the 1970s, environmental concerns and associated liabilities were a new and unknown aspect of corporate risk. Today, social concerns and the associated conflicts that they can generate constitute a rapidly expanding aspect of risk. Although not a new phenomena — the Bougainville copper mine was forced into closure in 1988 — social risk has emerged as considerably more important, and increasingly visible, in the last few years. Social risk is now an aspect of all mining activities which needs to be calculated into project assessments, and to be managed throughout the life of a project. While social risk has a number of aspects at the corporate level, such as company image and shareholder relations, at the level of the individual project, its primary component is social acceptability, and the principal tool for managing it is the Social Licence to Operate.Social Risk in Latin AmericaThroughout Latin America there are newly modernized mineral codes and economic systems introduced over the last ten years which, together with new environmental legislation, look very much like regulations in developed countries. To the corporations, the existence of these instruments means that the risks from the environmental issues associated with the project are known; they are legislated, defined, quantifiable and hence manageable.It seems ironic that, just when comprehensive regulations for the environmental management of mining have been put in place throughout Latin America, there arise an increasing number of challenges to mining activities. For, in spite of the apparent guarantees provided by these new legislative reforms, communities in Latin America today are more frequently standing up and taking exception to the presence of mining companies, or the ways in which the companies are conducting themselves. The viability of projects becomes threatened because they are considered socially unacceptable, a phenomenon that we describe as social risk. These challenges are less about opposing mining activities than many people would think. Rather, they are based on an increasing desire on the part of the local population to have some measure of control over their own future, and to participate in the development process from the earliest stages."

Jan 1, 2000

By D. Haraguchi, S. Izawa, C. Tokoro, S. Owada

"Arsenic is widely known as a toxic element for humans, animals and plants. Because of more stringent wastewater standards not only in Japan but also around the world, research for appropriate and efficient treatment method for arsenic is becoming increasingly important. Coprecipitation or adsorption process using ferrihydrite is widely implemented for dilute As(V) removal from wastewater. In this study, the sorption mechanism of dilute As(V) with ferrihydrite in coprecipitation or adsorption process was investigated. To accomplish this, we conducted batch experiments of coprecipitation or adsorption and compared these results for sorption isotherm and zeta potential. These experimental results showed that sorption mechanism in coprecipitation process depends on the initial As/Fe molar ratio; simple twodimensional adsorption onto the surface of ferrihydrite when the initial As/Fe molar ratio was < 0.4, and some three-dimensional uptake with ferrihydrite when it was = 0.4. We also evaluated the sorption mechanim by analysis of X-ray diffraction (XRD) and X-ray Absorption Fine Structure (XAFS). XRD or XAFS spectra showed that surface precipitation of amorphous ferric arsenate was formed when the initial as/Fe molar ratio was = 0.4, beyond the thermodynamic bulk precipitation range for ferric arsenate.INTRODUCTIONArsenic is toxic to animals, including humans, and long-term exposure to arsenic via drinkingwater causes cancer of the skin, lungs, urinary bladder, and kidneys, as well as other effects on the skin such as changes in pigmentation and thickening (Ghosha et al., 2008). Elevated levels of arsenic are often present in the environment as a result of the weathering and dissolution of minerals as well as in response to numerous anthropogenic sources including the discharge of mine wastes, coal fly ash and the use of pesticides that contain arsenic (Nriagu, 1994; Singh et al., 2007). Indeed, the potential for arsenic exposure affects many people, as evidenced by several million people in Bangladesh and India being at risk of exposure via drinking water obtained from contaminated groundwater sources (Ahmed, 2001).Acid mine drainage (AMD) containing arsenic is a global environmental problem (Dold, 2008; Liang and Thomson, 2008) that also affects Japan, which has many abandoned or closed mines that have been generating AMD for the last few decades (Masuda et al., 2008). Several such facilities in Japan produce AMD containing dilute concentrations of arsenic that exceed Japanese effluent standards (0.1 mg/dm3) (METI, 2006). For example, AMD from the abandoned Horobetsu sulfur mine, the largest AMD source in Japan, contains approximately 10 mg/dm3 arsenic."

Jan 1, 2012

By R. K. Kandasami

"Naturally occurring geomaterials such as sandstone, limestone and other soft rocks, residual soils are composed of a particulates held together through a cohesive matrix, usually composed of argillaceous or siliceous cementing agents. Geo-materials such as these have been reconstituted in the laboratory using ordinary Portland cement in lieu of the naturally occurring cohesive matrix, in addition to using sand particulates. This cohesive frictional granular ensemble is an ideal model material for understanding the mechanical behaviour of transitional geomaterials such as soft rocks. An important consequence of this cohesion that pervades the inter particulate system is the enhanced tensile strength when compared to a purely granular ensemble. The assessment of strength of these soft rocks and cemented sands is often understood in the framework of continuum mechanics, i.e. considering the cemented sand to be a continuum, and performing simple elemental tests such as uniaxial compression or tension tests. A simple model to describe the behaviour of these cemented sands has been to use elements such as springs, sliders, and dashpots in parallel to describe the existence of a cohesive and frictional component of strength (Jiang et al. 2007). In the framework of continuum mechanics, the mechanical response of these cemented sands have been modeled using traditional plasticity theory, for example utilizing variants of the traditional Mohr Coulomb model, Modified cam clay (Sun and Matsuoka 1999) etc. The typical sand models are amended to include the effects of cohesion, as proposed by Lagoia and Nova (1995).The mechanical response of cemented sands is understood to be transitional to the behaviour of a typical particulate assemblage and a quasi-brittle material. However, the effect of length scale in these material systems has not been investigated. This paper presents a series of uniaxial compression experiments conducted on weakly cemented sand specimens of various sizes. The effect of length scale in these weakly cemented sands is investigated through unconfined compression tests."

Jan 1, 2015

By Qing-hua Tian, Li-then Cheng, Xue-yi Guo

In order to recycle valuable metals from silver separated residue, a novel method using alkaline smelting at low temperature was proposed. The main factors affecting the main metal recovery such as the smelting temperature, smelting time, liquid-to-solid ratio and alkali addition were investigated comprehensively. The behavior of the main metal elements, such as Pb, Sn, Sb and Bi in silver separated residue was also discussed. The results indicated that amphoteric metals such as Pb and Sn can be smelted into the melt, while other metal elements, such as Sb and Bi were left in the residue.

Jan 1, 2011

By T. Johnson, K. Lambrych, D. Kelley

Materials for construction of equipment used in hydrometallurgical plants are selected based on a combination of their ability to perform as required in aggressive process environments as well as their cost. As a material of construction, fiber reinforced plastic (FRP) has been shown to provide equal if not improved durability relative to alternative materials such as corrosion resistant alloys at a considerably lower cost. This is particularly true in the case of equipment used in acid leaching processes for copper, cobalt, nickel and rare earth elements. The selection and extensive use of FRP over alloys in new hydromet plant construction in North and South America illustrates this advantage of FRP effectively. This paper will compare corrosion performance and cost of plant equipment fabricated with stainless steel alloys and FRP made with Epoxy Vinyl Ester thermoset resins. Real world case histories for FRP piping, storage tanks, extraction vessels, and electrowinning cells combined with laboratory based corrosion studies will be reviewed to demonstrate how FRP materials are selected for hydrometallurgical equipment.

Jan 1, 2015

By L. Kong, V. G. Papangelakis, L. Li

"The Eh-pH diagram of lithium-titanium-water system at 25°C, 100 °C and 200 °C was constructed. It shows that there exist thermodynamic stability areas of Li2TiO3. This indicates a thermodynamic possibility for the formation of Li2TiO3 in aqueous solution. A hydrothermal process has been applied for the preparation of Li2TiO3 using TiCl4 and LiOH•H2O as raw materials. The prepared samples were examined with X-ray diffraction, scanning electron microscopy and thermo-gravimetric analysis and differential scanning calorimetry. The results show that temperature and washing condition have significant effects on the phase composition of the product. Phase-pure Li2TiO3 powders were obtained at 200°C with Li:Ti molar ratio of 2.0.INTRODUCTIONLithium-containing ceramics enriched in 6Li, such as Li2O, LiAlO2, Li4SiO4, Li2ZrO3 and Li2TiO3, are considered as tritium breeding materials (Saito et al., 1998; Roux et al., 1998; Johnson et al., 1998; Hoshino et al., 2002). In view of its admirable properties: low-activation, good thermal stability and thermal conductivity, excellent tritium release performance and reasonable lithium atom density (Kopasz et al., 1994; Roux et al., 1996; Saito et al., 1998; Wu et al., 2008), Li2TiO3 is recognized as one of the most promising candidates of tritium breeding materials. Meanwhile, Li2TiO3, as the precursor of H2TiO3-type lithium absorbent, receives more attention as the development of extracting lithium from salt lakes (Zhong, 2004; Zhang, 2010).Several synthetic techniques have been applied to prepare Li2TiO3 powders, such as solid-state methods (Lulewicz and Roux, 2002; Ramaraghavulu et al., 2011; Mandal et al., 2012), sol-gel processes (Deptula et al., 2002; Lee, 2008) and solution combustion routes (Cruz et al., 2006; Jung et al., 2006; Sinha et al., 2010). A solid-state method may produce a series of problems, including impurity contamination and difficulty in morphology control of the obtained powders, although the process involved is simple. The solgel process is prolonged and usually demands for multi-step reactions, while solution combustion route requires plenty of energy and easily causes product contamination by the fuel used. Owing to its environmentally benign and highly suitable characteristics in fabricating materials, hydrothermal technology has been widely used and became a powerful tool in the field of material synthesis (Yoshimura and Byrappa, 2008). For example, ZnO in the form of bulk single crystals, fine particles and thin films, which is an attractive photoelectric material, was successfully synthesized by hydrothermal process (Sekiguchi et al., 2000; Ohshima et al., 2004). A hydrothermal technique was also used to the preparation of carbon nanotube, which possesses outstanding mechanical, structural and electric properties (Bernholc et al., 1997), and is superior to the commonly used method (Gogotsi and Libera, 2000). There, it provides an option for preparing Li2TiO3. Laumann et al. (Laumann et al., 2010) synthesized cubic a-Li2TiO3 by hydrothermal reaction at 180 °C for 18 h, using TiO2 powder, comprising of anatase and rutile, and lithium hydroxide in de-ionized water. However, the prepared a-Li2TiO3 is extremely unstable with a maximum lithium loss of 75% when treated in bathing experiment."

Jan 1, 2012

By J. G. Kim, B. G. Chae, D. S. Cheon, E. S. Park

The underground structures such as high-level radioactive waste disposal thermal energy storage should be designed and constructed considering thermal-mechanical characterization because of long term and/or cyclic thermal stress. High temperature changes in these structures can extend the existing cracks and generate new cracks in surrounding rock mass. In case of long term and/or cyclic thermal stress conditions, it is possible to lose the function of structures caused by the significant cracks and fracture growth in the rock mass. In this study, the critical thermal crack temperature of the granite, limestone and thermal Kaiser effect were evaluated. Experiments were carried out with the heating speed of 1.5?/min. To avoid thermal shock and target temperatures were set at 150? and 250?. In order to verify the thermal Kaiser effect, the samples were heated by 150 ? after 2-3 repetition to 250?. The generation and growth of cracks were observed through an acoustic emission measuring system. The variation of the physical rock properties was measured before and after thermal experiments. After compared with the thermal experiments using PFC2D, numerical simulations were carried out at higher temperatures (400?). The experiments showed that the initial thermal crack temperature of granite and limestone is about 35?, 32? and the critical thermal crack temperature were about 69? , and 49? , respectively. The experiments confirmed the thermal Kaiser effect of experimented granite and limestone due to thermal cyclic loading. From the numerical analysis, the critical crack temperature showed the same tendency as the thermal experiments. The P and S wave velocity of the sample after the experiment were reduced. Therefore, when heat is applied in long-term and repetitive conditions, these cracks may affect the function and stability of the underground structure. Therefore, further studies of thermal stress effects should be performed.

Jan 1, 2015

By Zhibao Li, Kunming Zhai, Yan Zhang

The hydration kinetics of MgO, namely magnesia or magnesium oxide, obtained by calcination of magnesite MgCO3 or synthetic MgCO3·3H2O has been studied. Nesquehonite (MgCO3·3H2O) was prepared by the reaction of MgCl2 with Na2CO3 in a mixed-suspension mixed-product removal (MSMPR) crystallizer at 40 °C. Three magnesium oxide samples were obtained by calcination of magnesite MgCO3 or synthetic MgCO3·3H2O in muffle furnace at 900, 1100 and 1300 °C for 3 h, respectively. The hydration experiments of MgO samples were investigated at 25, 35 and 45 °C for 24 h in a stirred batch reactor. The hydration results indicate that the rate and extent of hydration of magnesia decreased remarkably with hydration temperature and increased with decreasing calcination temperature at a constant hydration temperature. The whole hydration reaction of magnesia was supposed to experience the promotive period and declining period. An empirical kinetic model ( k t p -?ln(1-??) ??) and a modification of the classical shrinking core model for diffusion control ( k t b d -?-?3 2 ????1 [1 (1 ??) ] ) have been applied to fit the experimental data of hydration in two stages, respectively. The values of kinetic parameters ( p k and d k ) were obtained by regression analysis and the activation energy of the sample at 900 °C was estimated to be 34.23 kJ/mol. The comparison between MgO from calcination of synthetic MgCO3·3H2O and a commercial MgO used in silicon steel production was carried out, indicating that special silicon steel grade MgO can be obtained by calcination of MgCO3·3H2O below 900 °C.

Jan 1, 2014

By S. C. Robinson

"IntroductionALTHOUGH most uranium deposits of the Canadian Shield lie along its western and southern margins, those of the Lake Athabasca region extend easterly along the north shore of the lake and beyond to Charlebois lake. The western end of this belt of deposits, in the vicinity of Goldfields, is 80 miles from the Palaeozoic contact, and its eastern end, at Charlebois lake, is 240 miles from the nearest Palaeozoic rocks.Deposits in this belt may be grouped in four districts, which are, from west to east:(1) The Goldfields district, an area approximately 20 miles square, centred on Beaverlodge lake and extending eastward from St. Joseph's point to Moose channel.(2) A small area in the vicinity of Sucker bay, which is about l0 miles east of Fond du Lac.(3) An area including Middle lake to the northwest shore of Black lake at the Nisto mine.(4) A fairly large area extending northward from the eastern end of Black lake, through Charlebois lake to Spreckley lake.HistoryThe region has stimulated interest in mining circles since the reconnaissance survey of J. B. Tyrrell of the Geological Survey of Canada in l893, who reported concentrations of iron along the north shore of lake Athabasca. The deposits were staked and re-staked up to the early 'twenties' but are too lean to form ore."

Jan 1, 1952

By D. Campbell

Mining activity is increasing in northern boreal and subarctic regions of Canada. This is the case in the far north of Ontario, especially in and near the Hudson Bay Lowland (HBL). De Beers Canada opened the Victor diamond mine in the centre of the HBL in 2008, and advanced exploration and impact assessments are occurring to the west in the ?Ring of Fire? for ferrochrome, nickel/copper, iron/ vanadium and platinum-group elements, making it one of the richest mineral finds in Canada in recent years. However, the HBL is also a near-pristine, sensitive environment. Its peatlands forms the third largest wetland in the world and are globally important stores of terrestrial carbon. Human populations in the region are sparse, consisting almost entirely of First Nations communities. Local First Nations also have a strong land ethic and greatly influence mining developments. Through formal agreements, they have insisted on a gold standard for environmental management, including a small mine footprint and the return to representative native ecosystems after mine closure. However, knowledge on the revegetation of subarctic and northern boreal ecosystems is limited. Here, we are conducting research at the Victor mine to develop gold standard protocols for the revegetation of disturbed peatlands and mine waste uplands and present a summary of results. We first tested existing protocols for peatland restoration from southeastern Canada. We collected peat-forming plants from nearby muskeg, spread them sparsely over disturbed peatlands and applied a light phosphate fertilizer, but unlike southern protocols, no mulch appeared to be required to produce a representative cover of peat-forming plants within three years. A bigger challenge is the reclamation of uplands made of mine waste back to representative ecosystems. We first characterized reference conditions for uplands in the HBL, which are scarce in the region. Nearby natural uplands were divided into two classes, interior uplands and uplands along river valleys. Multiple parameters were examined at these sites including soil development, bulk density, soil chemistry in the rooting horizons, plant cover by stratum, plant species composition and dead wood. The mean condition and, more importantly, the range of these parameters allow us to set broad targets for progressive reclamation, which will facilitate success. Finally, we characterized local upland plant species through their functional traits to determine their likely abilities to colonize, grow and contribute to ecosystem processes. A classification of species by these simple functional attributes will help restoration managers to select candidate species to meet different goals at different successional stages (i.e. good versus poor dispersers or establishers). Research into these protocols remain in the early stages, but show promise that gold standards can be achieved to ensure that mining wastes can be reclaimed to productive ecosystems.

Aug 1, 2013

By Pierre Choquet

"The whole work carried out both in situ and in laboratory by a research group of the West German collieries is presented. This work has led to a design method of steel arch supports for gate roadways that gives full satisfaction in this particular coalfield. The method accounts for mining depth, the mining system (advancing or retreating), thickness of the coal seam and other parameters.Full statistics are then given on gate roadway supports of the ECCS (European Community for Coal and Steel) coalfields. They were collected by the author in order to show that the West German method can be applied to other coalfields as the long wall systems which are generally being used are very similar. Design calculations are conducted for each coalfield&apos;s case. They show that the method would have been able to predict in most cases the support actually used.Utilization of the design method is recommended to the Cape Breton Development Corporation &apos;s mine operators because mining conditions, even though different from European ones, present a number of similarities which make it possible to apply the design method to their particular case.This procedure might be profitable in mines facing support problems in their levels and for any planning of future projects"

Jan 1, 1986

By K. Mirkhani, P. Gebski, W. Ying

The campaign life of an industrial metallurgical vessels strongly relies on the quality and quantity of the refractory lining. An operating furnace or converter refractory lining can be assessed either by thermal modeling or by acousto ultrasonic-echo (AU-E) technique or a combination. AU-E is a Non-Destructive Testing (NDT) stress wave propagation technique that has been utilized on a wide variety of smelting vessels for over 12 years with good success. AU-E can determine the thickness of remaining refractory lining, estimate the thickness of build-up or accretion, detect and locate metal penetration and impregnation into the lining, and identify hydrated or cracked areas of refractory. This paper details the AU-E principles, equipment and recent improvements to the data analysis to further improve speed and accuracy. In addition, the paper discusses the AU-E accuracy and limitations through a diverse and vast array of practical examples including a comparison with thermal modeling and physical measurements.

Jan 1, 2011

By R H. Hallam

The Mattagami mining district encompasses a favour-?able belt of folded Keewatin-type rocks, with intercalated sediments and intrusives of late Keewatin age. This environment has been subjected to periods of basic and acidic intrusion. The orebodies lie within the fold structure and are associated with faulting and shearing of considerable magnitude. The No. 1 orebody contains 60 to 70 per cent massive sulphides. The minerals, in their order of abundance, are generally: pyrite, sphalerite, pyrrhotite, magnetite and chalcopyrite. It is evident that the broad geological structure of the district is amenable to ore deposition. There are two ? prominent linear expressions which comprise this broad structure. Both strike directions lie at the edge of, or are related to, a complex gabbro-anorthosite-peridotite zone. The fact that eleven of the ore zones discovered to date coincide with the broad structure indicates its over-all importance. It is estimated that the production from Mattagami Lake Mines will be in the range of 600 to 700 tons of zinc concentrate and 70 tons of copper concentrate per day.

Jan 1, 1964

By Alan D. Curtis

A standard planning block model for Phelps Dodge North America Operations has been developed to improve mine planning efficiency and performance in a skill starved environment. The model saves time on software management and training, consolidates data and standard information/output, enhances evaluation and strategic process, and improves communication between sites.

May 1, 2007

By R. J. Chase, C. Davies

"Abstract- The Merelani graphite-tanzanite deposit is located in northeast Tanzania, 14 kilometers south of Kilirnajaro International Airport and in close proximity to the towns of Moshi and Arusha . The graphite mineralization is hosted by relatively undeformed linear Proterowic metasedimentary gneisses, several of which have been subjected to hydrothermal alteration resulting in tanzanite mineralization. Exploration work comprised detailed geological mapping coupled with pit and trench channel sampling and a subsequent 1500 meters of diamond drilling. In addition, metallurgical tests have shown the graphite to be of unusually coarse flake size, crystallinity and high purity.Feasibility studies have shown the economic viability of a major coarse flake graphite deposit with the measured resource to 50 meters in excess of 9 million tonnes assaying over 8o/o graphitic carbon . Production is due to start by the end of the first quarter of 1994 with the processing plant design capacity initially set at 15 000 tonnes per annum.ln addition to graphite production, tanzanite will be produced through selective mining within the graphite open pit in the upper horizon and from underground workings within the lower horizon.The Merelani graphite-tanzanite deposit will be the first major orebody to be exploited through means of private funding since Tanzania gained independence."

Jan 1, 1994

By Christoph Miller

About 80 years ago the mining industry saw an advertisement of a machine manufacturer: ?One man ? one machine?, meaning the productivity gain by using a pneumatic rock drill instead of manual tools. Mechanization in mining had started. In the 1950&apos;s and 1960&apos;s when mechanization progressed the word could be transformed into the meaning of ?one man ? one drill rig?. During the 80&apos;s automatic functions were added to the machines. Automation started. In the 90&apos;s, the first autonomous machines were seen, transforming the advertisement from the 1920&apos;s into ?one man ? multiple machines? operated from a remote control room. Soon, the productivity gain achieved by pure automation will also be flating out meaning that the margin cost of further productivity gain will be inefficiently high. What next? In mining operations there is still a high potential of unused productivity lost by ?trivial? things like organization, logistics and operational management. Changing the focus from mechanization and automation towards optimizing the overall mining process will unleash another big potential for cost cuttings and for enhancing efficiency of production. Optimizing an overall process is a task of much higher total complexity compared to an isolated machine automation focus. And a successful process integration requires the collaboration of machine vendors, infrastructure suppliers, IT services and the mine itself. It requires a number of of important preconditions to be fulfilled: ? Integrated IT systems with seamless interfaces between all components and peripherals involved ? Real time information access in all locations ? Real time overview of all operational aspects A crucial aspect for all of these issues is a seamless communication both above and also under ground and IT interfaces which are easy and price efficient to implement. This paper highlights ways to achieve productivity gains by process optimization. It also discusses needs for industry wide activities in order to enable cost efficient performance of mine process optimization projects.

Oct 1, 2009

By Xiang-dong and Zhu, Xia-jie Hao, Yi-lin Fan, Quan Jiang, Lian-xing Hu, Xia-Ting Feng, Shao-jun Li

"Columnar jointed basalt (CJB), which typically originates from lava flows, is characterized by a special geological structure. The joint network inside the CJB is self-organized into a rough hexagonal arrangement. The field test and measurement during the unloading excavation showed that the columnar joint sets and other internal joint sets not only are important for determining the mechanical properties of the CJB, but also induced its asymmetric unloading deformation and failure. A constitutive model, which considered mechanical deterioration of both the joint sets and rock blocks, was also developed to simulate the unloading behaviour of the CJB. The crack-confinement supporting method for surrounding CJB was developed to overcome the failure of columnar jointed rock mass in the diversion tunnel. Application to the CJB segments of the diversion tunnels in the Baihetan project indicated that this supporting method was reasonable and efficient. INTRODUCTIONColumnar jointed basalt (CJB) rock mass, which typically originates from lava flow, is characterized by a special joint structure. The joint network of the CJB is self-organized into a roughly hexagonal arrangement and leaves behind an ordered colonnade. The widely accepted current view regarding the formation of columnar jointing involves a thermally induced contraction–cooling mechanism (Peck and Minakami, 1968; Degraff and Aydin, 1987; Budkewitsch and Robin, 1994; Lore et al., 2000; Goehring et al., 2006). Although the columnar basalt formation mechanism is fairly understood, the geotechnical characteristics of such rock mass are not well established. In practice, joint sets always induce the multi- failure modes of surrounding rock in the tunneling space (Ibarra et al., 1996; Waltham and Swift, 2004; Mahendra and Bhawani, 2008).According to conventional wisdom in rock mechanics, structural joints affect the mechanical response of rock mass by introducing strong anisotropic effects (Barton and Bandis, 1980; Hudson and Priest, 1983; Brady and Brown, 1985). The columnar jointed rock mass should be considered an anisotropic material given that the joint sets are distributed with some principal directions and characteristic spacing distributions (Cundall and Fairhurst, 1987; Hoek et al., 1998; Wu and Wang, 2001; Budetta and Nappi, 2011; Fortsakis et al.,2012). Columnar jointed rock mass would result in structurally controlled failure patterns, even serious disasters during underground excavation because of the low shear and tensile strengths of intensely joints (Gencer,1985 ;Ishida and Uchita, 2000; Jia and Tang, 2008). The CJB rock mass in the Baihetan hydropower station has exhibited serious stability issues, including sliding, fracturing and even collapse (Shi et al.,2008). Therefore, the geotechnical and geomechanical characteristics of such rock mass should be assessed through in situ investigation and numerical analysis to minimize future accidents during underground unloading excavation."

Jan 1, 2015