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By Kedikilwe Oageng

Effective perimeter control during drilling and blasting is critical not only to blasting results but also to the overall stability of the pit over its entire life span. A pit where perimeter control is not given enough attention when conducting drilling and blasting operations, often experiences over-break or back break beyond final pit wall limits, and therefore has a relatively high probability of failure. Such a pit also becomes unsafe, sometimes not easily accessible, has increased loading costs due to production of oversize, longer cycle times and often problems are encountered when blasting subsequent benches. All these are undesirable consequences, which have negative cost implications. Specialised blasting techniques such as trim blasting and pre-splitting have over the years proved to be effective perimeter control measures. However, the success of these techniques is directly attributable to the time and effort given to the processes. This paper presents results of a project undertaken to monitor, review and optimize the trim blasting and pre-splitting processes at Orapa Diamond Mine in Botswana. The project was specifically incepted to improve the final wall conditions, which continued to deteriorate due to persistent over-break during blasting. The paper also analyses the results obtained against a benchmark of results taken prior to project implementation. Specific blast design parameters which are critical to blasting results were identified as problem areas after auditing of the pre-implementation drilling and blasting practices. These include drill-hole depth, spacing, splitting factor for pre-splits and timing of trim blasts. The impact of different rock types on the results was also studied, and recommendations were made at different phases of the project and results obtained after implementation analysed until optimum results were achieved.

Jan 1, 2008

By Gy. Deák

The Romanian mining industry, especially salt mining, is going through a restructuring phase taking into account the Environment Acquis of the European Union1. In order to preserve the centuries-old salt mines and to develop new ones, in the same salt rock deposit, the long term stability assessment of the saline complex is very important. This case study refers to the Praid salt mine, which includes old salt mines, with impressive sizes, located above the new mines, with activity in progress, in order to provide the means and solutions for efficient conservation and sustainable exploitation for the salt resources. The DKRControl method and FLAC 3D code were used in order to assess the confidence level for the computed prediction of the stability of the salt mine complex salt.

Jan 1, 2008

By A. C. Smith

Although it is only utilized in a few U.S. longwall mines, a bleederless ventilation system can be an effective spontaneous combustion control method in mines with a demonstrated history of spontaneous combustion. In order to provide insights for the optimization of bleederless ventilation systems for U. S. underground coal mines, a computational fluid dynamics (CFD) study was conducted to model the spontaneous heating in longwall gob areas with a bleederless ventilation system. A single longwall panel with a bleederless ventilation system was simulated, and typical ventilation data for a longwall mine was used in the simulations. The permeability and porosity profiles for the longwall gob were estimated using a geotechnical model and were used as inputs for the CFD modeling. The effects of gob permeability and resistance of the collapsed entries on the spontaneous heating were studied. The effectiveness of nitrogen injection to prevent spontaneous heating in the gob was also examined. Disclaimer: The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health.

Jan 1, 2008

The fluorspar deposits at Okorusu, Namibia are closely related to an alkaline igneous ring complex of late Cretaceous age (125¦7 Ma). The fluorite ores consist of relatively fine-grained purple replacement fluorite and subsequent coarser-grained purple and green vug-filling fluorite crystals. Homogenisation temperature measurements for 38 primary fluid inclusions shows that main stage purple to green fluorite crystals were deposited over a temperature range from 166¦C to 144¦C, and minor late yellow fluorite was deposited at lower temperatures from 132¦C to 128¦C. Homogenisation and freezing temperatures measured for 18 primary fluid inclusions shows that the fluorite-depositing fluids were less saline than Mississippi Valley-Type (MVT) ore fluids and overlap the lower temperature range of fluids that deposited epithermal ore deposits. Mining in three open pits (A, B and C) at Okorusu has gradually provided exposures which reveal that the fluorite orebodies have been emplaced primarily by the preferential replacement of carbonatites. Evidence for the replacement of carbonatite includes: replacement remnants of carbonatite within the fluorite ores; goethite pseudomorphs after the carbonatite minerals, pyroxene, pyrrhotite and magnetite, which are disseminated in the fluorite ores; andpartial replacement by fluorite of a large sill-like carbonatite body in the A pit. Electron microprobe analyses of minerals in unreplaced portions of the carbonatites show that their mineralogy consists of titaniferous magnetite, diopside pyroxene, apatite, biotite and calcite. Magnetite contains 6.97 per cent to 10.46 per cent TiO2, averages 8.44 per cent TiO2, and has an average V2O3 content of 0.35 per cent. At high magnifications under the scanning electron microscope (SEM), the magnetite shows abundant fine ulv÷spinel exsolution lamellae arranged in a cloth texture. Apatite contains moderately high fluorine contents that range from 3.21 to 5.0 per cent and average 4.2 per cent, and apatite crystals range in total rare earth oxides from 1.7 per cent to 2.61 per cent. Pyroxenes in the carbonatites are iron-rich diopside, and they contrast to pyroxenes in the fenites that are aegirine-augite. All of the microprobe analyses for mica crystals in the carbonatites give biotite compositions. Microscopic examination of fluorite concentrates from Okorusu provides mineralogical information important to the resolution of beneficiation problems. Fluorite ores that are related to carbonatites are typically accompanied by phosphorus benefication problems. The cause for the presence of phosphate in some of the Okorusu fluorite concentrates is a function of the presence of binary locked fluorite-apatite particles. The fluorite ores have also replaced marble locally in the A pit, especially along the A band in the B pit, and dominantly in the orebody proposed for the new C pit. Those ores are characterised by fine grain sizes, faint remnant bedding, lack of carbonatite mineral pseudomorphs and local presence of remnants of unreplaced marble. Concentrates derived from those fluorite ores are devoid of phosphorus, but commonly have elevated silica contents due the presence of free quartz. Carbonatite and marble were preferentially replaced by fluorite because the calcite was readily soluble in the presence of the fluorite-depositing fluids and the dissolution of calcite provided calcium for the formation of fluorite. 

Jan 1, 2008

By B Ascott

As a prerequisite to achieving integrated regional production reporting across multiple sites, Newmont Australia initiated a project to standardise the configuration and use of mine control systems at three underground sites. This paper outlines the project and considers the outcomes which, in a number of cases, have exceeded the original objectives.

Jan 1, 2008

By T Vizcarra, G Sandoval, C L. Evans

One of the challenges in the development of mineral processing simulators is modelling the liberation characteristics of particles produced by comminution circuits. Understanding the mineral characteristics of these particles is one of the keys to predicting their behaviour in separation circuits. While more fundamental research seeks to model the non-random breakage of ores this work examines whether we can move forward now by using observed characteristics of ores to model the composition of particles generated in comminution processes. Several researchers have noted the similarity of the liberation characteristics for a selected size fraction of particulate material, whether the fraction comes from a coarse material, such as the product from a jaw crusher, or a more finely ground material, such as the product from a ball mill. In most cases these observations were reported as an aside and were not the main focus of the published work. This observed behaviour has the potential to be a useful tool for modelling the particle characteristics in mineral comminution and separation circuits, particularly as we move towards the development of multi-component models. However, before the behaviour can be used widely we need to understand which ore types follow the observed pattern and which do not. The current work examines a range of ores and identifies which exhibit the pattern of similarity of composition for particles in a given size class that has been produced as the result of a variety of breakage conditions. The impact of mineralogy and texture on the evolution of liberation characteristics for both valuable and gangue minerals is discussed.

Jan 1, 2008

By K Friese, H P÷llmann

Clinoptilolites, modified with sodium, produced a material which has been tested for the ability to remove Hg (II) from aqueous nitric acid. The amount of adsorption depends on contact time, acid concentration of aqueous solution and initial mercury concentration. The study of the kinetics of mercury uptake revealed that all sorbents exhibit a fast rate of sorption. The highest sorption capacities were observed for sodium forms, and were up to five times higher than for the unmodified zeolite. The maximum sorption capacity toward mercury is determined as 0.093 ¦g/g at an initial concentration of 10.0 ¦g/L for a clinoptilolite from Tsagaantsav deposit (Mongolia). The sorption of Hg (II) has an ion-exchange nature and consists of three stages, ie the adsorption on the surface of microcrystals, the inversion stage and the ion exchange in the interior of the microcrystal. Sorption capacity decreases with the increase of mercury concentration. The presence of other metal ions such as Cd (II), Cu (II), Ni (II) and Zn (II) increases Hg (II) uptake capacity. Finally, sorption for Hg (II) was investigated in batch systems to evaluate the short-term stability of the sorption properties.

Jan 1, 2008

By Frank P. Frandina

The Heartland Corridor Clearance Improvement Project is part of a regional Public-Private initiative to allow double stack container trains a direct route from the Port of Norfolk through Virginia, West Virginia, Eastern Kentucky and into Central Ohio. The project involves clearance improvements to twenty-eight tunnels, twenty-one of which require structural modification. With construction of the first Package of tunnels just underway at press time, this paper summarizes the program implementation from design through the initial stages of construction.

Jan 1, 2008

By K. C. Foye

Use of load and resistance factor design (LRFD) of foundations is growing, from offshore applications to bridge applications and beyond. The development of load and resistance factors for design has traditionally relied on calibration to traditional factors of safety. This technique, however, offers little insight into the challenges of pile design. This paper discusses an approach to LRFD factor development that seeks to isolate the various sources of design uncertainty. Using this approach, reliability analysis is used to develop resistance factors for the design of driven pipe piles in sand. These findings shed light on many aspects of the ongoing discussion of how LRFD can be successfully applied to pile design.

Jan 1, 2008

By A Kindred

The Bogong Hydropower Development is a 140 MW high head power project currently under construction in Northern Victoria. The project is the final link in the Kiewa hydroelectricity scheme, which was originally constructed in the 1950s. Due to its location in the Alpine National Park, the waterway for the Bogong project must be located entirely underground. A series of shafts and tunnels is being constructed to transfer the water from the headworks at McKay Creek to the new power station located on the shores of Lake Guy in Bogong village. The difference in elevation between the headworks and the power station is greater than 420 m, which poses particular issues for the design and construction of the waterway. The purpose of this paper is to describe the design and construction planning aspects of the tunnelling and shaft excavation and lining works for the waterway. The tunnelling works includes 5.7 km of hard rock tunnel boring machine (TBM) driven tunnel, 1.1 km of drill and blast tunnel and two deep shafts. The tunnels and shafts are lined with a mixture of permanent rock bolts and shotcrete, concrete lining and steel lining. The viability of the Bogong Hydropower Development relies heavily on the ability of the TBM to excavate at high speed through the East Kiewa Grandiorites. Particular attention was given during the construction planning stage to understanding the excavation characteristics of this material, and designing a suitable hard rock TBM that would be capable of meeting the program requirements of the project.

Jan 1, 2008

By C MacDonald

There are many technologies available today in terms of fire and life safety in road tunnels. So many in fact that it is becoming more and more difficult for clients and contractors alike to determine what they want and what they need. From a clientÆs perspective, fire and life safety is about protection to its infrastructure and to the public at large. Conversely, the contractor is looking to meet its æfit for purposeÆ or ædeem to complyÆ requirements in the most economic and practicable way. Practices regarding fire and life safety in road tunnels have undergone a degree of transformation during the last decade or more throughout the world. This transformation has largely been driven by a series of catastrophic accidents such as the major fires in Europe including the Mont Blanc Tunnel, Tauern Tunnel, Saint-Gothard Tunnel, and now most recently in the CityLink Tunnels in Melbourne. International guidelines produced by organisations such as the Permanent International Association of Road Congresses (PIARC), the European Union, the International Tunnelling Association (ITA) and the US National Fire Protection Authority (NFPA) now provide clients, owners and designers with the tools required to define and specify the required fire and life safety systems in road tunnels. The majority of these tools are based on risk assessment and risk management. Recent road tunnel projects within Australia, however, have not referred solely to such guidelines. Clients have opted to prescribe different or additional fire and life safety requirements within the projectÆs technical specification documentation (project requirements), leaving designers and contractors with little room to implement alternatives or substitutions. Further, these project requirements are largely dictated by practice established on previous road tunnel projects within Australia. This paper looks at the current international guidelines and practices and undertakes a comparison with the EastLink tunnels in Melbourne and other road tunnels within Australia and makes assessment on whether Australian methods are the most appropriate for clients and contractors alike. Focus is directed to the key elements of fire and life safety such as:traffic envelope, barrier arrangements and emergency walkway provisions;deluge systems;drainage systems;fire rating requirements;tunnel ventilation systems;cross passage provisions;fire safety assessment;critical intelligence systems including help phones, CCTV, incident detection, tunnel signage, etc; andexternal tunnel control systems.

Jan 1, 2008

Knowledge of the crystal chemistry of carbonate apatites is very important for the development of the concept of biomineralisation and the creation of a scientific base for new biocompatible materials for medical purposes. The present work is devoted to research results on various synthetic and biological carbonate apatites obtained at Saint Petersburg University over many years. All-important problems will be considered such as the location of CO32- ions in the apatite structure, the ionic substitutions in various biological apatites and the development of synthesis methods for their analogues. Syntheses of apatites were realised by precipitation methods and under hydrothermal conditions (from solid compounds and by calcite treatment). Biological samples used in this study were physiogenic and pathogenic apatites formed in the human organism, eg in teeth and in renal and salivary stones and dental calculi as well as apatites from fossils of different taxonomic families (brachiopods, conodonts, fishes, reptiles, mammal) with different geological ages and burial conditions. The study of the crystal chemistry of carbonate apatites has been carried out by powder (including high-temperature measurements) and single-crystal X-ray diffraction methods, IR-spectroscopy, thermal analysis and various chemical analytical techniques.

Jan 1, 2008

By N J. Grigg

Gekko Systems has developed an underground pre-concentration plant (Python) to reduce mine operating costs. Many ores liberate favourably using either high pressure grinding rolls (HPGR) or vertical shaft impactors (VSI). Using these comminution circuits for mineral liberation; rather than for the final recovery process and by utilising a high mass pull, high recovery process route (gravity/flotation), a narrow, low head, compact processing plant was developed that can sensibly be operated underground. The Python underground processing plant can provide a number of advantages for narrow vein mines including lower haulage costs, improved mine call factor and lower operating costs. The focus on fine crushing reduces the power requirement of the plant to approximately 8 kWh/tonne. The Python underground processing plant has been designed to be towed down the decline or lowered down a shaft, and is capable of being installed in sloping, non-linear drives for placement close to the working face. The overall benefit to mining companies of this concept has been estimated to be a saving in mining costs and a significantly smaller environmental footprint.

Jan 1, 2008

By Taegong Ryu

The thermal plasma process has been applied to the preparation of nanosized tungsten carbide (WC1-x). The reduction and carburization of the vaporized chloride by methane-hydrogen mixtures produced nanosized WC1-x powder, with a small amount of WC or W2C phase. The products were characterized using XRD, carbon analyzer, and TEM. The effects of plasma torch power, the flow rate of primary plasma gas (Ar) to generate plasma flame, and the addition of secondary plasma gas (H2) on the product composition were investigated. The tungsten carbide (WC1-x) powder had a particle size less than 30 nm. The powder was treated under hydrogen atmosphere to fully carburize the WC1-x, and W2C phases to WC as well as remove excess carbon in the product. Finally, WC powder with a grain size less than 40 nm was obtained.

Jan 1, 2008

By Ruth Marlene Campomanes Santana, Michel Tieccher, Marcondes Mafacioli Pacheco, Juliano Urach

"IntroductionThe gaseous emissions of fuel burning by mobile sources are responsible for incidence and increase of many lung and cardiovascular diseases (Braga et al., 2007). These implications can watch in morbity as much as mortality, even when the levels of pollution are considerate restrained or lower. (Leite et al., 2002).Sample of mobile sources exhausts contain not only particles directly shaped by burning, but also secondary particles that results of reaction between other compounds (Burtscher, 2004).One of the principal pollutants produced by combustion process with major toxicity and raiser of adverse effects to health is the particulate material. In its constitution there are fine and ultrafine particles that can to extend deep portion of breath system, break epithelial barrier and reach the interstitial of lungs and then, to unleash inflammatory process (Arbex, 2004).The Particulate Material is employed to define a mixture of solid particles and liquid drops suspense in atmosphere. Queiroz et al. (2007) declare that this material can be divided in two types separated by size interval that together, represent the major class of disperse particles: the fine particles type of 2,5 µm de (breath particulate) and the type of earthliness particles, major than 2,5 µm to 10 µm (inhale particle). The difference of size between the particles influences on the physics and chemistry properties. They affirm that exist correlation between size of particle and heavy metals; how many lower was the dimension of particulate materials, major is the concentration of heavy metals.The inhale particulate (MP10) that is object of present study can exhibit in your composition sulfates, nitrates, amoniacal, marine salt (NaCl), soil elements (Al, Ca, Fe, Si, Ti), metals (Cd, Cr, Cu, Ni, Pb, V, Zn) and water (Queiroz et al., 2007).Recent studies have exhibit strong relation between daily levels of particulate material inhale (MP10) with diameter until 10 µm and others pollutants and one infinity of effects to health that go since total mortality of population, sicken for specific causes until congenital bad formation or even difficult win weight by the fern during gestation (Gouveia et al., 2006)."

Jan 1, 2008

By E R. Ramanaidou, C Tessarolo, M Verrall

Garnierite mineralogy in saprolitic ore of the Goro lateritic nickel deposit, New Caledonia , was investigated using X-ray diffraction (XRD), optical and scanning electron microscopy (SEM) and electron microprobe (EMP) analyses. These conspicuously, green-coloured phases occur either as submillimetre to centimetresized veins or as æbookletsÆ arranged in, macroscopic (subcentimetre sized), accordionlike structures supported in an undifferentiated matrix of mixed ÿ7+ and ÿ10+ phases. Within the veins, nickel for Mg solid solution increased from ten wt per cent NiO at the edge to 34 wt per cent NiO at the core, with vein edges comprising Ni-kerolite with <1.5 Ni per formula unit (pfu) grading to pimelite containing >1.5 Ni pfu at vein cores. The æbookletsÆ comprised nTpouite of formula, (Mg0.67Ni1.59Fe3+0.05)(Si2.17Al0.22)O5(OH)4 and averaged 30 per cent NiO. SEM element mapping highlighted the distribution and mineralogical association of Ni and Mg and emphasised the inverse relationship between Ni and Mg at the macroscopic (thin-section) scale. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

By Wenbin Liu

A novel route for rapid synthesis of ultrafine WC-Co cemented carbides with homogeneous binder phase distribution is reported. The composite powder is produced by in situ reduction-carbonization reactions by using WO2.9, Co3O4 and carbon black as raw powders. The reaction equilibrium and phase stability are studied by thermodynamic calculations. The WC-Co composite powder is condensed by spark plasma sintering (SPS) to obtain the cemented carbides bulk. The sintering temperature is lower than that in the conventional sintering methods by 1500C, while the sintering time is remarkably reduced by 3-5 times. The high performances of the hardness and the fracture toughness are obtained. The experimental results confirm that the present processing scheme of in situ reduction-carbonization reactions and subsequent SPS sintering is an efficient way to prepare WC-Co cemented carbides, and is apparently superior to the conventional long-period techniques of preparing composite powder and cemented carbides bulk.

Jan 1, 2008

By J. Kang

To obtain microbial cultures with the ability to efficiently leach copper ion from chalcopyrite, microbial samples from acid mine drainage sites were mixed and then subjected to mutation using sodium nitrite (NaNO2), diethyl sulfate (DES), ultraviolet light (UV) and their combinations. Mixed cultures with a much stronger ability to leach copper ion (identified as mixed cultures A, B, C, D and E) were obtained by screening on leaching media. Leaching tests showed that mixed culture E had the best leaching performance and increased the Cu2+ content by 120.5% in 20 days, compared to a control without mutation treatment. Mixed culture E grows well on Leathen leaching medium supplemented with Cu2+ (at a final concentration of 32 g/L), reaching 3.2 × 107 cells/L after 15 days, while the unmutated control culture cannot survive beyond 15 days, indicating that mixed culture E is more tolerant of high concentrations of Cu2+. In addition, continuous leaching by mixed culture E is very effective at a pulp density of 1%. These results suggest that it has the potential for industrial applications.

Jan 1, 2008

By H. Palkowski

Recent trends in the automotive industry lead to increasing interest in advanced high strength steels (AHSS). Those steels often have a high bake hardening potential (BH), giving additional contribution to the strength of structural parts, subjected to the paint baking process. For hot rolled AHSS, namely dual phase and martensitic steels, the effect of process conditions on mechanical properties had been investigated. However, the influence of chemical composition within the range in industrial production has not been investigated sufficiently yet. In the current research, samples with different chemical compositions within the characteristic interval for industrial production are under investigation under different preload conditions and simulating the thermo-mechanical production process. The samples were then subjected to BH process. Tensile tests were performed to study the influence of varying chemical composition on the BH effect. The results of investigations on dual phase steels will be presented in this paper.

Jan 1, 2008

By R Riquelme

The El Salvador porphyry Cu deposit (26¦ 15Æ Lat S, ~2700 masl) and associated exotic mineralisation is situated at the back-scarp of the late middle Miocene Atacama pediplain in the western Precordillera. New, together with published 40Ar-39Ar data from El Salvador combined with morphologic analysis reveal that the palaeospring plumbing system related to exotic mineralisation at the Damiana exotic Cu deposit and the local geomorphology has not changed fundamentally between the late Eocene and late Miocene. Stable H/D isotope data on supergene alunite from El Salvador indicate an overall increase in dD values (VSMOW) from -74ë at 35.82 ¦ 0.95 Ma to -23ë at ~11 Ma. The transition from strongly to moderately negative deuterium values occurred between ~16 and ~13.5 Ma. Supergene alunite from the El Hueso (3950 masl) sedimentary rock-hosted epithermal deposit ca 35 km SE from El Salvador was dated at 8.19 ¦ 0.01 Ma and yielded a dD value of -25ë. We interpret the increasing deuterium excess as the result of strong evaporation and recycling of meteoric water after ~15 Ma and as indicative for a change in precipitation patterns and climate desiccation. In contrast, the strongly negative dD value for late Eocene supergene alunite points to a more humid climate and an elevation similar to the present. The late Miocene supergene activity at El Hueso is probably related to an uplift of the Precordillera to elevations sufficient for capture of orographically controlled precipitation. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008