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By W. J. Birch, A. Wetherelt

The scaled-distance model for blast vibration analysis is the standard method employed throughout the surface mining and quarrying industries to model Peak Particle Velocity (PPV) data. Although empirical, the method is widely accepted and through the simplicity of its application and ease of graphical verification is set to remain a popular option. The validity of the technique relies principally on the fundamental parametric assumption that blasting data is normally distributed. Throughout the evolution of scaled-distance modelling, this is an issue that has most often been presumed rather than proven (most likely due to the tediousness of the calculations involved). In the few cases when normality has been given some degree of consideration, the result has been the product of a simple visual inspection of frequency distributions: clearly unsatisfactory. However recently the soundness of this assumption has been brought into question, with obvious connotations for blast modelling in general. This paper considers this fundamental issue and seeks to investigate the normality hypothesis within the blasting context through an in-depth statistical analysis of what possibly can be described as an ‘ideal’ blasting dataset. This being a rare case study concerning an opencast coal site in England, where for the entire life of the site every single blast was monitored and recorded through the use of permanent monitoring stations. This has provided a unique ‘total population’ dataset of considerable size from which the assumptions of normality are put to the test.

Jan 1, 2005

By E. Asselin

Electrochemical polarization experiments were conducted on alloy 625 in ammonia solution between 25 and 225°C and the results were compared with those of an oxygen solubility model. Results confirm that corrosion is under oxygen control, Normalized corrosion rates are determined based on the rate of oxygen diffusion to the corroding surface, and the corrosion rate at 200°C (-9.7 µA.cm-2) is roughly 24 times higher than the corrosion rate at 25°C (0.4 nA,cm-2), An oxygen-solubility model for Supercritical Water Oxidation (SCWO) conditions was generated using the Redlich¬Kwong-Soave (RKS) equation of state, Results of the model confirm many of the experimental observations from SCWO reactors which suggest that corrosion is at a maximum at temperatures just short of the critical point, The RKS/oxygen diffusion model predicts that the corrosion rate at 365° C is ?85 times higher than the corrosion rate at 25' C. Given that a normalized corrosion rate is obtained, this type of model could be useful for selection of SCWO reactor materials.

Jan 1, 2005

By AN. Kumar

Two fabrication stages in the manufacture of pipelines are identified as causing significant deterioration of the steel plates, namely cold bending and welding. The objectives of this work include quantitative assessment of the degradation of the quality of the steel plate by the loss of fracture toughness, and an estimation of the safe working pressure. The study was conducted on three API grade steels: X42, X46 and X60. After cold bending by the UO technique, various welding technique were employed for joining of the bend plates along the pipe length. A crack-tip opening displacement parameter (CTOD) was used at the onset of initiation and at the first load maxima as the criterion for assessing the toughness degradation under various fabrication stages and regime (such as WZ, HAZ and parent body). In addition, strength, hardness and impact energy values were determined to check the degree of degradation. Microstructural and microfractographic investigation of the fractured samples were also carried out in the scanning electron microscope (SEM). X60 grade steel plate suffers from CTOD toughness loss by around 38 and 55% after welding and cold bending, respectively, for the conditions studied. A combined effect of the two stages results in a loss in toughness by around 70% for the same steel. In X42 grade, the loss in impact energy ranges from 78 to 35 J due to electrical-resistance welding study (ERW). Crack resistance curves are also obtained for the steels to study the crack growth resistance behaviour and to supplement the information on crack initiation behaviour. The orientation of the pearlite banding, as observed on the fracture plane with respect to notch front and applied loading direction appears to have a strong influence on the microvoid-coalescence mechanism of fracture as well as the toughness values. An integrated analysis of the performance of pipelines, considering all these key factors, is discussed.

Jan 1, 2005

By R. Krentz, P. D. Cordingley

The nickel-cobalt sulphides produced from limonitic laterite ores by Moa Nickel S.A. in Cuba are refined at the Corefco nickel-cobalt refinery in Canada. Major changes to the refining process were required when the Moa sulphide feed, with its unusually high cobalt content, was introduced in the early 1990's. In the period 1994 to 2005 the production capacity of the refinery has increased dramatically to match increases at Moa, and significant process improvements incorporated. The process flowsheet consists of the original ammonia leach process, optimized for cobalt chemistry and overall leaching capacity. Extraction of metal values is followed by the unique nickel-cobalt separation technology, in which most of the cobalt is separated from the ammoniacal nickel sulphate leach solution by precipitation as a nickel-cobalt hexammine salt. This salt is refined from a Co:Ni ratio of 1:1 to over 10,000:1 by selectively leaching nickel, redissolution and recrystallization in ammonium sulphate solution. Nickel and cobalt are recovered using the well-known Sherritt hydrogen reduction technology. This paper reviews the chemistry described above, examines some of the changes in operating conditions made over the years and highlights some of the recent physical changes made to the refinery.

Jan 1, 2005

By Leslie C. Taylor, Anthony L. Kee

Computational modeling of explosively loaded saturated sand on a suspended plate is an inherently complex problem. In this study a computational method is used to predict the dynamic pressure load/impulse from a buried charge. A fully coupled code modeling the explosive charge, sand and air with a Eulerian mesh and the plate structure with Lagrange elements, such as Gemini-Dyna, is an appropriate computational tool. In water-saturated sand, the loadings are soil and water-transmitted shock and bubble or blast effects depending on the depth and the charge size. The computations provide the capability to determine the total impulse load placed on a horizontal plate on or above the soil due to an explosion in the saturated sand for different burial depths in saturated sand and different plate stand off distances. The following test case will be presented: (a) 4.5 Kg (10 lbs) TNT, 10.16 cm (4 in) depth of burial to top of charge, and 20.32 cm (8 inch) stand off distance (Test 4).

Jan 1, 2005

Strips of AA6111 automotive alloy were cast on a horizontal single belt strip casting simulator, Pure copper and carbon steels substrates plasma sprayed with different coatings for improving the strip surface quality, were used as chill moulds, Experimental studies revealed that a graphite coating provided the greatest benefit in achieving good surface quality. The interfacial heat fluxes during solidification of AA6111 strip were calculated by the IHCP method (Inverse Heat Conduction Problem). Temperature variations and cooling rates within the strips were then calculated through numerical simulations based on the time-dependent heat fluxes obtained by IHCP, The effects of casting parameters, including casting temperature and strip thickness, on interfacial heat fluxes, cooling rates and microstructures, were investigated, Although the maximum interfacial heat fluxes on the chill copper substrate were much higher than the results obtained from the steel substrates, the solidification times of the melts were mainly determined by strip thickness. Very fine equi-axed grains were obtained for both 1.2mm and 2.5mm thick strips thanks to the rapid extraction of heat, and effective grain refinement.

Jan 1, 2005

By W. Basuki, B. Setyotomo, L. Hakim, R. Hendrajaya

Due to high crack sensitivity of slab product of gas and oil line pipe application, its steel making process and alloy composition were evaluated and then improved to overcome its critical solidification process and reduced surface defects. The study was conducted at Slab Steel Plant Krakatau Steel. The purpose was to improve slab surface quality by reducing surface defects so that the slab surface doesn't need to be totally repaired. The method applied was by performing plant trial process, which the secondary process parameters such as alloying method and the casting parameters such as casting powder selection, metallurgical cooling, mould level control, and superheat were continuously monitored and then adjusted to the surface quality of the product. Based on the calculation of Ferrite potential of the steel, the chemical composition was designed to achieve optimum casting parameters in order to avoid high shrinkage during solidification. The results of the study are decreased surface defect quantity, and smooth casting process. The quantity of crack decreased by almost 90%. The slab surface repairing was significantly reduced from 85. % to less than 10%. These new casting parameters and developed alloy composition are then used and standardized for the mass production of the steel.

Jan 1, 2005

By J R. Hernandez-Aguilar, C O. Go, C Acuna

The gas dispersion properties that are the subjects of this communication include three measured parameters, gas superficial velocity (gas rate), gas holdup and bubble size, plus derived parameter, bubble surface area flux. Over the past ten years sensors to measure these parameters have been introduced and those originating from McGill University are briefly described. The sensors have seen extensive use in plant campaigns and experiences on four cell types at three sites are discussed. The impact of frother in controlling bubble size by retarding coalescence is illustrated, introducing the need to understand chemistry/machine interactions in interpreting gas dispersion results. An increase in Sauter mean bubble size (D32) with superficial gas velocity (gas rate, Jg) was found, which followed the empirical relationship where Do ~ 0.5 - 0.6 mm and C and n are fitted parameters dependent on the system (machine and chemistry). Following this trend in Db - Jg, consistent bubble surface area flux (Sb) - Jg trends are also observed. The trend in Sauter mean versus number mean (D10) is used to help interpret the nature of the distribution; as the means approach numerically, the distribution is narrowing. Analysing gas holdup versus gas rate shows both a dependence on location in the cell as well as cell position in a bank, factors which must be accounted for when comparing data from different plants and circuits. The instrumentation and methodologies being developed are presenting new opportunities for incorporating cell hydrodynamics into metallurgical diagnostics. A case study at one plant serves as illustration.

Jan 1, 2005

By R Verreet

In April 2000 Mount Isa Mines installed hoist ropes of a new design on the double-drum winder at their P49 shaft. The ropes, CASAR Duroplast, were about three times as expensive as the previously used triangular strand ropes. The P49 shaft is situated at Mount Isa MinesÆ George Fisher Mine, located some 30 km north of Mt Isa. This shaft used the tried and proven 6 x 33 triangular strand style ropes. The rope life attained by these ropes at the time was acceptable due to many years of satisfactory performance. The following study indicates the improvement of service life using CASAR Duroplast rope in P 49 shaft, which depends on shaft and winder parameters of that particular shaft and cannot necessarily be generalised to other shafts.

Jan 1, 2005

By G. T. Lapidus, R. M. Luna-Sánchez

In the present study, a series of cyanidation experiments were performed on a bulk sulfide concentrate which contained silver in four distinct phases, to determine its extraction rate, varying the oxygen concentration. The results showed that three of the four phases were refractory, aguilarite (Ag,iSeS) being the only leachable phase, and that the effect of the oxidant concentration is minimal. Mathematical simulations were performed, adjusting only the Damkohler number to adequately fit the experimental data. This model, and the mechanism implied, was compared with that found for acanthite (Ag2S) in a previous study, and the differences between the two discussed.

Jan 1, 2005

By R. L. Eadie, J. L. Luo

The effect of plastic deformation on near-neutral pH stress corrosion cracking (SCC) also known as environmentally assisted cracking was studied by cracking rate measurements. All the tests were conducted in a synthetic near-neutral pH solution. The traditional potential drop tests using compact toughness (C-T) specimens with 2-3 mm long pre-cracks showed varying plastic deformation by rolling would increase the material's susceptibility to SCC. This was confirmed by cyclic loading tests using double notched flat tensile specimens with 200-300 µm long pre-cracks which gave the same results that the specimen with large scale plastic deformation by tensile loading had a relatively faster crack growth rate than that with only small scale plastic deformation.

Jan 1, 2005

By K. Häge

"Die Nachhaltigkeit der Braunkohlengewinnung in der öffentlichen Wahrnehmung wird nur weiter erfolgreich kommuniziert werden können, wenn durch konkretes Handeln glaubhaft gezeigt wird, dass die offenen Fragen fair und solide beantwortet werden. Dazu gehören insbesondere die neue innovative technische Lösung sowie das sensible Interessenmanagement. Die Braunkohlenindustrie hat gelernt, dass Offenheit und nicht zuletzt das beständige Bemühen um den Meinungsaustausch mit ihrem Umfeld wichtige Elemente sind. Der in Jahrzehnten erworbene Schatz an Glaubwürdig-keit ist eine Basis, auf der die Braunkohlenindustrie ihre Zukunft gestalten kann. Darüber hinaus sind politische Rahmenvorgaben erforderlich. Das öffentliche Interesse an einer sicheren und preiswerten Energieversorgung unter Einschluss der Braunkohle ist unverzichtbar. In diesem Kon-text kann dann die Braunkohle die an sie gerichteten Fragen der Ökonomie, der Ökologie und der Sozialverträglichkeit auch mit Hilfe von Indikatoren beantworten.ABSTRACTThe discussion of the sustainability of lignite mining can only be continued successfully if the indus-try acts in a practical manner and demonstrates trustworthiness by responding fairly and reliably to open questions. This includes new and innovative technical solutions as well as the sensitive management of interests. The lignite industry has learned that openness and the constant effort to exchange viewpoints within their environment are all essential elements. The credibility that has been gained over the decades is the foundation on which the lignite industry can build its future. Beyond that a framework of political guidelines is necessary. Public interest in a secure and inex-pensive energy supply that also includes lignite is indispensable. In this context, the lignite industry will then be able to answer the questions which are directed at them and concern the economy, ecology, and social tolerability also by indicators."

Jan 1, 2005

By D. Dreher Whetstone, Paul M. Blakita, Christopher M. Reith, Ravi P. Malviya

"Micro-piles are small diameter (5 to 10 inches), cast-in-place piles which can develop high load capacities by bonding with soil or rock. Micro-piles are particularly well-suited for moderate to heavily loaded structures requiring deep foundations in difficult subsurface conditions, such as karst, bouldery mine spoil, or unsuitable fills with concrete debris or other obstructions. Attempts to install conventional deep foundations including driven piles, drilled piers, or auger-cast piles are likely to be fraught with construction difficulties and disputes, delays, cost overruns, and may be unfeasible in some cases. Micro-pile installation equipment is very effective in installing foundations through such overburden or rock materials.This paper presents case histories of Micro-pile installations on two projects with difficult soil/rock materials. The project sites are located in Charles Town, West Virginia and Masontown, Pennsylvania.Charles Town, West Virginia ProjectThe Charles Town project entailed construction of a four-story pre-cast concrete garage. Triad Engineering, Inc. performed a geotechnical investigation for this project (Triad, 2001). The subsurface, geologic, and project specific information described in th is paper are largely based on the aforementioned geotechnical report.Ground ConditionsThe project site is located in Jefferson County, West Virginia, and is mapped to be underlain by the Elbrook Formation. This formation is described as argillaceous, dolomitic limestone with beds of dolomite and aphanitic and algal limestone (Dean, et al. , 1990). The carbonate rocks at the site were characterized as ""moderately solution-prone, highly calcareous and weathers differentially to produce a pinnacled or ""sawtooth"" top of rock profile. (Triad, 2001 )"" Overburden soils consist of low to high plasticity, fine grained residual soils formed by weathering of the parent carbonate rock. The residual soils include variable proportion of sand and rock fragments."

Jan 1, 2005

By D Giddings, S A. Silvester, S Pickerin

Underground fires represent a constant threat to the safety of underground personnel. Miners in the immediate vicinity may face intense heat, blinding smoke, toxic fumes, fall of ground and other direct effects of a fire. However, the vast majority of victims never actually see the fire, and are overcome either by deadly fumes in the ventilating current or by asphyxiation. The mine ventilation system, which maintains a sustainable atmosphere to the working places, can transport products of combustion with equal efficiency. Miners who are remotely situated from a fire may be forced to evacuate considerable distances, through dense smoke and fumes, or even become cut-off from escape. Additionally, miners may become confused by unfamiliar ventilation characteristics caused by fires. Conveyor belts are widely used for transporting minerals in mines as well as in many other industrial situations. Because they contain large amounts of polymeric materials their use in certain environments, especially coal mines, but also in steel works, power stations and other enclosed areas must be controlled to minimise the fire risk. Over last nine years there have been 60 fires in underground mines in the UK alone and that of these, half have been associated with conveyors. This paper summarises the results obtained from a recent research project that has developed a preliminary computational thermal and fluid dynamic model to represent the spread of flame along a typical conveyor belt used in UK deep coal mines. The results of these models have been calibrated against a series of experimental tests performed within a surface fire test gallery. An improved knowledge of the burn characteristics and rate of release of the products of combustion from conveyor belt fires will assist in the development of better fire detection and fire fighting techniques.

Jan 1, 2005

By J Koppe, J F. Costa

A fundamental error of sampling occurs when a sample is extracted from a larger mass of ore or lot. The act of sampling requires that all particles belonging to the lot have an equal chance of being extracted. This type of sampling is called unbiased sampling. The sampling equipment (herein referred to as the sampler) should be constructed with some additional mechanical characteristics to guarantee that the samples will be unbiased. Samplers, extracting increments from a continuous flow, such as a conveyor belt, collect aliquots at regular time intervals. These time intervals relate to the number of aliquots extracted from a given mass of lot, whilst passing through the continuous flow. The frequency of extractions will influence the precision or the error of the sample (integration error). Further, the ore variability influences the amount collected from the continuous flow. Normally, the sampling protocol utilised is designed for the extractions obtained from the conveyor belt, omitting any error committed during this operation, ie the error of extracting from the continuous flow. This study aims to analyse the error of sampling a continuous flow by using a variogram with added on auxiliary functions. Each different piece of material passing through the flow will exhibit a distinct temporal variogram, which should influence the frequency of the samples being extracted for each chosen sampling error. The methodology used is presented in the form of a case study from a coal processing plant.

Jan 1, 2005

By J M. F Clout

Geological, textural and mineralogical classification of iron ores is routinely conducted by mine and exploration geologists on reverse circulation percussion, blasthole cone and bulk samples for grade control, defining ore and waste, determining lump:fines ratio and predicting downstream processing characteristics. Classification is based on physical hardness, colour, streak and other visual characteristics. However, logging is generally restricted to the five to 20 per cent of chips above about 2 mm. This means that most of the sample is too fine to be reliably logged for anything but colour or streak and the textural types must be inferred from other information. A recently developed software package called æRecognitionÆ allows automated identification and classification of iron ore textural types and gangue on a particle basis in polished section down to 0.01 mm using processed digital images. It is not designed to be used as a routine logging tool, but is applicable where higher definition is required at the resource evaluation stage on selected percussion, drill core or bulk samples. æRecognitionÆ processes data obtained after optical image analysis of fine iron ore samples. It contains several parts, like æRecognitionÆ, æCompositionÆ, æLiberation by Total IronÆ, æLiberation by PhasesÆ and æStatisticsÆ, which allow vast and diverse information to be obtained about the iron ore samples being studied. Identification and classification of the textural type of each particle is performed according to the CSIRO-Hamersley Iron Ore Group Classification Scheme. The recognition procedure encompasses a good knowledge of different ore types and a logical knowledge tree, managing fuzzy boundary problems and the potential for a few different ore types in the same particle to be considered. This new technology introduces strict criteria to make the process of identifying particles more objective. Automated recognition standardises the identification procedure and significantly saves time. It enables users without a strong background in mineralogy to perform accurate texture identification. The æRecognitionÆ package has a modern user-friendly interface and Word compatible output. The combination of all the features mentioned makes the package a convenient tool for detailed studies of fine iron ores.

Jan 1, 2005

By Hitoshi Ogura, Koichi Kobayashi, Sadao Yabuuchi

"In Japan, most pile foundations using pre-cast concrete piles are installed by the bored pre-cast piling method, wherein pre-cast piles are installed in holes that have been excavated beforehand and filled with cement milk (term used for cement water slurry in Japan). The bored pre-cast piling method with enlarged base, in which the portion near the toe is enlarged during boring operation, is widely used because of the cost benefits and the increased vertical bearing capacity that this method offers.The EX MEGATOP method, further developed as an improved bored pre-cast piling method with enlarged base, is reported here. The features of this method are: (1) High vertical bearing capacity; (2) High degree of freedom in design; (3) Excellent workability; and (4) Friendly to the environment. In particular, high vertical bearing capacity can be obtained using nodular piles and by enlarging the area at the pile toe and shaft. This method can gave a vertical bearing capacity coefficient at the toe of a=430, more than twice the corresponding value of a = 200 of a conventional bored pre-cast pile. Moreover, the shaft resistance can be several times larger than that of a conventional bored pre-cast pile. This report gives an overview of the EX MEGATOP method, evaluation of vertical bearing capacity, and examples of application of the method.1.lntroductionMost pile foundations in Japan are installed by the bored pre-cast piling method, that is, in holes that have been excavated beforehand and filled with cement water slurry, referred to as 'cement milk'. The ""bored pre-cast piling method with enlarged base"" is frequently used. In this method an enlarged excavation is used near the pile toe to increase the vertical bearing capacity.The EX MEGATOP method is a variation of the bored pre-cast piling method. Its features include the use of nodular piles and a long, enlarged excavation. The vertical bearing capacity of the EX MEGATOP method is described in this report."

Jan 1, 2005

By Nabil F. Ismael, Mohamed El Deeb

"The behavior of laterally loaded step tapered bored piles in calcareous sand was examined by field tests. Lateral load tests were carried out on straight and step tapered bored piles 5.3 m long embedded 5 m below ground level. All piles were installed by augering. The straight piles were 0.2 m, and 0.3 m in diameter. The step tapered piles have a diameter of 0.3 m along the upper 10%, 20%, and 40% segment, respectively, changing to 0.2 m for the lower section. Two piles were instrumented with strain gages to measure the bending strains. All tests were carried out to failure. The purpose being to examine the ultimate lateral capacity and the deflection at working loads. Test results indicate non linear response and substantial increase in lateral capacity and decrease of deflection for the step tapered piles compared with the 0.2 m diameter straight shaft piles. However, beyond a depth of 40% of the pile length, the strengthening of the pile section by enlargement of its diameter had little effect on the lateral capacity and the deflection of step tapered bored piles.IntroductionFor many structures on pile foundations the ultimate capacity under lateral loads is important and may be the controlling factor in foundation design. Examples include transmission tower foundations and fender piles at sea port facilities. Increasing loads on these structures has resulted in piles of large diameter and depth at a significantly higher cost.In this work, the use of step tapered bored piles with a larger diameter along the upper segment of the piles is examined by field testing and analysis on single piles in calcareous desert sands. Lateral load tests were carried out on straight and step tapered piles 5.3 m long embedded 5 m below ground level. The straight piles were 0.2 m, and 0.3 m in diameter. The step tapered piles had a diameter of 0.3 m along the upper 10%, 20%, and 40% segment, respectively, changing to 0.2 m for the lower section. Two piles were instrumented with strain gages to measure the bending strains. All tests were carried out to failure. The purpose being to examine the ultimate lateral capacity and the deflection at working loads for step tapered bored piles."

Jan 1, 2005

By M. Galetakis, C. Roumpos

A sustainable coal industry needs to achieve a number objectives concerning mainly with superior utilisation of deposits and improved environmental performance. Modern quality control systems, which are greatly based on the on-line analysers, play an important role in achieving sustainability targets. This paper discusses the testing and application of on-line ash analysers installed in the Ptolemais and Megalopolis lignite mines in Greece and examines the possibility of using this type of analyser to control blending and homogenisation operations. The effect of the accuracy of on-line analyser to control process, when used for the characterization of low rank coals with complex and variable composition, such as greek lignites, is examined.

Jan 1, 2005

Legislation introduced for Queensland and New South Wales Coal mines provides different levels of prescription regarding specification of mine seals û generally in relation to capacity to withstand overpressure. In Queensland, the Coal Mining Safety and Health Regulation (2001), Section 341 (d) places a further onus on the statutory ventilation officer to æensure all ventilation control devices at the mine are properly constructed and maintainedÆ and that the ventilation officer æmust ensure a ventilation control device mentioned in the regulation à and installed at the mine meets the design criteria statedÆ for the ætype of deviceÆ. Based on the experience of the author, it appears that risk management and life cycle approach to seals has not been adopted to the same extent as for other aspects of operations. Further, because of the number of disciplines and personnel involved that may influence various factors affecting seal integrity, the opportunity for oversight or unclear allocation of responsibility is considerable. While suppliers can provide explosion or design rated seals, this should only be a starting point for application of the product in a coal mine. Application is often considered by mine planning staff (taking into consideration mine environment parameters such as water, control of gas, spontaneous combustion risk, etc) in conjunction with the colliery ventilation officer, and then construction completed by contractors under supervision of operational staff. After construction, seals often are managed by operational personnel with input from the ventilation officer. Input of the geotechnical engineer into pillar design, roadway opening size, ground support specification and most stable seal location is also required. The need for a customised design approach for each seal site is proposed in order to take into account the many and variable factors that may influence a site so that improved seal performance reliability and predictability can be developed. A program of quantitative as well as qualitative monitoring of performance and triggers for rectification or maintenance action is required, and would provide support to the aforementioned proposal. Many mines rely on visual/audible inspection and periodic bag sampling as the primary means of assessment. Other significant factors such as seal material properties, rib degradation, convergence, floor heave, effects of water on both structural integrity of the seal as well as the air tightness of the seal do not generally receive the same level of attention. Based on the above observations, the author has compiled a reference checklist in regard to the above matters, including aspects of and approaches to mine and pillar design, geotechnical modelling and data collection, civil engineering design, site evaluation and practical options available.

Jan 1, 2005