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By T. Feldmann, G. P. Demopoulos

The feasibility of chloride leaching processes depends on interfacing them with cost-effective HCl regeneration technologies. This paper summarizes the most important findings of research conducted in the past 3 years concerned with a novel process to regenerate high-strength HCl from concentrated CaCl2 solutions at temperatures below 100°C, via reaction of CaCl2 with H2SO4 resulting in the formation of calcium sulfate phases (gypsum, a-hemihydrate or anhydrite). From constant supersaturation semi-batch experiments in pure solution it was found that the crystal growth rate of hemihydrate, and hence the particle size, was influenced by the rate of reagent (Ca2+, SO4 2-) supply to the reactor. Additionally, growth studies of DH in presence of impurities (K+, Mg2+, Sr2+, Ba2+, Fe2+/3+, Al3+, La3+, Y3+, F- and PO4 3-) showed that specifically Sr2+ and PO4 3- are taken up during crystal growth. Furthermore, it was found that decreasing water activity (via different HCl/CaCl2 concentrations) and increasing temperature reduce the metastable life-time of DH and HH by increasing the phase transformation speed. The DH/HH transformation was identified to be dissolution-precipitation based, while HH to AH is a topochemical process. Finally, continuous experiments on bench scale are underway to confirm the feasibility of the process to obtain super-azeotropic strength HCl with up to 9 mol/L (~30wt.%) from 5 mol/L CaCl2 (~40wt.%) solution.

Jan 1, 2014

By Mingxia Liu, Hao Li, Qi Liu

"Laboratory batch flotation tests were carried out on fine (-20 µm) hematite to investigate the non-polar oil’s influences when sodium oleate, octyl hydroxamic acid, or oleyl hydroxamic acid were used as a collector. Batch flotation tests were performed with artificial mixed minerals (hematite:quartz = 1:1) under natural pH condition and kerosene was utilized as the model oil. The experimental results showed that kerosene emulsion behaved differently when used in conjunction with the three collectors. Kerosene helped improve the flotation when sodium oleate or oleyl hydroxamic acid was used as a collector. Nevertheless, it reduced concentrate weight yield, grade and recovery to a noticeable extent when octyl hydroxamic acid was used as a collector, especially at low dosages. In addition, single hematite batch flotation kinetics tests coupled with water recovery measurement were carried out to study the role of kerosene at different collector dosages. It was observed that water drainage and the resulting froth destabilization by kerosene was dominant at low collector dosages, especially in the flotation using octyl hydroxamic acid. At higher collector dosages, the water drainage and froth destabilization effect by kerosene was possibly counter-balanced by the higher hematite hydrophobicity and bubble surface tension gradient, which led to more stable froth layer.INTRODUCTION The minerals industry is facing a steady decline in ore grade, compounded by increasing complexity of mineral dissemination. As a result, the ore has to be ground sufficiently fine to have a suitable degree of mineral liberation, which produces large percentages of fine and ultrafine particles outside of optimal size range for ore dressing. Due to the unique characteristics of fine particles, i.e., small mass, high specific surface area, and problems such as increased solubility of complex minerals (Finkelstein, 1997; Finkelstein & Allison, 1976; Fornasiero & Ralston, 2005), high reagent consumption, fast surface oxidation in the case of sulfides (Collins & Read, 1971; Klassen & Mokrousov, 1963), severe particle entrainment (Subrahmanyam & Forssberg, 1988; Warren, 1984), low flotation rates (Glembotsky, 1953; Philippoff, 1952; Ye & Miller, 1988), slime coating (T. K. Mitchell et al., 2005; Parsonage, 1984), etc., flotation performance of these finely ground ores is very poor in terms of low concentrate grade and recovery."

Jan 1, 2017

By B. Haugrud, E. McConaghy, M. Collins, G. Smith

"Laterite ore processed by the Ambatovy joint venture in Madagascar is primarily limonitic in nature, containing approximately 40–45 wt.% Fe and 1.1 wt.% Ni. The process selected for treatment of this ore considered the behaviour and deportment of iron in each step of the commercial flowsheet. Such considerations included nickel and cobalt recoveries, reagent consumptions, liquid-solid separation characteristics, and intermediate and final product purities. In this paper, the results for the first three years of commercial operation at Ambatovy are compared with the design parameters, with emphasis on the behaviour of iron.RÉSUMÉ Le minerai latéritique traité par l’entreprise commune Ambatovy au Madagascar contient principalement de la limonite, composée de 40–45 % en poids (wt%) de fer (Fe) et de 1,1 wt% de nickel (Ni). Le procédé choisi pour le traitement de ce minerai tenait compte du comportement et du maintien du fer à chaque étape du schéma de traitement commercial. Parmi les facteurs pris en compte figuraient les récupérations de nickel et de cobalt, les consommations d’agents réactifs, les caractéristiques de séparation des liquides-solides ainsi que la pureté des produits semi-fini et final. Cet article compare les résultats des trois premières années d’exploitation commerciale à Ambatovy aux paramètres d’étude, en insistant notamment sur le comportement du fer.INTRODUCTIONThe main component of nickeliferous laterite ore is iron, and the Ambatovy deposit in Madagascar is no exception. Ambatovy ore is primarily limonitic in nature, containing approximately 40–45 wt.% Fe and 1.1 wt.% Ni. The nickel content of the ore is approximately 1/40th that of the iron content by weight; therefore, successful recovery of nickel depends on close control of the behaviour of iron in the selected process.The Ambatovy area is located 80 km east of Antananarivo, the capital of Madagascar. Exploration dates back to 1960, when the Malagasy Service Géologique carried out a limited pitting and auger-drilling program. Phelps Dodge Corporation (now Freeport-McMoRan Copper & Gold, Inc.) was granted the mining rights to the property in 1995 and carried out significant resource definition, environmental assessment, and engineering studies between 1995 and 2001 (Chou, Rooke, Williams, & Hanks, 2000). In 2003, Dynatec Corporation, which was formed in 1997 by the merger of Dynatec International Ltd. and Sherritt International Consultants Inc., signed a joint venture agreement with subsidiaries of Phelps Dodge to evaluate the Ambatovy nickel project. Dynatec became extensively involved in the development of the project, including process selection and pilot plant testing in Fort Saskatchewan, Alberta (Collins et al., 2004, 2005; Collins & Vardill, 2005; Collins, Buban, Holloway, Masters, & Raudsepp, 2009). Dynatec acquired 100% of the project in 2005 and a joint venture between Dynatec, Sumitomo Corporation, Korea Resources Corporation (KORES), and SNC-Lavalin Inc. (SLI) was formed shortly thereafter to provide funding for further development. SLI was responsible for engineering, procurement, and construction management of the commercial facilities. Sherritt International Corporation reacquired Dynatec Corporation, including 40% ownership in the Ambatovy nickel project, in 2007. The current Ambatovy joint venture consists of an integrated nickel and cobalt mining, processing, refining, and marketing enterprise between subsidiaries of Sherritt (40% owner and mine and plant operator), Sumitomo Corporation (32.5% owner), and KORES (27.5% owner)."

Jan 1, 2017

By D. Cronin, A. Plumtree, A. Hosseini

"Crack in corrosion (CIC) linepipe defects are hybrid defects not directly addressed by existing assessment methods. To investigate the collapse pressure of these defects, CIC defects were formed in 508 mm (20 in) diameter, 5.7 mm thick API X52 linepipe. These defects were 200mm long and varied in depth from 3.0 to 3.8 mm. The respective failure pressures decreased from 14.3 MPa for the plain pipe to 7.9 and 6.2 MPa respectively. A standard FAD method was applied to evaluate these defects as equivalent length and depth cracks, predicting the rupture pressure conservatively by 18% on average. However, when assessed as equivalent cracks with a reduced wall thickness corresponding to the corrosion depth, the predicted collapse pressures were more accurate, approximately 14% conservative on average.INTRODUCTIONPipelines are a safe and efficient method for transporting high volumes of oil and gas. However, aging pipelines may experience defects, such as cracks or corrosion. Present approaches include detection, assessment and repair of defects before they may become critical to the integrity of the line. There are different codes and standards for assessing pipeline defects, depending on the type of defect, with API 579 (API, 2000) being the most common code for the assessment of cracks in oil and gas pipelines . Corrosion is commonly assessed using RSTRENG (Kiefner & Vieth, 1989). Other methods such as the Finite Element method and the CPS method (Cronin & Pick, 2002) may be used for crack and corrosion, respectively.At present, there is no specific method or procedure for assessing crack in corrosion (CIC) defects, and as a consequence there is a need to provide an assessment and evaluation of the integrity of these defects in order to determine the requirements for defect repair or hydro line testing. Hence, the goal of this study was to provide guidance for the assessment of CIC defects for linepipe.CRACK IN CORROSION DEFECTS (CIC)Significant amounts of corrosion and cracking are not generally found together (Hosseini, 2010). However, a new hybrid defect including cracking within corrosion (CIC) has been identified in operating pipelines. In this case, cracking coincident with corrosion (schematic shown in Figure 1) provides the motivation for the current study."

Jan 1, 2012

By I. Vazaios, M. S. Diederichs, N. Vlachopoulos

"As rock engineering moves from continuum to more discontinuum approaches for modeling, the engineer must make decisions regarding the degree of complexity to simulate for a given application, balancing the level of structural detail within the rockmass model with computational cost and result accuracy. It is important to consider that model does not need to include all the existent fractures and that representative geometrical properties for a given rock mass volume can be defined including only major structural entities.Within this paper, the scale-dependency associated with the geometrical properties of fractured rock is investigated utilizing a Synthetic Rockmass (SRM) approach with a view to characterize such ground to aid in the design of geotechnical works. In terms of process, the concept of the Representative Elementary Volume (REV) is used to determine the equivalent structural properties of the rockmass in order to justify the applicability of far-field behaviour of such ground. A large size Discrete Fracture Network (DFN) measuring 60m x 60m x 60m has been generated using the structural data obtained from LiDAR scanning of the Brockville Tunnel, Ontario, Canada. A number of DFN samples of varying sizes are extracted from the master network, generated using MoFrac, in order to be used as a the basis of the structural analysis of the rockmass. Volumetric measurements for the density and the intensity of jointing are employed in order to approximate the geometrical REV for the networks.In this paper a complete methodology of how to generate a DFN from LiDAR data and its analysis in order to determine the size of a geometrical REV is demonstrated. For the specific rockmass found in the area of the Brockville Tunnel, a geometrical REV measuring 3.5m x 3.5m x 7m is established. The results are generally in good agreement with the in-situ observations."

Jan 1, 2015

By L. Tong

The nickel laterite ore is composed of soft and hard minerals, and nickel distributes preferentially into the soft mineral rather than in the hard. Selective comminution of saprolitic and goethitic nickel laterites is investigated to upgrade nickel into the fine fraction using stirred milling. The optimal selective grinding conditions were determined through a kinetic study and the limit of selective grinding and nickel upgrade was analyzed. The breakage rates of minerals, grinding time, and the weight ratio of soft and hard minerals in the feed play an important role in selective grinding. A small breakage rate on hard minerals and a large breakage rate difference between the minerals are optimum for selective grinding. The soft mineral grade decreases with grinding time and the optimum grinding time is a trade-off of the soft mineral upgrade and recovery. The minerals weight ratio determines the limit of selective grinding. The effect of nickel upgrade is determined by both the conditions that influence selective comminution and the nickel grades in both the soft and hard minerals. The nickel grade in the soft mineral determines the limit of nickel upgrade.

Jan 1, 2015

By A. P. Paiva

The solvent extraction properties exhibited by some /V,N'-tetrasubstituted malonamides to efficiently and selectively recover iron(III) from concentrated chloride leaching solutions can be found in the recent literature. The iron(III) extractive chemistry exhibited by some of these derivatives is revisited, in order to compare their chemistry with that shown by a few of the new malonamide compounds. The generally good extraction efficiency towards Fe(III), from >4 M hydrochloric acid solutions, and the relative ease of Fe(III) stripping by distilled water are remarkable findings that are confirmed for the malonamide derivatives described in this work. Furthermore, additional data regarding their selectivity towards Fe(III) extraction over several base metal ions and their behavior when subjected to successive Fe(III) extraction-stripping tests are also presented and discussed.

Jan 1, 2006

By W. A. Lang

"I.-IntroductionAn attempt bas been made in this paper to provide a basis for appraisal of the future of the coal briquetting industry in Alberta by outlining the processes used for briquetting various ranks of coal, by specifying the requirements of a briquetted fuel, by indicating .the status of the industry in the United States, by giving developments in Western Canada, by assessing costs of processing, and by discussing briquetting researches in progress. Much of .the detail bas been omitted since this might mask, rather than reveal, the more important phases of the problem. Reference will be made when possible to published articles where many of the details can be obtained.It should be stated at the outset that, in the writer’s opinion, there are three possible developments in Alberta as regards briquetting: (a) an expansion of the briquetting of the fines of • non-coking and coking coals of semi-anthracite, and of low and medium volatile bituminous rank; (b) the processing of the fines of high-volatile C bituminous coals; and (c) the upgrading of the lower rank high-moisture sub-bituminous coals. Details of the chemical and physical properties of these coals can be obtained in publications of the Research Council of Alberta (1, 2), and of the Fuel Research Station, Bureau of Mines, Ottawa (3).Semi-anthracite and low and medium volatile bituminons coals occur in the mountain areas of Alberta, where, during the upthrust of the Rocky mountains, the coal beds served as the sliding surface. This resulted in the coals being; crushed and consequently they contain a h1gh percentage of fines. In some cases they are high in mineral matter and require to be cleaned before being processed. However, the cleaning of fine coal is both difficult and costly. Both the amount of fines present in the mine-run coal and the amount of mineral matter associated with the coal have increased through the introduction of mechanized mining and through the recovery of coal by stripping operations."

Jan 1, 1950

By J. J. Laffin

In the pursuit of comfort and safety, the wonders of science have given us controlled heating and cooling, thus enabling us to enjoy all the aspects of present-day living to an extreme never previously •envisaged. Man's attempt to conquer the elements largely involves con-trolling the temperature around him. Without having conquered this aspect, his body energy would be consumed in trying to maintain physical comfort, rather than being invested in the explorations which have resulted in man's control over the forces of nature. The indirect methods used to obtain the most agreeable temperature environment were developed because of the natural tendency to strive for increased safety, convenience and comfort. Until the twentieth century, when heat generated by atomic fission became a reality, man's only source of heat, except for that of the sun, came from his discovery of fire.

Jan 1, 1962

By S. Kelebek, B. Ingram, C. Gibson, T. MacNeil, M. Aghamirian

"The beneficiation and upgrading of pyrochlore from its ores is carried out through flotation. In industrial practice, upgrading is conducted in a two-stage flotation process in which pyrochlore flotation is carried out after gangue mineral pre-flotation (carbonate, silicate, sulphide or phosphate reverse flotation). In this study, the flotation of pyrochlore from a low grade carbonatite ore was performed at the laboratory scale following a two-stage flotation process in which carbonate minerals were floated in advance of niobium minerals. In parallel, a simplified flotation process was developed in which pyrochlore was floated directly from gangue minerals at increasingly acidic pH. Laboratory results indicated that both two-stage and direct flotation provided similar results in terms of niobium grade-recovery. Based on these results, a large scale, integrated pilot plant was conducted using a direct flotation flowsheet. While the elimination of reverse gangue flotation resulted in flowsheet simplification, the dissolution of carbonate minerals and the subsequent effect of dissolved cations on the floatability of pyrochlore added an element of complexity. A comparison of results from locked-cycle laboratory testing and pilot plant testing highlights the challenges of scaling up a complex flowsheet. A case is made for the direct flotation process and the key parameters to achieving success in large scale direct flotation of pyrochlore are discussed.INTRODUCTIONPyrochlore (Ca,Na)2Nb2O6(OH,F) is a niobium bearing mineral which has been the primary global source of niobium since the first pyrochlore mine commenced operations in the late 1960s (Gibson et al., 2015a). Preceding the discovery and development of high grade pyrochlore deposits in North and South America, the majority of global niobium supply came from gravity concentration operations of columbite (Fe,Mn)Nb2O6, across Africa (Perrault and Manker, 1981)."

Jan 1, 2016

By R. E. Martin

"The Westerose Leduc (D-3) pool, a Devonian reef reservoir situated in Central Alberta, Canada, has now been producing for over seven years. As a unit operation, the pool pro-vides an interesting example of the full exploitation of gravity segregation tendencies. The reef has a 238-foot oil column, underlain •by bottom water and over-lain by a substantial gas cap. The original hydrocarbons in place were 147.96 million STB oil and 94.4 MMMCF of Taw gas cap gas. Nine-teen producing wells on 80-acre spacing have been completed, most of which are highly productive. Gas injection operations return solution gas to the gas cap. A study of the rock and fluid properties of the pool show it to be conducive to production by gravity segregation at high rates. Monthly average producing rates have varied between 800 B/D and 8,000 B/D and have recently totalled 3,000 BID to 5,000 B /D. Recovery and performance predictions under partial pres-sure maintenance at 10,000 BID indicate an ultimate recovery of 66 per cent of the original oil in place. In the absence of pressure maintenance, recovery would be only slightly less."

Jan 1, 1960

By W. Beres

Many non-commercial operators are currently faced with the need to operate fleets of legacy gas turbine engines. How long such engines can be kept in service safely, without replacing a significant portion of their aging structural components, has become a growing concern to engine life-cycle managers, due to uncertainties in the remaining lives of critical components of these engines. This paper describes the application of the damage tolerance methodology to predict safe inspection intervals (SII) for critical components of gas turbine engines, using components of a turboprop engine for a transport aircraft as examples. High temperature components of this engine are made of advanced aerospace alloys. The methods of predicting three-dimensional fatigue crack growth at the critical location of turbine discs and spacers using both commercial and in-house developed algorithms are presented. Sensitivity analyses are performed to determine the effect of variations in material parameters on the predicted safe inspection intervals. In addition, spin rig tests performed for both turbine discs and spacers are described. Finally, crack growth rates predicted by numerical analyses are compared to those obtained from spin rig testing and the damage tolerance of the turbine components is assessed.

Jan 1, 2015

By K. Yamaguchi

"This Precious metals content copper scrap is treated with a copper smelting process, and copper and precious metals are recovered. The precious metal lost in the slag is increasing with increasing of treated scrap amount. To determine the portion of the precious metals chemically dissolved and that associated with the mechanically trapped matte in the slag will be a key factor to improve the recovery of those metals. The distribution of precious metals between copper matte and FeOx-SiO2 slag phases is determined at 1300 oC and a fixed partial pressure of SO2 of 0.1 atm for the matte grades from 40 to 70 mass% of copper. The distribution ratios show a tendency to increase when the grade of matte is increased. In addition, the solubility of platinum and rhodium in the FeOx-SiO2-CaO slag under the air and the solubility of platinum in the FeOx-SiO2 slag equilibrated with a pure platinum or the Pt-Cu alloy were determined at 1300oC in the range of oxygen partial pressure from 10-9 to 10-7. The solubility of platinum and rhodium in the slag tends to increase with increasing content of copper in the slag and oxygen partial pressure. INTRODUCTIONThe stringency of the supply and demand of platinum group metal (PGM) intensifies by localization for resources and increase of the demand for PGM, furthermore, smelting and the recycling of PGM in the nonferrous smelting process take an important role. Scrap containing a precious metal for the purpose of collection of PGM is treated by copper smelting recently. With increase of the treatment amounts, loss of PGM in slags is the serious problem.In considering of PGM loss in slags, knowledge of the distribution behavior for PGM between slag and matte phases or slag and copper phases and the PGM solubility in slags is important. The distribution ratios of silver and gold between the FeOx-SiO2 slag and the Fe-Cu matte were reported by Roghani (Roghani et al., 2000), Shinha (Shinha et al., 1985) and Takeda (Takeda et al., 1993) However, there is no data for the PGM distribution ratio. On the other hand, the PGM solubility in slags was reported by Sano (Sano et al., 1997) However, there is very few report for the solubility of PGM in the nonferrous smelting slags."

Jan 1, 2012

By W. Kunda, J P. Warner

SHERRITT GORDON Mines Limited annually produce 300,-000 pounds of pure cobalt by processing a nickel-cobalt-copper-iron sulphide ore which is mined at Lynn Lake, Manitoba. The ore (containing 0.04 per cent Co) is •concentrated to give a concentrate containing l 1-12 per cent nickel, about 2.0 per cent .copper, and 0.25-0.35 per cent cobalt, which is treated at the Refinery in Fort Saskatchewan, Alberta. The concentrate is leached in an ammoniacal solution of ammonium sulphate using compressed air as the oxidant. After filtration the leach solution contains, besides nickel and cobalt, copper ammines, sulpharnates and salts of various thionic acids. The copper is removed by precipitation as sulphide and the sulphur compounds converted to ammonium sulphate by a combined oxidation and hydrolysis treatment. The purified solution •Containing about 45 gpl of nickel and 1 gpl of cobalt is treated with gaseous hydrogen under pressure at 350°F to precipitate metallic nickel powder, the precipitation 'being terminated when the nickel content of the solution is about 0.8-1 gpl. Only about

Jan 1, 1962

Traditionally within the mining industry, single models for both grade and geology of orebodies are created upon which all mine development decisions are based. These models provide a single interpretation of the extent and continuity of the mineralization envelope based on solids and sections interpreted from relatively wide spaced drilling i.e. the models infer behaviour of grade and geology at smaller/local scales based on data available at wider scales. The variable behaviour of grade and geology cannot be derived from single kriged resource models. In recognition of this, Newmont Mining Corporation typically uses Sequential Gaussian Simulation (SGS) to quantify grade variability and to determine its effect on some of these mine development decisions. In most of these studies the mineralized envelope remains fixed and grade simulations are generated within a fixed volume. To account for uncertainty in the geology/ mineralization envelope Newmont Mining Corporation has been experimenting with Multiple Point Statistics (MPS). Multiple-Point Statistics is an emerging technique, which can be used to generate multiple, geologically realistic, realizations of data that displays complex non-linear features. MPS uses a conceptual model of the geology, called a Training Image (TI), to infer these high-order spatial relationships. The multiple realizations allow for an assessment of the geologic uncertainty, which can be further combined with grade simulations to generate a more complete picture of the true uncertainty of a mineral deposit.

Jan 1, 2011

By W. R. Cowan

The Caledon Outwash is a large deposit of glaciofluvial gravel and sand located 55 km north west of down town Toronto. For the most part it was laid down in a meltwater channel fronting the Paris Moraine about 14,000 years ago. Applying the braided bar model of Eynon and Walker (1974) the principal facies present are imbricated coarse gravels (bar corefacies); crudely stratified, imbricated bar top sandy gravels; and trough crossbedded side channel sands and gravelly sands. Of lesser importance are crossbedded bar front gravels, shallow braided stream facies gravels, and stoss side facies sands and pebbly sands (rare). Lithologically these deposits are characterized by FIGURE I. Geological relationships of Caledon Outwash. Industrial Minerals in Canada up to 95% Ordovician limestone and siltstone in the gravel fraction. A siltstone content of up to 34% requires that beneficiation be carried out for the production of better quality aggregates. Resources remaining are estimated to exceed 500 million tonnes in 3000 ha of the most suitable part of the deposit. Present production is about 4.5 million tonnes per year, shared by several producers.

Jan 1, 1984

By N. T. Oo, L. D. Hutton

"The Banora Point Upgrade Project is a 2.5km long six-lane divided freeway in northern New South Wales, Australia. The geology at the project area comprises a volcanic succession of variably weathered basalt flows and agglomerate deposits that reach 48m in thickness and overlie Mesozoic sedimentary rocks. A site specific rock classification system was developed that characterised all the rock units based on the engineering properties governing the rock mass behaviour i.e. intact rock strength and defect characteristics (spacing, aperture, infilling, wall roughness and weathering) irrespective of the geological origin. This approach simplified the design and the on-site verification processes. Based on this classification system, rigorous quantitative statistical assessments of the available geological information including various laboratory and field testing were performed to derive the geotechnical design parameters for various rock classes. These parameters were used to complete geotechnical designs of retaining wall systems. INTRODUCTIONThe Banora Point Upgrade Project is a 2.5km long six-lane divided freeway in northern New South Wales, Australia. The key features include two interchanges, a 300m long viaduct, a large cutting through Sexton Hill with an associated 100m wide Land Bridge and retaining walls reaching 490m long and up to 22m high. This paper focuses on the derivation of representative geotechnical parameters for geotechnical design of the retaining structures supporting Sexton Hill Cutting including bored pile retaining walls and soil nail walls. The geology at the project area comprises a volcanic succession of variably weathered basalt flows and agglomerate deposits that reach 48m in thickness and overlie Mesozoic sedimentary rocks. Due to the complex geological nature of the site, an understanding of the regional and local geology, the typical behaviour of individual geological units and the implication of onsite variations from design intention are the ultimate challenges to the geotechnical engineer in order to select representative geotechnical parameters for design."

Jan 1, 2015

By M. Abouhamad

According to the Canadian Urban Transit Association (CUTA), 140 Billion CAD is required to maintain, rehabilitate, and replace subway infrastructure between 2010 and 2014. The current practice adopted by transit authorities for prioritizing subway stations for rehabilitation is based on the station structural needs. While this classification is reflective of station condition, other factors, such as station size, location and passenger capacity, play an important role. The criticality of a station is an index that represents the functional importance of a station depending upon a set of identified factors. The system criticality is based on several attributes, such as station location, size, and nature of use. This paper presents a novel method of clustering subway stations for rehabilitation priority based on their criticality level. The different stations in a subway network are rated according to their relative importance against predefined attributes. The weights and scores of the attributes are computed with the help of experts and current subway network data. The analysis is done using the Fuzzy Analytic Network Process (FANP) to accommodate the subjectivity of human judgment as being expressed in natural language which entails ?fuzziness? in real-life problems and account for the interdependency between the selected attributes. The output of the model is a criticality based clustering of subway stations. The proposed framework helps authorities prioritize stations for rehabilitation and highlight stations with more criticality for a more robust asset analysis.

Aug 1, 2013

By Yong-neng Feng, Xiao-ping Chen, Wei Guo

"While the uniaxial compressive strength of rock has been extensively investigated, the relation between the saturation and natural compressive strength is relatively unexplored. This paper studies on 1865 statistical data of Chongqing Rail Transit Line 1 and Line 6, which located in the Middle Jurassic of Shaximiao formation. The research focuses on the relation between the saturation and natural compressive strength. The statistical data are categorized and quantified in order to ascertain the softening properties of sandstone and sandy mudstone. The findings suggest that the saturation compressive strength is significant effected by its natural compressive strength, and an empirical formula is introduced to explain the relation. These findings have implications for researchers and engineer who concerned with Chongqing rail transit construction.INTRODUCTIONIn the engineering construction and surrounding rock classification, the uniaxial compressive strength index (Ministry of Water Conservancy, 1995; Ministry of Railways, 1999) is one of the essential parameters of rock mass. Usually, there are two types of the uniaxial compressive strength index, natural and saturation compressive strength, and the ratio of them is the softening coefficient. Most of the previous studies on rock strength had focused on the influence factors (Liu et al., 2008; Liu et al., 1998; Liu et al., 2013; Wang, 2013; Zhang et al., 2008; Zhang et al., 2010; Zeng & Lin, 2003) with experiment and in-situ tests. But few publications that reports a long and formal research project on the relationship between natural and saturation compressive strength. In order to figure out this issue, this study investigated the distribution of Solidity Classification of Rock Mass and softening coefficient based on the statistical data of Chongqing Rail Transit Line 1 and Line 6. Based on the analysis, an empirical formula was proposed to explain the relationship."

Jan 1, 2015

By Dharmendr Kumar, Pradip, Sivakumar Subramanian, Beena Rai, Venugopal Tammishetti

The separation efficiency in a mineral processing plant is generally assessed and reported in terms of elemental assays constituting the minerals of interest. However, different minerals comprising of same elements behave differently under similar process conditions. Thus, it is imperative to track the mineral composition thank elemental composition of different streams in a processing plant. The availability of automated mineral analyzers such as QEMSCAN and TESCAN in recent times has made it possible. However, due to the high cost and expertise required, their adaptation in day to day monitoring of operations is not yet a common place. X-ray diffraction (XRD) profile fitting (Rietveld Refinement) is another technique which can provide estimates of mineral proportions in a sample. The results of Rietveld Refinement however are affected by coating of fines on coarse particles, method of sample preparation, particle size distribution of sample, elemental substitution in mineral crystal lattice. In the present work, we propose a simple and efficient method for quantitative estimation of minerals in iron ores using elemental assays and thermo-gravimetry analysis data. The minerals (hematite, goethite, gibbsite, kaolin and quartz) are identified using powder XRD analysis. It is also observed that goethite contains Al substitution in the crystal lattice. The samples were analyzed for %Fe, %Al2O3 and %Silica using chemical analysis. The measured Loss on Ignition (LOI) in the sample is contributed from goethite, gibbsite and kaolinite phases. LOI from gibbsite and goethite occur in temperature range 250–350°C and LOI from kaolinite occur in temperature range 400–700°C. According, LOI are determined in two different temperature ranges that are 100–400°C and 400–850°C. We have used the data to successfully determine the mineral compositions of iron ore samples. We have also employed a data reconciliation algorithm on the calculated data for further improvement and consistency of our results. Our method is very convenient for quick estimation of mineral proportions in a sample. The proposed method can also be used for quantitative phase estimation in bauxite ores and red muds.

Jan 1, 2016