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By J. Muralha, L. Lamas

"Given the results of triaixial tests, regressions are commonly used to evaluate the parameters of failure criteria that model intact rock strength and to perform statistical inferences used to evaluate characteristic values defined in EC7. Statistical robustness of these inferences is affected if the basic hypothesis underlying regression are not met, namely homoscedasticity (constant variance of the errors). This paper presents analyses of 23 sets of triaxial tests, starting by the evaluation of the regression parameters of the Mohr-Coulomb linear criterion and of the Hoek-Brown non-linear criterion, followed by carrying several statistical tests to check the homoscedasticity null hypothesis of independence between the variance of intact rock strength and the confining stress.INTRODUCTIONThough rock engineering design is clearly included in the scope of Eurocode 7(EN1997-1), its implementation raised a wide discussion regarding the applicability of structural safety concepts to geotechnical design of construction works in or on rock masses. The basis of the limit state design philosophy adopted in EC7 is that, for each particular design situation, all the possible limit states for a structure, or part of it, shall be considered and that it shall be demonstrated that the likelihood of any limit state being exceeded is sufficiently small. Though EC7 allows the limit states to be verified by one or a combination of methods, use of calculations is by far the most used, and it is often confused with the EC7 itself. It involves using characteristic values of actions, ground properties and geometrical data, as well as obtaining their design values by the partial factor method.Characteristic value of a given material property is defined in Eurocode (EN 1990) as: “value of a material or product property having a prescribed probability of not being attained in a hypothetical unlimited test series. This value generally corresponds to a specified fractile of the assumed statistical distribution of the particular property of the material or product”. As regards the design value of a material or product property, according to the Eurocode it is a “value obtained by dividing the characteristic value by a partial factor”."

Jan 1, 2015

By N. W. Hendry

ABSTRACT Exploration by geophysical methods and diamond drilling of an occurrence of chrysotile asbestos, located ten miles east of Matheson, Ontario, was commenced on March 25th, 1949, by the Canadian Johns-Manville Company, Limited. The asbestos is associated with a narrow sill-like body of basic and ultrabasic rocks which strikes northwesterly across portions of Munro and Beatty townships. To date, asbestos zones of commercial interest, many hundreds of feet in length, width, and depth, have been outlined by diamond drilling along a 2-mile length of serpentine. The fractures occupied by the asbestos veins are closely associated with the regional faulting in the area. The mining of the first occurrence, or A orebody, will be by open-pit methods. Milling will commence at a rate of 50 tons an hour. INTRODUCTION OCCURRENCES of chrysotile asbestos in Munro township have been known at least since 1914 and references to them appear in reports published by the Ontario Department of Mines in 1915 (1) and 1919 (2). J. G. Ross (3) in his excellent publication on Chrysotile Asbestos in Canada, mentions an occurrence in Munro township. The area was first mapped in detail by J. Satterly, of the Ontario Department of Mines, in 1944, and brief mention is made of chrysotile asbestos in Satterly's preliminary report (4), which was published the following year.

Jan 1, 1951

By G. W. Toop

"The Cominco smeller in Trail, British Columbia, is a large integrated lead-zinc production facility. In the plant description, emphasis is given to the pyrometallurgical operations including zinc concentrate roasting, lead singer-blast furnace processing and silver refining. Production figures for the main metal products - zinc, lead, silver and gold - are provided.IntroductionIncorporated in 1906, Cominco Ltd. is an integrated natural resource company with principal activities in mining, smelting and refining, mineral exploration, fertilizer production and electrical power generation.Cominco is one of the world's largest producers of zinc and lead, accoW1ting for about 10070 of mine production in the western world. The company also produces and sells copper concentrate, copper sulphate, copper arsenate, sodium antirnonate, silver, gold, cadmium, bismuth, indium, and germanium dioxide and a range of fertilizers and sulphur products.Zinc OperationsRoastingThe roasters currently treat about 1400 t/d of zinc concentrates. Over half of the total concentrate treated originates from the Red Dog Mine in Alaska. During the summer, concentrate is shipped from Alaska to Vancouver where it is loaded into rail cars and hauled inland, transferred to trucks and delivered to Trail. The remainder of the roaster feed is made up of Sullivan concentrate and various custom concentrates. These arrive either by train or by truck.There are three roasters available for roasting the concentrate. The two major roasters are Lurgi fluid bed units. Each Lurgi roaster can process concentrate at about 1:7 tonnes per hour (tlb). A smaller Cominco suspension roaster with a capacity of 10 tlb is also used. The flowsheet for the high temperature section of the fluid bed circuit is shown in Figure 1.Concentrates fed to fluid bed roasting are conditioned with 7 1/min water to give 8% moisture in feed. Two slinger belts throw the mixture into the fluidized bed. The fluid bed roasters are 10.4 m in diameter with a bed depth of 1 m. Grate area is 84 m2• Normal operating conditions include bed temperatures of 930°C to 950°C, fluidizing air at 750 Nm3/min and a wind box pressure of 2000 mm H2O."

Jan 1, 1994

By M. Staite

This paper analyzed the feasibility of converting a 5kW natural gas SOFC power generator system designed to operate on natural gas to be fuelled by methanol. The analysis included laboratory methanol fuel processing experimentation, methanol reformate SOFC cell testing, and SOFC system mass and energy balance modelling. Methanol fuel processing experimentation indicated that theoretical reformate compositions can be achieved for high temperature (600-900°C) methanol steam reforming. A 6% open circuit voltage decrease and a 10% peak power current density decrease between cell operation on humidified hydrogen and methanol reformate was observed. SOFC system mass and energy balance modelling indicated that a natural gas SOFC system can be converted to operate on methanol fuel with minimal (1%) efficiency impacts, however the systems' thermal integration can be impacted.

Jan 1, 2005

By Gordon S. Farnham

THIS paper summarizes the results of investigations carried out at Sydney Mines, N.S., and at Ottawa, following the disaster at Princess colliery, December 6th, 1938. The Honourable Minister of Mines for Nova Scotia appointed A. E. Cameron special investigator to enquire into and report upon the cause of the rope failure. Public hearings were held in Sydney Mines and evidence taken from many witnesses. The site of the accident was examined in detail and investigations made of the rope layout and colliery practice. At the request of the special investigator, the Department of Mines and Resources, Ottawa, kindly undertook technical and scientific examination of the broken ends of the rope. These investigations were carried out in the Metallurgical Laboratories of the Department of Mines and Resources, under the supervision of G. S. Farnham, Metallurgist for the Department. Valuable assistance in interpretation of many features of the investigation was received from other sources. Acknowledgment is due to Messrs. Stuewe, McCall, and Gordon, and other members of the staff of the Dominion Steel & Coal Corporation; to Messrs. Morrison and Scott, and other members of District 26, United Mine Workers of America; and to Messrs. Timm, Parsons, Haycock, Haanell, and other members of the staff of the Department of Mines and Resources, Ottawa, for helpful ad vice and technical assistance in assembly of information, and preparation of material and interpretation of evidence obtained.

Jan 1, 1939

By H. J. McQueen

Pressure welding is a solid state joining technique that depends on bringing the parts into sufficiently close contact that inter-atomic bonds are achieved. Pressing is more effective at elevated temperatures where plastic flow causes the asperities to collapse; improved application conditions are derived from hot-work research to clarify temperature and strain rate dependence of hot strength and ductility. The substructure evolution systematically studied in hot working to determine dynamic recovery or recrystallization is applied to clarifying that developed in welding. The various processes are affected differently by work-piece geometry and final shape requirements. In addition to pre-cleaning of the surfaces, the plastic flow helps disperse the remaining oxide layers as was originally exemplified in blacksmith hot forging of layered sword blades and in bellldie welding of wrought iron tubes. The presentation critically compares the utility for various materials and configurations of simple pressure, ultrasonic application, diffusion, explosive, rotary and linear friction and friction-stir processes. Diffusion bonding (primarily Ti) with light cleaning, low pressure, little distortion in protective furnace atmosphere contrasts strongly with the heavy upsetting in friction welding, or complex alloy mingling and substructure variations in friction stir joints.

Jan 1, 2011

By S. Nikolic, H. M. Henao

"There is renewed interest in the improvement of existing copper smelting processes and the development of new technologies. It has become clear that further accurate information on slag properties, in particular, on phase equilibria are required in order to optimize these processes. It is in this context that improved experimental research methodologies have been developed specifically to provide information on phase equilibria at the oxygen partial pressures encountered in copper smelting practice. The methodology involves synthetic slag equilibration at controlled gas atmospheres, quenching and measurement of compositions of phases with an electron probe X-ray microanalyser (EPMA) with wavelength dispersive detectors (WDD). Application of modem analytical tools and careful design of experiments greatly improve accuracy of determination of phase equilibria in complex, multi-phase slag systems. New experimental data on phase equilibria for the copper smelting and converting silicate slags at controlled oxygen partial pressures in the temperature range between 1200°C and 1350°C in the ""Fe0""-Ca0-SiO2 system and in the ""Cu20""-""Fe0""-Ca0-Si02 system in equilibrium with metallic copper are reported, and differences between various data sources are analyzed."

Jan 1, 2007

As a bubble travels through the pulp region of a flotation cell, it will collect the most hydrophobic particles of an intermediate particle size range, this being the primary source of true flotation selectivity. Despite its role on bubble-particle attachment, however, particle hydrophobicity is still missing a mathematical definition that can be used for plant simulation. In this paper, particle hydrophobicity is defined in terms of the induction time necessary for attachment and then linked to the mass of collector adsorbed per particle. This allows particle hydrophobicity to be written as a function of density of collector adsorption as well as particle size and mineralogy. The model is calibrated from the experimental measurement of the flotation rate constant. Liberation data from an industrial flotation rougher is used for model validation. It is demonstrated that the model can describe a broad experimental dataset by means of a minimal number of parameters. Main industrial application is in simulating the effect of the chemical environment upon plant metallurgical performance.

Jan 1, 2006

By R. K. Jonas

"Pressure leaching and pressure oxidation in autoclaves are important alternatives in the extractive processing of gold, copper and nickel ores. The application of advanced control to pressure leach and pressure oxidation autoclaves could achieve significant benefits as has been shown in alumina pressure leaching. This paper compares and contrasts alumina digestion autoclaves to other mining autoclaves with respect to advanced controls. The application of advanced control in alumina with over 30 units controlled worldwide, and its benefits will be reviewed. The design and potential benefits from advanced control for pressure oxidation and leaching will be presented.INTRODUCTIONIt is this author's position and the purpose of this paper to propose that advanced control could be effectively applied to autoclaves in the nickel, gold, and copper mining processes. This is based on the proven effectiveness of advanced control on autoclaves used in the alumina industry for pressure leaching of bauxite ores. Incremental, but significant increases in production could be realized by applying advanced control to autoclaves, as evidenced by the alumina industry, and this not being implemented in other autoclaves in the mining industry.In addition, today the mining industry is being challenged to improve their production methods. In some markets like nickel, there is pressure to improve productivity and reduce the cash cost per ton. While in other markets like copper and gold, demand is vigorous with favourable pricing, and there are advantages to increase production and productivity given limited plant capacity. Advanced control has proven its capability to improve mineral processing operations through increases in throughput, recovery, as well as reducing variability. In today's mines, autoclaves are being used to a much larger scale and with much larger importance, thus it would be beneficial to improve operational performance through the use of advanced control.Accordingly, it is the author supposition that an opportunity exists in the mining industry to use a proven advanced control technology to improve the operations and financial performance of mines using autoclaves."

Jan 1, 2012

"Block caving is the preferred underground mining method to profitably extract massive, low-grade orebodies; however, lack of cave access inhibits understanding the rockmass response to mining, which is needed for safer, more productive operations. Combining large datasets from multiple sources with virtual reality scientific visualization (VRSV) is an alternative method for understanding complex cave behaviour, by providing virtual access to the cave. A customized VRSV module was developed at UNSW Australia to investigate rockmass response to undercut developments at a case-study block caving operation. Time/sequence effects are investigated in rockmass response to blasting, which is an important factor in hard-rock mines.RÉSUMÉ La méthode d’extraction souterraine par blocs foudroyés est la méthode préférentielle pour extraire rentablement des gisements massifs à faible teneur. Toutefois, le manque d’accès à la chambre restreint la compréhension de la réponse de la masse rocheuse à l’exploitation, ce qui est nécessaire pour obtenir des opérations plus sécuritaires et plus productives. La combinaison de grands ensembles de données de multiples sources avec la visualisation scientifique par réalité virtuelle (VRSV) constitue un autre moyen de comprendre le comportement complexe de la chambre en fournissant un accès virtuel à la chambre. Un module de VRSV sur mesure a été développé à l’Université de Nouvelles-Galles du Sud (UNSW) en Australie afin d’étudier, dans une étude de cas d’une exploitation par blocs foudroyés, la réponse de la masse rocheuse aux développements de galeries de sous-cavage. Les effets de temps/séquence sont étudiés dans la réponse de la masse rocheuse au sautage, ce qui est un facteur important dans les mines de roches dures."

Jan 1, 2016

By Wignall. T. K., J. De Geoffroy

Statistical models are fitted to the observed distributions of eighteen characteristics of the population of commercial porphyry deposits of North and South America. The statistical base required for the formulation of the statistical models includes 58 commercial porphyry-copper-molybdenum deposits of the Cordilleran Belt from which geological, geometric and economic data were collected. Predictive and composite models are derived from the statistical study to assist explorat10n. planning, engineering studies and fmanc1al analyses as required for the development of new porphyry deposits in the Cordilleran Belt.

Jan 1, 1973

By P. F. Venus

In December 1977, a large pillar was removed by blasthole mining methods at lnco's Creighton No. 3 mine. Although the 2,363.000-ton blast was not a size record for a single underground blast at Inco, it did represent a significant departure from conventional blasthole mining. In terms of the application of nominal 6-inch-diameter boreholes underground, coupled with bulk slurry explosives, the magnitude of the blast is considered a first and very important development. The application of large-diameter boreholes in underground operations was first tried successfully in 1973. Since that time over 13/4 million feet have been drilled in this adaptation of an open-pit technique to underground operations. The blast, which required 708 holes, totalling 131,500 feet of drilling, was loaded in a six-week period, using special slurry handling techniques developed jointly by Inco and CIL. Inco operating and engineering personnel consider this application of large boreholes and slurry explosives for blasthole mining a very important milestone in modern mining technology.

Jan 1, 1978

By W. G. Brissenden

"ALTHOUGH I SHOULD FIRST REVIEW the state of the mining art as it is today, because of the shortness of time I will confine myself to a re-view of the more important advances in that art which have been made in the past two to three decades. Then, a look at the opportunities and the challenges which now present themselves will be more meaningfulFirst, some of the more impor-tant developments in underground mining:(1) The recognition that good ventilation, visibility and working conditions are essential preliminaries to efficient production has resulted in their incorporation as a matter of practice in modern mine planning. (2) The introduction of the car-bide bit and the re-introduction of the airleg drill, and the resulting sharp rise in productivity, were early postwar developments. (3) The recovery of the coarser fraction of mill tailings for use as mine backfill also is an important cost-reducing development of recent years -and this has led to cemented backfill, which, al-though more expensive, meets certain specific needs and has tremendous potential. (4) Great strides have been made in improving explosives' materials and explosives' accessories. Millisecond-delay electric blasting caps, which improve fragmentation and reduce the seismic effect of blasting, and the development and •application for underground use of explosives are but two among many such improvements. (5) Trackless mining methods, using quarry-type equipment in some instances and specially de-signed low-headroom trucks, loaders and carrier-mounted drills in others have been successfully applied. (6) Dual-purpose load-haul units are now in use loading and hauling from open stope drawpoints, and smaller versions of this type of unit are in use in cut-and-fill and other types of stopes."

Jan 1, 1968

By Tobias Riedel, Peter Ay, University of Applied Sciences, Bianka Bade, Nicole Pausch, Bernhard Gemende, Florian Logsch, Matthias Leiker, Satyanarayana Narra, Claudia Glaser

This study focusses on the production of micro-structured agglomerates with high porosity from iron (III)-hydroxide-containing materials as adsorbent. A fractal-like structure of the agglomerates was created through a two-stage agglomeration process. Developing porous structures was necessary to increase the adsorption capacity. Various materials were used for the agglomeration experiments: i) filter cake (dry matter content 23 to 27 wt.-%); ii) FerroSorp®DGµ, a product which is already being used commercially for various applications in water cleaning. These materials in the pristine state have different characteristics such as dry matter content and particle size distribution. The desired optimised agglomerates can be achieved with the help of additives or binders, respectively. Additionally, the agglomeration process parameters play a vital role. In order to produce agglomerates with high porosity, the process was carried out in two steps. Firstly, FerroSorp®DGµ (d90 < 30 µm) was agglomerated jointly with the aforementioned filter cake in an Eirich intensive mixer (particle size range 125 µm < d90 < 500 µm). The second agglomeration step post drying was carried out in a pelletisation disc or in an Eirich intensive mixer with the addition of polymeric binders (up to particle sizes ranging from 2 to 4 mm). Agglomerates were characterised both in short and long term loading tests using phosphate as model ion. Contact times were less than 10 min, similar to practical application in percolation columns, or more than 7 days, respectively. The results show that the agglomerates produced in the two-stage pelletisation process have more advantageous properties like better accessibility of the active sites obtained by specificly influencing the particle size distribution during the two-stage pelletisation process.

Jan 1, 2016

By Kretschmar. U. H.

Fieldwork in the Meguma of Nova Scotia and Archean equivalents shows that bedding-parallel quartz lode gold veins (LVs) commonly occur at the top of graded elastic sequences. We define a "gold cycle" (GC) by analogy with Bouma turbidites and show that most "shear zones" and "lamprophyres" correspond to the upper pelagic-pelitic (E) division. We describe GCs from Archean Chester Twp, ON; Elmhirst, ON; Bourlamaque, QC; "intrusions" and interpret them as crystal tuffs and tuff-breccias. Extensive early Archean pyroclastic volcanism is implied: the genesis of trondjhemite-tonalite-granodiorite (TTG) rocks must be re-examined. The geopetal nature and asymmetric alteration of LVs indicates genesis from sea-floor hydrothermal vents. Textures suggest that often quartz was deposited as a gel. Vent geometry (fracture, point source or diffuse seep), bottom topography and vent spacing is reflected in wade-thickness plots. GC facing directions survive metamorphism. The Bourlamaque batholith was a flat-lying sheet of quartz-feldspar-hornblende crystal tuff, and isoclinal folding has repeated one or more gold-bearing horizons. Syngenesis clarifies and simplifies LV formation with major implications for models. Exploration becomes more cost-effective. Basin analysis, whole rock geochemistry, ore lens geometry and vent spacing can be used.

Jan 1, 2011

By C. F. Chung, F. P. Agterberg

"Prediction of a variable sulphur content in Cape Breton seams is important for planning the production of a highgrade metallurgical coal. Two extrapolation methods (Kriging and a version of Universal Kriging) to predict sulphur content in blocks of coal before mining are presented and applied to the New Lingan Mine reserves in the Harbour seam. The uncertainty of the predicted values is expressed by using standard deviations. Some statistical results for the Phalen seam, which occurs about 400 ft below the Harbour seam, are presented for comparison. The two mathematical models consist of two sets of equations which have been used in computer algorithms. Some limitations of the present approach and possibilities for further statistical work are indicated."

Jan 1, 1973

By W. G. Miller

An overall study was conducted to evaluate the properties and processes influencing the rate and magnitude of consolidation for oil sands fine tailings produced using different extraction processes. As part of this overall study, consolidation tests using slurry consolidometers were carried out for caustic and non-caustic fine tailings. The influence of a change in bitumen extraction process (caustic versus non-caustic) on consolidation properties, namely compressibility and hydraulic conductivity, was determined, as was the effect of adding a coagulant (calcium sulphate [CaSO4]) to caustic fine tailings. For fine tailings originating from two different oil sands ores (Ore A and Ore B), results were presented in terms of variation in average void ratio with time (settlement), void ratio with effective stress (compressibility), hydraulic conductivity with void ratio and coefficient of compressibility and hydraulic conductivity with sodium adsorption ratio. Findings indicated that chemical characteristics of fine tailings (water chemistry, degree of dispersion) do not have a significant impact on their compressibility behaviour and have only a small influence at high void ratio (low effective stress). The biggest advantage of non-caustic fine tailings and treating caustic fine tailings with coagulant is an increased initial settlement rate and slightly increased hydraulic conductivity at higher void ratios. Thereafter, compressibility and hydraulic conductivity is governed by effective stress.

Aug 1, 2010

By W. G. Miller, J. D. Scott, D. C. Sego

An overall study was conducted to evaluate the properties and processes influencing the rate and magnitude of consolidation for oil sands fine tailings produced using different extraction processes. As part of this overall study, consolidation tests using slurry consolidometers were carried out for caustic and non-caustic fine tailings. The influence of a change in bitumen extraction process (caustic versus non-caustic) on consolidation properties, namely compressibility and hydraulic conductivity, was determined, as was the effect of adding a coagulant (calcium sulphate [CaSO4]) to caustic fine tailings. For fine tailings originating from two different oil sands ores (Ore A and Ore B), results were presented in terms of variation in average void ratio with time (settlement), void ratio with effective stress (compressibility), hydraulic conductivity with void ratio and coefficient of compressibility and hydraulic conductivity with sodium adsorption ratio. Findings indicated that chemical characteristics of fine tailings (water chemistry, degree of dispersion) do not have a significant impact on their compressibility behaviour and have only a small influence at high void ratio (low effective stress). The biggest advantage of non-caustic fine tailings and treating caustic fine tailings with coagulant is an increased initial settlement rate and slightly increased hydraulic conductivity at higher void ratios. Thereafter, compressibility and hydraulic conductivity is governed by effective stress.

Jan 1, 2010

By G. Hamel

The LCL&L process (Low Caustic Leaching & Liming) is a patented hydrometallurgical route developed by Rio Tinto Alcan (RTA) to economically process spent pot lining (SPL) generated by aluminum cells. The three resulting end-products (carbonaceous, fluorinated and caustic liquor) are inert and have valorization possibilities. An industrial size pilot plant located in Saguenay (Quebec) was inaugurated in mid-2008 to demonstrate and optimize the technology. This paper describes characteristics of the LCL&L process and the experience acquired by RTA since the plant&apos;s start-up, including ramp-up capacity and technology challenges that were overcome. Possible end-products valorization methods are also presented. The carbonaceous end-product can be separated into carbon and brick rich fractions and used as either alternative fuel, reducing agents, or as raw material for third party processes. The development of a conversion process for the fluorinated end-product would allow its reuse as a substitute to fluorspar mineral for aluminum fluoride production. Finally concentrated caustic liquor is already valorized at the nearby RTA Vaudreuil alumina refinery.

Jan 1, 2011

By B. Karnath, K. Guha, S. Tandon

At Jhagadia Copper Ltd (India), Copper is produced through secondary route using Top Blown Rotary Converter (Kaldo Furnace). The basic raw material being treated includes Matte-slag Reverts, Copper Cakes, dross & Cement, Oxide Ore, Low S bearing Concentrates & various metallics along with high grade copper scraps. The plant has capability to refine & produce Blister grade copper from Kaldo furnace as well as PS Converter . Blister is fire refined in Anode furnace & electro refined in Refinery to produce cathode copper. Our product , Copper Cathode , has already been established in the market as its quality is better than &apos;LME Gr&apos;. The paper deals with the experiences encountered during commissioning & stabilization of the plant.

Jan 1, 2007