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By B. Panton, J. Carvalho, E. T. Brown

"A major consideration in the design of high capacity tiedown anchors for dam, bridge and tower foundations is the tensile resistance of the rock mass to pullout, typically as a result of overturning moments or hydrostatic uplift. Rock mass pullout capacity for installed anchors is developed from the tensile strength and fracture propagation properties of intact rock, the orientation and physical properties of the discontinuities and anchor confinement at depth. The typically assumed, but generally conservative, design approach is to calculate anchor pullout capacity using the dead weight of a uniformly shaped inverted “cone” with an assumed initiation point and breakout angle. In some cases, some tensile or shear strength is considered across the area of the assumed pullout cone, however, these strength estimates are based primarily on based on limited historic testing data, empirical relationships for rock mass strength developed for other applications, and engineering judgement.As an alternative to the current foundation anchor design method, this paper presents a new approach to the rock cone pullout problem using Discrete Fracture Networks (DFN) combined with numerical simulations. The simulations presented in the paper investigate the influence of fractures in a synthetic rock mass on ultimate anchor strength. In addition, the global influence on fracture network statistics on rock mass pullout failure is also discussed and it is contended that some of the aleatory and epistemic uncertainty inherent in the design of rock anchors can be reduced by considering fracture statistics in anchor design."

Jan 1, 2015

By P. R. A. Andrews

"Areas of bubble contact were delineated for cassiterite in the presence of chloride, fluoride, sulphate, phosphate, oxalate and citrate ions using dodecylamine hydrochloride collector. The limits of pH, and the minimum collector concentration were established using the bubble pick-up technique.Bubble contact did not occur below the p.z.c. (point of zero charge), estimated to be 4.7, in the presence of chloride ion, and fluoride ion showed only a weak response in the same pH range. These anions are considered to act as indifferent electrolytes. Activation at pH values below the p.z.c. was obtained with sulphate, phosphate, oxalate and citrate ions; the greatest response was by oxalate and phosphate ions extending pick-up to between pH 2.0 and 2.5.Activation appeared to be strongest when anionic protonated species were in maximum concentration. Strong activation also corresponded to the formation of very stable metal ion species, thought to be formed on the surface of cassiterite, between exposed stannic ions and modifying anions; dodecylammonium ions being absorbed on the surface so modified."

Jan 1, 1991

By R. Baker

A novel electrochemical half-cell and corresponding working electrode were designed to evaluate the electro-catalytic activities of catalysts in an environment close to that of an operating proton exchange or polymer electrolyte fuel cell (PEMFC). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques were employed using the novel cell to characterize various methanol electro-oxidation parameters that contribute to the overall reaction on a fuel cell anode. The effect of temperature on methanol oxidation kinetics was examined in the potential range of 0.31 to 0.65V (vs. NHE). The data was collected in the temperature range of 20 to 80°C. Based on the experimental analysis and literature data, an equivalent circuit model (ECM) for methanol oxidation was proposed and was used to fit the EIS experimental data. The experimental data and ECM electrochemical data was used to extract electrochemical kinetic parameters for methanol oxidation such as the exchange current density, Tafel slope, and energy of activation for the reaction. Kinetic data, especially at different temperatures, is very limited in the literature.

Jan 1, 2005

By Michael J. Sapko, Ellsworth R. Spencer, Frank J. Perzak

"The fire resistance of several mine conveyor belts is evaluated using a new belt-flammability apparatus developed by the U.S. Bureau of Mines. The test apparatus, experimental details and a calculated flammability index (FI) are described.The FI values are useful for ranking the fir e resistance of mine conveyor belts. Values are determined using parameters readily measured with thermocouples, high-temperature flow probes and a methane-oxygen torch, all of which are components of the Bureau's new test apparatus. The FI varies directly with the flame-spread rate and the rate of heat release during burning and varies inversely with the critical (minimum) ignitor energy output.The fire-resistance ranking of nine different belt types using this moderately scaled apparatus is compared with available full-scale data on belt fires. This comparison shows that the ranking based on the FI is consistent with the full-scale data.IntroductionFull-scale fire hazard evaluations of mine conveyor belts are not easily related to the properties usually measured in small-scale flammability tests. The inadequacy of small-scale belt fire tests has been demonstrated in works by Mitchell, Warner and Reinke.Mitchell and Warner showed that certain neoprene (NP) and polyvinyl chloride (PVC) belts, which had been approved by the Code of Federal Regulations 30 CFR 18.65, were nevertheless capable of propagating flame over their entire length when full-scale fire conditions were simulated. Comparable results were also observed by Reinke at the Tremonia experimental mine in Dortmund, West Germany, where all belts burned in full-scale tests even though they passed the small-scale tests. Only by reducing the severity of the full-scale test could these fire-resistant belts be grouped on a pass-fail basis."

Jan 1, 1982

By I. Stefanou, J. Sulem

"In the last thirty years, the study of earthquake mechanisms has emphasized the major role of rock friction. Earthquakes appear to be the result of a frictional instability and occur by sudden slippage along a pre-existing fault or a plate interface. Multiphysics couplings play a major role in earthquake nucleation and seismic slip. The effect of shear heating and thermal pressurization may be of prime importance in the control of the stability of shear deformation inside the slipping zone. Other mechanisms in relation with thermal decomposition of minerals affect the pore pressure and the temperature evolution of the system, and can play a significant role in the extreme strain localization observed in field. The actual width of the localized zone is a key parameter for understanding fault weakening mechanisms. On the basis of field observations, laboratory experiments and recent advanced modeling, these phenomena are analyzed and discussed in order to bring some new insights in the understanding of earthquakes nucleation.INTRODUCTIONIn the last thirty years, the study of earthquake mechanisms has emphasized the major role of rock friction. Earthquakes appear to be the result of a frictional instability and occur by sudden slippage along a pre-existing fault or a plate interface (Scholz, 1998; Sykes, 1978). The conceptual model of spring slider system is commonly used to represent the interaction between an elastic crustal block and a fault zone. Stick-slip instability is possible if the softening rate of the shear resistance of the fault zone is high enough as compared to the stiffness of the crustal block. Therefore, weakening mechanisms that can explain how the frictional resistance of a fault decreases with slip and/or slip rate is of prime importance to understand how an earthquake nucleates. In recent years, several drilling programs in active faults (e.g. the Nojima fault in Japan, Boullier, 2011; the Aigion Fault in Greece, Cornet et al. 2004, the Chelungpu fault in Taiwan, Ma et al. 2006, and the San Andreas fault in the U.S.A. Ellsworth et al. 2000) as well as high velocity friction experiments (e.g. Tanikawa et al 2012a; Tanikawa et al. 2012b) have highlighted the physico-chemical processes involved in the nucleation of seismic slip (see for the example the review paper of Niemeijer et al. 2012)."

Jan 1, 2015

"This document sets out the Exchange’s expectations and requirements for a valuation of mineral properties and outlines: the general purpose of valuation reports; guidelines respecting circumstances where the Exchange will require a valuation report; and valuation standards, guidelines and methods that are generally acceptable to the Exchange, 1. IntroductionThis Appendix sets out the Exchange's expectations and requirements for a valuation of mineral properties and outlines:(a) the general purpose of valuation reports;(b) guidelines respecting circumstances where the Exchange will require a valuation report; and(c) valuation standards, guidelines and methods that are generally acceptable to the Exchange.Mining industry standards and guidelines for valuations and valuation reports can be found in the Canadian Institute of Mining, Metallurgy and Petroleum Standards and Guidelines for Valuation of Mineral Properties (""CIMVal"") published in February, 2003 (www.cim.org). CIMVal consists of two parts, Standards and Guidelines. The Standards are mandatory and must be followed in order for a valuation to be CIMVal compliant. The Guidelines in CIMVal are not mandatory, but are strongly recommended.The Exchange requires that CIMVal Standards be used by Issuers and their professional advisors when preparing valuations and valuation reports on mineral properties. The CIMVal Guidelines should be followed by Issuers and their professional advisors in preparing valuation reports on mineral properties, with the exception that the valuation methods and guidelines under Section 4 Acceptable Valuation Methods and Guidelines below, must be followed."

Jan 1, 2003

By Bergh. L. C.

On line monitoring and diagnosis systems of process operating performance are becoming an important part of industrial programs, leading to improve process operation and therefore product quality over time. In processes, such as the contact section of a sulphuric acid plant, a large number of input variables, highly correlated, are presented. These characteristics usually pose more difficulties in modelling the process for monitoring and diagnosis purposes. Multivariate statistical projection methods, such as Main Component Analysis, have been proposed to effectively deal with these situations. The application of these ideas to a section of a 2350 MTD sulphuric acid plant, located at the Caletones Smelter, including dry tower, gas blowers, catalytic reactor and S03 absorber processes, is discussed here. A PCA model with eight main components is used for monitoring and diagnosis of more than seventy operating variables. Hottelling's T2 and Q residuals test were used for detecting measurement problems in relevant variables, and for identifying which set of variables were responsible for driving the process outside its normal operating region. Furthermore, considerable information for the correction of the tested operating problems was given by the use of these techniques.

Jan 1, 2007

By S. C. Ells

Introduction An investigation of the bituminous sands of Alberta was begun by the Mines Branch, Department of Mines, in 1913. This investigation was interrupted during the period 1916-19, but was resumed in 1920. Work completed in October 1924 has included detailed topographical surveys of extensive areas, examination and sampling of principal outcrops, the mining of trial shipments, laying of demonstration pavements, and a study of methods adapted to the recovery of hydrocarbons from the crude bituminous sand. Bituminous sand consists, for the most part, of clear quartz grains, cemented together by petroleum residuum or bitumen. In form the quartz grains are most irregular, varying from sharply angular to smooth, waterworn shapes. The bitumen has a specific gravity of 1.018 and has a penetration of 9.00 mm. (77° F. 100 grams 1 sec.). The percentage of bitumen associated with the sand varies from 5 to 25 per cent. A large tonnage is available in which the percentage of bitqmen is 15 per cent or over. Production Up to the present time, production has been restricted to requirements for experimental .and demonstration work. The total quantity shipped for such purposes has not exceeded 750 tons.

Jan 1, 1925

By Andrea Lisjak

The mechanical behaviour of Opalinus Clay, an indurated over-consolidated argillaceous rock, is heavily influenced by the presence of preferably oriented bedding planes. The objective of this study is to illustrate a new modeling approach aimed at capturing the bedding-induced anisotropy of Opalinus Clay as observed in the laboratory and in situ. The combined finite-discrete element method (FEM/DEM) is employed as the main simulation tool. FEM/DEM is a numerical method that models material damage processes by explicitly considering fracture nucleation and propagation. A transversely isotropic elastic constitutive law is used to account for different elastic property values in the direction parallel and perpendicular to the layering, while strength anisotropy is captured using a directional cohesive fracture model. Quantitative calibration and validation of the model is based on laboratory results of indirect tensile tests and uniaxial compression tests. Emergent strength and deformation properties, together with the simulated damage mechanisms, are shown to be in good agreement with experimental observations. Preliminary results relative to the analysis of a circular tunnel show that the approach is able to reproduce the main Excavation Damaged Zone (EDZ) formation mechanisms as observed in the field.

Jun 1, 2012

By D. O. DeGagné, J. F. Archibald

Spray-on polymer linings, as partial or full replacement for traditional forms of area rock support, have seen rapid growth in interest within Canada. A wide variety of lining types, ranging from polymer chemical to water-based cementitious materials, have been developed and commercially introduced to the underground mining market. Following approximately one decade of development work, several general conclusions have been reached regarding the performance of this class of area support media, these being that: health and safety assessment of the broad range of materials has shown the majority of them to be acceptable and safe for underground use; significant ground support potential can be offered by them, being equivalent to or better than capabilities offered by traditional support forms such as bolt-and-screen or shotcrete, and; their abilities to be rapidly deployed and provide near instantaneous support restraint offer considerable operational and cost benefits to underground operators. A review of currently available liner materials, their historic development within the Canadian mining industry, and overviews of support, health and safety, operational considerations and cost benefits are provided in this paper.

Jan 1, 2001

By Sergio Bustos

A significant expansion project is under way at KATCO?s Torkuduk In Situ Leaching (ISL) operation to increase uranium production up to about 4000 tU/year. Higher flows and lower uranium concentration are expected in the rich solutions coming from the well fields. Therefore, extra adsorption and elution columns and modified operating conditions are required to deal with the increased demand for uranium transfer from the ISL solutions to the eluate solution, which goes to the uranium precipitation section. Resin adsorption and elution performance have been interpreted and projected by using Mac Cabe-Thiele equilibrium diagrams. The resin load, the adsorption mass transfer coefficient, the adsorption zone height and the eluate concentration have been estimated for the expected changing operating conditions associated to the future mine plan. This information has allowed to improve the present operation results and to define the main process design criteria for the expansion project.

Aug 1, 2010

By Anton Sizo, Alexey Klyashtorin

The Gunnar uranium mine operated from 1953 to 1961 on the shore of Lake Athabasca, in 1964 the site was abandoned, and the mine pit flooded. In 1981, the pit was found to be stratified with a chemocline at ~70 m by a sharp change in conductivity and TDS. The uranium concentration was ~700 μg/l on the surface, 320 μg/l at 50 m, and 2,900 μg/l at 110 m. The Ra-226 concentrations were 0.1, 0.06, 0.12, and 0.4 Bq/l. By 2017, the chemocline was ~60 m deep. The highest uranium concentration was 1150 μg/l and the lowest concentration (220 μg/l) was attributed to the chemocline. In the deeper column, the uranium content varied around 750 μg/l. The uranium distribution down the pit profile was aligned with DO, ORP, and TDS. Ra-226 averaged to ~0.4 Bq/l, Ra-226 and uranium profiles were inversely related with the respective maximum and minimum attributed to the chemocline. The uranium and radium amount accumulated in the pit by 2017 was 3,420 kg and 2,163 GBq, respectively. The uranium and radium apparent accumulation trend estimates to 64 kg/y and 41 MBq/y, respectively. A stable chemocline and no concentration gradients in the other parts of the pit suggest that the contaminants are unlikely to inflow from the bottom opening or outside the pit, but rather are mobilized from the pit walls. The contaminants are not in a steady state, and concentrations of both uranium and radium are likely to increase slowly in the future if no remediation occurs.

Jan 1, 2020

By K. Waters, A. Navarra, T. Grammatikopoulos

Strategic decisions to develop a mineral deposit are subject to geological uncertainty, due to the sparsity of drill core samples. The selection of metallurgical equipment is especially critical, since it restricts the processing options that are available to different ore blocks, even as the nature of the deposit is still highly uncertain. Current approaches for long-term mine planning are successful at addressing geological uncertainty, but do not adequately represent alternate modes of operation for the mineral processing plant, nor do they provide sufficient guidance for developing processing options. Nonetheless, recent developments in stochastic optimization and computer data structures have resulted in a framework that can integrate operational modes into strategic mine planning algorithms. A logical next step is to incorporate geometallurgical models that relate mineralogical features to plant performance, as described in this paper.

Jan 1, 2017

By Jaeheon Lee

"Biooxidation of gold ores or concentrates could be a very attractive alternative to pressure oxidation (POX) or roasting to liberate the gold grains from various sulfides. Crushed heap bioleaching was successful in US and many operations using tank bioleaching of gold concentrate are currently running around the world. Many parameters need to be considered during the project of sulfidic refractory gold ore process. Capital and operation costs are among the most important ones. Run-of-mine heap biooxidation could be very inexpensive and the smaller the crush size (particle size), the more expensive the capital and operating costs for biooxidation application are expected. The capital cost of biooxidation could be a fraction of the cost for building POX plant or roaster and the operating cost could be 1/3 of POX or roasting depending on the method utilized. A new biooxidation process, Sand Farming, is introduced as an alternative to POX and tank biooxidation process. A relatively coarser particle size (P80 = 650 µm) of the process benefits the low cost of grinding against the conventional grinding size (P80 = 75 µm) for other options. The cost of Sand Farming is less than 40% of that of pressure oxidation with comparable gold recovery from the downstream process. This paper will review the laboratory scale testwork for various biooxidation process of sulfidic refractory gold ores and concentrates and provide the economic evaluation showing the biooxidation could be the most economic method without much sacrificing the overall gold recovery. INTRODUCTIONThe decreased availability and lower grade of raw materials has motivated industries to consider recovering values utilizing low cost process options. The process may treat high grade concentrates or submill grade ores that cannot be processed economically by conventional milling-flotation or leaching. Sulfidic refractory gold ores/concentrates have been economically processed by roasting, pressure oxidation, and biooxidation in stirred tank reactor. The process selection is based on a series of studies including multi-year long ore characterization and metallurgical investigations."

Jan 1, 2016

By B. F. Giyani, D. Rahal

"Stirred media mills have proved to be more energy-efficient than the conventional ball milling for fine grinding applications. The mill performance is governed by a number of operating variables including mill stirrer speed, feed particle size, solids content and slurry rheology. A study was conducted to assess effects of mill speed, media size and density, and slurry density on the Stress Intensity (SI) in a VXPmill and thereby the relationship to mill performance. For the mill speeds tested, it was found that the optimum tip speed is 7 m/s. If the speed is too high (12 m/s) energy losses result due to mechanical friction losses and heat generation. If the speed is too low (3 m/s), the kinetic energy is not sufficient to promote breakage. The size reduction ratio increases with the increase in mill speed and the decrease in solids content especially in the coarse fraction particle sizes. The effect of slurry rheology on mill performance was shown by assessing the effects of increasing solids concentration and decreasing particle size. Rheological effects seemed to interact with mill speed such that the mill was less energy-efficient at higher solids content and at higher mill speeds particularly for grinding to fine particle sizes. There is an opti"

Jan 1, 2017

By Schoeman L., K. C. Sole

Evaluation and measurement of the influence of changes in conditions and electrolyte composition during early stages of a growing metal electrodeposit are crucial to predict changes in developing morphology. A galvanodynamic polarization technique was developed to reliably measure overpotentials for nickel electrodeposition from sulfate electrolyte. The validity of these polarization parameters as indicators of the relationships between changes in the electrolyte and resulting deposit morphology was evaluated for electrolytes of varying composition. Findings indicate that nucleation and plating overpotentials measured by the described technique can be used as indicative tools for monitoring, evaluating and ultimately improving control of the electrodeposition of nickel from sulfate electrolytes. The results predict that nickel deposits of desirable quality and morphology are obtained when plating overpotentials are higher than 700 mV vs. Ag/AgCl and nucleation overpotential is less negative than plating overpotential.

Jan 1, 2017

By Jochen Franke, Matt Bird, Thoma Perkins, Malcolm Powell, Jason Robertson, Paul Toor

zThe operation of SAG mills is variable over time due to their continually changing liner shape, mass and subsequent load motion. However, this tends to be poorly accommodated in liner design and mill control, with only limited compensation made for this influence, usually in the first few weeks after a new liner is installed. With ever-increasing ore competency, increasing energy costs and decreasing ore grades, simplified design and operational approaches that compromise the achievable mill efficiency are no longer adequate. This paper presents a methodology that has been developed to measure and account for the changes in mill performance as the liner wears. This involves monitoring all liner profiles – in other words the three-dimensional liner shape - over the life of the liner, then conducting controlled surveys at different stages of the liner wear life, and correlating the mill performance to the liner profiles. The measured liner mass is modelled to provide an ongoing meaningful load mass measure that excludes the liner mass.

Jan 1, 2012

By Paul M. Lévesque

The Dome Mine has been in production for nearly 100 years and throughout the years many different mining methods were used to extract the ore. An exploration program late in the 1990s outlines new resources requiring the mine to extract the rock and some previously placed backfill (alluvial sand and/or classified tailings). It is therefore imperative to separate the backfill from the rock to reduce the negative impacts of handling the backfill on the ore pass, crushers and mill processes. Separating the backfill from the ore at the source would also reduce and/or eliminate the cost of handling this waste stream. The paper will touch on the backfill removal criteria, the risks, the alternatives and the selected method, screen decks, for backfill removal at the Dome Mine. The 155549 bulk zone case study will illustrate how the screen decks are in use at the mine. The paper will also illustrate how the lessons learned and conclusions of the work done for the 155549 bulk zone were applied to the second screen deck installation for the 257260 bulk zone.

May 1, 2009

By Saeid Akhavan

Accumulative roll bonding (ARB) is a severe plastic deformation process for achieving ultrafine grains in metallic sheets without changing the sample dimensions. In this study, ARB process was carried out on 5083 aluminum alloy sheets up to 6 cycles. In this process, the surfaces of the strips to be joined are roughened and cleaned and then stacked. After stacking, the specimen is roll-bonded by rolling using a 50% reduction. The rolled specimen is cut into two halves, and the above-mentioned procedure is repeated for several times. Microstructural characterizations were analyzed by transmition electron microscopy (TEM). Tension and Vickers hardness tests were performed on produced sheets for evaluating their mechanical properties. Moreover the texture parameter of the ARB-ed samples was calculated using their XRD patterns and the related equation. Additionally, the texture evolution during the ARB process was demonstrate by analyzing the measured pole figures and orientation distribution functions (ODF) and skeleton lines. The results indicated that at the early stages of ARB process, grains were subdivided by deformation induced boundaries. After several ARB cycles continuous recrystallization resulted in a microstructure covered with small recrystallized grains with an average diameter below 100 nm at the end of four cycle. Texture analysis revealed fiber textures have been discovered with continiuose of the ARB process cupper. Brass, S and dillamor textures identify which their differences are in intensity of ARB process. Results indicated conformity between mechanical evolutions and texture evolutions during ARB process.

Oct 1, 2011

By Saeid Akhavan

Accumulative roll bonding (ARB) is a severe plastic deformation process for achieving ultrafine grains in metallic sheets without changing the sample dimensions. In this study, ARB process was carried out on 5083 aluminum alloy sheets up to 6 cycles. In this process, the surfaces of the strips to be joined are roughened and cleaned and then stacked. After stacking, the specimen is roll-bonded by rolling using a 50% reduction. The rolled specimen is cut into two halves, and the above-mentioned procedure is repeated for several times. Microstructural characterizations were analyzed by transmition electron microscopy (TEM). Tension and Vickers hardness tests were performed on produced sheets for evaluating their mechanical properties. In order to clarify the failure mode, fracture surfaces after tensile tests were observed by scanning electron microscopy (SEM). The results indicated that at the early stages of ARB process, grains were subdivided by deformation induced boundaries. After several ARB cycles, lamellar structure elongated in the rolling direction contains lamellar boundaries was formed. With increasing the strain, mean spacing of lamellar boundaries decreased. Finally, continuous recrystallization resulted in a microstructure covered with small recrystallized grains with an average diameter below 100 nm at the end of four cycle. The tensile strength and hardness of the 6 cycle ARB processed 5083 aluminum alloy sheet increased about two and three times of the initial values, respectively. Results indicated conformity between mechanical evolutions and microstructural changes during ARB process. Fracture surfaces observations showed that failure mode in ARB processed aluminum is shear ductile rupture with elongated small dimples.

Oct 1, 2011