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By J. W. Smith, J. Van Dusen, A. Papachristodoulou

"As part of a study to evaluate factors affecting tankroom air quality, the mechanism of aerosol generation from bursting bubbles in electrowinning operations has been investigated. Typically 2 to 3 mg/m2.s are produced in zinc tankrooms. Analysis shows that the rate of production of film drops (geometric mean diameter - 2 urn] increases with decreasing bubble size, and that jet droplets (geometric mean diameter - 20 um) are not produced with gas bubble larger than - 4 mm. Both mechanisms of drop formation and current efficiency are affected by surface active agents, with an over-all reduction in emission of up to 60% to 70% being achievable. A source control system which does not adversely affect electrolyte properties is always preferred, and coalescence of all gas bubbles in to a continuous stream of gas at a single point on the electrolyte surface would eliminate aerosol emissions. This objective was the basis for design of a coalescence device which, in laboratory tests, reduced the emission rate by over 95%.The control device fit s over the electrodes in the electrowinning cell and is partially immersed in the electrolyte. A number of changes in the design which resulted in significant improvement in the performance of the device are reported.Field tests have shown that only about 75% of the aerosol below 10 um can be eliminated by coalescence. The remainder (up to 95% of the total) is controlled by coalescence of droplets, by impaction on the exposed collector surface and gravitational settling.The device does not interfere with operation of the tankroom, handles the effect of surges in power during harvesting, and is simple and inexpensive to maintain. IntroductionDuring the electrowinning of metals (such as zinc and copper) gases are evolved along the electrode surface forming small bubbles. The bubbles travel upwards and burst on the electrolyte free surface generating, in this way, small droplets. Because the electrolyte is often highly acidic or contains toxic materials, the whole process can result in the formation of an aerosol in the atmosphere above the electrowinning cells which poses a serious health hazard to workers in the area, and corrodes equipment."

Jan 1, 1988

By D. Q. Li

"This paper briefly introduces problems that can occur in the design of rare earth separation processes and that require close attention during engineering design. Important factors must be considered include the following. 1) The separation process is primarily based on two points. One is the raw material composition and the other is the product purity requirements. 2) Optimization of the rare earth separation process requires optimization of the flowsheet configuration and each process parameter. 3) The separation of heavy rare earths is performed under non-equilibrium conditions. 4) The radioactive elements uranium and thorium must be removed from the feed to separation. 5) Process economy and environmental protection must be considered together in the evaluation of any separation technology options. INTRODUCTIONThe importance of rare earth (RE) is well recognized in high-tech applications and sophisticated national defense technologies. RE is the treasure house of the 21st Century new materials. The RE separation processes developed using HEHEHP (P507), P507-alcohol (ROH) and naphthenic acid (NA) have been widely applied in China. These processes have led to industrial production of all of the individual RE with up to 4N (99.99%) or higher purity (Li, Wan, Lin, Xie, Lin, & Wang, 1980; Li, Wang, & Xie, 1985; Li, 1995; Li, Wang, Meng, & Li, 2005). In order to achieve the best economic and environmental benefits, this paper discusses several problems to which attention must be paid in the design of rare earth separation process."

Jan 1, 2016

By J. P. Thomson

Magnesium alloys are steadily improving their market share as structural components especially in the transportation sector. Therefore, there is a great deal of interest from the automotive and the metal casting industry to develop viable economic casting processes for magnesium-base alloys. This paper summarizes the preliminary results on the continuing projects within CANMET-MTL on casting processes such as gravity and low-pressure casting in sand molds, permanent molds and lost foam.

Jan 1, 2004

By Robert A. Brown

"The O'Brien mine is in the west-central part of Cadillac township along the Cadillac 'break', which extends for 7,500 feet from west to east across the property.The ground was staked in 1924 by A. Dumont and W. Hermeston, prospecting for M. J. O'Brien, Limited. The first vein discovered is that now known as No. 1. The No. 4 vein was later exposed on the surface; the other veins known to be present were revealed by underground work and diamond drilling carried out both from the surface and underground.The mine is developed from three vertical shafts: No .. 2 extending from the surface to 2,000 feet; No. 3 from the surface to 1,500 feet; and No. 4 from 2,000 to 3,000 feet. There is on the property a mill of about 200 tons a day capacity, the usual shops, and a townsite housing about forty-five families. Gold production to the end of September, 1944, amounted to 295,824 fine oz. from ore having an average grade of 0.505 oz. a ton. In addition, the mill recovered 3,237 tons of arsenic trioxide having a purity of 83 per cent As2O3.GENERAL GEOLOGYThe four main groups of rocks of the Cadillac area- the Cadillac, Blake River, Kewagama or Pontiac, and Malartic- are found within the boundaries of the property. However, as these rocks have been fully described in · various government reports (1,2,3,4,5,6) and all the known orebodies occur within one group- the Blake River-a detailed description of the geology will be dispensed with here. The known ore deposits lie south of the Cadillac 'break' in a group of rocks that includes 'greenstones', greywackes, conglomerate, porphyries, and a rock of gabbroic composition that may be intrusive. Both flows and tuffs can be recognized in the 'greenstones'. The two bands of porphyry that trend easterly across most of the property have been considered by some observers to be dyke rocks and by others to be flows. Certain evidence points to their being dykes that were intruded as sills considerably prior to the emplacement of the gold-bearing veins, but the possibility of flow origin cannot be fully rejected. North of the talc-chlorite-carbonate schist zone forming the 'break' the rocks are conglomerate and greywacke with iron formation, in which there are no known veins of ore grade. Within the schist zone are minor acid and basic intrusives. The general trend of both bedding and schistosity is a few degrees south of east. The dip is generally vertica1 or steep to the south."

Jan 1, 1954

By W. Swidzinski

"Zelazny Most" post-flotation copper mine tailings pond is the only place to of storeing wastes for KGHM POLSKA MI EDZ S.A. The flotation tailings is are the main waste stream in copper mining in Poland. Sufficient storage capacity for tailings is crucial for , thus uninterrupted production of copper is crucially related to the possibility of storing wastes in the pond. The pond covers a Its over 14 km2 arca, almost 50 m high dams making this dame this construction one of the largest in the world. The risk assessment of potential damage due to un stable ility loss of dams or environmental contamination, as well as safely constructing damsincrease of dams within the design criteriaprocess, require quick access to a large amount of the monitoring data , which in vast amount have to be monitored, that needs to be analyzed and processed and reported, every day. This In the paper describes the numerical information system "SyZeM" , used for designated to the "Zelazny Most" pond, baseding on the Oracle database and Geographical Information System , to manage the graphical and descriptive data in coherent way., is presented. The main structure of the system, as well as the methodology of storing, processing and reporting the geological, geotechnical, hydrogeological, geophysical, chemical and survey data are shown. The aspects of Optimizing optimal and risk mitigation and safe management of copper wastes and risk mitigation with the help of "SyZeM" are discussed.

Jan 1, 2007

By Robert B. Parsons

"It is quite likely that more than a handful of junior exploration companies will receive some startling news from their accountants this spring when 1989s tax returns are being prepared. These companies could find that, for the first time ever, they will have to write a cheque to the federal government on account of a new federal capital tax which became effective July I, 1989IntroductionMany mining companies which have never had to pay a federal income tax are finding that they indeed have a tax liability for 1989. Non-producing companies, such as junior exploration companies, almost automatically assume that they don't have to pay any income tax. But, a new tax imposed under the Income Tax Act catches especially the company that has no income.Effective July 1, 1989, a federal capital tax (some call it a corporation minimum tax) is payable by any corporate carrying on business in Canada where the corporation has ""taxable capital"" exceeding $10 million. As a result of the popular use of flow-through shares in recent years, many junior exploration companies are finding that their balance sheets show capital stock over $10 million, and that they are consequently caught by the new tax. Further, some of these companies are finding, to their chagrin, that the tax for 1989 was due on February 28, 1990, and that non-deductible interest is ticking away on unpaid taxes."

Jan 1, 1990

By V. V. Zubkov

The systems of geophysical monitoring have been already put into operation at coal mines and ore mines. Since at present it is rather difficult to conduct mine experiments; it is necessary to start a new step in joining of geomechanics and seismic. The linking geomechanical and geophysical monitoring at coal mines and ore mines today became possible due to progress in development of numerical methods of modeling of stress state and technology for processing of seismic information. This paper describes one potential step in linking geomechanical and seismic monitoring at coal mines and ore mines.

Aug 1, 2013

By P. Hale

"The trend to drives of more than 10,000 hp on large-capacity ball and autogenous mills for increased operating efficiency has been limited by factors in the conventional drive system. A solution to this problem, using modern developments in static converter technology, is the concept of driving the mill directly without gearing using a low-speed, low-frequency synchronous motor with a cyclo-converter power supply.This paper presents various practical arrangements of mill and low-speed motors giving the specific advantages of each system. The means of controlling inrush currents on starting and of spotting by the use of variable-frequency control are outlined in general form. Several gearless ball mill drives are scheduled for start-up in European cement plants and further orders have been placed."

Jan 1, 1970

By A. Gakwaya, K. Ba, M. Guillot, J. Levesque

"In the aerospace industry, parts requiring tight dimensional tolerances and high mechanical properties are often produced by forging. This forming process allows for an optimal use of the material and can produce high quality parts at a reasonable cost. Thanks to CAD techniques, it is now easier to predict flow profiles and in-process defects occurrence as well as wear of the forging dies. However, in order to determine the properties of the forged part with computer simulation methods, a good material constitutive law is a prerequisite. This paper presents a virtual manufacturing process modeling for the closed die forging of a workpiece performed with Abaqus. The hot closed die forging is a regular process applied to manufacture metallic components used in aerospace industry. In this forming process, the material flow and final properties depend on the microstructure evolution during the process that is why it is important to include the microstructure effects in the material model. Based on the stress-strain data measured experimentally, the material parameters of the standard (classical) Johnson-Cook constitutive model and of a modified Johnson-Cook constitutive law including the microstructure effects have been determined. The obtained simulation results are compared with the experimental results for validation.INTRODUCTIONDue to their good physical and mechanical properties such as ductility, fatigue strength, corrosion resistance and rupture, aluminium alloys are often used in the aeronautic and the automobile industries. In this work, we present the forging of an Al-Zn-Mg-Cu alloy, a high strength aerospace alloy recognized for his good combination of physical and mechanical properties. The forging process is simulated in Abaqus Explicit using both the standard Johnson-Cook law (Johnson & Cook, 1983; Hor, 2011; Lin et al., 2012), and its modified version as proposed by Andrade et al., (1994). The Johnson-Cook law offers the advantage of considering the coupled effect of the plastic strain, the plastic strain rate, the temperature of forging and the hardening effect. However, it is a phenomenological model which does not account for the effect of the microstructure evolution. In this work, a modified Johnson-Cook model implemented in a user subroutine is used. It includes the effect of the dynamic recrystallization phenomenon during the hot deformation. The dynamic recrystallization has a noticeable influence on the microstructure and on the properties of the material. The term dynamic means that the process starts and acts during the deformation and this is different from the static mechanism of recrystallization which occurs during an annealing and after cold or hot deformation. Since properties of the alloy used in this work are not readily available in the literature then characterization tests have been done at various temperatures and strain rates, in order to determine the thermomechanical properties and the material behavior during the process of hot forming, more precisely during the hot forging process."

Jan 1, 2016

By James R. Hunter, Sandra K. Zacharias, Ursula M. Franklin

Archaeometallurgical remains can be a valuable source of information about past technological activities and, by inference, the societies that undertook them. Material traces of former metal-producing or metal-working centres can include raw materials, products, or metallurgical installations such as mines, furnaces or forges. Of these remains, the most common is slag, often left undisturbed since its original production. Physical and chemical analyses of archaeological slag and metal can often reveal the processes and materials involved in their formation. Mineral composition and softening temperature of a slag, for instance, can indicate the conditions of the metallurgical operation, such as temperature and atmosphere and, thus, help identify metallurgical processes which took place at a site(1). The present report illustrates the value of such analysis. Metal-working remains from Sainte-Marie among the Hurons, near Midland, Ontario, on the south side of Georgian Bay have been analyzed in order to determine the techniques and processes used by the 17th-century blacksmith who worked at the mission headquarters from 1642 to 1649. Samples were selected from a very large collection of blacksmith refuse which was excavated from the site by archaeologist Kenneth Kidd in 1941-42(2).

Jan 1, 1999

By J. B. Hamilton

The advantages of generating and distributing electrical energy direct from the coal-fields so closely affects the mining industry that a few remarks on the unbalanced phases of coal distribution is worthy of attention. The value of coal imported into Canada from 1912 to 1921 exceeded the sum of $580,000,000. In 1922 Ontario imported 1,640,000 tons of anthracite and 9,440,000 tons of bituminous coal. I submit that the use of Saskatchewan lignite in an electrical super-power plant equipped for the carbonizing of coal, and disposal of excess gases would be the commencement of a solution of the fuel shortage in Ontario. As Saskatchewan becomes more and more populated and manufacturing increases, the amount of by-product carbonized fuel available for shipment to Ontario will increase, and its shipment to that province would decrease the trade deficit of the national balance sheet. If and when this is carried out it will mean a better and wider market for Alberta fuels in Saskatchewan and Manitoba.

Jan 1, 1924

By M. Nzotta, L. Teng, S. Seetharaman, A. Chychko

The objective of the present work is to optimize the EAF practice towards Mo alloying with maximum retention of the alloying element in molten steel. During Mo additions, there were significant losses to the dust (ca 7 %) and to the slag phase (ca 2 %), which had serious economic and environmental impacts. The present work was aimed at designing a suitable Mo precursor, an alternative to ferromolybdenum, as the Mo source and a process sequence for optimal retention of Mo in the steel. The design of the Mo source should be in such a way that low cost raw materials such as MoO3 concentrate have to be used, stable during the addition so that the vapour phase losses as MoO3 are kept minimum and the dissolution of the precursor in molten steel is easy without loss to the slag phase. After thermodynamic considerations, three precursor materials were chosen, viz. CaMoO4, MgMoO4 and Fe2MoO4. Synthetic mixtures of the component oxides in each case as well as pure MoO3 were investigated by TGA and high temperature XRD in order to find out the temperature range in which the compounds were formed. Experiments were also conducted separately where the evolved gases were analyzed. All the three precursors were formed easily and the loss of MoO3 to the vapour phase was found to be extremely low. Addition of the oxide mixtures to steel melts were conducted in three different scales, viz. 16 g, 500 g and 3 tons (induction furnacle). Initial experiments showed that MgMoO4 was not suitable since the Mo yield in the steel melt was not very high. Fe2MoO4 was found to perform best, the Mo yield reaching 98 %. Further trials were conducted in the 65 ton Electric Arc Furnace (EAF) at Uddeholms AB in Hagfors. Mixtures of mill scale, MoO3 and carbon in suitable proportions were added in a pre-determined addition sequence. It was found that, in the actual practice, the Mo yield reached 99 %, equaling in performance the addition of ferromolybdenum. The process offers an effective use of cheaper raw materials and very high Mo yield avoiding a pre-treatment step like the production of ferromolybdenum. This is both cost effective and environmentally advantageous. The process has been patented and is being currently implemented at Uddeholms AB, Hagfors, Sweden.

Jan 1, 2011

By A. Christoffersson, T. Nillson-Wullf, H. R. Manouchehri

"Mining industry has been the building blocks for human development through millennia and will continue to play its role in sustainability and meeting society’s needs for raw material. In the way towards sustainability, the next generation of efficient and heavy duty of Sandvik’s crushers, CH860 and CH865, are introduced for efficient crushing. As the secondary, tertiary and/or pebble crusher, these new crushers are designed to over perform in tough mining environment. Featuring higher crushing forces relative to the mantel diameter and 500 kW motor, combined with advanced automation system, i.e., sophisticated HydrosetTM and Automated Setting Regulation (ASRTM), combined with overpressure system with dedicated air supply in dust collar, etc., the new crushers provide higher safety, productivity, and reliability with the same foot-print of conventional cone crushers.Since crushers are more energy efficient than mills it makes sense to effort in fine crushing to save energy and protect environment. That has been the logic behind development and introducing stronger and more efficient crushers by Sandvik. The results on crushing hard iron and gold ores by CH865 have proven its efficiency in fine crushing at a higher productivity, availability and reliability rates through increasing throughput for defined size fraction and extended crushing chamber liner life.Within this paper the performance of the CH865 to deal with two different ores are presented discussed with a glance at how the downstream milling process can be benefited by saving energy and reducing the operation cost. In plant practice, the implementation of the new CH865 provides between 25 and 30% of the crushed ore in the size range of first step milling, i.e., < 2 mm, that offers opportunity for reduction in energy consumption in milling and even changing the process plant configuration by directly forwarded that part to gravity separation. Furthermore, potential of converting the rod mill to ball mill to improve productivity has been considered by plant engineers. Furthermore, some potential applications for such efficient crushers are brought into considerations and discussed. The new developments provide about 30% higher crushing force to efficiently deal with competent ores and pebbles. The CH860 and CH865 crushers are well suited to replace conventional secondary and tertiary crushers respectively; nevertheless, CH865 is virtual option for pebble crushing in SAG and AG milling circuits."

Jan 1, 2016

By K. Himbeault, D. Campbell, N. C. Garisto, D. A. Orava, A. Rosaasen

"The level of scientific knowledge about the effects of contaminants is increasing and changes in environmental monitoring are likely to allow for the assessment of environment effects particularly to the aquatic environment. This paper provides an overview of recent developments in this area which include the environmental effects monitoring program for pulp and paper operations, the assessment of the Aquatic Effects of Mining (AQUAMIN) program, the Aquatic Effects Technology Evaluation (AETE) program, and the review of the federal Metal Mining Liquid Effluent Regulations (MMLER). The paper also provides a look forward at the direction of environmental monitoring of mine projects in Canada. IntroductionEnvironmental monitoring programs provide a wide range of data to environmental management systems, regulatory authorities, and stakeholders. The data obtained are used to demonstrate that operations are in compliance with regulatory environmental protection requirements, and provide the scientific basis for assessing the effectiveness of environmental protection measures. Environmental monitoring requirements for mine projects are established based on the type of operation, site specific issues and concerns, and the requirements of regulators and mine proponents.The level of scientific knowledge regarding the potential effects of contaminants on the receiving environment is increasing, and in particular with regards to the receiving aquatic environment. Regulatory controls regarding the protection of fish, fish habitat, and fishery resources are being reviewed with regards to their adequacy, and the environmental effects monitoring program on the pulp and paper industry is expected to provide useful data relevant to those types of operations. These developments are of interest to mine proponents as it is presently expected that an environment effects monitoring program will be developed specifically for the metal mining industry under a regulated environmental effects monitoring program as part of the Fisheries Act. This paper reviews recent developments in this area, and provides a look forward on the future directions of environmental monitoring programs."

Jan 1, 2000

By Diego L. Romero, Joy P. Romero

"IntroductionThe purpose of this paper is to explain the theory and demonstrate the industrial applications of electrostatic separation. Wabush Mines' use of this type of processing for the concentration of iron ore is unique in the industry. Other minerals are concentrated electrostatically but the process is not widely used.Typical minerals separated by electrostatic separation techniques are:Non-ConductorsAnhydriteApatiteBariteBastnasiteBerylCalciteChrysotileCorundumDiamondEpidoteFeldsparsFluoriteGarnetGypsumHornblendeKyaniteAcmiteAugiteBrookiteCassiteriteChalcopyriteChromiteColumbiteCopperDaviditeEuxeniteFerberiteFrankliniteGalenaGoldGraphiteHematiteMica (Biotite)Mica (Muscovite)MonaziteOlivinePerovskiteQuartzScheeliteSideriteSillimaniteSpheneStauroliteSulphurTopazTourmalineXenotimeZirconConductorsIlmeniteIlmenite-( High Iron)IlvaiteKoppiteMagnetiteMarmatiteMolybdenitePyriteRutileSamarskiteSphaleriteTantaliteWolframiteWulfeniteThe limitations of this process are:1. There must be a difference in conductivity between the minerals being separated.2. The size range must not be very wide.3. The specific gravity of minerals being separated should be similar or the minerals to be pinned should be lighter. 4. The feed must be dry.5. The particle shape should be more or less uniform. 6. The feed must not be high in true middling particles."

Jan 1, 1989

By Angeles Mendoza Sammet

Based on the analysis of issues associated to conflicts between communities and mining companies in Mexico, this paper suggests actions to make mining more sustainable in Mexico. Interviews with key informants and a revision of documental information available on the internet provided information on 15 cases of conflicts in various parts of the country. The issues varied from incompliance with environmental law to assassination of community members opposing mining. The analysis concludes that mining is not sustainable in Mexico. Both mining companies and the Government of Mexico can make changes to improve sustainability. Mining companies could take a proactive approach and engage in consultation with communities before starting operations. Sharing information with communities on environmental management programs and monitoring results can be a way to start building trust and demonstrate environmental commitments. Companies can implement and evaluate CSR policies to ensure that all staff and contractors are trained on them to reduce and/or prevent corruption and violations of human and indigenous rights. Only 3 of the 15 companies had clear social responsibility policies or sustainability targets, but no reports evaluating them. Complying with the law does not make a project sustainable because of corruption, deficient enforcement, and gaps in legislation. The Government of Mexico should address the following points to make mining more consistent with sustainable development. Update the mining legislation to introduce sustainable development principles and consultation. Incorporate the notion of Free, Prior, Informed Consent (FPIC) for Indigenous People (IP) on all applicable Mexican laws or regulations. The government should not grant concessions on protected areas or indigenous lands without extensive meaningful consultation with the public, IP and land owners. Finally, it is vital to increase SEMARNAT?s capacity to review impact assessment reports and inspect and monitor environmental compliance along the life cycle of projects.

Aug 1, 2013

By H. Ikeman

"The highly specialized communication systems used in the mining industry place exacting demands on equipment and transmission media. Safely and reliability of services are perhaps the two most important factors. Fibre optics is ideally suited 10 meet these stringent requirements. Aside from being an intrinsically safe, non-sparking and EMI/RFI immune medium , fibre optics offers greater reliability , higher quality of services and superior flexibility over conventional copper or radio-based communication systems.This paper wilt show how fibre optics can be applied in mining industry applications. Emerging trends and concepts will be presented to show how fibre-optic-based integrated service communication networks and local distribution systems can be implemented.IntroductionCommunication requirements in today&apos;s mine s are varied and extensive. The communication system must be rugged , safe and reliable, yet provide an ever increasing amount of high quality services. Presently, these systems are implemented using conventional copper cable. As mining method s and technology advance and the demand for better and more communication services increases, traditional systems quickly reach their limitations. It is under these circumstances that we turn to fibre optic communication systems.Fibre optics is a mature technology which is finding its way into more and more applications worldwide. A fibre optic communication system can provide a level of performance unattainable by conventional cable systems yet ca n be cost competitive. As is well known, fibre optics provides a noise-free, noise-immune, high -capacity communications channel. Glass fibre, being dielectric and non-sparking, is an intrinsically safe communications medium. Clearly, it is ideally suited to the harsh environment present in a mine.From a communication systems point-of-view, the topology of a deep mine is unique. The objective of the systems engineer is to implement a total communications capability throughout this wide spread area. Ideally all classes of services should be accessible throughout the network-an integrated network concept. Recent advances in communications technology combined with fibre optics make this realizable."

Jan 1, 1984

By A. Hekmat-Ardakan

Conventional hypereutectic Al-Si alloys such as A390 are used principally for the casting of components used in wear applications requiring abrasive resistance such as in engine or compressor blocks. A comprehensive study was undertaken to investigate the potential of improving the mechanical properties of these alloys by the addition of magnesium. A thorough thermodynamic study of the effect of the addition of Mg to the conventional A390 alloy showed that Mg2Si starts to form as a primary phase at 4.2% Mg as well as in the products of the binary and ternary eutectic reactions forming the matrix. Experiments were carried out in producing castings with different cooling and solidification rates of alloys with up to 10% Mg. Mg additions were found to increase the hardness over the as cast alloy due to solid solution strengthening. Also, T6 heat treatment greatly improved the tensile properties of these alloy compositions due to the strengthening effect of the theta-Al2Cu phase. The elongation of these alloys generally decreases marginally with Mg content. The most significant property improvement of the alloys with higher Mg content is the substantial increase in wear resistance. This is attributed to the dispersion of smaller particles of Mg2Si and their coherence with the matrix as compared to the large Si particles in the conventional alloy. A new rheoforming process for A390 is presented that improves the processing of the semi-solid slurry. Structure modification elements were also added to refine the primary and eutectic silicon greatly improving the processing of the semi-solid slurry.

Jan 1, 2011

By Jian Deng

Rockbursts are sudden and violent failure of rocks in deep and/or high stress mines, which may destroy the excavation space and cause an accident or even the death of mining workers. This study is motivated by the pervasiveness of rockbursts all round the world. It has been found that rockbursts are often stimulated by dynamic fluctuation which is generated by mining operations or other sources of vibrations, such as blasting in adjacent stopes. This paper attempts to investigate the dynamically stimulating mechanism of pillar rockbursts in hard rock mines from an innovative point of view. Rockbursts are classified into triggered rockbursts and induced rockbursts in accordance with the magnitude of the stimulation force. Triggered rockbursts occur only when a small fraction of stress changes associated with rockbursts is accounted for by the causative excavation, whereas induced rockbursts happen where the causative factor is responsible for most of the stress changes required to produce the rockburst. By considering rockbursts as a dynamic instability problem of structures, rigorous mathematical models are set up for triggered rockbursts and induced rockbursts, respectively. By using the method of averaging and the method of eigenvalue problems, the boundaries of rockburst occurrence of a pillar are obtained for these two rockbursts. A new explanation of the failure mode of fretting or necking of pillars is given, the perturbation effect for pillar rockbursts is found, and the parametric resonance mechanism of pillar rockbursts is revealed. The quantitative relation between blasting parameters and pillar rockbursts obtained can be directly used to control the rockbursts. Contrary to conventional methods where only rock materials or rock specimen were used to study rockbursts, this investigation attaches more attention on the structural effect on rockbursts, which have strong potential applications in deep mining.

Jan 1, 2015

By A. Mykytiuk, I. E. Puddington, W. D. Macleod, F. W. Meadus

"A laboratory-scale continuous procedure for the up-grading of naturally occurring tin ores, based on the principle of spherical agglomeration, is described. High recoveries are indicated. A proposed second stage suggests useful fractionation steps.IntroductionA LABORATORY-SCALE batch process for the upgrading of a tin ore using the principles of spherical agglomeration has already been described (1). This procedure consisted of milling, for about an hour, a precrushed ore with at least 200 per cent water, 0.2 per cent of a reagent such as tall oil (to render the de-sired ore particles hydrophobic) and about 3 per cent of a viscous petroleum oil. The feed material passed an 8-mesh Tyler sieve, and the percentages of re-agents are based on the dry weight of the feed. Du-ring the grinding, the hydrophobic particles transfer into the oil phase to produce coherent semi-solid bodies while the gangue stays preferentially in the aqueous phase. The concentrate can be separated from the gangue easily by a mechanical operation. Using an ore containing about 0.3 -0.5 per cent tin, grades of from 1.5 to 7.0 per cent were obtained by varying the pH of the system. Recoveries fell from about 80 per cent to as low as 50 per cent as the grade in-creased."

Jan 1, 1966