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By M. Dupuis

It has been previously demonstrated [1,2] that using selective collector bar rodding has a big impact on the uniformity of the current density at the top surface of the cathode block and hence on the intensity of the horizontal current in the metal pad, The present study investigates the impact of using selective collector bar rodding on the MHD stability of a 500 kA aluminium electrolysis cell, For this purpose the recently developed MHD package for the aluminium reduction cell time dependent behavior is used.

Jan 1, 2005

By P. Chollet, A Constant

THE RESULTS of a previous investigation ( 1) on the work-softening of some heat-treated steels have led to the conclusion that the occurrence and intensity of the phenomenon is possibly governed by the work-hardening capacity of the material, and the relative amount of retained austenite. The first assumption is compatible with Polakowski's theory (2) that the absence of work-softening, in steels quenched and tempered at relatively low temperatures, may be attributed to the high rate of work-hardening which compensates for, and even out-weighs, the loss of internal energy associated with the simultaneous rearrangement of the original system of internal stresses. Indeed, Polakowski first considered the work-softening as a manifestation of a partial release (by cold-working) of the latent strain energy stored in

Jan 1, 1962

By B. Calver, D. J. M. Farnsworth

"As open-pit operations expanded at Pine Point, hydraulic aquifer evaluation was undertaken to establish the criteria necessary for the design of a feasible dewatering system.The extreme climate of this northern location dictated that the ore zone under extraction be rendered as dry as possible to minimize freezing effects. The design and implementation of such a system necessitated detailed hydraulic evaluation, and the problems that occurred are typical of those inherent in open-pit mining operations in northern areas.The paper describes the problem solution as approached from a mine engineering point of view, with particular reference to the practical aspects of operation and installation. The hydrological analysis used is simple and readily applicable to most open-pit dewatering problems."

Jan 1, 1969

By P. Venkatasubramanian

"In recent years, computer based ""expert systems"" have been taking on large complex tasks for which no exact algorithmic solutions are feasible; tasks previously reserved for human experts requiring empirical knowledge, judgment, experience, developing a ""best solution "" by the use of plausible reasoning. Mining method selection is an appropriate area for the application of an expert system because extensive and detailed knowledge is required to make a ""best"" interpretaion of frequently ambiguous geological information. The expert system model presented here would enable users to apply expert knowledge to the evaluation of methods for coal deposits mineable by underground methods. IntroductionIn an increasingly complex and specialized world, human expertise spanning scientific, economic, social and political issues plays an increasingly important role in all branches of engineering. This is especially true of mining engineering. The number of scientific and professional disciplines involved in mine planning and evaluation, illustrates the problem. A conservative list includes geology, geophysics, geotechnics, hydrology, mining, environment, and economics.Engineers are almost obliged to be experts in at least one of the above disciplines if they are to handle the volume of information required in the planning process. Although computers have become indispensable tools in many endeavours, there is continued reliance on the human expert's ability to identify and synthesize these diverse factors, to form judgments, evaluate alternatives , and make decisions . This is especially true with regard to problems that are not easily amenable to precise formulations.The precious resource of human expert is also fragile and transient. The departure of a crucial expert from an organization ma y cause serious dislocations. Senior experienced people impart their knowledge of younger colleagues, but the demand for their talent may not leave sufficient time for such educational efforts. In recent years, computer based "" expert systems"" have been taking on large complex tasks for which no exact algorithmic solutions are feasible; tasks previously reserved for human experts, requiring empirical knowledge, judgment , experience, developing a ""best solution"" by the use of plausible reasoning."

Jan 1, 1988

By Carlos Alberto Spier

The Águas Claras and Pico mines are two world-class, iron-ore mines hosted within Lower- Proterozoic banded iron-formations (locally known as itabirites) of the Minas Supergroup located in the Quadrilátero Ferrífero District, Minas Gerais, Brazil. The Águas Claras orebody consists of a 2,500 m long roughly tabular-shaped lens hosted within the dolomitic itabirite of the Cauê Formation. Dolomitic itabirite is the protore of the soft high-grade iron ore, which is the main ore type of the Águas Claras orebody, and represents more than 85% of the 284 Mt mined since 1973. Hematite is the main constituent of the iron ores. It occurs as martite, granular hematite and, locally, as specularite. Magnetite appears subordinately as relicts within martite and hematite crystals. Gangue minerals are very rare. These consist of dolomite, chlorite, talc and apatite and are especially common close to the contact with the protore. This virtual absence of gangue minerals is reflected in the chemistry of ores which are characterized by very high Fe contents (an average of 68.2% Fe). The Pico orebody is a continuous ~3,000 m long body of lenticular shape hosted within quartz itabirite, which is the protore of the soft high- and low-grade ores at the Pico mine. The soft high-grade ores, together with the low-grade ores, called iron-rich itabirite, are the main types of ores at the Pico mine, respectively representing approximately 51 % and 29 % of the reserves within the pit. The iron oxide mineralogy is the same as that of the Águas Claras mine, but in different proportions. Gangue minerals are very rare in the high-grade ores, but are slightly more common in the iron-rich itabirite. Quartz is the dominant gangue mineral, and is found with minor quantities of chlorite. The chemistry of the high-grade ores is characterized by high Fe contents (an average of 67.0 %) and low P, Al2O3, and SiO2 which are concentrated in the fines. Iron rich itabirites average 58.6% Fe and 13.5% SiO2.

May 1, 2003

By F. Guo

"The leaching kinetics of zinc sulphide concentrate was studied under total pressures ranging from 0.3 MPa to 0.5 MPa and leaching temperatures ranging from 358 K to 378 K. The apparent activation energy of leaching reaction under different total pressures was calculated. The results show that for the extraction of zinc at low-temperature pressure leaching is controlled by an interfacial chemical reaction. This was supported mineralogical analysis of the leaching residue. The kinetic equation for low-temperature pressure leaching of zinc sulphide concentrate was further established by quadratic regression on the basis of shrinking core model.INTRODUCTIONThe Roast-Leach-Electrowinning Process (RLE) is the primary route for zinc production and responsible for more than 85% of the total zinc production (Souza et al., 2007). During the roasting of zinc concentrates, fugitive SO2 causes pollution. The prevention of SO2 emissions from the RLE process can be one of the challenges to this technology (Deller, 2005). In the 1980s, the Zinc Pressure Leach (ZPL) process changed the concept of zinc hydrometallurgy, in which zinc sulphide concentrate is directly leached at approximately 423 K and approximately 0.7 MPa oxygen overpressure and the sulphidic sulphur is oxidized into elemental sulphur so that the pollution by SO2 is completely avoided. Since 1981, five zinc plants have adopted the ZPL process either for expansion by integration with existing roasting facilities, or for the production of zinc without any roasting at all (Collins et al. 1994; Barth et al. 1998). The innovation of the ZPL process has made the zinc industries more competitive although it needs an autoclave. The direct leaching technology of zinc is still in development."

Jan 1, 2012

By S. Yue, P. Vo, M. Jahazi

The flow behaviour and microstructure development of a near-alpha titanium alloy during beta working has been investigated. Typical cogging conditions were simulated through compression testing of IMI834 at temperatures of 1025°C-1100°C, strain rates of 0.01 s-1 - 1 s-1 and post-deformation heat treatments up to 4h. Using a synthesis of available literature models, a finite element model has been developed and validated through quantitative measures of flow stress-strain data and beta grain characteristics. Flow behaviour was analyzed through a self-consistent method while the microstructure development was considered with regard to the kinetics of beta recrystallization. Deformation at beta or high alpha/beta working temperatures (T>l025°C) produced minor flow softening with complete grain refinement achieved through metadynamic recrystallization.

Jan 1, 2006

By S. Kelebek, B. Nanthakumar

ABSTRACT The sensitivity of sulphide minerals towards oxidation depends on the mineralogical makeup and nature of sulphide ores. This paper focuses on chalcopyrite behaviour in a nickel-copper sulphide- ore matrix that was aged in the mine-site stockpiles. Results of collectorless, collector-induced flotation and recovery by size are presented following a discussion of XPS analysis that was used to gain insight into oxidative alteration of chalcopyrite’s surface chemistry. Chalcopyrite maintains its high flotation activity despite exposure to weeks of oxidative conditions. It is concluded that chalcopyrite is quite tolerant to stockpile oxidation due to various factors related to alteration of its surface chemistry.

Jan 1, 2012

By Charlie Harper

Open Pit Mining of Golden Band Resources? EP Gold Deposit Golden Band Resources Inc. (GBN:TSX-V) is Saskatchewan's newest Gold Producer. Located in the La Ronge Gold Belt of northern Saskatchewan, GBN has over 875 km2 of claims with 12 known gold deposits and 4 former producing mines. Production has begun at the Roy Lloyd Mine (Bingo Deposit), to be followed initially by our EP and Komis properties. Development of the underground infrastructure at the Roy Lloyd Mineis continuing and on schedule. Production from these deposits will feed our centrally located and 100% owned Jolu mill. We have our provincial environmental permits in place, and we have an established infrastructure including a 400 tonne-per-day mill, year-round road access, and access to grid power. Construction of the grid power line and the above ground tailings facility are now complete.

Nov 1, 2011

By M. W. Grabinsky, J. H. Curran

"Characterizing the spatial distribution of rock stresses is a challenge, especially in the geologically complex environments typically found at most metalliferous mines. Therefore, instead of focusing, specifically, on the task of making stress measurements, the engineer should instead attempt to develop a better understanding of the interaction between stress, mining geometry and rock mass behaviour. This paper demonstrates such an approach using a Canadian Shield hardrock mine case study, in which geomechanical models are used to relate stress, mining geometry, and rock mass properties to observed excavation response, and numerical modelling is used to better quantify this interaction.IntroductionUnderstanding how the mine geometry, field stresses and rock mass interact to produce the observed rock mass response to mining can be a significant challenge. Consider our present ability to quantify the basic geomechanical design input data. Mine geometry is normally quantified in more detail than is required for analysis purposes. Our understanding of rock mass strength and stiffness is far from complete, but established procedures do exist to obtain estimates of these parameters based on index and laboratory testing data and field mapping. Our ability to quantify field stresses is probably the most limited, in part because stress measurements are difficult and expensive to carry out, and in part because the stresses vary to an unknown degree from point to point within the rock mass. The engineer must, therefore, consider whether or not stress measurements are justified and, when they are, where the average stress state needs to be quantified and how many of which type of measurements will be required to determine the average stresses.Such was the case at Ansil mine, a massive sulphide deposit in hard rock located at a depth of more than one kilometre in the northern Québec portion of the Canadian Shield. The Ansil orebody was relatively rich, but small, with the potential for significant stress-related problems. As a result, geomechanical design had to be done carefully from the start – there would be little opportunity to modify the mining strategy once production had begun, and the economic consequences of stope dilution and rock mass instability would be severe. An extensive stress measurement campaign was carried out, but the determined stress magnitudes were unexpectedly low. The designers were, therefore, faced with a dilemma:"

Jan 1, 1997

By K. K. Panthi, P. K. Shrestha

"Displacement of rock mass around a tunnel opening varies according to the rock mass properties, insitu stress conditions and applied support in the tunnel. Such displacement is also altered by presence of bands of rock mass that differ in properties. This paper focuses on the deformation behavior of rock mass around tunnel openings at four tunnel sections in Kaligandaki headrace tunnel where extensive instrumentation was done. Based on the actually measured tunnel displacement records and actually measured support pressure; back analysis has been done to estimate rock mass properties and insitu stresses. Numerical analysis has been done to analyze and assess the deformation behavior of the rock mass around the tunnel sections.INTRODUCTION Instrumentation and monitoring of tunnel convergences have significant importance in evaluation of tunnel stability. One of the key aspects of monitored data is that early convergences can be used in estimation of long term convergence. In addition, these data can also be used in evaluation of rock mass parameters and in-situ stresses around the tunnel. Convergence around a tunnel periphery may vary according to rock mass quality. Presence of bands of different rock mass may hinder the displacement pattern in the tunnel. Particularly, displacement characteristic of tunnel periphery in schistose, foliated and deformed rock mass is altered by presence of bands of comparatively stronger rock mass, e.g., quartz veins or presence of shear seams or faults. Similar observations were also recorded in monitored tunnel sections in Kaligandaki headrace tunnel, located in the Nepal Himalayas. Extensive monitoring was done by installing multiple point borehole extensometers (MPBX) at three different locations of the tunnel periphery at four different tunnel sections. In addition, convergence measurements by tape extensometers and installation of pressure cells to record support pressures were also carried out at each of the tunnel sections. Observations showed that the tunnel convergences varied according to rock mass quality, in-situ stress and effective support pressure.Rock mass parameters and stresses have significant role in the extent of tunnel deformation, but these parameters are often unknown or difficult to predict. Back analysis based on actual tunnel displacement records and known support pressure is believed to be an important method in such endeavor. This paper performs back analysis to evaluate rock mass parameters and discusses correlation of rock mass behavior with tunnel deformation and applied support. For this purpose, the rock mass parameters are estimated from actual tunnel displacement records, mapped rock mass quality records and laboratory tested data. Then, numerical modelling is conducted to correlate post peak behavior of the rock mass with actual tunnel displacement."

Jan 1, 2015

By G. J. Knighton

Introduction The Sullivan concentrator treats the complex lead-zinc-iron ore from the Sullivan mine of the Consolidated Mining and Smelting Company of Canada, Limited, to make a lead and a zinc concentrate for its metallurgical plants at Trail. Three miles separate the mine and mill, which are situated near the town of Kimberley, in the East Kootenay district of British Columbia. The orebody consists typically of banded sulphides, mainly galena, sphalerite, pyrrhotite, and pyrite. Important factors in the concentration of the ore are its exceedingly complex and its high specific gravity. It should be remembered throughout the paper that results and figures are based on Consolidated's experience with the Sullivan ore. The present mill feed rate is 8,500 dry tons of ore per 24 hours, for an operating week of five and a half days. Grinding and classification of the ore are carried out in three stages and, in addition, there is a re-grind section which re-treats the zinc middling. It is the purpose of this paper to discuss the classification in the various stages and to give the results o comparative tests which have been carried out for the purpose of improving operations in the mill. The Primary stage consists of six units, each made up of a ball-mill and classifier (see accompanying flow-sheet). Four units operate in open circuit and two in closed circuit. The secondary stage consists of eight ball-mills operating in closed circuit with twenty-one classifiers. In the Tertiary stage are two ball-mills in closed circuit with eight classifiers. The re-treatment section for re-grinding the zinc middling comprises one ball-mill in closed circuit with two classifiers.

Jan 1, 1947

By M Reza Afshar

In this work a mathematical model was developed to study the effect of electromagnetic force on the magnesium melt containing nonmetallic inclusion in an electrical isolated channel. The electromagnetic force exerted on the inclusion induced by DC current field was calculated. A three dimensional turbulent flow equations were solved numerically to compute the velocity field within the channel. On the basis of computed velocity and magnetic fields, the trajectories of inclusions were calculated using the equations of motion for inclusions. Parametric studies were carried out to evaluate the effect of various parameters such as current density, channel diameter and particle density on the removal efficiency of inclusions from magnesium melts.

Jan 1, 2004

By H. P. Kang, Y. J. Feng

The hard roof in underground coal mines is generally considered as a main cause that induces disasters in working faces and entries, such as rock burst and windblast. Hydraulic fracturing technology is an effective approach to weaken hard roof to reduce ground pressure and control rock burst. The state and achievements associated with hydraulic fracturing technology applied in Chinese coal mines are summarized in this paper. Theories related to hydraulic fracturing are of the essence in fracture design to determine the fracture initiation and propagation pressure and predict the geometry and the characteristics of hydraulically induced fractures. Initially, theory of elasticity was employed to determine the breakdown pressure for a vertical borehole where the rock medium is assumed to be elastic. However, porosity and pore fluid have an influence on the borehole breakdown pressure, and then the poroelasticity theory was applied. Arbitrary deviated boreholes in practice are rather common and the maximum tensile stress criterion was employed to determine borehole breakdown pressure. The effect of natural crack in the rock medium on the initiation pressure has been taken into consideration through fracture mechanics. Meanwhile, considerable achievements have been made on hydraulic fracturing tools and equipment, and a set of mature hydraulic fracturing technologies for hard roof control are available. Some comprehensive investigations on the hydraulic fracturing for hard roof weakening are presented, and successful field applications in the Jincheng and Luan coal mining districts are introduced. Finally, the unsolved problems related to hydraulic fracturing are also put forward.

Jan 1, 2015

By V. S. Sastri, M. Elboujdaïni

"Corrosion rates of silicon brasses, highzinc yellow brass, low-zinc yellow brass, leadedtin bronze and silicon bronzes in both permanent-mold and sand-cast conditions were determined in soft water of pH 3, 5 and 8, and hard water of pH 8 at 70°C by electrochemical polarization technique. The alloys in permanent- mold condition showed greater corrosion resistance than sand-cast condition. Corrosion rates obtained from weight loss measurements showed no observable trend of a difference between permanent-mold and sand-cast alloys.The corrosion rates decreased with increasing pH of the medium. Silicon bronze and silicon brass showed high corrosion resistance while leaded-tin bronze showed the least resistance. Addition of small amounts of aluminum improved the corrosion resistance of silicon bronzes and silicon brasses. Alloys in permanent- mold condition showed greater resistance to dezincification than sand-cast alloys when average pit depth parameter is considered."

Jan 1, 1997

By R. Heikkilä

In this paper the utilisation of building information models (BIM) and construction automation on building sites is discussed. A lot of research has been carried out to develop new applications for using BIM to assist construction site planning, different operations and logistics. The methods of production control and management on site utilize BIM together with machine control and navigation systems. In Finland machine control systems and the automation of construction equipment is widely used in infrastructure construction. Recently similar methods have been introduced also in building construction. This paper describes some latest Finnish examples where BIM-software is used for the planning, execution and control of building construction operations. University of Oulu has studied methods and technologies to capitalize BIM-models. The research has been mainly in infrastructure construction but the activities have recently been extended to building construction. In this paper a BIM-based tower crane operation and control system is discussed as a case study. The aim of this study was to highlight the potential areas were automation can increase the crane productivity and improve site operations and logistics. The construction site managers and tower crane operators interviewed in this study were experienced in using BIM-models on site.

Aug 1, 2013

By M. Moats, J. A. Gonzalez

A review of operating practices in zinc electrowinning plants is presented in this paper. Surveys were sent to several zinc electrowinning plants and data provided by some of these plants was compiled in a database. Information about anodes and cathodes, electrolyte composition, stripping methods, cells, electrical systems, and additives was compiled and analyzed. From the data analysis, correlations between operating variables are presented. Recent trends in operational practices are also highlighted.

Jan 1, 2008

By Stephen Hardcastle

Presentation Outline ? Introduction ? Mine Ventilation Facts ? Ventilation-on-demand (VOD) ? Sensors/Controls ? Continuing Work ? Conclusions ? Mine ventilation engineering practices were published in 1556 in Agricola?s De Re Metallica (wind sails, bellows, etc.) That was then? This is today? Large fan installations handling >1M cfm

Nov 1, 2011

By T. E. W. Nind

"A short description of the chamber lift method for producing oil wells is followed by some comments on compressor requirements and gas utilization. A quantitative analysis of the process is presented and, based on this analysis, criteria are suggested for selecting wells for which this type of lift might be suitable. The analysis leads to the conclusions that chamber lift is an efficient producing mechanism for wells having very low productivity indices (say about 0.05 bbl/d/ p.s.i. or less), but that for such wells optimum utilization of injection gas cannot be attained. It is suggested that the gas injection time per cycle should be kept as low as possible, compatible with a small oil fallback volume, and that the cycle frequency should be in the range of 20-40 cycles/ day. For wells with productivity indices of 0.2 bbl/d/p.s.i. or higher, chamber lift is relatively inefficient; how-ever, if well allowables are low it may offer an attractive, low cost, alternative to gas lift or pumping."

Jan 1, 1960

By Kenneth L. Norris

Stonegate Agricom Ltd. is currently conducting exploration and development drilling of the Paris Hills Phosphate Project (Paris Hills Project) located in Bear Lake County, southeastern Idaho, 3.2 km west of the towns of Paris and Bloomington, Idaho. The project is located adjacent to a highway and 19 km by paved highway to Montpelier, Idaho where the Union Pacific Railroad system is located. Power and water are available locally. The nearest metropolitan centre is Salt Lake City, Utah approximately 225 km by road to the south-west of the property. The Paris Hills Project encompasses an area of approximately 856 hectares. Property holdings consist of three (3) patented lode mining claims and 16 contiguous fee parcels (some with federal phosphate leases). Active open pit phosphate mining operations are located in surrounding counties in south-east Idaho and are owned and operated by Agrium Inc., Monsanto Company and J.R. Simplot Company. The Paris Hills Project is located near the centre of the Western Phosphate Field which constitutes the most extensive phosphorite beds in the United States. Phosphate beds of the Western Phosphate Field occur within the Phosphoria Formation of Permian age and extend over an area of more than 350,000 km2 including extensive areas of Idaho, Utah, Wyoming and Montana. At Paris Hills the phosphate mineralized beds occur in the overturned limb and the horizontal limb of the Paris Syncline. Grades and thicknesses in both the western overturned limb and the eastern horizontal limb of the anticline are similar. The vast majority of potential mineralization occurs in the horizontal limb which underlies most of the property holdings. Mineralization in the overturned limb has a strike length of over three (3) kilometres and extends from the surface to a depth exceeding 300 m depending on location along the north-trending strike of outcrops. Depths of the horizontal limb range from surface along the north side of Bloomington Canyon to estimated depths of 915 to 1,035 m at Paris Canyon. The property contains an Inferred resource of 109.6 million tonnes at 23.6% P2O5 over two mineralized horizons. The phosphate zones have a strike length of over 3 km and extend from surface to a depth of at least 900 m. Drilling commenced late in the 3rd quarter of 2010 and is planned to continue through 2011. The drilling was planned to target an area of potentially higher grade phosphate mineralization and better define and upgrade the current resources.

May 1, 2011