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By S. Sunkavalli

Acid rock drainage (ARD) is produced when sulfides are exposed to oxygen and water. Oxidation reactions typically result in a depression of pH and leaching of solutes and metals. Many oxidation models have been developed based on oxygen diffusion, but in environments with high permeability, other transport processes (i.e., convection and advection) can play an important role. Multiple sulfide mineral phases with differing oxidation rates should also be incorporated. WROC, a finite-difference model, was developed to account for these factors in predicting ARD. The program includes sulfide mineral oxidation using a shrinking core mechanism, heat transfer by conduction, heat of reaction, and oxygen transport by diffusion and advection. The model was validated using data from the literature. After validation, the WROC model was used to simulate several different waste rock scenarios including different forms of sulfide mineralization and the effect of implementing a waste rock cover. The results demonstrate that including specific sulfide mineral phases can have a significant effect on oxidation and that implementation of a cover can also aid in reducing waste rock oxidation. Key words: Arsenic sulfides, oxidation, shrinking core, waste rock, oxygen transport

Feb 27, 2013

By Christopher J. Bise

INTRODUCTION The transportation of men, supplies, and mined material from an underground operation is the connecting link between the mine plant and the surface plant. Unless the mine is accessed by a drift or adit, some form of hoisting system is necessary for slopes or shafts. This chapter will deal with the selection of wire ropes and hoists, two of the most important consider¬ations when designing a hoisting system for an under¬ground mine. WIRE ROPES General A wire rope is designed to transmit forces longitudi¬nally along its axis. Wire rope is used in a variety of mining applications because of its flexibility, high ten¬sile strength, and dependability. Shaft hoisting ropes and principal slope haulage ropes are usually custom-¬built; however, proper rope selection for slushers, car spotters, etc. should not be overlooked. Wire ropes for shafts and slopes, since they represent the life line for the mines, should be of the very highest quality improved plow steel. This quality is necessary to deal with the conditions of loading, winding, vibration, abrasion, and corrosion. Tables I and 2 display the specifications for the typical wire ropes used for mine haulage applications. The 6 x 19-class haulage rope is used for most hoisting where abrasion is not critical. On the other hand, where abrasion is critical, such as a slope application, 6 X 7-class haulage ropes are preferred. For other mining applications, manufactur¬ers' handbooks should be consulted. Selection The selection of a wire rope for a mining situation consists of simply applying appropriate safety factors to a calculated maximum rope pull and comparing the result to the listed breaking strength of the rope under consideration. Table 3 can be used for determin¬ing the minimum factors of safety for wire ropes. To determine the maximum rope pull, the following quantities must be known: the rope weight in pounds (x), the conveyance weight in pounds (y), and the weight in pounds of the load in the conveyance (z). These values are used to calculate the load due to gravity, the load due to conveyance friction, and the load due to rope friction. When these loads are added together, as shown in Eq. 1, the maximum (static) rope pull (RPS) can be derived:

Jan 1, 1986

By J. E. Warren, J. H. Hartsock

An asymptotic solution to the equation that describes the flow of a slightly compressible fluid in an infinite porous medium has been used to estimate the interaction between two adjacent wells producing from a common reservoir. A direct method for approximating the interference time defined by Stevens and Thodosl has been suggested. An alternative definition for the time of interference, based on the minimum pressure change in the interference region, has been proposed; also, a direct method of determination has been prescribed. Examples have been employed to illustrate the use of both methods.

By William H. Schiffbauer

One of the safety and health research programs of the former U.S. Bureau of Mines Pittsburgh Research Center was the evaluation of technology that will provide remote-controlled operation of mechanized equipment in underground room-and-pillar mining. The purpose of this effort was to enable workers to be located away from the hazardous and unhealthful coal extraction area (the face). As part of this program, advanced machine navigation and control technologies were developed for underground room-and-pillar and highwall coal mining that can be applied to commercially available mining equipment. These technologies use off-the-shelf components and a flexible control software architecture to minimize the effort required to adapt them to mining equipment. An accurate, reliable navigation system that can provide the mining machine's heading and location is a critical requirement for a remote-controlled mining system. After investigating several different types of navigation sensors, researchers selected the Honeywell Ring Laser Gyro Inertial Navigation System (INS) as showing the most promise. It was installed on a continuous mining machine at our Mining Equipment Test Facility. Extensive testing at an open pit (OP) site was also performed. This report describes the INS as it was employed on the mining machine in the laboratory, in the field, and OP tests, and provides the accuracy and performance results of the OP and highwalltests.

Jan 11, 1997

The following data are put together to assist those who are responsible for ordering stores for mines and works. When making out a list of mine stores for a new plant, one can hardly be expected to remember everything, still it is all the more important that articles should not be forgotten, should the mine be situated in an out of the way place, where the manager has to look several weeks ahead. A man who has been accustomed to buy stores on a small scale, from local merchants, where he could pick out personally what he wanted, may suddenly find himself in a place where he has to order wholesale quantities or make out store lists to send contractors for quotations. As it is of course cheaper to purchase stores by the hundredweight, coil, barrel, etc as the case may be, in which they are made up, than to break such a parcel, the way in which the materials are placed on the market is mentioned, so that those who don't know may take full advantage of wholesale terms. The most frequent sizes and brands employed in connection with Australian mining are also mentioned. It would be useless to enumerate all sizes made by the trade, as many would be of no value for our purpose; still I have put down what will serve as a reminder to the manager to mention what size he requires when giving an order, such as the diameter of dynamite cartridges a slight neglect of this sort has often caused serious delay. By mentioning certain brands I do not wish to recommend them in preference to others inadvertently omitted they are simply mentioned as some of those frequently met with.

By A. Hashempour, D. Javani

"Selection of an optimal bit is a critical issue in drilling engineering. Specific energy (SE) and Cost per Foot (CPF) are the most common methods for evaluation of bit efficiency and optimal bit selection. The major shortfall of both methods is that they do not directly account for geological and geomechanical parameters of formations being drilling. In this paper, results of using the two foregoing methods are compared using Formation Drillability (FD) method, which directly accounts for geological and geomechanical parameters of a formation. This method combines various geological and geomechanical parameters and yields a dimensionless parameter indicating the formation drilling hardness (drillability). Results of this study show that the amount of energy, cost and time spent for drilling a unit volume / length of an identical formation may vary in different wells. This is due to the fact that geological and geomechanical characteristics of a formation may vary among wells and even within short intervals of a single well. Therefore, an optimal bit may not be appropriately selected, if drilling and economical parameters are the only factors considered and the formation geological and geomechanical specifications are ignored.INTRODUCTIONMany authors such as Bilgesu, Al-Rashidi, Aminian, and Ameri (2000) and Clegg (2006) conducted research in the evaluation of bit performance and optimum bit selection. Almost all of them tried to establish a good relationship based on geomechanical parameters. Primary examples are the research done by Ubaldi (1999), Macini, Magagni, Da Dalt, and Valente (2007)."

Jan 1, 2015

By B. Macdonald

In 1991, roofbolts were introduced as a primary support for inseam retreat longwall entries at CBDC's Phalen Colliery. Increasing mine depth (+550 m) necessitated replacing conventional inseam steel sets in these entries because they were being severely damaged during wall retreat and subsequently causing gate end problems. Roofbolts had been used in the Sydney coalfield between 1949 and 1963 in room and pillar working, however, some concerns arose with using roofbolts as a primary support in long (2.2 - 3.4 km) single entry roadways. In order to alleviate these concerns, a phased approach was adopted whereby conventional steel densities remained along with roofbolts. The roofbolt design was such that the roofbolts would be the primary support and the steel sets would experience little or no loading. A detailed geotechnical monitoring program was developed by both CBDC and the Cape Breton Coal Research Laboratories technical staffs. The results of this monitoring were used to build-up confidence in roofbolts and subsequently reduce the steel set densities until eventually only roofbolts were used as a primary support. This paper will discuss briefly the phased introduction of rootbolts at Phalen Colliery and more specifically the development of geotechnical data collection and interpretation.

Jan 1, 1994

Observed mineral assemblages in the Mt. Lyell copper deposit can be correlated with phase equilibrium investigations in the systems Cu-Fe-S and Fe-Zn-S. The trend of crystallization (or paragenetic sequence) of the ores is reflected in a progressive increase in the Cu: Fe and metal: sulphur ratios of the assemblages. This trend agrees with the regional zoning of the district. Tentative relationships between the paragenetic sequence, sulphur vapour pressure, and temperature are presented graphically. The absence of a suitable geological thermometer prevents precise elucidation of the range of temperatures and pressures which existed during crystallization.INTRODUCTIONRecent phase equilibrium investigations of metal-sulphur systems at the Geophysical Laboratory, Washington, D.C. provide valuable information on the stability relations of a number of important sulphide minerals. This data, when applied to natural ore deposits, may be expected to clarify two special problems which confront the ore petrologist seeking to interpret observed data in terms of a particular physical and chemical environment of ore deposition. These two problems are the sequence of formation of sulphide minerals (commonly designated the paragenetic sequence) and an elucidation of the range of temperatures and pressures which existed during crystallization. The object of this paper is to make such an interpretation of the copper mineralization of the Mt. Lyell district, Queenstown, Tasmania.The following abbreviations are used in this paper:py = pyrite, cp = chalcopyrite, en = cubanite, bn = bornite,cc = chalcocite, cv = covellite, dg = digenite, id = idaite,po = pyrrhotite, v = sulphur vapour.GEOLOGICAL SETTING AND MINERALIZATIONThe general geology of the Mt. Lyell district is well known through the recent work of Wade and Solomon (1958). The host rocks are a series of quartz-chlorite-seri-...

Jan 1, 1963

By N A. Sikwa, L M. van Niekerk, G N. Ndlovu

In June 2012, Lucara Diamond Corporation officially commissioned its Karowe Diamond Mine in Letlhakane, Botswana. The processing plant circuit incorporates variable speed autogeneous milling, a first for African diamond processing - only previously practiced in Russia. The paper discusses the basis for the selection of milling against the more traditional circuits incorporating crushing and scrubbing. It covers early commissioning challenges of operating a mill in an æalien environmentÆ with no immediate reference plant to look up to for bench-marking.The paper describes how these challenges were overcome and learnings quickly incorporated into the mill operating philosophy for maximum diamond liberation and minimum product damage. The plant was commissioned in three months and by August 2012 the production ramp up had reached name-plate capacity. The feed to the mill has varied from highly weathered material to extremely hard kimberlite and the operating philosophy had to be optimised for the full range of ore types. While more work is required to stretch the mill operating envelope coupled with other circuit additions to improve liberation of fine diamonds at minimum capital expenditure, the mill has, to date, performed to its billing.CITATION:van Niekerk, L M, Ndlovu, G N and Sikwa, N A, 2013. Commissioning and operating an autogeneous mill at Karowe Diamond Mine, in Proceedings MetPlant 2013 , pp 215-228 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 15, 2013

By W. A. Tiller, J. D. Harrison

HOT pressing of powder particles has gained importance recently, since it affords a method in which high densities are rapidly attained. In a recent study on hot pressing of alumina powders, Mangsen, Lam-bertson, and Best1 have shown within the limits of their experiment, the validity the rate equation for densification in hot pressing, originally proposed by Murray, Livey, and Williams.2 i.e., where D = fraction of theoretical density, t = time, P = pressure and 77 is the viscosity, all in appropriate units. This equation was derived from earlier work of Shuttleworth and Mackenzie3 which is based on the closing of spherical pores under the action of surface tension. The integrated form of this equation yields a straight-line relation between log (1 - D) and t. Such conditions were found by Felten4 to be true only after extended periods of pressing. In an endeavor to quantitatively evaluate the exactitude of this equation in the initial sintering stage, i.e., prior to sealing of the pores, spherical anti-

Jan 1, 1962

By D. E. Kirby

The electrochemical reduction of AlC13 was investigated as a process for the production of aluminum. An externally heated, single-compartment cell with a rammed refractory lining was used with molten KCl-NaCl-AlC13 electrolyte. Aluminum was deposited qt 700° to 760° C with a current of 100 to 200 amperes on a molten aluminum cathode. Chlorine was evolved at a graphite anode and collected and measured to provide a quantitative evaluation of the AlC13 reduction. Aluminum was removed from the cell by siphoning or ladling. Granular AlC13 was added periodically to replenish that depleted from the electrolyte. Concentrations of 7.5 to 17.5 percent AlC13 in the electrolyte were optimum for operation. Anode current efficiencies of 83 to 85 percent were attained, using anode current densities of 5.9 amperes per square inch and an anode-cathode distance of 4 inches. The chemically bonded, alumina liner was resistant to attack by aluminum and chlorine but susceptible to erosion at the surface of the electrolyte. Titanium diboride proved suitable for the electrical connection to the molten aluminum cathode. Aluminum of a purity equal to or better than 1100 series metal was electrowon continuously from commercial AlC13 for a period of 4-1/2 months.

Jan 1, 1970

Raw materials account for over 60 per cent of the cost of hot metal production in classical blast furnaces and the principal cost component is cost of coke. Dependence on coke is a traditional weakness of blast furnace ironmaking and while efforts have been made to evolve alternative ironmaking technologies which do not use coke, such as direct reduction, smelting reduction, and the more recent method of making iron carbide, blast furnaces continue to be the most efficient means of producing bulk hot metal even today. Coal injection, to the extent of 150 - 200 kg/t of hot metal, has been one of the major innovations made in blast furnaces to decrease cost and to reduce the dependence on coke. This has, however, given rise to more stringent coke property requirements (which often means more expensive coke) - a `tail spin' of Sorts!

Jan 1, 1999

By Roozbeh Afzali

Designing an appropriate tunnel blasting pattern reduces the cost of rock breakage and subsequent operations such as loading, haulage and support of tunnels. For that reason, we developed a software that designs tunnel blasting patterns. Using this software, three different tunnel blast design models based on parallel hole cut, namely, Swedish, Konya and Energy Balance, were investigated and compared for a virtual tunnel. Accordingly, blasting patterns were designed, for different cross sections. The trend of parameters such as specific charge and specific drilling as functions of tunnel cross-section was determined for each model. Our results show that, in general, The Swedish model gives lower specific charge and specific drilling compared to other models.

Jan 1, 2008

By Loris S. Russell

THE plains of southern Alberta constitute one of the classic areas of geological investigation in Canada, for it was here in 1874, and in 1881 to 1883, that George Mercer Dawson (1, 2, 3) made the pioneer observations that are basic to all subsequent work on the interior plains of Canada. Dawson's work was extended eastward by R. G. McConnell ( 4) and northward by J. B. Tyrrell( 5) , but it remained. for D. B. Dowling to re-examine Dawson's Bow and Belly River Area and to make certain necessary revisions in the stratigraphical system of his predecessor. In 1917, Dowling published his memoir, The Southern Plains of Alberta( 6) , which remained for over ten years the last word on the stratigraphy and structure of the area described. It is generally conceded that Dowling's work made known the existence of a great artesian basin beneath the semi-arid plains of southeastern Alberta. In addition, his structural studies greatly stimulated the search for natural gas and petroleum. The most recent general publications on this area by the Geological Survey are based on the field work of M. Y. Williams, E. J. Whittaker, W. S. Dyer, and P. S. Warren, between the years 1923 and 1926. Their results were embodied in the Calgary Sheet (7) and the memoir, Geology of Southern Alberta and Southwestern Saskatchewan (8). By this time, the number of geologists working in Alberta in the development of the petroleum and natural gas industries had become large, and in 1931 the Alberta Association of Petroleum Geologist~ offered the Donaldson Bogart Dowling Memorial Symposium on Stratigraphy of Southern Alberta( 9) , a most valuable series of papers descriptive both of the ,surface stratigraphy and that observed in the well records.

Jan 1, 1937

By Luciano Aparecido Kempski

O ferramental utilizado em processos de conformação é de grande interesse da Engenharia de Superfícies devido às características tribológicas específicas encontradas nestes processos. Portanto busca-se sempre melhorar o ferramental para se obter menores coeficientes de atrito, desgaste e adesão de material sobre a superfície da ferramenta, sendo empregadas diversas técnicas de tratamentos superficiais como a nitretação e os revestimentos depositados via PVD. Uma variável importante do par tribológico é o coeficiente de atrito desenvolvido entre as superfícies em contato nos processos de conformação a frio, portanto foram realizados ensaios de pino-sobre-disco e ensaios DST, para determinação de coeficientes de atrito em pares tribológicos. Desta forma, chapas de aço inoxidável austenítico AISI 304 foram conformadas sobre uma superfície de um aço ferramenta DIN X100CrMoV8-1-1, com o propósito de se conhecer o atrito desenvolvido entre os materiais. As amostras foram nitretadas a plasma e ou revestida com TiCN, posteriormente, a caracterização da microestrutura e as propriedades avaliadas através de ensaios mecânicos e tribológicos. O ensaios proporcionaram obter valores de coeficiente de atrito para as condições de tratamentos e lubrificação utilizados e as análises dos resultados mostram um aumento da dureza superficial das amostras tanto nitretadas quanto revestidas com TiCN e uma redução do coeficiente de atrito significativa quando se faz uso do revestimento.

Aug 8, 2018

Residual aeolian placers (RAPs) are formed by the wind, by preferential entrainment and removal of small and low-density detritusfrom a pre-existing, typically sedimentary sequence containing heavy minerals. Heavy minerals that are resistant to chemical alteration and either soft and malleable (gold), or extremely hard (diamond, sapphire, ruby, etc), are concentrated as a residual on the wind deflation surface, typically in the interstices between larger resistant clasts. RAPs form preferentially in arid or semi arid areas, where the vegetation is sparse or absent, and where topography and surface gradients are low, but may also form on beaches and in periglacial environments. RAPs consist of a continuous or discontinuous, planar or gently undulating horizon of heavy minerals in a single-clast-thick pavement of resistant pebbles, cobbles, or boulders, which mantles the present topography or palaeo-topography. Extreme wind erosion and surface deflation may condense the full pre-existing sequence into a layer of heavy minerals only. The grade of RAPs is substantially higher than in the precursor deposit, and commonly much higher than those typically found in most other placer types. Aside from their general occurrence as a thin pavement of resistant clasts, the best indicators of residual aeolian gold placers are the presence of wind-eroded stones (ventifacts) on the pavement, and the distinctive and unique shapes of aeolian gold grains themselves. The shape of the gold grains is progressively transformed by sand blasting during placer development, from grains with thickened rims, to toroidal grains on which the rims are æsplitÆ and peened inward toward the grain centre on one or both of the grain sides, to hemispherical or sub-spherical grains that are fully encapsulated by the in-turned rims. Gold that has undergone aeolian shape transformation is difficult to entrain and transport away from the site of aeolian concentration by anything other than mass movement or glacial processes. It is also easily retained by commercial recovery plants of any configuration.

Jan 1, 2004

By Roy A. Imbsen

Following the 1989 Loma Prieta earthquake, California Department of Transportation (Caltrans) expedited an effort to evaluate and retrofit important state-owned toll bridges to en­hance performance of the state's transportation systems during and after major (credible) earthquake events. Imbsen and Associates, Inc. (IAI) along with their sub-consultants, were awarded a contract to conduct seismic evaluation and to develop retrofit design for Benicia-Martinez Toll structure, to meet a "Serviceable" performance requirement after the event of a "Safety Evaluation Earthquake." This paper describes the design and construction specifications for the deep foundations supporting the main spans of the Benicia-Martinez Bridge. Benicia-Martinez Toll Structure (George Miller Bridge), a high-level deck-type welded truss bridge with welded girder approach spans, carries Interstate Route I-680 over the easterly end of Carquinez Strait near San Francisco, CA. The nearly 5000 ft long main truss structure consists of ten spans, ranging from 330' to 528' in length, supported on cellular reinforced con­crete pier structures. Foundation systems across the waterway, consist of cellular reinforced concrete footings, supported by groups of 6' diameter, concrete filled, steel caissons, resting on 5' deep rock sockets, at depths of 50' to 150' below the water level. Seismic evaluation of the existing foundation systems accounted for spatially varying ground motion along the length of the structure, variability of foundation material strength (i.e. at bed-rock), variation and effects of scour depth on the performance of the foundations, and dy­namic soil-structure interaction. Performance of caissons beyond their elastic strength, as well as their effects on the behavior of the foundations and substructures were evaluated and considered in establishing foundation vulnerabilities. Several retrofit strategies were considered leading to a final retrofit strategy to strengthen end connections of existing caissons, as well addition of new caissons to provide adequate lateral force resistance for the foundations. Final design package includes specifications as well as construction methods and requirements for existing and new caissons, under traffic, and pile load testing procedures for design loads of up to 12500 kips per caisson.

Jan 1, 1998

By Harold W. Lipper

BUREAU OF MINES helium plants produced a. record-breaking 477 million cubic feet of this essential element in 1959. The supply of helium was less than the demand before operations were resumed at the Navajo plant in July and begun Sit a. new plant at Keyes, Okla., in August. Helium was in abundant supply after August, and the informal allocation system which had been in use intermittently since 1955 was discontinued Delivery of 26 new tank cars in August and September increased the total in the tank-car pool to 163. Defense and space agencies and the Atomic Energy Commission continued to use more helium in their operations and research.

Jan 1, 1960

By E. W. Greig

This paper is an account of exploration for bauxite in the Amazon Basin, Brazil, and particularly of the discovery, exploration and development by Alcan of the Trombetas deposit so a general account of the Trombetas Project has already been published in E/MJ (Anon. 1975) to which the reader is referred for details on owner-ship, infrastructure and construction as well as the proposal for mining and treating the bauxite. It is impossible to consider the Trombetas deposits in isolation. A regional account of bauxite in and around the Guyana Shield and the northern portion of the Brazilian Shield is included and it is suggested that these deposits all formed during Tertiary time under similar conditions.

Jan 1, 1977

By Yindong Yang

Despite the importance and usefulness of basicity in metallurgical slags, the optimum quantitative expression of it has remained elusive, partly due to the fact that the precise concept of basicity has not been properly clarified. The two basic approaches to the concept of basicity are the Lux-Flood, which perceives basicity in terms of the activity of the free oxide ion, a O2- , and the Lewis, which perceives basicity in terms of the ability to donate negative charge. The former has been almost universally adopted in the area of metallurgical slags, while the latter has been increasingly accepted in the field of glass chemistry. In this paper, some difficulties of the Lux-Flood approach are pointed out, including the need for indirect measures of a O2- , which have proliferated in recent years. Accordingly, it is suggested that the Lewis approach has a good deal to commend it, and that the quantification of it in terms of optical basicity is the best measure of basicity available, which should therefore be more widely applied in metallurgical slags than it currently is. The fact that there are intrinsic problems in evaluating the optical basicities for the transition metal oxides is acknowledged, and a new scale is recommended. The patterns of iso-optical basicity lines in ternary systems are shown to agree well with the pattern of iso-activity and iso-capacity lines under appropriate conditions. * Originally published in the Proceedings of MINPREX 2000, published by The AusIMM.

Jan 1, 2001