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By Z. Eisenstein, H. K. Heinz, F. M. Kuwajima

Due to its complex rheological behaviour, shotcrete induces a ground-structure interaction that differs significantly from other types of tunnel linings. For the same reason, the instrumentation of shotcrete linings presents special problems, particularly when it comes to estimating the stresses transferred to the lining during construction. The shotcrete characteristics which affect the stress distribution are initially discussed. Measurements obtained in a recent soft ground tunnel are also presented. The conclusions are aimed at introducing practical recommendations for the design of tunnels where shotcrete is used as initial and/or final support.

Jan 1, 1991

By M. Quamrul Ahsan, Andrew Griffiths, Edward P. Jucevic

Heap leaching of precious metal ores using the cyanide process is extensively used in the Western U.S.A. for extracting gold. Consequently, the impact of cyanide in the spent heap is closely examined by environmental agencies and permitting authorities. Currently, many states require that all decomnissioned heaps be detoxified before abandonment. This paper describes a case study for detoxification of spent heaps at the ACH-Dayton Project using hydrogen peroxide. The chemistry of cyanide detoxification by hydrogen peroxide, together with simplicity of a detoxification operation, is discussed.

Jan 1, 1989

By Lynton S. Land

Representative collections of recent dolomites, and of samples concentrated by leaching-out of coexisting magnesian calcites, provide grounds for appraisal of the compositions and cation ordering in recent dolomitized sediments. Unit cell volumes for near-stoichiometric compositions exceed those of ordered dolomite and increase as the departures from regular cation order became more pronounced. Infrared absorption maxima of disordered examples occur at perceptibly lower frequencies. Stable isotope ratios indicate that best ordered examples formed in highly saline environments. Present observations are qualitatively reconciled with data from synthetic products described by other authors.

Jan 1, 1972

By G. K. Roset, L. R. Woodland, J. A. Stevenson, G. J. Hodges

The Stillwater Mining Co. (SMC) is a partnership of Pittsburg & Midway Coal Mining Co. and Manville Corp. Since the summer of 1990, SMC has operated a precious metals smelter at Columbus, MT for further upgrading of concentrates from its platinum-palladium mine. The facility's gas-cleaning system utilizes "oxidation/dilute-mode," dual-alkali scrubbing technology to capture sulfur oxide gases from the process gas streams. This paper describes the rationale for selecting the dilute-mode, dual-alkali system and summarizes the design parameters. Also discussed are the startup problems encountered and their solutions.

Jan 1, 1993

By Donald G. Foot, Jeffrey D. Mckay

Flotation columns have been readily accepted for use in most sulfide flotation plants: however, recently columns are being used in many other areas. Recent improvements in design methodologies have overcome many operating problems and led to improvements in metallurgy. In addition. Physical improvements in column design have simplified their operation while leading to better control. The Turbo-Air External Bubble Generator has provided a method for bubble size control and variation in air holdup and carrying capacity. These have enabled commercial operations to improve grades and recoveries by optimizing performance.

Jan 1, 1989

By N. T. Rempe

The underground voids that result from mining provide opportunities for deep geologic waste disposal (DGWD). Such disposal could solve many environmental problems. DGWD takes careful planning, technology transfer and true partnership between waste generators and mine/repository operators. The US government is now planning on using specially mined excavations to dispose of radiotoxic and mixed waste. Using the experience gained from the domestic projects that are now in preparation and from foreign repositories that are now in operation, US mines can claim their rightful share of the growing market for DGWD.

Jan 1, 1998

By J. A. Burger

Research in the eastern U.S. has shown that productive mine soils and forests can be restored using the following guidelines: (1) cooperation among the mine operator, landowner, and regulatory authority in developing the mining permit; (2) replacing topsoil or creating a desirable medium in which trees are planted; (3) loosely grading non-compacted topsoil; (4) using native and non-competitive domestic ground covers that quickly protect the site; and (5) planting a proper silvicultural mix of crop trees for their commercial value along with nurse trees for wildlife and soil improvement.

Jan 1, 2002

By A. Arik

The accurate estimation of mining-block grades continues to be a challenging task for ore reserve practitioners. The estimation method used and the variability of the mineralization in the deposit are two factors that affect the accuracy of the estimates. The objectives of this study are to determine how different estimation methods perform on a given deposit and to determine the impact that the nature of the mineralization has on the results. A comparison of several estimation methods for prediction accuracy is performed based on conditional simulation results.

Jan 1, 2002

By A. M. Abouzeid, R. Hogg

Materials transport is involved in all phases of mineral processing. Bulk transport is necessary for moving materials between unit operations and through processing devices such as grinding mills. Differential transport is a primary mechanism for most separation processes. The basic mechanisms of transport and flow in particulate materials are reviewed and their role in materials handling and storage and in the performance of processing operations such as grinding and separation are discussed. Specific examples are used to illustrate current understanding of these transport phenomena and to indicate important research needs and opportunities.

Jan 1, 1989

By Robert C. Bates

Published information on costs of radon-daughter control in uranium mines was analyzed to develop estimates of the cost per ton for any level of radiation exposure control. All data were converted to 1967 cost of living index to provide a common analysis base. Results of the analysis show that the cost per ton increases exponentially as the radiation level is lowered. A linear relationship with the cost of living index is assumed, and equations and graphs are provided to estimate control cost per ton for any exposure control level and cost of living index.

Jan 1, 1981

By G. Banini

A plug-flow model is described for the reactor mass balance of a typical AARL gold elution process. The model is in the form of a hyperbolic differential equation and was transformed using the method of characteristics. The transformed model was then solved simultaneously with models dependent on intraparticle surface diffusion and film transfer parameters. The solution was found to represent the experimental data for a modified form of the AARL elution. Correlation between the experimental conditions and the film transfer parameters estimated by the model are also presented.

Jan 1, 1998

By S. K. Kawatra, T. C. Eisele

Under normal conditions, a significant amount of pyrite is recovered in the froth during flotation of high-sulfur coal. To reduce this pyrite recovery, it is first necessary to determine the primary recovery mechanism, because different measures are required for reducing entrainment, locked particle flotation or true hydrophobic flotation. In this paper, evidence is presented that suggests that hydrophobic flotation is not the major mechanism for recovery of liberated pyrite; instead, the bulk of the recovered pyrite results either from simple entrainment or from being physically locked with floatable coal particles.

Jan 1, 1993

By B. K. Parekh, R. H. Mehta

The handling of fine coal is an important issue for both the coal and utility industries. Reconstitution of fine coal in the form of pellets or briquettes would be desirable if it could be done economically. This paper evaluates the effectiveness of three binders, asphalt-emulsion, corn starch and Brewex, informing pellets of ultrafine clean coal. It was found that asphalt-emulsion and corn starch were not effective binders. However, the use of Brewex resulted in pellets that exceeded all of the minimum quality requirements for coal pellets.

Jan 1, 1997

By Gerald H. Luttrell, Roe-Hoan Yoon

Flotation columns are becoming increasingly popular due to their ability to improve selectivity and to reduce operating costs. Unfortunately, these advantages are not often realized because of poor operating practices and difficulties associated with design and maintenance. This article provides guidelines for the operation and design of columns. The discussion will focus on designing proper wash water systems for improved selectivity, maximizing throughput by increasing the bubble surface area rate, and minimizing operating and maintenance costs. It is suggested that the design of the air sparging system is the most critical element in column flotation.

Jan 1, 1993

By W. R. Penney, J. M. Richardson, J. Y. Oldshue

Introduction The mining industry has for years underrated the value of mixing in mineral processing unit operations. In present-day operations where leaching is playing an ever increasing role in the total profit picture, the need for good mixing is becoming more obvious. The engineer in the research laboratory and in the operations is by necessity becoming more familiar with the concepts of mixing. This section is designed to provide the engineer with mixing data and correlations sufficient to assist in the general planning of simple mixing systems.

Jan 1, 1985

By J. Andrew Leach, Robert T. Tape, Thomas G. Harper

A practical approach to elope stability design of heap leaches up to 90 m (300 ft) high is presented based on recent experiences with heaps throughout the Western U.S. Shear strength parameters for foundations, ore and liner systems are considered, with particular attention given to frictional contacts between geomembranes and clay or geotextiles. Stability of both ore and containment dikes is discussed including the effects of seismicity, staged dike construction, progressive heap development and in-heap solution levels. Design criteria and methods of analyses are presented along with techniques for improving stability.

Jan 1, 1987

By R. P. Moran, B. C. Lewis

The objective of this article is to discuss the fundamentals for determining the value of a limestone reserve or operation. The general step-by-step procedure, while prudent, is subject to the various site-specific issues that influence the valuation calculation. The most common methods for determining fair market value of mining lands are: comparable sales, operational analysis, and royalty analysis. An overview of typical eastern limestone mines (both quarries and underground) is presented. Specifically, properties in West Virginia and Alabama are reviewed and the sample methodologies and valuation calculations are presented.

Jan 1, 1991

By S. Chander

The effect of pretreatment potential on the response of a gold electrode for Eh measurements in sulfide solutions was examined in terms of measured Eh values and electrode response time. The electrode response time is defined as the time required for the electrode to reach a steady-state value. The relationship between measured Eh values and the hydrosulfide ion concentration is established. The effect of pH, the reversibility of the gold electrode in the sulfide solutions, and the reproducibility of measurements are also investigated. A mixed potential theory is proposed to explain the observations.

Jan 1, 1989

By Håkan Tyni, Jan Björkman, Per-Olaf Samskog, Irving Wigdén

Process automation can provide better utilization of capital investments. Furthermore, it is a necessity for securing the high demands of product quality. In this paper, process automation in underground mining as well as in the beneficiation plant will be discussed. The development of reliable broadband communication systems for real-time transfer of image, audio and data have enabled remotely controlled LHDs and drilling rigs. In the beneficiation plants, model-based expert control systems far on-line dynamic process optimization and control have been installed in unit operations such as grinding, flotation and induration.

Jan 1, 2000

By G. Wonnacott

A model for simulation of gravity regrinding circuits is presented. The model can predict "secondary" density distribution data from a series of "primary" grind/density distribution tests. Thus middlings regrind requirements can be predicted from primary grind data. Traditional methods of regrind design involve lengthy and tedious tests programmes. The model presented herein can considerably reduce the quantity of testwork required for regrind design. The model can also be used to design primary gravity grinding circuits. A parameter estimation scheme and experimental data validating the model are presented.

Jan 1, 1989