Search Documents

By Robert J. Greaves

High-resolution seismic reflection profiling can be used to evaluate detailed struc¬tural and stratigraphic features of coal pros¬pects. Since most coal prospects are relatively shallow (less than six hundred meters deep), the vertical and lateral resolution of seismic data can be significantly improved by high sampling rates in space and time. The case study present¬ed shows the effective use of seismic data in evaluation of the Wyodak coal at a prospective coal gasification site. The data were used to map the detailed structure and thickness of the coal and to search for lateral discontinuities, such as pinchouts and. faults. An important find was a paleochannel cutting across the base of the coal seam, which was later confirmed by drilling.

Jan 1, 1983

By G. Kraemer, J. A. Le Gac, P. R. ZETTWOOG

I. INTRODUCTION During the course of our activities in assisting mining companies, we have had access to the monitoring results for personnel from a large number of uranium mines. The results differ greatly from one mine to another. One of our objectives has been to discover the origin of these differences. It is evident that they are largely due to variations in the geological context, to mining methods, and to the organization of the work ; but we also found that the rigor with which measures are implemented to prevent the personnel from being exposed to radiations is also a cause. In order to advise mining operators effectively, we have asked ourselves the following question Given the dosimetric results of a mining site, how can it be known - if occupational exposure has been reduced to the lowest possible level (dose optimization principle recommended by the ICRP) ; - if the exposures were justified, which would not necessarily be the case following a questionable choice of the mining method, for instance, or a lack of efficiency in the maintenance and repairs of ventilation apparatus or even an excess of radiation protection. It is necessary to establish some criteria, while taking into consideration the specific conditions for each mine, in order to determine whether a mining company is adequately implementing radiation protection procedures. This need led us to attempt a modelization of the occupational exposures of uranium miners ; the preliminary phase is presented here. Although voluntarily still very basic, this model makes it possible to demonstrate the role of certain dynamic or passive variables. Moreover, the model presents the concept of specific irradiation of a mining site equal to the collective dose received per ton of uranium metal supplied to the uranium mill. The specific irradiation can therefore be used to indicate the effectiveness of radiation protection procedures at a given mining site. This model can be used for - previsional exposure studies based on the use of data gathered at each site, making it possible to compare various work methods and to determine prevention means ; - qualification of "radiation protection" procedures at a mining site ; - detection of unjustified exposures ; - research of ways to reduce inevitable exposures. 2. DETRIMENT TO BE ASSOCIATED WITH A GIVEN EXPOSURE DISTRIBUTION Respecting exposure limits ensures that delayed stochastic effects are the only health risks to workers. If the hypothesis of linearity in the dose-effect relationship is applied, the detriment to a group of workers is proportional to the sum of exposure for all the workers, or the collective exposure usually expressed as man x rem. On this point the linearity of effects hypothesis makes it possible to consider that two different standard deviation distributions having the same mean value are equivalent. It would be possible, then, to reduce the standard deviation by changing the distribution of workers at the various working places without changing the mean exposure value. In other words, without taking into consideration the practical implications, individual limits can be respected by rotating the personnel or by reducing the individual working period which would be compensated by increasing the number of workers. The collective dose would remain the same, which would justify the use of the concept of collective exposure. 3. "RADIATION PROTECTION" QUALITY INDEX AT VARIOUS MINING SITES Each mining site is responsible for its own collective dose, but it is also responsible for producing a certain amount of uranium metal in the ore sent to the uranium mill. These two quantities must be brought together in order to establish the "radiation protection" quality index of a mining site. This quality index, called-specific irradiation (Ir) is expressed in rem.ton -1 for external irradiation, in mJoule.ton-1 for inhaled [a]-energy, and in Ci.ton -1 for inhaled radon *. The specific irradiation represents the health hazard which must be associated to the extraction of one ton of uranium metal. Figures la and lb present a system of coordinates for which the axis of the abscisses is graduated in tons of U metal and the axis of the ordinates is graduated in units of collective exposures. In the EEC, the regulation is based on the measurement of the amounts of radon 222 inhaled.

Jan 1, 1981

By M. P. McArthur

General mining practices at W. R. Grace's Bonny Lake mine are much the same as those used in open pit phosphate mines in Central Florida, except for the difference in the depth of the overburden which introduces many variations, From 1945 to 1961 the mining at Bonny Lake has been from an area in which the overburden averages from 55 to 60 feet and in several locations exceeded 65 feet. The matrix thickness will average 15 to 18 feet for the areas mined. As you can see from the above depths a total hole depth will average from 70 to 75 feet.

Jan 1, 1962

By K. N. Han

Copper and nickel are extracted from their elemental state, complex sulfides, ores, and other materials such as scrap by leaching them with a solution containing halogen salts - bromine/bromide, and/or iodide/iodine, oxygen and sodium or potassium nitrate. This US patented process is extremely effective yielding 98% recovery in15 minutes for the treatment of chalcopyrite and pentlandite in an autoclave at a temperature of 100°C - 150°C.

Jan 1, 2003

By M. S. Klima, A. Simard, M. L. Turek

Laboratory testing was carried out to evaluate several devices for recovering clean coal from bituminous coal refuse material. The bulk of the testing focused on using a dense-medium cyclone to process -0.6-mm refuse material. A hindered-settling column and a spiral concentrator were also used to process nominal 1.2 x 0.15-mm material. Product yields and ash contents were obtained for all tests, while partition curves were generated for selected tests from which the characteristic performance parameters (relative density of separation and probable error) were determined. The results indicated that the dense-medium cyclone was capable of cleaning down to 0.037 mm, while the other devices were effective to 0.15 mm. Keywords: Coal recovery, Coal refuse, Dense-medium cyclone, Hindered settling, Spiral concentration

Jan 1, 2003

By J. S. Lindsey, E. E. Jones

Dow Chemical Co.'s research in lignite gasification has required that the fuel be upgraded in terms of ash loading and the slagging character of the residual ash. Lignite beneficiation has been shown to substantially reduce the total ash loading and, in some cases, causes very significant reductions in slag viscosity. In support of this work, a slag viscometer was constructed and the viscous flow properties of lignite ash were run as a function of temperature and composition. The flow as a function of temperature was shown to be predictable from the chemical composition.

Jan 1, 1988

By A. B. Szwilski

The mineability and coal processing costs are influenced largely by the structural and physical properties of the coal seam. The mining process involves coal cutting, pillar support, crushing, and floating. A correlation between the rank, ash content, and coal strength/stiffness is discussed. The coefficient of variability of rebound tests on the face of various coal seams are compared with those of laboratory compressive strength tests by other investigators.

Jan 1, 1988

By Karl P. Norrena, Clayton V. Deutsch

Ore and waste cannot always be visually separated. The distinction between ore and waste may need to be made on the basis of blasthole sampling. Hand drawn dig limits or computer-generated contour lines do not account for uncertainty, economics or equipment. Geometric methods for interpreting grade information such as the polygonal or triangulation methods share the same limitations as contouring. Geostatistical techniques exist for the realistic modeling of grade variations and uncertainty. Decision analysis techniques exist for the binary classification of ore, and waste blocks in the presence of this uncertainty. Block-by-block classification is not enough; mining equipment cannot exercise free selection of blocks. There is a need for procedures to determine optimal dig limits that account for (1) the uncertainty in the grades, (2) the economics of risk-qualified decision-making, and (3) the ability of the mining equipment to dig to specific limits. This paper presents a procedure for optimal determination of dig limits that account for these constraints. Simulated annealing (SA) is used with modest computational requirements because the number of variables is relatively small. The solution of the optimization problem is dig limits that maximize profit under multiple constraints. The method is illustrated with different constraints and tested against hand drawn dig limits in a "Dig Limit Challenge," which illustrates the efficacy of the new method.

Jan 1, 2002

Building aggregates, basic materials for the construction industry, must be produced according to socio-economic and environmental sustainability principles, i.e. the three fundamental components of Sustainable Development. On this subject, an introductory discussion about the interpretation of these concepts in the field of mineral production and construction industry is first presented. As for the socio-economic aspect, aggregates are then illustrated as being essential resources for the development of the society, underlying that it is possible to understand their fundamental socio-economic role only through the analysis of the whole product life cycle, from production to end use and beyond. The same has to be done on the environmental side to assess the environmental impacts of aggregates: one should look for, not in the quarry phase only, but also in all the downstream activities of the construction process, including the use phase and beyond. Based on this approach, in the second part of the paper, the results of some investigations focused on eco-profiles of building aggregates, gathered through the application of LCA methodology are presented and discussed. In such a context, strengths and weaknesses of LCA indicators will be discussed, as well.

Jan 1, 2007

By H. P. Schlanger, L. Paterson, B. H. G. Brady, B. E. Hobbs

A novel principle for a waste repository, based on a backfilled thermosyphon as the functional unit, is proposed. Such a unit reduces temperatures and temperature gradients in the vicinity of a waste package and in the repository near field, reducing leach rates from packages and thermomechanical disturbance of the rock mass. Preliminary analyses confirm the mode of performance of the system, and reveal some interesting features of material transport and sealing in backfill and rock fissures. The thermosyphon combines attractively with the prospect of developing a near-field geochemical trap with chemical specificity for radionuclides. It is proposed that a thermosyphon repository may provide superior performance of engineered and natural barriers compared with conventional designs. The achievement of the ability to predict accurately the performance of the thermosyphon, relative to other isolation schemes, will represent a benchmark in the understanding of the absolute performance of any repository.

Jan 1, 1986

By C. H. Bucknam

An interlaboratory testing program was undertaken in support of an ASTM standardization program for simultaneous combustion-infrared analysis for carbon and sulfur in ores and related materials. Statistical analysis results from the study are used to generate the within-laboratory and between-laboratory precision data needed for standardization of the methods. The interlaboratory precision statistics are also interpreted to estimate the uncertainty in calculation of net carbonate value classifications using a simplified quantitative risk analysis technique.

Jan 1, 1998

By J. Gallagher

Henderson Mine has been transporting molybdenum ore using a rail haulage system for the past 21 years. Due to the age of this system, limited performance, and obsolescence, a capital investment decision was imminent. Henderson used this opportunity to evaluate other transportation methods and continuously improve their mining practices. These efforts resulted in a new mine plan for Henderson, which ensures that Henderson will continue to supply high quality molybdenum into the 21st century. This paper will discuss the dramatic changes taking place at the Henderson Mine as a new production level is mined. These changes include the installation of an underground crushing, conveying, and truck haulage system, as well as increasing the scale of the panel caving process. Each of these topics will be discussed, as will their rock mechanics and material flow implications.

Jan 1, 1998

By M. Li, J. K. Thompson, A. S. Azman

"Powerful mining systems typically generate high-level noise that can damage the hearing ability of miners. Engineering noise controls are the most desirable and effective control for overexposure to noise. However, the effects of these noise controls on the actual hearing status of workers are not easily measured. A tool that can provide guidance in assigning workers to jobs based on the noise levels to which they will be exposed is highly desirable. Therefore, the Office of Mine Safety and Health Research (OMSHR) of the National Institute for Occupational Safety and Health (NIOSH) developed a useful tool to estimate the hearing loss due to occupational noise exposure in a systematic way and evaluate the effectiveness of developed engineering controls. This computer program is based on the ISO 1999 standard and can be used to estimate the loss of hearing ability caused by occupational noise exposures. In this paper, the functionalities of this software are discussed and several case studies related to mining machinery are presented to demonstrate the functionalities of this software. INTRODUCTIONPeople regularly exposed to noise can develop hearing loss at different levels of severity depending on a number of factors. The resultant hearing loss can affect one’s ability to understand speech, learning, acoustic signal perception, or appreciation of music. Hearing loss caused by overexposure to noise has long been recognized in literature. However, it still does not get serious attention by those working in noisy environments because the loss of hearing ability is a gradual process and workers are often unaware until the damage becomes an apparent problem. In the United States, occupational hearing loss is one of the most common work-related illnesses. Depending on the definition of exposure and impairment, in 2012 the National Institute for Occupational Safety and Health (NIOSH) estimated that there are between 5 and 30 million workers in the U.S. who are exposed to noise levels at work that put them at risk of hearing loss.4 In the mining industry, noise-induced hearing loss (NIHL) is particularly severe due to the fact that heavy-duty machinery is widely used to improve production efficiency, and this machinery can generate much higher-level noise than the permissible level defined by regulation. As a result, the mining sector has the highest prevalence of hazardous workplace with high noise exposures (76%) among all industrial sectors."

Jan 1, 2015

By L. R. Freitas, A. K. Resende, J. A. Oliveria, K. L. Gonçalves, L. F. D’Assumpção, L. R. Lage, J. D. Neto, F. Viveiros

Pará Pigmentos S.A. (PPSA) is an association between the Brazilian companies CVRD and CADAM, Mitsubishi Corporation of Japan, and the IFC (World Bank) created in 1992 in order to recover kaolin from Rio Capim deposit, northern Brazil. Commercial production at PPSA started in August 1996 using a process comprising mining and beneficiation at the mine site, pumping through a pipeline and drying/loading at the port site on the Amazon river estuary. Presently, all PPSA production is concentrated on 82% <2um, high-brightness coating clay shipped in bulk. In this paper, a detailed description of the development of PPSA beneficiation process is presented. The results of laboratory and pilot plant studies under- taken to develop alternative grades of clay, such as delaminated and calcined kaolins, are also discussed.

Jan 1, 1998

By S. B. Patton, T. Novak

To fully utilize a ventilation simulator as a planning and production tool, the network database must keep pace with mining progress. By using AutoCAD&apos;s™ attribute-definition function, the branch data and node coordinates can be stored as part of the branch-diagram file and updated with the drawing. Attributes are drawing entities that contain text which can he extracted in a standard spreadsheet format or as an ASCII text file. The data can be subsequently loaded into a ventilation simulator. This paper presents the methodology for using AutoCAD&apos;s™ attribute feature in a ventilation simulation format.

Jan 1, 1995

By Alfred Jr. Petrick

Modelling of cash flows and calculation of net present value of rate of return over the expected life of a mine/processing unit continues to be the accepted basis for mineral investment decision-making. The computer and spreadsheet programs have greatly improved ability to perform sensitivity and risk analysis, hence our ability to deal with key analytical problems. These problems of cash flow analysis result from the necessity of forecasting an uncertain and risky future. Cash flow models begin with the critical assumption of a "design basis", then integrate all of the variables relevant to the investment decision including forecasts of price, cost, taxation, financial conditions, and company strategy. Alternate "scenarios" portray possible future outcome of the investment decision. The potential for straying from reality is enormous. The computer has eliminated the time consuming hand calculations from the cash flow analysis, but the analyst still struggles with the risk of trying to predict "how the project will really turn out".

Jan 1, 1991

By W. A. Heitbrink, M. Schmitz, J. A. Organiscak, A. B. Cecala, E. Ahrenholtz

Mobile excavation equipment operators at surface mines generally have the highest exposure to airborne respirable silica dust. Operator cabs on newer equipment are usually enclosed and equipped with heating and air conditioning systems. Many newer cabs are also equipped with air filtration systems. However, some newer cabs and many older cabs have either inefficient or no air filtration systems. The U. S. surface mining industry is still populated with older equipment and many of these have cabs that provide little or no respirable silica dust protection. Collaborative field studies were conducted as part of a partnership involving NIOSH, Clean Air Filter®, Red Dot, MSHA, and several mine operators to demonstrate that effective dust protection can be provided by these cabs at a nominal cost to mine operators. This effort encompassed adding an external make-up air fan and filter system to a retrofitted roof-mounted heating and air conditioning system in three older equipment cabs, and attempting to seal the cab enclosures to achieve interior cab pressurization. Abetter than 90 percent dust reduction was measured inside two of the three enclosed equipment cabs. It was possible to achieve positive cab pressurization inside these two cabs. A less significant dust reduction was measured inside the third cab, where positive pressurization was not achieved. These field studies demonstrate the key elements needed to improve enclosed cab dust protection in a cost-effective manner.

Jan 1, 2003

By Anthony D. Hammond

INTRODUCTION A two-dimensional approach for modeling narrow-vein deposits using the TECHBASE® software was implemented at Sunshine Mining for its use in the evaluation of mineral properties. This 2-D approach prevents the overestimation of high-grade tons typically associated with the use of fixed 3-D blocks and reduces the size of the model in computer memory. The method consists of constructing a two-dimensional model oriented along the average plane of the mineralized structure. This approach works well for single, multiple and intersecting veins with the condition that each vein is roughly planar with variation in dip or strike less than 30" in order to maintain a reasonable resolution in the process of projecting data onto a plane (Figure 1). Also, a precise identification of the hanging-wall and foot-wall location is critical in ensuring an accurate representation of the vein. By using various modeling techniques, the two-dimensional model estimates metal content, thickness, tonnage, economic and dilution parameters which will be ultimately used in the identification of minable reserves. The following is a generic description of the steps involved in modeling a steeply dipping vein. DATA ENTRY A typical project database consists of drillhole coordinates, survey information, assay data and any other quantitative or qualitative data. This database can be created inside the software or imported from any spreadsheet. TECHBASE® utilizes the concept of "fields" and "records" (columns and rows) for storing data. The use of "calculated fields" enables the user to expand on the manipulation of the database with minimum memory requirements. Another important feature of TECHBASE® is the ability to replicate the structure and format of the "tables" for its use in another project and the capability of running a series of repetitive tasks by means of batch and "runlog" files.

Jan 1, 1998

By S. L. Huang, J. D. Rockaway, N. B. Aughenbaugh

Shale has long been recognized for its tendency to swell when exposed to the atmosphere. Interaction of moisture with exposed shale strata can cause serious ground stabi1ity problems, since the initial strength of a shale is reduced if the material is sensitive to moisture variations. In this paper, the authors present a classification system to estimate the response of swelling generated within shales. This characterization of the swelling potential is based upon plasticity, susceptibility to moisture, mineralogical constituents of clay size particles, and fabric. Use of this classification system in conjunction with other existing rock properties tests will provide data for more rational engineering design.

Jan 1, 1986

By Spencer R. Titley

Nearly three decades of intense research, corresponding with a period of unparalleled discovery and the advent of scientific advances and hypotheses of ore formation, has resulted in a great body process-focused research concerning how ore deposits form. The development of process models and their application has proceeded more or less in step. Discoveries have been made in mineralized regions such as provinces and districts but generally without a comparably developed understanding of why provinces and ore bodies exist and, except in general terms, where ore deposits are within districts and regions. The process of discovery is still referred to as search and exploration budgets are heavily weighted toward exploration drilling.

Jan 1, 1995