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By R. J. R. Cornelissen

The elimination of the incidence of silicosis in employees in industries such as mining and pottery is an ongoing international initiative. After many decades of industrial activity in these industries and many dollars spent on preventative measures, silicosis is still occurring. The exposure-prevention measures taken so far have certainly improved the working environment dust concentrations; however, the illness is still regularly diagnosed in workers. More funding is needed for interventions to improve working conditions. Many aspects of dust prevention and suppression will be researched and exposure assessment methodologies and equipment will need to be reviewed for the purposes of improvements in effectiveness. This paper presents results from laboratory tests carried out on gravimetric sampling pumps and cyclones. It highlights the erratic flow produced by gravimetric pumps of three different manufacturers who claim their respective pumps are equipped with flow stabilisers. The standard BS EN 1232:1997 is used as a basis for the tests. A method, albeit impractical for fieldwork, is shown for the elimination of the pulsation in the flow. This method serves to prove the method and protocol used in this study. The pressure loss caused air-flow resistance of cyclones is measured. The air inlet aperture size of cyclones is measured. The large discrepancy in the two criteria between individual cyclones is shown. The paper concludes that all the pumps tested failed the prescribed limits of BS EN 1232:1997 regarding the pulsation of the gravimetric sampling flow. The difference in flow characteristics of the cyclones, together with the erratic flow produced by the pumps, throws into question the accuracy of the exposure assessments. It is suggested that substantial resources be channelled towards solving these flow problems in parallel with measures taken to reduce exposure. In principle, the accurate assessment of exposure and dust concentration levels is a prerequisite for effective management of the problem of silicosis.

Jan 1, 2009

[COUNCIL FOR 1991/92 President R.D. Beck President Elect JP. Hoffman Vice Presidents Senior Junior Dr H. Scott-Russell J.A. Cruise Immediate Past President Honorary Treasurer H.G. Mosenthal J.A. Cruise Members of Council Dr N.A. Barcza G.A. Brown B.R. Broekman Prof. RJ. Dippenaar B.R. Fleetwood* J.S. Freer P.R. Janisch P.J. Knottenbelt Dr J. Lurie R.P. Mohring *Co-opted K.C. Owen P.D.K. Robinson D.A.J. Ross-Watt P. Smith K.A. van Gessel DJ. van Niekerk P. van Schaardenburgh* CJ.C.J. van Vuuren* P.M.T. White]

Jan 1, 1992

By W. G. Diamond

Lightweight aggregates have become increasingly important to the construction industry. From 1953 to 1960, the quantity of the aggregates used in concrete block, precast and prestressed concrete, and monolithic structures increased about 92 percent. The present study was conducted in Bureau of Mines Area IV which encompasses the South-Central States of Arkansas, Kansas, Louisiana, Mississippi, Missouri, Oklahoma, and Texas. This is an administrative area and does not delimit a market area or imply an economic unit. Because of the increasing importance of metropolitan areas in evaluating economic growth, significant data showing relationships between growth of the metropolitan areas and the lightweight aggregate industry are included.

Jan 1, 1964

By K. D. Russ, A. J. Beer

Non-contact systems for measuring underground voids have used theodolites, reflective or non-reflective laser methods and sonar techniques. An effective but cheaper alternative is based on use of a Wild T1000 electronic theodolite coupled to a Leica Data DISTO and a Wild GRE3 data logger. The software used to process the theodolite data is a spreadsheet and macro combination, while Surpac, Datamine and AutoCAD modelling packages have been investigated for viewing the tunnel profiles. The main limitations were found to be blinding, when irregularities in the stope obstructed the line of sight, and the 30 m range of the Data DISTO model used in the study, although more powerful models are available. All three modelling packages proved suitable, with Surpac providing the best-quality printed images of the voids surveyed and AutoCad by far the cheapest alternative

Jun 21, 1905

By R. Rushforth

The surge of activity in the solar energy market, spurred by government incentives, has created new and more efficient solar technologies, but issues surrounding land- and water-use have backlogged the full-scale development of solar farms. This paper explores siting solar power plants on degraded or polluted lands, such as mine tailings impoundments. Historically, mining and has been integral to Arizona?s economy, but has dwindled in relevance due to urban pressures and environmental regulations. Currently, it is legal to site solar power plants on degraded or polluted lands, but the question remains whether the economics of this degraded lands solar development is more favorable than developing pristine land. Therefore, we explore economics of developing mine tailings impoundments at both the institutional and financial level. Methods of research for this paper were interviews with government regulators, environmental advocacy organizations, farmers, and mining company executives. Financial models using extant tax incentives show a positive net present value for the installation of solar power plants, even when accounting for the costs of land remediation.

Jan 1, 2011

By Sanford J. Douglas

This publication describes a study by the Federal Bureau of Mines of devices and methods used for testing and splicing 4,160-volt and 440-volt cables and for providing ground-fault protection for 440-volt circuits, as developed and used by the electrical staff of the Tecumseh coal mine, an open-pit operation at Boonville, Ind. The testing and ground-fault devices described should find ready application in other open-pit mines, and, with suitable modifications for voltages involved, in underground mining. The devices and testing methods are based on sound engineering principles and are time-tested and economically feasible, Four devices are used: A high-voltage tester, and a low-voltage high- current tester, both for testing 4,160-volt cables; a tester for 440-volt cables; and, electronic ground-fault protective device for 440-volt cable circuits. All the cable testers and the grounding device were designed and built at the mine from standard parts. They are inexpensive, dependable, and job tested, An attempt has been made here to describe them in enough detail so that interested persons can assemble duplicate units.

Jan 1, 1960

By L. J. Health

Synthetic rock with predictable porosity and permeability has been Prepared from mixtures of sand, cement and water. Three series of mixes were investigated primarily for the relation between porosity and permeability for certain grain sizes and proportions. Synthetic rock prepared of 65 per cent large grains, 27 per cent small grains and 8 per cent Portland cement, gave measurable results ranging in porosity from 22.5 to 40 per cent and in permeability from 0.1 darcies to 6 darcies. This variation in porosity and permeability was caused by varying the amount of blending water. Drainage-cycle relative permeability characteristics of the synthetic rock were similar to those of natural reservoir rock. INTRODUCTION The fundamental behavior characteristics of fluids flowing through porous media have been described in the literature. Practical application of these flow characteristics to field conditions is too complicated except where assumptions are overly simplified. The use of dimensionally scaled models to simulate oil reservoirs has been described in the literature. 1-3 These and other papers have presented the theoretical and experimental justification for model design. Others have presented elements of model construction and their operation. In most investigations the porous media have consisted of either u ncon soli da ted sand, glass beads, broken glass or plastic-impregnated granular substances—materials in which the flow behavior is not identical to that in natural reservoir rock. The relative permeability curves for unconsoli-dated sands differ from those for consolidated sandstone. The effect of saturation history on relative permeability measurements is discussed by Geffen, et a1.4 Wyga15 has shown quite conclusively that a process of artificial cementation can be used to render un consolidated packs into synthetic sandstones having properties similar to those of natural rock. Many theoretical and experimental studies have been made in attempts to determine the structure and properties of unconsolidated sand, the most notable being by Naar and Wygal.6 Others have theorized and experimented with the fundamental characteristics of reservoir rocks. This study was conducted to determine if some general relationship could be established between the size of sand grains and the porosity and permeability in consolidated binary packs. This paper presents the results obtained by changing some of the factors which affect the porosity and permeability of synthetically prepared sandstone. In addition, drainage relative permeability curves are presented. EXPERIMENTAL PROCEDURE Mixtures of Portland cement with water and aggregate generally are designed to have certain characteristics, but essentially all are planned to be impervious to water or other liquids. Synthetic sandstone simulating oil reservoir rock, however, must be designed to have a given permeability (sometimes several darcies), a porosity which is primarily the effective porosity but quantitatively similar to natural rock, and other characteristics comparable to reservoir rock, such as wettability, pore geometry, tortuosity, etc. Unconsolidated ternary mixtures of spheres gave both a theoretically computed and an experimentally observed minimum porosity of about 25 per cent.7 By using a particle-distribution system, one-size particle packs had reproducible porosities in the reproducible range of 35 to 37 per cent.6 For model reservoir studies of the prototype system, a synthetic rock having a porosity of 25 per cent or less and a permeability of 2 darcies was required. The rock had to be uniform and competent enough to handle. Synthetic sandstone cores were prepared utilizing the technique developed by Wygal.5 Some slight variations in the procedure were incorporated. The sand was sieved through U. S. Standard sieves. A 18-20 sand denotes that the sand passed the Number

Jan 1, 1966

By George H. Willis

In the second half of the nineteenth century, bimetallism progressively replaced by gold standard. After World War I and 1931-33 depression, gold mainly reserved for official international transactions and internal use restricted. Changes since 1971 have shrunk official international use of gold. International payments deficits and surpluses now financed by private and official credit, rarely by gold. Historical review covers evolution of: (1) internal and external private use, (2) internal official use, (3) external official use, (4) role in IMF and (5) use as unit of account.

Jan 1, 1978

By P. van Meurs, C. van der Poel

From observations of the linear displacement of oil by water from a porous medium as visualized in transparent models, new insight into the mechanism of vircous fingering, as occurring in the case of unfavorable oil-water viscosity ratios, has been obtained. A mathematical description of the observed phenomena leads to formulas. expressing both oil production and pressure drop across the formation as a func-tion of cumulative water injection with the oil-water viscosity ratio as a parameter. Theoretical results are compared with those obtained from scaled laboratory experiments in sand-filled rubes in which water was injected at the one end and production was obtained from the other end. In the second part of the paper the same principles are used to calculate a more realistic production scheme in which production of oil and water is obtained from wells regularly distributed over the field. Results show satisfactory agreement with production data of an actual oil field. Application of the theory is extremely simple as only a limited number of readily available parameters have to be known and results are presented in an analytical form. INTRODUCTION When oil is displaced from a porous medium by water having a viscosity lower than the oil. the oil-water interface is essentially unstable and has the tendency to break up into what are called "fingers" or "streamers". This Viscous fingering has been noted before by Engelberts and Klinkenberg' and has recently been demonstrated in transparent models by van Meurs-. It is highly questionable whether it is at all possible to perform relative permeability measurements In the laboratory reproducing the same distribution of water and oil in the cores as Present in practice. Therefore, we based our descriptive theory on an idealized model which was "tailored" to the fingering mechanism as observed in transparent models under scaled conditions. This approach was the more attractive, as a highly simplified model had already yielded an adequate description of the process. Though we are aware our theoretical approach can be extended in several ways, it is given here in its simplest form to explain the fundamental principles and to avoid complicated formulas. SIMPLEST CASE OF A LINEAR DRIVE Observations and Theoretical Model In Fig. 1 a series of photographs shows how water penetrates into a formation saturated with an oil which is considerably more viscous than the water. The technique for obtaining these photographs, using transparent models, has already been described?. The fingers can be clearly observed and are seen to be mainly parallel to the flow direction. Note that the contours of these fingers are not smooth but show protrusions of water enclosing oil pockets.

By A. A. Debrah

Artisanal and small-scale mining (ASM) plays a fundamental role in the national and local economies of resource-rich countries in Africa. As such, more effort must be geared towards fostering this type of economic activity to sustain livelihoods in rural communities. Across Africa, efforts to operationalize ASM based on a sustainable development framework have been quite tedious and often ineffective. This is because most of these frameworks lacked context and an understanding of the continuum from the artisanal through small-scale and up to the junior miner, grouped under the general term ?ASM?. Driven by the need to contextualize some of the definitional issues in this niche sector, and gain a clearer understanding of their peculiar challenges, this paper aims to contribute to the debate on ASM by considering two of Africa?s resource-rich countries ? Ghana and South Africa. Since South Africa has made greater inroads in protecting the interests of small-scale miners, we thus draw comparisons from both countries? approach to ASM, outline the lessons learnt, and provide recommendations regarding the ways forward.

Jan 1, 2014

By Patrice Favreau, R. F. Ph. D. Professor Emeritus Favreau

After Nobel invented dynamite, blasts were carried out by trial and error, without the use of equations based on the fundamental principles of Chemistry and Physics, although everyone accepted that shock waves were involved; but no equations were available to calculate their intensity. Around 1950 however, M.A. Cook proposed a procedure to calculate the thermochemistry of an explosive, and thus evaluate theenergy released during the explosion of a fully confined explosive. Some blasters then began to use theEnergy Factor; the latter, however, does not subdivide the energy into its three kinds of activities necessaryfor a successful blast, as demonstrated in 1968 by reference 2, namely i) the shock wave which weakensthe rock; ii) the stress field SS which fully fragments the rock; and iii) the release of the stress SS whichcauses the fully fragmented rock to burst out with the velocity necessary to move the rock into the muckpile. The article explains that the way to achieve a successful blast is by insuring that the explosive energy divides properly into the weakening action of the shock wave which is necessary to prevent large collar blocks and toe, and into adequate stress field intensity SS which is necessary to obtain good fragmentation size distribution at the crusher, as well as adequate burst out rock movement to achieve easy mucking.

By Donald R. Alvic

For electric utilities serving the aluminum smelter industry in the United States, sulfur oxide (SOx) abatement legislation could bring about increases in the costs of generating electricity. This paper documents the method and assumptions used in estimating these increases, and the contains the results of the estimation. 1.2 SMELTER INFORMATION The smelters used in this study were identified by the Bureau of Mines (BOM) and are listed in Table 1.1. Also included in Table 1.1 are the electric utilities that serve these smelters. Compliance costs were estimated for these utilities. Some of the utilities are unique in the way that the information is handled or in the way the utility is operated; these are discussed below. 1.2.1 Big Rivers and Associated Co-ops, Data for Big Rivers and Associated Co-ops were gathered by George Mason University (GMU) students for BON and are included in this study.

Jan 1, 1988

By Bruce Rock

A continuous mining machine was redesigned for the installation of an integrated illumination system. The illumination system was designed by first calculating the theoretical number of luminaires required to meet the Federal Illumination Standards. Luminaires initially were placed using isointensity diagrams. A darkroom was used for "fine tuning" and demonstrating that the system met the illumination requirements. The luminaire mounts were installed on a machine underground. The performance of this illumination system was monitored in the working environment of an operating coal mine. Design changes were made as necessary during this evaluation period to improve the system.

Jan 1, 1979

This report is the 26th in a series summarizing Bureau of Mines research and technologic work on coal and related investigations and the 8th of these reports to be issued on a calendar-year basis.1 It reviews briefly work in progress during 1961, and it provides references to publications by Bureau personnel during 1961 and also to a few older papers that were not cited in prior reports of this series. Details about some of the researches mentioned may be obtained by referring to the publications cited in the footnotes or in the further list in the Bibliography; other phases of work are reported here for the first time and will be covered in more detail by later publications.

Jan 1, 1963

By Carl Fisher

A microseismic roof fall warning system was field tested in Western and Eastern coal mines in the United States to better define the capabilities and limitations of the microseismic method in predicting roof fall. Microseismic event and energy type data were obtained and documented for twenty-three coal mine roof falls, Field test results indicate that both the microseismic event and energy methods, as applied in this development effort, have a high probability for successful application in a commercially practical roof fall warning system. Based on the results and experience obtained during field testing, a commercial prototype microseismic roof fall warning system was designed and constructed. Although it was the intent of the program to field test the commercial prototype system, delays in equipment fabrication and contract time limitations did not permit field testing.

Jan 1, 1980

By Q. J. Browne, M. A. Miller

Silver Bell produces about 22,000T of fine copper annually from low-grade chalcocite and oxidized copper ore that is recovered by sulfuric acid leaching and SX-EW processing. The current mineable reserves are 146 million short tons averaging 0.39% Cu, at a 0.15% cutoff. Silver Bell utilizes two types of mining methods to develop the low-grade reserves: (1) a conventional blast, load and haul method for run-of-mine leach ore, and (2) rubblization of material on the margins of existing pits. Rubble leach ore is blasted, terraced with a bulldozer, and leached in place. Mining and/or rubble leaching is currently active in four separate pits. Laramide-age intrusive rocks host porphyry copper mineralization at Silver Bell. Quartz monzonite porphyry dikes and stocks, mafic-poor equigranular granite (alaskite), and sub-volcanic dacite porphyry are the predominant host rocks. Most of the ore currently mined comes from near-horizontal enrichment zones containing veinlets and disseminated grains of pyrite and chalcopyrite rimmed by chalcocite. Conversion from a milling operation to a leach only operation allowed for a much lower cutoff grade than was historically used at Silver Bell. Mine geologists were able to increase copper resources by drilling exploration targets that were previously interpreted to provide lower-grade mineralization below cutoff-grade for milling. Geologic parameters that effect the distribution of rubble and mineable leach ore include: ore grade and thickness, variable alteration styles in intrusive host rocks that affect fragmentation during blasting, acid consuming carbonate wallrocks (reactive skarn) which influence leach solution pH, solution flow paths and drainage, presence of leachable oxide mineralization in non-reactive skarn, and depth to hypogene mineralization which is currently uneconomic. Geologic parameters are used to predict rubble bench limits, vary blast hole spacing for consistent fragmentation, and correct errors in mineral zone classification based solely on blast hole assays. An expansion-drilling program has identified approximately 150 million tons of new leachable copper resources with an average grade of 0.35% Cu.

Jan 1, 2002

By E. Sharifi

Advanced Process Control (APC) has been one of the most beneficial tools in the past decades available to minerals processing industry. Low capital cost together with significant improvements in process optimization have made APC an attractive investment option for nearly all mineral processing units. During economic downturns, importance of process optimization becomes even more relevant as metal producers tend to target de-bottlenecking and process efficiency improvements rather than large-scale capacity upgrades. APC project clearly has a lot of potential to improve process performance but there are also some pitfalls to be identified and avoided in order to achieve a desired outcome. Above all, APC project implementation is collaboration between the system vendor and user. Targets for the optimization must be agreed together with the customer and process performance must be defined before and after the optimization project. Most importantly, performance of the process must be monitored on a continuous basis during and after the project and potentially improved further. This paper discusses Outotec’s experiences from various concentrator optimization projects. Some examples are discussed in more details; however, the main target is to present general guidelines enabling a successful APC project implementation.

Jan 1, 2014

Removal of Dilute Toxic Anions in Wastewater Using Aluminum Hydroxides Co-Precipitation Method

Sep 13, 2010

Entry of personnel under a vertical raise bored hole is not standard practice in Australia. Where access is required below a rise, mining operations must be confident that they understand the capacity of the ground control specified and installed. Physical modelling was conducted on Callie mine to evaluate the performance of 5 mm steel wire weldmesh secured to the base of a vertical raise bored hole of 1.4 m diameter. Joint orientation data was used with Unwedge to calculate a series of potential wedges likely to form within the rise. The mass of the most likely wedges were then replicated by collecting rocks in 5 kg increments (¦10 per cent), which were allowed to freefall onto installed mesh at the base of a 40 m vertical rise. The results indicate that two sheets of mesh can retain a freefalling rock of at least 20 kg mass although rupture of strands can result. This paper outlines the test conditions, expected results based on theoretical calculations and actual outcomes of the testing.

Nov 25, 2010

By David F. Gearhart

The Burrell Can1 is a thin, steel, tubular shell filled with aerated concrete that is used as a roof support in coal mines. The Can height is always shorter than the mining entry, so it is capped with wooden timbers and wedges when it is installed. This combination of the Can and the wooden header is a standing support system that is designed to yield in a controlled manner and exhibit a constant yield, or elastic-plastic behavior. The Burrell Can is capable of withstanding 20 in or more of vertical convergence and 15 in or more of horizontal displacement. Because of this exceptional ability to sustain load through extended convergence and displacement, it is one of the most robust standing supports in use today. The National Institute for Occupational Safety and Health (NIOSH) conducted testing on seventeen Burrell Cans in 1995, during development of the support where the ratio of the height to the diameter, or the aspect ratio, was between 2:1 and 4:1. Based on the results of that testing, it was suggested that the standard aspect ratio of the Can be less than 5:1. This suggestion is intended to preserve the overall stability of the Can, which will help to maintain the initial stiffness and prevent load shedding. Recently, the necessity of the aspect ratio has been questioned, and this issue will be addressed in this paper. Since the initial development and introduction, more than 130 tests of the Can have been conducted at the NIOSH Mine Roof Simulator (MRS), and 25 of those specimens had aspect ratios greater than 5:1. The 18-in-diameter by 10-ft-tall specimens had the largest aspect ratio, 6.67:1.However, the aspect ratio is not the only parameter that affects the performance characteristics of the Can. Multiple factors, such as the use of different wood species, the use of different header or footer configurations, and the use of pedestals, as well as biaxial loading conditions can also decrease the stiffness and capacity of the Can. Data from full-scale tests that include these other factors are analyzed to show that the initial stiffness is primarily affected by the roof and floor contact configurations. Furthermore, load shedding is more likely to occur or begin earlier when the aspect ratio is greater than 5:1 and one or more of the other factors are present.

Jan 1, 2012