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By M. M. Gadde

Recent regulatory changes in the United States make it mandatory to conduct structural analysis of coal mine seals used to isolate abandoned workings from active mining areas. Different loading criteria are available for seal design depending on whether gob composition is actively monitored and maintained or not and whether the gob conditions lead to deflagration or detonation type loading. Since the loads involved in seal designs are dynamic in nature, the structural analysis must be made using dynamic stress analysis techniques. However, because of the significant complexities involved in conducting dynamic analyses, some designers use approximate simplified techniques to address the design problem. In this paper two such simplified methods are critically evaluated for their suitability to design coal mine seals. The benefits and limitations of the simplified methods are also outlined. Some comparisons are made to show the differences between sophisticated three dimensional dynamic analyses and the simplified methods and to delineate the problems associated with the latter approaches.

Jan 1, 2009

By David S. Bolin, Gary R. Peterson

INTRODUCTION In both the United States and Canada, a company making a public offering of securities must comply with regulations which have been promulgated by Federal and/or Provincial Legislatures. This paper focuses on the regulations pertaining to reserve reports required by the United States Securities and Exchange Commission (SEC). SEC RESERVE FILINGS Reserve reports made to the United States Securities and Exchange Commission are the only reserve reports which are directly regulated by the United States government. The requirements for SEC reserve reports are set forth in the filing forms as shown in Appendix A, from Item 17A of SEC Form S-18. These reporting requirements, which are intended to protect the investing public from inaccurate or misleading claims, are primarily oriented to S-1 or other filings for new stock issues but must also be followed for annual 10K reports which must be filed annually by U.S. public corporations as part of the Corporate Annual Report. These undertakings require independent audits of reserves, mine designs, plant facilities and a general economic evaluation of the planned or existing operation as part of the backup documents for filing. An ore reserve is defined by the SEC as "That part of a mineral deposit which could be economically and legally extracted or produced at the time of the reserve determination". This definition is unchanged since it was last

Jan 1, 1988

By R. D. Herron

Mining coal under deep cover conditions is certainly the proper phrase to use in describing one of our newest operations. Located in the southwest corner of Virginia is this operation which is the Beatrice Mine of the Beatrice Pocahontas Company, a joint venture of Republic Steel Corporation and Island Creek Coal Company. The mine is working in the No. 3 Pocahontas seam in an assigned area of over 9500 acres containing over 60 million tons of recoverable, high quality, low volatile coal. The site of the mine opening was at Keen Mountain, Virginia, where the seam lay 1350 feet below the surface. This depth, greater than anything attempted thus far in the coal industry on this continent, would pose some problems, we felt, with which we had not previously had to contend.

Jan 1, 1968

By M. Ashraf Mahtab

In Louisiana salt mines a sudden erruption or outburst of salt and gas occurs when the heading face approaches a pressure pocket (altered salt with high pressure gas). The resulting cavity is semi-ellipsoidal, reaching lengths of 50m or more. Potential risks from the outbursts include loss of life and equipment. A gas outburst is initiated by "disking" of the salt in biaxial compression and propagates by spalling of the cavity walls and further disking. The outburst is terminated by a combination of dilatancy hardening, increase in stress along the cavity axis, and enlargement to boundaries of the pressure pocket.

Jan 1, 1982

By V. Dentoni

The paper deals with the assessment of the visual impact generated by surface mining and quarrying. Previous research works proved the applicability of an indirect method based on the elaboration of digital images through which the extent of the visible altered area and the chromatic contrast with the surrounding environment is calculated. The resulting level of visual impact allows an objective comparison among different cases as far as the evaluation procedure is univocally defined. The article illustrates the application of the method to a number of selected quarries located within the Sardinian territory; different issues are discussed such as the choice of the viewpoints from which the pictures are taken, the influence of the distance from the quarry to the selected viewpoints, the light condition and the orientation of the quarry faces. Moreover, the visual impact level obtained from pictures taken at the same time with five digital cameras are compared in order to evaluate the contribution on the overall uncertainty.

Jan 1, 2008

By K. S. Liddell

Ultra fine grinding is becoming increasingly used in the mining industry over recent years. The development of large-scale units for high volume grinding of low value materials and concentrates has opened up new areas of economical metal extraction. The ability of stirred vertical mills to produce very fine particles with high surface areas, is providing mine operators with novel extraction possibilities within gold concentrate regrind for Biox or leach feed, Activox autoclave feed preparation and lime slaking operations. The paper will review design, operational and maintenance aspects of ANI-Metprotech stirred vertical mills, comparing these to tower mills, horizontal bead mills and attrition mills.

Jan 1, 2001

By R. Y. Wan, J. D. Miller, P. L. Sibrell

Three different refractory carbonaceous gold ores from the Carlin operation in northeastern Nevada were investigated to characterize the effect of passivation treatments on the nature of the carbonaceous material. The carbonaceous material was chemically isolated from the ores and passivated residues, and examined by FTIR spectroscopy, elemental analysis, and gold adsorption capacity. The main component of the carbonaceous material in these ores was found to be a naturally occurring activated carbon-type compound. Hydro-carbons were detected on rare occasions, but no evidence was seen for humic acids. Ore samples were passivated by autoclaving, or by treatment with sodium hypochlorite or gaseous chlorine. In some of the passivation tests, a new peak was observed in the IR spectra of the isolated carbonaceous material, that was due to carbonyl functionalities. However, all of the passivation treatments tested decreased preg robbing significantly. This suggested that the appearance of the carbonyl peak was due to the severity of the conditions during passivation, rather than the method used.

Jan 1, 1990

By David K. Ingram

The objective of this U.S. Bureau of Mines investigation was to characterize overburden response due to longwall mining. Subsurface strata and surface deformations were monitored during the mining of two adjacent, 900 ft wide longwall panels in southeastern Ohio. The panels were separated by a five entry, four pillar system (about 350 ft wide). The overburden thickness in the study area ranged from 214 to 280 ft, and the extraction thickness averaged 70 in. To delineate the geology of the overburden, six coreholes were drilled along a profile line extending across the two longwall panels. Multi-point borehole extensometers (MPBX) with eight-anchors were installed in six boreholes to measure subsurface displacements. The MPBX units were continuously monitored using a data logger. During the mining of the first panel, displacement occurred in a radiating pattern beginning just above the extracted area in the center of the panel and extending upward and outward towards the surface and margins of the panel. Overburden deformation did not project over the gate road entries. During the mining of the second panel, the MPBX's showed almost simultaneous displacement, indicating that the overburden began to move as a whole unit. Again, overburden deformation was confined to the immediate panel area. At both panels, overburden movement began when the longwall face was approximately 55 ft beyond the line of MPBX boreholes. Moreover, all ground movement was complete when the longwall face was approximately 200 ft beyond the line of MPBX boreholes. This paper discusses the results of the study and identifies the characteristics of overburden deformation.

Jan 1, 1986

By M. J. Virnig, Marc Le Vier, Rong Yu Wan, Jan D. Miller

Although most gold production from primary resources is achieved by cyanidation, many research activities have focused on alternative processes using noncyanide lixiviants. Such research has been prompted by environmental concerns and problems associated with the processing of refractory gold ores. Numerous research projects have been conducted to search for a noncyanide hydrometallurgical process for gold extraction. In this paper, a technical review of gold recovery from noncyanide solutions is presented, and new results are reported. Gold recovery techniques that are considered include activated carbon adsorption, cementation, solvent extraction, ion exchange, and reduction-precipitation.

Jan 1, 1993

By I. Iwasaki

Precious metals are commonly believed to be recovered along with sulfide minerals in flotation, but a few neutron activation analyses showed that the recoveries of gold and silver were unexpectedly low. Recoveries of platinum group metals remained unresolved due to interferences in the analyses. Electron micro-probe, scanning electron microscope and scanning auger microprobe analyses have identified nickel arsenide minerals in the ore and confirmed a close association of platinum group metals with the arsenide minerals as minute inclusions. These results indicated a need for re-evaluation of flotation procedures which have so far ignored special problems related to arsenide minerals. The electrochemical and flotation behaviors of nickel arsenide and their implications to the flotation recovery of arsenide minerals from copper-nickel bearing Duluth gabbro are presented.

Jan 1, 1985

By R. J. Pruett, J. Yuan

Kaolin clays from five different commercial deposits in Georgia were studied to understand the variations of zeta potential and related fundamental properties. The results suggest that higher negative zeta potential is related to exchangeable or soluble calcium ions in the clays.

Jan 1, 1999

By James D. Bliss

Evaluation of data for three engineering variables-absorption, bulk specific gravity, and freeze-thaw durability (350 cycles)-was made for quarries in carbon- ate rocks in Oklahoma that supply aggregate. It was found that lower Paleozoic carbonate rocks (Cambrian through Devonian) are likely to make a better quality aggregate than upper Paleozoic (Mississippian to Permian) carbonate rocks. In addition, freeze-thaw durability can be forecast from absorption and is exemplary for lower Paleozoic carbonate rocks.

Jan 1, 1999

By G. Bloomsburg, R. E. Williams, S. D. Vincent

A modeling scheme is developed to simulate the hydrogeologic effects of mine design and development in unsaturated rock. Simulations are conducted using the UNSAT2 finite element computer program and hydrogeologic data from the site of a proposed mined-out waste repository at Yucca Mountain, NV. Results of the simulations are analyzed for: •variations in the direction of ground water flow and in the distribution of pressure head caused by the design of the mined out openings; and •mine design variables that affect the predicted rates of mine water inflow. Evaluating the hydrogeologic impacts of mine design and mine development in unsaturated rock is significant in several respects. Characterization of the preemplacement of wastes along the fastest path ground water flow system at the Yucca Mountain site has been a primary research effort. Ultimately, however, the degree to which waste isolation is achieved will depend largely on the post-mining hydrogeologic environment as altered by the mine design and on the radionuclide inventory and resulting heat effects of the repository. Therefore, an ongoing characterization of the proposed mined-out nuclear waste repository at Yucca Mountain, NV, is recommended. Modeling results indicate that: •mined out openings will affect the movement of ground water, both in rate and direction; •hydraulic effects of mine development depend on the hydrogeologic environment and on mine design geometry; •mine water inflow is possible in the unsaturated zone, even for mines developed in hydrogeologically homogeneous rocks; and •mine water inflow can occur at values of down ward flux that are appreciably less than the saturated hydraulic conductivity of the overlying rocks.

Jan 1, 1991

By Donna L. Boreck

Introduction Coal has been mined in the western United States since the mid-1800s. The resource is abundant in the West. Despite recent economic conditions, it remains an important part of the nation's energy warehouse. Many of the seams that comprise the western resource base are thick, some exceeding 61 m (200 ft). Multiple, closely-spaced seams or thick coals that split into two or more minable seams are also common. Historically, subsurface development recovered from less than 15% to 50% of these deposits (Matson and White, 1975). This resulted in a substantial loss of inplace reserve due to the limited height that could be mined using the available technology. In an effort to increase future recovery from such deposits, the US Bureau of Mines analyzed the potential for incorporating three thick-seam mining methods into western coal mines. These methods are high-face longwall, multislice longwall, and longwall caving. They were developed in Europe and are being used to mine thick coal seams in Europe and Asia. One aspect that will determine their success in the US is the geology of the individual deposit; namely, are the methods adaptable to the geologic conditions characteristic of western coal? This paper analyzes some of the geologic factors that would affect development of thick or closely-spaced seams using these mining methods. Occurrence of thick and closely-spaced seams Since mining conditions and methods differ around the world, a thick seam is often defined as a seam whose total thickness cannot be extracted using the available equipment. In the western US, the maximum extractable mining height is about 4.3 m (14 ft). For this research, a thick seam was defined as a minable seam 4.6 m (15 ft) thick or more. Since one of the seams is usually lost using standard mining methods, closely-spaced or split seams were also addressed. These were defined as two minable seams 1.5 m (5 ft) thick or more separated by 9 m (30 ft) of interburden. Thick or closely-spaced coal seams are common in the West. Their importance has not been documented due, in part, to the methods used to measure resources. In the past, all reserves greater than 1.1 m (42 in.) thick for bituminous seams and greater than 3 m (10 ft) thick for subbituminous seams were grouped together and were differentiated only by rank. Further differentiation by seam thickness or minability was not done. For this reason, reserve figures for thick or split seams are difficult to determine. By analyzing available published resource data, Ferm and Muthig (1982) addressed thick seam resources. They estimated a resource of 90 Gt (99 billion st) of coal (16% of the Western resource base) in seams 4.6 (15 ft) or greater at less than 610 m (2000 ft) overburden. Yet, a later study of Pierce and others (1982) on one thick seam deposit in the Powder River Basin estimated a resource of 103 Gt (113 billion st). Pierce (1986) reported that the overburden reached a maximum of 731 m (2400 ft). The resources in this single deposit exceeded the 90 Gt (99 billion st) total projected for the entire western US by 12.7 Gt (14 billion st). Due to such differences, this author chose to look at reported occurrences of thick or closely-spaced minable seams in place of resource figures, to verify the need to research thick seam mining in the West. An occurrence was defined as an isolated site where a thick seam or two or more closely-spaced seams were reported. The occurrences were derived from published material - mostly mine descriptions, measured sections, coal exploration logs, and oil and gas logs. Due to time constraints, the reserves associated with each occurrence were not determined. All data points were random. The analysis was limited to occurrences in Colorado, Wyoming, and Utah. Although source material available to the author was limited to general coal summa-

Jan 3, 1988

By C. H. Rawlins

Deep bed media filtration is used as a tertiary treatment step (after hydrocyclones and flotation cells) to remove fine oil droplets and solids from oilfield water before reinjection disposal or to remove particulate material from surface waters used for waterflood injection. Oil and solids injection requirements are typically <5 ppm concentration at <2 micron diameter. The preferred media for produced water filtration is walnut or pecan shell, however the use of this media has evolved by trial & error and the fundamental mechanisms that occur during separation and media cleaning have not been investigated. A project was initiated to fill in this knowledge gap by analyzing the physical, mechanical, chemical, and hydrodynamic properties of six types of granular filtration media (12/20 mesh size): garnet, silica, anthracite, pecan shell, English walnut shell, and black walnut shell. Comparison of bed packing, oil wetting, attrition resistance, particle strength, and fluidization has led to an understanding of the preferred filtration media for separation of fine oil droplets and solids.

Jan 1, 2010

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 1.2x0.15-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.

Jan 1, 2002

By D. P. Plute

The mechanization of the materials management function must contribute to the overall goal of optimization of profits. A computerized system contributes to the profitability of the company by saving more than it costs to operate. Design and implementation of the sys- tem must respond to the needs of users, the operating environment of the property, and must support the objectives of materials management. Three basic functions interact within the scope of materials management. They are inventory control, purchasing, and warehousing which have the following objectives: 1) Inventory control-to request materials in a timely manner and in quantities that provide the best level of support to users at the lowest cost. 2) Purchasing-to purchase requested materials and services at the required time and at the lowest cost. 3) Warehousing-to efficiently receive, store, and issue materials and to prepare accurate transaction documents for the activities. The development of the mechanized materials management system will require a plan and objective analysis by management and system users of system requirements. A typical plan would include: 1) System Design Objectives-the development of objectives that support mechanization of the materials management function. 2) System Characteristics and Concepts- the development of key system concepts and characteristics, which identify the needs of materials management. 3) System Inventory Item Classification- development and assignment of inventory category codes to inventory items. 4) System Order Decision Rules-the development of decision rules and forecasting techniques to minimize the inventory investment and to provide acceptable support levels. 5) System Report Structure-the development of a report structure to support the goals and objectives of materials management. 6) System Report Design-the development and design of reports for effective utilization of the mechanized system.

Jan 1, 1979

By Tom Plouf, Deepak Malhotra

INTRODUCTION The U. S. mining industry experienced a severe recession in the early 1980&apos;s. This resulted in the realization that the domestic mining industry had to compete on a global basis and only the strong or the low-cost producers would survive. The economic viability of a mining company not only depended on maximizing mineral recovery but also on its ability to do so at minimum cost. Companies had to become more productive not only by cutting costs, but also by developing and/or evaluating new technologies in existing or new plants. Several innovative concepts, including in-pit crushing and conveying, fine crushing, improved classification equipment, flotation, column flotation, pressure filtration, etc., have been developed in recent years. This paper addresses the impact of new flotation concepts and equipment on mill design. MILL DESIGN PHILOSOPHY Modern mill design, especially for large capacity plants, has its foundation in minimizing capital and operating costs. Capital costs can be minimized by minimizing the various components of the capital cost: infrastructure, equipment, instrumentation, structural, initial spare parts costs, etc. All these costs are minimized by simplifying the mill design and/or process flowsheet. The simplified process flowsheet, where applicable, consists of a single stage primary crusher followed by a semiautogeneous - ball mill grinding circuit to produce feed for a flotation circuit. Multiple flotation circuits have been eliminated in most cases. These concepts minimize the cost and encourage the use of large capacity equipment while maintaining optimum metallurgical recovery. The philosophy of mill modernization/modification is generally driven by the desire to increase the mill capacity within the limits of the existing mill building. This need is facilitated by using large size flotation equipment and eliminating multiple parallel flotation circuits in order to minimize capital and operating costs. Conventional flotation machine development has paralleled this mill design philosophy. FLOTATION CELL DESIGN Since froth flotation has been the most widely used separation process for over half a century, one would expect that it would be possible to design and select flotation machines for specific applications based on scientific principles. But this has not been the case. Best judgment, experience and personal prejudice have played a key role in equipment selection. These factors, along with the difficulty of evaluating new concepts in commercial plants, has slowed progress in implementation and commercialization of innovative ideas and/or equipment. Conventional Flotation There have been no major technological advances in conventional flotation cell design in recent years. A recent flotation cell survey indicates that &apos;larger flotation cells are still the order of the day.”(1) A comprehensive review of design of flotation machines indicate that they have been mechanically redesigned and are generally simpler and easier to maintain and less expensive to manufacture. (2,3) The approximate chronological development of conventional cells from the 25 cubic foot cells to the 3000 cubic foot cells, which were recently installed at the Copperton concentrator of Utah Copper, is given in Table 1. Larger flotation cells are the obvious choice for new plants or plants looking for expansion because of the following reasons: • They have lower capital cost per unit volume • Installation costs are generally lower because fewer units require less space • Maintenance costs are lower because of fewer mechanisms • Power requirements (HP/ton dry feed) are generally lower • with increased flotation cell size as illustrated in Table 2 [Table 1. Conventional Flotation Cell Size Development Year Individual Cubic Cell Size, Feet 1925 25 1935 50 1960 100 1965 300 1970 500 1975 1,000 1980 1,500 1985 3,000]

Jan 1, 1989

By Colin P. Pigott

The paper describes a variety of existing techniques and equipment which when combined together permit faster and cheaper drilling of shafts in soft to medium strength formations. Drilling fluid circulation, methods of hole stabilisation and bit design, including the advantages of flat bottomed and conical bits, shrouds and skirts, tungsten carbide, long tooth and disc cutters are considered. The principles of rock chip transportation and bottom hole cleaning are described together with a new and very efficient fluid circulation system which was invented by the author.

Jan 1, 1985

By M. Gaft, G. Panczer

Sedimentary francolite and magmatic apatite are characterized by specific laser-induced time- resolved luminescence, which allows phosphate to be distinguished from accompanying dolomite. The "selective window" parameters are: he, = 337 nm, delay time after laser pulse is 0.5-5 ps, and detection spectral range is 400-525 nm. In the case of nonuniform distribution of phosphate minerals, it makes it possible to accomplish lasero- luminescent sorting and to receive intermediate product with a lowered dolomite contents.

Jan 1, 1999