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By K. Nielsen

The paper uses three examples to illustrate the challenges that the minerals industry is facing with regard to our image and the public?s perception of us. The paper then discusses communication with stakeholders as opposed to lecturing to the public and the authorities, and states that the industry needs to work more directly towards politicians and regulators as target groups. The conclusion is that we still have a way to go before the industry is doing enough to bring our message to the right people, but we are improving.

Jan 1, 2007

By Thomas M. Tharp, Mark A. Travers

A new method is presented for precracking three-point bending specimens for fracture toughness testing. A notched specimen of rectangular cross section is placed on a flat loading platen, with paper between specimen and platen. The specimen is loaded from above through a roller placed directly over the crack. The thin, high compliance joint between specimen and platen causes a distributed load on the bottom of the specimen. This results in bending at the cracked section and crack initiation at the notch tip. Since the joint is thin, its stiffness increases rapidly with deflection and crack propagation in the specimen generally remains stable and controllable. Fracture toughness KIC in a sandstone directly overlying the No. V coal was measured to be 0.27 MPa m 1/2. Even for cracks 1 cm long this value of KIC results in substantially lower effective tensile strength (modulus of rupture) in roof beams than is expected from intact rock strength.

Jan 1, 1986

In general, it cannot be assumed that the strength of coal pillars remains constant over long periods of time. Field observations indicate that a coal seam, especially when it contains a parting layer, deteriorates over time, reducing the load-bearing capacity of the pillars. This paper discusses a unique approach to determining the time-dependent strength of coal pillars in the field. Three coal pillars that were developed 5, 15, and 50 years ago were chosen for the study. Holes were drilled in coal and parting layers in each pillar, and the strength profiles were determined for each hole using a borehole penetrometer. The strength data were treated statistically to establish time-dependent strength equations for different layers. The results can be used to help estimate the loss of pillar capacity over time.

Jan 1, 2012

By Hooman Askari-Nasab, AHLAM MAREMI, EUGENE BEN-AWUAH

In oil sands mining, tailings are voluminous unwanted byproducts generated from extracting the desired mineral from the mined ore. Dyke construction and backfilling activities require well-managed techniques to facilitate progressive reclamation at the earliest opportunity. This directly affects the sustainability and profitability of the mining operation. This research introduces a goal programming framework that simultaneously optimizes the (1) production schedule with limited duration stockpiling and directional mining, (2) dyke construction schedule, (3) size, shape and location of tailing cells and (4) mining and processing production targets. The results show that in creating in-pit tailing-cell designs, decreasing the mining-cell volume and increasing the number of mining cells improves the net present value (NPV) of the operation due to increased operational flexibility.

By Robert W. Bartlett

Heap biooxidation of sulfidic refractory gold ore requires large amounts of oxygen, as shown in Figure 1. Bacteria, Thiobaci/lus ferrooxidans, are donnant at oxygen concentrations below about 3% in air (1 ppm in aqueous solution) because ofmonod kinet­ics. Hence, the maximum possible utilization is only about 75%, and it may be much less than that due to poor air sweep effi­ciency. At the maximum oxygen utilization, an ore containing two percent pyrite requires nearly 100 cubic meters of air per tonne (4,000 cubic feet per ton). The stoichiometric air require­ment to oxidize arsenopyrite is similar to that of pyrite. While the leaching solution percolating through the heap introduces some dissolved oxygen, the amount is insignificant because of the low solubility of oxygen in water, 7 to 8 ppm at atmospheric saturation. There are only three ways to provide oxygen to the heap: either air flow by natural convection, diffusion of oxygen from the surface (through stagnant air in the air-filled void space in the heap), or forced air ventilation of the heap. Each of these processes will be reviewed.

Jan 1, 1996

By C. Allen, H. Zhang, L. Falk

Shock loss occurs when there is a change in the area of a drift or airflow direction. These shock losses accumulate throughout the ventilation system and will increase the mine resistance as underground development deepens or becomes more complex. Hence, shock losses should be carefully considered when establishing the resistance through a series of branches as they can be a significant contributor to the estimated mine resistance. Using computer software to simulate a ventilation system is common but applying reasonable shock loss factors in the software is not a simple or direct process. Determining shock loss values includes the consideration of historical measurements, application of factors and formulas from literature based on the geometry and complexity of junctions, and the geometry variation at different locations. For example, the shock loss at the bottom of a ventilation raise can consist of a 90° bend and a sudden area change. This paper presents an approach for estimating shock loss factors near raise junctions using computational fluid dynamics (CFD). Current and future work will also be compared with field measurements. Results from this approach are compared with software defaults as well as classical techniques in published literature and standards.

Sep 1, 2024

By Jeffrey P. Chanton

A specialized Pore-Fluid Array sampler (PFA) was designed to collect and store pore-fluids to monitor temporal changes of ions and gases in gas hydrate bearing sediments. We tested the hypothesis that pore-fluid chemistry records hydrate formation or decomposition events and reflects local seismic activity. The PFA is a seafloor probe that consists of an interchangeable instrument package that houses OsmoSamplers, long-term pore-fluid samplers; a specialized low-dead volume fluid coupler; and eight sample ports along a 10-meter sediment probe shaft. The PFA was deployed at Mississippi Canyon 118, a Gulf of Mexico hydrate site. A 160-day record was acquired from the overlying water (OLW) and 1.3 meters below seafloor (mbsf). Fluids were measured for dissolved chloride, sulfate, and methane concentrations and dissolved inorganic carbon and methane stable carbon and deuterium isotope ratios. Chloride and sulfate did not change significantly over time, suggesting the absence of gas hydrate formation or decomposition events. Over the temporal record, methane concentrations averaged 4 mM at 1.3 mbsf and was thermogenic in origin (d13C-CH4 = -32.4±3.4?). The timing of an anomalous 14 mM methane spike coincided with a nearby earthquake (Mw=5.8), consistent with the hypothesis that pore-fluid chemistry reflects seismic events. Keywords: Osmosampler, gas hydrate, methane, stable isotopes

Jan 1, 2008

By K. W. Deter

The gold ores in the Jerritt Canyon district have been recognized as refractory since they were first encountered by FMC geologists in 1976. Upon obtaining managing rights as joint venture partner, Freeport McMoRan Inc. developed an operating plan featuring carbon-in-leach gold recovery techniques for the oxide portion of the ores and a patented sulphide oxidation step followed by chlorination for treating the organic carbon constituents of the refractory ores prior to CIL gold recovery. The plant was successfully started up in 1981 with the first gold poured on July 4, 1981. Initial plant throughput was designed to be 2495 MTPD (2750 STPD) total through the dual processing trains.

Jan 1, 1991

By S. Nygren

Nalco Chemical Company and a North Carolina Phosphate operation have formed a successful supplier/customer team effort that has resulted in major improvements in the operation of the clay thickening circuit at the Aurora, North Carolina concentrator. A Nalco OPTICUS® Automated Process Control System for thickener and flocculant control was installed in 1994. The paper will discuss in detail the development and refinement of the OPTICUS system over the past three years. The paper will survey the development and networking of process control for monitoring, controlling and operating four 325-foot Dorr-Oliver thickeners, three 80-foot high-rate Enviro-Clear thickeners and control links to the facility's clay/gypsum blending operation.

Jan 1, 1998

By Sheldon P. Wimpfen

Under the Wilderness Act of 1964 and the accompanying House Conference Report, the Geological Survey and Bureau of Mines are charged with the responsibility of making recurring mineral studies of wilderness and wilderness candidate areas in national forests within and proposed for the National Wilderness Preservation System. The Wilderness Act, a major shift from the multiple-use concept of national forests, identified for the first time the value of mineral resource information in decisions for single-use designation of public lands. This concept was further realized when the Secretary of the Interior in May 1974 recommended that mineral studies be made prior to wilderness recommendations for five large Interior-managed game ranges and the Glacier Bay National Monument aggregating 7.8 million acres. Presently, our studies have been completed on 126 wilderness and proposed wilderness areas totaling 15.4 million acres in the national forests. In 1973, 1 year in advance of the act's 10-year review deadline, we completed the 34 primitive areas, originally the only potential additions considered by the 1964 Act.

Jan 1, 1975

By T. J. Cox

The Red River is located within the Sangre De Cristo Mountain Range in northern New Mexico. An approximate 12-mile segment of the river from the town of Red River to the village of Questa (Questa) includes several hydrothermal alteration zones. Alteration ?scars? formed as a result of rapid chemical weathering and physical erosion of pyrite-rich hydrothermally altered rocks. Storm water runoff from the scar drainages contributes metal-laden, acidic water to the river and creates a visible plume of discolored water in the river. Acidic runoff reduces the river pH from 7 to the mid 3s for at least 2 hours during large storms and the low pH water continues downstream. Runoff from scar drainages increases some metal concentrations in the river from below chronic ecological criteria to as much as two orders of magnitude greater than acute ecological criteria, and results in acutely toxic conditions for macro-invertebrates. A general improvement in the river?s water quality occurs downstream due to dilution from tributary inflow from non-mineralized watersheds, the natural buffering capacity of the river, and storm water controls at the Chevron Mining Inc. Questa mine.

Jan 1, 2011

By B. Seymour

The National Institute for Occupational Safety and Health (NIOSH) is conducting research to develop safe practices for the use of shotcrete as ground support in underground mines, particularly mines operating in weak host rock. As part of this research, tests were conducted with a commercial poly-fiber reinforced shotcrete mix to develop a practical means of measuring shotcrete adhesion strength. Full-scale tests were conducted in a test frame equipped with concrete panels having three distinct surface roughness profiles. Adhesion test fixtures either embedded or epoxied in the shotcrete were overcored into the underlying concrete, and direct tensile tests were conducted to determine the bond strength of the shotcrete cores to the substrate after a selected shotcrete curing interval (1, 3, 7, 14, 28, or 90 days). Measured adhesion strengths typically ranged from 0.5 to 2.0 MPa depending on the curing age of the shotcrete samples. This paper presents the results of these tests, describes the portable test system components, and addresses some of the design issues encountered in the development of a rugged and reliable method for determining shotcrete adhesion strength in underground mines.

Jan 1, 2010

By R. R. Klimpel

Introduction The grinding of coal-water slurries has received increasing industrial attention during the last decade. In particular, there is long-term interest in the use of pulverized coal-water slurries to replace oil in combustion equipment and in the development of coal gasification/liquefaction processes that require coal-water slurries as feed. More specifically, the use of coal-water slurries in gasification requires grinding a high-density slurry containing the smallest amount of water consistent with slurry pumping and spraying. As part of a fundamental engineering research support program aimed at the industrial implementation of dense coal-water slurry grinding, this author has published several papers on how specific rates of breakage vary as a function of slurry rheology (Klimpel, 1982,1982/83). These papers demonstrated that there is a consistent pattern of change in specific rates of breakage of coal in dense slurries with controlled variation in slurry rheology. By matching rheological data with laboratory grinding results, it was possible to identify directly slurry conditions that correspond to: 1) slowing down of breakage rates, 2) the occasional acceleration of breakage of some sizes, and 3) conditions where chemical additives will increase rates of breakage. In brief, these conditions were analyzed using two different criteria: a) the net production rate of material less than some specified size (e.g. kg/min of minus 325 mesh) in a standard batch laboratory mill test as a function of controlled changes in grinding conditions, and b) the use of the one-size-fraction feed method, which consists of following the disappearance of this largest size over grinding time in a batch laboratory mill to arrive at well-known specific rates of breakage (Austin et al., 1984). Detailed references to the methodology used as well as the conclusions are available (Klimpel, 1982, 1982/83) and will not be repeated here. The purpose of this paper is to further demonstrate several additional characteristics of dense coal-water slurry grinding that were shown in a simplified sense in the earlier publications of the author but which have clearly demonstrated themselves as being very important in the industrial simulation and scale-up of such coal-water grinding systems. In particular, this includes the clear and unambiguous demonstration of how the simultaneous acceleration of breakage of some size fractions and slowing down of the breakage of other size fractions is occurring as a function of changes in coal-water slurry density. In the earlier publications (e.g. Klimpel, 1982), it was shown by specially designed experiments that the addition of fine material and/or the use of a chemical thickening agent accelerated the specific rates of breakage of coals of coarser size fractions using the one-size-fraction method. There were also numerous examples given of non first-order breakage (the slowing down of coal breakage rates) using also the one-size-fraction method due to the presence of excessive amounts of fines which corresponded to the development of a rheological yield value. The problem with the simulation and scale-up of any laboratory and/or pilot-scale mill data to an industrial scale using the mechanistic modelling approach involving specific rates of breakage and breakage distribution parameters (e.g. Austin et al., 1984) is the number of assumptions involved in translating the smaller mill breakage parameters to the predicted larger mill breakage parameters. It is apparent, at least to this author, that to accurately simulate and predict larger scale equipment performance from smaller scale data (given that the larger scale data performance is known and hence predictions can be thoroughly checked) requires a better knowledge of breakage parameters than is currently available. More specifically, it was felt that one of the chief problems was the inability of the one-size-fraction method of determining breakage parameters to sufficiently represent the actual magnitude and sometimes even the directions of. the complicated interactions involved with slurry density changes in coal-water slurry grinding. Thus, a special set of experiments was conducted in a somewhat larger batch ball mill (0.457 m diam x 0.610 m length) than the 0.203-m-diam mill used in the original rheology characterization paper (Klimpel, 1982) so as to minimize any unusual effects due to wall-ball interactions (2.54-cm-diam balls used in both mills). More importantly, the measurements of specific rates of breakage were done using a proprietary tracer method on a portion of a given size fraction, which was then remixed into a natural feed size distribution before grinding. The experimental procedure and analysis of subsequent data was done in exactly the same manner as the radioactive tracer technique on coals as originally developed by Gardner (1962). The advantage of such an approach is that it makes no assumptions such as the independence of the specific rate of breakage of any size on the absolute sizes and amounts of other sizes present (both larger and smaller) in the mix of natural feed material. It will be shown that the measured rates of breakage using the direct tracer technique and the one-size fraction method on the same coal are indeed different. In fact, an accurate assessment of what is happening to the rates of breakage as a function of changing slurry density can only he made by measuring particle breakage under grinding conditions approximating the size distributions actually being produced in practice. Experiment procedures and results The pilot mill used was 44 cm diam x 60 cm long with a volume of 91,250 cm3 and was fitted with six 0.5-in. lifter bars.

Jan 1, 1992

In a future world of 8.5 billion people in 2035, the Energy Information Administration's (EIA) projected 50% increase in energy consumption will require true "all of the above" energy resource use from oil, gas, renewables, nuclear, and coal. In particular, coal will continue to be the world's energy cornerstone, providing more incremental energy over that same time period than any other single fuel. Coal has long been a centerpiece of a low-cost, high-reliability electricity grid. Today there are 1.3 billion people across the globe without access to electricity and 2.7 billion people who do not have clean cooking facilities. The problem is spread across the developing world, but it is particularly severe in sub-Saharan Africa and developing Asia, which together account for 95% of people in energy poverty. Without a commitment to achieve universal energy access it has been estimated that by 2030, there will be an additional 1.5 million premature deaths per year caused by household pollution from burning wood and dung and through a lack of access to clean water, basic sanitation and healthcare. Modern energy sources are essential to meeting these challenges.

Jan 1, 2012

By W. Dresler

Since 1900, smelters have produced in Canada over 10 million tonnes of iron silicate waste slag containing significant quantities of nickel, cobalt and copper. The slag is reduced with aluminum and calcium oxide additions to produce a copper, nickel, and cobalt enriched alloy and an obsidian slag. It was found that the obsidian slag contained very low copper, nickel, and cobalt contents, indeed below 0.06% of each the base metals. These metals have been collected in a type of ferroalloy with up to 1.6% Cu, 2.1% Ni, and 0.7% Co. These alloys can be recycled according to standard procedures in base metal smelters. Surprisingly, the obsidian slag was found to display good cementitious and pozzolanic properties, which is a requirement for cement production. The strength producing properties of the obsidian slag are considered to be exceptional at the 28 day standard test age. In most cases, the obsidian concrete is characterized by significantly greater strengths than control concrete tests and concrete containing fly ash or blast furnace slag. Compressive strength data at 365 days for the obsidian concrete is impressive.

Jan 1, 2003

By C. W. Newcom

The mining industry continues to be under expanded scrutiny in the health and safety arena, both from federal regulators and the media. While this paper will briefly discuss how enforcement activity, both with citations issued and the size of penalties proposed, the primary focus will be practical suggestions to deal with some key, high-risk areas for a mine operator which could have substantial impact, both in terms of liability and mine operations. It goes without saying that all mine operators need to continue compliance programs they have in place with careful ongoing evaluation of those plans for areas of improvement. The focus here will not be compliance as such, but rather steps to take and procedures to have in place to try to minimize risks in the face of the potential for more significant liability. Thus, our focus will be procedures to respond to unwarrantable failure citations, immediately reportable accidents, and to deal with potential pattern of violation issues.1

Jan 1, 2011

By Dale D. Teeters

Today, I would like to talk about ways to maximize the efficiency of surface coal operations. I doubt I will present any startling new ideas, but my comments may, hopefully, stimulate some conversation today and later back at your own operations. Strip mining is a very old technique used by ancient societies. Only with the coming of the machine age in the early twentieth century did we attempt to increase the magnitude of our operations. The industry, as we know it today, really only got started in the early 1900s with the advent of steam shovels. In the first portion of this presentation, I will attempt to show that we have, in many cases, not changed the basics of strip mining, only the scale. In doing so, quite often we have complicated the operations to the point of being unmanageable and unprofitable.

Jan 1, 1981

By John Relser

The production processes that are developed in the mining and minerals industry are manufactured to be exposed to very aggressive environments. Chemical, abrasion, and impact expose structures and equipment, steel or concrete, to a significant deterioration. This causes damage and adds high costs to operations that can be reflected in the destruction of equipment and structures in the arrest of the production process, which becomes very costly. Also, there is the potential for personnel accidents, which would require large sums of compensation for an employee, thus directly harming the image of the mining operation and company. Manufacturers of paints and coatings that have major centers for research and development (R&D Labs) distributed globally have developed high-tech products for durable protection from the elements for structures and equipment used in the mining industry. The difference between these paintings and coatings and what is normally known as conventional paints (e.g., those called domestic or decorative), is its chemical composition, structured around polymeric components that have highly resistant, chemical and physical properties to cope with extreme conditions to which they are exposed. With this, and only this, longer life of components can be achieved for equipment and structures used in the production processes of the mining industry. Today, in addition to the important features mentioned, some manufacturers of the paints and coatings dedicated to this highly modernized process have invested large sums of money in developing new products that add operational elements to the painting process. These coatings provide added value and significant performance to companies mining operations and that we can describe in three fundamental concepts:

Feb 1, 2014

By Weijie Wei, Jinwang Zhang, Jiachen Wang, Yang Li

"Longwall top-coal caving (LTCC) mining technique is one of the important methods for underground thick seam extraction in China. The coal seam in LTCC panel is divided into two parts: bottom-coal and top-coal. The bottom-coal is mined by conventional longwall method while the top-coal is mined by caving method. The top-coal caving process in LTCC and block caving process in metal mine are both gravity flow of loose ore/coal blocks. However, the presence of caving shield in LTCC makes the characteristics of drawing body shape in the two caving processes differ a lot. This paper discusses the influence of caving shields on the characteristics of drawing body shapes in light of recent studies of the top-coal drawing process. The theoretical model for describing the drawing body shape in LTCC is proposed both along the seam strike and seam inclination. Then, the experimental data are used to validate the correctness of the theoretical model. Furthermore, two examples of how the theoretical findings assist LTCC mining are given and discussed.INTRODUCTIONLongwall top-coal caving (LTCC) mining technique and large-cutting-height mining technique have been widely used for extracting thick coal seams in China. About 0.6–0.7 billion metric tons of coal come from longwall top-coal caving panels every year. The maximum annual production is 15 million metric tons per panel _The mining method employed in such panel is a combination of top-coal caving mining technique and large-cutting-height mining technique, which is suitable for seam height between 12–20 m, as shown in Figure 1. Apart from China, LTCC has also been employed in some coal mines in Australia and Vietnam (Le et al., 2017).The coal seam in a LTCC panel is divided into two parts: bottom coal and top coal. The bottom-coal is mined by the conventional longwall method, while the top coal is mined by the caving method. The top-coal caving process in LTCC and block caving process in metal mines are both gravity flows of loose coal/ore blocks, as shown in Figure 2. However, the presence of caving shields in LTCC causes the characteristics of the drawing body shapes in the two caving processes to differ significantly.There are two main differences between the blocking method and the top-coal caving method:"

Jan 1, 2019

By Leonard Sargeant

The Pocahontas Coal Field consists of eight mineable seams of low-volatile coal in southern West Virginia and Virginia. The deeper seams, especially the Pocahontas No. 3 and No.4 Seams, under heavy cover and below drainage are notoriously gassy. Methane in the Pocahontas Field is generally thought of as being confined in the coal itself, rather than in mud slips or clay veins. Furthermore, it is characteristic of Pocahontas coal to retain its gas until the coal is broken and removed from the solid. Because of this inability for gas to escape from unmined coal, entries developed around large blocks are seldom of significant value in bleeding off methane before pillar extraction begins. This is evidenced by the fact that it is not uncommon to find gas liberated during the mining of chain pillars and barriers which have been developed for several years. The Pocahontas Fuel Company develops almost all solid coal by conventional methods with shuttle car haulage. To provide the maximum productive capacity without compromising ventilation and safety requirements, the Company has adopted standards for ventilating 5, 6 and 7-entry sections.

Jan 1, 1960