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By William G. Doepken

The extensive use of rubber-tired support vehicles as a complement to a fleet of load-haul-dump and drill jumbo units has proved invaluable in maintaining scheduled multilevel/multiheading development drifting advances at the Henderson Mine. Support equipment, whether self-powered or towed, releases primary drill-blast-muck equipment from the supportive functions of ground control, utilities installation, steel and concrete construction and supply handling, thus providing both balance and increased flexibility to an underground, rubber-tired mining system. Experience has indicated that increases in man productivity and improved safety and working conditions coupled with decreases in overall costs and mining cycle times are realized with the inclusion of support vehicles in the mining fleet.

Jan 1, 1976

By M. A. Berdine, C. N. Thompson, D. Brock

The raise bore method of shaft construction has been success-fully used in the mining and construction industries for over thirty years. In the mid 1990’s, Twentymile Coal Company (“TCC”), now affiliated with RAG American Coal Company, used this method for a moderately deep small diameter shaft and the raise bore and slash method for a shallow larger diameter shaft. In late 2001, TCC contracted to raise bore a 431-meter deep, 6.2-meter diameter shaft. During the raise bore and shaft lining processes, regional horizontal stress fields resulted in extensive elliptical caving beyond the original design diameter. This paper discusses the engineering approaches and procedures used to safely complete construction of the raise bore shaft.

Jan 1, 2004

By Paul H. Earl

This paper discusses the evolution of a modeling methodology for explaining price behavior in the aluminum industry. Three generations are described, each utilizing as a foundation a microeconomic stages-of-processing approach. The second generation represents an improvement over the initial version, by incorporating more rigorous specifications of energy cost, and market strength (demand-supply balance) as well as endogenous treatment of market strength. International linkages across prices, costs, and markets, are the major extensions in the third generation. The discussion covers theoretical considerations, data problems and limitations, and model specifications. Simulation and forecasting properties of the models are also addressed.

Jan 1, 1979

By J. L. Watson

n the U.S., lead has been produced via blast furnace processing for over a century, and the slags from that pyro-metallurgical process have been accumulating on industrial sites over that extended period. Lead blast furnace slags typically contain both lead and zinc compounds in an iron-silicate matrix, and it appears highly likely that such materials will have to be processed in the near future to meet with EPA regulations. Thus it is appropriate to investigate possible processing routes to render the slags non-hazardous and simultaneously to recover metal values to partially off-set the inherent high cost of processing such materials. There are two major processing alternatives: one being pyrometallurgical and the other hydrometallurgical. The research reported here investigates leaching/solution purification/recovery processes for lead and presents experimental data for the treatment of lead blast furnace slags from S.E. Missouri. The results of the research suggest that both lead and zinc can be removed effectively from the slag, and that metallic lead can be recovered directly from the organic extractant utilized for solution purification.

Jan 1, 1995

By P. M. Soupios

The study of soft soil (wastes above the rock bed) an issue of great importance in civil engineering, is usually addressed by drilling boreholes. This method is rather expensive and time-consuming and although the information obtained is usually accurate, on the other hand it is much localized. Recently published researches have demonstrated the ability of the combination of geophysical exploration methods to estimate the thickness of deposited wastes, which provides the layered structure of the study area and certain, method depended, mechanical parameters as well. By theory, the frequency of resonance of an upper layer is a function of its thickness and the average shear velocity in it. Furthermore, the application of H/V spectral ratios of micro-tremors is a fast, straight forward and cost effective methodology, yielding the determination of the main resonant frequency of the soil. Based on this framework, 20 microtremor measurements have been carried out in a Landfill in Heraklion-Crete. Some of these measurements were deliberately close to drilled sites, where the basement had been reached. Three electrical resistivity tomographies were also used, in order to define the landfill structure such as, thickness, determination of different wastes distribution in the study area and other parameters. In addition, estimation of predictive Vs using empirical relationship between shear velocity and penetration resistance (SPT?s) were also conducted. Knowing the thickness and the resonant frequency, we estimated the shear (Vs) velocity of the waste cover. The final Vs model was confirmed using the results from the Vs-SPT correlation. The combinative implementation of the above mentioned geophysical and geotechnical methods have successfully defined geometrical and geotechnical/geophysical characteristics of the area under investigation in a fast and cost effective way.

Jan 1, 2005

By Jeffery L. Kohler

The research and development of a pattern recognition system which can predict incipient failures and safety hazards in the mine power network is described. An examination of mine electrical safety hazards revealed they are often related to the electrical equipment down-time experienced on mine sections. Based on this, a method is proposed that can improve both production and safety, without compromising either. Equipment failure modes are examined to illustrate how the ultimate failure can be predicted for enough in advance to allow a convenient and safe repair, followed by a discussion of actual monitoring system performance. Finally, the paper is concluded by projections of the system's utility to industry.

Jan 1, 1977

By I. Chatterjee

The application of microwaves has a demonstrated potential for the ultimate removal of water from fine coal. The principle of microwave drying of fine coal is based on the selective absorption of microwaves by water. Coal is a poor absorber of microwaves. As a result, water can be removed from fine coal by selectively heating water molecules. One of the difficult problems drilling microwave heating is the exact determination of temperature in the core of the materials. The electromagnetic energy absorption in coal/water mixtures during microwave drying is controlled by several factors including the dielectric properties of the constituents. In this paper the dielectric properties of various ranks of coal are presented as a function of frequency and moisture content. The measured dielectric data are incorporated into electromagnetic and thermal models of coal which predict the energy absorption and temperature distribution during microwave heating.

Jan 1, 1990

By E. J. Harvey

The Ozarks has been called "a diamond in the rough". In this region streams have steep gradients, sparkling clear flows of cold water fed by many springs, and a wildness that is almost unique in the central part of the United States today. The Current River and its tributary, Jacks Fork, have been set aside for preservation by the National Park Service as a "Wild River" in the first park of its kind in the country. It is called the Ozark National Scenic Riverway. Similarly, responsibility for the preservation of the Eleven Point River has been assigned to the U. S. Forest Service. Protection of other streams in the Ozarks has been considered by State agencies. The hydrologic system of the Ozarks is a complex network of gaining and losing streams, caves, conduits, and large springs. Increased sewage loads derived from the growing towns and expanding tourist trade are a potential hazard; effluents may flow underground for long distances, polluting springs and wells. To add another dimension to the hydrologic picture a new lead industry is also flourishing in the Ozarks. Although the history of lead mining in the area goes back to 1701 (U. S. G. S., p. 43), the area has not seen a revitalization like the one that has been developing in the last 10 years; and the economic growth promises to continue indefinitely. Although this brings capital expenditures and wages into the area, it also brings potential hydrologic problems. Chemicals, wastes and other substances either stored on the surface or transported across it are subject to accidental spillage. In an area where these substances remain on the surface their effects are subject to surveillance. In the Ozarks, however, this may not be possible.

Jan 1, 1970

By Michael Deutscher, Jozef F. Zurawski

Part of Capital Improvement Project SE-754 tendered by New York City Department of Design and Construction included installation of a 96-in. (2.47 m)diameter sewer by pipe jacking methods. The pipe selected by the Contractor, EIC Associates, Newark, New Jersey, was a glass-fiber-reinforced thermosetting resin pipe installed in two reaches: 72 m (235-ft.) and 222 m (728-ft.). The machine selected for the excavation was an open face shield. This paper describes the set up of the tunneling operations, subsurface conditions, progress of excavation, pipe performance and other details of the project including unexpected difficult ground conditions that were encountered during excavation and how these conditions were overcome.

Jan 1, 2003

By Carlos Kovacs-Figueroa

Because of air pollution control regulations in the early 701s it became necessary to clean effluent gases from the Morenci Reduction Works Smelter. Feasibility studies indicated that this could be accomplished most efficiently by using the smelter gaseous effluent to feed a sulfuric acid plant. Complying with air pollution control regulations thus created the need to dispose of relatively large amounts of concentrated sulfuric acid. Typical Morenci ores contain substantial amounts of oxidized copper minerals which are not recoverable by flotation. In addition, there is low sulfide, high oxide material which can be leached, but is not suitable for flotation concentration. Early in 1971 sufficent data had been accumulated to show that a leaching plant for the Morenci tailings could use a large portion of the sulfuric acid produced by the Smelter. It was determined that for all practical purposes leaching of the available copper was complete in two hours or less. Capital expenditures could not be justified for more than two stages of counter current decantation for recovery of the leached copper, and the plant was designed with these criteria in mind.

Jan 1, 1976

By J. Gordon Scott

The Iron Ore Company of Canada has now been operating a computer for the grading or blending of direct shipping ores for two years. This paper deals with the computer application pertaining to the grading of direct shipping ore. It consists of five sections. The first part deals briefly with a description of the operation of the Iron Ore Company of Canada; the second with the source and flow of the various data required to grade or blend ore; the third briefly outlines the computer programs used in this application; the fourth illustrates the mathematical approach used to properly blend ore. The final section briefly describes other technical computer programs.

Jan 1, 1964

By K. Sample

Slope stability analysis plays an integral role in the design of various mining applications including waste dumps, heap leach piles, solution ponds, and tailings dams. Generally, limit equilibrium analysis using one of the several prevalent approaches is considered adequate. The density, saturation, and shear strength parameters of the materials forming the slope affect the failure mode and the calculated factor of safety (FS) against sliding. These parameters are generally based on laboratory tests. Field practices and construction procedures are often not completely simulated in the laboratory for various reasons (e.g. equipment limits, time and budget restraints, etc.). This paper presents a holistic assessment of slope stability analysis as practiced in mining applications, using example data from multiple heap leach projects. A sensitivity analysis is presented for variations in material properties, data interpretation, and computation methods. For each step in the design process, the possible variations in parameter values were identified and then used to perform traditional and probabilistic stability analyses. This simple, cradle-to-grave-type approach is used to evaluate the reliability of an example design, and the combined impact of multiple uncertainties on the factor of safety. Example Study The issue of addressing uncertainty in geotechnical design has been discussed in depth by numerous authors (Duncan 2000; Christian 2004; Whitman 1984; Christian et al. 1993). One may ignore the uncertainties involved in a design, take a conservative approach, rely on observational methods (Peck 1969), or attempt to quantify the uncertainty. Geotechnical projects in general, may include a combination of these methods. For important structures, such as heap leach pads, it is critical that sources of uncertainty in the stability analysis be acknowledged early on and considered in the overall design approach. As with any project, economics and other physical constraints, such as space limitation, often do not always allow for an overly-conservative, robust design. In an effort to quantify uncertainty and provide a sense of level of confidence in the safety and reliability of a design, probabilistic methods have been developed and implemented in many slope stability software packages. Reliability methods are often used in the design of open pit mine slopes, but not as commonly in designing heap leach pads and waste dumps. As an example, the stability analysis of a copper heap leach project is presented here to evaluate the effects of multiple sources of uncertainty and differing methods of data interpretation. Some of the parametric values, or the variation therein, are assumed on the basis of actual data from multiple heap leach projects, included in the paper as well. A generic representation of the example case study is shown in Figure 1. As depicted in the cross-section, the ultimate height of the design is 114 m (measured from the crest to the toe). The overall slope of the heap leach pad is 1.88 horizontal to 1 vertical (1.88H:1V), or 28°. The slope benches are considered in the overall slope. The example leach pad is founded on alluvial, colluvial and residual soils overlying weathered limestone. The ore to be placed on the pad is characterized as poorly graded gravel (GP) with average fines content (percent passing #200 sieve) of 4%. The liner subgrade is low permeability (fine) soil. The cover or the drainage material, placed directly above the geomembrane (between the liner and the ore), is crushed ore in this case. The phreatic surface was assumed to be 1 m above the base liner, which is what the collection system over the liner is typically designed for. [ ] In heap leach pads, typically, Linear Low Density Polyethylene (LLDPE) or High Density Polyethylene (HDPE) is used as the base liner. The decision is based on the elongation, strength and other requirements of the application as well as economic considerations. In this example study, the base liner was 80-mil single-side textured LLDPE. FIELD INVETIGATION AND SAMPLING When selecting appropriate values for the input parameters of the stability analysis, the level of uncertainty in the data and the assumptions that are made must be clearly identified and considered in the design. This concept has been emphasized through an extensive number of publications regarding geotechnical uncertainty and reliability (Christian et al. 1994; Duncan 2000; Christian 2004). The primary source of uncertainties involved in slope stability analysis for mining applications is inadequate geotechnical investigation, often lacking in a thorough assessment of in-situ material characterization and sampling disturbances. To emphasize this point, some background information is presented here. The tradeoff between the costs of a thorough site investigation versus the risks of design uncertainty has long been a challenging management decision in geotechnical projects. For mine sites, significant investment is typically made in exploration and estimating mineral resources and the geology of a mine site is often more thoroughly documented than other types of geotechnical projects. Nevertheless, the engineering properties of the soil and rocks relevant to slope stability receive less emphasis. Baecher and Christian (2003) observed that the areas of geotechnical concern, such as slopes and waste disposal facilities, are usually associated with mine costs rather than revenue, and therefore, significantly less money is devoted to their site characterization and laboratory testing. The expenditure for site investigations varies significantly from project to project, with higher levels of uncertainty and, therefore, the

Jan 1, 2009

By J. D. Miller

The recent non-equilibrium electro-phoretic mobility measurements by laser-Doppler electrophoresis coupled with the stability and prevalence of collector colloids in soluble salt flotation systems suggest that the selective flotation of alkali halides is due to the adsorption of oppositely charged collector colloids by hetero-coagulation. Previously reported flotation results confirm this surface charge/collector colloid adsorption model. However, the nature of the inter-particle forces responsible for hetero-coagulation of such oppositely charged particles at high ionic strengths remains to be determined. In this regard, atomic force microscopy was used for inter-particle force measurements at high ionic strengths. Model systems such as polystyrene/quartz and silica/sapphire were studied to measure the particle interaction forces prevalent at high ionic strengths. Results from this study indicate that while repulsive hydration forces exist between similarly charged hydrophilic particles, attractive forces exist between oppositely charged hydrophilic particles in high ionic strength solutions. The repulsive forces between similarly charged hydrophilic surfaces at high ionic strengths (2-4 M) are described by a double exponential function with decay lengths of 0.17 and 1.4 nm depending upon the surfaces involved. On the other hand, attractive forces were observed between oppositely charged hydrophilic surfaces at high ionic strengths (2-4M) and were described by a single exponential function with decay lengths of up to 9 nm depending upon the surfaces involved.

Jan 1, 1996

By Adolph V. Mitterer

International Minerals and Chemical Corporation operates one of six potash mines in the Carlsbad potash basin. More than 90 percent of America's potash is produced at Carlsbad and IMC accounts for about one-fifth of that amount, Since the Company began operations in 1941 it has mined nearly 50 million tons of ore. Of the two types of ore mined at Carlsbad the principal tonnage is sylvinite in which sylvite-potassium chloride-is the ore mineral. It is produced by IMC as well as by all other mines in the area, In addition to sylvinite IMC is the exclusive producer of langbeinite ore--potassium-magnesium sulfate. From its two ores, International produces a spectrum of 8 high-quality agricultural and industrial chemical products.

Jan 1, 1959

By R. F. Merwin

Advancement in automation intensifies the need to remove tramp iron from bulk materials being processed and carried on belt conveyors. Although magnets have long been employed for this purpose, it becomes increasingly necessary that magnetic equipment of appropriate types and sizes be selected and advantageously installed -- if maximum benefits are to be derived Tramp iron present in bulk materials consists of ferrous trash, such as wire, bolts, nails, equipment parts, tools, and machine cuttings. The results, if the iron is not removed, are damaging to equipment having close clearances, explosions, or fire, En the case of flammable materials, production downtime losses, and contaminated products.

Jan 1, 1966

By Thomas E. Shufflebarger

Definition of glass sand prospects may be modified by constraints which range from demography to critically important product-control. Characteristics of usable raw materials, physical and chemical, are discussed; an ideal raw material is defined. Following field investigations and preliminary sampling, evaluation of selected prospects includes use of modern drilling techniques, viz.: core, percussion (air-hammer), auger, jet, rotary jet, split-spoon and other. Nearly complete core (sample) return is mandatory. Land-use regulations, availability of water and transportation continue to direct exploration in a major sense. But fitting a prospect to burdensome politics nay be considered a decidedly negative factor.

Jan 1, 1983

By John E. Anderson, Charles A. III Cravotta, Eleanora I. Robbins, E. Terrance Slonecker, Gordon L. Nord

Remote sensing is being tested for its ability to identify the severity of impact on streams that are subjected to contaminated mine drainage (CMD) in the Southern Anthracite Coalfield of Pennsylvania. Airborne digital multispectral video images of acidic and near-neutral CMD are being compared with field spectra, water chemistry, mineralogy, and microbiology. Spectral differences in the visible region of the electromagnetic spectrum are caused by the presence of schwertmannite in the acidic precipitates and ferrihydrite in the near- neutral precipitates. The acidic CMD averages 1,500 mg/L sulfate and has bacteria coated with schwertmannite; the near-neutral CMD averages 87 mg/L sulfate and has bacteria coated with ferrihydrite.

Jan 1, 2000

By Valérie J. Bertrand, Richard W. Lawrence, Marcos G. Monroy

Two cemented paste backfill (CPB) formulations containing pyritic tailings were leached in deionized water in flooded and alternating air-flooded environments and in a simulated acid rock drainage-type (ARD) solution. Scanning Electron Microscopy (SEM), solid phase chemistry and acid-base accounting measurements documented the weathering characteristics of the CPB samples. Short-term exposures of the portland-CPB samples preferentially dissolved the cement binder to a greater extent than slag-Portland CPB mistures. In all cases, the added neutralizing potential provided to backfill by cement was short-lived and insufficient to neutralize the acid generating potential of the mixture.

Jan 1, 2000

By Edgar O. McAlister

Associated with cordilleran intrusives of intemediate to acidic composition, gold/silver ores are generally found in the intruded host rocks which are adjacent to these intrusives. Generally precious metal deposits lie further from the intrusives than allied base metal deposits. For vented intrusives, the associated volcanics may constitute the intruded rock and form the host for precious metal accumulation. Potential field methods, particularly magnetics, can help to define unseen boundaries of intrusive systems and thus can point to generalized prospecting targets. Other clues arise from the intrusive system type, its emplacement fracturing, the host rock type and local magnetic changes caused by mineralization processes.

Jan 1, 1984

By R. P. King

The MODSIM mineral processing plant simulator is used to find optimal combinations of target separation specific gravities in a typical modem coal washing plant. A plant that is set up with these optimal targets can deliver up to 10% more yield at the same ash content as the same plant set up with separation targets chosen by conventional methods. MODSIM is the only simulator currently available that can simulate the liberation of pyrite and other mineral matter during open-and closed-circuit grinding operations. The simulator can therefore be used to assess the benefits of grinding operations in the flowsheet.

Jan 1, 1997