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By T. M. Ruff, W. G. McCoy, M. J. Beus, S. Iverson, W. Hasz

Technology to enhance safety during mine hoisting has been developed by researchers at the Spokane Research Laboratory of the National Institute for Occupational Safety and Health. Assessment of current hoisting technology suggests that monitoring conveyance position and load directly from the skip or cage top offers several significant safety advantages. Wireless data transmission schemes and a package consisting of sensors, batteries, and a charger mounted on the wire rope and skip have been developed. A state-of-the-art automated hoisting test facility was constructed to test the concept in a controlled laboratory setting. Field tests in a full-size shaft are underway.

Jan 1, 1999

By M. S. Klima

Proper analysis of washability data can lead to the development of a maximum yield coal preparation plant flow sheet. Simulations, as simple as spreadsheet mass and water balancing, are important in examining yield maximization and middlings liberation. Key to such attribute tracking flow sheet simulations is the distribution model, expressing the probability of a species reporting to the product stream. There are many such models in the literature. This paper examines a functional form that can represent or fit most of the proposed distribution functions.

Jan 1, 1997

By Norm Steenson

Rapid excavation includes rapid support and is the central theme of this paper. Over the last few years, enormous strides forward have been made in the excavation and material handling aspects of underground excavation. However, the technology necessary to support these rapidly created openings has lagged behind the other aspects. This paper would attempt to bring you up-to-date on the progress made in bringing ground support using shotcrete into the same productivity rates as the other cyclic operations. Shotcrete has become an acceptable material for temporary and permanent support for undergound openings. However, coarse aggregate shotcrete has been an expensive construction material. It has been confined in the main to difficult ground conditions where conventional methods of support have proved to be even slower and more expensive than shotcrete. There are two main factors influencing the productivity of shotcrete equipment. (1) Structural shotcrete as opposed to gunite requires 40% to 45% rock minus 3/4" in the mix design. The equipment to handle such aggregate content has been difficult to develop on a volume basis owing to the attritional nature of the material which causes intense wear problems on

Jan 1, 1974

By C. L. Lin

Linear grade distribution measurements determined from polished sections of randomly oriented particles can be used to estimate the extent of liberation for multiphase particles of specified size. Two techniques, optical image analysis and microprobe analysis, have been used to establish linear grade distributions. Both techniques were evaluated and compared using variable grade samples of products from a copper porphyry flotation circuit. The statistical significance of the linear grade distribution data obtained by optical image analysis was assessed. The average chalcopyrite content of these samples, as determined by chemical assay was used to estimate the variance of the experimental procedure. For a given accuracy, the number of particles required to obtain an unbiased representation of the sample was determined.

Jan 1, 1985

By Paul E. Epstein

Despite the controversies that have surrounded asbestos over the past 20 to 30 years, no knowledgeable authority has doubted the usefulness of this material. Were it not for the health risks associated with the manufacture and use of asbestos products, its physical and chemical characteristics would continue to be hailed as an undeniable boon to mankind. However, it has become clear over the past 30 years that like other major contributors to our modern industrialized society, asbestos must be handled responsibly and with the full understanding that lack of care can lead to injury, suffering and death. In this sense, asbestos shares characteristics with nuclear power, pesticides and even motor vehicle usage. It is unlikely that modern society would be willing to walk away from the benefits bestowed by any of these valuable resources. Rather, the appropriate response to the identification of danger is to define the type of risk, quantify its incidence, search for methods of decreasing the risk and implement programs to achieve the goal of minimization of risk. We should recognize at the outset that the risk cannot be diminished to zero without elimination of the material entirely from our midst. The concept of acceptable risk is a complex issue involving medical, legal, financial, moral and even psychological factors that defy precise quantification. In essence, the major danger produced by exposure to asbestos is its potential effects on the respiratory system. Despite the fact that asbestos workers have constant skin contact with the material and porbably swallow it in the course of their activities, inhalation of the fibers is recognized as the major health risk associated with its use. Aerosols of asbestos are inhaled not only by miners, millers and fabricators but also by urban dwellers who have no direct occupational contact with the material. This occurs because asbestos has been applied to our buildings and has been used in a wide variety of products that touch our daily lives. While it is estimated that three to four million people in the United States have been occupationally exposed to asbestos, the number who have been non-occupationally exposed is many times that number.

Jan 1, 1984

By P. Chauvet

From a computational point of view calculating a variogram is a perfectly simple operation. For any particular study, we know which variable is to be studied. We also have a good idea of structural parameters which are likely to be important (the scale of the phenomenon, the probable direction of the anisotropy, etc.). Finally, we know the structure of the data file. So we can specify the parameters to be used to calculate the variogram (the distance classes, the angular classes, etc.). This allows us to decide which variogram program is most appropriate (1, 2 or 3 dimensional data, regularly or irregularly spaced, etc. ) . In general, the basic statistics (mean, variance, correlation? etc.) have been calculated beforehand, and so the distribution of the data is already known. Consequently, the choice of the parameter values fed into the variogram is by no means arbitrary. But it must nevertheless be made before the' variogram is calculated. If the resulting variogram is not satisfactory, the whole sequence of operations has to be repeated. Before going on to see how this can be avoided, it is worthwhile having a brief look at the common causes of "unsatisfactory" variograms.

Jan 1, 1982

By C. A. Young

Previous experimental results have shown that an increase in temperature and/or oxygen concentration leads to an increase in the hydrophobicity of fluorite (CaF2) with adsorbed oleate. Subsequently, ex-situ Fourier transform infrared (FT-IR) transmission studies suggested that this increase in hydrophobicity was the result of double-bond reactions between adjacent oleate species adsorbed at the fluorite surface. Now an in-situ FT-IR study on single crystals of fluorite has been used to monitor this phenomenon using internal reflection spectroscopy (IRS) with the crystals serving as reactive internal reflection elements. The double-bond reaction has been correlated with in-situ adsorption density measurements. These results demonstrate that only the first chemisorbed oleate layer undergoes the double-bond reaction at an appreciable rate. However, multilayers of precipitated calcium oleate in the case of fluorite appear to react minimally even for oxygen saturated solutions at elevated temperatures.

Jan 1, 1991

By Noel Jarrett

Energy consumption and distribution in aluminum production, conservation accomplishments, and future goals are presented. Electrolysis and electrode manufacture show the greatest promise for major improvements. Means are proposed for reducing waste heat generation in smelting and for conserving energy in anode manufacture by furnace design and substitution of other materials for petroleum coke. Hall-Heroult Process modifications, alternative designs, and the Alcoa Smelting Process are discussed as energy savers. Scrap recycling, more use of aluminum in transportation, and the installation of offshore smelters in less developed countries are shown to be additional means of coping with possible energy dislocations.

Jan 1, 1981

By R. E. Mason

Shotcrete has been used for approximately 20 years to facilitate tunnel excavation through poor ground. Early examples of such usage in North America include the recuperation of the Granduc Mines access tunnel in Northern British Columbia, and similar work performed in the Carley V. Porter and Big Walker Tunnels in the United States. Mining companies such as Craigmont Mines in B.C. and Hecla Mines have used shotcrete in their workings for the past ten years. Shotcrete is now a widely utilized fool in the mining and tunnel construction industries in North America, but the accumulated experience is too limited for many to fully appreciate the capability of shotcrete to control ground movements and to understand the limitations of this tool. It is common, for instance, to use shotcrete to "bridge the gap" between rock bolt-supported and steel-rib supported ground and to avoid the use of shotcrete in water-bearing ground. Shotcrete can, and has been, used economically and practically under most severe ground conditions.

Jan 1, 1976

By R. E. Driscoll

The exploration, geologist of necessity has to have a wide working knowledge of many specialties other than hiw own, First he has to use his own technical background to find a deposit,, of a mineral that is of interest, Once found, his problems are Just beginning, He then has to assume the role of an economist, an accountant, a mining engineer, a chemist, a metallurgist,, a salesman and what-have you, In the economic field, he must determine the marketability of either the ore or the refined mineral. He must gauge the supply and demand for the particular mineral he is interested in and make his best guess as to ultimate cash flow from a deposit over the estimated life of said deposit, He must then assume the role of a mining man and estimate cost of recovery, including an, evaluation of the most economic mining method, cost of supplies and labor, and again estimate a net cash flow. He must then determine amenability of ore to economic metallurgical methods, he must determine the legal status of the property involved and, after analysis of the specific situation, determine the best approach to a deal, After all of this he must sell it to the people who will put up the money and then put his deal together and sell it to the people who own the minerals, if that be necessary. Then he has to sit back, with crossed fingers and crossed legs wondering for some months, and in many cases even years, whether or not he is right. The expenditures required to open up a mine in this day of wild inflation are such that he has to be right, and the responsibilities are awesome.

Jan 1, 1958

By Vladimir Adamek

Due to the variability of subsidence characteristics across the U.S. coalfields, it was concluded that it would be practically impossible to develop a universal predictive model for mining-induced subsidence based on theoretical assumptions. Therefore, an effort was made to find a procedure to develop an empirical subsidence predictive model based on a sufficient Mount of field data from one mining area (in this case the Northern Appalachian Coal Region). It was also thought that this procedure, if successful, could be used as the template for developing predictive capabilities for other coalfields with different subsidence characteristics given a reasonable amount of field data. It has been found, in the Northern Appalachian Coal Region, that the variability of subsidence characteristics can be expressed by a polynomial equation developed through regression analysis of the variable subsidence coefficient and derived directly from the field data. In this study, field data were obtained from 11 Bureau longwall panel studies (16 half profiles) for static subsidence and 14 panels for dynamic subsidence. The effects of lithology, expressed in the form of a variable subsidence coefficient, have been separated for each test site by introducing a correlation between hythetically homogeneous overburden and existing ithological conditions. For each longwall panel, the characteristic of the variable subsidence coefficient was defined along individual static profiles. The definition of mean values with acceptable deviations is the substance of the predictive method. The same procedure was used to develop a predictive model for dynamic subsidence, since it war discovered that the rate of longwall face advance is not a necessary functional parameter. This paper presents the theory, development, and application of the static and dynamic subsidence prediction models.

Jan 1, 1986

By F. N. Earll

4.1 – DEFINITIONS 4.1.1-MINERALS, ROCKS, ORES AND NONMETALLIC MINERALS F. N. EARLL A mineral is a naturally occurring inorganic element or compound. Most minerals are distinctly crystalline in habit, and many commonly occur in well-formed crystals or crystalline aggregates, but a few species are characteristically amorphous or noncrystalline. Nearly 2,000 mineral species are now recognized but, perhaps fortun¬ately, a rather large proportion are rarely encountered. Even so, the application of modern mineral-detection and identification techniques reveals the presence of surprising numbers of mineral species, even in deposits of outwardly simple mineralogy. A rock is an aggregate of grains or crystals of one or more minerals. Some rocks are essentially monomineralic. Thus, limestone consists largely of the mineral calcite, and many sandstones are dominantly quartz. Most rock varieties, however, contain a number of mineral species, and their classification or identification depends upon the minerals present, their relative abundance, and such factors as rock tex¬ture and origin. Ore is defined as an accumulation or deposit of one or more minerals that can be exploited at a profit. The profit criterion commonly is taken somewhat liberally, however, for, although always present, the specific mineral content that constitutes a viable product is transitory. The term ore, usually, but no longer consistently, is restricted to the description of mineral deposits that are of value for their metal content. Nonmetallic deposits, although similar to metallic ores in many respects, generally are valued for the minerals or compounds present, as with rock salt (halite), rather than for individual contained elements, though such minerals as elemental sulfur are of much value. 4.1.2-ROCK TYPES F. N. EARLL Rocks arc grouped tinder three broad headings: (1) igneous rocks formed by the crystallization of magma; (2) sedimentary rocks formed by surface processes of weathering and deposition; and (3) metamorphic rocks, which may have been derived from either of the foregoing, but have undergone important physical and/or chemical changes through the application of heat or pressure, or both. The three groups can he further subdivided for convenient reference. Thus, igneous rocks are described as being abyssal or plutonic if formed at great depth, hypabyssal if formed at intermediate depth, and extrusive or effusive if formed at or on the earth's surface. The sedimentary rock group is similarly subdivided into clastic sediments and chemical precipitates. The clastic sediments form by deposition of preexisting minerals that were released from their place of origin by weathering and were transported to their point of deposition as discrete grains

Jan 1, 1973

By Al. Valero

This paper quantifies in universal units (energy units), the annual decrease in the mineral endowment of the planet. This is done for some important extracted non-fuel minerals, namely aluminium, cobalt, chromium, copper, gold, lead, uranium and zinc and is compared with the depletion figures of conventional fossil fuels. The results of this study reveal that each year, the decrease of the global non-fuel mineral bonus provided by Nature is 2 to 3 orders of magnitude greater than the loss associated to the burning of fossil fuels. Particularly for 2008, the depletion in mineral wealth of the studied commodities was about 20 times greater than that of fossil fuels. The assessment methodology is based on the Second Law of Thermodynamics. It quantifies the useful energy (exergy) required to concentrate a mineral from a completely dispersed state in the crust, to the conditions of composition and concentration found in the mines. Exergy can be a useful measure for quantifying the mineral depletion caused by man, as it takes into account the main physical features that make minerals valuable: composition and concentration. This analysis enhances and puts numbers to the importance and necessity of material reuse and recycling.

Jan 1, 2011

By J. M. Keane

SMEThis loaner is concerned with important criteria relative to the design of small flota¬tion concentrators. For the purpose of this discussion a small flotation concentrator is defined as a facility having a designed ore feed rate of 1,000 metric tons per day (MTPD), or less. The decision to design and construct a small flotation concentrator is the culmination of a series of logical steps relative to the ex¬ploitation of a potential ore body. The information required for a rational and timely decision regarding plant design and construction is usually contained in a feasibility report. The information required in a thorough feasibility report has been summarized (1) (2) as follows: Type of mine or plant and proposed daily, monthly, and yearly production of all intermediate and final products. Quantity of indicated ore reserves. Location of project illustrated by a map showing surroundings, trans-portation facilities, and existing utilities.

Jan 1, 1980

By M. J. Sanzotti, C. J. Bise

This paper examines the potential for controlling longwall-induced subsidence by pneumatically backstowing waste rock into the void created by mining. The paper also examines scheduling the process as a unit operation of the mining activity. Based on a review of background literature and interviews with representatives of various mining companies, public-interest groups and state and federal regulatory agencies, a hypothetical case-study evaluation of pneumatic stowing at a southwestern Pennsylvania mine was conducted. The study indicated that current stowing technology cannot keep pace with the production potential of longwall systems in the United States. Further, at the mine used in this case study, concomitant stowing would reduce subsidence by only 50% of what would normally be incurred during full longwall caving, and the longwall coal-production rate would decrease from 3,630 t (4,000 st) per shift in the nonstowing case to 1,360 t (1,500 st) in the stowing case. A preliminary cost analysis reveals that pneumatic stowing would add from $5.79 to $11.57 per t ($5.25 to $10.50 per st) to the operating cost of producing coal at the case-study site.

Jan 1, 1997

By T. K. McCranie, A. H. Tousley, A. H. Kackman, L. R. Gregory, A. Jr. McElrath, R. J. Krekel

In Roman and earlier civilizations the term cement was applied only to mixtures of lime, pozzolana, sand, water, etc., used as a mortar to bind larger stones. Today, portland cement, the subject of this section, can be briefly defined as follows: The product obtained by finely grinding clinker produced by calcining to incipient fusion (i.e., sintering) an intimate and properly proportioned mixture of argillaceous and calcareous materials. History The Egyptians were probably the first to join building stones with a mixture of sand and a cementitious material (i.e., having the property of or acting like cement). It is generally accepted that the cement used by the Egyptians on such structures as the Great Pyramid was calcined gypsum, Later the Greeks began to calcine limestone for use as a mortar with sand and water. Still later, broken brick and tile were added to the mortar to make the first concrete. The Greeks and Romans found that some sands produced mortars that were especially resistant to the action of water. Hydraulic (i.e., underwater-hardening) cements formed by combining slaked lime, water, and finely divided siliceous materials (e.g., pozzolana) possess superior strength and are capable of resisting the destructive action of water. They were used on the Pantheon, Colosseum, and other structures, some of which are still standing. In 1756 an English engineer, John Smeaton, found that an argillaceous limestone (i.e., containing an appreciable amount of clay as an impurity) produced a cement with greater resistance to the action of water. Despite Smeaton's findings, the use of the old mixture of lime and pozzolana long retained its popularity. Significant contributions in cement technology from England, Swe¬den, France, and Holland were made in the next 68 years. However, the invention of portland cement is generally credited to Joseph Aspdin, an Englishman, who in 1824 patented "portland cement." The name was selected because, on hardening, it resembled the natural building stone from the Isle of Portland, England. The patent features mixing ground limestone and argillaceous materials in appropriate proportions and calcining (i.e., expelling CO2 by roasting) the mixture. This superseded the existing practice of calcining naturally occurring argillaceous limestone. In about 1845 Isaac Johnson, also English, conducted experiments on proportioning the components and calcining them at higher tem¬peratures. His accomplishments are accepted as the beginning of the present-day portland cement industry. The U.S. cement industry originated with the demand for good hydraulic cement for building structures such as the Erie Canal, which was started in 1817. The first discovery of cement rock (i.e., naturally occurring argillaceous limestone with near-optimum ratios of calcium carbonate, alumina, and silica) near Fayetteville, N.Y., was made by C. White. In 1818, White secured a patent for the manufacture of natural cement from that deposit. Subsequently, several natural cement plants were built in 1830-1840 at Rosendale, N.Y., and in the Lehigh Valley of Pennsylvania. David Saylor, who participated in establishing a natural cement plant at Coplay, Pa., in 1850 discovered that a superior cement could be produced by calcining the rock at higher temperatures than hith¬erto. In 1871, Saylor obtained a patent and commenced the manufac¬ture of portland cement. By 1890, there were 17 portland cement plants in the United States with a combined annual output of 62,300 tons. At the end of 1970, the number of plants producing portland cement in the United States (including Puerto Rico) was 169, down from a maximum of 185 in 1967, with total annual shipments of 73.4 million tons valued at $1,298 million. (Fig. 1). In 1970, annual world production of hydraulic cement (which includes pozzolanic materials, hydraulic limes, natural cement, alumina cement, and portland cement, all of which are in current use in various parts of the world) reached 630 million tons (Table 1). Flowsheets of typical U.S. cement plants are shown in Chapter 13. Chemical Composition and Physical Properties It is generally accepted that portland cement clinker consists of a mixture of compounds or synthetic minerals. The four principal compounds are:

Jan 1, 1985

By William R. Bond

The pressure/vacuum lysimeter is being used as an effective vadose zone monitoring device for mining heap leach facilities, tailing disposal ponds and tailing waste sites. Their use has proven reliable for baseline data collection, early warning leakage detection and analyzing geochemical variations in the vadose zone. The lysimeter structure utilizes a closed cylindrical chamber made of PVC or inert material. The soil water intake portion of the cylinder is made of a porous material of low permeability. The application of vacuum or pressure to the unit is via two access tubes from the ground surface. Available soil moisture is drawn by vacuum through porous material into the lysimeter chamber and then collected from the access tubes. Case studies show their usefulness for monitoring around a uranium tailing pond constructed in glacial till material, under heap leach pads and pregnant, barren, and overflow ponds, and investigating the movement of contaminant moisture through old tailing deposits. Relatively easy to install and sample, regulatory agencies and facility operators are accepting and negotiating for their application as a site integrity monitoring device and unsaturated zone research tool. Their use at heap leach facilities lends credibility to solution balance calculations when considering a leachate loss of 5 or 10 percent can make or break a mine's profitability.

Jan 1, 1984

By Allan D. Fernie

Growing interest in pit crushing and conveying is evident from the many articles, technical papers, and new equipment development recently presented. Application of a pit crushing and conveying system is complex, as many factors such as mine design, production scheduling as well as initial and ongoing capital and operating costs must be thoroughly and realistically examined. This paper will address the fundamentals to be considered and review several approaches to developing a total system for a new and existing mine situation. The planning function will be outlined and operating and design criteria defined to interface the mining operation and the pit crushing conveying system.

Jan 1, 1983

By Devraj Sharma

This paper presents technical issues in the design and management of a retorted oil shale disposal site. Major physical and geochemical mechanisms which affect the disposal are: heat transport, moisture migration, chemical species transport, auto-ignition, and mechanical behavior alterations of the retorted oil shale pile. The interaction of these mechanisms and their relative magnitude will affect the environmental behavior of the pile. The paper discusses the coupling between the mechanisms, presents a framework to quantify the processes by laboratory and field measurements, and in addition discusses the use of mathematical models to provide quantitative predictions.

Jan 1, 1981

By Boris J. Kochanowsky

In the mobile crushing unit system trucks are replaced by a conveyor resulting in a "continuous" almost "fully-automated" operation with all its attendant advantages. In consequence, overall operating costs are greatly reduced. Because of the new designs of large mobile crushing units that have been brought on-to the market, the use of these plants has increased significantly during the last three years. This paper describes the designs of new mobile crushing units, and emphasizes the advantages that such plants offer to the rock products and mining industries. It examines operating costs, and indicates the conditions in which the application of these plants is most profitable.

Jan 1, 1968