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By R. Hogg, E. Kaya

The presence of agglomerated particles in airborne dust in coal mines has been confirmed by SEM examination of static samples collected on substrates. In addition, the effect of agglomerated particles on the performance of cascade impactors and cyclone- type personal samplers has been studied. Simple procedures have been developed for evaluating the extent of agglomeration in air-borne dust by comparing the observed size- selectivity of the sampling devices with that expected under idealized conditions. Applications of these techniques in the laboratory and in underground mines are discussed.

Jan 1, 1992

By R. Simon

Strain-burst phenomena are generally characterised by sudden releases of energy in a volume of highly stressed rock. Strain bursts are encountered in situations such as crown pillar bursts during cut-and-fill mining, face bursts at development headings cord floor bursts in deep shaft sinking. This paper describes a simple two-dimensional linear elastic FE modeling approach that leads to the calculation of the energy-release rate (ERR) and the total energy storage rate (TESR) in the rock-mass around the openings. The merits of using such energy parameters in the analysis of strain-burst problems for identifying areas of high energy release/storage are discussed through a case stud v. However, much site-specific back analyses are needed to better understand how strain bursts and energy parameters are interrelated.

Jan 1, 1999

By D. A. Day, H. L. Marsh, P. J. Stephens, C. A. Wiggins

Lightweight cellular grout backfill behind pipe-in-tunnel has been gaining increased acceptance in the tunneling industry and has proved to be both practical and economical. Two successfully constructed projects, the Upper Scioto West Interceptor Sewer (USWIS), in Columbus, Ohio and the Benbrook Pipeline Tunnel Project in Fort Worth, Texas will be discussed. The projects represent two different but successful applications of lightweight cellular grout backfill. The USWIS placed the grout behind precast reinforced concrete pipe, in water bearing limestone, and in close proximity to residential water wells. The Benbrook Project placed grout behind 6,096 meters (20,000 feet) of steel pipe from just two locations, eliminating major surface disruption typically associated with the placement of pumped concrete.

Jan 1, 1999

By Gilles A. Tremblay

Acidic drainage has been long recognized to be the largest environmental liability facing the Canadian mining industry and to a lesser extent the public through abandoned mines. The Mine Environment Neutral Drainage (MEND) Program was the first initiative formed in 1989 to develop scientifically-based technologies to combat acidic drainage. This 9-year volunteer program reduced the liability by several hundreds of million dollars and established Canada as the recognized leader in research and development on acidic drainage for metal mines. MEND 2000 is a three-year program that started in 1998. The key to MEND 2000 is technology transfer- providing state-of-the-art information and technology developments to users. MEND-developed technologies are being verified by long-term monitoring of large-scale field tests. Maintaining linkages with a number of foreign government and industry-driven programs is also important to the successful completion of the program. Through these efforts a further reduction of the environmental liability associated with acidic drainage will be realized.

Jan 1, 2000

By C. J. Hall

The simplest natural ventilation cycle is similar to a Joule or Brayton cycle. This comprises two reversible adiabatic processes in the shafts and constant pressure processes underground and on surface. The thermal efficiency of such a cycle is given by the temperature increase in the downcast shaft divided by the absolute temperature of the air at the bottom of the downcast shaft, and is independent of the temperature increase underground. This efficiency is comparable to the Carnot efficiency, which is the greatest possible value between constant temperature reservoirs, source and sink. Two variations of the Joule cycle are investigated, using numerous work examples. In the first, dry air is used as the working substance, a fan is provided at the top of the upcast shaft, and various mass rates of flow are used with frictionless shafts and a constant resistance value in the horizontal mine workings. The lost work less the fan work gives the natural ventilation work, and this divided by the enthalpy increase in the workings gives the thermal efficiency. The thermal efficiency increases dramatically with mass rate of flow, although the enthalpy increase remains constant. This appears to violate the second law of thermodynamics, since the frictionless case has a Carnot efficiency. When the lost work is added to the enthalpy increase, however, the efficiency decreases slightly from the Carnot value, to conform with the second law. This increase in efficiency with mass rate of flow is often referred to as the reheat effect, although the air is not heated. The second investigation is similar to the first, except that the air entering the downcast shaft contains a small amount of water vapor, and there is evaporation in the mine workings only, until the air entering the upcast shaft is saturated. There is, of course, condensation in the upcast shaft. In this case, it is not possible to calculate the Carnot efficiency, but the thermal efficiency is 20 to 40% of the similar dry air values. This decrease is much more than can be accounted for by the larger value of specific heat for water vapor. In addition, the natural ventilation work is almost constant with increased mass rate of flow, and the thermal efficiency based on heat addition tends to decrease. The thermal efficiency based on heat and lost work decreases in conformity with the second law. The reasons for the differences in behavior between dry and moist air are not readily apparent.

Jan 1, 1991

By Thomas H. Wake, Timothy M. Tower

A continuing trend in raise drilling is the movement toward increased automation. This paper discusses the reasons for automating a raise drill, which include labor saving, faster and smoother operation, quicker response to blocky ground, and improved data logging and diagnostics. It gives a "wish list" of features when automating a raise drill, from simple shutdown control through unattended operation. It discusses the principles involved in closed loop control of a sluggish mining machine with large inertia, and covers functions such as data logging and remote control. Results are presented from a field test on a production raise drill.

Jan 1, 1991

By Dr. George W. Annadale, Dr. Adrian G. Chantler

Materials which are likely to produce Acid Rock Drainage (ARV) can be identified with a reasonable degree of certainty. However, it is not currently possible to predict the concentrations of future contaminant discharges with similar confidence. One way of overcoming this problem is to model the uncertainty in knowledge related to estimates of future contaminant concentrations, and utilize this information in a decision model to decide on acceptable levels of expenditure on ARV control measures. The paper presents a risk modeling approach and proposes a decision model.

Jan 1, 1992

By B. K. Baird, P. C. Satchwell

The application of cutoffs during and after pit optimization is examined for a lower-grade multimetallic copper deposit. Pit optimization requires calculation of the net revenue associated with each mining block. The calculation incorporates parameters such as metal prices, grades and expected recoveries, mining and processing costs, smelting and refining charges, and penalty element and royalty charges. Sensitivity analysis during pit optimization reveals which parameters have significant effects on the total contained resource tonnage and total contained nondiscounted revenue in the optimized pit. The cumulative effects of changing several of the more-significant parameters are investigated The application of a copper cutoff grade to a block inside the optimized pit could result in the less-than-optimal extraction of the resource. A block with a copper grade below the applied cutoff could be economic due to the presence of other metals. Conversely, a higher-copper-grade block may be subeconomic. Also discussed are the merits of applying a copper-grade cutoff, an "equivalent-grade" cutoff and a dollar-per-ton cutoff to blocks inside the optimum nit.

Jan 1, 2002

The visible portion of accounting-record keeping and preparation of financial statements-suggests a lack of sophistication and imagination. In reality, accounting is based on a large body of theory. Accountants philosophize, theorize, judge, create, and deliberate as a significant part of their professional practice. The subjective aspects that are so critical to current accounting practice, such as searching for truth and fact, judging what is fair presentation, and considering the behavior induced by presentations, are often overshadowed by the appearance of exactitude, precision, and objectivity that accompanies the use of numbers to express the financial results of the enterprise. * Fundamental accounting principles are hypothesized in the same manner as mathematical principles. These principles are justified by acceptability and intuition. Accounting theory is built upon these hypotheses, resulting in a coherent set of standards and rules. Although it does not specifically address every situation that may be encountered, this conceptual frame- work enables the manager or analyst to resolve specific situations. This framework also aids in the understanding and confidence in financial statements and ensures comparability between statements from different companies. This framework is referred to as "generally accepted accounting principles," or GAAP.

Jan 1, 1999

By S. G. Malghan, V. K. Pujari

Detailed characterization of all the powder constituents during powder processing is necessary for the reproducible manufacture of ceramic components that will perform reliably in intended applications. In this paper, selected physical and surface chemical techniques for characterization of silicon nitride powder are evaluated. The characterization data are discussed in the context of how these data, through their influence on powder processing unit operations, can affect the final microstructure. In the forming of ceramics, some of the major variables of injection molding are evaluated. Accurate measurement and control of these variables is emphasized for manufacture of Si3N4 ceramics with a high degree of reliability.

Jan 1, 1990

By Terry Owen

Business development process. Throughout Cyprus Amax's early months in Russia, the company stayed focused on what was needed from a deposit for economic success. Cyprus Amax's reason for success in Russia is that all involved - its Russian partners, the workforce and expatriates - provided a focused effort that served the project as it worked through the tender process and the Russian regulations. The company developed an understanding of the regulatory process by working with solid, ethical partners. Infused into the Kubaka management structure were Russians with the knowledge to facilitate the process and a professional group of expatriates. Developing credibility and a solid rapport with the Russian mining authority was critical to the success of this venture. Identifying and gaining the trust of key Russian individuals was also critical during the early stages. Gaining their trust and building credibility was part of the process. These key Russians were brought to the United States to visit existing Cyprus Amax mines. These efforts proved valuable in building an understanding with the Russians about the kind of company Cyprus Amax is and the kind of efficient operations that it can run. This was a learning process for all parties. Fortunately, the company was dealing with intelligent and educated people.

Jan 1, 1997

By J. P. Allen, D. A. Rice, H. L. Abercrombie

Cobalt, nickel and manganese can be recovered quickly, cleanly and selectively from cobalt-rich manganese ocean crust by leaching in dilute acid solutions in the presence of hydrogen peroxide. Common selective precipitation methods can then be used to recover these metals from the leach liquor. The leaching reaction produces only oxygen as a byproduct, and the waste residue from leaching was tested and found to be nonhazardous under existing EPA specifications. The leaching process is effective in either fresh water or seawater. This research is a part of the Bureau of Mines program to identify the mineral resources of the Exclusive Economic Zone and devise methods, for recovering their valuable components.

Jan 1, 1992

By R. J. Sweigard, R. V. Ramani

Estimated costs and revenues can be used in evaluating postmining land use alternatives. However, postmining land use decisions have to be made in an environment complicated by several additional factors. These factors, including cultural, natural, and managerial issues, are not as easily quantified as costs and revenues but may be more important determinants. There fore, some approach is needed to attach relative weight to the various factors. The concept of fuzzy sets assembled into a structured hierarchy facilitates analysis of the relative value of individual factors and their impact on each alternative under consideration. In this paper, a method is presented that employs fuzzy set analysis to evaluate postmining land use plans on the basis of these nonquantitative factors.

Jan 1, 1988

By S. R. S. Sastri

By using the data of E.A. Hersam and F.C. Bond's equation for energy consumption in comminution, a method was developed to analyze the performance of industrial jaw crushers. The study showed that industrial jaw crushers are generally operated below capacity. The study also showed that industrial jaw crushers generally have sufficient installed power to operate at, full capacity. The method presented can be used to estimate the capacities and power requirements of jaw crushers.

Jan 1, 1995

By S. Liu

A general account of nitrogen-generating systems, including the surface fixed, surface-mobile and underground-mobile types is presented. These systems have recently been adopted in coal mines in China to prevent and extinguish fires. The paper stresses nitrogen -injection technology and relevant systems of monitoring and stopping air leakage.

Jan 1, 1998

By S. A. Abetel Sabour

In this work, the block theory was applied to determine the safe limit of the angle of face slope at Limestone quarry of Assiut cement company in order to decrease the occurrence of dangerous potential key blocks. Four joint sets were observed and measured at the face. Computer program based on the vector analysis technique was developed to determine the removable block codes. Stereographic projection was also used in this work to determine the removable block codes and to calculate the maximum limit for the angle of dip of the free face, which was found to be 77°.

Jan 1, 1998

By T. H. Udayashankara

Soil pollution, a very serious environmental problem, has been attracting considerable attention in recent years. It is now generally recognized that land as a component of the environment deserves the same attention and protection as water and air. This recognition has arisen perhaps because of increased incidents of land pollution, the scarcity of land, and increased awareness and concern about long-term effects of land pollution on terrestrial and aquatic eco-systems and on ground water quality. Contamination of land results from a wide range of human activities, including industrial discharge process, disposal of wastewater and agriculture. The environmental impact of exploration, production and refining of crude oil is a major concern in developed and developing countries. Because of the known adverse effects of petroleum hydrocarbons on soil ecology and fertility there has been growing interest in the development of efficient technologies for the remediation of contaminated land, with a view toward making it available for further use. Crude oil is a natural product and as such is susceptible to degradation by naturally occurring micro flora. Bioremediation has become an important method for the restoration of oil-polluted environments. A bench scale study was conducted to evaluate the bioremediation technique in treating soil contaminated with transformer oil. The steps involved in this study are: (1) Preparation of contaminated soil, (2) Extraction of PAHs and PCBs from contaminated soil, (3) Treatment of contaminated soil in slurry batch reactor, and (4) Analysis of PAHs and PCBs by gas chromatography technique. The performance of reactor was assessed by measuring parameters like COD, PAHs and PCBs. The study was con-ducted for six different pulp densities ranging from 20% to 40%. The maximum removal of PAHs and PCBs was observed for 20% pulp density.

Jan 1, 2008

By William C. Cox, Ronald E. Heuer, Jean-Michel Loignon

The Gatineau shaft described in this paper was an excavation of about 38 m diameter and 21 m depth constructed in Gatineau, Quebec, across the Ottawa River just north of Ottawa, Ontario. A large sewage lift pumping station-was to be constructed in this excavation. Subcontractor for the shaft excavation and initial support was Beaver Underground Structures Ltd., of Dorval, Quebec. Mr. William C. Cox of Beaver conceived the idea for the support system used in this excavation, and was responsible for the construction activities. Initial analysis and design concepts for the lining system were developed by Mr. Ronald E. Heuer. Detailed lining design and construction monitoring were the responsibility of Mr. Jean-Michel Loignon. Geologic conditions indicated by two borings within the shaft area are illustrated in Fig. 1. The shaft excavation would be in the sensitive Leda silty clay. The clay is of stiff to very stiff consistency, with an insitu vane shear strength averaging about 115 KPa (2400 psf) and a reported low value of about 87 KPa (1820 psf). Low strength values were from the middle of the clay layer, with higher strengths at the top and bottom. Average shear strength at the level of the base of the excavation was about 137 KPa (2860 psf). Remolded vane shear strength averaged about 20 KPa (420 psf), with a reported low of 13 KPa (270 psf). Based upon average strength values, the clay sensitivity is 5.8. The clay has an average water content of 53% (range 43 to 66%), which is near its liquid limit (average 56%). The clay unit weight is about 1760 kg/m3 (110 pcf). Underlying the shaft site at shallow depth is limestone bedrock within which the piezometric head is approximately equal to the original ground surface elevation. For shaft support, a -cast-in-place concrete wafer system was considered, but was discarded because of time restrictions imposed by concrete placement and curing. The support system selected utilized liner plate with light steel walers closely spaced. The light rib

Jan 1, 1983

By John A. Herbst, William T. Pate, A. Edward Oblad

Dynamic optimization is a cost-effective means to increase production or improve product quality in a plant. Several model-based approaches to dynamic optimization of mineral processing operations have been developed and implemented in plants. This paper reviews the phenomenological models that are the basis for dynamic optimization and the alternative methods of mathematical optimization. These methods range from theoretically complex and costly to implement to intuitively comprehensible and readily implemented.

Jan 1, 1990

By Nelson R. Shaffer

Glamorous, burgeoning biotechnology and mundane industrial minerals would at first glance seem to share little in common, but in truth, modern biotechnology depends on many minerals. Biotechnical processes also can be used in industrial mineral extraction and processing. Biotechnology is broadly defined as the application of biological organisms, systems, or processes to manufacturing and service industries. Genetic engineering has reinvigorated one of mankind's oldest sciences, biotechnology, into a booming business. Many modern processes depend on microorganisms cultivated under very stringent conditions in bioreactors. Minerals from carbonate, sulfate, chloride, nitrate, phosphate, and silicate families are used to provide essential nutrients and to regulate growth conditions (such as pH) in order to assure optimal growth of organisms. Certain cells or enzymes perform better when immobilized upon or within solids, and minerals are often used to immobilize cells, especially in continuous process. Minerals are also used extensively in separating and purifying products of biotechnology. Diatomite, zeolites, and silica are especially useful in purification processes. Industrial minerals also are commonly used to clean up large volumes of process water that must be treated. Biotechnology can be employed in exploration, extraction, and processing of geologic materials and in reducing mining or other environmental problems through bioremediation. Microbes have been shown to solubilize certain elements and so promote extraction of heavy metals, phosphate, aluminum, potassium, and even rare earth elements. In a related technique, unwanted materials such as pyrite impurities can be leached microbially to produce cleaner products in sand and clay industries. Microbial actions can modify surface characteristics and so enhance certain ceramic properties. Certain organisms can accumulate useful elements from dilute sources; others can transform unusable chemical species to more useful forms. Deterioration of stone, concrete, and even glass or brick, can be accelerated by microorganisms. Control of such biodeterioration could improve long-term performance of industrial mineral products. Microbial processes have shown promise in improving several mine-related problems. Certain bacteria help remove clays from phosphate slimes and other suspensions. Others are used to degrade cyanide or other organic chemicals such as floatation aids. Cells immobilized on clays have been especially efficacious in bioremediation. Biotechnology industries, like the industrial minerals industries, encompass huge ranges of materials and processes. Costs of products from these industries range from pennies to thousands of dollars per unit, and their products are vital for maintaining modern life styles. Many biotechnical processes depend upon industrial minerals and certain biological processes can be harnessed to do useful tasks in the minerals field. The interplay of industrial minerals and biotechnology is important today, and as biotechnology advances, its interaction with the industrial minerals industry can only increase.

Jan 1, 1995