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By Cloyd D. McDowell

The Federal coal Mine Health and Safety Act of 1969 has been criticized by those who say it goes too far in controlling the activity of private enterprise and by those who say it does not go far enough in eliminating fatalities and accidents in an accident prone industry. Possibly a better evaluation of this legislation lies somewhere in between. From the viewpoint of the coal industry it can be said that through the efforts of those engaged in mining, both the operator and the miner, the year 1969 marked a record year in mine safety with only 190 fatalities and a frequency of 0.84 per million man hours exposure. This outstanding achievement compared to any previous was the result of a determined effort on the part of a concerned industry to improve its reputation as being the most hazardous industry in the nation. After the effective date of the Act, March 31, 1970, the Bureau of Mines assumed complete control of all safety and health activities of the mining industry. Unfortunately, there was no improvement in the safety record of underground mines in 1970 with the total of 255 fatal injuries and a frequency of 1.04 for the year. The number of fatalities declined to 177 in 1971 but the number of underground coal mines had declined from 5,955 to 2,268 during the two year period. Meanwhile, surface mined coal increased from about 38% of total production in 1969 to over 50% in 1971, keeping the annual production of coal at a normal level but involving fewer men.

Jan 1, 1973

By D. Lauriski, E. D. Thimons, A. C. Smith, D. C. Fredley

The National Institute for Occupational Safety and Health (NIOSH) and Northwest Barricade LLC (NWB) conducted a study to evaluate the effectiveness of a novel fire blocking gel for use in underground coal mines to extinguish or retard the growth of a coal fire. The gel agent was subjected to controlled laboratory testing to assess its ability to delay coal ignition. It was then evaluated to determine if manual fire hose application could be used to apply the agent to mine roofs and ribs to provide a safe egress for mine rescue teams from a fire area. The gel agent was also evaluated in a water sprinkler system to determine its potential for use in conveyor belt fire suppression systems. The agent was then tested in live-fire exercises to examine its effectiveness in retarding and extinguishing a deep-seated coal fire and wood fire. Lastly, the ability of a mine rescue team to quickly and safely apply the gel agent to a mine entry during a simulated mine fire exercise was determined.

Jan 1, 2011

By H. E. Rojas, G. T. Adel

The primary objective of most comminution operations is liberation; however, mill performance is generally quantified in terms of particle size. Only recently has the use of image analysis equipment made it possible to quantify mill performance on the basis of liberation. In this investigation, a series of tests were carried out to study the effect of mill operating parameters on the liberation of sphalerite from a sphalerite/dolomite ore. The parameters studied included mill rotational speed, mill loading and ball size. The results of this work appear to indicate that sphalerite liberation is improved under conditions that promote impact breakage, while dolomite breakage is enhanced under attrition conditions.

Jan 1, 1992

By J. Mastoris

The determination of the surface area that may be impacted by underground mining is an important consideration in subsidence engineering. A number of parameters have been utilized to identify this influence area, most notably the angles of draw and break. This paper discusses the implications of selecting an appropriate "damage angle" for defining a potential damage area due to mining, within which surface structures may be impacted. Furthermore, the influence of both mining and geological factors (i.e., mining width, depth and overburden lithology) on this angle is examined using the Surface Deformation Prediction System (SDPS) software. Finally, recommendations are given for applying these concepts in subsidence control.

Jan 1, 1995

By C. Roldan, C. Garcia, J. D. Miller, C. L. Lin

The ultimate recovery in a heap leaching operation is related to the degree of exposure of the valuable minerals in comminuted particles. Recently, high-resolution cone beam x-ray microtomography (XMT) has been used to determine this parameter. XMT technology consists of examining the extent of mineral exposure for each size fraction of ore in 3D, then, by algebraic calculations, the ultimate recovery can be estimated for different particle size distributions (PSD). To confirm the usefulness of the XMT technology for mineral exposure analysis, column tests were performed to determine ultimate recovery using three PSDs for two composites obtained from the copper heap leaching operation at Zaldivar-Chile.

Jan 1, 2003

By A. G. Wylie

The dimensions and shape both airborne and bulk amphibole-asbestos fibers are different from those of both airborne and bulk of cleavage fragments of the amphiboles. These differences are related to the mineralogical properties unique to the habit of asbestos, including the fibrillar structure, small fibril widths and distinctive crystal-lographic faces of fibrils. Criteria for distinguishing amphi-bole cleavage fragments from amphibole-asbestos include mineralogical properties observable in bulk samples and the dimensions of particles collected on air filters. It would be it very helpful to the mining and mineral industry lf these properties were recognized in the regulation of asbestos.

Jan 1, 1987

By A. D. Unsted

The Premier mine has been in existence for over 75 years and is closely woven into the glamour of the history of South Africa. A note on the geological formation of the diamond pipe and the gabbro gives a clearer overall picture of the mine. Mining methods for operations above and below the gabbro sill are briefly discussed. Ventilation arrangements for mining above the sill are briefly described and possible ventilation arrangements for mining below the sill are discussed in more detail. Note: conversions to S.I. units are not exact as rounding has been done.

Jan 1, 1980

By Fred D. Wright

In this paper the principal theories used to design roof bolting systems are presented and discussed. Then the characteristics of various types of roof bolts are presented and finally the interaction between rock and roof bolt characteristics on choice of roof bolts is discussed. Theories can be considered design tools which may or may not be appropriate for a specific situation. It is good for a design engineer to have a number of such tools available and also important that he understand their good features as well as their limitations. Hence, some of the principal theories and classification systems used for design of roof bolting systems are discussed first.

Jan 1, 1982

By W. J. Dolinar, S. P. Sandoval

The US Bureau of Mines (USBM) implemented the Fe2+/ Fe3+-SO2 anode reaction in a Cu-electrowinning cell with full-size electrodes. Electrowinning was conducted using industrial electrolyte at 258 A/ m2 (24 A/ft2) and 40°C. Manifold injection of electrolyte provided circulation between the electrodes. Five-day operation using an optimized manifold gave an average cell voltage of 0.94 V at 89% current efficiency, which amounted to an energy savings of 2.82 MJ/kg (0.355 kW-hr/lb), compared to conventional electrowinning. Acid milling 5was completely eliminated, and the SO2 concentration 23 cm (9 in.) above the cell averaged 0.06 ppm.

Jan 1, 1996

By Antti J. Niemi

Radioisotope tracers have so far been used for extraction of residence time distributions of flotation devices. They have also been proven applicable to evaluation of rate coefficients k of industrial flotation. It is now shown how values of k are scaled up on the basis of laboratory data on flotation and chemical conditioning, and of laboratory testing of samples from output of industrial conditioning vessel. Subsequently a model of conditioning and flotation is obtained which may be used for simulation and control of the steady state of the combined process. Discussion extends to modelling, simulation, CAD and opti- mization of flotation plants with re- circulation, and of ore dressing systems which consist of grinding and flotation plants.

Jan 1, 1990

By C. J. Bise

Continuous mining accounts for about 69% of the nation's underground coal production. This level is not expected to change much in the near future. This is because continuous mining represents the primary means of under- ground coal production. It is also the primary means of driving development entries for underground coal mines, including longwall mines. The continuous miner worksite contains many characteristics that can lead to personnel accidents. It continues to be an area of concern for mine managers, safety engineers, and training coordinators. In an effort to assist mine management in attempts to reduce the number of accidents and injuries sustained in this area, this paper presents a loss-control-based, non-intrusive strategy for conducting safety evaluations at continuous miner worksites.

Jan 1, 1991

By L. J. Prosser, A. T. Iannacchione

From 1991 through 1995, 44 miners out of a total workforce of less than 2,000 were fatally injured in the stone industry. Of these, 12 occurred at underground mining operations with nine deaths resulting from roof or rib falls. A safer environment can be achieved by evaluating the nature of the hazardous ground and by developing more efficient and effective ground-control strategies. Roof and rib conditions were observed and assessed in 33 underground stone mines in Illinois, Indiana, Kentucky, Maryland, Missouri, Pennsylvania and West Virginia (Fig. 1). Hazard assessment indicated that the ground failures that occurred under moderate to substantial overburden, i.e., >30 m (100 ft), were caused by stress concentrations and geologic structures. Ground failures near the surface are caused by solution (water) processes. Selection of the mining horizon and mine-layout decisions

Jan 1, 1999

By Yuuichi Umeki, Yuusaku Tominaga

In order to keep good air condition in any specific branch such as coal face and/or heading in an underground coal mine, effective factors of all the branches with respect to the specified branch have been investigated, using computer simulation. Main results of the paper are as follows; 1) A branch in a network is classified to one of three classes of effectiveness to increase, to decrease and not to change airflow rate in the specific branch by altering aerodynamic resistance in the branch. 2) Distribution of position of branches, belonging to each class, related to a specific branch is one of the macroscopic characteristic of a network which is the inherent property of every network. 3) A relation of the aerodynamic resistances of any two branches to keep a constant airflow rate in the specified branch is shown as a monotonous curve. 4) Ventilation transition diagram with the rate of airflow in the two branches as coordinates, and for different rates of airflow in the specific branch as the parameter, is found to be straight lines. 5) Existing range of airflow rates In the specified branch is given as a parameter in the enclosed area in the ventilation transition diagram. Moreover, an expert system to assist ventilation control using a transition diagram of airflow rate is introduced in this paper.

Jan 1, 1991

By P. Somasundaran, Bruno Lartiges

Two different groups of mechanisms have been considered in the past to explain the effects of chemical additives on grinding. While one group of explanations is based upon alterations of surface and mechanical properties of the individual particles, the other group depends mainly on the arrangement of particles and their flow in suspensions. In this paper some of the past work on grinding aids is reviewed and attrition grinding of a commercially important ceramic material, zirconia (stabilized with yttria) with polyaaylic acid as grinding aid, is studied in order to determine the effect of the aid on the ground product itself. It was observed that even though polyaaylic acid did cause a drastic decrease in the viscosity of the pulp, it did not have any major effect on the grinding of zirconia at least up to 2000 ppm and only minor detrimental effect above it. Importantly, complexation by the polymer was found to cause extraction of yttrium into solution with possibly significant changes in the surface chemical composition of the product.

Jan 1, 1992

By J. A. Herbst, J. E. Bohrer, Y. C. Lo

A systematic approach has been developed to analyze a phosphate grinding circuit with a view toward determining promising alternatives for increasing mill capacity. This analysis was carried out and capacity increases were predicted in the context of detailed population balance models developed for the plant ball mills and classifier systems. Model development and verification was performed using data obtained in a series of batch tests and two plant test campaigns. The effects of feed rate, percent solids, ball size, and mill material filling, etc., on grinding were investigated in the laboratory and plant. Residence time distribution tests were also performed to determine the transport behavior in the mill. The population balance models were found to provide accurate predictions of full-scale grinding circuit performance. Based on the findings of this study, additional capacity in excess of 25% was predicted for these ball milling circuits by a proper combination of ball size change, mill dilution, and adopting screen classification in place of hydro-cyclones. These predictions have been confirmed by plant tests in which the recommended operating changes have been implemented. Understanding the effects of operating variables on breakage kinetics and the interplay between kinetics, transport, and classification has contributed significantly to increasing the mill capacity.

Jan 1, 1988

By R. V. Ramani, K. V. K. Prasad

Forecasting mined grade variability from exploration information is a challenging task in mine planning. For effective planning of activities, such as workplace scheduling, ore grade quality control, etc., development of realistic numerical simulation models of in situ variability from exploration information is an essential first step. Geostatistical conditional simulation (GCS) is one of the well known methods to develop such simulations. Recently, stochastic fractal models based on the assumptions of scale-invariance and self-similarity have been used for developing simulations of several natural phenomena. It has been suggested that these models might permit the generation of short-scale variability information from exploration data with greater fidelity when the data satisfies the attendant assumptions. In this paper, stochastic fractal models are reviewed, and their relationship to geostatistical variogram models is examined. A comparison of the two simulation techniques has been performed using coal sulfur data from a mined-out coal property. The results of this comparative analysis are also presented in the paper.

Jan 1, 1993

By D. Oyler

The National Institute for Occupational Safety and Health’s(NIOSH) Pittsburgh Research Laboratory (PRL), RAG Pennsylvania and Strata Control Technologies of Australia have collaborated to conduct an extensive study of roof bolt strata interaction at the Emerald mine in Southwestern Pennsylvania. The primary goal of the project was to obtain detailed data on the interaction between the mine roof and the support elements for use in modeling studies. The study site was a longwall tailgate subjected to high horizontal stress. Three arrays of instruments were installed at the site, one in the tail-gate entry and two in an adjacent crosscut. Pumpable concrete cribs were present in the tailgate array, and cable bolts were installed in one of the crosscut arrays. The instruments included mechanical and sonic extensometers for measuring roof movement, instrumented roof bolts, and three-dimensional roof stress cells. The study was ultimately successful in determining the magnitude of the horizontal stress concentration, the height of roof failure and the roof failure sequence, and the loading history of the primary roof supports.

Jan 1, 2004

By B. K. Cantrell, D. H. Carlson, W. F. Watts, K. L. Rubow

The use of diesel equipment in underground coal mines is controversial because the National Institute for Occupational Safety and Health (NIOSH) regards "whole diesel exhaust" as "a potential occupational carcinogen." Threshold limit values (TLVs) are recommended for the gaseous pollutants CO, CO2, NO, N02, SO2 and some hydrocarbons emitted in diesel exhaust. There is, however, no TLV recommended for diesel exhaust aerosols (DEA) nor is there a standard method for sampling these aerosols. The University of Minnesota and the USBM have collaborated to develop a personal diesel exhaust aerosol sampler (PDEAS) that utilizes size selective, inertial impaction and gravimetric analysis. During the field tests of this sampler, numerous air quality measurements were conducted in underground coal mines that used diesel equipment. The objective of this report is to present these data and to assess the impact of diesel face haulage equipment on mine air quality. Air quality data were collected in four underground coal mines. The mines used continuous miners and diesel haulage equipment. Daily samples were collected at the section intake, haulageway and on haulage vehicles. Both full-and partial-shift samples were collected using a variety of aerosol instruments. These included the PDEAS and the micro-orifice uniform deposit impactor (MOUDI) that sample the mine aerosol diesel exhaust fraction. Two of the mines were also monitored for the major gaseous constituents found in diesel exhaust CO, CO2, NO, NO2 and SO2. These measurements were made by either collecting bag samples for subsequent gas analysis or by Palmes dosimeters. Concentrations of CO, C02, NO, NO2 and SO2 were well below regulated levels. The mine average DEA concentration determined by the PDEAS in the haulageway for the three mines surveyed was 0.79 mg/m3, with a standard deviation of 0.19 mg/m3. DEA contributed 65% of the respirable aerosol, at this location. These results were the same as the mean DEA concentrations calculated from size distribution measurements obtained using the MOUDI. This was 0.78 mg/m3, with a standard deviation of 0.22 mg/m3.

Jan 1, 1992

By Surendra K. Mishra

The increasing volume of wastes being generated by industry is a legacy of the industrial revolution and subsequent industrial growth. Social and regulatory pressures have been mounting on industry to improve its waste management practices. In many industrial sectors, waste disposal has been the only method of waste management. Land farming, underground burial, deep wells and incineration are still practiced. Often, concentration and volume reduction of waste streams are also practiced to reduce the waste management costs. In the recent years, there has been emphasis on waste minimization. Since the 19th century, industry has practiced recycling of usable resources as a way of handling unwanted byproducts. The mining industry has recovered or extracted economic minerals from tailings for decades. For example, during the gold rush period of 1970s, extraction of gold from tailings dams became economically attractive. Similarly, when it was economical, coal and shale fractions have also been recovered from tailings and refuge materials for commercial uses. In the steel industry, with the development of new furnace technology, recycling of flue dust and scrap iron was practiced as early as in the 19th century. Before 1900, there was little incentive for the industry to reduce the waste volumes. Manufacturers, however, did see a rationale for adopting profit-increasing techniques. They made an effort to recover and recycle economic materials from waste sources. One of the pioneering examples of resource recovery is the coke making industry. As the industry was market driven, products recycled from coke batteries included ammonia for use in fertilizers, gas for power generation and heating, and tar for road construction, wood preservation and roofing. Tar had been avery troublesome waste byproduct. But it quickly became a valuable chemical raw material, providing the foundation for Germany's dominance of the world's dye and medicine markets before World War I. Similar trends evolved in the chemical industry. In the context of current environmental regulations and escalating mining and processing costs, recycling of re- [ ] sources is becoming economically more attractive. Solid and liquid wastes generated by industries contain a range of inorganic and organic contaminants. Among these contaminants, metals and hydrocarbons form major groups. Treatment of these wastes is essential to meet regulatory disposal requirements. In the recent years, based on the principles of chemical and mineral process engineering, processes have been developed to treat these industrial wastes. This article reviews some of the processes that have made impacts and have proven to be effective at commercial scales.

Jan 1, 1999

By Sue Sawyer

In October, November and December, teachers at the National Science Teachers' Association (NSTA) area conventions were lured to visit the Minerals Education Coalition (MEC) booth by the promise of free rocks, video tapes, and literature on earth science topics. Teachers were content to stand in lines that at times took as much as an hour and a half to progress through the exhibit. Adding to their interest was the opportunity to converse with people from the minerals industry who were staffing the booth. The MEC was formed by a group of associations and companies in the minerals industry. They felt the need to educate the public about the current-day minerals industry and how it affects everyone's life. The American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. (AIME) underwrote the major expenses of exhibit space and exhibitor services at all three conventions in 1997. SME members have been active in staffing and chairing the NSTA exhibit booth. But they represented only about one-third of the volunteers for the booth. Additional volunteers were drawn from local minerals companies, associations, interested teachers and other support groups. (See donors list on page 64.) In 1997, the conventions were held in Pittsburgh, PA, Denver, CO and Nashville, TN. The local SME GEM Committees chaired Pittsburgh and Denver and The Rogers Group Inc. supplied the chairperson in Nashville. Each exhibit relies on a local committee to plan and run the booth. Support is available from the GEM Projects Coordinator at SME headquarters. Usually the chair of the committee is drawn from the local SME membership. It is easy to see why the MEC booth is so popular. Free literature, videos, posters, workshop packets and rock specimens were handed out to about 5,500 science teachers at the three sites. Feedback from the attending teachers was overwhelmingly positive: "Who do we thank for these great materials?" Some of those great materials included Caterpillar's outstanding donation of Common Ground videos and teacher packets for Pittsburgh, Denver and Nashville for every teacher expected to attend. Placer Dome sent enough What's a Mine coloring books and It Comes from a Mine activity books for teachers at all three sites. Newmont supplied all teachers with an excellent poster describing gold processing. Women in Mining Education Foundation had plenty of its classroom activity handouts. The American Coal Foundation provided a list of its educational materials that are given out free to teachers who request them on school letterhead. The National Mining Association had its Facts About Minerals and Facts About Coal available. US Borax provided the funding to reproduce the NMA black and white posters that were published as inserts in Mining Voice magazine. In addition, each site had other materials chosen by the local committees to round out their selections. At each exhibit site, committees raise between $8,000 and $12,000 in cash donations from industry to support the high overhead of producing this exhibit. Usually, there are between 12 and 18 different rock specimens representing a range of mineral ores from aggregates to the metal ores. The committee arranged to have these donated (along with the freight charges to ship them to the site). Literature is also donated by the industry. It covers a diverse spectrum from basic information on rocks and minerals to posters, flow charts, videos and coloring books. Other donations include storage space before the event, haulage of items to the hall and door prizes. These exhibits could not have been staged without the network of SME Local Sections and the able chairs and committees at each site. At this time, credit should be given to their extensive donation of time and effort.

Jan 1, 1998