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By Christopher Mark

Sixty years ago, underground coal mining was the most hazardous job in the United States. Roof falls killed about 100 miners every year, more than all other causes put together. Fast forward half a century to 2016, and the first year ever with zero roof fall fatalities. Just three miners were killed by roof falls during the following six years. To understand how this historic goal was achieved, this study analyzed hundreds of roof fall fatality reports covering five decades. It found that the immediate effect of the Federal Coal Mine Health and Safety Act of 1969 (Coal Act) was to reduce the riskiest activities, like needlessly going under unsupported roof. Other hazards, like large roof falls, required technological developments before they were brought under control. Roof control plans, which the U.S. Bureau of Mines had been advocating since the 1920s, fostered the necessary improvements in both the safety culture and the mining technology.

Jun 1, 2024

By Boghani. A. B.

A computer program has been developed to simulate evacuation of a mine in various configurations. The simulation input variables include characteristics of the mine, expressed, in the form of a network of passages, properties of hoists and hoisting strategies, initial miner positions, ventilation and compressed air velocities, stench warning system and self rescuer capabilities. The simulation can be carried out for cases in which there is no fire, i. e. , fire drill simulation, or for cases in which there is a fire at any arbitrary location. The fire is assumed to generate gases which impede movement of miners in the gaseous region. However, the thermal effects of the fire are not considered. The simulation output include the evacuation time for each miner, movement of the hoists, propagation of smoke through the mine passages and smoke exposure of the miners. Several illustrative simulations have been carried out to verify validity of the program and to demonstrate its capabilities. The computer program has been able to predict evacuation time, within 5 percent, for an actual fire drill. It is believed that this program can be used to evaluate evacuation performance of a mine, identify problem areas and demonstrate improvements due to the recommended corrective actions.

Jan 1, 1977

The dissolution kinetics of gold in iodide solutions with oxygen in an autoclave was investigated. The leaching process was described by a gas-liquid-solid heterogeneous reaction. The effect of stirring speed, temperature, partial pressure of oxygen, and concentration of lixiviants on the overall leaching rate was investigated. It was found that the dissolution of gold was limited by a heterogeneous chemical reaction. The apparent activation energy was measured to be 34.7-54.3 kJ/mol under the conditions studied. Experimental findings were in good agreement with the kinetic model proposed.

Jan 1, 1996

By M. P. D. Ingunza, Júnior Santos, F. S. D. Araújo, A. L. C. Araújo, J. Y. P. Leite

Wastewater sludge is a problem for environmental control and it is necessary alternative researches for its reuse. Industries can research the association of clay and sewage sludge as a source of ceramic mass. This procedure can contribute for the industry sustainability including in its raw materials, wastes of environmental concern. This paper presents the results of sewage sludge and clays characterization being analyzed particle size distribution (sedimentation), mineralogical (X-ray diffraction), chemical composition (X-ray fluorescence), thermal analysis, density, and Atterberg proprieties (liquid and plastic limit; plasticity index) and also their applications in ceramics. Results were used to determine moisture for mass of raw material and sewage sludge and there were realized tests of fired in kiln at temperatures used in ceramic industry for bricks production. In the test pieces were analyzed the properties for application as bricks.

Jan 1, 2005

By C. E. Stack

For the purposes of this presentation, "refractory clay" is intended to include any clay suitable for refractory products and thus represents a description based on industrial application. Other common examples based on use would be white-ware clay, bleaching clay, paper clay, or cement clay. Most users and producers of refractories have specific quality requirements which determine the quality or type of clay that can be utilized. Many clays can however be interchanged or substituted in use by changing manufacturing processes or upgrading less desirable clays. U.S. Bureau of Mines publications (Ampian, 1985) categorize days into six groups. These are kaolin, fire clay, ball clay, bentonite, fuller's earth, and common clay. These are practical groupings based on clay production and usage in the United States. Among these groups bentonite, fuller's earth, and common clay are primarily composed of the minerals, smectite, illite, or chlorite, and are non-refractory. Kaolin, ball clay, and fire clay are commonly used in refractories and thus qualify as refractory clays.

Jan 1, 1986

By D. G. Purdy

Planning, as defined in Webster's New Collegiate Dictionary, is a detailed program of action designed to achieve an end. When developing a detailed plan to incorporate all the complex activities involved in a surface lignite mine, many elements must be carefully evaluated as to the individual and cumulative effects on the end result. The following elements are generally evaluated when planning a surface lignite mine: ? Reserve evaluation, including lignite quality characterization; ? Delineation of mining parameters, including lignite recovery factors, geotechnical factors, land control factors; ? Selection of mining blocks; ? Pit sequencing; ? Reclamation, including soil reconstruction design and land use planning; ? Overburden handling design; ? Selection of equipment; ? Sizing of equipment; ? Manpower requirements; and ? Other elements, including contract negotiations and execution, financing, investment return, operation economics, permitting and scheduling.

Jan 1, 1985

The last time Mining Engineering presented an issue with a special focus on Canadian Mining (ME, August 2008 pp. 28 to 40) things were going well. A feature story took a look at Xstrata?s Nickel Rim South Mine in Sudbury and the booming Canadian oil sands were discussed at length. Potash prices were soaring, large diamonds were being found and British Columbia was launching plans to find more workers. How things have changed in six short months. What began as a mortgage crisis grew into a credit crisis, then mutated into a financial crisis, that has taken its toll on the value of bonds, loans, stocks, real estate and commodities. Miners that were flying high on unprecedented commodity prices six months ago have begun scaling back with delays, shut downs and layoffs as they struggle to survive this most recent economic downturn.

Jan 1, 2009

By T. P. Meloy

In the last decade increased and prolonged interest has been displayed in the use: of tunneling or rapid excavation to solve many of the urban and industrial problems confronting our society. There has been talk and action on the interurban rapid transit systems for major cities, and even preliminary designs for a Boston to Washington interurban transit system. Much of this interest stems from the search to the solution of our increasingly complex urban problems, where the surface area must be given over more and more to the inhabitants, and the subsurface for transit, utility and other services. While tunneling is not a panacea to urban ills it holds a real solution to many existing problems. There is also, among the tunneling experts, a growing confidence that technical problems of rapid tunneling can be solved. To solve these problems, R & D money must be invested. If it is to be money invested either by private industry or governments, there must be significant returns on the investment to justify the research and development need to bring about the breakthrough that will make tunneling a major contribution to the solution of urban problems. To make these economic studies more extensive and more accurate tunneling demand figures were needed. To this end, the Organization of Economic Cooperation & Development - OCED - included in its Conference on Tunneling a section on tunneling demand. As a result of the conference the organization for Economic Cooperation and Development issued a report entitled "The Advisory Conference on Tunneling - Report on Tunneling Demand 1960-1980. " This report was presented at the OCED Conference on Rapid Excavation, held at Washington, D.C. To obtain the data in the Report, questionnaires were sent to the OCED countries and 18 replies were received from Australia, Austria, Belgium, Canada, Denmark, France, Germany, Ireland, Italy, Japan, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, United Kingdom, and the United States. While it is true, that data were missing, that sometimes the definitions were confused, and that several countries provided no cost estimates at all, in general, this report contains the most comprehensive gathering of data that ever existed in the field. All data in the OECD report is expressed in terms of meters or cubic meters, and costs are in U.S. dollars.

Jan 1, 1970

By J. L. Ellenberger

The U.S. Bureau of Mines has cooperated with Cyprus Casa Grande Corporation Cyprus Casa Grande Mine, Cas a Grande, Arizona, since 1988 to assess the hydrology of an in situ leaching test facility. This work has resulted in an in situ design for leaching copper oxide ore that takes advantage of the increased mineral access associated with poor quality rock surrounding mine drifts. Blasting and bulkheads are used to produce readily-leachable rubble and contain and control solution movement, respectively. The design reduces the need for handling solution under high pressures in an injection/recovery system for in situ leaching of underground ore bodies. Early work at the site recognized a stress redistribution zone and increased transmissivity near drifts. Fracture data from a corehole oriented parallel to the dip of the ore body indicated an increase in fracture frequency around drifts a distance of 21 m (70 ft) away from the 5 m (16 ft) diameter drifts.

Jan 1, 1994

By E. G. Loesche

Grinding mills in which the comminution takes place between rollers and the surface of a disc, table or ring are generally known as roller type mills. The Loesche Mill, also known as the Disc Roll Mill, is a special type of roller mill in which the grinding surfaces consist of two rollers assembled over a horizontal disc or table which rotates at a relatively low speed. This design is particularly applicable to industry's present day demand for large capacity grinding mills.

Jan 1, 1964

By R. K. Will

An inactive mining operation in northern California is known to be a source of acid mine drainage and heavy metals which have impacted adjacent creeks. Elevated concentrations of copper and zinc are a concern to aquatic populations, particularly steelhead trout and salmon downstream in the Sacramento River. Previous regional geological surveys of mineralization by the U.S. Geological Survey located and mapped outcrops of massive sulfides and gossan. Recent investigations indicate that a substantial amount of the metals in the local creeks are due to natural causes. The investigations include locating and mapping surface and subsurface minerals, soil and water sampling, and chemical analysis. Groundwater, seeps, and surface water were also sampled and analyzed. A water balance was conducted on a sub-basin level following delineation of surface water drainage and groundwater divides. A chemical mass balance incorporated metal concentrations and water volumes and was then used with other data to determine the contribution of metals from natural versus mining-related causes.

Jan 1, 1998

By J. A. Herbst, H. R. Cooper, R. J. Brison, R. W. Harper, K. P. Ananthapadmanabhan, W. C. Hellyer, B. H. Bergstorm, D. M. Hopstock, H. Rush Spedden, W. C. Hellyner

Scope of Section The physical characterization of an ore or mineral mixture in such detail that mineral processing may be effectively applied to create more useful products is one part of the technology of sampling and testing. In addition, the evaluation of the multitude of separation processes, both physical and chemical, combined with ancillary opera¬tions and performed on samples at a laboratory scale, is another part of the testing procedure. Although analytical techniques provid¬ing quantitative determinations of elemental compositions are an im¬portant and necessary supplement to any testing program, that field of endeavor is a well-developed, separate entity beyond the scope of this Section. Sampling procedures cover the practice of selecting representative quantities of test materials in the field to evaluate mineral deposits, and extend to techniques of obtaining process samples in slurry and bulk ore as part of process evaluation. The same techniques are appli¬cable, of course, to standardized methods of metallurgical accounting. Sampling is also an important facet of successful on-line measurement of slurry properties such as assays and particle size in the practice of automation. However, the sampling methods in this case can be different from those needed for precise testing and accounting pur¬poses. Sampling was well defined in Taggart's Handbook as "the opera¬tion of removing a part convenient in size for testing, from a whole which is of much greater bulk, in such a way that the proportion and distribution of the quality to be tested (e.g., specific gravity, metal content, recoverability) are the same in both the whole and the part removed (SAMPLE). The conditions of the more stringent definition, that the sample shall be completely representative of the whole as regards all aspects save bulk, are practically never fulfilled when heterogenous mineral mixtures are sampled." Taggart's Handbook of Mineral Dressing, Section 19, "Sampling and Testing," continues to be a very useful compendium of principles and techniques, particularly as applied to manual methods for han¬dling samples. In the intervening years since its last revision, substan¬tial progress has been made in both the theory and the techniques; thus, this current contribution is designed to be an extension of the earlier work, yet complete enough to provide procedural guidelines to methods of continuing validity. Although basic principles of testing remain unchanged, the meth¬ods of applying those principles have undergone great change. New testing equipment has become available, yielding a greater precision of results. Testing methods have been refined which, in many cases, allows for a valid scale up of flowsheet designs without the necessity of costly pilot or prototype plant development. Justification for a Sampling and Testing Program* The proper evaluation of a mineral property is a complicated process. It often is done on a team basis with the exploration geologist, mining engineer, mineral process engineer (extractive metallurgist), economist, and product utilizer (ceramist, chemical engineer, chemist, metallurgist, etc.) all represented. The mineral processing engineer is a key member because he can provide a go no-go answer to the question, "Can this ore be processed economically?" In addition, his judgment on the response of even the initial sample to processing can be an invaluable guide to the proposed process and its mutations. Since the capital investment and operating costs are so sensitive to the type of process used, the judgment of the mineral processing engineer forms an important part of the early evaluation of the profitability of a new mining venture. This early estimation of the processing approach is all the more important since, for some metalliferous ores, the capital investment for mill, smelter, water supply, and tailings disposal exceeds the cost of the mine. At present, for commodities such as coal, the reverse is true. There is a smaller capital investment for the coal preparation plant than for the mine. In general, both the capital and operating costs escalate very rapidly in the following order: gravity concentration of alluvial deposits (e.g., dredging), gravity concentration of lode ores, flotation, simple hydrometallurgical processes, and complicated hydrometallurgical and pyrometallurgical processes. The latter two processes may cost 100 to 1,000 times more per ton treated than processing of a simple alluvial deposit. This dictates that the valuable mineral be concentrated as much as possible to minimize the total tonnage treated in the more expensive operations. Within each of these ore-processing categories there is a wide range of process sophistication and hence of capital and operating costs. Perhaps the greatest variations are in the chemical processing of ores. These range from the simple leaching of a copper waste dump to very sophisticated hydrometallurgical processing of ores in increasing order of cost. Because the overall cost of a mining venture is so sensitive to the process selected, it is essential that the mineral¬ processing engineer evaluate the ore in the initial stages of the development of an ore body. As better samples become available, he must continually revise his estimate of the process to be employed. The sampling and testing process must be a necessary and continuing activity throughout the life of a project. One fundamental aspect of nearly all mineral deposits is the inherent variability of the mineral assemblage and composition. A utopian goal of any processing plant is to have the process so flexible and so well-defined that an automatic process control system can optimize the economic recovery at all times. Since this is rarely possible, a continuing or at least a periodic testing program is desirable. Variables to be considered are: 1) Ore body inconsistencies. 2) Zonal variations. 3) Feed variations from mining plan or methods. 4) Variable performance of processing units due to wear. 5) Seasonal or other changes affecting processing conditions such as water quality, temperature, etc. 6) Changing market conditions for product quality or byproducts. 7) Technological advances in processing methods or equipment. 8) Increasing demands for environmental control. 9) Changing economics of competitive processes, of supplies, of capital investment vs. labor costs, etc. Sampling Procedures Preliminary Guidelines for Sampling Ore Deposit Studies. t At a very early stage, it is essential that the mineral processing engineer receive a sample of the ore. This may be a portion of the diamond drill core or a split from the trench, pit, churn drill, channel, or sheet sample. Even a grab sample may have some value, but it should be selected by the mining engineer or exploration geologist to be as representative of the ore body as possible within his best judgment. The sample delivered to the process engineer should have been subjected to as little prior crushing as is practical since fine sizes are difficult to concentrate. In addition, finely ground ores are readily oxidized and thus may give misleading test results. Furthermore, ground samples may make it impossible to eval¬uate either the comminution or the coarse-gravity concentration pro¬cesses. For an initial evaluation, a good deal may often be learned from a sample of only a few pounds if that is all that is available. To obtain the maximum information from a sample, its selection should be carefully discussed with the mineral processing engineer. In addi¬tion to being as representative as possible, the mineralogically distinct samples should be carefully segregated rather than composited. Since drastically different processes are often needed to process samples of differing mineralogy, considerable care and time must be exercised during this sample collection step. The segregation of samples showing gross mineralogical differences, such as the oxide caping on a sulfide deposit or a laterized zone, is easy. It is the more subtle changes in mineralogy that can often elude the field man. Yet these differences are often sufficient to dictate that an entirely different type of process be used. Obviously, the selection of these initial samples for ore testing and mineralogical studies requires that it be done by a man of consider¬able experience and judgment. While the mining engineer or field geologist is collecting these samples, he should also note and convey to the processing engineer such details as water quality and availabil¬ity, terrain, potential mill location, tailings-disposal areas, case of transportation, etc. As the property is developed with additional drill holes, adits, etc., larger and more representative samples will be required to develop the ore-processing flowsheet more adequately. If pilot-plant studies are required, a very large sample may be necessary. Though the type and amount of sample collected for flowsheet development investigations vary widely, gathering a representative sample of the ore body is a prime requisite for any process development effort. The process developed for any given ore body is only as reliable as the sample on which the flowsheet was based¬

Jan 1, 1985

By S. L. Manske

The Mesquite gold deposit is a recent discovery of Gold Fields Mining Corporation lying 65 kilo- meters northeast of El Centro in Imperial County, California (Figure 1). The deposit is located on the southwestern flank of the Chocolate Mountains and is a bulk-minable, low grade "disseminated" orebody. Although the host rocks of the deposit are part of a regional high-grade metamorphic terrane, abundant brittle fractures, brecciation, and open-space vein fillings indicate that Mesquite mineralization is epithermal. Faulting which postdates the hydrothermal activity has complicated the original geometry of the orebody. Alluvium effectively hides most surface expression of the mineralization, but open-pit mining is now revealing the details of Mesquite geology.

Jan 1, 1987

By Douglas J. Lacke

1974 marked the start of a new era for Climax Molybdenum Co., a division of AMAX, with the initiation of an open pit operation above the existing successful underground block panel caving mine. A number of problems posed a challenge to the Climax open pit. Highly fractured rock, old mine workings, permafrost, and more than 7.6 m/a (300") of snowfall forced changes in normal operations. Final pit wall design was altered. Production bench heights were lessened due to old workings. These and other modifications contribute to a highly successful open pit operation.

Jan 1, 1981

By Kent D. Gastreich

As the number of prime surface coal mining sites diminishes with time and with the potential for increased coal demand, areas that were previously not mined because of their difficult mining conditions, marginal economics, and controversial environmental nature, will have to be considered if surface coal mining is to continue in the future. Such sites include areas near major rivers, streams, and lakes. The name most commonly given to these areas by regulatory agencies is "wetlands". The exact definition(s) to the term "wetland" will be discussed later in this paper. Most coal operators are now more than familiar with permitting requirements under the Surface Mining Control and Reclamation Act of 1977 (SMCRA). The SMCRA permanent regulatory program recognizes the fact that coal mining operations will periodically encounter streams, wetlands, etc. Although discussed in various sections of the permanent program regulations, the relationship of coal mining operations to wetlands is particularly evident in the performance standards regarding hydrologic balance and protection of fish, wildlife and related environmental values.

Jan 1, 1980

By David B. Costain

Three dimensional surface approximations are important means of evaluating physical and environmental factors that affect surface coal mining and reclamation. Computer approximated surfaces are projected as an array of square grid cells where individual cells define each parameter value respective to locations on the grid. Grid surfaces or grid cells within a surface can be compared or modified through application of standard mathematical functions. Surface approximations can be used to define the quantity and quality of marketable coal and to evaluate thickness and quality of overburden. Surface approximations also can be used to evaluate overburden swell factors wherein changes in post-mine topographic relief are related to expansion of unconsolidated materials in the backfill. Application of computer approximated surface to analysis of approximate original contour (AOC) standards allows an assessment of the quantity and geographical displacement of overburden and the distribution and numerical level of slope.

Jan 1, 1984

By J. J. Zaluski

The Surface Mining control and Reclamation Act (public Law 95-87) (here-inafter the "Act" or "SMCRA") passed by congress in August of 1977 represents a comprehensive federal scheme for controlling surface coal mining and the surface effects of underground mining through permitting requirements, performance guidelines, and reclamation planning. While the provisions of the Act have been the subject of numerous legal challenges and court battles over the years, it is difficult to identify a more controversial program within the Act than the provisions for designating lands as unsuitable for surface coal mining operations. The lands unsuitable designation process provides for the acceptance and review of petitions submitted by citizens or organizations seeking to have specified land areas designated unsuitable for all or certain types of surface coal mining activities. In filing these petitions, the interested parties or petitioners are required to make allegations about potential adverse impacts on people or the environment and submit evidence supporting their allegations.

Jan 1, 1992

By M. R. Carter

The Rochester Mining District is located some twenty-five miles NE of Lovelock, Nevada. The District was discovered and named in the 1860's by prospectors from Rochester, New York. For a number of years, they worked Rochester Canyon, sinking shafts and inclines and making open cuts. After reaching a depth of approximately eighty feet, the miners tapped an underground channel and were driven from these workings by a strong flow of water leaving pumps in the shaft and barely escaping with their lives. With the Rochester workings no longer accessible, the miners went to the southeast and established the Relief Mining District. About 1881, gold was found in the gravel at the mouth of American Canyon, to the east of Rochester. These placers were worked until 1895, first by the Americans who reportedly took out $1 000 000, and later by the Chinese who mined the gravel with great skill. It was estimated that the Chinese took out as much as $10 000 000.

Jan 1, 1987

By L. M. Gochioco

The U.S. coal industry is under-going dramatic changes to meet the challenges of the keenly competitive fuels market. The application of innovative technologies is needed to improve safety and to increase productivity in order to make coal more competitive as a fuel. As more coal companies shift into capital intensive longwall mining, there is a clear need to invest more in exploration before mine plans are made. Coal seam anomalies may create adverse mining conditions. The early detection of these anomalies could make the longwall mining safer and more productive through improved planning. A standard exploratory drilling program can provide only limited geologic information. The seismic reflection technique can be used to detect coal seam anomalies and is effective in reconnaissance surveying. Recent advances in the quality of coal seismic data have increased the success rate of seismic surveying. Therefore, surface seismic surveys, coupled with selective drilling, will come to play an integral role in coal exploration in the 1990s.

Jan 1, 1990

By S. N. McIntosh

Column bioleaching was evaluated by the U.S. Bureau of Mines as a means of recovering manganese from a low-grade ore from the Three Kids deposit in Southern Nevada. Manganese was solubilized from the ore using indigenous heterotrophic microorganisms. Diluted molasses medium was provided as nutrient for the microorganisms. The medium was recirculated through the ore bed until the sugars were spent. Two methods were evaluated to recover manganese from the sugar depleted bioleaching solution: (1) adsorption with a weak cation exchange resin followed by stripping and precipitation techniques, and (2) direct precipitation of the manganese using ammonium carbonate. Both methods removed up to 95 pct of the solubilized manganese from the medium as a carbonate salt. After manganese removal, the medium was replenished with fresh molasses and recycled back through the column. More manganese was effectively leached. This process of manganese solubilization and recovery followed by replenishment and recycling of the medium was repeated until 98 pct manganese was extracted from the ore.

Jan 1, 1993