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By T. G. Bobick

Task analyses were conducted by the Bureau of Mines at four underground low-seam coal mines to evaluate their supply-handling systems and for use in subsequent design of laboratory simulation experiments. Items were tracked (by videotaping) from delivery to the surface storage areas to their final destinations underground. Of particular interest were those tasks that required manual handling of supplies or equipment. Analysis of the videotapes revealed that the miners handled materials while stooped over a total of 37.8 pct of the time, 31.5 pct while on both knees and 9.5 pct while kneeling on one knee. These working postures impose considerable stress on the lumbar spine and may be implicated in the high number of back injuries in this work population. This paper also discusses various mechanical-assist devices developed by the Bureau and successfully evaluated in the underground workplace. These devices can be used to minimize the manual effort and the corresponding risk of injury associated with handling supplies and equipment components in low-seam coal mines.

Jan 1, 1988

By L. Borsch

Geochemical laboratories are commonly criticized by geologists about poor analytical reproducibility and erratic anomaly patterns, especially when gold and trace metals from resistant minerals are reported. Geochemical analysis in mineral exploration is a compromise between high productivity on the one hand, imposed by large numbers of samples, and analytical precision and accuracy on the other. However, the physical properties of resistant minerals, such as cassiterite, gold, beryl, chromite, zircon and others, interfere with both of these requirements. Therefore, the degree of sample homogeneity that can reasonably be achieved in sampling and sample preparation must be considered. Subsequently, the understanding of its effects on analytical data quality and the consequences on data interpretation will provide a basis for understanding the problems common to exploration as an interdisciplinary science. Complaints about poor and inadequate analytical performance are not confined to exploration geochemistry. They are a common feature in mining and metallurgy and wherever sampling and analysis of "grains" are concerned - the "nugget" or "grain size effect." The "grain size" effect Poor analytical reproducibility is normal for gold and a well-defined group of other elements usually found in resistant placer minerals. Those who use and interpret geochemical data must realize and appreciate the chemical, the physicochemical, the physical and the mineralogical properties of the elements and their minerals. Especially for the "placer" minerals and their elements, such comprehensive interpretation is crucial. The most important factor to consider is the behavior of a mineral and its metal component(s) during weathering and their integration into the sampled medium, in exploration mostly sediments and soils. (Data interpretation for samples of water, gas, to a certain extent rock, follows different patterns.) A mineral may be chemically and physically stable or it may easily disintegrate physically or decompose chemically, or any combination of such processes, at varying degrees. The breakdown products, in turn, may or may not, interreact with the environment. If the nature of an element or a mineral predestines it for a heterogenous distribution in the sample medium, then nature, size and number of grains likely to occur should be considered in relation to the sample portion taken for analysis. This allows the estimation of their effect on analytical precision and accuracy. Elaborate and sophisticated statistical calculations exist on this subject. But these approaches do not cope with the complexity of the natural surface environment. The miner alogical, chemical and environmental behavior of elements and minerals can be estimated but not calculated. However, the mineral grain sizes and their influence on analytical precision can be precisely calculated if certain conditions, assumptions and idealizations are made. If the geochemical and mineralogical characteristics of minerals and elements are understood, such calculations demonstrate the grain (or nugget) effects that mineral properties and (geo)chemical behavior of minerals and elements cause on the precision and accuracy of geochemical analysis through their influence on sample homogeneity. Two other factors that influence the sample homogeneity and the nugget effect are the efficiency of sample preparation and the sample portion taken for analysis. In this way, certain element- or mineral-specific parameters can be established as a guide for the sampling program. The information, for example, may assist in determining sampling procedures in the field, especially the sample weight to be taken for "representative samples." Also, it may help assess whether analytical data, as provided by the laboratory, are acceptable. Finally, it may help determine the approach in data interpretation. However, all such simplified calculations are based on idealized, that is, unreal assumptions and conditions. As such, they represent one extreme end on the scale of probabilities. The reality is found somewhere away from this extreme, towards homogeneity. An example from a study of an eluvial gold prospect may be given for illustration: •Original sample weight: 20 kg (44 lbs) of rock gravel, crushed and ground to -0.18 mm (-80 mesh). •Au content: 20 grains of Au, average size of about 0.5 mm3 (0.03 cu in.) each = 7.5 mg each, making a total of about 150 mg Au in the sample = 7.5 ppm Au. Assumptions •Au occurs in the sample as free, discrete grains only. •Not more than one grain, if any, goes into each sample split (analyte) portion (20 grains of 7.5 mg Au each). •Analysis of original rock sample: 100 g sample for analysis, 20 kg/100 g = 200 samples 20 samples with 1 grain each: result, - 75 ppm Au. 180 samples with no grain: result, 0 ppm Au chances 1:9 •10 g sample for analysis:

Jan 1, 1996

By D. Weston

During recent years there has been a great deal of confusion in the North American mining industry with the introduction of new comminution terminology and claims (without substantiative evidence), for various types of equipment in this field. The authors will attempt to clarify the terminology used, and where possible, give illustrations of plant practice with actual operational and pilot plant data. This is considered necessary in order to obtain a clear picture of the comparison of such equipment to the revolutionary change that the Aerofall Mill has brought to the mining industry.

Jan 1, 1964

By R. Matikainen

Since the Brundtland Commission in 1987, the use of natural resources has been an issue of global concern. Minerals are among the most important Earth resources and will definitely be essential for the development of societies also in future. Increasing scientific effort is needed not only to discover new deposits, but also to promote resource management in ecologically and socially sound way. Sustainable resource management is essentially a multidisciplinary challenge of developing life-cycle analysis and recycling of non-renewable resources from local to global scale. It offers great opportunities for geological surveys not only in EU, but all over the world to contribute positively to the welfare and sustainability of societies.

Jan 1, 2003

By Karl-Heinz Bruemmer, Karl Wollers

1- Importance of Shafts for the Exploration and Extraction of Coal Deposits Coal mining in the Federal Republic of Germany is carried out in a depth between 800 and 1200 m below sea level (Fig. 1). The shortest connections underground in a mine and up to the surface are vertical shafts. Such shafts assume, with ventilation, manriding and the winding of material, the most important functions for the maintenance of mining operations. In the German coal mining industry, a difference is made between the main shafts providing a direct access from the surface to the deposits, and the so-called "blindshafts" which serve as a connection between two or several haulage levels underground. [ ]

Jan 1, 1976

By L. G. Austin, R. C. Klimpel

Batch breakage kinetic tests were performed in a mill of 0.3 m diameter for a range of mill conditions. Accurate simulation required the measurement and use of factors which accelerated the specific rates of breakage of the top sizes as finer material accumulated in the slurry. These factors depended on the size distribution expressed relative to the top size, not the absolute size, suggesting that they are due to a packing effect not a rheological effect. The data simulated correctly a series of steady-state continuous tests in a mill of the same diameter providing values were corrected to the hold-up, ball load, slurry density, and size distribution measured in the continuous mill tests.

Jan 1, 1990

By Edwin J. Connell, O&apos

Investment in mining and related process facilities will be more costly and complex in the 1980s than ever before. Interest rates and inflation are soaring; regulations are expanding; and in order to achieve economies of scale, plant facilities and mines are getting larger. As the pace quickens, the time/cost circuit closes around the resource owner or developer. Larger modern projects cost more money and take more time to build. The longer it takes to bring a project onstream, the more it costs in interest, escalation, and lost production. One solution to the time/cost squeeze is to take advantage of systems developed by major contractors serving the mining industry. These contractors have been serving clients in planning and executing large and small projects for many years. They have developed systems which, if applied at an early point in the project's life, can be a significant benefit in development of mineral resources. The systems involve performance of feasibility studies, economic evaluations, and the project installation itself. First the Feasibility Study Feasibility studies can minimize risk through systematic evaluations while progressing toward the ultimate objective-an operating plant. Normally, studies are initiated with a minimum amount of specific information and a maximum number of as¬sumptions. Through the course of the study program, assumptions are continuously confirmed, refined, or rejected by facts until a sound basis for decision is available. High on the list of cost effective tools for evaluation is the use of a geostatistically derived sampling program that provides a highly accurate ore reserve estimate for economic evaluation. When a predetermined sample of data from the drilling program and bench-scale or pilot-plant tests are received, a detailed feasibility study may be started. This study can involve design of the mine,

Jan 10, 1980

By D. Hodouin

The improvement of mineral processing data using material balance computer programs is nowadays a current practice in many plants, engineering companies or research centers. It now becomes more obvious that such programs should integrate new features such as the preprocessing of data, the estimation of less accessible process variables and an in-depth interpretation of: the computed results. A few solutions to these new problems are already available. The feasibility of a mass balance computation for instance can be examined by analyzing the degree of redundancy of the measurements prior to any data adjustment. New variables such as chemical analyses in particle size intervals or liquid phase composition can be included in a set of measurements. Finally, a sensitivity analysis can be used to analyze the reliability of the results, to detect eventual outliers or to redesign a sampling scheme. Some illustrations of these new developments are presented.

Jan 1, 1989

By G. D. Hood, C. E. Jordan

The US Bureau of Mines investigated rapid froth flotation through more efficient bubble-particle collisions that improved the overall flotation kinetics. An in-line static mixer efficiently mixed the bubbles, water and ore, selectively attaching these bubbles to the hydrophobic mineral's surface. As the mixture entered the flotation chamber, the hydrophobic mineral was already attached to the bubbles and was quickly floated away from the remaining ore pulp. The rapid flotation system was evaluated for beneficiation with a western porphyry copper ore containing 0.67% copper and with a phosphate-bearing amine flotation tailings sample containing 9.5% P2O5 in a quartz matrix. Over 88% of the copper was recovered from the ore in a rougher concentrate containing 5.9% copper at a rate seven times, faster than conventional flotation. Sixty percent of the quartz in the phosphate-bearing sample was floated at a rate four times faster than conventional flotation. The unfloated product retained 80% of the phosphate in a 16.9% P2O5 concentrate.

Jan 1, 1994

In underground coal mining, one of the biggest challenges is spontaneous combustion, which will not only present safety hazards but result in reserve losses as a result of burnt coal. The released heat coupled with other combustible gases commonly encountered underground will significantly increase the risk of explosion. In this paper, three-phase foam as an environment-friendly fire fighting agent composed of nitrogen, water and fly ash is introduced. The nitrogen facilitates inertization of the fire zone; the water helps cool down the fire and the fly ash can closely cover the coal to isolate the oxygen. What's more, the fly ash and the foaming agent are good free radical absorption. The comprehensive merits mentioned above make three-phase foam quite effective in quenching spontaneous combustion. Experiments indicate that three-phase foam can significantly slow down the temperature rise of coal during oxidation. The comparison between slurry and three-phase foam shows that the latter one is capable of flowing upward in the porous media so as to extinguish the high-point fire and concealed fire.

Jan 1, 2011

By S. Nickson, M. Grenon

Oriented borehole data provide the means to characterize a rock mass. In this paper, the geomechanical caving potential of a hard rock mine project is investigated. In particular, the influence of random joints to the resulting block size distributions is addressed. The implications of this approach in preliminary investigations on the choice of mining methods are discussed with reference to one site.

Jan 1, 2003

By Alireza Ayoubian, Richard Finno

The network of freight tunnels in Chicago consists of about 62 miles of horseshoeshaped tunnels constructed typically less than 50 feet below ground surface. These tunnels serve as repositories of much infrastructure and should remain serviceable. The tunnels are often impacted by adjacent excavations and the question arises as to the existing state of stress in the final liner. This paper discusses construction of these tunnels and presents the results of finite element analyses which were used to obtain ranges for axial forces and bending moments that have developed in the final liner of the freight tunnels since their construction.

Jun 13, 2023

By T. Lupek, S. Plaum

"The execution of classical building services in underground mining operations is more truth than myth. From small concrete foundations for conveyor belts to the construction of huge workshops for large machinery maintenance, nearly every operation requires building services. By creating such fixed facilities, these services ensure the efficiency of the production. A distinction must be made between fixed facilities which directly enable the production and auxiliary facilities which only indirectly support the production. The construction costs of such auxiliary facilities are often roughly estimated because they do not immediately contribute to mineral extraction. The research project ‘Development of a systematic cost-calculation method for building services in underground mines’ seeks to address the question: ‘Can the construction costs concerning fixed auxiliary facilities be neglected e.g. within a prefeasibility study?’ The presentation will show the monetary relevance and significance of these auxiliary facilities and introduce a guideline for cost estimators. PROBLEM DEFINITION The overriding interest of an underground mining operator is to exploit the commodity with the maximal quality by minimum cost and time expenditure. If a new operation shall be installed, it has to promise profitability. Therefore, predictive economic feasibility studies are performed in advance of installation. Herein, all cost expenditure for installation and operation of the future underground mine is determined and compared to the expected income by selling the raw material. The described interest of the mining operator is the starting point of the research project ‘Development of a systematic cost-calculation method for building services in underground mines’. While economic feasibility studies for future operations are focused on the profitable exploitation of raw materials and the efficiency of the accompanying necessary production processes, auxiliary actions are only considered rudimentary. Necessary production processes, as well as auxiliary actions regularly require classical building services, which are normally performed in construction business on the surface in the same manner. By performing building services like masonry or concrete works in underground mines, fixed facilities shall be set up in order to enable or support the raw material production. Production enabling fixed facilities are varying from small concrete foundations for conveyor belts or other infrastructural elements to upstream processing plants situated in the mine workings. While such fixed facilities are essential parts of the production process chain, supporting facilities underground shall increase the efficiency of the mining operation. Workshops, control rooms and social installations are only a few examples for supporting facilities. Those could be situated on the surface as well, but the efficiency increases significantly by installing them underground. Especially supporting facilities are evading from the main interest of the mine operator, since they are only indirectly connected to the production process. The building costs are oftentimes only roughly assumed."

Jan 1, 2017

The Kinross DeLamar Mine has been operated for more than 17 years producing precious metals dore' from ores, principally silver bearing with associated gold co-products. In late 1995 a new orebody was commissioned, the Stone Cabin orebody, and the site began a phased shift from silver dominance to gold dominance in terms of precious metals revenue. The Knelson Concentrator was selected to remove gold from a portion of the cyclone underflow stream in the grinding circuit. This paper describes the development of the flow sheet, specific mineralogical impacts on Knelson product and downstream materials, and impacts on mine/mill grade reconciliation.

Jan 1, 1997

By Anshumali Gangwar

This paper outlines the chance constrained binary integer program developed by the author in his doctoral dissertation at Columbia University, New York, 1973. The optimum planning of a mining program involves the determination of a production schedule which maximizes the net present value of the mining property. The actual mining process has an inherent stochastic and discrete nature. In particular, the demand for the mined product and the grade of the mineralized material in the ore are the two most important stochastic mining variables. The decision to mine or not to mine any block of a mining property is a binary integer variable. This paper outlines the formulation of pit production scheduling problem as a chance constrained binary integer program. The deterministic equivalents of these chance constraints are nonlinear in binary variables which have subsequently been linearized. The planned objective is to meet with a stipulated high degree of reliability, all the random demands as they materialize with a random supply of the commodity being marketed as determined by the eventuating random grade values of the exposed ore blocks and the mining system's production constraints such that the discounted total production costs over the entire planning horizon are minimized or the profits maximized. The emerging surface of the mine in each scheduling period is determined by the values taken by the binary decision variable associated with each block of material in each scheduling period.

Jan 1, 1982

By Mehmet Guney

Acceptable working environments in production areas and service openings of Mindola Mine on the Zambian Copperbelt are currently maintained with an air volume of 1000 cu m/s and 5500 kW of installed refrigeration plant. It is planned to open up additional deeper areas of the mine for future production. Temperature problems, due to the increased heat generation from various underground sources are recognized as potential hinderances to efficient production. Findings of research work indicate that the present total heat output of 58,000 kW will inevitably increase by the second five-year period of the deepening program to 52,900 kW and by the fifth five-year period to 63,200 k\V. Estimated WB and DB temperatures, representing the total heat generation in stope faces and development headings during these same periods are predicted to increase to 53.8/40.2 °C and 35.5/42.1 °C respectively. It is assessed that the nominal refrigeration capacity needs to be progressively increased to 9,000 k\V This paper deals with the thermal problems in Mindola Mine, current heat output calculations, future prediction of temperature and heat load in various working areas of the mine with the application of computer programs and interpretation of data in order to find the effective solution for long-term planning of ventilation and air-conditioning.

Jan 1, 1982

By T. Takamori

This paper reviews the present status of coal preparation in Japan concentrating on the process in coal cleaning and waste water treatment. This paper also discusses recent topics on maintenance, automatic control, raw coal management, etc.

Jan 1, 1982

By Julia R. Budden, Peter A. Spencer

Bacterial oxidation processes have often been repo1ted as releasing large amounts of energy so that a large scale operation would require cooling to maintain the required operating temperature for the bacterial culture. These reports are based on the chemical heat release which in some eases has been adjusted for the energy required to fonn the mass of bacterial cell matter per unit volume of solution. There are two flaws in this approach for calculating energy release in the fonn of heat. The first flaw is that it only considers the bacteria in solution. The second assumption is that the only bacterial reaction is the fonnation of cell material and others such as energy for respiration and locomotion are not considered.

Jan 1, 1992

By G. Gaidajis

Sea water samples collected from coastal waters in the vicinity of the Stratoni mining operations, in North-Aegean Sea were analysed for dissolved metals and elements. The maximum concentrations observed were one to three orders of magnitude lower than the environmental limit which coincides with the quality of sea waters suitable for swimming purposes. The quality of the coastal sea waters are affected by the natural mineralization of the area and the urban activities drained through local small rivers, the past mining activities present in the sea bottom sediments in the form of disposed tailings, and finally by the presence of the adjacent Mill-Flotation Plant. The relative importance of the treated final effluents discharged from the mining operations is considered to be insignificant.

Jan 1, 2006

By Raj K. Singhal

Canada produces close to 42 million tonnes of coal per annum of which some 38 million tonnes is produced by surface mining methods. The two Western Canadian provinces, Alberta and British Columbia, produce 31 million tonnes of coal by surface mining. These two provinces provide the bulk of the metallurgical coal for export. The geological conditions in the Western provinces particularly in the mountain region are complex. The coals are friable and the seams are steeply inclined, sheared, intensely folded and faulted. There may be as many as 15 to 20 coal seams present with true thickness ranging from 2.5 m to over 8 m. This paper reviews the surface mining methods used to extract such seams. The difficulties associated with steep seam and multiple seam mining of friable coal resulting in lower coal recovery, high dilution and the problem of cleaning fine coal in the wash plant have been highlighted.

Jan 1, 1984