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By A. De Daio, D. W. Fuerstenau, P. C. Kapur

Because of its pronounced tendency to undergo visco-plastic flow, coal ground in the energy- efficient high-pressure roll mill invariably comes out as a briquetted product which must be disintegrated in a conventional type of grinding device such as the ball mill. The aggregates comprise comminuted coal particles that are apparently extensively cracked and weakened during passage of the coal through the high-pressure rolls. Their deaggregation in a ball mill in the second stage is accompanied by further grinding of the coal with a relatively small expenditure of energy. Thus in spite of energy dissipation in briquetting in the roll mill and in disintegrating the briquettes in the ball mill, significant energy savings are possible in the fine grinding of coal in a two-stage serial grinding mode, as compared to ball mill grinding alone. It has been determined that for the best results the energy invested in the two grinding stages must be apportioned in an optimal manner, the energy consumption in the ball milling step is comparable to, even in excess of, the energy spent in the high- pressure roll mill; and 20 to 50 percent energy savings might be possible in grinding coal to minus 200-mesh size by this two-step process, as compared to conventional milling.

Jan 1, 1995

By G. Récoché

For the African continent promoting a sustainable utilization of its mineral resources could be considered as a key determinant to fight against poverty. Sustainable development performance indicators for measuring the economic, environmental and social impacts of mining activity are necessary for drawing up policies and sectoral actions, identifying and controlling risks, identifying and implementing sustainable development actions, negotiating between stake-holders, improving mine production, etc. To respond to this need, the SIGAfrique Network proposed to develop a joint decision support tool entitled the African Mining Observatory (AMO) and, to this end, develops a system of indicators to be integrated within the SIGAfrique database. The development of both the OMA and the indicators is based on a participatory method within the working groups, which comprise experts/participants from the 13 SIGAfrique partner and observer countries (Guinea, Burkina Faso, Mali, Tanzania, Niger, Mozambique, Kenya, Uganda, Senegal, Angola, Madagascar, Ethiopia, and Mauritania).

Jan 1, 2007

By M. A. Bothwell

The purpose of this paper is to describe the methods used to select mill discharge screens, and to outline factors which should be taken into consideration when choosing screens for this application.

Jan 1, 2001

By H. I. Morrison, A. J. deVilliers, D. T. Wigle, H. Stocker

INTRODUCTION At the end of 1959, high levels of radioactivity attributed to radon and its daughter products were discovered in the fluorspar mines at St. Lawrence, Newfoundland. These levels were presumed to be the cause of an unusually high incidence of lung cancer among the fluorspar miners (deVilliers & Windish, 1964) (Parsons et al. 1964). The mining of fluorspar (calcium fluoride) began in 1933 as open pit operations but converted to standard underground mining procedures in 1936. During the second world war, production was greatly expanded as a result of increased demand for fluorspar used in the production of steel. Wet drilling was first introduced into general use in 1942. Ventilation was mainly by natural draft occasionally supplemented by small blowers. The amount of ventilation varied greatly between mines as well as over time. For example, one large mine, the Iron Springs mine, had only a single small raise to the surface some 600' from the central shaft. Other mines, such as the Director mine, had a number of raises to the surface and, as a result, had far better ventilation. Mines also varied by the amount of ground-water which seeped into them. In the early 1950's, an unusually large number of lung cancer cases were diagnosed among the fluorspar miners. As a result, in 1956 and 1957, J.P. Windish of Canada's Department of Health and Welfare tested for possible causative agents in the mines. Unfortunately, radon measurements were not conducted until 1959 and 1960 when Windish tested Director mine as did the A.D. Little company in 1960. As a result of the high radon levels found, mechanical ventilation was introduced and the concentration of radon dauthers fell, on the average to well below 1 WL. During this period, lung cancer cases continued to be diagnosed with 29 lung cancer deaths recorded by 1964 and 71 by 1971. As of July 1981, 105 lung cancer cases had been identified (Hollywood, 1981). Previous reports concerning the fluorspar miners have dealt in detail with the factors in the occupational environment and discussed occupational mortality patterns. The purpose of this paper is to review further the mortality experience with particular reference to lung cancer in relation to cumulated radiation exposure and to describe briefly our ongoing study of this group. METHODS Occupational histories were prepared for men who had been employed by the mining companies at St. Lawrence during the period 1933 to 1977. The histories were compiled from company records except for the period 1933 to 1936, records for which were lost in a fire; however, the occupational histories for this period were completed by searching census records and interviewing company officials, ex-employees and others. In addition, occupational and smoking histories were also obtained for some miners during a survey conducted in 1978. Occupational records included name and date of birth as well as the type, place and hours of work by year. For each year prior to 1960, hours of work were converted to working months (1 WM = 167 hours) and were multiplied by the estimated average radon daughter concentration in working levels (WL) to yield the annual radiation exposure in working level months (WLM). Pre-1960 radiation levels were estimated on the basis of the history of mining methods employed, ventilation history of the mine, type and place of work and conditions under which the first radiation measurements were made in 1959 and 1960 (deVilliers and Windish, 1964). During the period from 1960 to 1967, the average exposure was about 0.5 WL. Beginning in 1968, radiation levels were measured more frequently, and, beginning in 1969, daily exposures for each worker were recorded based on radiation levels in the place worked on a given day. Mortality data were obtained from medical certificates of death. In a small number of cases, medically certified death certificates were unavailable. In these cases, probable cause of death were obtained from forms completed by the local clergyman (returns of death), parish records, information obtained from interviews with family members of the deceased and/or hospital information, before assigning a cause of death. Data obtained from these sources were found in Tables 1, 2 and 4, cover the time period 1933 to 1971. Data in Table 3 as well as in Figures 1 through 3 cover deaths from 1933 to 1977, and includes only those miners for whom medical certificates of death were available. Two medically certified causes of death were changed from other causes to lung cancer on the basis of pathology reports.

Jan 1, 1981

By F. C. Eberhardt

Systematic planning of underground work is increasingly important in this era of advancement of rapid underground excavation techniques. The day when planning consisted of deciding which men would shovel and which would push wheelbarrows - and the answer to any problem was more men - has faded into the past. The modern underground constructor faces economic and competitive conditions which demand exacting planning, logistics and scheduling; the most efficient operating methods and equipment known; and realistic, comprehensive, analytical risk evaluation with adequate contingencies or other protection. Proper planning to cover all these elements - plus one other element: old fashioned "good luck" - will insure a successful underground project. Underground work, because of its inherent characteristics, is among the most risky types of construction. The forecasting of underground conditions is at this time only educated predictions based on sometimes faulty data, insufficient data, or no data at all. The predicted conditions of numerous operations have deviated far from the actual conditions encountered. Opportunities for error exist in profusion seldom present for surface operations. Other than this unusual risk factor, the planning for underground work does not differ greatly from planning for surface work. In planning and starting an operation there is seldom available the information or time to thoroughly analyze all unknowns. It then becomes necessary to develop a plan predicated on assumptions and trade-offs that appear to be safe and economical and to add time and cost contingencies that will provide some degree of protection. On competitively bid fixed price work, choice of markup on estimated

Jan 1, 1974

By Changwoo Lee

Under drastically deteriorated situations, diesel equipment was introduced to some of local coal mines, aiming at higher productivity and better safety. To accommodate various diesel equipment in conventionally developed mines, mining system itself had to be modified; much larger trackless haulage ways were excavated. Possible health hazards of diesel not taken into account at the beginning become a serious concern and effective control measures are being searched for. The purpose of this paper is to study the diffusion characteristics of diesel exhaust in local coal mines. One of the parameters affecting dispersion of diesel contaminants is the coefficient of turbulent diffusion. Since CO2 is known to be closely correlated with other contaminants such as CO, NO, NQ, SO2 and RCD, it was chosen as a tracer gas in a series of dispersion experiments. A large diesel passage as well as a conventional track haulage way were the sites for the experiments. Rectangular dispersion pulses were generated for 30 ~60 seconds and CO2 concentrations were recorded at several locations 50~190 m downwind. The diffusion coefficients calculated graphically vary between 0.10~0.48 m2/s at both haulage ways. The results are analyzed to find any correlation with the air velocity and the distance from the disperser. Skobunov's empirical formula is applied to the experimental data for comparison and the relationship between Reynolds number and Ex/Dp/sci0.4 Sc1…

Jan 1, 1995

By Kenneth B. DeGraaf

The development of precious metal recovery processes using chloride systems has mostly evolved from the development of chloride based treatments for base metal concentrates or ores. The recovery of silver from chloride solutions within a process designed for the treatment of base metals usually is part of a solution purification stage. This paper discusses the development of the silver recovery stage used in the GCM HydroCopper process.

Jan 1, 1990

By Robert J. Storms, David J. Malone, Thomas E. Crandall

Corrosion and abrasion have been present in hydrometallurgical processes for many years. Ceramic lining materials have been used in several applications to protect process vessels from the corrosive and abrasive effects of a wide range of ore slurry processes. This paper reviews the history of ceramic lining systems utilized in hydrometallurgical vessels, the commercial benefits associated with their use, and additional areas of opportunity for the Mining Industry.

Jan 1, 1995

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 Takeshi Shinohara

It is a great honor and pleasure for me as President of the Japanese Tunnel Association to send greetings to the 1974 Rapid Excavation and Tunneling Conference. Recently in Japan, the Japanese Tunnel Association was established as recommended by the OECD Advisory Conference on Tunneling. This is a central organization concerned with tunnel construction consisting of government authorities, universities' research institutes and construction firms as well as manufacturers of relevant materials and equipment. As I was chosen the first president of the newly-established Japanese Tunnel Association, I would like to avail myself of this opportunity to announce to you its establishment and its earnest wish to contribute to the development of tunneling technique not only in our country but also all over the world. At the same time, I cordially request your friendship and cooperation for the benefit of further development of tunneling techniques on both sides of the Pacific. At present, many tunnels are under construction in Japan. The total length of tunnels under construction for railways and highways is about 600km including the 54km Seikan Undersea Tunnel which connects the Main Island and Hokkaido. Naturally, for construction of such tunnels in Japan, we have introduced much equipment and technique from the United States and other foreign countries. Now with accumulated experience, we are confident to be able to furnish various useful information concerning tunnel construction.

Jan 1, 1974

By Maurice Deul

Certain health and safety hazards occur entirely unexpectedly in some subterranean excavations. Although ground support is not the subject of this paper, ground failure can result in large and often uncontrolled flow of fluids into an excavation. Even when there is no ground failure, the disturbance of nature's equilibrium between rock or unconsolidated alluvium or rubble and the contained fluids poses severe problems to a well planned operation. Optimum conditions for safe operation cannot be the sole criterion for site selection. Some mineral deposits form in zones of structural weakness, others form where hydrothermal alteration substantially weakens the enclosing rock, and tabular deposits such as coal and evaporites inevitably undermine large areas. Excavation to acquire mineral values cannot be relocated. The same is often true for tunnels driven to connect distant points by the most direct route. Rivers and mountains cannot he avoided, and the cost of lengthening a tunnel--by even a fraction of a percent--must be strongly justified. No responsible engineer will knowingly select a dangerous route for excavation, but to what extent do engineers attempt to assess the health and safety hazards that may be reasonably expected? How, specifically, can methane explosions, water and sand flooding, dangerous dusts, toxic gases, thermal shock and radar poisoning be eliminated or minimized through systematic advance planning?

Jan 1, 1974

By David J. Herzog

There are two steps in evaluating potential mine waste impacts on ground and surface waters. Characterize the mine waste (characterization methodologies) and assess potential impacts (assessment strategies). One or both may be required for mine permitting, operation and closure. The first step is to characterize the waste. Determine if it has the potential to release chemical constituents or acid rock drainage to the environment. If no potential exists for release to the environment, the evaluation process is complete. A monitoring plan is then established. If the potential exists for release of chemical constituents or acid rock drainage to the environment, a strategy to evaluate potential impacts must be implemented. Strategies discussed here to evaluate potential impacts were developed during investigations at precious metal and base metal mines in Nevada. Water resources in Nevada consist mostly of ground water. So the strategies discussed focus on potential impacts to ground water. However, several of these strategies also apply to assessing potential impacts to surface water. Implementing these strategies has helped determine the potential for impact and has been successful in permitting mine expansion as well as allowing continued operation and obtaining mine closure at several mine sites in Nevada. These strategies were carried out in accordance with Nevada Division of Environmental Protection (NDEP) regulations and through the National Environmental Policy Act (NEPA)

Jan 1, 1995

By J. M. Carter, Rodney H. Sergent, L. E. Kun, J. T. Pressly

Underground mine service water in South Africa is used for dust suppression and cooling the environment as well as the pneumatic rock drills. Although the chilled water is not intended for potable use, it is often used as drinking water by mining personnel. Furthermore, droplets sprayed are liable to be inhaled. The water is recirculated on a continuous basis and is a potential source of infection by intestinal microorganisms or water-borne diseases such as cholera or typhoid. In order to protect the health of the underground workforce it is customary to disinfect the chilled service water, The bacteriological quality of the water is monitored by enumerating total aerobic bacteria (TAB), total coliforms (C C) and Escherichia coli (E Coli). E coli is an indicator of human faeca_l __ - -- contamination, The bacteriological standard specified by the Anglo American Corporation for mine service water is less than 3000 TA B per 100ml, less than 2 CC per ml and the total absence of E Coli. There are several disinfecting agents available for use. Among these are UV irradiation, ozone, chlorine dioxide and compounds that produce hypobromous and hypochlorous acids. Historically, the methods of treatment have been chlorine based and include the use of gaseous chlorine (surface installations only), calcium hypochlorite granules or tablets, chlorinated cyanurate tablets, sodium hypochlorite solutions and hypochlorite produced by electrolysis.

Jan 1, 1991

By David Martin Menne

In a small tank, slurry is passed through the high shear impeller zone with small time intervals, and a large proportion is regularly exposed to air at the surface, and at relatively high shear rates. This accounts for significant differences in the performance of large and small tanks. It is preferable to derive data where possible directly from an operating plant rather than applying data generated in small tanks where allowances must be estimated for the above differences [and where slurry aging and often substantial cooling compared to hot freshly milled ore further distorts results]. Various measurements have shown that many gold slurries can suffer extreme variability, as streamers of bypassing material or boules of hold-up periodically condstitute the instantaneous discharge from a tank - the relatively high Yield stress of slurries [around 1 to 10 Pa] causes very incomplete homogenization of slurry in any tank, the worse the larger the tank and the more viscous the slurry. To provide a background for this subject, this monograph presents leach and adsorption models based on the fundamental physics and chemistry of these processes, and includes quantitative discussions of factors which can lead to deviations on scale-up. The Throughflow model which avoids the need for such alowances is then presented, as well as a Computer Programme applying this model, and which allows direct calculation of the effects of:

Jan 1, 1995

By J. F. T. Agapito

Significant economic benefits can result when rock mechanics is applied within a practical framework and integrated within the other engineering functions of the mine organization. Such application and integration requires management support and understanding of rock mechanics as a practical tool to help attain high standards of safety, productivity and resource recovery. For such an approach, a long-term geotechnical program is needed in most operations to build an adequate data base and to ensure that design and ground control issues are handled in a cost-effective manner. Best usage of rock mechanics in mining occurs when management recognizes the application as a long-term investment, where time is needed to realize good returns. The need for this approach is due to the difficulty in accurately predicting ground conditions ahead of mining. The practical application of rock mechanics must follow an iterative process of design and verification based on site-specific experience to account for geologic and mining impacts. Ground conditions experienced during mining must be used to check the initial mine design and, if necessary, to provide a basis for design modification. Such a practical rock mechanics program includes comparative experience, in situ instrumentation and numerical modeling. The program begins with the geologic site investigation and continues throughout the life of the mine. It is an integral part of mine planning and operation.

Jan 1, 1991

By Levent Ozdemir

The advantages offered by mechanical mining have been demonstrated in the underground mining of coal, evaporites and other soft minerals. Mechanical mining and the advancements in automation technoloogies have been the principal drivers towards the realization of enhanced productivity in soft rock mining. For past two decades, emphasis has been placed on developing mechanical mining technology for hard rock applications, to achieve similar productivity improvements and cost reductions. The benefits of mechanical mining are numerous, particularly in an industry where market conditions continue to dictate higher production and lower costs while maintaining high safety standards. Other benefits of mechanical mining include reduced ground support and labor requirements and the elimination of blast and diesel fumes. These benefits further make this technology an attractive alternative to drill and blast for hard rock mining. Mechanical mining is conducive to full implementation of remote control and automation technologies that are under development to achieve further productivity and safety improvements in underground mining. Mine development has been the main focus area for mechanical miners by manufacturers and mining companies. Potential applications include ore body access, haulage and ventilation drifts, undercut and exploration drifts. The economic use of this technology in mine production is still considered many years away. It would need a major technological breakthrough that would make mechanical rock fragmentation competitive with the large-scale, low-cost production blasting operations.

Jan 1, 1998

By James C. Puckett

The mining industry finds itself in the middle, between the need to increase production of our energy resources and the necessity of minimizing the environmental impact. Using the recent past as a guide, the mine planning engineer's function will continue to increase as further coal quality constraints are made upon the production staff. The engineer will need to make use of all available tools in order to provide timely answers to the complex "what if" questions that arise. This need to consider many alternatives is bringing about a rapidly increasing acceptance and utilization of the computer. In the areas of data handling, mineralization modeling, and production simulation, the computer is an effective tool for the mine planning engineer. Described herein is a coal data storage and analysis system developed to provide timely answers to the "what if" questions for an operating strip coal mine in Montana. The characteristics of a computerized coal data base and coal quality planning system are outlined in this chapter. The system has been developed for use at a particular coal mine; however, it has applicability to coal mines in general. Fig. 1 is a flow chart showing the functional relationships of the system. There are three main file types: the drill-hole data base, the boundary file, and the zone file. The purposes for which each file is organized are illustrated on the flow chart.

Jan 1, 1979

By B. C. Haimson

The Committee on Rapid Excavation of the National Research Council has recognized in its 1968 report the need for "improvement of rock-mechanics techniques for measuring subsurface stress field in deep boreholes and for determining stress distribution in walls of underground excavations". The technique recommended in this paper as being most suitable for both deep hole and tunnel wall stress determination is Hydraulic Fracturing. Using this method stresses are calculated directly from the fluid pressures necessary to initiate and extend a fracture away from a borehole. Stress determination by hydraulic fracturing is rather insensitive to inhomogeneity or anisotropy, is not limited in depth except by the length of the hole, requires simple equipment which is commercially available, and can be carried out by unskilled personnel. The method has been worked out theoretically and extensively tested and verified in the laboratory. A number of field tests in deep holes ranging from 300 to 6300 ft have yielded surprisingly good results. Preliminary underground tests have been very encouraging and most recent measurements in a tunnel complex at the Nevada Test Site yielded stresses that were both consistent and reasonable when compared with the expected directionsand magnitudes. It is recommended that hydraulic fracturing be considered as a method of in-situ stress measurement both in the pre-excavation stage of design and during tunneling.

Jan 1, 1974

By M. Gershon

The article is an excellent one, providing a basis for the conduct of the major tasks in underground mine planning and scheduling. I object to only one word. Since that word is featured in the title, it is a strong objection. The word used erroneously is optimization. There is no optimization performed in the article. By definition, an optimization is an approach that yields the best of all possible solutions. We can limit this definition to its narrowest sense, the optimization techniques of operations research such as linear programming, or broaden it to include less sophisticated search procedures that find the best mine plan or schedule. No such claim is made in the article. No optimization of any kind is performed. The major tool used is a simulation, which, in truth, is probably more appropriate for this problem than any optimization. But simulation does not optimize. It only allows for quick evaluation of many options, leading to the selection of the best plan "of those tried," not "of all possible plans." This article, of course, is not the first mining paper to make this error. It seems that the word optimization is used more to impress people than to refer to any act of optimizing. It is used in a way that implies "try to optimize" or "come close to optimize," but not to really do it. It is usually appropriate to quietly ignore this error. But when Dr. Chatterjee, who has done so much good work in true optimization projects and whose work I have come to admire, makes such an error, it is time to publicly dispute it. Having discussed this very point with him in the past, I am sure that he will agree. If he can support this position in his response, perhaps people will start to listen and we can reduce the number of false claims of optimization. This should be easy for him in this case since the approach he used, simulation, is the more appropriate one anyway.

Jan 1, 1987

By Roland F. Beers

At East Union, Knox County, Maine, near the shore of Crawford Pond, an outcrop of basic rock has been known for more than a century. The occurrence has been regarded as an unusual type of peridotite-pyroxenite, containing disseminated and massive pyrrhotite with nickel, copper and cobalt in recoverable amounts. From the outcrop, the sulfide body had been mapped more or less continuously for a distance of two miles through geophysical methods of several kinds. This paper describes the methods in sufficient detail to evaluate their significance. A core drilling program has con- firmed the location of the conductor and offers a positive means of correlating the geophysical measurements with the physical properties of the ore body. The history of the exploration offers a unique opportunity to evaluate the method of multiple geophysical methods.

Jan 1, 1962