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By Tomb. T. F., R. A. Haney

During the past several years, the Mine Safety and Health Administration (MSHA) has conducted studies in underground mining operations to obtain information on occupational exposures to diesel particulate (DP), mine environmental DP levels and on the effectiveness of methodologies used to control DP. The studies conducted were representative of four coal mines and 10 metal mines. The metal mines included two lead-zinc mines, one limestone mine, two potash mines, one zinc mine and four salt mines. Three of the four coal mines were using disposable diesel exhaust filters to remove particulate from the exhaust and one was using a reusable wire mesh filter. Results of these studies indicate that average DP levels in coal mines not using exhaust filters range from 0.9 to 2.1 mg/m3, The use of exhaust filtration devices reduced these levels by about 50% to 90%. Studies conducted in metal and nonmetal mines showed average DP levels ranging from 0.3 to 1.6 mg/m3.

Jan 1, 1996

By M. Saidman, R. Pizzuti, R. Hirschfeld, A. J. Desai, J. Rand

Two bedrock tunnels, 170 to 250 feet deep and with a length of about 17,000 feet each, will be used to convey cooling water from the Atlantic Ocean to the Seabrook, N.H., Nuclear Power Plant. Seismic reflection and refraction surveys were used to obtain preliminary information about overburden and bedrock conditions. A major boring program, including core orientation and water-pressure testing, was undertaken to provide detailed geologic data. The results of the geotechnical investigation were summarized in terms of rock type, frequency and character of joints, degree of weathering, modified core recovery (RQD), pressure-test results and strength and hardness. These parameters were used as a basis for evaluating the feasibility of using a tunnel-boring machine, for designing and estimating the initial support systems, and for evaluating the grouting and tunnel lining requirements.

Jan 1, 1976

By E. D. Thompson, Y. J. Zhang, K. F. Unrug

This paper presents the results of a recent study on the development of an in situ testing method for determining coal strength in mine pillars. The strength testing is performed in the horizontal holes drilled into the coal rib using a penetrometer, which is an hydraulically powered device that uses an indenter to press on the surface of the borehole until the load reaches the failure point of the coal. The pressure and the penetration of the loading pin are recorded by a data-acquisition unit. The results collected from several coal mines indicate that this testing method is ideally suited for the realistic coal strength measurements. The new testing system not only improves the accuracy of the pillar-strength determination, but it is more cost efficient than the conventional method.

Jan 1, 1997

By A. Unal, R. L. Grayson

The use of radio frequency identification (RFID) technology to solve informational needs in isolated and restricted underground mining environments are reviewed, and the specifications of some of the past and currently available systems are presented. The advantages and disadvantages of using various frequencies, system configurations and specific components, including their construction standards and capability, are also discussed. The remaining challenges to the more widespread use of RFID systems for personnel and vehicle tracking are identified, and recommendations concerning the operating environment capabilities are detailed. Finally, the ultimate requirements for maintaining system integrity during and following a coal mine emergency are discussed.

Jan 1, 1999

By D. E. Ranta, Leigh A. Readdy

Defining classes of ore using geostatistical methods that match historical classifications has presented problems in the past. A simplistic and practical approach to this problem is presented. An example of the approach is presented using a porphyry-type system as a case study. The technique described uses area of drill-hole influence and known conditions from similar deposits, or the production history of the deposit being studied. It provides a practical bridging mechanism for defining the class of ore on a block-by-block basis using the error of estimation value developed during kriging. The approach provides a filtering method that refocuses attention on the adequacy of drill-hole spacing.

Jan 1, 1992

By F. L. Wilke

Bong Mining Co. Ltd. in Liberia, West Africa, operates an iron ore open pit some 60 miles northeast of Monrovia. The production is at present about 40,000 t/d (metric tons/day) from which about 18,500 t/d concentrate with 65.5% Fe is produced. The ore waste ratio is about 1: 1.5 to 1:2. The technical layout and the equipment are very similar to those in many modern open-pit operations as described by Jacobs and Thomson (1967). As described by Lersch in detail (1966), the deposit is a very irregular one. The quality of the ore changes within very short distances with regard to both physical conditions (hardness) and chemical properties. Very soft and very hard ore as well as high-grade and low-grade ore are found adjacent to each other. In addition, there are enclosures of sterile rocks. For the purpose of identification and production scheduling, 12 different types of ore are distinguished.

Jan 1, 1979

By Don C. White

Santa Rosa is a mid-Tertiary, volcanic-hosted, gold-silver deposit. Current proven and probable reserves are 8.9 Mt (9.8 million st) grading 1.5 g/t (0.044 oz/ st) gold, minable by open pit and amenable to heap leaching. It is the product of hydrothermal mineralization along an arcuate segment of a caldera collapse ring fault in a probable maar volcanic setting. This segment was later broken by radial faults. Gold at Santa Rosa occurs principally as electrum, finely disseminated through intermediate tuffs, and associated with pyrite. The nearby Alto de la Mina deposit displays stockwork silica-pyrite-gold in a tectonically and hydrothermally shattered andesite flow. Miocene epithermal mineralization was accompanied by central silicification and pyritization and more distal argillization. An andesite flow cap rock at Santa Rosa played a pivotal role as an upward permeability barrier. Highest gold grades and most intense alteration occur closest to the ring faults and immediately beneath the andesite flow. Supergene alteration effects on the gold distribution are minimal.

Jan 1, 1995

By Ralph D. Daley, Kevin E. Redinger

The production of coal/water fuel (CWF), a highly loaded mixture of finely ground coal, water, and chemical additives, presents a unique opportunity for significant ash and sulfur reduction through physical coal cleaning. Froth flotation can be integrated with the staged, wet, fine grinding inherent in the CWF production process. A laboratory scale research program was conducted to demonstrate the feasibility of a flexible, integrated coal cleaning/CWF process flowsheet. Performance of the conceptual flowsheet was examined for two coals of CWF commercial interest, Upper Freeport and Pittsburgh seam coals, from central and southwestern Pennsylvania, respectively. Several multi-stage coal flotation and reverse flotation circuits were evaluated. CWF was produced from the cleaned coal in each case at similar solids loadings and viscosities as observed for the raw coal. However, the ash loading and SO2 emission potential for each CWF had been significantly reduced.

Jan 1, 1988

By Y. M. Jiang, D. W. Park

Longwall faces can move at high advancing rates, but many geological variations can cause unexpected instabilities and production losses. The rapid movement makes it necessary to evaluate different geologic conditions in the rock mass as fast as possible to assess their effects on the longwall face and shields. It is believed that prompt awareness of geologic conditions is the key to preventing instability at a longwall face. This paper introduces the application of fuzzy set theory for characterizing and evaluating roof conditions. Real-time monitored data coupled with fuzzy set analysis provides valuable information, such as shield leg pressure, developing load on shields, intervals of periodic weighting and the ratio of developing loads during periodic to normal times.

Jan 1, 1998

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 Xia Guangxiang, R. Y. Wan, Yang Hanlin, M. C. Fuerstenau

The mechanism and kinetics of pretreatment on pyritic gold concentrate with the catalytic oxidation acid leach (COAL) process were studied in the temperature range of 80-100°C and oxygen pressure range of 230-1013 kPa, with sodium lignosulfonate (SL) and mixed medium of sulfuric acid (11 g/[ ]) and nitric acid (5.5 g/ [ ]). The results show that nitric acid acts as a catalyst, the surfactant changes the hydro-phobicity of resulting elemental sulfur to favor the oxidation of pyrite, and the oxidation-determining step would be the chemical reaction between nitric acid and pyrite. When about 80% of pyrite contained in the concentrate is oxidized, the gold cyanidation extraction exceeds 95 % . The nitric acid in solution can be recycled and used again.

Jan 1, 1993

By M. Jaramillo

The expanded west pit of the 15 Mta (13.6 stpy) El Cerrejon mine will eventually reach a maximum depth of 270 m (890 ft). Slope-stability evaluations indicated that this depth, combined with structural complexities, would create a serious risk of footwall instability. Stabilization calls for anchoring the footwall by the installation of 9- to 33-m- (30- to 108 ft-) long multistrand steel cable bolts. For each of the 15-m- (50-ft-) high mining benches, a row of bolts is installed with variable horizontal spacing, depending on the dip magnitude. Cable bolting is now standard operating practice, and an estimated 11,800 bolts will be installed during the life of the mine. Results to date have been satisfactory in terms of the stability condition of the bolted slopes.

Jan 1, 1997

By M. G. Papasotiriou

For our company, S&B Industrial Minerals S.A., restoration of areas which were mined and the effort for bringing up again a balance of nature is an important priority over the last 3 decades. The successful qualitative results of restoration works have delivered to nature over 1.700.000 m2 of surface after mining activity. Our fundamental method in order to achieve the best results for restoration of mined areas is the use of local plants (bush or tree type). Grass and herbs are installed by using the method of hydroseeding. Small trees and bushes are produced and they grow up at our fully owned Milos nursery and they are installed during winter when weather conditions are suitable. During the initial stages of restoration activities a great amount of surfaces, adequately shaped, are delivered by the mining department covered with top soil. These surfaces are suitable not only for the local nature community but also for a combination between natural and agricultural environment. The above fact was a great chance to create small horizontal agricultural cultivations as pilots inside the restored areas. At the beginning the agricultural items that could potentially be installed in these pilot areas were studied and examined analytically. The following agricultural items were finally qualified to be furthermore researched: 1) Vineyard (Vitis vinifera ) 2) Prickly pear (Opuntia ficus indica) 3) Jojoba (Simmonsia chinensis) 4) Olive tree (Olea europea)

Jan 1, 2007

By M. Dondi, M. Surracco, G. Alfano, P. Saba

Recent investigations on fine grinding with jet mill miprototypes of original design, constructed at the DIMM and Centro Studi of the National Research Council at Cagliari University, have led to the realization of a third generation micronizer characterized by large capacity and high efficiency. The new model and its distinctive features are described here and the results are presented of grinding tests on typical, high grade Sardinian minerals used for quality products. The operating principles of the jet mill are described in relation to the mechanico-elastic properties of the minerals treated. In particular the efficacy of the comminution process is demonstrated in terms of both solid treated and of impact, attrition and shearing forces generated in the micronizer. Particle size distribution of the finished products are reported, that satisfy the most stringent market specifications for the different minerals, as well as energy consumptions. The alternative operating options for solving particular grinding problems and minimizing energy consumption are discussed. Lastly, the main developments of the jet mill for a possible application at industrial scale are suggested.

Jan 1, 1995

By A. Unal

Coal resource characterization usually calls for estimating more than one variable over a block or node simultaneously. Within the realm of geostatistics, each variable has been evaluated independently from the others assuming a lack of significant correlation. Research conducted with coal seams, however, has shown that the variables of immediate interest, such as seam thickness, ash, sulfur content, and density depict some correlation schemes in distinct zones, if not throughout the entire area. The above findings have two immediate consequences : (1) correlation analyses provide guidelines to determine the geologically distinct zones, and (2) where possible, cokriging should be used instead of kriging. This will maximize data utilization decreasing the frequently criticized high estimation errors. The cokriging formulation will also provide more accurate estimates for under sampled variables using better-sampled ones. This is a common case with coal with regard to the non-cored reconnaissance drill holes for which only very few variables were recorded. A case study illustrates the improvements that may be obtained by taking advantage of the intervariable correlations.

Jan 1, 1986

By Normand Tassé

Reactive barriers, which consume oxygen, are prospective though unconventional alternatives to physical barriers for Acid Mine Drainage prevention. However, a reactive barrier implies a problem of duration. Pore gases were analysed in several wood waste piles in order to understand the factors which control wood degradation and help to determine the effective life span of such a cover. Long term efficiency seems to strongly depend on the degree of water saturation at the bottom of the pile, likely because the development of a microbial biomass in such an environment helps to keep the amounts of nutriments and readily metabolizable organic substrates at a high level, which in turn promotes oxygen consumption.

Jan 1, 2000

By S. S. Peng, V. Z. Sun

One of the major concerns of ground control in a coal mine is the prevention of roof, pillar and floor failures of the mine entry. To better design and evaluate the stability of a mine entry within a certain level of confidence, a reliability approach is introduced. The advantage of using the reliability approach, rather than the conventional safety-factor (SF) method, is that it not only takes variability of both rock/coal properties and stress into consideration but also assesses the stability of each component and the mine entry as a whole. Therefore, it is anticipated that by using this approach the current ground-control technology in a coal mine will convey a better sense of confidence. The results of a case study show that there is a significant difference in mine entry stability between the current design method and the reliability approach.

Jan 1, 1999

By Thomas E. McNider

Preliminary studies were conducted at Jim Walter Resources, Inc. Blue Creek No. 3 Mine to determine the influence propane operated heaters exert on the mine ventilation system when two of three intake airshafts were heated. During initial use of the heaters, it was found that change in density caused by heating a portion of the air at two of three intake shafts altered under- ground air flow changes sufficient to be considered a violation of Part 75.322 of the Federal Coal Mine Health and Safety Act of 1969 as amended by Public Law 95.164. The primary concern was to accurately define the problem in order to derive a workable solution.

Jan 1, 1980

By Lars Olaf Höglund

MiMi has been set up to be i) visionary, ii) strategic and iii) long-term. The planning as well as the executive phases involves industry, academia and authorities in close co-operation. MiMi focuses on improved, economically efficient management of mining waste, a challenge that requires combined and integrated research efforts across discipline boundaries. The MiMi programme is financed by the Swedish Foundation for Strategic Environmental Research (MISTRA) with support from the mining industry. The first programme phase covers the period 1997 - 2000, with intentions for additional phases. Planning, experience and results from the first programme period are highlighted. INTRODUCTION Most of the mining activities in Sweden takes place in the No

Jan 1, 2000

By Kewal K. Kohli, Richard E. Thill, Syd S. Peng

The results of unpublished investigations into surface subsidence from coal mining in the Northern Appalachian Coalfield are summarized. These investigations were carried out by various coal companies and the State of Pennsylvania in the sixties and seventies. Subsidence data were collected and analyzed from 10 room-and-pillar panels in 5 mines in the Pittsburgh coal seam. Results show that angle of draw ranges from 26° to 33° and subsidence factor from 0.42 to 0.72; surface heating generally occurs beyond the edges of the panel, the amount and extent of which vary; waviness occurs in the subsidence profile if a substantial number of pillar stumps are left in irregular patterns; interpanel effect is significant; time-dependent subsidence exists, but varies for different panels; and surface slope does not seem to affect the amount of subsidence.

Jan 1, 1982