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By Robert W. Leonardson

The Questa Molybdenite Mine provides a unique opportunity to study the geochemical dispersion of various hydrothermal events, utilizing drill hole analyses. Numerous post-ore factors have altered the primary ore-related geochemical dispersions to the present day configuration, e. g. dikes, faults, hydrothermal convection cells, and weathering. Due to the interaction of an andesitic volcanic pile with the silicic-alkalic generated volatiles, the geochemical haloes of the Goat Hill deposit demonstrate a marked divergence from the classic Climax-type molybdenite ore body. Certainly, however, the similarities to the Climax-type ore body are apparent as potassically-rich fluids have invaded the highly reactive country rock.

Jan 1, 1984

By D. P. Bryan

An aggregate resource study was done for southern Washoe County, Nevada, which contains the Reno-Sparks metropolitan area and a population of about 300,000. The study included an inventory of existing operations, projection of future demand, identification of potential aggregate resources based on geology, and determination of economic potential of these resources. Economic potential was determined by the integration of GIS layers that included aggregate potential, distance from market, distance from major and minor transportation arteries, and elevation. The investigation resulted in a determination that resources of high quality aggregate sufficient for future consumption are present in southern Washoe county; the limiting factor for future utilization is accessibility.

Jan 1, 1996

By M. K. Rizkalla

This paper discusses the time-dependent behaviour of rock when it involves the presence of several layers of rock strata in the vicinity of mine openings, mining in sequences and the placement of backfill. The paper describes numerical techniques which proved useful when such situations are encountered in practice. The model is elastoviscoplastic. At given time stations, short term loading or changes can be made to the creep behavior of the rock. The modelling technique is first described and is followed by simulations of stresses and displacements in a potash mine with the primary objective to demonstrate the effect of such aspects as mining and fill sequences in 3-D. This involves cutting finite elements representing the strip of the mining face and simultaneously filling those elements representing the newly placed fill. The stiffness of the fill varies with the degree of compaction at each point. In this way, the effect of the time of fill placement, the gap between the top of the fill and the back as well as the degree of compaction are simulated. The second example is a 2-D problem simulating the long term effect of backfill, as a material compacting with time, on the settlement of the layers above it as well as the closure of the room.

Jan 1, 1996

By J. Alatalo

Autogenous grinding is a process of reducing the particle size distribution of an extracted ore by using the ore itself as the grinding media. It is a process that is difficult to control and there is a lack of knowledge of the events occurring inside the mill. To find out more about how the mill behaves under different processing conditions, a full factorial test was performed with iron ore in a pilot-scale pebble mill at the LKAB R&D facility in Malmberget. To complement this work, a strain gauge detector was embedded in one of the mill?s rubber lifters, the Metso Minerals continuous charge measurement (CCM) system, and was used to get more information about the charge dynamics. The data from the experiments has been analyzed. For production purposes, an increase in the number of particles smaller than 45 µm can be regarded as a probable increase in the production rate. The analysis shows that there will be an increase in fines at 65% of critical speed, especially when the mill is 45% full. This setting will also increase the power consumption, but improves the grindability of the ore even more. The deflection of the lifters is smaller for lower critical speeds. A higher degree of filling also gives a smaller toe angle and a higher shoulder angle as expected.

Jan 1, 2011

By J. Alatalo

Autogenous grinding is a process of reducing the particle size distribution of an extracted ore by using the ore itself as the grinding media. It is a process that is difficult to control and there is a lack of knowledge of the events occurring inside the mill. To find out more about how the mill behaves under different processing conditions, a full factorial test was performed with iron ore in a pilot-scale pebble mill at the LKAB R&D facility in Malmberget. To complement this work, a strain gauge detector was embedded in one of the mill?s rubber lifters, the Metso Minerals continuous charge measurement (CCM) system, and was used to get more information about the charge dynamics. The data from the experiments has been analyzed. For production purposes, an increase in the number of particles smaller than 45 µm can be regarded as a probable increase in the production rate. The analysis shows that there will be an increase in fines at 65% of critical speed, especially when the mill is 45% full. This setting will also increase the power consumption, but improves the grindability of the ore even more. The deflection of the lifters is smaller for lower critical speeds. A higher degree of filling also gives a smaller toe angle and a higher shoulder angle as expected.

Nov 1, 2011

By R. R. Johnson

The Hama Mining Company owns and operates The Groveland Mine near Iron Mountain, in the Upper Peninsula of Michigan. The orebody is part of the Menominee Range of the Lake Superior District. The ore (generally known as Jasper taconite) contains an average of 35% iron ranging from 28% to 39% with an overall split of 60% magnetite and 40% hematite. The variations encountered throughout the orebody require a certain amount of blending to reduce feed changes to the mill. One of the variables which affects the crushers, as well as the mill, is the range of hardness which has a low of 7.9 and a high of 24.6 as measured by the Bond Twin pendulum impact and crushing technique. Reference is made to hardness only to point out its effect on crushing and wear rate variations. Over a period of time, these variables do, of course, average out. Mining of the low grade ore started in 1959 and has operated continuously to date. Preparation of the feed for conventional rod and ball mill grinding is accomplished by three stages of crushing. Reduction of crude ore is first passed through a 54 inch gyratory crusher; then through a secondary crusher; followed by two or three tertiary crushers in closed circuit with screens as production quotas require (Figure 1). Current demand to the crushers is about 5,200,000 tons of crude ore per year.

Jan 1, 1976

By J. Noll, D. Yantek, J. Organiscak

The Office of Mine Safety and Health Research of the U.S. National Institute for Occupational Safety and Health (NIOSH OMSHR) conducted laboratory testing of a self-tramming, remotely controlled mobile Dry Scrubber (DS) that J.H. Fletcher and Co. developed under a contract with NIOSH OMSHR to reduce the exposure of miners to airborne dust. The scrubber was found to average greater than 95 percent dust removal efficiency with disposable filters, and 88 and 90 percent, respectively, with optional washable filters in their prewash and post-wash test conditions. Although the washable filters can be reused, washing them generated personal and downstream respirable dust concentrations of 1.2 and 8.3 mg/m3, respectively, for a 10-min washing period. The scrubber’s velocity-pressure-regulated variablefrequency- drive fan maintained relatively consistent airflow near the targeted 1.42 and 4.25 m3/s (3,000 and 9,000 ft3/min) airflow rates during most of the laboratory dust testing until reaching its maximum 60-Hz fan motor frequency or horsepower rating at 2,610 Pa (10.5 in. w.g.) of filter differential pressure and 3.97 m3/s (8,420 ft3/min) of scrubber airflow quantity. Laboratory sound level measurements of the scrubber showed that the outlet side of the scrubber was noisier, and the loaded filters increased sound levels compared with clean filters at the same airflow quantities. With loaded filters, the scrubber reached a 90 dB(A) sound level at 2.83 m3/s (6,000 ft3/min) of scrubber airflow, indicating that miners should not be overexposed in relation to MSHA’s permissible exposure level — under Title 30 Code of Federal Regulations Part 62.101— of 90 dB(A) at or below this airflow quantity. The scrubber’s washable filters were not used during field-testing because of their lower respirable dust removal efficiency and the airborne dust generated by filter washing. Field-testing the scrubber with disposable filters at two underground coal mine sections showed that it could clean a portion of the section return air and provide dust reduction of about 50 percent at the face area downstream of the continuous-miner operation.

Jan 1, 2016

By A. E. Michon

I am Alfred E. Michon, Vice President- International for Burlington Northern Inc. I work for BN's holding company and my responsibilities include co-ordinating the activities of our eight subsidiary companies as they relate to international commerce--an increasingly important aspect of the overall business of our company. Until last April, I was President of the Fort Worth and Denver and Colorado and Southern railroads, subsidiaries of BN. Prior to that, I headed the marketing and pricing area of BN's coal transportation business. Based on my experience in the energy industry, both domestic and international, I would like to discuss the world-wide trend towards the reliance on low-sulfur coal in lieu of natural gas and oil for the generation of electricity. Since pontification on the energy scene world- wide is best left to consultants with scenario-spitting computers, let me in- stead emphasize this trend through two examples. First I will describe the regulatory and economic factors which have encouraged the replacement of natural gas by low sulfur coal as a boiler fuel in the US. BN's investments in track and equipment were instrumental in this conversion. Secondly, I will show how this same combination of factors has created a large demand for steam coal in the Far East. Again, our company's strategy is to facilitate conversion to coal overseas through timely and sufficient investments.

Jan 1, 1982

By E. A. Lauha

The Goldstrike Mine is in Eureka County, Nevada, U.S.A., approximately 23 miles northwest of the town of Carlin. The mine is at the north end of the Tuscarora Spur of the Tuscarora Mountains at elevations of 5,300 feet to 5,950 feet. It is part of the Bluestar/Goldstrike sub-district of the Carlin Trend, a northwest alignment of sediment hosted, disseminated gold deposits. The Carlin Trend includes over 15 major gold deposits with production, reserves and geological resources of approximately 65 million ounces of gold (Figure 1). In the Bluestar/Goldstrike sub-district, there are seven major deposits: Betze, Lower Post, Post, Genesis, Bluestar, Purple Vein and Deep Star, plus numerous smaller deposits (Figure 2). Production, reserves and resources for the sub-district are approximately 40 million ounces. Betze and Purple Vein are located on property controlled by Barrick Goldstrike Mines and Bluestar and Genesis on Newmont Gold property. Post, Lower Post and Deep Star occur both on Barrick and Newmont property.

Jan 1, 1993

By William H. Lane

After a number of years of engineering and operating assignments and through many types of evaluations, the need for a simple analytical method of evaluating mine haulage alternatives became obvious. Haulage, like 50 many other facets of mining, is generally a sequence of interconnected events that change, often drastically from mine to mine. Often the operator or the mine engineer has neither the time, manpower, facilities, or information needed to prepare a detailed evaluation. For many studies or for routine variance analysis, that detail may not be necessary. The intent of this article is to present an approach for analyzing mobile mine haulage that is simple and straight-forward. These methods are not designed to replace more formal and detailed procedures that have been developed previously and are available in our technical libraries. They are offered as a tool to be applied to preliminary designs, feasibility studies, and variance analyses where more complete detail is not warranted. These methods will eliminate combinations that are not economical or appropriate before more intensive and complete evaluations are undertaken. These methods may also be used to evaluate ongoing operations and to plan changes in those operations. This presentation describes a series of steps that have evolved for the handling of haulage evaluations. It concentrates on the factors having major impact on the results. Because the approach is a sequence of distinct steps, a case study was chosen as the best method of presentation. This case is a composite of several actual situations that have been encountered within the last few years.

Jan 1, 1978

By Kenneth S. Johnson

Large reserves of high-purity Permian gypsum crop out and are at shallow depth in three regions of western Oklahoma, Gypsum beds in the Blaine Formation are 10 to 30 feet thick and are generally 95 to 99 percent pure, whereas the massive Cloud Chief Gypsum is 20 to 100 feet thick and is 92 to 97 percent pure. Reserves are estimated at 48 billion short tons. Eight companies in the State currently mine about 1 million tons of gypsum each year for wall- board, for plaster, as a retarder in portland cement, and as a soil conditioner. Future uses, under more favorable market conditions, may be in the chemical industries, largely because of gypsum's potential as a source of sulfur. Three thick sequences of Permian rock salt underlie most of western Oklahoma at depths of 30 to 3,000 feet. Individual salt beds 5 to 30 feet thick are interbedded with thinner layers of shale and anhydrite. Five large salt plains, fed by natural springs of saturated brine constitute additional resources of salt. Reserves, estimated at 20 trillion short tons, are virtually untapped, and, ironically, about 90 percent of the salt used in Oklahoma is imported. Chemical data on the rock salt are lacking, but evaporated salt produced from brines is generally 97 to 99 percent pure. Current production from three solar-evaporation plants is used mainly for stockfeed, recharging water softeners, and deicing roads. Potential uses are in the chemical industries, where salt or brine is a necessary raw material.

Jan 1, 1973

The criteria used to design, operate and control flotation columns are significantly different from those used for conventional flotation machines. Therefore, a computer-aided design (CAD) package for column flotation has been developed. The simulator has been set up using guidelines developed at Virginia Tech and information published in literature during the past few years. The simulator is useful for determining the proper design and appropriate operating conditions for a column cell to fit a specific set of conditions. In addition, the simulator can be used for training in column operation and for trouble-shooting operational problems. Simulation results have been found to be in good agreement with experimental data obtained using laboratory columns.

Jan 1, 1990

By Rafael Moure

On April 21, 1980 the Oil, Chemical and Atomic Workers Union (OCAW) submitted a petition urging the revision of the Mine Safety and Health Administration (MSHA) permissible exposure limit to radon daughters in underground mines. This petition asks for: 1. Annual worker exposure to be lowered from the current 4 WLM/year to 0.7 WLM/year; 2. Full economic protection for workers whose exposure exceeds the proposed 0.7 WLM/ year; and 3. The primary means of lowering workers' radiation exposures shall be environmental controls. I will present the scientific rationale for the lower standard requested in our petition to the Department of Labor. [1. Radiation Exposures to Uranium Miners] Two types of radiation exposures are present in the environment of uranium mines: A. [External Exposure] to gamma sources which until 1978 was considered as negligible compared with internal alpha radiation. R. E. Utting (1), in an investigation of three Canadian uranium mines, found levels of exposures adding to an annual dose equivalent of 3 rems (30 mSv)/year. He concluded that gamma dosages may be a major fraction of the maximum permissible dose for many individual miners. The U.S. experience has shown that there is significant gamma exposure in U.S. uranium mines and, therefore, it could contribute to the total radiation exposure to the lungs in combination with internal alpha radiation. Before ventilation improvements in uranium mines, the contribution of external radiation to total lung dosage was relatively small. After improvements in ventilation, the reduction in internal radiation exposure appears to be in 1980 as low as 1/10 of the 1950 dosages. However, ventilation improvements do not affect external gamma radiation. Gamma radiation remains at the same 1950's level, and it represents today a higher proportion of the total radiation burden to the miner's lungs. MSHA regulations (57.5-47) state that if gamma exposure is below 2.0 milliroentgens per hour, then workers are not required to wear gamma dosimeters and cummulative gamma radiation records need not be kept. Assuming an exposure of 1.9 milliroentgens per hour per 173 hours/month for 12 months,a miner would accumulate a dose from external radiation of 3.9 rems/ year. This dosage would, of course, go unrecorded. MSHA, therefore, should consider a downward revision of the external radiation permissible exposure limit of 2.0 milliroentgens/hour. MSHA should make clear that this exposure level, when added to the internal exposure, does not make for sound health physics -even though the measured current levels do not approach 2.0 milliroentgens/hour. B. [Internal Exposure] to alpha radiation is still the larger contributor to lung irradiation in uranium miners. The target organ is still the lung. The parameters to be considered in determining the biological radiation load appear in Table I for radon daughters present in the upper respiratory tract (URT). TABLE I RADIATION DOSE PARAMETERS IN THE URT OF URANIUM MINERS Parameter Uranium Underground Mining [1. Quantity of the Absorbed Radon daughters (Po-218, Nuclide Pb-214, Bi-214) deposit in bronchial and lung tissue. (Measured by air concentration, Working Levels) 2. Type of Radiation Emitted Alpha Particles 3. Energy of Radiation High-Linear Energy Transfer 4. Half-life of the Nuclide Ra 222, 3.8 days in the Organ Po-218 (RaA), T1/2 = 3.1 minutes Pb-214 (RaB), T1/2 = 26.8 minutes Bi-264 (RaC), Vi = 19.7 minutes 5. Selection Factor of the Direct inhalation with mine Organ dust to be deposited in the tipper Respiratory Tract 6. Mass and Form of the Organ Especially cancer sensitive, tracheobronchial region and bronchi* 7. Distribution of the Activity Dependent on deposited dust in the Organ distribution in the Upper Respiratory Tract 8. Chemical Nature of All compounds (RaA, RaB, RaC) Incorporated Substance biologically insoluble. (Only localized, irradiation) *See Reference (2)] The parameters of Table I depend, in turn, on the demography of the exposed population, especially: 1. Age 2. Sex 3. Health Status 4. Genetic Constitution 5. Lifestyle (Smoking, Diet) Some of these demographic characteristics of uran-

Jan 1, 1981

By ERIK CHARRIER, HUGH MILLER, JOSEF BOURGEOIS

In this study, a unique excavation system was characterized, utilizing waterjet technology as the primary tool for material removal during rehabilitation of reinforced concrete and shotcrete structural liners. Through empiric testing, this research seeks to validate the hypothesis that waterjet removal of these support systems will result in less unintended damage than conventional removal methods. The intent is to develop a viable technology that will reduce the collateral damage caused to surrounding liners during excavation, improve the adhesion between shotcrete and the substrate for longer lasting ground support, and improve overall safety for workers in underground environments. An analysis on the fracture mechanisms and operating parameters of each method was completed. Instrumented shotcrete panels were physically tested and examined through visual inspection and ground penetrating radar (GPR) to compare substrate damage according to each testing method. After testing was completed, the data strongly indicates that waterjet cutting causes less collateral damage to the surrounding intact liner and substrate when compared to that of conventional impact hammers. This research is intended to provide a scientific basis for additional applied research in the rapid excavation and repair of shotcrete support systems.

Sep 23, 2021

By Jessica M. Wempen, Dallan J. Coons, Bailey S. Simmons, Michael K. McCarter

Gate-road yield pillars are subject to increases in stress as the longwall face advances toward the pillars. Increases in pillar stress can be inferred by measuring roof/floor convergence surrounding the pillar. This paper presents a case study of convergence measurements surrounding a two-entry gate-road yield pillar in the head gate of a coal mine. Convergence was measured over a six-month period, as the longwall face approached and passed the pillar. Measurements were collected at eight locations surrounding the pillar: four locations in the travelway and four locations in the beltway. In addition to convergence stations, the pillar was instrumented with an array of seismometers. In future analysis, convergence measurements will be compared to seismic interpretations. This study reports on the geology and geometry of the longwall panel, the roof and rib support, the change in convergence over time, and the physical properties of coal and parting. Additionally, the convergence measurements are compared to pillar safety factor distributions derived from a finite element model. The convergence measurements contribute to the knowledge of when yield pillar abutment loading, caused by the encroaching longwall, is first detected. Knowing when abutment loading begins to yield the pillars can help define when standing secondary roof supports are required for head gate entry support.

By Ning Wang, Tengfei Guo, Wanyan Li, Hanjie Wen, Hannian Gu, Zehai Li

Bauxite residue (red mud) is an alkaline waste derived from the industrial process for extraction of alumina from bauxite ore. Some bauxite residues contain considerable concentrations of critical metals, for example, rare earth elements. Lithium in red mud was also reported as a potential resource. In the current study, a Li-rich red mud was leached using acetic acid to investigate the leaching behavior of lithium followed by neutralizing with hydrochloric or oxalic acid. By neutralizing red mud using diluted hydrochloric acid (0.01 mol/L), 58.04–60.27% of lithium was leached using 25% acetic acid at 95 °C for 60 min. In the meantime, more than 95% of sodium and 85% of calcium were also dissolved in the leachate solution. While oxalic acid (0.5 mol/L) was used to neutralize red mud prior to acetic acid leaching, lithium performed lower leaching efficiencies (42.41–46.88%) in comparison of using of hydrochloric acid–neutralized red mud. Nevertheless, these leaching efficiencies of lithium were close to that of calcium and much higher than those of sodium under the condition. In this study, 25% (v/v) of acetic acid, at 85 °C for 60 min, was demonstrated as optimum conditions for lithium extraction from oxalic acid–neutralized red mud using acetic acid. The results would be useful and of interest for lithium recovery and purification from red mud.

By M. Kehnemuyi

The U.S. Department of Energy is charged, by federal law, with the responsibility for developing and implementing programs for long- term storage and terminal disposal of high- level radioactive wastes from both commercial and defense nuclear operations. Approximately 288,000 cubic meters of defense high-level wastes are currently in storage at the government's Hanford Reservation in the State of Washington, the Savannah River Plant in South Carolina, and the Idaho Chemical Processing Plant in Idaho (U.S. Department of Energy, 1980a). High-level wastes from commercial nuclear power production are stored in water pools or basins at various power plant sites. At the end of 1980, approximately 7.460 metric tons of uranium, contained within 28,300 fuel assemblies was in storage at various reactor basins. Although the present inventory of defense wastes are many times larger in volume and in total level of radioactivity than the commercial wastes, in the future, the latter will constitute a substantial quantity of wastes that will have to be disposed of. The present electric generating capactiy of nuclear power plants in the United States is 56.5 Gigawatts-electric (GWe). The amount of spent fuel that would be discharged and accumulated by the year 2000 from these operating reactors would be 38,000 metric tons. With a projected growth of the nuclear industry to 180 GWe in the year 2000, the amount of spent fuel accumulated at the turn of the century could reach 89,000 metric tons of uranium or approximately 318,000 assemblies. In any case, whether one postulates a no growth pattern or one where nuclear power provides its share in the country's electric generating capacity in the next two decades, a means for safe and environmentally accept- able disposal of high-level nuclear wastes must be found. Storage of commercial wastes in water basins, either at reactor (AR) sites or at away from reactor (AFR) sites, and storage of reprocessed defense wastes in surface or near surface tanks is a temporary solution and is not an alternative for permanent disposal.

Jan 1, 1981

By Verya Nasri, Mehdi Bakhshi

"Fiber reinforcement has emerged as an alternative to steel bars in precast concrete segments due to advantages such as saving cost and reducing production time while developing a more robust product with improved handling and long-term durability. ACI recently drafted a new report as the first design guideline on FRC tunnel segments to provide specific guidance for this emerging technology. ACI document offers general information on the history of FRC precast segments from tunneling projects throughout the world; a procedure for structural analysis and design based on governing load cases, and a description of the material parameters, tests and analyses required to complete the design. This paper summarizes the design considerations in this ACI guideline prepared by the authors of this paper as the main contributors. Application of this guideline to design of a tunnel with an internal diameter of 5.5 m (18 ft) results in elimination of steel bars.INTRODUCTIONPrecast concrete segments are installed to support the tunnel excavation behind the Tunnel Boring Machine (TBM) in soft ground and weak rock applications. The TBM advances by thrusting off the completed rings of precast concrete segments that provide both the initial and final ground support as part of a one-pass lining system. These segments are typically designed to resist the permanent loads from the ground and groundwater as well as the temporary loads from production, transportation and construction. Tunnel segments are generally reinforced to resist the tensile stresses at both the Serviceability (SLS) and the Ultimate Limit States (ULS). With traditional rebar, a significant amount of labor is needed to assemble the cages and place the rebar, which results in higher production costs.Fiber Reinforced Concrete (FRC) can be used to enhance the production, handling, and placement of precast concrete segments. This is because of the uniform dispersion of fibers throughout the segment to include the concrete cover, which is very advantageous for resisting the bursting and spalling stresses. These stresses develop as a result of the high loads induced on the segments during the TBM jacking process. The presence of fiber in the concrete matrix helps mitigate against unintentional impact loads during segment handling and tunnel construction operations."

Jan 1, 2016

By M. J. Laurila

The concentration of low grade iron ores to pellets or sinter fines suitable for blast furnace feed or direct reduction is highly energy intensive and costly in terns of both size reduction and separatory processes. Large equipment with high throughputs are required to make the fine grinds and multi-stage separations economical. Control of these circuits is essential to producing a high grade product. As a result, iron ore concentrators possess some of the more sophisticated instrumentation for process control in the mineral dressing industry. These instruments must characterize flowstreams of up to 8,000 gpm where 80% of the particles are less than 50 µm. The past decade has been one where enormous strides have been made in automated control of iron ore plants. This paper reviews state-of- the-art control systems for crushing, grinding, magnetic separation, froth flotation and sizing/classifying circuits. Trends toward computerization and plant automation in response to a dismal outlook for North American steel production are also examined.

Jan 1, 1984

By F. Habashi

Chile is at present the largest copper and rhenium producer and was before World War I the largest nitrate producer. She is also an important producer of lithium carbonate and molybdenum oxide. An important event in the history of the country is the Pacific War of 1879-1883 in which she acquired the northern provinces initially belonged to Bolivia and Peru. In 1888 Chile annexed Easter Island. The Chilean mineral and cultural history is briefly reviewed together with the people who contributed to her development. The present report is the result of a number of academic and industrial visits to Chile during the period 1992 to 2009.

Jan 1, 2011