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By Denis Tepavac, Mark Trim

Structural performance of fiber reinforced concrete (FRC) depends on its ability to carry tensile forces after cracking. Australian Standards AS5100-2017 and AS3600-2018 are the only available design standards that establish a test procedure to determine strength and toughness of an FRC in direct tension. Direct tensile testing of fiber reinforced shotcrete samples was performed to determine if the model and guidelines in AS5100/3600 were applicable to shotcrete; all previous testing was from cast samples. In addition to direct testing, micro CT-scanning was also performed. The paper presents tests performed, results, and how the tests could be used on future projects. In addition, a brief summary is provided of the guiding structural mechanics used for estimating residual tensile strength and test methods utilized to verify those estimates.

Jun 13, 2023

By A. J. Plumpton

Centrifugal air classification and li-quid-phase sedimentation are the principal methods of industrially sizing materials of dimensions smaller than those handled by screens. Increasing application of materials such as composites and high performance ceramics has furthered the need for closely-sized, fine, industrial mineral and synthetic products of controlled properties. Sedimentation can be used to separate very small sized particles but introduces problems of liquid-solid separation, de-agglomeration and drying. Some of the advantages and limitations of centrifugal air classification will be discussed and laboratory and plant measurements using centrifugal machines will be presented to support the discussion.

Jan 1, 1990

By V. Aghazadeh, E. Bidari, M. Aazami

In this study, mineralogical and microanalysis characterization, as well as diagnostic leaching and cyanidation tests, were performed to gain a better understanding of the refractory nature of the arsenical zone of a Carlin-type gold deposit and also to evaluate possible treatment routes to maximize gold recovery. The results obtained showed that only 56% of the ore’s gold content is amenable to direct cyanidation. The majority of the remaining gold was found as submicroscopic gold and in association with sulfide minerals, such as orpiment, pyrite, and sphalerite. It was also found that despite the abundance of silicate and carbonate minerals in the arsenical zone, they do not play a key role in the refractory nature of the ore, and gold can be liberated from such minerals by appropriate grinding. The analyses further revealed that orpiment dissolves readily during cyanidation, and this dissolution retards the kinetics of gold extraction. Pyrite and sphalerite were generally found to occur in fine network texture and in association with quartz. Flotation of such auriferous sulfides may be difficult due to their oxidized surface. Fine grinding (−20 μm) was found to be partially effective in improving gold extraction.

May 28, 2020

By J. R. Hoskins

Method - A direct approach to instrument users, initially by letter and later by telephone or personal contact was made. The resultant data was compiled to give specific use information on the seven instruments. During the course of the study attempts to evaluate the Griswold Gage were abandoned when it became apparent that the gage was not being commercially produced. One company is developing the gage for its own use. The information presented is the result of over 1200 inquiries.

Jan 1, 1973

By J. L. Carr

On average, one to two fatalities occur every year when a miner is struck or pinned by a continuous mining machine (CMM). Proximity detection systems offer an effective means to prevent these types of injuries and fatalities by sensing the presence of a miner and automatically disabling machine motion. The Mine Safety and Health Administration (MSHA) is expected to finalize a regulation that would require the use of proximity detection systems on all CMMs. Approximately one-fourth of all CMMs in use in the United States are already equipped with such a system. The use of these systems will save lives, not only by automatically preventing accidents but also by acting as a tool for educating miners and reinforcing safe work practices. Researchers at the Office of Mine Safety and Health Research (OMSHR) have conducted a series of field evaluations to quantify the performance of these systems in an underground coal environment. These field evaluations measured the distance at which the warning and stop zones were activated. The technology provided consistent activation of the warning and stop zones under many of the conditions tested. However, some performance inconsistencies were observed which present opportunities to improve the reliability of proximity detection system technology. Some of the notable variables that caused significant changes in performance and should be considered in the design, implementation, and use of proximity detection systems include interaction with the trailing cable, performance changes during tramming, and orientation of the miner-worn component.

Feb 23, 2014

By Hamid Mazouz, Mohammed Hakkar, Rim Jouraiphy, Fatima Ezzahra Arhouni, Ahmed Mahrou, Aziz Boukhair, Mohammed Fahad

The wet process is the most commonly used worldwide for phosphoric acid (PA) production, in which phosphate rock (PR) is reacted with strong acid mainly sulfuric acid. This work aims on studying the rare earth elements (REEs) distribution during the production of phosphoric acid using different qualities of phosphate through various industrial technologies. At the onset of this work, the process started with 12 samples of PR, PA, and phosphogypsum (PG) being taken simultaneously from two different Moroccan basins (Ouled Abdoun mine represented by K09 and Gantour mine depicted by G10, G20, BG) and various production lines at two processing platforms (Jorf Lasfar and Safi). Afterward, collected samples were prepared and analyzed for REE characterization using an inductively coupled plasma mass spectrometry (ICP-MS). Based on the analysis results, a transfer factor ( TFX) was introduced with the aim of gauging the REE distribution between PA and PG. The results showed that the total concentration of REEs in different phosphate qualities ranged from 411 to 631 ppm; the major part of this concentration was attributed to the four elements: Y, La, Ce, and Nd which constitute more than 77%. The REE distribution between PA and PG depends on neither the phosphate quality nor the industrial technology used since that the distribution results showed that 55 up to 66% of the initial REEs in phosphate rock ended up in the PG. The behavior of each REE was common except for the element scandium, which transferred mainly to the phosphoric acid.

Nov 3, 2021

By Brett P. Spigarelli

To meet the growing need for CO2 capture and storage technology, Michigan Technological University is researching CO2 capture and storage using alkali solutions1. Without implementing emission controls, world energy emissions will rise from 29.7 billion t in 2007 to 42.4 billion t in 2035. The first objective of the project was to determine the optimal amount of alkali in solution for CO2 absorption. This was accomplished using theoretical equilibrium calculations and experimental absorption data for alkali solutions of 1, 2, 3, 4 and 5 weight %. As the % alkali in solution increased, so, too, did the ionic strength of the solution. Theoretical calculations took into account the effect increasing ionic strength will have on the solubility of gaseous CO2. The calculations assumed negligible formation of H2CO3, constant temperature and constant pressure. In the experimental setup, a 16% CO2 /balance air gas mixture was bubbled through an Erlenmeyer flask filled with an alkali solution. The gas exiting the flask was fed to a gas analyzer to record the % CO2 in the exhaust gas stream. The % CO2 absorbed was taken as the % CO2 in the exhaust gas minus the % CO2 in the feed. Theoretical calculations found that as the % alkali in solution increases, the solubility of CO2 decreases. This was verified by experimental data, which found that a 2% alkali solution, by weight, was the ideal solution for CO2 absorption. Current research is focused on using the 2% alkali solution for permanent storage of CO2 via mineral carbonation to produce a value-added product.

May 1, 2012

By Muhammad Hashim Rasa, Ali Aras

Recovering valuable metals from tailings not only provides a source of income but also helps conserve natural resources, thus reducing the environmental impact of mining activities. This study aimed to recover cobalt using tailings of the Küre flotation plant, which were determined to contain 0.17% Co. Flotation tests were conducted on samples taken from the tailings to investigate the effects of pH and pH conditioning time, as well as types and amounts of depressant, collector, and frother on the grade and recovery of Co in rougher flotation tests. Optimal flotation conditions were determined to be pH 6, a pH conditioning time of 7 min, and dosages of 50 g/t, 100 g/t, and 20 g/t of sodium hexametaphosphate, X-231, and DF250, respectively. According to the rougher flotation test results, a concentrate with a Co grade of 0.46% and a Co recovery of 84.15% was obtained. In the concentrate obtained using cleaner flotation tests, the Co grade increased to 0.49% and Co recovery increased to 90.56%. These results show that froth flotation, carried out with the appropriate reagents, is a successful method for recovering Co by enriching the flotation plant tailings.

May 17, 2023

The dissolution kinetics of cobalt in iodine/iodide solutions was investigated using a rotating disc technique. Variables studied here included temperature, rotating speed, concentration of lixiviants, and pH of the solution. The overall dissolution reaction was found to be limited by mass transfer of tri-iodide through the diffusion boundary layer with Arrhenius activation energy of less than 16.2 kJ/mol (4 kcal/mol) over the temperature range, 2-42°C. The pH of the solution had little effect as long as the pH of the solution was less than 8. However, when the pH of the solution became greater than 8, the dissolution rate decreased dramatically due to passivation. The rate of dissolution was in good agreement with the dissolution model developed by the authors earlier.

Jan 1, 1994

By I. Mazalov, G. Ospanova

Introduction Today, uranium is of great interest because of its application to nuclear power and nuclear weapons. Kazakhstan has been an important source of uranium for more than fifty years. All uranium products are exported. Results In Kazakhstan uranium exploration started in 1948 and developed in several parts of the country thru mining of hard rock deposits. There are known around 50 uranium deposits in six provinces: Shu-Sarysuyskaya (57%), North Kazakhstan (18%), Syrdaryinskaya (15%), Ilyiskaya (7%), Caspian (2%), Balkhash (1%). In the Northern Kazakhstan province, KazSabton took over Tselinny Mining & Chemical Co in 1999. In this province the stockwork is of Paleozoic and Paleozoic folded complexes origin. In the Balkash province some mining of volcanogenic deposits occurred during the Soviet era. This province’s stockwork is of Endogenous origin.In the Ili province uraniumis mainly found in uranium-coal deposits formed by oxidation of the lignite beds roofs. In the Caspian province the Prikaspisky Combine operated since the 1960s a major mining and processing complex on the Mangyshalk Peninsula. This led to the founding of Aktau. It was privatised as Kaskor in 1992 and operations ceased in 1994. The uranium occurrence is associated with the phosphorous from fossil fish bone detritus conglomeration. In the Chu-Sarysu province, which has more than half the country's known resources, both Stepnoye and Tsentralnoye have been operating since 1978 and 1982 respectively. Uranium mineralization occurred in the regional stratum oxidation zones. In the Syrdarya province slightly to the west of the province’s center the No.6 Mining group has been operating since 1985. Uranium mineralization occurred in the regional stratum oxidation zones.

Jan 1, 2007

By Jon Ike Isaacson, Michael Miller, Jarek Trela

Despite reef structures being relatively common in carbonate rocks around the world, tunneling experience in reefs is extremely rare. Impacts and risks associated with reef tunneling through these geologic features were also relatively unknown. A new reef was encountered during construction of the Lower Pogues Run Tunnel in Indianapolis, exposed over 5,000 linear feet along the alignment, resulting in adverse impacts on construction. Analysis of investigation data and construction from this encounter provide insight into the identification and characterization of reefs along tunnel alignments as well as the potential impacts on construction for future tunneling within reef structures.

Jun 23, 2024

By S. S. Hsieh

As part of a program to address long-term needs for ensuring adequate supplies of domestic phosphate raw materials, the Tennessee Valley Authority (TVA) has conducted considerable research on dolomitic phosphate rock beneficiation. The discovery that alkyl diphosphonic acids act as phosphate mineral depressants led to the development of several processes involving a carbonate flotation step for the effective beneficiation of these problem ores. Most recently, a partial de-oiling process in which the reagent consumption is greatly reduced has been developed. The reduction is achieved because part of the initial feed is beneficiated without passing through the separate carbonate flotation step. Using this method, a phosphate product containing 30.6-30.9% P2O5 and 0.7-0.8% MgO was obtained from a Florida dolomitic phosphate pebble which contained about 23% P2O5 and 2.0% MgO. The P2O5 recovery was 80.8-86.5%.

Jan 1, 1989

By Robert Hochscheid

When the original water-only cyclone patents were established in the 1950?s, the supplies of low cost oil and natural gas were abundant and low selling prices for metallurgical and steam coal provided little incentive for developing more sophisticated coal cleaning systems. Bituminous coal sold for less than $5.00 per ton, and in this period many domestic coal producers discarded to the slurry pond the coal finer than 0.5-mm. For many producers, the selling price would not permit the recovery of the capital and operating costs required for dewatering and drying the fine coal. Water-only Cyclones Clean Fine Metallurgical Coal The first broad interest in the water-only cyclone became evident in the mid- 19601s, and though some work was done on coarser coals, investigators were particularly interested in cleaning coal finer than 0.5-mm. Flotation was the only fine coal cleaning method that was broadly accepted, but short-comings were recognized and investigators were looking for an effective fine coal cleaning device or system. Because of the greater market value and the need for reducing pyritic sulfur in metallurgical coals, much of the development work of the 1960's was done on coking coals.

Jan 1, 1981

By Karl C. Dean

To assist in the reduction of environmental degradation resulting from milling operations, the Bureau of Mines has developed, and successfully demonstrated, chemical, vegetative, and combined chemical-vegetative procedures for stabilizing milling wastes under varying environmental conditions. Costs of achieving reclamation using these stabilization procedures are compared with those of other physical and vegetative approaches. The Bureau's chemical-vegetative procedure for establishing vegetation directly on fine-sized wastes compares favorably with other stabilization processes that have been used.

Jan 1, 1972

By K. T. Stafford, N. A. Iverson, V. T. McLemore

Southwestern New Mexico is part of a large belt of Late Cretaceous to Eocene copper porphyry deposits found in Arizona, New Mexico, and Mexico. These deposits are the result of arc magmatism that occurred during the Laramide orogeny. Recently, attention has been brought to other commodities that can be extracted as by- and co-products, many of which are critical minerals. A new compilation of the geochronology of these deposits shows two main pulses of magmatism that produced mineralized deposits and, along with new dates by the author, shines new light on the geologic history of these deposits and the role it plays in critical mineral abundance.

Feb 1, 2024

By Joe M. Short

More than eighty years ago, in what we generally consider a more leisurely age, workers and engineers began the construction of the longest railroad tunnel in the world. When completed, the Simplon Tunnel ran more than twelve miles through the alps to connect Switzerland and Italy. Work began in 1898 and the tunnel was completed in 1905. In all it took about seven years to build one of the world's great tunnels. More than seven years ago, in what was hoped to be a rapid and constructive to the deaths of 38 workers in two spectacular tunnel disasters in 1971, the secretary of Labor's Construction Advisory Committee on Safety and Health began in January 1972 a search for an effective standard on tunnel safety. Much hard and useful work has been done, especially by the construction advisory committee' but more than seven years later, we still don't have a tunnel standard. We may speculate that, when the Simplon Tunnel was completed, workers and their bosses assembled to celebrate their achievement and to count their casualities. We have no need to speculate on the lack of achievement up to this time. An so far as I know, the bureaucrats have suffered no casualities except perhaps some unreported cases of ring-around-the-color. The only moral I can draw from all this is thai it is easier to penetrate solid rock than it is to get through bureaucratic fog. We can only hope that OSHA will finally take advantage of the work which was finished years ago and complete the actions necessary to give us a tunnel standard. Having made my point, I could stop my remarks right now; but

Jan 1, 1979

By Jacob Carr, Bruce Whisner, Adam Smith, Jingcheng Li

Electromagnetic-based proximity detection systems (PDSs) are utilized on mining machinery to protect workers from being pinned or struck. These systems generate magnetic fields covering the space around a machine, and a miner-wearable component (MWC) detects the field. The PDS determines the distance of miners relative to the machine based on the detected magnetic flux density in the magnetic field. This information is used to establish warning and shutdown zones around the machine. Maintaining a stable magnetic field is essential for system accuracy. However, components used to generate magnetic fields can be influenced by temperature changes. Depending on ventilation conditions and seasonal alternation, a PDS can be subject to significant temperature fluctuation. To better understand and quantify this phenomenon, researchers from the National Institute for Occupational Safety and Health (NIOSH) developed an experimental apparatus to study the influence of temperature on magnetic field generator circuits used in PDSs. Results from the study show that the electric current through a generator can be influenced by both ambient and internal temperatures, modifying the magnetic field that is produced. These findings show that temperature can significantly influence the ability of PDSs, used in underground coal mines, to accurately determine a worker’s position in relation to mining machine.

By N. M. Levine

This work defines and systematizes the physical factors of the problem of leaching and demonstrates for the first time the utility of macropore volume, micropore volume, specific surface, pore size distribution and permeability as parameters of leaching based on a study of the recovery of uranium from the Top Black member of Chattanooga Shale.

Jan 1, 1962

By Patrick R. Taylor

United States Antimony Corporation, at its Yankee Fork property in central Idaho, is currently using a combination of flotation, gravity-amalgamation, and concentrate cyanide leaching, silver sulfide precipitation, and activated charcoal loading to recover both silver and gold. Tine processes of flotation, milling, gravity concentration, amalgamation, concentrate leaching, sulfide precipitation and gold recovery via charcoal are discussed. The flow sheet illustrates the use of cyanidation as an alternative to shipment to a smelter.

Jan 1, 1984

P.T. Freeport Indonesia's latest expansion has increased total mill throughput to 125,000 dry metric tonnes per day. The most recent expansion included the installation of a Semi Autogenous Mill designed to treat more ore than any other single SAG mill currently operating in the world. Also included in the expansion were two large ball mills, rougher and cleaner flotation including conventional and column cells and a regrind circuit. All equipment is supported by a modem distributed control system. This paper describes the design considerations, construction, commissioning and start-up of the SAG concentrator and support facilities and includes an overview of the oreflow and milling facilities.

Jan 1, 1996