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By Steve Kral

The mining industry in Colorado faces the same problems the industry faces throughout the United States and the world — record low commodity prices and increasing regulatory and environmental restrictions that seemed designed to curtail mining activities. Despite those obstacles, the mining industry in Colorado still contributes about $8 billion annually to the state’s economy in the form of base and precious metals, industrial minerals, coal and associated service businesses and jobs. So the 300 attendees at the102nd National Western Mining Conference felt reason-ably positive about the industry in their state. The meeting is the Colorado Mining Association’s annual conference and was held at the Broadmoor Hotel in Colorado Springs in November. The theme was “Mining in the New Millennium — Achievement + Innovation = Survival.” Experts from Colorado’s mining industry and abroad discussed the challenges faced by the mining industry as it enters the new millennium. They offered insights into how the industry will operate during the early years of the 21st century and how it will survive low prices and increased regulatory restrictions.

Jan 1, 2000

By Richard Wilson

In the early 1970s, it became a concern that exposure to the mineral fibers associated taconite ore processed in Silver Bay, Minnesota would cause asbestos-related disease including gastrointestinal cancer. At that time data gaps existed which have now been significantly reduced by further research. To further our understanding of the types of airborne fibers in Silver Bay we undertook a geological survey of their source the Peter Mitchell Pit, and found that there are no primary asbestos minerals at a detectable level. However we identified two non-asbestos types of fibrous minerals in very limited geological locales. Air sampling useful for risk assessment was done to determine the type, concentrations and size distribution of the population of airborne fibers around Silver Bay. Approximately 80% of the airborne fibers have elemental compositions consistent with cummingtonite-grunerite and the remaining 20% have elemental compositions in the tremolite-actinolite series. The mean airborne concentration of both fiber types is less than 0.00014 fibers per milliliter that is within the background level reported by the World Health Organization. We calculate the risk of asbestos-related mesothelioma and lung cancer using a variety of different pessimistic assumptions. (i) that all the non-asbestos fibers are as potent as asbestos fibers used in the EPA-IRIS listing for asbestos; with a calculated risk of asbestos-related cancer for environmental exposure at Silver Bay of 1 excess cancer in 28,500 lifetimes (or 35 excess cancers per 1,000,000 lifetimes) and secondly that taconite associated fibers are as potent as chrysotile the least potent form of asbestos. The calculated risk is less than 0.77 excess cancer case in 1,000,000 lifetimes. Finally, we briefly review the epidemiology studies of grunerite asbestos (amosite) focusing on the exposure conditions associated with increased risk of human mesothelioma. © 2008 Elsevier Inc. All rights reserved. Keywords: Risk; Fibers; Particles; Taconite; Asbestos; Exposures

Jan 1, 2007

By Moyle F. J

This paper describes an apparatus which was developed to study solid-vapour equilibria and presents results which were obtained during a study of the FeCI3-AlCI3-CI2 system. Analysis of the results showsthat fractional desublimation might offer a means of achieving a useful separation of the iron and aluminium chlorides produced by the chlorination of bauxite. The results, presented in the form of isothermal vapour pressure curves covering the range of temperature 160-200°C, support the earlier findings of Semenenko et al (Dokl Akad Nauk SSSR, 154: 42-43 (1964)) that the solid phase contains two terminal solid solutions.The equilibrium constant for the formation of the mixed dimer, FeAICI6, was approximately 4. The latent heat of sublimation of aluminium chloride varied from 18 to 26 kcal/mole AI2CI6 for solid compositionsfrom 0.9 to 0·5 mole fraction FeCls3.

Jan 1, 1979

By N Clarke, G R. Ballantyne, M S. Powell, P Elms, A Anyimadu

AngloGold Ashanti Ltd nominated Sunrise Dam Gold Mine as a case study via their involvement with the long-running Australian Mineral Industry Research Association (AMIRA) International P9P research program (AMIRA, 2015) . A group of researchers from the Global Comminution Collaborative (GCC) conducted a comminution circuit survey and review together with a large group of graduate metallurgists, senior metallurgists and operators. Fundamental and applied research understanding was used to identify productivity and efficiency improvements around the crushing and grinding circuits. The limitations of current scientific knowledge were identified through this process and this will allow future research to be more focussed on what is required by industry.The comminution circuit at Sunrise Dam comprises three stages of crushing followed by two stages of ball milling. The secondary crusher and primary ball mill classification were identified as the primary limitations of the circuit. The secondary crusher was found to be underperforming through overall equipment efficiency (OEE) analysis and an improved chamber design was identified by Chalmers University. This improved design will promote higher power utilisation, choke feeding and a finer crushed product for the milling circuit. The primary ball mill product is classified by a combination of a trommel, 3 sieve bends and a hydrocyclone. The combination of poor classification and coarse, competent feed led to a situation where the primary mill was overfilled with rocks, reducing grinding rate due to cushioning of impact. Size specific energy (SSE) benchmarking methodology was used to identify that a 10% increase in throughput could be achieved with improved primary classification.CITATION:Ballantyne, G R, Clarke, N, Elms, P, Anyimadu, A and Powell, M S, 2015. Application of research principles to identify process improvement at Sunrise Dam Gold Mine, in Proceedings MetPlant 2015, pp 221–229 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 7, 2015

By Emad Iskander

The seepage forces generated around pressurized water tunnels in rock are investigated using the analysis tools of geomechanics. The theoretical background of the two-phase material behavior is explained and the equations of motion and continuity are presented. Applications on two case studies typically occurring in practice deal with the required minimum rock cover for a pressurized tunnel and the separation between two tunnels carrying different heads. The rock mass behavior as described by the Mohr-Coulomb and Hoek-Brown material models is investigated by numerical analyses and the results are compared. The effect of key material parameters on the safety factors and the associated modes of failure is discussed.

Jan 1, 2008

THE object of the air-tight stopping is either to prevent a current of fresh air from getting into the fire area, or to prevent an escape of fumes and gases from the fire area into the workings of the mine. In the former case all is "plain sailing," but in the latter case there are certain difficulties to be overcome.In the Broken Hill Proprietary mine there were two styles of stopping used during the last fire-brick and bag and the following were the chief points that determined the use of one in preference to the other:-If the required stopping were to be more or less permanent, bricks were used, also if the area to be blocked were large-bricks being so much lighter and easier to handle than bags filled with -skimps. If, however, the air contained much gas, a bag stopping was put up. Great difficulty was experienced in getting essentially surface men, such as bricklayers, to work where there was the; slightest trace of gas; miners, however, would willingly do the work, and a bag stopping could be built without skilled labour.In old drives and gangways, where there was the liability of settlement, the bag stoppings were preferable to brick. The slightest movement around the sides or foundations of the latter would cause cracks, thus rendering the brick stopping useless;whereas, in the former, there was a certain amount of elasticity.

Jan 1, 1909

By K. Saikiran, A. R. Nalla

Longwall management, regular shield maintenance, and evaluation of ground control problems can be performed using real-time shield monitoring program. Based on real-time shield pressure data, evaluation of intensity and interval of periodic weighting, estimation of time-dependent pressure increase and the effects of geologic anomalies can be obtained. In this study, full-face shield pressure data of over 457 m (1,500 feet) of face advancement is analyzed to evaluate shield response in the presence of surface lineaments, floor undulations, and multiple main roofs. Shield pressure increase due to web cutting is also correlated with setting pressure during periodic weighting and normal time. In addition, time-dependent pressure increase rate on Sundays and holidays is also correlated with time average pressure and the location of previous periodic weighting.

Jan 1, 2000

By Peter D. Bell

The paper describes the geology of the gold deposits of the Yanacocha district, Northern Perú. The Yanacocha District is located 20 km north of the city of Cajamarca, whose deposits are located in the Andes of norther in Perú. Gold production may have occurred as early as Incan times, but modern exploration that began in the 1960’s targeted only copper and silver. Current mining is entirely by open pit methods with heap leach recovery. Production in 2003 was from the Cerro Yanacocha deposit and the La Quinua fluvioglacial deposit. La Quinua is not discussed in detail in this report. However, Yanacocha is described as a high-sulfidation epithermal deposit occurring in pyroclastic rocks. The success of Yanacocha has made this type of target among the most sought after by exploration companies worldwide. The important characteristics of the geology of Yanacocha are reviewed below, along with some specifics of exploration techniques used in the district.

Sep 12, 2005

By Donald F. Reed

In the Coastal Plain sedimentaries of northeastern Mississippi, high-alumina clays and kaolins, which are bauxitized locally to varying degrees, are found in many places along the contact between the Midway (Paleocene) and the Wilcox (Eocene) series. The trace of the contact extends from Tippah County, on the Tennessee border, south to Winston County, thence southeast to Lauderdale County, and into Alabama. Its length within Mississippi, disregarding sinuosities, is 185 miles (fig. 1). Commercial production of bauxite from the region has amounted to about 400 tons, shipped from one outcrop in Komper County. In December 1941 and January 1942, the Bureau of Mines and the Federal Geological Survey made a reconnaissance survey of the contact zone and selected the most promising areas for further study. In 1942, four areas in Benton, Union, and Pontotoc Counties were investigated by auger and rotary core drilling, and in 194, core drilling was done on five areas in Kemper, Noxubee, and Winston Counties. The present report records the work done by the. Bureau of Mines and the factual data obtained from the investigations of the nine areas in the two projects.

Jan 1, 1952

By Bengt L. Stillborg

INTRODUCTION This paper summarizes the result of a two and a half year research program. The objective of the research was to develop a fundamental understanding of the Rib-in-Roc method. Through the development of a new model technology, namely three-dimensional physical models which powerfully exploit the results of dimensional analysis Stillborg, Stephansson and Swan (1), it has been possible to establish the contribution to both permanent and immediate stabilization of a large underground opening pre-reinforced by the Rib-in-Roc method. Using the results from these physical models and earlier work by Stillborg and Stephansson (2) and Åkesson (3), a conceptual synthesis is given in this paper so demonstrating the Rib-in-Roc method to be a practical working system of pre-reinforcement. DESCRIPTION OF THE RIB-IN-ROC METHOD To give the reader an idea of how this method of pre-reinforcement is performed, a short description will be given, Figure 1. Before any full-scale excavation takes place an entry is made in the host rock and rib raises are driven around the proposed opening. These raises are made at a spacing that is dependent upon rock quality; an opening in poor rock needs more ribs per length of opening. As the ribs are driven they are used as a site from which very competent rock bolting can be done. As a rib is excavated it is filled with reinforced concrete. Finally after having in this way reinforced the zone around the proposed opening, (a reinforced arch is formed) the displacements are automatically controlled as the opening is being excavated. Using this method openings with a span of 50-60 meters (160-200 ft) and a height of 60-80 meters (200-260 ft) are likely to be realised.

Jan 1, 1979

By Jorge Meza

Uno de los objetivos principales del proyecto de la modernización de la Fundición SPCC es capturar y procesar el gas generado de la reacción exotérmica del proceso de fusión de los sulfuros del concentrado para transformarlo en un subproducto comercial que es el (ácido sulfúrico) H2SO4. En ese sentido, el presente texto señala el manejo de un sistema de control de gases a través de un proceso sofisticado para el enfriamiento, limpieza y manejo de este gas de dióxido de azufre, reduciendo los costos de operación, así como el tiempo de reacción de los equipos involucrados en el manejo y procesamiento de los gases.

Sep 19, 2006

By D. Strachan

Installation of support in known poor ground intersections during reaming operations requires rapid access to stabilize the shaft wall and thus to prevent the loss of the shaft through scaling. This is especially relevant to shafts of long dimension where the duration from time of exposure to time of support installation is lengthy This paper deals with the innovative methodology employed at Harmony?s No. 8 Shaft 17/24 level sub ventilation shaft to rapidly support a shale intersection between 23 and 24 Level by employing a single deck stage suspended from the reamer head by means of Skyjack winches.

Jan 1, 2009

By L. J. Lorig

Much of the present knowledge about caving behavior of rock masses has been obtained from empirical observations. Additional notions about caving have been developed through inferences derived from two-dimensional finite element analyses. These analyses have indicated that a combination of one low-angle set of fractures and one nearly vertical set of fractures is the optimum fracturing configuration for ease of cavability of an orebody. This paper presents the results of two- and three-dimensional distinct element analyses which draw different conclusions than those reported from finite element studies. The distinct element method is selected far analysis of cavability because this method treats the rock mass as an assemblage of rock blocks which may interact individually, The results of the analyses are compared to a documented case history which involved a groundfall of 80,000 tons of ore in a 160-foot high pillar. The mechanics associated with these results are-explained in terms of simple static stability analysis of wedges. The propensity for orebody caving is primarily a function of the number of joint sets or potential "release" surfaces in the orebody. This mechanism is influenced by the bounding weak discontinuities, and intact strength of rock material.

Jan 1, 1989

By Rainer Kahrger

This paper is a follow-up to the paper presented at the SME meeting in April of 1996. Since then, the El Abra facility has been started up, 9 months ahead of schedule, and has processed about 45 million tons of ore and produced over 700 million pounds of copper. For those unfamiliar with the El Abra materials handling and leaching facilities, a brief overview of the facility is provided. The paper will then deal in detail with such aspects of Conveyor 103, the long regenerative overland conveyor, including: actual running resistance starting and stopping procedures emergency brake test at 10,000 t/h Additionally, we shall take the opportunity to report on a catastrophic culvert collapse in October 1996, which stopped the conveyor abruptly at full speed and under high load condition, causing a belt breakage. We would like to use this opportunity to thank the management of El Abra and Cyprus Amax for providing assistance and allowing us to present this paper. The El Abra team deserves a great compliment for building this one billion dollar facility in record time in a remote area of a high-altitude desert with no existing infrastructure, and for bringing it so quickly up to full operating capacity. The El Abra management had to assemble a completely new operator team. Considering the above circumstances, it took a great effort by all involved to achieve success. The official performance test which was required by the lending banks was successfully concluded in November 1997.

Jan 1, 1998

By Gordon R. Sima

The contract is concerned with feasibility studies, design and fabrication of a group of prototype hand-held test instruments and machine-mounted test instruments for measurement of electrical shock hazards of mining machines. An instrument for use in open pit mining machine ground wire verification was proposed, developed, built, and tested. This report presents the design and operational theory of the open pit instrument as well as information on the program to improve the original prototype hand-held machine-mounted test instruments.

Jan 1, 1977

By Patrick J. Doig

The contract for the construction of the Inline Pump Station for the Milwaukee Metropolitan Sewerage District involves the sinking of three shafts and the excavation of a pump chamber. The shafts are being sunk to a depth of 104 meters and pass through 52m of sediments before encountering dolomitic bedrock. The pump chamber is constructed in dolomite. The sediments are alluvial, estuarine and lacustrine in origin, with some ice margin deposits. They comprise loosely consolidated fine to coarse grained sand, silts, clays and gravels, and they are heavily saturated with a water content often above 60%. The water table is at a depth of 3m. The dolomite is silurian, generally dense, with some clay-filled vugs and shale partings. Until 1983, underground construction in the Milwaukee area had been limited to depths of 26m in the sediments and 20m in the dolomites. Water control methods had included caissons, compressed air, extensive internal and external dewatering, and grouting. Flows of 20 liters per second were commonplace with as much as 80 liters per second being encountered in the rock. However, in 1984 work was commenced on the deep sections of the Milwaukee sewerage scheme with the letting of three major contracts including the Inline Pump Station. With excavation taking place at greater depths, it become obvious that previous methods of water control would be inappropriate. To protect against major inrushes of high pressure water in the rock, an extensive program of pre-grouting from the surface was specified. Water control in the sediments was left to the discretion of the contractor and in each case freezing was choosen. This paper describes in detail the grouting and freezing procedures.

Jan 1, 1985

By Orlando Bernal

El presente texto aborda el aspecto termodinámico del sistema de lixiviación -en tanto predice los fenómenos que ocurren en el interior de la pila para luego continuar con el análisis del mecanismo cinético. La metodología aplicada en cuanto a los mecanismos de lixiviación, difiere de otros trabajos porque aquí se considera los tres mecanismos por separado (óxidos, sulfuros secundarios y primarios) basados en el análisis secuencial del cobre. Asímismo la cinética per se obedece las leyes de la termodinámica ergo, cuyo aspecto no puede ser ignorado en un análisis global. En este sentido, se presenta el modelo de desarrollo matemático como una herramienta óptima que controla y predice este proceso del lixiviación por medio de la simulación utilizando la ecuación de continuidad, la cual supone flujo tipo pistón de la fase líquida en el interior de la pila.

Sep 9, 2007

By Jorge Castillo

This paper presents a dynamic analyses of heap leach pad stability under high phreatic levels and various levels of seismic loading. The dynamic analysis were conducted as fully non-linear two dimensional analyses with fully coupled liquefaction triggering using the Fast Lagrangian Analysis of Continua (FLAC) computer code. Also, the geotechnical parameters, appropriate earthquake record selection and modification, model calibration, numerical analyses and results are discussed.

Sep 12, 2005

By Fookes R. A, Gardner K. J, Gravitis V. L, Watt J. S, Steffner E. J

Two radioisotope techniques suitable for the rapid laboratory determination of the ash content of coal have been tested ou unwashed coal samples from four Australian coal seams. In one techniqne, measurements of backscattered 238Pu L X-rays and iron K X-rays from finely ground coal samples have been combined to determine ash content in uuwashed coals to ±0.5 weight per ce111 ash (ls) for three seams and 0.9 weight per cent ash for the fourth.The second technique, which involves measurements of the transmission by the coal of narrow beams of 241Am 60 keV and 123Ba 356 keV ? rays, requires less sample preparat ion. The ash was determined to within the range of 0.8 to 2.6 weight per cent for the four seams (unwashed coal). For washed coals, errors are expected to be < ±0.5 weight per cent ash.

Jan 1, 1982

By E. R. Bauer

In response to the mandates in the MINER Act of 2006, NIOSH conducted refuge alternatives research that included characterizing the utility, practicality and survivability of refuge chambers and outby safe havens. NIOSH also prepared and delivered a report to Congress in late December 2007 that summarized the findings of the research, included recommendations concerning the design and performance specifications for refuge alternatives, and focused on specific information that could inform the regulatory process on refuge alternatives. This document highlights NIOSH's research and recommendations concerning refuge alternatives, survivability evaluations of refuge chambers, and presents a brief review of the current deployment of refuge chambers in underground coal mines in the U.S. The research has lead to the conclusion that refuge alternatives have the potential for saving the lives of mine workers if they are part of a comprehensive escape and rescue plan, and if appropriate training is provided. DISCLAIMER: ?The findings and conclusions in this report have not been formally disseminated by the National Institute for Occupational Safety and Health and should not be construed to represent any agency determination or policy.?

Jan 1, 2009