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By John Ellenberger

The nature of a stone deposit is rarely defined through exploration and engineering design, but more through the actual experience encountered as the mine develops; hence, issues with ground control are often at the forefront for a new mine. Ground control problems account for over 15 percent of lost-time injuries in underground stone mines. The objective of this work is to present actions taken during early development of a stone mine to mitigate the obvious effects of high horizontal stress on ground control. The mine was developed from a box cut with relatively little cover, and high horizontal stresses were not anticipated. Early recognition of possible high horizontal stress resulted in mapping of the mine using the NIOSH-developed Roof Fall Risk Index (RFRI) to provide a baseline to objectively analyze roof conditions. A program of borescoping the mine roof provided valuable roof beam thickness data and found that the roof beam was of minimal thickness, approximately 10 percent of drift width. As the mine developed, it became apparent that ground control problems related to high horizontal stress existed. A concentrated effort was made to improve ground conditions by implemeting a number of mitigation techniques. Actions taken by the mine included systematic roof support, reorientation of mining direction, a lower roof horizon, reduced span widths and reduced mining height in crosscuts to prevent running falls. These strategies resulted in signifcantly improved ground stability.

Jan 1, 2012

By Omid Lashkari

Keywords: SEED, SSM materials, Microstructural evolution, Rheology, Swirling Speed SEED (Swirled Enthalpy Equilibration Device) is established itself as a new technology amongst the many Semi-Solid Metal (SSM) processes, where swirling of the mush plays an important role in modifying the dendritic structure of as-cast parts. A range of semi solid metal structures, dendritic, rosette and/or globular morphology of primary phase, can be prepared using SEED. The current article reports on the application of rheological tests in characterizing microstructural evolution during SSM processing of 356 Al-Si foundry alloy. A simple parallel plate test machine, designed and constructed at our labs, was used to determine viscosity values for each structure and identify the optimum structure with superior die filling characteristics. Such findings have important technological and economical implications during high pressure die casting of semi- solid metals. The strain-time graphs for 356 Al-Si foundry alloy indicated lower viscosity values for globular microstructure, i.e. improved die filling.

Jan 1, 2005

By Chen Xia, G. Deschenes, Wan-Tai Yen

"Ammonium thiosulphate is a potential replacement for the cyanide in gold leaching. However, the high reagent consumption hinders its practical applications. In order to reduce the thiosulphate consumption, chemical additives were used. The gold leaching tests were conducted on a sulphide copper-bearing gold ore with 0.3M thiosulphate, 0.03M copper sulphate and 3M ammonium hydroxide solution at 44% solids and pH 10.2. Sulphate, sulphite, amino acid and chelating agents were initially used as additives. It was found that chelating agents (EDTA and NTA) could reduce the thiosulphate consumption from 30 kg/t to 17.8 kg/t with some increase of gold extraction. The improvement from other additives was not significant. Other approaches were also attempted to reduce thiosulphate consumption with some success. The thiosulphate consumption could be reduced to about 17 kg/t by reducing copper sulphate concentration fiom 0.03M to 0.0015M; adding 0.04M of EDTA; replacing copper sulphate with 0.001M of nickel sulphate. The increase of pulp density fkom 44% to 60% solids could reduce the thiosulphate consumption to 17 kg/t as well. Limiting the dissolved oxygen content by sparging nitrogen reduced the thiosulphate consumption further to 10 kg/t. It could be concluded that the regulations of copper and oxygen supply in the lixiviant were the keys to reduce the reagent consumption.INTRODUCTIONCyanidation, as the predominant gold leaching method, has been used in mining industry for more than a century. The low reagent requirement and the high performance are the reasons for its great success. However, cyanidation cannot deal with ores containing large amount of copper, nickel, arsenic and zinc minerals. This type of ore may consume more reagents and result in a poor gold extraction. On the other hand, the carbonaceous materials may preg-rob the gold from pregnant solution and make cyanidation a problem leaching method. Further more, the high toxicity of cyanide represents another challenge to modern gold mines. In the beginning of the year 2000, an environmental disaster caused by an accidental spill in Yugoslavia was broadcasted world-widely (Gurevitch 2000). Gold mine operators are facing higher social pressures and increasing costs on environmental protections. The usage of cyanide in mining industry has been banned in some countries and locations such as Czech Republic, Japan, Turkey, California, Colorado, Wisconsin and Montana States. Thus, a non-cyanide lixiviant is required."

Jan 1, 2002

By Jones S. C

A specific arc can be cut in hard rock formations using a specially designed multistep piloI bit, variable sized drift joint and long heavy control rod as a stabilizer rather than the Vaughan Thompson "Lifting" arc cuttingequipment. The rate of deflection can be controlled after an initial determination of behaviour in any particular rock type.

Jan 1, 1966

By Robert Hopler

As a part of the depression and rectification work on the Port Morris branch of the Harlem Division of the New York Central & Hudson River Railroad, a short tunnel is being driven under St. Mary’s Park. The park is near 149th St. and St. Ann’s Ave., in the Borough of the Bronx, New York City.

Jan 1, 2006

By S. Krukowski

Iodine is a bluish-black, crystalline solid with sub-metallic luster, and has a specific gravity of 4.93. It volatilizes (sublimates) at ordinary temperatures into a blue-violet gas that has an irritating odor. Iodine is the least active of the halogens, all of which readily displace it. Only slightly soluble in water, iodine also dissolves in carbon disulfide, carbon tetrachloride and chloroform, giving a deep violet solution. The primary sources for iodine production are sub-surface brines associated with petroleum and natural gas deposits, and as a byproduct from nitrate deposits in Chilean desert caliche. The largest source of iodine is seawater which contains 0.05 ppm, or about 31 Mt (34 million st). Seaweed of the family Laminaria can extract and accumulate up to 0.45 percent iodine on a dry basis. Seaweed was an important source of iodine prior to 1959. However, it remains a significant source of iodine in the diets of many populations throughout the world.

Jan 1, 2005

Open cut mining of the Black Rock chalcocite ore started in 1963. A ground movement monitoring programme was commencing in the early stages of mining when signs of instabilityof the western wall became apparent. Eventually 100.000 cu vd, of overburden Were removed beyond the rim of the western wall in an attempt to stabilize the slope. Subsequent decpenlug and mining till the final batter angle of 45 resulted in deterioration and mining was stopped 38 ft short in the ulltimte design deplh of 520 ft.Investigations showed that the geology of the western wall , was a major factor in the instability of this wall. A block jointed model was made 10 illustrate some of the pehomena observed. Quallatative agreement was found between the model deformation and the field measurements obtained.The results of the monitoring programme clearly show the value of this work In respect to the conlrol of the mining operatIon...

Jan 1, 1968

By F. M. C. C. Vieira

The DEEPMINE Research Programme sought to develop the technology and competence to mine gold safely and profitably at depths of 3 to 5 km. Among the many issues addressed was the stability and support of rockpasses at ultra-depth. It was found that high virgin and mining-induced stresses could cause the walls of rockpasses to spall, leading to the deterioration and failure. A comprehensive programme of numerical modelling was conducted to investigate alternative mining layouts and sequences to ameliorate the problem.

Jan 1, 2005

By Michael J. Lord, Richard H. O. Wagner

"The technologies used in the mineral processing of ores are being increasingly applied to the identification and remediation of metal contaminated industrial, military and landfill sites. The objective of mineral processing treatment of contaminated site material is to restore the value of the land and to concentrate the contaminants into a very small volume of separated material which, depending upon its nature, can be further processed, marketed, or sent to a landfill. A systematic characterisation of the site material is first undertaken. Bench and pilot testing follows to evaluate criteria for metal separation. The testing may examine one or more physical or physico-chemical reprocessing methods, singly or in combination, for the remediation of the test samples. These mineral processing tests determine the % metal removal fiom the soil and the contaminants concentrated from the medium. The usefulness of mineral processing testing for site remediation flowsheet design and execution is illustrated by the case studies presented. This paper will present the test results of three case studies: an industrial site decontamination, the cleanup of a small arms firing range, and the reclamation of property within a landfill.INTRODUCTIONEnvironmental legislation and our society’s quest for a cleaner environment has led to the application of mineral processing expertise and technology for industrial site decontamination, military site cleanup and landfill reclamation. Although the required level of decontamination varies between jurisdictions, a site becomes a candidate for decontamination once the contaminant concentrations are found to exceed the Canadian Council of Ministers of the Environment (CCME) Interim Remediation Criteria for soil (decommissioning guidelines) or applicable provincial guidelines. The objective of mineral processing treatment of contaminated site material is to restore the value of the land and to concentrate the contaminants into a very small volume of separated material which, depending upon its nature, can be further processed, marketed or disposed of in a landfill"

Jan 1, 1999

By A. C. Legg, M. T. Malema

Keywords: Pyrometallurgy, flash, smelting, furnace, nickel, copper, Botswana BCL Limited operates the only Flash Smelting Furnace on the African continent, at Selebi-Phikwe, situated in north-eastern Botswana. The furnace was commissioned in 1973 and produces a high-grade sulphide matte containing nickel, copper and cobalt, which is shipped to refineries in Zimbabwe and Norway for further processing. This paper outlines the recent process improvements and plant expansions that have resulted in a capacity increase from 40 000 to 60 000 tons per annum of metal production.

Jan 1, 2006

By K. Bartholomew

The Functional Performance Equation for ball milling circuits provides plant staff with a new means to improve circuit performance. However, successful execution of a plant processing performance improvement project, with verifiable improvements, requires a significant number of accompanying steps beyond using this equation. In order to identify and articulate all these steps, a study was undertaken with the metallurgical staff from two milling operations and process application specialists from a grinding media manufacturing company. “Task analysis” of improving plant grinding performance was carried out. This analysis identified the required steps, and ultimately yielded a “Plant Grinding Circuit Processing Performance Management/ Improvement System.

Jan 1, 2015

By Mark R. Svinkin

This paper deals with application of the wave equation analysis to determine capacities of piles driven in saturated sandy soils. It shows that pile capacity in sandy soils changes with time after the completion of pile driving and depends on the ground water elevation. In saturated sandy soils the setup coefficient ranges between upper and lower curves represented by power functions. For a reliable prediction of pile capacity wave equation input should be adjusted with soil damping. Back calculation of soil damping from known pile capacity performed for five tested piles shows that skin damping coefficient changes with time in the same manner as the pile capacity and can be represented by the power functions for considered damping models.

Jan 1, 1995

By W. J. Mahoney

A good quality assurance program at a coal mine or power plant is accurate, timely and consistent. The quality analysis is accurate due to a complete sampling of the coal stream loaded into the unit train. The sample analysis is accurate because standardized testing procedures are applied. Once an analysis is completed, the results must be communicated to the electric utility in a timely manner. The electric utility needs the results to better manage the coal inventory at its power plants. A quality assurance program can also help a mine deliver a consistent product to a utility's power plants. The importance of accuracy, timeliness and consistency are based on major changes that are taking place in the electric utility industry.

Jan 1, 1994

By Donald E. Garrett

Sodium sulfate is one of the larger tonnage industrial minerals. A little more than half of this tonnage — 3 Mt/a (3.3 million stpy) of natural product— is recovered from ore deposits. Most of the rest is produced as a byproduct from other manufacturing operations. Sodium sulfate is mined in a variety of ways. These include conventional room-and-pillar mining, strip mining, in situ leaching of thick ore beds, solar evaporation and cooling-crystallization of lake brine, and the pumping of brine from complex salt deposits. There is also a variety of commercial sodium sulfate ore sources. They include thenardite (the mineral form of sodium sulfate, or Na2SO4), mirabilite (glauber salt,Na2SO4•10H2O), glauberite (Na2SO4•CaSO4), astra-kanite (bloedite; Na2SO4•MgSO4•4H2O), burkeite(2Na2SO4•Na2CO3), sodium sulfate-containing caliche and various brines.

Jan 1, 2002

An extensive laboratory grinding study was carried out on a magnetite ore in order to assess the grinding behaviour of magnetic concentrate and tail from low intensity magnetic separation (LIMS).The test work involved Bond ball mill testing, rod milling, low intensity magnetic separation (LIMS), and batch ball milling down to product sizes of around P80~25 microns. A total of 18 Bond tests and over 150 batch grinding tests and sieve sizing were carried out. Throughout the grinding tests, power draw was continuously monitored. The relationship between the grinding energy and product size was analysed using the conventional energy-size concepts. It was found that the Rittinger equation fits the experimental data well. However, Bond?s equation does not fit the experimental data well, and therefore a modified Bond equation was developed. Differences in grinding properties between the magnetic and non-magnetic component were analysed and compared to the bulk ore. It was found that grinding properties differ significantly and therefore separate grinding test work may be required for each grinding step in the magnetite ore beneficiation flowsheet. Keywords: grinding, iron ores, particle size, modelling.

Jan 1, 2010

By Nicholas G. Theofilos

The Bahamian economy weathered the worldwide recession of the last few years better than most developing countries. This was mainly owing to the ties between the tourist industry of the Bahamas and the U.S. economy. The mineral industry played a minor role in the country's economy. The chief mineral exports included an increasing amount of petroleum products horn the country?s 500,000-barrel-per-day refinery, steel pipe, salt, and aragonite. A 60,001)-barrel-per-day desulfurization facility was completed by Bahamas Oil Refinery Co. (BORCO) in Freeport. The project included vacuum gas oil desulfurization, hydrogen and sulfur recovery, steam generation, water desalinization, and offsite facilities.

Jan 1, 1980

By G A. Ekama

This paper describes a novel system for the biological sulfate reduction (BSR) of acid mine drainage (AMD) using primary sewage sludge (PSS) as carbon source in an upflow anaerobic sludge bed (UASB) reactor configuration. A UASB reactor was operated at a temperature of 35¦C and it received PSS (1875 mg/L COD) augmented with sulfate (1500 mg/L SO42-). The experimental results indicate that a high treatment efficiency was achieved at more than 90 per cent sulfate reduction at a liquid hydraulic retention time (HRT) of 13.5 h. In this study, the effects of various operational parameters were also investigated. The effect of a biomass recycle stream from the top to the bottom of the sludge bed was found to initiate rapid BSR from the bottom of the bed. Profile tests showed that effective and immediate sulfate reduction was achieved as soon as the influent entered the reactor. From these results, it can be concluded that the UASB configuration using PSS as energy source would be a viable method for the BSR of AMD.

Jan 1, 2009

By G. van Aswegen

The geometry and morphology of a set of low-angle fractures around a stope in a deep Witwatersrand gold mine are explained in terms of extension fractures forming under variable conditions of stress. Primary extension fractures (E1) form some distance ahead of an advancing stope along the s1, s2 plane. With stope advance, a couple of these fractures end up in a stress regime conducive to transpressional shear and a secondary set of extension fractures(E2) is formed at a high angle to the primary fractures. i.e. at a low angle to the stope. As the E2 fractures are undermined, they migrate into a stress regime of transtensional shear and a third set of extension fractures (E3) may develop between E2 fractures. These have sigmoidal shapes, being parallel to the E2 fractures at the E2 discontinuity where s3 is negative, and curved through the un-fractured rock between E2 fractures where s3 is positive at the instant of fracturing. The fractures all display fractographic features characteristic of dynamic extension failure with striae indicative of the direction of rupture propagation and the local, instantaneous orientation of s1.

Jan 1, 2012

By Janet Torma-Krajewski

Research has shown that an ergonomics process that identifies risk factors, devises solutions to reduce musculoskeletal disorders (MSDs), and evaluates the effectiveness of the solutions can lower worker exposure to risk factors and MSDs and improve productivity. A review of the Mine Safety and Health Administration (MSHA) injury/illness database indicated that 46% of illnesses in 2004 were associated with repetitive trauma and 35% of nonfatal lost days involved material handling during 2001? 2004. Even though these statistics show that MSDs significantly contribute to occupational illnesses and injuries in the U.S. mining industry, few mining companies have implemented an ergonomics process. Despite the many unique challenges in the mining environment, three mining companies partnered with the MSD Prevention Team at the National Institute for Occupational Safety and Health?s Pittsburgh Research Laboratory to demonstrate that an ergonomics process could be systematically implemented and effectively integrated with existing safety and health programs. Because these three mining companies were very different in organization, culture, and size, the ergonomics processes had to be modified to meet the needs of each company. A description of how these three companies applied ergonomics and the tools and training used to implement their processes is given. Prior to discussing the case studies, general information on the elements of an ergonomics process is provided.

Feb 1, 2009

By Brad Wells, Wayne Bull, Wayne Dickinson

"Antiscalants were evaluated for control of calcium carbonate (CaCO3) in gold processing applications. Under severely supersaturated conditions, 100 percent inhibition was achieved with 30 ppm antiscalant. Laboratory and field testing established that an antiscalant could both inhibit scale buildup and remove an estimated 0.5 kg/m2 per annum of pre-existing scale. A program was developed to control CaCO3 at a gold mill experiencing severe scale buildup. Annual accumulation of as much as 3 cm of scale in process piping was reduced to unmeasureable levels when 10 ppm antiscalant was applied. No scale-related upsets in mill operation occurred during a five-month trial period.INTRODUCTION Inorganic mineral scale is a crystalline deposit that forms when dissolved mineral constituents exceed the solubility of the respective mineral phase. Formation of mineral scale adversely affects a wide range of industries and is of particular interest in mining and metals processing. Scale affects numerous stages of metal extraction processes. Restricted flow in piping, nozzles, valves, screens, pumps and other components used to transport mineral slurries, metal concentrates, and tailings as well as scale in millwater and thickener overflow circuits are primary concerns (Alfano & Boffardi, 1994). Heap leaching, comminuation, flotation, vat leaching, carbon adsorption, and heat exchangers as well as oxidation steps used in processing sulfidic ores are among key unit operations that may be adversely affected (Simmons & Gathje, 2003). Antiscalant chemicals are designed to prevent formation and growth of mineral scales such as CaCO3. These chemicals, which include two primary classes – phosphonates and anionic carboxylate polymers and copolymers - are added to the gold processing stream at low parts-per-million (ppm) concentrations to interfere with nucleation and growth of scale forming crystals and to disperse fine particulate material. Application points may be located throughout the gold extraction process. Evaluation of the performance of antiscalants plays a critical role in determining the best product for a specific application. Performance evaluations include laboratory testing, pilot scale studies, in-plant trials, and ongoing performance monitoring during mill operation."

Jan 1, 2014