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By J. Nielen van der Merwe

This investigation was done to develop a method to predict the lie of coal pillars. It has long since been known that coal pillars deteriorate over time, but there was no method to quantify the deterioration. It was found that the rate of pillar deterioration was essentially a function of two parameters, namely mining height and time. The higher the mining height, the more rapidly the pillars deteriorated. The rate of deterioration is not constant, but decreases exponentially with time. The pillar life should be viewed in conjunction with the safety factor. While the relationship between safety factor and pillar life is ambiguous, the trend is nonetheless for higher safety factor pillars to have longer lives. The safety factor can be used to quantify a failure probability. The pillar life prediction indicates when the pillars which are predicted to fail, can be expected to do so.

Jan 1, 1998

By R. K. McLimans, C. Knudsen, S. Bernstein, D. Frei

Computer Controlled Scanning Electron Microscopy (CCSEM) is used to analyze indivdual mineral fractions in heavy mineral sands. CCSEM is a fully automated particle analysis technique for the determination of physical and chemical properties of a large number of individual particles. CCSEM enables the precise and accurate determination of the modal abundances of individual mineral fractions (e.g. ilmenite, rutile, zircon, or garnet), their average chemical composition (and compositional variation), as well as their physical properties such as size (e.g. diameter and perimeter length) and shape (aspect ratio and circularity). A unique sample preparation procedure is used to produce representative polished sections from cylinders of raw sand samples such that thousands of grains are present in a polished cross section, but grains are not touching. The combination of this sample preparation technique with CCSEM enables the fully automated analysis of individual grains without the application of de-agglomeration or erosion steps to separate touching particles. Hence, CCSEM yields information representative of the entire area of analyzed grains without systematic bias due to neglect of rim areas by de-agglomeration or erosion steps. Therefore, the resulting data are determined with high accuracy, precision and statistical validity. Because the sample preparation is relatively straightforward, using raw sand samples, and all chemical and physical properties are determined in one analytical session per sample, CCSEM is a powerful cost and time efficient tool for characterizing chemical and physical properties of minerals in heavy mineral sand deposits.

Jan 1, 2005

The process of electrostatic separation was developed in the late 19th century, but did not make much headway for about 25 years. High dc voltages, of the order of 20 kilovolts, are involved, and the only means of obtaining such voltages at that time were by the use of frictional machines, such as the Wimshurst. These were not reliable, for two reasons:-a. If a spark discharge occurred it took an appreciable time before a steady voltage was again attained.b. In damp weather the machines were almost useless.In the first 20 years of the 20th century the advent of mechanical and vacuum-tube rectifiers led to promising developments of 'the process. In the early 1920's flotation became widely used commercially, and proved to be more reliable, and capable of wider application, than electrostatic separation. During the last 15 years or so, with a better knowledge of the fundamentals forming the basis of the process, electrostatic separation is beginning to compete with flotation, especially in the treatment of smallsizedgranular material, such as beach sands. Electrostatic separation can be, and is, widely used in many cases where flotation is impossible, such as in the cleaning of food products which must be kept dry.

Jan 1, 1950

By T BoBo, D La Rosa, P Cameron

Efficient pre-concentration using natural and induced deportment starts with effective blast design. Leveraging these characteristics using Size-Based Grade Engineering® techniques requires detailed understanding and measurement of the particle size distribution (PSD) of the Run of Mine (ROM) ore. In turn, blasts must be designed to optimise fragmentation for the pre-concentration method. To be successful, fragmentation outcomes must be predicted and measured as part of the blast design process to account for the response ranking of the rock mass. The upgrade achieved using Size-Based Grade Engineering® methodologies will rely on the proportion of feed that reports to the screen undersize, so particle size distribution of the feed stock is of paramount importance if the potential benefits are to be achieved and maintained. Measuring actual fragmentation in the ROM ore and comparing with predictions allows the modification of subsequent blast designs to optimise fragmentation for pre-concentration scenarios. Automating this process can deliver significant increases in productivity and mine site profits. This paper discusses the importance fragmentation plays in Size-Based Grade Engineering® and explores technologies and methodologies used to measure it, consistently ensuring the best outcomes.

Nov 10, 2020

Acid soluble calcium is depleted in drainage sediments from hydrothermal alteration centres in the Coromandel Peninsula. The routine analysis of acid-soluble calcium on drainage samples is an economical and effective technique for outlining hydrothermal alteration centres in volcanic terrains.

Jan 1, 1979

By Ken MacLeod

A development at 83 Queens Road in Melbourne, Australia required construction of a three level basement. The normal geotechnical constraints of excavating adjacent to an existing relatively new building were challenging enough for the complicated soils profile occurring at the site. An additional significant challenge faced by the designers, was the requirement to excavate underneath the entire footprint of an existing heritage listed building, known locally as the Mansion, in the centre of the site. Maintaining the structural integrity of that building was afforded the highest priority during the 10m excavation. This paper describes geotechnical aspects of the analysis, design and construction of the secant retention system adjacent the new building and support of the Mansion enabling the 10m excavation to proceed without causing damage to the structure. The secant wall comprised hard-soft interlocking piles constructed using CFA methods. CFA piles along the length of the Mansion provided short term support, with the building load being transferred to the piles by large steel beams jacked under the building. Survey results confirmed that movements of the retaining wall and also the load bearing piles were minimal and well within design expectations.

Jan 1, 2006

By A. Nieto

A vehicle proximity warning–collision avoidance system is being developed using GPS and wireless local area networks to improve safety of off-highway trucks in open pit mines. After two-and a-half years of research, software development, and laboratory testing, field tests were carried out at operating limestone quarries and open pit mining operations to evaluate GPS accuracy and overall system effectiveness under rugged operating conditions. This article describes the progress made on this NIOSH-funded project and discusses the GPS accuracy tests and overall system tests that were carried out during the year 2001 at the Colorado School of Mines Survey Field and at the Morenci open pit copper mine in Arizona. Keywords: GPS, Advanced Mining, Virtual Reality, Wireless Networks, Proximity Warning

Jan 1, 2003

By P. R. Day, W. K. Webster

"The introduction of large boreholes underground initially involved taking the techniques of open-pit bench blasting to the production stope, but with deeper boreholes and narrower stopes more controlled techniques must be developed in order to maintain good stope walls and prevent dilution of ore or structural damage to pillars due to blasting overbreak. The points discussed are drilling accuracy and drill pattern, the relationship between open-pit wall control and underground mining, the varied explosives products and initiation devices available, and some of the many ways that variations in loading, such as deck charging, etc., can produce desirable results.IntroductionThe use of large-diameter blastholes for underground mining began ten years ago and today they are widely employed in a variety of orebodies and stope configurations. These big blastholes, which range in size from 4.5 to 8 inches in diameter, were originally employed in the same manner ' as open-pit bench blasts; that is, the stope was silled out to full width and all holes were drilled vertical and parallel. This was suitable for competent, massive orebodies, however the popularity of the big drills saw their usage in more narrow stopes, often with poor ground conditions. The dipping orebodies and small drill sublevels resulted in inclined drilling.Today, there is full-ring drilling of 4.5-inch holes. Some 6.5-inch holes are drilled up to 350 feet deep. A 350-foot borehole may contain 6000 to 7000 pounds of explosive. The detonation of this size of charge weight within the confines of an underground stope can have considerable effect on the stability of stope walls and adjacent pillars. Obviously, precautions must be taken to minimize the damage which would result from the large charge weights possible with these big boreholes."

Jan 1, 1982

By Chelsea Woodward

The Spokane Research Laboratory of the National Institute for Occupational Safety and Health has demonstrated a prototype hydrogen-fueled mining vehicle as an alternative to diesel equipment in underground mines. Safety and control systems were added to allow a 70-kW rubber-tired hydrogen vehicle, originally developed by the U. S. Bureau of Mines and Hydrogen Consultants, Inc. (now Hydrogen Components, Inc., of Littleton, CO), to be tested. This work began in late 2000 and culminated with a Mine Safety and Health Administration fire safety review and field tests at the Stillwater Mine in Nye, MT, in 2004.

Jan 1, 2006

By S. Makni, A. Faucher, F. Robichaud, A. Bouajila

"Optimizing the ball charge in a grinding mill may be needed to maximise throughput or alternatively, to achieve proper product size in more challenging situations. Efforts to optimise the ball charge however are essentially empirical and suffer from the lack of appropriate, accessible and reliable tools. To address these limitations, a new model-based technology was developed that relies on 3D Discrete Element Method and population balance techniques: it takes on the form of a simulator that aims to significantly decrease the time required to optimise the size distribution and the grinding media load within a ball mill. This paper summarizes the research work related to the development of this simulator. The calibration of the different constituting sub-models will be highlighted. The successful use of the simulator to predict the effect of ball make-up on the grinding product size distribution in one plant is also reported.INTRODUCTION Adjusting the characteristics of the grinding media charge in grinding mills holds significant potential for optimisation of mill performance. For example, properly adjusting the ball size distribution in a ball mill can help achieving specified targets for final product size distribution and/or throughput capacity. However, several problems appear when reviewing the process and the available tools to optimise ball mill load: • The current empirical simulation tools are lacking with regard to the ability to predict the performance of grinding when changes to mill ball make-up are made; • Generally, these tools estimate the top size of the charge so it is difficult to predict the effect of mixed ball make-up; • As the quality of prediction of these tools is low, the operators try to optimise the ball charge by a ""trial and error"" method and proceeding with conservative changes. The influence of these changes on grinding performance is often less than the measurement precision and the improvements then remain imperceptible; • A change in ball make-up may require an average of about 6 months waiting period before reaching the stationary state of mill ball load. This exercise is due to be costly if applied change decreases the mill performance. In its effort towards the comminution process optimisation, COREM R&D portfolio had addressed the herein described opportunity during the last five years This paper describes the technology already developed for the optimisation of ball charge. It takes on the form of a simulator that aims to predict the evolution of the grinding media load, the grinding energy available in the ball mill and the final product size distribution. The simulator was first validated in a pilot scale ball mill and then applied in an industrial case."

Jan 1, 2012

By Larry F. Drolet

Charleston, SC is anything but boring. The city was founded in 1670 and has played a significant role throughout the history of the United States. Located along the coast of the Atlantic Ocean in the southeastern United States, Charleston was a vital city in America?s early existence. Charleston?s coastal location has helped the city become the fourth largest cargo port in the United States and earn the 2011 designation as the number one travel destination in the United States by the Conde Nast Traveler Magazine. Part of Charleston?s charm and beauty can be attributed to its historic structures and churches that line nearly every sidewalk, roadways that were laid out based on the width of horse carriages, great weather, southern hospitality and coastal living. Now imagine the challenges of installing new, or re-placing aging infrastructure, in this setting. Every shovel full of dirt, every stick of pipe and every roadway sub-surface has its own historic story to tell. For engineering minded individuals, Charleston?s infrastructure has almost as fascinating a history as its more visible surface structures. Charleston was among one of the first American cities to construct separate sanitary and storm water drainage infrastructure. This concept has roots dating back to the city?s founding and is a credit to the foresight of its founding fathers who understood the basic health differences between sanitary and storm water.

Jan 1, 2013

By P. C. Schutte

There have been several high-profile accidents in the South African mining industry where fatigue was identified as either causal or contributory. The risk of fatigue is inherent in any work-time arrangement involving shift work and work that is physically or mentally demanding, repetitive, or requires high vigilance. The management of fatigue is not simply a matter of correct shift scheduling. Amore comprehensive approach is needed. In order to be successful, a fatigue management programme should address the unique needs of the operation in which it will be implemented and should be integrated into normal operations. Fatigue management is a shared responsibility between the organization and its employees, and all stakeholders should participate in order to provide the safest and healthiest working environment possible.

Jan 1, 2010

By Rosana Silva Xavier

Compósitos magneto-elétricos (ME) combinam fases magnetostrictivas e piezoelétricas e podem ser utilizados na geração de energia a partir de vibrações e campos magnéticos presentes no ambiente, sendo também aplicáveis em sensores de campo magnético e em redes de sensores sem fio. Neste trabalho, um compósito ME foi processado pelo método cerâmico com 15 vol% CoFe2O4 (ferrita de cobalto) como fase magnetostrictiva e 85 vol% BaTiO3 como fase piezoelétrica. É mostrada a relação entre os parâmetros de processamento/sinterização e a microestrutura do compósito ME, com três tipos diferentes de arranjo das fases: particulado (obtido por dois diferentes métodos) e em camadas. Foram compactadas pastilhas dos compósitos para sinterização nas temperaturas de 1.200ºC, 1.300ºC e 1.400ºC por 4h, sendo que ocorreu a fusão da pastilha sinterizada a 1.400ºC. As amostras sinterizadas foram observadas em microscópio eletrônico de varredura (MEV), onde foram analisadas as características de porosidade, tamanho de grão e a distribuição das fases na microestrutura. Foram realizadas também análises cristalográficas por difração de raios-X (DRX), de espectroscopia RAMAN e de espectroscopia de energia dispersiva (EDS). Foram relacionados os parâmetros de processamento utilizados com os resultados obtidos.

Aug 8, 2018

By Daniel P. Lathrop, Leslie C. Taylor, William L. Fourney

Except when the target is on the surface, e.g. a tank track, the most important loading mechanism from a buried charge on a target above it is the impact of soil propelled at the target by the expanding gas from the explosion. Detonation of a shallow buried explosive generally yields an unstable interface between the rising soil and the air which appears to be the result of Richtmyer-Meshkov instability. Irregular “fingers” of saturated sand extend into the air above a more generalized dome of soil. These fingers move at a much higher velocity than the material between them at smaller stand off distances. As a result, the local load on the target at positions on the target at the same distance from the charge may vary by 50% or more from shot to shot or even within a single shot. This variation requires a large design safety factor to assure the integrity of design of mine-resistant vehicles.

Jan 1, 2009

By J. Châteauneuf, R. Dupéré, D. Mrabet

"In gold processing plants, it is common to start gold cyanidation in the grinding circuit by simple cyanide addition or as a result of recycling residual cyanide. In such cases, advantages such as a decrease in gold lockup and reduced leach time have been noticed. The prevailing conditions in grinding circuits such as intense mixing, particle breakage and friction or high temperature are quite different from those found in tanks and so is the resulting cyanidation behaviour. To gain a better understanding of the cyanidation behaviour in mills and of the pertinence of cyanide addition in grinding circuits, lab tests were conducted using an industrial ore from Canadian Malartic mine. In this study, the effects of different parameters on cyanidation in grinding circuits were examined; parameters such as such as temperature, dissolved oxygen, cyanide concentration and pH. The results showed that the kinetic benefits of high temperature in the mill can overcome the low dissolved oxygen concentration thus leading to an overall gold dissolution kinetics improvement for temperatures up to 50°C. However, gold leach in the studied grinding circuit at lab scale caused an increase in cyanide consumption with a higher generation of iron cyanide and SCN-. These results were confirmed by tests in the Canadian Malartic plant where the cyanide addition was moved from the SAG mill to the leaching tanks resulting in a 20% savings in cyanide consumption.IntroductionCyanidation in grinding circuits can benefit gold processing by decreasing gold lockup and by reducing leach time. However, other aspects regarding gold and cyanicide dissolution come into play in the conditions prevailing in grinding circuits. Indeed, high turbulence, high temperature, recycling load, friction and particle breakage make cyanidation behaviour in grinding circuits different from in-tank cyanidation (Marsden and House, 2006). In several cases, cyanide in grinding is limited to a very low level or completely avoided such as in circuits with gravimetric separation, for ores requiring oxidative pretreatment or for preg-robbing ores. In other cases, water management imposes a certain recycling of residual cyanide. This problem is generally addressed by a case-by-case approach. However, the chemistry of cyanidation in mill circuits is worth investigating in order to assess the advantages and disadvantages."

Jan 1, 2016

By Bengt H. Fellenius

.1.1 Prior to commencement of pile installation operation, submit to [Engineer] for [approval] [review], details of equipment for installation of piles. SPEC NOTE: The information requested in 3.1 .1.2 is necessary as input to a detailed wave equation analysis of the pile driving. .1.2 For impact hammers, give manufacturer's name, type, maximum rated energy and rated energy per blow at normal working rate during easy and at termination driving, mass of striking parts of hammer, mass of driving cap, and type and elastic properties of hammer cushion. .1.3 For non-impact methods of installation, such as drilling, jacking, jetting, use of vibratory hammers, or other means, give full details of characteristics necessary to evaluate performance. .2 Impact Hammer SPEC NOTE: Do not exclude a hammer type unless for very specific reason. .2.1 [Drop hammers will not be permitted.] [Diesel hammers will not be permitted.] For final driving of [TYPE] piles, provide a hammer capable of delivering to the pile a non-erratic impact stress not smaller than [VALUE] Pascal and transferring a non-erratic energy not smaller than [VALUE] Joules per blow to the pile head at normal working rate.

Jan 1, 1991

By F. L. Pirkle, D. L. Pirkle, E. C. Pirkle, W. A. Pirkle

Heavy minerals have been mined from the sands of the United States’ Atlantic Coastal Plain since the early part of the twentieth century. Production of ilmenite from beach sands near Mineral City (Ponte Vedra), Florida, began in 1916. The first reported large-scale recovery of zircon in Florida was reported from this deposit in 1922 and of rutile in 1925. These operations ceased in 1929. Today the Ponte Vedra Country Club and Golf Course is situated in the center of the former mining site. In 1942 heavy-mineral operations were established on 202 hectares of land situated in Duval County, Florida. The location is about 16 kilometers east of the center of Jacksonville, Florida, in an area known as Arlington. This operation demonstrated that low-grade sand containing only 2 to 3 percent titanium minerals could be concentrated economically with the Humphreys spiral and that the oxides could be separated from the heavy silicates by electrostatic methods. Much of this area is now covered by a large mall and is a major retail- commercial center. Between 1958 and 1964 the Skinner tract, a deposit about 4 kilometers south of the above deposit, was mined. Today the area of this deposit is known as Deerwood, a gated country club community on the southside of Jacksonville. Further inland, E.I. du Pont de Nemours and Co. has been mining heavy minerals from a physiographic feature known as Trail Ridge since 1948, and a deposit near Green Cove Springs, Florida has been in production since 1972. Since the start of heavy-mineral mining in the southeastern United States, nine heavy-mineral ore bodies either have been or are being exploited in Florida and Georgia. Other deposits either have been lost to mining or are yet to be mined. These deposits have different origins. Some formed along shorelines at the heights of marine transgressions while others formed on regressional beach ridge plains during periods of temporary stillstands or slight transgressions. These different origins are reflected in the chemical and physical characteristics of the deposits. Ilmenite in older, more western deposits has a higher TiO2 content than ilmenite in younger, more eastern deposits. TiO2 content does not very with north-south direction. Garnet and epidote are absent or rare in the older Trail Ridge deposits, but progressively become common in the younger Duval Upland, Crestal Pamlico, and Holocene deposits. Grain size is coarsest for Trail Ridge sediments and finest for sediments in Duval Upland and Crestal Pamlico deposits. The average grain size for Holocene deposits is intermediate between Trail Ridge and Duval Upland deposits. The two models for the origin of the heavy-mineral deposits – deposits formed at the height of major marine transgression; and deposits formed during periods of temporary stillstands or slight transgressions that occur during a general marine regression; - are consistent with known sedimentological data and depositional trends.

Jan 1, 2005

By H. Kenworthy

Laboratory experiments were conducted on several materials to determine their suitability for the production of mineral wool. By blending raw charges in the proper proportions and in some instances by adding lime, acceptable wools were made from samples originating in Alaska, Florida, Texas, and Virginia. It was shown that satisfactory wools can be produced from many kinds of raw materials if the ratios of acidic and basic constituents are properly maintained. INTRODUCTION The Federal Bureau of Mines has facilities at the Mississippi Valley Experiment Station, Rolla, Mo., for examining and testing mineral-wool raw materials. Samples are evaluated through small-scale wool-blowing experiments, aided by petrographic, chemical, and physical analyses of the raw materials and finished wools. When enough experimental data have been accumulated they are made public through Government reports and periodicals. This report of investigations follows that published in 19513/ and presents test data on samples received and examined since 1951.

Jan 1, 1956

By Ruth F. Brinkley

This report is the 18th of a series of reports originally issued annually, and more recently bienially, to acquaint the public with the work of the Federal Bureau of Mines in explosives technology. Part I reviews briefly the overall activities during fiscal years 1957 and 1958.4/ Part II presents in abstract form the publications prepared by the Bureau that appeared during the period.5/

Jan 1, 1961

By D Crequer

A Peer Review Panel for the Golden Cross Mine in the upperWaitekauri Valley, Coromandel was initiated in December 1989, before mining, as a requirement of the conditions of the Mining Licence and Water Rights. The panel's function is as a technical audit and advisory team - to provide independent technical review of design, construction, and execution of mining operations, slope remediation works, and reclamation/mine closure activities. The primary role of the panel is to act in the public interest by providing assurance to regulating authorities that the design and application of on-site mining operations accords with 'good industry practice'. Panellists are not involved in design nor as advisers, although until 1997 when explicit terms of reference were written, the panellists were a sounding board for some operational proposals. The panel functions to ensure that best mining industry technical standards are met. The costs of the peer review process are met by the mining company. Review of mining operations includes environmental matters such as land rehabilitation and water quality. The focus of this paper is on the process of peer review for environmental management factors rather than for structural and mine engineering.

Jan 1, 1998