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By R. H. Estrada-Ruiz

This work analyses a new approach to estimates bubble size distribution of froth surfaces using artificial neural networks (ANN).Also, the robustness of ANN to interpret images with illumination perturbations, produced by light problems or dirt attached to the window of the video camera is evaluated. The experimental work was carried out in a laboratory flotation column, instrumented with an image acquisition system. The images were processed making use of a perceptron model with a hidden layer, sigmoidal transfer function and unitary bias, and the ANN trained with a back propagation algorithm. The results of validation show that ANN are reliable for learning and producing generalized predictions of the froth mean bubble diameter and bubble size distribution, when the model is trained using a database that contains information on the illumination intensity. Keywords: image analysis, neural networks, bubble diameter, bubble size distribution.

Jan 1, 2009

By H. Ewaschuk

"INTRODUCTIONRio Algom's Stanleigh Mill in Elliot Lake began production in June of 1983. The highly instrumented mill treats uranium ore at an average rate of 3900 metric tons per day. To help ensure a good start-up and low operating costs, an extensive training program was undertaken prior to and during start-up. This presentation describes how an unconventional operating crew were combined to form an operating unit with a high efficiency in terms of production and labour utilization. I would like to point out at the outset that the operating philosophy, and the role of the supervisors and the operators as set up at Stanleigh is not unique. Indeed, I have seen the same results at a couple of small plants where efficiency meant survival. However, these situations appeared to be the exception, and it was not readily apparent how similar results could be obtained in a larger plant. A factor that existed at the time was low labour turnover. As in most parts of Canada, jobs were easy to get in the Elliot Lake camp in the late 1970's. This, and other factors, contributed to an unusually high labour turnover. This changed dramatically in the early 1980's. Indeed, Rio's two other operating mills, Quirke and Panel reduced crew sizes at this time to reduce operating costs. As a result all of Stanleigh's operators came from Quirke and Panel with experience varying from 4 to 7 years. The experience that operators had was obviously of benefit and served to reduce the scope of the training program from what would have been required with inexperienced personnel."

Jan 1, 1985

In 1992, the United States economy grew at a rate of 2%. The Gross Domestic Product rose to $5,946 billion. With 257 million people - 635,000 in mining including petroleum - the United States has more than 100 million dwelling units and more than 190 million licensed motor vehicles. New private housing starts rose I 1 % to 1.2 million units. New car production rose 4% to 5.7 million units. Truck and bus production rose 20% to 4 million units. The rate of inflation was 3.5% and the prime rate of interest was 6.25%. The Producer Price Index (1982 =100) was relatively unchanged from 1991 as follows: fuels and related products and power 80, metals and metal products 119, chemicals and allied products 126 and nonmetallic mineral products 117. Energy Imports of crude and refined petroleum, costing $50 billion, rose 3% to 455 Mm3 (2.9 billion bbl). Domestic petroleum production fell 1 % to 582 Mm3 (3.5 billion bbl). Petroleum supplied about 41 % of US energy, natural gas 24% and coal 23%. Coal production, 60% from surface operations, rose 1 % to 914 Mt (1 billion st). About 78% was used to generate electricity and 3% was coked. Exports valued at $4 billion included 57 Mt (63 million st) of metallurgical coal and 39 Mt (43 million st) of steam coal. Ura¬nium mining, including recovery from phosphates, fell 18% to 3 kt (3300 st) U308.

Jan 1, 1993

By Meghan McGrath

Third generation advance high strength steels with microstructures of acicular ferrite and retained austenite were investigated and meet mechanical property goals. A good combination of strength and ductility were achieved with duplex ferrite and austenite microstructures where cementite formation was suppressed. Transformation induced plasticity (TRIP) behavior produced rapid work hardening. The mechanical properties of two hot-rolled steels with duplex microstructures were compared and had the following compositions: (1) Fe-0.14C-13.87Mn-1.42Si-3.51Al; and (2) Fe-0.06C-14.2Mn-1.85Si-2.38Al. These steels were cast, homogenized, and hot rolled at 900ºC to obtain a refined microstructure with ultimate tensile strengths and elongations to failure of 865 MPa and 39% and 1,217 MPa and 28%, respectively. The amount of metastable austenite in both compositions decreased after tensile testing from 58% and 28% to 6% and 0%, respectively. Microstructures were characterized using optical microscopy, scanning electron microscopy (SEM), and x-ray diffraction.

Jan 1, 2010

By Jim Britton

Sustained elevated metal and coal prices in 2011 continued to drive mining projects across British Columbia. The province is the top producer of copper, exporter of coal and the only producer of molybdenum in Canada. The province also produces significant amounts of gold, silver, lead and zinc and more than 30 industrial minerals. The total 2011 value of solid metal production is an estimated $8.6 billion and the outlook for 2012 is positive. British Columbia is poised to bring several new mines onstream in the next few years. Construction continues at the New Afton and Mt Milligan copper-gold projects that are anticipated to be open in 2012 and 2013, respectively. The provincial Environmental Assessment Office indicates there are 26 mine proposals in process with three currently under review and 23 in the preapplication stage. The following text briefly describes 2011 metal and coal mining activities in the five regions reported on by the provinces? regional geologists (Fig. 1).

Jan 1, 2012

By Sanjeeva Latchireddi

"Deteriorating ore grade and high demand of metals has tremendously influenced the unit capacity of SAG mills. Pebble circuits have been added to the existing SAG circuits to increase their unit capacity. To make the pebble circuits justifiable, the grate openings are increased almost to 4.5 inches to draw large quantity of pebbles. The inherent transportation problems associated with SAG mills in closed circuit with pebble fraction are more complicated than the single stage SAG mill operation, because the coarse pebbles behave significantly different to that of slurry in pulp lifters. In addition, operation of mills at higher speed, to take advantage of precise design of high release angled shell lifters significantly reduces the discharge efficiency of the conventional pulp dischargers. The presence of a sizable quantity of pebbles in the pulp lifter limits the space available and reduces the flow gradient through the grate thus increases the load inside the mill and hence the mill power-draw. This paper analyses all the problems associated in discharge of slurry and pebbles in SAG mills with pebble circuits. The Outokumpu patented Turbo Pulp Lifter (TPLTM) aims at eliminating the inherent material transport problems to ensure good grinding conditions. Recent installation of TPLTM in a 26-ft SAG mill has proven these claims by reducing the specific power consumption while increasing the mill capacity.INTRODUCTIONThe conventional wisdom is to look at the semi-autogenous grinding (SAG) mill as just another grinding mill in which ball charge, mill filling, and mill speed are varied to attain maximum throughput. Liner design for the SAG was also approached more from a wear perspective rather than a metallurgical and hydraulic-flow perspective. The extensive research work carried out by Latchireddi and Morrell (1997,2003a and 2003b) has demonstrated to think of the SAG as more of a pump in which the grates and pulp discharger end (“impeller”) were designed to efficiently discharge the product sized particles smaller than the grate size with minimal recirculation out of the mill.The rock load in the mill is essentially depends on ore characteristics and the discharge rate of broken particles. The discharge rate of the product material depends on how efficiently the discharge pump (grate and pulp lifters) is operating. Similar to the impeller design affecting the pump capacity, the pulp lifter design affects the discharge capacity (or mill throughput) of the SAG/AG grinding mills. The general arrangement of AG/SAG mills discharge system is shown in Figure 1."

Jan 1, 2007

By G. Swan, E. Nordlund, P. Zhang

"SynopsisThe most widely used support design damage criterion for rockburst-prone mines is based upon kinetic energy, which is proportional to the square of the ejection velocity and is commonly expressed in terms of peak particle velocity (PPV). Field monitoring and back-analyses have shown that ejection velocities of the order of 10 m/s and higher can result from seismic events of moderate magnitude. Such velocities are much higher than those predicted using PPV obtained from scaling laws. It has also been found that the peak ground motion (i.e. PPV) on the surface of an excavation is preferentially amplified (by four- to tenfold) compared to the motion in solid rock at a similar distance from the source. However, the wave propagation and interaction processes involved within the fractured rock in generating high ground motion are very complex and are not well understood at this time.In this paper, velocity amplification was investigated by modelling the dynamic interaction between fractured rock and a free surface using a 2D discontinuum-based numerical program, UDEC (Universal Distinct Element Code). A 1D model with a fractured zone was used to represent the fractured rock. Velocity amplification, quantified by PPV, predicted at the free end of the model was 2.0–3.6 times higher than the input velocity. It was found that the wave frequency, fracture stiffness, fracture spacing, and thickness of fractured zone are the main factors that affect the velocity amplification. The results have proved that the interaction of the seismic wave and multiple fractures near the free surface strongly influences the ground motion.IntroductionSince mining-induced seismicity is almost inevitable in deep mines, ground support is generally employed to mitigate the risk of seismically-induced damage. The most widely used support design criterion for seismicallyprone mines is one that seeks to maximize the absorption of the kinetic energy (plus potential energy if a gravity component is considered) of key rock blocks. Based on this criterion, design methods for rock support were first proposed by Wagner (1984) in South Africa and later improved, among others, by Roberts and Brummer (1988) and Kaiser et al. (1996)."

Jan 1, 2015

By Staff

A major emphasis of the U.S. Bureau of Mines is to perform research on the prevention of fatal accidents at mining operations. The leading cause of fatalities in the underground coal mining industry is groundfalls. This proceedings volume presents several new developments that are helping to prevent fatalities and reduce injuries by groundfalls. The papers focus on the problem from two different perspectives. About half of the papers present information and techniques that can be used to train and motivate miners to protect themselves from groundfalls. The other papers explain how to identify and respond to various geologic conditions that affect the stability of the mine roof. Of the 95 groundfall fatalities that occurred during 1986-90, 75% took place in Kentucky, West Virginia, and Virginia. The rate of groundfall fatalities was much higher at small mines. During 1986-90, the rate of groundfall fatalities at mines employing fewer than 20 people was 4.3 times higher than the rate for larger mines. Because so many groundfall fatalities are occurring at relatively small mines in the southern Appalachian coalfields, many of the papers focus specifically on the needs of this category of mine operations.

Jan 1, 1992

By J. -P. Chilès

The discrete Gaussian model is a very popular change-of-support model for estimating block grade distributions. It is designed for a stationary random function Z(x) that is regarded as the transform of a stationary random function Y(x) with Gaussian marginal. It is based on an assumption that is not fully true and thus constitutes an approximation to the exact solution. We examine the effect of this approximation on the modelling of the marginal distribution of block values of a lognormal random function. The initial discrete Gaussian model and a variant of that model are considered.

Jan 1, 2014

By T. Cyrul

The Polish underground mining has its long lasting tradition. High production of coal, that has recently been approaching 200 milion tons per year, put this small country among the bigest world producers of coal. To achieve such a high production, which mainly originate from very unfavourable mining and geological conditions, Polish scientists and engineers have to introduce new and original solutions to the mining practice. Many of the solutions on mining methods, ventilation, stability, subsidence etc., have had the world wide reputation, however, insufficient translations from Polish cause , that many of the recent Polish mining achievements are not known to foreign specialists.

Jan 1, 1986

The safety analysis of shaft-sinking operations included a review of accident reports from coal and metal-nonmetallic mine shaft-sinking projects in the United States, a review of foreign and domestic shaft laws, and discussions with shaft contractors and Federal mine inspectors. Accident data were studied to identify the most common and the most severe types of shaft accidents and to determine their immediate and contributing causes. Additional factors such as worker training and experience, equipment and sinking procedures, regulations and enforcement practices were also investigated to determine their impact on shaft safety. The results of the study are summarized in recommendations for improved training of shaft miners and clarification of Federal shaft-sinking regulations. A guide to assist mine inspectors in examining shaft-sinking projects is also included.

Jan 1, 1977

By C. Patel, George H. Hope

"INTRODUCTIONThe Hemlo area is located in Northern Ontario, some 350 km east of Thunder Bay along highway 17. Hemlo is Canada's largest, recent discovery of gold ore. Three companies, Lac, Noranda, and Teck are currently developing mines and processing facilities in the area. A combined milling capacity of approximately 10,000 tonnes per day will ultimately be available in the area. The gold yield will be between 750,000 to 1,000,000 ozs. per year. This will slightly more than double Ontario's gold production but only represents 2.5% of the total world gold production.Lac Minerals Ltd. is substantially committed to the gold mining business. Lac currently operates four (4) gold mines and mills and produces 300,000 ozs. per year. Lac's Hemlo development will put the company in the position of number one gold producer in Canada.The Lac Hemlo ore body has an estimated reserve of 37 million tonnes at 6.2 g/t. The mining will take place at an initial rate of 3,000 t/d commencing in the first quarter of 1986. The mine and plant will be expanded to 6,000 t/d in 1988. At this capacity, Lac will be the largest producer in the Hemlo area.1. GEOLOGYThe orebody is divided into two (2) zones for mining purposes. The 'A' Zone is to the east and dips to the Northeast from surface to 300 m below surface. This zone has a strike length of 250 m to 300 m at an average width of 20 m. The upperpart of the zone will be mined by open pit and the remainder from underground. The 'B' Zone, to the north west of the 'A' Zone, although lined up is not necessarily an extension of 'A' Zone. 'B' Zone has a known strike length of 600 m and is open to depth and along the strike. It is over 70 m wide in the core. This zone holds most of the property's known reserves. 'C' Zone with narrow gold zones is under exploration in the south west portion of the property."

Jan 1, 1985

By J. E. Hawley, Y. Rimsaite, T. V. Lord

"IntroductionIN THE COURSE of. a spectrographic investigation of the platinum metal .content of various minerals in sulphide ores, the use of • fire-assay beads dissolved in gold-amalgam ( 1) was found suitable for the quantitative determination of palladium and platinum. Later work on platinum and bismuth-rich beads showed however, that these could not always be readily mixed uniformly in the amalgam. Accordingly another technique was sought which would allow the simultaneous determination of gold, silver, palladium, platinum, rhodium, and bismuth, the last .a common contaminant in fire-assay beads. The method evolved, which consists of dissolving fire-assay •beads in .lead, resembles in several respects the method of Scobie (2) in which silver was used. It has equally good sensitivity arid reproducibility, and allows the determination of silver as well as the other metals mentioned. The 'mutua1 standard' method of calculation (3a) is used to determine actual quantities present. This method has been applied to sulphide and arsenide minerals and •ores• of nickeliferous and non-nickelferous deposits• of both pre-and post Cambrian age, and, following a suggestion by Dr. G. S. Hume and the late Dr. H. V. Ellsworth, Geological Survey of Canada, has also been used for a peculiarly rich platiniferous uranium oxide ore from the Nicholson property, Lake Athakaska, Sask. More recently, the method has been .tested for the determination also of iridium and ruthenium and results indicate it may be applied, as• well to osmium."

Jan 1, 1953

By P. J. Baguley

The model has been developed on the basis of the observation that the partitioning behaviour of a particle is related to its calculated terminal velocity. It utilises a theoretical calculation of the terminal velocity of each particle class. This is then correlated with the observed partition data for a plant separator using empirically-derived functions of operating conditions which take into account effects such as bath turbulence, holes in drum lifters and feed arrangements. The model successfully decouples the effects of medium density and viscosity and is appropriate for any bath-type separator. The correlation between calculated terminal velocity and actual partitioning behaviour was established and modelled using data obtained from two Wemco drums treating Fe and Mn ores. The model can be used to predict the prevailing size-by-size partition curves and the separation (product grades/recoveries) given the washability of the feed and operating conditions. Simulations are used to show that, for the treatment of Fe ore, there is a maximum medium density beyond which product grades fall and that this maximum decreases as the proportion of magnetite in the medium increases. This is attributed to the dominant effect of viscosity at higher medium solids concentrations

Jun 18, 1905

By Elmer W. Pehrson

NINETEEN FORTY-SIX was an eventful year for the mineral industries. Perhaps the most significant development was the socialization of industry in Great Britain, initiated in 1945 but carried to fruition in the coal industry in 1946. On Jan. 1, 1947, management of the coal industry will be vested in a National Coal Board, responsible to the Ministry of Fuel and Power. A sum of £164,660,000 has been provided to compensate private owners for assets transferred to the Board. The British coal industry has been a problem for many years. Production has declined to a point where serious shortages of fuel for domestic needs have developed. Exports have dwindled to a small fraction of the previous trade. Costs have increased greatly, and quality has deteriorated. The industry's physical plant has not kept pace with the rapidly mounting wage scales in recent years. Some claim that the best and most accessible coal reserves of Britain are heavily depleted. The industry has been harassed by difficult labor problems, including bad morale among the workers and a shrinking labor force.

Jan 1, 1947

The dynamic response of holdup in a continuous ball mill has a direct influence on the rate function of grinding kinetics and is useful for predicting the variation in the size distribution of the finished product with time.A model was proposed involving three interacting, completely mixed chambers and this was used to derive analytically the transfer function of the system, from which the unit impulse response and the unit step response of the holdup with feed rate were obtained.The theory was confirmed by comparing it with previously published experimental data for the residence time distribution of particles passing through a ball mill.

Jan 1, 1975

By D David

Amongst those whose task it is to design tumbling mills and other comminution machines there is an almost religious divide between devotees of the Bond method and devotees of other methods developed in more recent times. For a decade or so the issue was between the Bond power-based methods and the JKMRC (JK) simulation based approach. The newest method to challenge the status quo is power-based and was developed by Steve Morrell. As the title suggests, this paper will take some liberty at concluding that Fred Bond and Steve Morrell may be separated by history, but not by their approaches to their individual contributions to the science of comminution. Another driver for the paper is that although it is good to have diversity of thought, the existing divisions are problematic for those of us signing public disclosure documents. If alternative design methods produce materially different outcomes for the mill duty, then at least one of them is wrong or being used incorrectly. At some point the unsustainable argument may need to be put in a court of law that we metallurgists have two or more materially different design methods, each of which is correct! Therefore, perhaps a resolution is needed before this occurs?The works of both Fred Bond and Steve Morrell are each directly related to their contemporary grinding mill design and operational environments. Both their approaches are empirical, borne of observing and measuring real world situations. Both worked with theories that preceded them, gathered their own data and then each saw shortfalls in the status quo.Fred Bond was an escapee from revolution, a victim of The Great Depression, and had several near death experiences during his early site-based career. Perhaps he was fortuitously rescued from himself when asked by Allis Chalmers (A-C) to set up its rock testing laboratory in Milwaukie in 1930. Fred’s testing led him to conclude that neither the Kick nor the Von Rittinger theories explained his measurements. His writings on the failings of these old theories caused a divide between devotees of the old and new methods at that time. After many years, and much thought and plotting of data (the old way!), he came up with his now-famous equations (and his Third Theory) which have stood the test of time, certainly in the world of Bond-era machines.Coming from England via several African diamond mines, Steve Morrell immersed himself into the comminution world of the JK in Brisbane about a decade after Fred passed on. The JK had developed its semi-autogenous grinding (SAG) simulation framework using its own pendulum breakage tester, itself a derivative of the twin pendulum impact device invented by Bond decades earlier. At the JK Steve developed his authoritative Tumbling Mill Power equations and was involved in real world analysis of comminution problems on the global stage. Steve’s JK experience coincided with the demise of the rod mill, the rise of autogenous grinding (AG) and SAG milling and a rapid expansion in concentrator capacity.Morrell left the JK to pursue his own interests, which included ongoing consulting work, now demanded by the comminution world. He then turned to investigating a growing list of discrepancies between the opinions of designers and theoreticians, and the factual outcomes. The Morrell Method of design arose from this re-examination of ore testing, real world operating data and these glaring and expensive discrepancies between design and outcome. The elements necessary for a relook at the world of rock breakage were in place!CITATION:David, D, 2017. Steve and Fred would have been mates – a comminution design evolution story, in Proceedings MetPlant 2017, pp 2–11 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 11, 2017

By J. D. Noll, S. E. Mischler

Measurement and sampling of diesel particulate matter in mine air presents a challenge due to the complexity of the diesel aerosol. The results of a series of tests carried out by the National Institute for Occupation Safety and Health, Pittsburgh Research Laboratory, in an underground mine were used to evaluate several measurement methods that are currently used to characterize particulate matter emitted by diesel-powered equipment. This paper presents an overview of these techniques and examples of the results along with a discussion of the advantages and information gained by each technique. The measurement methods discussed include particle size measurements using a scanning mobility particle sizer, total particulate matter measurements using a tapered elemental oscillating microbalance, a size selective sampling method for workplace and personal exposure assessment and a size-selective high volume sampling method for carbon analysis.

By Ronald T. Mayerle

In-1992, the U.S. Bureau of Mines conducted a mineral investigation of the Anderson Mountain study area, including RARE II area 4-942, in Lemhi County, Idaho. The 7,340-ha study area lies within the Salmon National Forest about one kilometer north of the old mining town of Gibbonsville (pop.: 100). The eastern boundary of the study area is formed by the crest of the Bitterroot Range. The crest also serves as the continental Divide, and as the border between Idaho and Montana. The study area lies within the Gibbonsville Mining District, an important past producer of gold from lode and placer deposits. Since the 1870's, several hundred claims for both types have been located in the study area. Thirty-six current (1992) lode claims and two patented claim groups (one lode and one placer) are wholly or partially in the study area. No placer claims are current. In all, twenty-seven lode and five placer properties in and adjacent to the study area were investigated. Workings on the properties included 2 caved shafts; 36 caved adits; 8 open adits; 120 small pits, cuts, and trenches; and 4 large dozed cuts.

Jan 1, 1993

By A. M. Hefny, F. P. Siew, P. G. Ranjith

Fracture initiation and propagation, being one of the most intensive subjects in rock mechanics; contribute significantly to the deformation of jointed rock masses. An experimental study on fractured granitic rock was carried out to determine the peak strength of specimen under triaxial loading conditions. The commonly observed failure mode for rock specimens in this study was found to be the shearing of the plane of weakness. The minimum peak strength of fractured rock is observed when the joint orientation is approximately 70° to the horizontal axis. Based on experimental test data, an empirical expression was developed to accommodate the effect of joint orientation and joint trace length in estimating the peak strength of fractured rocks. The predicted values of peak strength using the proposed equation well agree with the experimental results carried out on singly fractured specimens under triaxial loading conditions. The threshold stress values of crack initiation and propagation depend on joint geometrical parameters, their degree of interconnectivity, as well as surrounding stresses on the fracture plane.

Jan 1, 2003