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By R H. Sibson

Magmatic and/or hydrothermal fluid systems in island or mountain arcs self-organise to critical states subject to perturbation by changes in the regional stress, which plays a controlling role in the containment of overpressured fluids. Whether the magmatic arc is under compression (eg Andes, northern Honshu) or extension (eg Taupo Volcanic Zone, New Zealand) is a key factor controlling the ease of magmatic or hydrothermal fluid ascent. Abrupt changes in the stress regime have the potential to induce major episodes of fluid redistribution. Large earthquake ruptures along plate boundaries may induce such changes over broad areas, also contributing to fluid redistribution by renewing fault permeability along the causative rupture zone or reactivating distant fault-fracture permeability by shaking from radiated waves. High-resolution geophysical investigations of active arc systems and the subduction thrust interface underlying their fore-arcs reveal repositories of overpressured hydrothermal fluids. In active magmatic arcs under compression such as NE Honshu or Cascadia, there is evidence for a heterogeneous distribution of overpressured hydrothermal fluids in the middle-to-lower crust trapped around the base of the upper crustal seismogenic zone. Investigations of the subduction thrust interface responsible for great (Mw = 8.0) ‘megathrust’ earthquake ruptures has revealed in some instances (Cascadia, SW Japan) the existence of a belt of non-volcanic tremor (NVT) with accompanying slow slip episodes defining the base of the megathrust interface at 40 ± 5 km and 350°C??-??550°C. Aqueous fluid at these depths is likely derived from dehydration reactions accompanying the basalt-eclogite transition in subducted oceanic crust. NVT sequences in the hanging-wall above the interface may be defining migration pathways into the overlying crust.The potential for eruptive episodes in magmatic arcs and redistribution of hydrothermal fluids is assessed in the light of the stress changes that followed the 2011 Mw9.0 Tohoku subduction thrust rupture which extended along strike for over 500 km and down-dip for over 150 km, with maximum slip of c 50 m.

Aug 22, 2011

By Jamal Rostami, Tala Tahernia

TBM utilization rate is a component of machine performance prediction and critical for developing a reliable estimate of the construction completion time and cost of the tunnel. Estimation of the utilization rate involves identifying and quantifying the time dedicated to each activity in a tunneling jobsite. Ring building is a common activity in TBM tunneling and takes a large amount of tunnel excavation time when using shielded TBMs. This paper concentrates on the effect of tunnel diameter on the duration of downtimes related to ring building and examines the impact of machine diameter on downtimes. For this purpose, the dependency of segment installation time to segment configuration, and also the diameter of the tunnel was investigated. Furthermore, the ring building time for four tunnels with different sizes of diameters and a variety of ring arrangement were analyzed and the relationship between TBM diameter and segment installation time and consequently TBM utilization was evaluated.

Jun 13, 2021

By N. T. Cowper

Slurry viscosity ultimately affects the majority of mineral extraction processes. However, to date its role has been disguised because mineral processing equipment has been conservatively designed to operate at minimal slurry viscosity. With most ores this still meant acceptable solids concentration was achieved. However, with the advent of treatment of weathered ores the resulting higher slurry viscosity (rheology) has meant solids concentration has had to be reduced, often to unacceptable levels. To permit operation at higher solids concentration chemical dispersants are employed. These dispersants are expensive and their addition should be controlled. Slurry Systems Pty Limited (SSPL) has developed an On-Line Viscometer to monitor and control slurry viscosity, whether by controlling water addition or by controlling dispersant addition. Using this instrument the slurry rheology can be controlled at the optimum level, maximizing solids throughput, and minimizing water, reagent, and dispersant addition. This paper discusses rheology of typical mineral slurries, the relationship between slurry rheology and percent solids in a slurry, and the need for rheological control in mineral processing. The effects of rheology on various process steps, and the use of dispersants are reviewed. The paper concludes with summarizing actual case histories and cost impact of Theological control.

Jan 1, 1992

By N. Hwang

There has been increasing interest in the use of robotic machines, and several prototype robotic machines have been developed to automate the grit-blasting process for the purpose of steel bridge maintenance. To utilize such a robotic grit-blast machine effectively, the first consideration is automating the determination of the rust surface area to blast, on the basis of standards of practice, in a rapid manner. This study aims to propose a method to rapidly and accurately determine the rust surface area on steel bridges to blast, with consideration for the standards of practice, from images acquired via a blasting machine. The first step is to perform a color space conversion to transform the input image from a red/green/blue (RGB) color space to a hue/saturation/intensity (HSI) color space. The next step is to detect the presence of rust, using pixel-level classification via the C4.5 decision tree algorithm. Then it is necessary to confirm the blasting area by verifying whether the rust detection result satisfies the specified criteria on the basis of standards of practice. The proposed method was validated on 39 test images with various characteristics with respect to the degree of rusting and rust distribution type. The experimental results showed that the average accuracy rate of rust area classification was about 97.63%, and the success rate of the final decision of blasting area determination was 100.00% for 39 test examples. The whole processing time took an average of only 0.86 seconds per image. The preliminary results demonstrated that the proposed method not only determined whether rust was present in an image and the amount of rust but also indicated whether blasting was necessary, and, if necessary, it rapidly specified the rust surface area that should be blasted on the basis of standards of practice. The proposed method could be successfully incorporated into a robotic grit-blast machine.

Aug 1, 2013

By T. Krumins, F. C. Ruff, M. Eichhorn, L. Zunti

Hatch Ltd. has recently completed a project to increase refractory gold ore processing capacity at Newmont Mining Corporation’s Twin Creeks facility. The objective of the project was to increase throughput by approximately 10% by adding a third autoclave feed pump to each of the two autoclave circuits. To minimize project capital cost, autoclave feed pumps from Newmont’s decommissioned Lone Tree facility were evaluated and found to be suitable for this new service. The existing pressure oxidation circuit was reviewed in a debottlenecking study to determine other upgrades required to facilitate the increased throughput. Interruption to operations was minimized with a detailed construction plan, supplemented with detailed 3D layout model sequencing studies. The focus of this paper is project development, multi-discipline design considerations, and implementation results.

Jan 1, 2014

THE members arrived at Ticonderoga, N. Y., at noon, Tuesday, October 15th, and were received by Mr. Cyrus Butler, Chairman of the Local Committee of Arrangements. During the afternoon the works of the American Graphite Company and the Horicon Iron Company were visited under the guidance of Mr. Butler, President of both companies, and of Mr. William Hooper, Superintendent. An excursion was then made, in carriages, to old Fort Ticonderoga, on Lake Champlain, after which the party were driven to the Rogers Rock Hotel, on Lake George. The first session of the Institute was held in the parlor of time hotel on Tuesday evening. Mr. Eckley B. Coxe, President of the Institute, opened the proceedings with the following address: I shall ask your attention, this evening, to a few reflections upon the subject of mining engineering as a profession in the United States, its past, its present, and its future, and its duties and oppor¬tunities with reference to the proper development of our great min¬eral resources. Thirty years ago, there were scarcely any mining engineers in this country, and but few in England, and there were no institutions where young men could be educated for the profession in the Eng¬lish language. France and Germany have been able for about a century to boast of mining schools of a high character, that number among their graduates such men as Humboldt, Weisbach, Rittinger, Combes, and Gruner. Of the few we then had worthy of the name of "mining engi¬neer," some had studied in the continental academies, and others were graduates in the school of practical experience, and had learned their profession in mines and smelting-works. Their work con¬sisted principally in making surveys and maps of mines and mining properties, geological reports, and analyses of ores ; but the mining engineer whom we often meet with now, who has studied chemistry, physics, mineralogy, geology, mechanics, and drawing; who is more or less familiar with machinery and its construction, and with the practical management of mines or smelting-works, and who is an expert in some one branch of his profession, would have been very difficult if not impossible to find in the United States. The induce¬ments held out to ambitious and talented young men to enter the

Jan 1, 1879

By S. J. Gasior

A method for destroying the caking properties of bituminous coal was developed by the Bureau of Mines. Coal is treated in a fixed bed by heating through its plastic range under controlled temperatures in mildly oxidative atmospheres composed of inert gas and/or steam containing about 1 volume-percent oxygen. High-volatile A (hvab) and high-volatile B (hvbb) and low-volatile bituminous (lvb) coals in the size range 1/8 to 1-1/2 inches were successfully treated at 0 (atmospheric pressure) to 300 psig in static beds 6 to 18 inches deep. Conditions of treatment depended on the coal and ranged from 80 to 200 minutes at 350° to 510° C. Char produced in this manner from hvab coal was gasified with steam at 800° C and 100 psig in a fixed bed in one series of tests and in other tests was exposed to hydrogen in a dilute co current free-falling-bed system at 750° C and 3,000 psig without agglomerating.

Jan 1, 1965

By R. H. Eric, A. Chaendera

Gas jet was blown through bottom nozzles of a 1/5th scale CLU model in the presence and absence of slag. Kerosene and water were used to simulate the slag and metal phases respectively. Mixing time increased with increasing bath height and with a decrease in the gas flow rate. It was related to bath weight, bath height and gas flow rate. Slag increased mixing time by about 16% and the mass transfer values by about 32%. Mass transfer rates were higher near the bath surface and in the gas-liquid plume region. They increased with increasing gas flow rate and with a decrease in bath height. A relationship showing the dependence of derived mass transfer coef ficient on the gas injection rate was established. Turbulence characteristics inside the bath liquid were established to vary with location, vessel geometry and gas injection rate.

Mar 1, 2017

MIM Holdings Limited has acquired a reputation for the successful application of R&D to develop break-through technologies for the mining industry. The Isa Process tank-house technology has been licensed to copper refineries throughout the world, and almost 40 per cent of the worldÆs copper is refined using this technology. Isasmelt copper and lead smelting technology is either in use, or is currently being installed, by eight companies in eight countries around the world. Jameson Cell technology is widely used in the coal mining industry and increasingly in the base-metal industry. The IsaMills developed at Mount Isa and McArthur River made it possible to develop the McArthur River and George Fisher orebodies. This paper will address the need for innovation and then discuss the development of the IsaMill and Isasmelt technologies. It will conclude with some comments about why MIM has been so successful in developing such technologies.

Jan 1, 2002

By J. V. W. REYNDERS

IN THE remarks which I am about to make concern¬ing the safety work of the Bureau of Mines, I want first of all to disengage myself from a disposition, which is frequently in evidence, to give spectacular emphasis to the hazards of mining operations. It is of the' utmost importance to the industrial welfare of our country that the enormous annual requirement of fuel be produced and be made available in our economic activities, with a minimum of distress and hardship. The safety of coal mining is a condition with which. we are all concerned in a fundamental way. And yet we should not rush to accept hastily conceived notions that laxity among employers in respect to safety measures exists to any outstanding degree. In fact in a large number of instances, the precautionary efforts of min¬ing companies, directed to the elimination of accidents are beyond all criticism, albeit the industry suffers in reputation from the carelessness of, its less effi¬cient constituents. The Bureau of Mines has been a leading influence in disseminating the doctrines of safety, in securing the cooperation of the miners themselves, and in stirring up ' the laggards, both among the employers and the employed. It is much to the interest of well-conducted mine operations that the industry, as a whole, observe safety regulations to the utmost.

Jan 1, 1925

By Richard H. Sibson

Changes in seismic style along the San Andreas fault system appear to correlate with strike-parallel variations in regional heat flow. Large earthquake ruptures are associated with colder segments of the fault zone, while comparatively high levels of microearthquake activity and small to moderate shocks occur along the hotter segments, often in association with aseismic creep. Such behavior is consistent with geotherm and strain rate dependent profiles of shear resistance versus depth, constructed for quartz-bearing rocks. These profiles suggest that the transition from frictional to quasi-plastic behavior with depth should increase by a few kilometers passing from the hotter to the colder portions of the fault zone, giving rise to long-wavelength concentrations of distortional strain energy near the base of the seismogenic zone in the cold segments. Some support for this hypothesis comes from the observed deepening of microseismic activity passing northwest and southeast from the central Californian active region to the currently locked, ~400 Ian segments of the San Andreas fault that ruptured in 1906 and 1857.

Jan 1, 1982

By J. P. Morris

The Bureau of Mines investigated the mechanics of fuming of iron-carbon melts during top-blowing with oxygen. Melts weighing 45 lb were prepared in an induction furnace and blown with oxygen by means of water-cooled lances. The rate of fuming was measured and correlated with the operating variables. The data showed that the primary cause of fuming was a boil at the bath surface in the impingement zone of the oxygen jet. Nucleation of the carbon monoxide bubbles producing the boil was apparently brought about by the precipitation of an oxide phase. The actual fuming mechanism involved partial oxidation and vaporization of bubble films and fine metal spray generated by the bursting of the bubbles. Bubbles that formed outside the impingement zone produced little fume. The distribution of trace elements between the metal and fume strongly indicated that the fume contained fine spray particles as well as particles that had condensed from vapor. The rate of fuming was found to be proportional to the carbon content of the metal) the concentration of oxygen in the jet) and the bath temperature) provided that a continuous boil occurred. In the absence of a boil) very little fume was produced.

Jan 1, 1967

By Richard I. Barnhisel

At the Sinclair Study Site it was found that the deeper the soil the greater the yield of corn, soybeans, wheat, alfalfa, and timothy. Yields at this location were generally lower than those at the Alston Surface Mine. At Alston the non-prime land treatments generally produced greater yields for all crops than did the prime farmland treatments, however, the intermediate soil thickness, 20 cm topsoil over 40 cm of subsoil, gave the best yields, provided it's subsoil had been limed. From a chemical point of view, acidic spoils do not need to be buried by 120 cm or 4 feet of soil, provided adequate lime is applied to these spoils as a barrier prior to placement of good quality topsoil and only forage crops are to be grown. The burial depth must be increased to as much as 75 cm when grain crops such as corn or soybeans are to be grown. This response to burial depth appears to be related to water storage needed by the crop and not due to toxic effects of the spoils. A conventional farm tractor-mounted subsoiler increased yields of soybeans and corn the first one or two years, but the effect was diminished with time. Subsoiling did not produce significant increases for alfalfa or wheat. However, ripping with a bulldozer produced significant yield responses, especially for corn and soybeans, that have lasted for at least three years. The ripping effectively reduced the bulk density at least within the zones through which the ripper had passed. Liming the upper 20 cm of subsoil significantly increased yields of alfalfa, corn, and soybeans. There also appeared to be an interaction between this lime treatment and soil depth. Yields of some grain and forage crops may be high enough to meet target levels for bond release for prime farmland. Based on the present study, one should not expect corn yields to be high enough to meet bond release. This statement should not be considered final since the experiment is not complete.

Jan 1, 1983

By Timothy Batchler

"Standing roof supports help to provide a stable working environment in coal mine gateroads. NIOSH participates in the development of these support systems by conducting full-scale tests in their Mine Roof Simulator. These tests have established the performance characteristics of every coal mine support system currently in use in the United States. Through these tests, mine operators and regulatory officials have acquired a fundamental understanding of the various types of support performance that guides the assessment and use of these support systems. However, some little known factors that influence support behavior can lead to misconceptions and, perhaps, a poor assessment of support behavior at times. This paper highlights several of these factors and discusses their significance. The paper also examines a current longwall tailgate support and discusses the inefficiency with this approach. Finally, the NIOSH Mine Roof Simulator (MRS) is the world’s most powerful load frame built specifically to test full-scale roof supports, including longwall shields. are addressed in this paper to provide a more in-depth assessment of the limitations of the MRS and what the MRS testing protocol is designed to do. INTRODUCTION Over the years, considerable research has been conducted to develop standing support technologies and to evaluate their performance characteristics. The load and displacement characteristics of the standing supports have been determined from full-scale testing conducted using the National Institute for Occupational Safety and Health (NIOSH) Mine Roof Simulator (MRS) (Barczak and Tadolini, 2008) located in Bruceton, PA. Performance traits, installation patterns, and ground responses are observed in various geological and mining conditions and are evaluated to determine the support performance in the field (Dolinar, 2010; Campoli, 2015; Zhang et al., 2012). Despite widespread use of standing supports, not every aspect of their performance and resulting ground support capability are always well understood. This paper discusses 10 factors, several of which are surprising, that impact standing support performance."

Jan 1, 2017

By Oliver Bowles

TO keep pace with technical progress is an important function of any industry. All branches of mining may learn important lessons by observing progress made in other branches. The non-metallic mineral industries may learn much from each other as well as from the metal miner and the metallurgist. Recent technical advances which have come to the attention of the Committee on Non-metallic Minerals are presented herewith for consideration and comment. It is planned to present this review for open discussion at the February, 1931, meeting of the Institute. Comments will be welcomed either in the form of written or oral discussion. It is desired that new developments not covered in this paper be brought up at that time. Some notable advances have been made in cement technology. Recognition is now being given to the advantages of closed-circuit grinding of cement raw materials in wet-process plants, with stage removal of the fine materials, It increases mill capacity, reduces the wear of grinding media, and also reduces the power requirement. The method is well known in metallurgical plants, and its acceptance by cement companies is another illustration of the lessons the non-metallic industries may learn from the metal industries. Closed-circuit dry grinding has also proved advantageous for both raw materials and clinker.

Jan 1, 1931

By H. G. Lucas

A feeder screw supplied at constant pressure by a hopper-orifice arrangement was developed for feeding solids in size ranges up to several hundred micrometers at constant flow rates. Performance of the feeder was evaluated by measuring the flow rates obtained with 3-to 7-micrometer coal ash, 70 percent through 200-mesh coal, and minus 325-plus 400-mesh coal ash. Constant feed rates within a few percent of set values were achieved for half-hour periods for the larger particles and for 5-minute periods for the finer particles. Suggestions are given for feedstock preparation and feeder operation for optimum performance.

Jan 1, 1974

By L. Martins Demuner, D. Burzic, V. Cunha Aranda, F. L. Lourenço, G. Romeu Trindade dos Santos, F. Ramstorfer

For many years, Dynamic Soft Reduction has been regarded as a proper method in improving internal quality of slabs. Even though processes models improved significantly over the past years, the efficiency of Soft Reduction was always limited by the discretization error, which inherently exists if segment rollers cannot be positioned individually. The recently developed SRD segment type allows for an individual roller positioning within the mushy zone by avoiding any discretization deviation from the optimal gap. This paper provides a detailed technological overview of the SRD segments as well as operational results at their very first implementation at Ternium Brazil.

Oct 1, 2019

By Ira Joralemon

THE Ajo copper district is in the heart of the Arizona desert, near the western boundary of Pima county. Gila Bend, the nearest railroad point, is 43 miles north of the camp, and the little Mexican border town of Sonoita is 30 miles south. Between Gila Bend and Sonoita, Ajo is the only settlement save for one or two small cattle ranches and the uncertain villages of nomadic Papago families. The Little Ajo mountains rise a few hundred feet above wide desert valleys, beyond which are lava mesas. The camp itself lies at an elevation of about 1,900 ft. above sea level, in a little basin on the east side of the range, separated from the open desert by low hills. In the center of the basin the brilliantly iron and copper stained rocks of Copper mountain rise 150 ft. above -the village. Many varieties of cactus and low desert bushes cover the hills, while in the large valleys there are clusters of mesquite paloverde, and ironwood trees which furnish limited amounts of fairly good fuel. A scanty supply of water is obtained from wells in the desert and from prospect pits in the camp. The nearest abundant source of water is the Gila river, 50 miles north of Ajo. (See Fig. 1.) HISTORY OF THE AJO DISTRICT The Ajo, next to Santa Rita, New Mexico, is claimed to have been the first copper district in the Southwest worked by Americans. In the '60's or even earlier high-grade native copper and cuprite Ore was mined from shallow surface workings and hauled by bull team 400 miles across the desert to San Diego. From there it was carried in sailing ships to Swansea, Wales. Later, the ore was hauled to Yuma, floated down the Colorado river to the Gulf Of California, and shipped to Swansea. Bat-infested old workings and the massive axles of the bull carts are shown to prove the truth of the stories.

Jan 8, 1914

By Knud Sinding

Mining firms are widely criticised for their adverse impacts on the environment. At the same time many firms in the industry devote extensive resources, both financial and managerial, to the reduction or elimination such impacts. Very considerable improvements have been made, although these are sometimes overshadowed by a few high-profile accidents, such as the occasional collapse of a cyanide-containing tailings dam. In parallel, much effort is also directed at projecting a positive environmental image, as witnessed by extensive environmental reporting, both on paper and increasingly through web-platforms. Mining projects today almost invariably involve some form of environmental protection. In industrial countries regulations in this area are extremely stringent, as is enforcement. In less well developed countries, regulation and enforcement may be weaker, but firms are in many cases and for a number of reasons committing themselves to high levels of environmental protection, even if they might get away without doing so. Research in the area of environmental performance of mining firms has so far paid much attention to concepts such as sustainability indicators and the sustainability of individual firms. Given the still raging debates about the appropriate way to determine the degree to which any given firm is sustainable (Welford 1995) as well as the usefulness of what will in the final analysis be a value judgement, anyone on the sidelines of the debate will come back to the fundamental issue, how is knowledge that a particular firm has been judged ?sustainable? going to be made use of. This issue remains unresolved, which may explain the lack of progress in formulating a useful definition of a sustainable firm The question addressed in this paper is not so much about what firms are doing on the ground or in any particular case of environmental protection, but more in the subsequent use of these efforts - and by extension - on the overall direction of corporate environmental strategy. The fundamental problem facing all mining firms is that they cannot easily benefit from unilaterally reducing their environmental impact. The firm can of course avoid liability and keep a variety of stakeholders happy and hence experience lower costs of obtaining the [input] resources they need (in a broad sense, not just minerals), but this represents only part of the opportunities available form pursuing an environmental strategy (Reinhardt 2000). The other part, which may have an enormous potential, involves the concepts of competitor management and product differentiation. The logic of keeping stakeholders happy has been most forcefully argued by Pfeffer and Salanchick (1978) who link the behaviour of firms in all domains to their ability to obtain the resources they need, at a cost that is lower than it would otherwise be (Pfeffer & Salanccik 1978). Several varieties of strategy can be included under this heading, including cost reduction and risk management. The alternative logic is to convince customers that they want to pay more for minerals supplied by mining firm X or directly attributable to mine Y, or by making all mineral users pay more. These two strategies, which may be referred to as product differentiation and competitor management, respectively (Reinhardt 2000) are related to the demand side of mineral supply, whereas cost reduction and risk management are related to the supply side. Mining firms have not pursued the demand side very much, if at all. This is probably due to the extreme difficulty of moving mineral products, bulky and unglamorous as they are, away from their

May 1, 2003

By W. A. Grosh

Records show that much of the lead produced in the Upper Mississippi Valley lead-zinc field was taken from natural openings along crevice systems at shallow horizons or at the surface. During the early history of the district, the shallow deposits were worked intensively; but in recent years the production of lead, except as a byproduct of deeper mining for zinc ores, has not been significant. Considering the methods of early mining, the character of mineralization, and the fact that galena can still be found on the surface of the old digging areas, it was reasoned that enough mineralization might remain on and above bedrock to permit, through the use of modern equipment and methods, economical re-treatment of surface material in the digging areas.

Jan 1, 1960