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By C. J. Hall

An investigation of multi-shaft airflow problems by the author in 1976 (1) was presented in the hope of arousing considerable written comment, but in fact-. only one contribution (2) was forthcoming. The investigation in this paper is taken several stages fur¬ther, because the matter is of major importance in many American hard rock mines with complex networks extending over thousands of meters vertically. The examples used have all been generated thermodynamical¬ly and checked by motive column (denisty) calculations. Dry air has been used to reduce the amount of time spent on the rather complex calculations, but it has been shown (3) that the principals developed apply equally well to air/vapor/water mixtures. Initially the subject is investigated using both thermodynamic and motive column analyses. The latter part of the paper concentrates on a motive column presentation. Both methods are, of course, equally valid and give identical answers to any situation when correctly applied, as is shown in the worked examples.

Jan 1, 1980

By R. Q. Honaker, D. Tao, D. Taulbee, B. K. Parekh

A significant amount of energy exists in the waste generated by the coal and timber industries. In the coal industry, the energy loss is mainly due to the discharge of fine coal to the waste impoundment. Despite the fact that the fine coal has the greatest cleaning potential, dewatering, handling and transportation concerns prevent its use as product in many cases. Likewise, the sawdust generated from wood production has energy value and is used as industrial boiler fuel when the transportation distance is relative short. However, wood waste is often discarded into cumbersome landfills due to uneconomical transportation alternatives. Recent research found that these two waste materials can be combined to provide a high energy fuel of around 13000 btu/lb that can be easily handled and transported to end users.

Jan 1, 2004

Overland conveyor belts that exhibit tracking problems under loaded and unloaded conditions can be tested to' determine the root cause of the mistracking. Moveable conveyors are more prone to mistracking due to structure alignment requirements. In addition, belting quality, splice straightness and carcass condition has a dramatic effect on the performance of a belt in relation to tracking. Methods are discussed that are proven to reduce belt mistracking and improve the operational reliability of the conveyor system.

Jan 1, 1995

By James K. Ballard

Leach dumps in Butte are relatively new in comparison with older established dumps in other areas throughout the West. With the exception of one 10 million ton dump, all dumps have been formed on a prepared base. This is necessary because the entire leach dump area overlies an alluvial fill which varies in depth from 100 to 400 feet and through which solution would be lost. Preparation of the leach pad consists of first removing all vegetative material and compacting the exposed surface with rollers. This surface is covered with a 4" layer of minus 1" crushed rock which in turn is roller compacted. A 3" compacted layer of asphalt hot mix is then applied to the crushed rock surface. Final sealing is effected by a 1/4'? coating of catalytically applied hot asphalt. Dump leaching was inaugurated in 1964. First solution applied was wholly made up of mine water pumped to surface through a central pump shaft. Sulfuric acid was added on surface at a surge pond to control pH of the leach solution. Acid addition is necessary not only to benefit the leach dumps, but to prevent the formation of ocher scale within the pipe line distribution system. Mine water pH is on the order of 2.8. The combination of ferrous and ferric iron as well as magnesium and aluminum salts is such that ocher forms at a pH of 2.38. It is therefore mandatory to control pH at 2.0. Dump effluent pH is held at 2.3 or less.

Jan 1, 1968

By George S. Austin

Adobe, dried mud bricks, have been used since before historic time in the construction of dwellings. Building materials are normally evaluated for thermal performance based on measurements known as R- and U-values. The R-value is an indicator of the ability of a wall to insulate effectively and the higher the R-value, the better it is as an insulating material. The U-value, or value of conductance, is the reciprocal of the R-value and reflects the rate at which heat is conducted through a material. But the "heat capacity of the wall" must also be considered. This measures the length of time that passes before a steady state of heat flow is achieved. The effective U-value measures both the resistance to the transfer of heat and the capacity to hold heat. These latter value make adobe a far more interesting as a modern building material that was formerly recognized.

Jan 1, 1983

By John D. Katsllometes

In the mining and processing industry, the maintenance plan has often evolved rather than being consciously set up resulting in an overreliance on breakdown and fixed-time maintenance (planned maintenance). Historically mining and processing plant equipment has been robust and less automated than modem equipment, making it relatively easy to work on. Mining and processing plants have relied on large and expensive maintenance departments to enable rapid attention to breakdowns. Maintenance itself can result in excessive downtime and costs. This results from the requirement to take the machinery off-line to carry out (possibly unnecessary and invasive) maintenance. The danger of infant mortality after it has been put back on line again and also the cost of the maintenance action itself contributes to costs. A goal of any well-run maintenance program is to have the lowest cost while providing 100% capacity 100% of the time to operations. When maintenance investments are at a minimum, the cost of lost production is at its highest. As maintenance effort and investments are intelligently increased, the production loss gradually decreases until the lowest combined cost is achieved. This is the maintenance goal. A road map is needed to achieving maintenance excellence. This article addresses a "Road Map" to achieving maintenance excellence. INTRODUCTION Mining and processing industry maintenance is big business. A world-class maintenance program is characterized by maintenance excellence.

Jan 1, 2004

By Paul Mitchell, Clive Potter, Miles Watkins

Meldon Quarry is a seemingly rare occurrence of acid rock drainage (ARD) in a quarrying operation.4 With surface waters discharging to a tributary of a salmon-bearing river, it is subject to stringent discharge conditions. The quarry predates effective environmental management, and preventative, control and treatment measures were not implemented until relatively recently. However, retrospectively implementing standard preventative approaches at the site is costly, technically difficult and of uncertain benefit. This paper overviews the recent site history and introduces data from a demonstration by KEECO (UK) Limited of its Silica Micro Encapsulation (SME) water treatment technology.

Jan 1, 2000

By R. L. Merrifield

Cominco Snip is a 60: 40 joint venture of Cominco Ltd. and Prime Resources Group Inc. Cominco manages the operation. The mine site is located in a narrow mountain valley where Bronson Creek enters the Iskut River in Northwestern British Columbia. Access is by air only to the company's 1,500 meter airstrip. Milling at a designed feed rate of 300 tpd began on schedule in January 1991. Tonnage and gold production in the form of bullion bars from the gravity circuit and gold bearing float concentrate have exceeded design forecast. This presentation will examine many of the factors that influenced the final plant design inclusive of exploration findings, bench scale and pilot plant test results, environmental and social considerations, capital and projected operating costs and product transportation alternatives such as the operation's Hovercraft.

Jan 1, 1993

By D. L. Monroe

Technical service is assuming an increasingly important role in the sale of asbestos fibre,, Manufacturers are examining raw materials more closely than ever before in order to, obtain the most efficient usage in their processes. Asbestos is one of the more difficult materials to evaluate and consequently has been are of the last to be subjected to evaluation. The main problem encountered in the evaluation of asbestos fibre is that minor differences in grade and texture are not shown up by chemical analysis, and are identified only by specialized physical analyses or actual production use. However, such minor differences become more critical as manufacturing processes are made more efficient, and many purchasing agents and plant chemists are applying a closer scrutiny to their supply of raw asbestos fibre. Many processes have been formulated around grades and qualities of asbestos fibre, which were standard some time ago, but which may now be subject to modification and improvement.

Jan 1, 1959

By John G. Hall

Everyone forms his own mental picture when the subject of copper is mentioned. To an architect, copper is a warm, enduring metal with a quiet beauty; to the historian, man's first metal; to the product engineer, the best electrical and thermal conductor of all commercial metals; to the investor, a volatile stock; to the speculator, the daily price quotation; to those in the mining industry, the challenge of producing copper for rising needs in the face of rising costs and lower grades of ore. At this meeting, we will look upon copper as a key raw material in industry, in national defense, in technology, in world trade, and as a principal commodity in the economies of several developing countries. As miners, and most of us here are miners, we are prone to view our role as suppliers of copper. We locate, mine, smelt and refine the metal. In the complexities of today's world, however, following a period of the longest domestic copper strike in history which caused critical world-wide shortages and widely fluctuating prices; it becomes necessary for all of us to concern ourselves with the whole spectrum of copper affairs -"from mine to consumer " But first we need to look at the miner's side of the picture -- capacity and production. We will examine these functions in terms of the whole world -- not simply the free world. Nature did not endow all regions of the earth equally, and copper in world trade has a way of ignoring political boundaries. Science and technology, as well, know no national boundaries. It is said that the "Engineering & Mining Journal" has as many readers in the Communist World as in the Free World. Nor is this a one-way street. We presently have available to us in the. U.S., cover-to-cover translations of many Communist World mining and metallurgical journals.

Jan 1, 1968

By Sandy Clamage

"Seeing the elephant" was a term often heard from 1849 to 1859, the period of the great California Gold Rush. The phrase was used by those who dreamed of instant wealth that was believed could be found in California's virgin earth and mighty rivers. When news of fabulous gold strikes throughout the Mother Lode reached far away places, thousands of gold seekers left home and family to join in this incredible adventure. The barren, placid state of California soon became one of the most bustling, populous areas in the West. Before the Rush Before 1848, Mexico ruled California. It was then a remote region, isolated from the urbane world of the East by 2900 km (1800 miles) of scorching desert and impassible mountains. By sea, it was 29 000 km (18,000 miles) via Cape Horn. Spaniards and Mexicans settled the coastal lands on tracts donated to them by the Mexican government. The inland area was the domain of Indians and a few settlers who also had been granted estates by the government. Among those settlers was Captain John Sutter. He had been fortunate enough to obtain about 11 leagues of land (spanning 100 km or 60 miles in length) from Governor Alvarado of Mexico. Sutter was somewhat of a visionary and possessed a gifted tongue. He managed to receive most of what he desired with minimal trouble. Enchanted with Sutter's personality, Alvarado promised him Mexican citizenship. Alvarado also commissioned him to become "representative of the government and officer of justice on the Northern frontier." With uncanny foresight, Sutter began building a fortress on his land in the Sacramento Valley. It later became known as Sutter's Fort. It was more than just a fort, however. It also became a stopping place and home for many foreigners and Americans who traveled to California, and it eventually became the mecca for overland pilgrims. Sutter engaged in many projects. These included a cattle ranch, fur trade and trapping, and the construction of an irrigation system. With the influx of immigrants over the years, the community around the fort grew rapidly. Lumber was much in demand and Captain Sutter agreed to supply the necessary capital for a community sawmill. The site chosen was some 72 km (45 miles) northeast of the fort on the south fork of the American River in the town of Coloma. During the course of its construction, Sutter's carpenter, James Marshall, discovered a problem with the tailrace on the mill. First Strike Early in the morning on Jan. 24, 1848, Marshall was checking the tailrace. He noticed an object shining in a foot of water at the bottom of a ditch. He reached down and picked it up. His heart began to thump wildly as he realized he was holding a gold nugget. Sutter planned to keep the find a secret for as long as possible. He knew very well that he could become an extremely wealthy man. The ever loyal Marshall remained faithful to his employer and the pair did their best to obtain more

Jan 3, 1985

By A. Unal

Barbaro et al. (1990) implemented a tedious study aimed at delineating the short-scale spatial variability of sulfur in a coal seam. It is not possible, however, to extend their conclusions to any other coal seam or use theirs in any other fashion, because the background geology was not presented. Nor were the conclusions accompanied by geological interpretations in the paper. In addition, an unfortunate printing error occurred where the total sulfur (determined by High Temperature Combustion) variogram in Fig.3 was duplicated in Fig. 2 instead of the seam height variogram. A more serious error, however, has been committed in the definition of the variable, seam height. What is defined as seam height by Barbaro et al. (1990) is, in essence, mining height, and is not a regionalized variable that should be studied by geostatistical methods directly. Despite the fact that the variable, seam height, is not defined in the paper explicitly, the following quotation discloses the fallacy: "All roof rock that exceeded 1.8 m (6 ft) from the floor was not taken because the longwall was operated to not mine more than 1.8 m (6 ft) unless the coal seam height exceeded 1.8 m (6 ft)." From this definition, the seam height, and therefore the sampling height, is equal to the actual coal thickness, if the coal thickness is greater than 1.8 m (6 ft). Otherwise, it is equal to the sum of the coal thickness plus the thickness of the roof rock that complements the thickness to 1.8 m (6 ft). In the latter case, the seam height is constant and equal to 1.8 m (6 ft). It is possible to conduct a variogram study on a pool of samples that are realizations of two different variables. But the conclusions derived would not belong to any one of the two variables uniquely and, therefore, do not possess any significance. Geostatistical analysis is irrelevant for the sum of multiple regionalized variables formed by arbitrary selections. In a two¬seam setting, for example, the mining height, as defined by the thickness of one seam at one location and the thickness of both seams at another location (due to quality and/or minimum thickness considerations perhaps), should not be used in the calculation of one common variogram. The two seams should be modeled separately. They can then be combined according to the specific purposes of the study. On the other hand, if a constant is added to a regionalized variable (to incorporate dilution perhaps), the variogram of the new variable will not change. Barbaro et al.( 1990), surprisingly, does not give any geologi¬cal interpretation of their results despite the fact that most of them can be explained by the origins of sulfur in a coal seam. The presentation of the results of a geostatistical study with no reference to the geology of the deposit is uninformative. It may also be misleading for the potential users of geostatistics. It is not unusual to find nuggets of pyrite in coal seams. In such cases, pyritic sulfur will probably display a spatial structure for only a very small distance that will appear in the experimen-

Jan 1, 1991

Due to the relatively remote location of the St. Anthony Mine, the high cost of transportation and milling, plus the low grade nature of the deposit, the United Nuclear Corporation began investigating methods of mechanical upgrading approximately eighteen moths ago. This investigation culminated in the installation of Model 17 and Model 18 ore sorting machines. The machines are marketed in the United States and Canada by Ore Sorters of Canada (Ltd.). The installation of this advanced technology will enable United Nuclear Corporation to fully realize the residual potential of St. Anthony.

Jan 1, 1979

By Alexander N. Winchell

"The iron ores of the Lake Superior region are found almost exclusively in rocks of Huronian age, the only exception of importance being in the Vermilion district. It may be estimated that about 95 per cent of the ores thus far mined have been obtained from Huronian rocks. Although these ores come from rocks of varying age and slightly varying type, they have many features in common, and therefore may readily be described together.The iron formations of the Lake Superior region consist essentially of interbanded layers of mixtures in widely varying proportions of silica and iron oxide, and are called taconite, ferruginous chert, or jaspilite. They vary considerably in hard¬ness and color, depending upon the tenor of silica and the history of the rock. Local phases of the iron bearing formation consist of cherty iron carbonates, greenalite or ferrous silicate, rocks, amphibole-magnetite masses, cherts and slates, and pyritic quartz rocks. The average iron content of all the original phases of the iron bearing formations, excluding interbedded slates, is about 25 per cent, while the average iron content for all portions of the formation, whether in the original condition or not, is about 38 per cent. It is believed that this difference is due essen¬tially to the removal of silica in solution from the. primary phases, and, of course, such removal of silica has in many cases produced material now used as iron ore, since it contains con¬siderably more than 38 per cent of iron."

Jan 1, 1920

By Donald Babbitt

In 1971, during the planning and design stages of a $300 million expansion, the Iron Ore Company of Canada Ltd. through its Engineers, Canadian Bechtel Ltd., came out with a preliminary request for two (2) 10,000 LTPH belt conveyor scale systems. These Systems were to provide weighing accuracies within 2.5% of the iron ore pellets and concentrates in transit on two (2) 72" wide conveyors from the stockpiles to the ships. Each conveyor system would be fed by a rail mounted bucket wheel reclaimer, with the conveyed material moving directly to the ship loaders with no inter- mediate surge and/or storage bins between the stockpiles and the ships. The bucket wheel reclaimer discharge rates would vary from 0-9600 LTPH in cyclic periods, with the periods varying from 1-5 minutes - dependent on the level of the reclaim buckets in relation to the stockpile as well as the slewing rate of the reclaimer. There would be frequent interruptions for bucket wheel repositioning (laterally and vertically), changing ship holds, and trimming ship holds. These frequent zero flow conditions, approximately 500 per 150,000 ton ship, could last 1-5 minutes. In addition, the conveyors on which the scales were to be mounted would be over the water and subject to the wind and cold of Northern Quebec. These Systems would be in use 350 working days of the year and would load 30,000,000 LT/yr. (An average of 90,000/working day).

Jan 1, 1975

By James L. Patton

Automation of mining increases the productivity of labor, thereby reducing the unit cost of labor. Such cost constitutes the largest portion of the direct or variable costs of producing coal. Therefore, any increase in productivity directly reduces variable cost. The large investment in mechanical equipment carries with it the burden of increased fixed charges. As the proportion of fixed cost to the total cost increases, the effects on the cost of production changes are amplified. Therefore, equipment must be fully utilized at all times. Averaged fixed costs rise with any decline in production. Such a situation forces coal companies to seek every means of main¬taining full production. Figure I will reflect the story on the relationship of production to cost.

Jan 1, 1962

By P. Asadollahi, M. Invernizzi

"This paper describes the innovative full-face conventional tunnel excavation technology, with its advantages in terms of savings and safety. The full-face approach has been developed throughout the experiences gained in tunnel construction. The innovative design approach is focused primarily on the deformation response of the ground acting first and foremost ahead of the face, which is analyzed, predicted and controlled by pre-confinement of the core. The advantage of this method is particularly evident in difficult grounds. This paper will present the outstanding benefits given by the adoption of the full-face approach in two projects, the “Sochi” and the “Visnove” tunnels. THEORY AND DESIGN ASPECTS OF THE FULL-FACE EXCAVATION The main challenges in tunnel and underground construction industry are gathering the design data from the ground that is being excavated and foreseeing the critical stage during construction, where the materials are in its most critical configuration. These challenges shall be addressed during excavation when the lining and the excavation disturbance have not yet reach the equilibrium. The in situ stresses in the ground are redistributed (forming an “arch-effect”) around the opening, with zones of increased stresses around the walls of the excavation (Figure 1). The distribution of the stresses can be close or far from the excavation profile, depending upon having a ground capable of withstanding the deviated stresses well or unable to withstand them, respectively. In the latter case, the ground will plasticize and deform in proportion to the volume of ground involved in the plasticization phenomenon. When the ground completely cannot withstand the stresses redistribution, it will cause the collapse of the excavation. While in the first case, the arch effect occurs naturally, in the second case, it does occur naturally only when the ground is stabilized properly. In the case of collapse, the arch-effect must be produced artificially operating on the ground prior excavation. The design should be based on the understanding of if and how the arch-effect can be mobilized during tunnel excavation and ensure that is formed by calibrating excavation and stabilization operations appropriately. The arch-effect is function of the medium that is being excavated, the action taken to excavate and the reaction expected following the excavation."

Jan 1, 2018

By D. Hodouin

The paper reviews approaches to estimate in a real time fashion consistent mass flowrates and assays, using data from the on-stream analyzers and flowmeters of a flotation circuit. Results obtained with one algorithm operating on-line with an industrial flotation circuit are presented.

Jan 1, 1996

By D. E. Ranta, G. H. Giroux, A. W. Randall, D. A. Barr

Zinc-lead ores of the Pine Point District, Northwest Territories, Canada, are hosted in paleokarst cavities within a Middle Devonian carbonate barrier complex. Of the nearly 100 deposits found, most are irregularly distributed along two main regional stratigraphically controlled trends. The ores, which occur predominantly as open space filling, form deposits most of which average one million tonnes in size with an average grade of 10% combined zinc plus lead. Geological features related to karsting control not only distribution of deposits but also their shape, size and grade. The higher grade ore in these deposits generally occurs in a relatively small core area. Consequently, accuracy of reserve estimation is dependent on drill-hole density and understanding of karst geometry. Several case examples will be reviewed to demonstrate the relationship between shape, size and grade of deposit, geological reserves and drill-hole density, along with a discussion of geological ore reserve estimation methods.

Jan 1, 1992

By D. J. Fitzpatrick

The paper reviews current mining subsidence research at The Department of Mining Engineering, University of Notting- ham. Special attention is being devoted to prediction of ground movements between the mining horizon and the surface using physical and computer-based models. The paper presented discusses linear and non- linear finite element methods and compares results with those from physical models and field observations. Special attention is focussed on the determination of the effect of caved zones on overlying and underlying geological structures. The paper presents data from comparisons with U.K. case histories.

Jan 1, 1986