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By Y. -J. Park, K. -H. You, Y. -T. Choi, Lee. H. -W.

Many large caverns are being constructed in great depths in Korea mainly for the storage of oil and LPG. These caverns are mostly located near the port where rock conditions are reasonably good. In some instances, the horizontal stress is very high and endangers the stability of the cavern. The purpose of this study is to assess the stability of large caverns excavated in a rock mass with high horizontal stress where Ko value is close to 3. Result shows that stress exerted in the shotcrete at crown exceeds allowable value when the 3rd bench is excavated. Also found is the tensile failure of shotcrete near the boundaries between benches. In Korea werden viele grosse Kaverne fuer Aufbewahrung vom Oel und Fluessiggas in grosser Tiefe gebaut. Am Meisten befinden sich diese Kaverne in der Naehe von Haefen, wo der Fels gute Verhaeltnisse zum Bauen einer Kaverne besitzt. In einigen Faellen ist die Horizontalspannung sehr gross und dadurch wird die Stabilitaet vom Kaverne gefaerdet. Der Zweck dieser Arbeit ist die Stabilitaet des im Fels gebauten grossen Kavernes mit hoher Horiaontalspannung zu schuetzen, wo Ko-Wert sich auf 3 naehrt. Die Ergebnisse zeigen, dass die Spannung im Spritzbeton an der Krone den zulaessigen Wert ueberschreitet, wenn das dritte Bank ausgegraben wird. Im Bereich des Spritzbetons zwischen Baenke wurde das Zugversagen festgestellt. Des larges cavités nombreuses sont en train d’être construites en grand profondeur en Corée prin-cipalement pour le stocage du pétrole et LPG. Ces cavités sont pour la plupart situées près de la porte oú les conditions des roches sont résonablement bons. En quelques cas, la contrainte hori-zontale est trés haute et met en danger la stabilité de la cavité. L’objet de cet étude est d’estimer la stabilité des large cavités excavées dans une masse de roche ayant une haute contrainte horizontale oú la valeur de Ko est proche à 3. Le résultat montre que la contrainte exercée dans le shotcrete à la couronne dépasse la valeur admissible quand le troisième banc est excavé. En plus une faillite en tension du shotcrete près de la frontière entre des bancs est trouvée.

Jan 1, 2003

By H. B. Hill

The West Red River oil field, in Tillman County, Okla. (fig. 1), is approximately 8 miles northwest of the town of Burkburnett, Wichita County, Tex. The wells are in the river bed between the medial line and the south bank of the Red Diver. In the following discussion of the geology, development, and exploita-tion of the field, the authors have, by means of structure maps, crews sections through various parts of the reservoir and tabulated development data and production statistics, recorded salient information on a field whose development was unique and in some respects unusual for fields discovered and initially developed more than a quarter of a century ago. The total oil production from Government-operated leases; considered in the report was 6,900,440 barrels to January 1, 1947, from 3 proved acres developed by H1 oil-producing wells, 10 gas-injection wells, and 5 nonproductive wells. A calculated past recovery of 60P, barrels of oil per acre-foot and an estimated ultimate recovery of 6.S0 barrels of oil per acre-foot under present gas-injection methods begun in 1929 in shown.

Jan 1, 1949

By Lynn Alcorn, Jeffrey Shawn Peterson

Data collected by the Mine Safety and Health Administration (MSHA) has shown that roof bolting machine (RBM) operators are the second most likely type of underground mining machine operator to be are over exposed to noise, per the MSHA Permissible Exposure Limit. In response to this, the Pittsburgh Research Laboratory of the National Institute for Occupational Safety and Health (NIOSH) has initiated a project to develop engineering noise controls for roof bolting machines. Key to this research is an evaluation of the duty cycle of a typical roof bolting machine operation and this paper presents the results of such an exercise for data collected at two cooperating coalmines. The evaluation entails a time motion study of an operators' shift, logging each activity for time (e.g., tramming the machine, drilling holes, installing the roof bolt, etc.) and the noise levels associated with each task with a Larson Davis Spark 705+ dosimeter. NIOSH post processed the data to determine which tasks the operator devotes the most time to and the noise dosage accumulated during those tasks. These results provide insight into which portion of the operators' duty cycle is the most prominent contributor to noise exposure and thus, where research activities for the development of engineering noise controls should be focused. It was determined that the task of drilling holes is the most significant source of the operators' noise exposure and project research has focused on engineering noise controls to reduce the noise emissions generated during the drilling portion of the machine duty cycle.

By J. C. Yingling, R. J. Sweigard, P. W. Conrad, J. M. Ringe, D. H. Graves

Much of the land reclaimed since enactment of the 1977 Surface Mining Control and Reclamation Act is over-compacted. Research has shown that excessive compaction in replaced growing media is detrimental to establishment of trees. If trees are to be grown on reclaimed surface mined sites, something must be done to alleviate this excessive compaction. Dry bulk density and penetration resistance are two soil parameters that can be used to indicate the level of compaction in reclaimed growing media. The University of Kentucky has developed test cells on reclaimed sites at a surface mine in eastern Kentucky to determine the impact of tillage (ripping) on soil compaction and tree survival rate. The ripping methods being evaluated include shallow tillage using conventional farm equipment and deep tillage using a dozer with a ripping arm. The impact of organic soil supplements on soil physical properties and tree survival rates is also being evaluated at the site. The organic soil supplements being evaluated include application of hardwood bark and application of straw and mulch. Each test cell has been planted with various species of trees, and for the first two years, data have been collected at these test cells for soil dry bulk density, penetration depth and resistance, and survival rate of trees. These data are currently being correlated to determine how ripping and the application of organic soil supplements affects the relationship between soil compaction and tree survival rate.

Jan 1, 2002

By Godfrey MacDonald

"The East West Caribou deposit with an underground mine, concentrator and ancillaries is located 30 km west of Bathurst, New Brunswick. The Restigouche deposit, an open pit mine is 30 km west of East West Caribou. The ore will be trucked from the Restigouche site to the East West Caribou minesite.History:The East West Caribou ore body was discovered in 1955 and the subsequent metallurgical programme focused on producing a bulk sulphide concentrate. However, in 1966 a Mr. P.G. Kihlstadt of Anaconda did float a Copper-Lead concentrate and a Zinc concentrate. He also reported that as the grind became finer the recoveries improved. In 1968 the Mines Branch in Ottawa produced a Lead concentrate of 30 percent at a 60.5 percent recovery and a 52 percent Zinc concentrate at an 83.4 percent recovery.Laboratory testwork proceed the 1988 start up of our current concentrator and underground mine facilities. The concentrator was designed to produce a Lead ""rich"" concentrate and a Zinc ""rich"" concentrate which were combined to make a marketable Bulk concentrate. In 1990 the operation was suspended because of declining base metal prices, increasing smelter treatment charges, increasing operating costs and operating difficulties.The 1997 operating plan is to produce a Lead concentrate and a Zinc concentrate.The Restigouche ore body was discovered in 1989. The subsequent testwork done at Lakefield Research recommended the production of a Copper, a Lead and a Zinc concentrate. The ore reserve could not support a stand alone concentrator so the project was put on hold.Laboratory testwork was carried out at Lakefield Research to confirm compatibility of the East West Caribou ore and the Restigouche ore in their processing."

Jan 1, 1997

By J. C. Edwards, C. C. Hwang

In ventilated tunnel fires, smoke and hot combustion products may form a layer near the ceiling and flow in the direction opposite to the ventilation stream. The existence of this reverse stratified flow has an important bearing on fire fighting and evacuation of underground mine roadways, tunnels and building corridors. In the present study, conducted by the National Institute for Occupational Safety and Health, a CFD program (fire dynamics simulator) based on large eddy simulations (LES) is used to model floor-level fires in a ventilated tunnel. Specifically, the critical ventilation velocity that is just sufficient to prevent the formation of a reverse stratified layer is simulated for two tunnels of different size. The computer code is verified by checking the computed velocity profile against experimental measurements. The CFD results show the leveling-off of the critical ventilation velocity as the heat release rate surpasses a certain value. At this critical ventilation, the ceiling temperature above the fire reaches a maximum for both tunnels. The velocity leveling-off can be explained from this observation. An extended correlation of Newman (Combust. Flame 57 (1984) 33) is applied to the temperature profiles obtained by CFD. At the critical ventilation, temperature stratification exists downstream from the fire. The computed critical ventilation velocity shows fair agreement with available experimental data taken from both horizontal and inclined fire tunnels. The CFD simulations indicate that the Froude modeling is an approximation for tunnel fires. The Froude-scaling law does not apply to two geometrically similar fire tunnels. The CFD results are compared with two simple theories of critical ventilation by Kennedy et al. (ASHRAE Trans. Res. 102(2) (1996) 40) and Kunsch

By X. M. Yuan

In the flotation of Zn-Pb ores, sphalerite is floated following copper sulfide activation. In this type of sulfide ore, pyrite is commonly treated as a gangue, and poor selectivity between sphalerite and pyrite/quartz is often reported. But pyrite may also appear in association with gold, and flotation of such auriferous sulfides is of great importance in many countries (e.g. South Africa, Australia). In the cationic flotation of sulfide ores with dodecyl amine, sphalerite can be floated while depressing quartz and pyrite. While in a well-aerated pulp in the presence of lime (especially after oxidation with H2O2) the cationic flotation of pyrite is depressed, oxidation of pyrite in the presence of Na2S makes it floatable with amines even in very alkaline environment.

Jan 1, 2002

By J. Werfling, J. R. Kiehl

SUMMARY: The effects of blasting on structures are assessed on the basis of the maximum amplitudes of the occuring vibration velocities. If the standard values in the German Standard DIN 4150 are not exceeded, damages to structures are not to be expected. The estimation of the maximum vibration amplitudes is usually based on experience or on emperical formulae. However, a comparison of expected with measured values shows that these estimations are not conservative, particulary in case of small distances between blasting locations and structures. More reliable predictions are possible on the basis of numerical analyses, which simulate the three-dimensional propagation of waves with consideration of the geomechanical and geometrical conditions. In addition to the expected velocities, these analyses also allow the determination of stresses resulting from dynamic loading. If the dynamic stresses are known, the effects of blasting on structures can be predicted. ZUSAMMENFASSUNG: Die Auswirkungen sprengbedingter Erschütterungen auf bauliche Anlagen werden in der Praxis auf der Grundlage der Maximalamplituden der auftretenden Schwinggeschwindigkeiten beurteilt. In der DIN 4150 werden Anhaltswerte angegeben, bei deren Einhaltung Schäden von Gebäuden nicht zu erwarten sind. Die Abschätzung dieser Schwing-geschwindigkeiten erfolgt meist auf der Grundlage von Erfahrungswerten oder empirischer Formeln. Der Vergleich der prognostizierten Werte mit Meßergebnissen zeigt jedoch, daß diese Ansätze insbesondere dann, wenn die Abstände zwischen den Sprengorten und den Gebäuden gering sind, nicht konservativ sind. Zuverlässigere Prognosen sind auf der Grundlage von numerischen Berechnungen möglich, in denen die räumliche Ausbreitung von Erschütterungen unter Berücksichtigung der geomechanischen und geometrischen Verhältnisse simuliert wird. Mit derartigen Berechnungen können die zu erwartenden Schwinggeschwindigkeiten und die aus der dynamischen Beanspruchung resultierenden Spannungen ermittelt werden. Dies ermöglicht Aussagen über die Auswirkungen sprengbedingter Erschütterungen auf Bauwerke. RÉSUMÉ: Les conséquences de vibrations résultantes d'explosions pour des bâtiments sont estimés dans la pratique à partir des amplitudes maximales des vitesses d'oscillation. Dans la norme allemande DIN 4150 des valeurs d'orientation sont données, avec l'observation desquelles de dommage à des bâtiments n'est pas à présumer. Ces vitesses d'oscillation sont estimés généralement à partir de valeurs d'expérience ou de formules empiriques. La comparaison des valeurs prédits avec des résultats de mesures montre cependant que ces hypothèses ne sont pas conservateurs, en particulier si les distances entre les lieux de sautage et les bâtiments sont petites. Des prédictions plus fiables sont possibles à partir de calculs numériques, dans lesquelles la dissipation spatiale de vibrations est simulée en considération de la situation géoméchanique et géométrique. Avec tels calculs les vitesses de vibration à présumer et les contraintes résultantes de l'effort dynamique peuvent être établies. Cela permet de constater sur les conséquences de vibrations résultantes d'explosions pour des bâtiments.

Jan 1, 2003

THE CHAIRMAN.- This meeting is under the auspices of the American Institute of Mining and Metallurgical Engineers, and I think the germ of the idea originated in the steel business. Last year there was a meeting of prominent people in the steel industry with the idea of getting together and discussing practical phases of their business, so that everybody could contribute and from that there might be benefit derived for the industry. Several months ago when Mr. Bain was in Salt Lake City, he and Mr. Oldright asked me what I, as an individual, thought of it. From that originated this idea of having the copper people come together to discuss reverberatory smelting and all its phases. In starting out, it seemed the best plan to ask members what particular subjects they wished to discuss first; that is, the ones that would be considered more important. We asked Mr. Oldright, or suggested sometime ago that the meeting be postponed until May because May is a lovely month in Salt Lake. There are a number of attractive features around the city. We have a number of smelters here and I think that probably the most of the benefit will be derived from talking in an informal way and visiting the various plants around. the valley. At any rate, speaking as a resident of Salt Lake, I am glad to see all of you gentlemen here, and hope you have an interesting and instructive time. The tentative list of subjects for discussion at this conference is as follows: Construction Walls, etc. Walls, proper design and thickness of brick for various types of charging. Bottoms, construction of. Binding steel, correct weight and arrangement, where thrust of arch should be taken. Refractory materials, feasibility of using different material in various parts of the furnace. Water jackets, where applicable. Should bricks be used inside of same. Gas space, proper design for, height of roof above bath, etc. Roof Shape of Roof, in hot zone and elsewhere, longitudinally. Construction of roof, in various zones, around openings.

Jan 1, 1930

By R. V. Higgins, G. B. Shea

"FOREWORDIn the second year of World War II, the petroleum industry in California was taxed to near capacity to satisfy the expanded war demand for petroleum products, particularly fuel oil. With discoveries of crude oil in California declining and known reserves being depleted rapidly, conditions appeared to warrant study of the possibilities of utilizing the outcropping bituminous sandstone deposits in California for obtaining new sources of oil if the war should he prolonged. At conferences in Washington, D. C., with members of the Petroleum Administration for War and the Geological Survey, Bureau of Mines engineers emphasized the importance of determining the extent of those outcropping deposits of oil-impregnated rocks and of developing a practical process for commercial recovery of the contained bitumen to assure, if necessary, a supplementary supply of fuels. The desirability of such a study was recognized, and in July 1943 the Petroleum Field Office of the Bureau of Mines at San Francisco, Calif., in cooperation with the Geological Survey and the Petroleum Administration for War, initiated a study of the bituminouss sandstone problem. It was agreed that all mapping and geological work in connection with the study would be done by the Geological Survey, all engineering studies in developing a process for extracting the oil would be carried out, by the Bureau of Mines, and that the Petroleum Administration for War would aid in final adoption of the results in the field if circumstances warranted such action.Deposits of bituminous sandstones in California occur principally in the immediate region of the Coast Range mountains, notably at Pt. Arena, in Mendocino County, about 110 miles north of San Francisco; near Santa Cruz, in Santa Cruz County; in the Edna area in San Luis Obispo County; in the Sisquoc area in Santa Barbara County; and in the Ojai and Santa Clara Valleys in Ventura County. 4/ In addition oil-bearing sands outcrop near McKittrick and Maricopa, in western Kern County, and along the east edge of the Kern River oil field. Among the several prominent deposits of these source materials, those occurring near the cities of Santa Cruz and San Luis Obispo, and the town of Sisquoc are the largess."

Oct 1, 1948

By L. C. Brown, C. St. John, C. C. Sanderson

The diffusion rate in Cu-Te couples is very sensitive to compressive stress, with a load of 20 psi making a significant difference to the width of the diffusion zone. At zero stress, two phases appear in the diffusion zone (Cu4Te3 and CuTe). Under compressive loading the third stable phase (Cuz Te) also appears, and its thickness increases progressively with increasing stress. The results are explained on the basis of an incipient Kirkendall porosity which restricts the transfer of atoms from the copper into the diffusion zone. DURING a study of the Kirkendall effect in Cu-Te couples prepared by clamping together the two components, it was found that the diffusion-zone width and shape in the plane of contact were not reproducible. Although the stresses involved in clamping are not normally sufficiently high to affect diffusion rates, preliminary tests established that the Cu-Te system is particularly stress-sensitive. The phase diagram for the system Cu-Te given in Hanssen1 shows that there is practically no solid solubility at either end of the phase diagram. Many areas of the diagram are not fully substantiated, but there appear to be three intermediate phases: Cu,Te—hexagonal in structure, having a grey luster; Cu4Te3—a tetragonal defect structure, having a red-purple luster; CuTe—orthorhombic in structure and having a golden-green luster. The existence of a fourth phase, the X phase at 37 at. pct Te, is considered doubtful. The composition ranges of the three stable phases are small, and are not accurately known. The phase diagram changes little with temperature up to 305°C, at which temperature a polymorphic transformation takes place in Cu2Te. The nature of the Cu-Te phase diagram indicates that the diffusion zone in a Cu-Te couple would consist of a series of layers of intermediate phases. The relative thickness of any one phase will depend on its diffusion coefficient and composition range.' In this type of diffusion couple it is often found experimentally that some phases are not visible at all in the diffusion zone due either to a small diffusion coefficient or to a restricted composition range.3 Since the composition ranges of the phases in Cu-Te are not known, it is not possible to determine diffusion coefficients in this system from a knowledge of the phase thicknesses. Several investigations have been carried out to determine the effect of compressive stress on diffusion rates in multiphase systems. Diffusion couples of Ni-A1 have been investigated by Storchheim et al.4 and by Castleman and Seigle.5 Two phases (ß and ?) appear in the diffusion zone under zero stress and the thickness of both phases is progressively reduced with increasing stress. According to Storchheim et al.4 a stress of 25,000 psi reduces the thickness of the diffusion zone by 50 pct. In a-brass—?-brass couples the thickness of the 0 phase formed in the diffusion zone was reduced by 20 pct at a stress of 20,000 psi.6 In other investigations the compressive load has been observed to increase the width of the diffusion zone. In A1-U, several investigators3,8 have found the width of the whase UA13 to increase with stress. According to casileman,8 the rate of formation of UA13 at 520°C is 75 pct faster at a stress of 20,000 psi as compared with a stress of 2500 psi. In Cu-Sb the effect of stress is greater than in the other systems described. According to Heumann9,10 only one phase (y) appears in the diffusion zone at a stress of 500 psi, but at a stress of 850 psi two phases (y and k) are present. If a diffusion couple containing both y and k phases is annealed at a low stress level, the y phase grows at the expense of the k phase. EXPERIMENTAL The diffusion couples were prepared from electrolytic copper bar stock with a nominal purity of 99.92 pct and from tellurium of 99.7 pct purity. The tellurium proved difficult to machine because of its brittleness and a technique was developed for casting the tellurium into a graphite slab mold and spark-machining specimens from this slab. Both the copper and tellurium were produced in the form of discs 2 in. diam by approximately 1/4 in. thick with surfaces ground flat to 3/0 emery paper. The diffusion apparatus is shown in Fig. 1. Auni-axial compressive stress was applied to the system through a simple lever system. A stainless-steel rod actuated by the lever arm lay inside a stainless-steel tube. The diffusion couple lay on top of the steel rod, and pressure was applied to the couple between the rod and a plug welded into the center of the tube. To ensure a uniform stress across the couple, a hemispherical boss and cup were used to transmit the load to the diffusion couple. A 400-w tube furnace with a uniform hot zone 3 in. long slid around the stainless-steel tube and maintained the assembly at temperature. A thermocouple situated 3 in. from the specimen operated a proportional temperature controller which maintained the specimen temperature constant to ±2°C. Most diffusion runs were carried out at 250C although a few tests were made at other temperatures in the range 235° to 300°C. The specimens were inserted and removed with the furnace at operating temperature, and took only 2 min to reach diffusion temperature—a time small compared with the total diffusion time. All the diffusion experiments were carried out in a hydrogen atmosphere, since consistent results were obtained in hydrogen and nitrogen atmospheres and in

Jan 1, 1967

By M. Kul

In this study, the effects of various extraction and stripping parameters, such as equilibrium pH (7.0, 8.5 and 10), extractant concentration (5, 10 and 20 volume %), organic-to-aqueous (O/A) ratio and stripping agent type and concentration were studied on chromium (VI) recovery from chromium electroplating rinse bath wastewater using Aliquat 336. Results showed that these parameters all had significant effects on chromium (VI) recovery. A pregnant strip solution from a chromium electroplating rinse bath wastewater with 33.4 g/L chromium content, suitable for sodium dichromate production, was generated by 20 vol. % Aliquat 336 in commercial kerosene. The O/A ratio was 1/4 and the equilibrium pH value was 0.87, the as-received pH value. The wastewater was treated with a two-stage countercurrent extraction process to produce a loaded organic phase, which was later stripped at the O/A ratio of two with a 4-M NaOH solution in a two-stage countercurrent stripping process using Taguchi?s optimization technique.

Jan 1, 2010

By George Hope, Brigitte Lacouture

"The Red Dog Mine has increased mill throughput for most years since startup. Although flotation equipment has been added over the last 10 years, the Red Dog metallurgical performance has been restricted by a lack of adequate flotation capacity. Two reduced tonnage trials conducted in 1997 as well as numerous SAG relines have consistently indicated the potential to significantly increase both zinc concentrate recovery and grade with additional flotation capacity. Late in 1999, a new circuit was designed with increased flotation capacity while simplifylng the current circuit, providing for three stages of dilution cleaning, and creating a retreat section. The purpose of the retreat section is to target the more complex particles and allow the chemical environment to be fine tuned for improved iron depression. In total, twentyone (21) Outokumpu OK50 mechanical flotation cells and four (4) 3.66m dia. column cells will be added to the current flotation circuit. The VIP (Value Improvement Program) Mill Optimization project is also addressing thickening, water treatment and power issues and has a total budget of $US105 M. Startup of equipment will be phased in to minimize the impact on current operations and is expected to be complete by the end of Q3-2001.INTRODUCTIONRed Dog Operations started production in November 1989. The mine is located above the arctic circle in northwest Alaska. It is linked by an 80 km road to a port-site facility where the concentrate is stored. Concentrate is shipped to markets throughout the world during the one hundred (100) days of open seas. Typical of sedimentary exhalative deposits, the metallurgy proved to be challenging and coupled with many mechanical shortcomings, the initial few years were very difficult. The start-up issues were slowly resolved and in 1998, a major grinding expansion, the PRI (Production Rate Increase) project, was completed. The project was designed to allow a 40% increase over the 1995 throughput. In 2000 mill throughput was 3,050,000 tonnes to produce a total of 960,000 and 140,000 dry tonnes of zinc and lead concentrates respectively, making Red Dog the largest zinc concentrate producer in the world. To address a shortage of flotation capacity remaining from the PRI grinding expansion, a project designated as the VIP (Value Improvement Program) Mill Optimization project was initiated. The mill optimization project is targeted to produce 1,100,000 tonnes of zinc concentrate at 56% zinc grade and 87% zinc recovery. The project will add twenty-one (21) Outokumpu OK50 (50m3) flotation cells, four (4) 3.66mO column cells and address water treatment, thickening and power generation capacities."

Jan 1, 2002

By Douglas F. Scott

In 1981 the U.S. Bureau of Mines and U.S. Geological Survey conducted a mineral survey of the Pyramid RARE II area (No. 5023) covering 23,500 acres (9,500 ha) of E1 Dorado National Forest and 7,900 acres (3,200 ha) of the Lake Tahoe Basin Management Unit (fig. 1). The Bureau of Mines investigation did not reveal mineral deposits in the area. Samples taken from silicified and limonite-stained metasedimentary rocks and aplite dikes were void of precious or base metals or uranium. Placer samples from stream gravels contained no gold values. Molybdenite occurs in quartz stringers within quartz monzonite near Grass Lake, adjacent to the area; no extension; were found in the area.

Jan 1, 1982

By Robert Hopler

It is the nature of the initial detonation to the powder around the cap which governs the greater or less effect of the explosion of the whole charge. The cap communicates to the first particles of powder a disruptive impulse, which, according to the nature and strength of the cap, more or less completely overthrows their equilibrium and decomposes the powder with great energy, setting up sympathetic vibrations that explode the particles of powder in turn by the violent disturbances or friction between them in a regular succession of impulses and decompositions, which, if started with sufficient energy, are of such intense heat and velocity that the rupturing force of the explosive is developed practically instantaneously. This detonation has already been shown to be not only the result of mechanical force, but a combination of extremely sudden chemical and dynamical reactions which set up vibrations to which different powders are more or less susceptible, and these explosive reactions will be propagated through the mass of the powder according to the intensity of the vibrations and the resistance with which their motion is opposed by the nature and consistency of the powder, whether it be difficult or easy to oxidize, soft and plastic like dynamite, or hard. If the initial detonation of the powder surrounding the cap is of the highest degree, the vibrations will be most intense and will be propagated further through the mass than by a poorer detonation. Hence the different degrees of detonation. Unless the first particles of powder are so thoroughly decomposed by a detonation of high order, or first degree, as to convey the necessary heat and energy to detonate the whole charge, the greatest force of the powder will not be developed. There will frequently be unbottomed holes or pieces of unexploded powder scattered about, or both, and the air in the mine will be contaminated with some obnoxious gases that have not been completely oxidized.

Jan 1, 2007

By D. A. Kramer

Ammonia, the principal source of fixed nitrogen, was produced by 16 companies at 31 plants in the United States during 2003. Fifty-five percent of U.S. ammonia production capacity was centered in Louisiana, Oklahoma and Texas because of their large reserves of natural gas, the dominant domestic feedstock. Production In 2004, U.S. producers operated at about 59 percent of their rated capacity. The United States remained the world’s second largest ammonia producer and consumer following China. Urea, ammonium nitrate, ammonium phosphates, nitric acid and ammonium sulfate were the major derivatives of ammonia in the United States, in descending order of importance.

Jan 1, 2005

By T. E. Bernard

Occupying a refuge alternative (RA) is an accepted practice in mine fires and explosions when escape is not feasible. MSHA has promulgated a final rule on refuge alternatives that includes a recognition that thermal environment is an important consideration. To this end, an environmental index was specified. The question remains about how to test a refuge shelter to demonstrate that it meets the final rule. The analysis followed five activities: A. Provide an estimate of heat generated by an individual refuge alternative occupant; B. Evaluate the Steadman Apparent Temperature criterion of 95°F; C. Discuss simulations based on body temperature or skin temperature limits; D. Suggest method of simulating human heat generation during refuge occupancy; and E. Suggest alternative methodologies/criteria for evaluating heat and humidity survivability inside a refuge alternative.

Feb 27, 2013

By Braam Blom

PK2 Ventilation shaft is part of Paardekraal No 2 twin shaft system that is being developed to replace depleting Merensky reef production at Paardekraal shaft complex. The sinking team at this shaft faced considerable challenge of improving the total sinking cycle in order to be able to deliver the fully equipped shaft on time and on schedule. The cladding support cycle was identified as the tedious and time consuming activity in the overall shaft sinking operation. Reduction in the time required for handling and setting up the support installation equipment, and the time required for subsequent installation of the necessary support has a direct impact on the overall cycle time, and consequently the overall productivity and efficiency of the sinking operation. This reduction in support cycle was achieved by making use of machine carousel. The objective of this paper is to describe the support methodology that was used during the ventilation shaft sinking and the use of the machine carousel to reduce the cladding support cycle. The machine carousel replaces the traditional use of machine kibble in conventional vertical shaft sinking and has been designed specifically for installation of sidewall support at the shaft bottom during the sinking process.

Jan 1, 2009

By M Nehring, E Topal

Nowadays mining projects are seeking new versions of evaluation that are based on the flexibility in the project. Real option valuation (ROV) is one of the modern evaluation methods that provides a tool to adapt and revise mining projects under uncertainty and future variable movements. Most evaluation approaches simply assume that some variables are fixed, such as production rate, variable cost, fixed cost and lifetime of project. The first section of this paper reviews a comprehensive study of ROV in mining projects. The paper then introduces a new model that solves problems where previous methods lacked. The new method endeavours to find maximum mining project value by adding total cost as a function of production rate into ROV. The second section has been applied to a new model on the Century zinc mine in north-west Queensland, thus illustrating the future overview of that mine. The new version of ROV gave a significant positive value for the Century Mine, when the closure and reopening options where available throughout the life of the mine. Consequently, the new method evaluates real options to add value to mining projects, maximising projectÆs value, estimating cost function, optimising production rates and offers opportunities in projects to amplify gains or to mitigate losses.

Jan 1, 2009

By C. Ketata, M. C. Rockwell

During the operation of a mineral processing plant, the unit processes are investigated by analyzing the data extracted by means of stream sampling. The data structure is identical to the time series form. Data analysis is a crucial step in understanding the plant performance. To control the plant performance efficiently, it is very important to avoid sampling errors, which is impossible. However, it is possible to minimize these errors. The factors influencing these errors are divided into two categories: material properties illustrating its heterogeneity, and sampler features. The purpose of this paper is to study the influence of the material composition variation on sampling errors, and to compare our evaluation method with that of Gy. Note that the stream mass flowrate is assumed to be constant during the sampling process.

Jan 1, 2001