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By I Villalba

The need to continue the development of the Ensham mine has led to blast up to 75 m to the Eastern side of a water dam in the vicinity of Ramp 23. The water dam wall is exposed to blasting over a distance of approximately 500 m. The first decision was to determine that the existing rock pillar between the Eastern side of the water dam and the blasting operations may not be less than 75 m in order to minimise the damage that the blast could generate to the dam wall. It was also necessary to define blasting practices to minimising the blast damage to the rock properties of the dam wall and to avoid adverse effects from vibration and gases generated by the detonation on structures.For this purpose analytical designs and test blasts were conducted to assess the ground vibration attenuation within the rock pillar. From this analysis, it was concluded that the best practice to reduce the rock damage was to create a zone of fractured rock adjacent to the side of each production blast. This fractured zone would create an effective filter both for vibration and for gases generated by the blast. This zone of fractured rock was created by firing two buffer rows. In terms of pattern size and powder factor the two buffer rows were designed just to generate a fractured rock zone. To date approximately 500 m have been excavated along the eastern wall of the water dam where each production blast was preceded by a Trim blast. This practice has given good results with regard to minimising the damage generated by production blasting.

Nov 8, 2011

By C. G. Storm

Permissible explosives are those that have passed the tests pre- scribed by the Bureau of Mines for explosives intended for use in coal mines, and are therefore recommended by the bureau as suitable for this class of work when used under the prescribed conditions. The tests for permissible explosives and the conditions prescribed for their use are described in Miners' Circular 6 of the Bureau of Mines. Up to June 1, 1915, 168 explosives had been classed as per- missible explosives; 133 of them were then on the bureau's "per- missible list" and 35 had been withdrawn by the manufacturers. In addition to the required physical tests, each explosive is sub- jected to a complete chemical examination in order that its exact composition may be known and also that the composition of future samples of the same explosive collected in the field may be compared with that of the sample which originally passed the bureau's tests, for by such comparison it may be possible to ascertain whether or not the explosive as supplied to the miner is still "permissible." This bulletin is published primarily for the purpose of informing manufacturers of such explosives as to the methods used by the Bureau of Mines in the analysis of samples received for tests to determine their permissibility. Such information may be of value in cases of possible controversy over the results obtained in the analysis of a field sample as compared with those obtained in ana- lyzing the sample originally tested by the bureau. Also, a descrip- tion of the methods used by the Bureau of Mines in the analysis of explosives should be of assistance to the many chemists engaged in similar analytical work.

Jan 1, 1916

By J. Owens

Advanced materials development ranks as one of the most important high-tech industries of the future in the United States. Recent breakthroughs can be attributed to advanced computer technology, powerful mathematical models, and more precise analytical tools that enable scientists to examine and control properties of materials as never before. Discoveries now being made are providing many industries with opportunities to improve product lines, fabrication techniques, product reliability, and so forth. More¬over, industries, such as space, medicine, and defense, which require stringent: design and perfomance specifications in highly competitive world markets, increasingly demand these new materials. The definition of advanced materials used here is one that has been adopted by the U. S. Bureau of Mines: Those materials which have been developed over the past 30 years or so, and which are being developed at present, that exhibit greater strength, higher strength-density ratios, greater hardness, and/or one or more superior thermal, electrical, optical, or chemical properties, when compared with traditional materials.

Jan 1, 1991

By R. C. Bryan, D. B. Jamison

This paper describes a procedure for minimizing the operational costs associated with blending sodium in coal at a surface mine in the Powder River Basin. Mine site blending is performed by adjusting daily production rates for high- and low-sodium pits. These adjustments are designed to produce a consistent sodium value called the blending target. The mine's contractual limit for sodium is sufficiently close to the field average value that any decrease in the sodium blending target may result in an opportunity cost, if the number of potentially minable tons is reduced. Conversely, any increase in the blending target may result in a higher sampling cost if more information is required to keep the blend within contractual limits. Blending parameters were defined using a geostatistical block model of sodium content that was based on analyses of hundreds of in-pit sample holes. Variograms for these data were used to compute the marginal costs of opportunity and sampling for a series of hypothetical in-pit drilling patterns. These marginal costs provided a basis for selecting optimum values for key parameters such as the blending target, production variance and in-pit sampling density. The benefit of implementing these optimized parameter values is that operational costs of sodium blending will be minimized over the long-term. At the mine where this procedure was developed, each dollar spent to increase the sampling density to the optimum value was shown to generate a $10 savings in opportunity cost.

Jan 1, 1991

By O. C. Blade

This report on the properties of aviation gasolines and aviation jet fuels produced in the United States during 1956 was made under a cooperative agreement between the American Petroleum Institute and the Bureau of Mines of the United States Department of the Interior. Analytical data are presented for 120 samples of aviation gasoline and for 38 samples of aviation jet fuel. The analyses were made on samples typical of the manufacturers' 1956 production in their laboratories and the results submitted to the Bureau of Mines for compilation. The products of 20 manufacturers of aviation gasolines and of 17 producers of aviation jet fuels are represented.

Jan 1, 1957

By Claude Cunningham

Ths oonoept of precise. eooursts timing with Elsotronic Delay Detonators (EDD’s) was first ssriously sddresssd in ths mid 80’s end much wss made of the cheapness end profusion of digital wstohes in terms of the likelihood of EDD’s also being cheap and essyto produce. Ten years Iater. with every major explosives group end many elsotronios groups having instituted projects to capitalize on the promise of these devices, production devices are still to come into asneral use.

Jan 1, 1994

By R. Armstrong

The stability of rock slopes is significantly influenced by their curvature in plan view. The importance of this in open pit mining is indicated by the fact that, in a deep pit, steepening of the slopes by 1° may save as much as $100 million. It is considered that there are two significant factors that play a part in the influence of plan curvature. These two factors are the effect of stress, and the effect of geological structure. The scant literature that pertains to this aspect of rock slope design was reviewed. The geometrical influence of the plan curvature was then investigated. It was seen that it has a parabolic effect on the maximum possible wedge that can fail into a circular pit, where the tighter the concave curvature the smaller the wedge. The plan curvature also affects the volume of a particular wedge, where concave slopes result in an exponential decrease in the volumes and convex slopes have exponentially increased wedge volumes. A change in the strike of the wedge did not affect the curvature’s influence on the volume, but the volumes of shallower dipping wedges were affected more by the influence of the plan curvature. La stabilité des talus des roches est très influence par la courbure de celles ci dans la vue en plan.Son importance de l peut arriver à sauver même $100 millions. Il est considère qu il y a deux facteurs importants qui jouent une influence sur cette courbure. Il s’agit de l’effet des contraintes et l’effet de la structure géologique. La brève littérature qui se réfère à cet aspect du conception sur le talus des roches a été revue. L’influence géométrique de la courbure des plans a été investiguée. Il a été vu que cela un effet parabolique sur la bosse ou le su relèvement maximum possible qui peut faillir dans un puits circulaire, ou le plus resserre est la courbure concave, le plus petit est su relèvement (bosse). La courbure plane aussi affecte le volume d’un particulier su relèvement ou les talus concaves résultent dans une décroissance exponentielle en volume alors que les talus convexes accroissent la volume de ces su relèvements (bosse). Le changement de l’orientation de la bosse (su relèvement) perpendiculairement ou obliquement n’ a par affecte l’influence de al courbure sur le volume mais les volumes des bosse (su relèvement) peu profonds étaient affectes par la courbure des plans. Die Stabilität der Felsensteigungen wird erheblich durch ihre Biegung im Plan beeinflußt. Der Wert von diesem in der Tagebaugrube wird durch die diese Tatsache, in einer tiefen Grube, steepening der Steigungen durch 1° angezeigt; kann soviel wie $100 Million speichern. Es wird betrachtet, daß es zwei bedeutende Faktoren gibt, die eine Rolle im Einfluß der Planbiegung spielen. Diese zwei Faktoren sind der Effekt des Druckes und der Effekt der geologischen Struktur. Die dürftige Literatur, die diesen Aspekt des Felsensteigungdesigns betrifft, wurde wiederholt. Der geometrische Einfluß der Planbiegung wurde dann nachgeforscht. Es wurde gesehen, daß es einen Parabolischen Effekt auf dem maximalen möglichen Keil hat, der in eine kreisförmige Grube ausfallen kann, wo, das fester die konkave Biegung, das kleiner der Keil. Die Planbiegung beeinflußt auch das Volumen eines bestimmten Keils, in dem konkave Steigungen eine exponentiale Abnahme an den Volumen ergeben und konvexe Steigungen exponential Keilvolumen erhöht haben. Eine Änderung im Schlag des Keils beeinflußte nicht den Einfluß der Biegung auf das Volumen, aber den Volu

Jan 1, 2003

By Henry Antwi

The decade of the 1990s promises to be one of increasing internationalization for domestic minerals producers as they scramble to enhance relative positions in highly competitive, international minerals markets. This "international mining rush" is fueled by developing countries seeking international investment capital to explore for, develop and exploit sizable mineral endowments in an attempt to support the increasingly popular, but expensive, wave of democracy and selfdetermination sweeping the world. This "fuel" typically takes the form of revised mining codes and, often, lucrative investment incentives. These incentives include favorable tax rates, royalty provisions, relaxation of import/ export constraints, depreciation schedules, profit repatriation and other variables that can positively impact mineral investment decision making. Concomitantly, in their attempts to address real and perceived short- and long-term woes associated with enhancing competitive positions internationally, many domestic explorers and producers are attracted to the prospect of finding high-grade deposits in relatively virgin areas. Combined with the investment incentives provided by foreign governments, these high-grade deposits promise lucrative potential returns from projects having short payback periods. Classic examples of this mutual desire to intensify international mining efforts by domestic producers are illustrated by activity levels in countries like Chile, Bolivia and Venezuela in Latin America and, more recently, in Eastern Europe and select locations in the former Soviet Union. As US corporations scurry to send fact-finding, technical, evaluation and financial teams to these presently popular locations, one area of the world has received little attention - Subsaharan Africa. Specifically, the country of Ghana (formerly the Gold Coast) deserves more attention than it appears to be receiving from North American mining companies.

Jan 1, 1992

By H. Jehn

The high-temperature oxidation of Pt metals results' in the formation of volatile oxides. The evaporation of which considerably increases the metal losses in oxygen-containing atmospheres when compared with high-vacuum or inert-atomosphere conditions. The paper describes gravimetric investigations carried out to determine the metal losses of polycrystalline samples of Ru, together with earlier studies on Ir and Pt at oxygen pressures of 10-3 to 1000 mbar and temperatures > 1000 °C. A strong pressure and temperature dependence is noted. Preliminary results of the oxidation of Pd are reported, too (665 mbar 02, 1100-1300 °C). The oxidation mechanism is discussed and the oxidation rates of Ru, Pd, Ir and Pt are compared with those of the other Pt metals Rh and 0s and of refractory metals.

Jan 1, 1984

By Raymond B. Ladoo

Silica , or silicon dioxide , ( Si0, ) , occurs in a free state chiefly as quartz , but hydrous silica ( amorphous silica carrying a variable amount of combined water , 2 to 13 per cent ) , occurs as opal , flint , diatomaceous earth , tripoli and so on . Quartz is found in many forms , the most important of which are ; As vein quartz; quartzite ; sandstone ; silica sand and gravel ; as crystals or crystalline grains , masses or aggregates in igneous rocks such as granites , dicrites and pegmatites . Commercially silica is used in many ways , but ordinary uses of sand and gravel are so well known that they will not be considered here .

Jan 1, 1922

By J. A. Finch, S. T. Hall

An oxidative alkaline pressure leach is shown to increase the magnetic susceptibility of coal-pyrite particles. The leach was successfully exploited as a pretreatment in the magnetic desulfurization of an eastern Canadian coal. Greater than 50% total sulfur (65% pyritic sulfur) rejection at 85% clean coal yield was achieved using a high-gradient magnetic separator (HGMS) at 1.3 T and 53 mm/s (2 in. per sec) flow rate, after pretreatment at 0.5 mot NaOH, 85ºC (185ºF), 930 kPa (135 psi) air pressure, 15 minutes retention time, and 20% solids by weight (w/w). Without pretreatment, sulfur rejection at these HGMS settings was less than 5%.

Jan 1, 1985

By John Garcia

THE presence of carbon de terre along the banks of the Illinois river was noted by the members of the Joliet and Marquette expeditions in 1673, and that may be referred to as the birthday of coal in the Middle West. The march of progress in the majority of indus-tries radiating from Chicago-one of the phenomena of history-is due in no small measure to this same carbon de terre and to the development and exploita-tion of the vast coal resources, which nature in a generous mood spread so lavishly over almost the en-tire state. The geological records indicate that coal-bearing rocks underlie three-quarters of Illinois, in-cluding 85 of the 102 counties and the entire area is estimated at from 36,000 to 42,000 square miles. Not all of the coal in this great area may be mined under the conditions existing today; producers are now taking the "cream" since industry demands the best quality and the lowest cost, thereby forcing competition among operators, which, in turn, com-pels the development of mines in those areas where the coal may be most readily .won, leaving the coal that is more difficult and expensive to mine to pos-terity. This is not such a bad arrangement, since the engineers of succeeding generations will enjoy the advantage of the experience of their ancestors, where-by they should profit and know how to mine a 2-ft. seam with as much economy and dispatch as we today work coal of thrice that thickness. During the period between 1830 and 1850, Illinois coal-mining progressed from the art of scratching along the outcrop to the development of small mines, mostly slopes, drifts and shallow shafts, but the real progress in the industry was coincident with the con-struction of railroads.

Jan 2, 1927

By C. S. Barrett

IT has been observed that deformation in iron takes place by slip on {110} + {112} + {123} planes1,2 but in silicon ferrite with low deforma-tion temperatures or high silicon contents (exceeding 4 per cent) the authors have found that slip is confined wholly to {110} planes, at least with small amounts of deformation. The purpose of the present inves-tigation was to determine the effect of this alteration of slip mechanism on preferred orientations in cold-rolled and recrystallized strips. Inci-dental observations on the effect of the recrystallization temperature were also made. The numerous determinations of the texture of cold-rolled iron and steel have been in satisfactory agreement as to the principal features of the texture. (with the exception of a few conclusions that apparently have been based on insufficient data). The texture is chiefly one in which [110] directions of the grains lie along tile direction of rolling, with a deviation of a few degrees, and in which the (100) planes lie in the plane of the rolled sheet, with a deviation from this position chiefly about the rolling direc-tion as all axis 3-9. This deviation about the rolling direction as an axis has been measured by different observers and lies between about 45° and 50° or 60° for iron5,6,9 and is usually in the neighborhood of 50° for mild steel6,7,8. The range of this deviation is a function of the percentage of total reduction 8, 10. Post' reported that it decreases with increasing percentage reduction, but apparently he .studied only the surface material, which Gensamer and Mehl7 found to be somewhat differently oriented from the material in the inside of the sheet. McLachlan and Davey10 found that the deviation also decreases with increasing percentage of total reduction for the material in the interior of the sheet and is independent of the percentage of reduction per pass.

Jan 1, 1937

By Cardm Jeffrey W.

The decay of 222 Rn yields a series of short-lived decay products which become attached to the surface of a plate or wire exposed in a 222Rn-bearing atmosphere. The alpha-activity of two of the decay products, 218Po and 214Po, can be measured by simple counting techniques. This phenomenon may have direct application to uranium exploration. Laboratory studies have shown that: (a) radon decay products can be collected on a wide variety of materials (including various kinds of metals and plastics); (b) activity increases as a function of the surface area of the 'collector; and (c) the collection of the decay products is enhanced by applying a negative charge. The new technique was used in situ to delineate the anomaly above the South March uranium-copper occurrence. A related technique was developed to measure radium in soil samples. The results of both studies compared favourably with those obtained from conventional methods.

Jan 1, 1979

By Frederic Becket

IN a recent article,1 which described the softening effect of columbium in plain high-chromium steels, the authors stated that their investi-gations had shown columbium to be also a particularly valuable inhibitor of intergranular corrosion in steels of the 18 per cent chromium, 8 per cent nickel type. It is the purpose of the present paper to record some of the results obtained through the introduction of columbium to the austenitic chromium-nickel steels. The damaging effects of this type of corrosion have become so widely known as to restrict considerably the applications of the steels under consideration, and therefore there is little question of the importance of the goal to be attained. Numerous contributions concerning the susceptibility of the aus-tenitic chromium-nickel steels to intergranular corrosion have appeared during the past few years, and among others who have dealt construc-tively with the subject are such well-known authors as Strauss and Houdremont of Germany, Hatfield of England, and Bain in the United States. Different theories have been propounded as to the cause of intergranular corrosion, and various remedial measures have been proposed, the majority of which involve the use of addition agents. Titanium is the addition agent at present most generally employed, as suggested by Houdremont and modified as described by Bain, Aborn and Rutherford.2 Little has been published on the effects of holding these steels for long periods at the relatively lower temperatures in the presence of

Jan 1, 1934

By I. C. Edwards, E. O. Lilge, H. H. Mccreedy

"Introductory and GeneralTHE DRIESSEN CONE bas been used fairly extensively commercially as a classifier. Its use as a concentrator in the upgrading of ores at a fairly high ratio of concentration with concomitant recoveries has been almost negligible. Certain known features about the cone, however, such as its high throughput capacity, cheapness of construction and operation, and simplicity of design have attracted the attention of mill men. An inadequate knowledge of the operating characteristics of the cone when used as a concentrator seems to have been the main reason for its lack of use. It was for this reason that the present investigations§ were undertaken to determine the operating characteristics of the cone and its application to the concentration of uranium ores, with particular emphasis being placed on the concentration of low-grade uranium ores.The investigations were started in December, 1951, and have continued uninterrupted to the present. The initial work was confined chiefly to investigating the operating characteristics of the cone in order to establish the trends that certain variables would exert on the general metallurgy of uranium concentration. Optimum metallurgy was therefore not the prime initial objective."

Jan 1, 1955

By W. Pariseau, J. Goris, S. R. Dismuke

Ore at the Magmont mine in southeast Missouri is extracted by the room-and-pillar method on two and sometimes three horizons. In 1991, a plan was formulated to recover high-grade ore in pillars using cable halts to accommodate spans of more than 27 m (90 ft ). A test area was selected and a recovery plan developed. A cooperative rock mechanics study was established by Cominco Metals, the US Bureau of Mines and the University of Utah. When initially opened in 1968, the planned production rate was about 910 kt/a (1 million stpy). Due to declining reserves, the production rate was decreased in November 1992 to 570 kt/a (630.000 stpy). Pillar recovery now accounts for about 40% to 50% of the mined tonnage. This method plays a vital role in allowing Magmont to continue to operate.

Jan 1, 1996

By Catherine Aimone-Martin, Mary-Alena Martell

Whole-structure and mid-wall responses of 33 non-traditional structures to surface coal mine blasting were characterized. Eighty-nine blasts were conducted at 11 mine sites throughout the U.S. to measure blastgenerated dynamic response of structures typically found in the proximity of surface coal mining. Structures selected for this study include log-type, manufactured (single- and double-wide trailers), “mine camp”-type, adobe, and stone. Traditional acoustic microphones, t&axial (ground) and single component (structure) velocity transducers were used to record airblast, ground motions, and structures response time histories with a common time base. Wall crack displacement gages were used to record static and dynamic movement of existing drywall cracks. The relative responses of selected “atypical” structures to blast vibrations and nonblasting causes of structural stress, including natural forces, environmental effects, and human habitation, are compared. The purpose of this study is to document and compare vibration characteristics of structures that were not included in previous studies conducted by the U.S. Bureau of Mines and others in establishing the widely adopted safe level blast vibration criteria in the U.S. An important objective of this study is to outline an evaluation process including structure uniqueness relative to cracking susceptibility.

Jan 1, 2002

By Whiten W. J

A simulation model was used to study the performance of various types of screen cloth on industrial vibrating screens. The model takes into account the effect of loading upon screen performance and predicts both themass flow rate and size distribution of the screen products.It was found that the use of the simulation model allowed the reconstruction of data for identical conditions and hence has simplified the analysis of the comparative performance of the screens. The dependence of performance upon operating conditions was found to vary markedly with screen cloth type.

Jan 1, 1977

By G. A. Vissac

In continental Europe the feldspar jig is used almost exclusively for cleaning the fine sizes of coal; it operates with an artificial bed, made up generally of pieces of feldspar or of any other hard and heavy rock with good cleavages. A primitive form of this machine requiring close supervision was used in this country years ago, but output was small. The modern machines are generally air-pulsated Baum-type jigs, with capacities up to 150 tph, and treat sizes from 3/s in. to 0, usually previously dedusted or deslimed. These jigs are equipped with very accurate and sensitive automatic controls insuring satisfactory operation even at low separating gravity and with feeds irregular in quality and quantity. This paper will deal more particularly with coal cleaning separation, but the technical studies apply equally to all minerals.

Jul 1, 1955