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By John F. Wiss

A series of controlled experiments was conducted at four surface coal mines to study the effects of certain blast parameters upon the ground and air vibration. Preliminary scale-model blasts were conducted at a quarry to provide basic data. It was found that the amplitudes of the ground and air vibration were controlled by the maximum explosive weight per delay. Either cube root or square root scaling could be used for the seismic amplitudes, and cube root scaling could be used for the overpressure amplitudes. Both amplitudes were not significantly affected by the total charge weight per blast, the attitude of the boreholes, or the charge length or diameter. The overpressure amplitudes were affected by the charge depth, the use of cover over surface detonating cord, and the use of adequate stemming. The length of the delay intervals and the spacing of holes were important in determining the potential for reinforcement of the amplitudes in certain directions from the blasts. In downwind directions from the blast, the attenuation of the overpressure with distance decreases. Surface terrain did not significantly affect the overpressure amplitudes within the range investigated. The type of overburden affects the generation of both amplitudes and the propagation of the seismic amplitudes. Spectral analysis of the ground and air vibration is reported. A scaled distance of 300 ft/lb1/3 should produce a peak particle velocity of less than 1 ips and an overpressure of less than 128 dB linear peak. For square root scaling, a scaled distance of 75 ft/ lbl/2 should limit the ground vibration to less than 1 ips.

Jan 1, 1978

By G. Richards Gwinn

In modern warfare, mica is truly indispensable. Coordination of combatant units necessitates maintenance of intricate communications equipment, in the construction of which high-grade sheet mica is essential. Scrap, ground, and the poorer qualities of block mica, which are less essential to the military program, are not considered in this paper. Furthermore, as the paper is designed primarily to assist mica miners, mica derivatives, Such as splittings and films, also are excluded from discussion. The paper therefore relates solely to block mica of strategic quality. Understanding of t e many factor involved in marketing mica is definitely advantageous to mica, miners. The nature and detrimental effects

Jan 1, 1943

What is a nugget effect? In the early development of geostatistics, the term ?nugget effect? was coined for the apparent discontinuity at the beginning of many semivariogram graphs. This name was chosen to reflect the large differences found between neighbouring samples in ?nuggety? mineralizations such as Wits gold reefs. Geostatistical theory assumes that the difference between a sampled value and a potential repeat sample at the same location is actually zero. Included in this ?nugget effect? would be true variation between contiguous samples due to the nature of the mineralization, micro-fracturing, nugget or crystal size, and so on. Also included in the nugget effect would be any ?random? sampling variation which might occur due to the method in which the sample was taken, the adequacy of the sample size, the assaying process, etc. Arguments were put forward that ?sampling errors? actually exist at zero distance. Some geostatistical schools actually maintain that the ?nugget effect? is all sampling error. This would imply that ?perfect? sampling would eliminate the nugget effect entirely. There is now a dichotomy both in the geostatistical world and in the software packages provided for geostatistical analyses. It may seem academic to argue over whether the semivariogram model should take a value of zero, a value equal to the nugget effect, or a partial value at distance zero. However, the decision can have a profound effect on both the estimated resource and in our confidence on that resource. Whereas most geostatistical texts define the semivariogram model as taking the value of zero at zero distance, others imply that the full nugget effect should be used at zero distance. For example: ?The nugget effect refers to the nonzero intercept of the variogram and is an overall estimate of error caused by measurement inaccuracy and environmental variability occurring at fine enough scales to be unresolved by the sampling interval3 ?Christensen4 has shown that the ?nugget effect?, or non-zero variance at the origin of the sernivariogram, can be reproduced by a measurement error model ?The nugget effect is considered random noise and may represent short-scale variability, measurement error, sample rate, etc.5. In many training texts and Web courses, the definition of the semivariogram is ambiguous as the formulae for semivariogram models is not actually specified at zero distance6,7,8.

Jan 1, 2010

By H. Harzer

Statistics Canada record s indicate that in recent years 70 to 80% of the entire Canadian coal production originated from Western Canadian mines, in which about 55 to 65% of the coals are bituminous. Until recently, less than 20% of the latter were extracted by underground methods , the remainder being surface-mined. However, it is estimated that within the foreseeable future up to 80 or 90% will have to be gained by underground techniques. Although Western Canadian coal resources are considerable, they are unfortunately locked in severely distorted, steeply pitching and faulted seams of variable thickness. Consequently, their economic extraction poses serious engineering problems. One possible solution to the problems is to apply hydromechanical methods to underground mining. This is a well-proven method shown to be economically viable under Western Canadian conditions. This paper endeavours to widen the scope of published data on hydraulic coal mining and is based on practical engineering and cost data gathered through contacts with West German designers and operators of hydraulic mines.

Jan 1, 1978

By J. N. Geyer

During the early stages of the mining industry of the United States an apparently inexhaustible supply of high-quality, easily accessible coal made the product cheap and the attendant mining methods wasteful of recoverable coal. Because coal from advance places could be mined with less effort and a large outwit obtained as the entries advanced, much of the coal left in pillars to support the roof was lost. Squeezes often developed in these mined-over areas, or, if pillars were of sufficient size to-prevent squeeze, the roof would be so weakened by long exposure that any pillar recovery was extremely hazardous. As the value of unmined coal increased, a high recovery of the available coal became necessary. Numerous plans were tried during the period that followed, some of the methods proving successful while others were complete failures or only partly successful. As a better knowledge was pained of the roof strata and its behavior, however, pillar mining became more successful and methods suited to special roof conditions were developed.

Jan 1, 1933

By Scott Turner

The monetary metals , gold and silver , have recently been the object of such general interest that the United States Bureau of Mines has received many inquiries regarding them . Though requests for technologic information have been numerous , they have been exceeded in number by those concerned with economic aspects of these metals . The nature of the latter communications indicates that the public is not generally aware that various Bureau publications are available which deal with the economic situation of gold and silver . For this reason , it is deemed advisable to present a brief résumé of the papers which are obtainable from the Bureau or the Superintendent of Documents , together with the text of three articles recently prepared by the Director , reprints of which are not otherwise available . The Bureau of Mines compiles figures showing mine production of gold and silver , by districts and States , and cooperates with the Bureau of the Mint in determining the total annual output in the United States as a whole . 3 It recently established an annual canvass to determine the consumption of silver in the arts and industries of the United States , and published an economic paper covering such use in 1928 and 1929 , followed by an information circular on silver consumption by industry during the 2 years subsequent . A 4-year record is thus provided for those interested in utilization of silver . The Bureau has also published summarizations of all available data upon world production since 1493 of gold and of silver . It has , furthermore , rendered available a compilation of production- data of silver mines of the world , and an analysis of it , showing the proportions of silver and other metals contained in all the ores from which silver is derived . " All of these papers are concerned solely with putting into readily usable form statistical data and other factual material ; they do not offer theories or express opinions upon controversial questions related to these metals . Three other recent papers concerned with gold and silver are presented below in order to put them in shape for distribution by the United States Bureau of Mines . All three of them are by the Director of the Bureau . It should be noted that these papers do not commit

Jul 1, 1933

By AIME AIME

ANOTHER meeting of the Institute has passed into history and it fully sustained the reputation of the Institute as a live organization of the men, and nowadays the women, concerned with the mineral . ? industries and those working therein. The field meetings of, the 1nstitute are cine of its pleasantest and most valuable features. As Dr. Raymond used to say, ((It is good for a mining engineer once in a while to see a mine" and these meetings bring back to the mines those who, through progress into higher executive positions, have come to visit them infrequently, at the same time that they give opportunity for the .younger men to see regions and mines aside from those in which they are then working. This, and the formal and' informal interchange of information resulting,, is of the greatest professional value to all, while the meeting of old and making of new friends causes each meeting to be notable in turn. This year's meeting at Salt Lake City was one of the largest that has been held outside of. New York City; 470 members and guests registered while many more were present at the sessions without attending to this formality. '

Jan 1, 1925

By Whitman E. Brown

"As part of a Nation-wide program of the United States Government to develop natural resources, funds were made available to the Bureau of Mines for the investigation of the ""Reduction of Iron Ores by Solid and Gaseous Fuels."" These investigations are concerned with the direct production of iron from its ores without the use of a blast furnace. Many processes have been proposed for the low-temperature reduction of iron oxides, but few have been developed to commercial use. High-quality sponge iron is produced com-mercially only in Sweden.The cost of iron production depends in part on the grade of the ore and increases with decrease in grade. The substitution of cheap natural gas in a sponge-iron process for expensive coke in smelting in the blast fry pace would partly compensate for the use of low-grade ores. If a process can be developed in which inexpensive natural gas can be used as fuel and reducing agent, the large deposits of low-grade iron ore and the natural-gas resources of east Texas may be utilized in the commercial production of sponge iron.Sponge iron may possibly be used to supplement scrap iron, pig iron, or, in special instances, wrought iron. Sponge iron will vary but slightly in composition and will contain little or no nickel, cobalt, manganese, copper, and other allowying metals. It is becoming increasingly difficult to obtain choice scrap iron of nonalloy composition. Pig iron contains 1.5 to 3.0 percent silicon and 3.0 to 4.5 percent carbon. Sponge iron generally contains less carbon than pig iron.The Madaras Steel Corp. in Longview, Tex., built a set commercial-scale sponge-iron plant which was intended to be operated in connection with a steel foundry. The process is based upon the reduction of preheated iron ore, with hot reducing gases under pulsating pressure. Although the Madaras Corp. had previously experimented with the production of sponge iron by reducing the ore with pure hydrogen, several attempts to use a re-formed natural gas as the reducing agent in this pilot plant were unsuccessful. The Bureau of Mines leased this plant and conducted an extensive investigation of the Madaras process on a semicommercial scale.The experiments were not entirely satisfactory, partly because of mechanical difficulties and partly because the reducing gas was not of the best quality. However, much information on the production of reducing gas by re-forming natural gas and on the reduction of iron ore with re-formed natural gas was obtained.The sponge iron produced contained approximately 0.1 percent phosphorus; and, after melting in an electric furnace, the iron contained approximately 0.15 percent phosphorus. The results of attempts to improve the ore by ore-dressing methods were not encouraging."

Aug 1, 1946

By Gordon MacVean

THE adoption of rock dusting, as a safety measure, has made notable progress in the West Virginia coal mines since May, 1925. At that time there were but two mines in the State that were thoroughly rock dusted, mines No. 2 and No. 12 of the Boone County Coal Corp., at Sharpless. Since then it is probable that 75 per cent of the coal operators in the State have given consideration at one time or another to rock dusting. This growth of interest followed the meetings of the various mining institutes all over the country, during the summer of 1925, at which papers were presented, drawing the attention of the coal mining operators to the merits of this safety measure. Yet outside of the experience with rock dusting at the Old Ben Coal Corp., of Southern Illinois, and the Carbon Fuel Co., of Rains, Utah, there had been no actual occurrence in the coal mines of the United States, which could be taken as positive evidence of the efficacy of rock dusting in the prevention of the propagation of coal dust explosions. The U. S. Bureau of Mines, however, had run innumerable tests under conditions which closely approximated actual coal mining conditions and had clearly shown that rock dusting was effective.

Jan 1, 1926

By L. Andrews

Mineralogy, traditionally associated with concentrator studies, is being increasingly applied to problems in pyrometallurgy. Such investigations commonly make use of a number of techniques, and the results are combined for a meaningful interpretation, which can lead to a successful solution for the problem. Mineralogical techniques are described for various pyrometallurgical operations. Examples are given of studies and investigations involving mineralogy in chemical-looping combustion, feed monitoring to platinum-smelting furnaces, and losses to slag in base metal and platinum smelting.

Jan 1, 2011

By J. Philip Neal

Feldspar is no example of special mineralization in isolated spots: it can usually be found within a mile or so of almost anywhere. Along with silica sand, it is a major part of our world's total mineral composition. This fact imparts to it an economic status different from a sulfide ore, or potash, or phosphate. While every feldspathic "stringer" does not possess economic potential, the generous distribution does yield a high statistical frequency of good feldspar ore bodies: the adjective "good" being subject to some flexibility of interpretation. The strong chemical bonds of this alkali aluminum silicate give it certain use advantages, but under present technology its individual elements cannot practically be separated to create aluminum, potassium, sodium, silicon - or their oxides. Its present uses rely upon chemical inertness - as in fillers; and on its physical melting characteristics and their effect in glass, enamel, or ceramics.

Jan 1, 1973

By T. A. Muhlare

The use of electrolyte additives to smoothen cathode deposits during copper deposition is practised worldwide. These additives absorb on the cathode surface and take part in the electrochemical crystallization process. However, these additives also affect the quality of the cathodes when they are inadequately controlled. Electrolyte additives used by Palabora are glue, thiourea, Avitone and chloride. Their effects were determined on cathode quality, the size of the current density region that gives the desired compact morphology, and current efficiency. This was done in a small-scale cell. Small cells have different hydrodynamics from industrial-scale cells, which makes it difficult to simulate the operation of industrial cells in a laboratory. The approach used here was to use a rotating cylinder cathode to attain controlled hydrodynamics. The rotation speed was chosen to give a diffusion layer thickness that is similar to that of an industrial-scale cell. It was shown that even fairly small changes in the additive levels can significantly affect the cathode morphology, and the current density range over which this morphology can be obtained. Keywords Copper, electrorefining, glue, thiourea, avitone and chloride.

Jan 1, 2011

By D P. Blair

There are two major aspects to wall control blasting – the potential for any blasthole to cause wall damage and the potential for a delayed sequence of blastholes to cause damage. The damage potential of individual blastholes is governed by standoff distance and charge weight. However, for locations sufficiently close to a highwall, dynamic finite element models and field measurements show that there is also a critical nature to those blastholes very close to the wall, over and above standoff distance. At many mine sites, the charge weight/standoff-distance is set by trial and error. Thus, a significant aspect of the present work is the determination of dynamic stress radiating from a blasthole. Unfortunately, the modelling and measurement of this dynamic stress is still faced with many difficulties. Typical models have questionable aspects, which casts serious doubt over their predictions, and it is shown that the Hustrulid Bar experimental technique does not correctly account for stress wave attenuation in extended media. In an attempt to solve the dynamic stress problem, the present work describes a model based on an exact solution under the assumption of viscoelastic material. The model takes full account of the rock mass elastic/viscoelastic properties, the explosive type, geometry and primer location and predicts a dynamic stress for direct comparison with the unconfined compressive strength of the local rock mass. This model predicts the standoff distance required to avoid damage due to a single blasthole. The behaviour of a delayed sequence of blastholes is analysed using an upgraded waveform superposition model, covering a range of initiation delay combinations, which predicts the peak particle motion (PPM) induced in the wall for each combination. This approach shows that there is no need to fire dedicated trim shots close to walls; all that is required is a carefully modified production shot. The mechanism of vibration screening is discussed, and its use in a superposition model highlights the potential of reverse firing (shield blasting) to reduce wall PPM. A conceptual model is also introduced to give a further insight to vibration screening and damage (via ground heave). This model predicts that a centre-lift blast will have a central heave profile and that a reverse-fired shot will produce a smaller power trough than that produced by a standard shot. It is demonstrated that the mechanism of presplit formation is not well understood; nevertheless, experimental evidence shows that presplits can be an effective method for reducing wall vibrations.CITATION:Blair, D P, 2015. Wall control blasting, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 13–26 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By V. F. Parry

[Approximately 7-1/2 million tons of subbituminous coals are mined annually in Colorado, Wyoming, and Montana, of which 50 percent probably reaches domestic consumers. The moisture of these subbituminous coals is high, averaging about 25 percent when they are mined. The coals are non-caking end stack to a variable degree when exposed to normal atmospheric conditions. They are good domestic fuels, are considered to be smokeless in most furnaces, and have been used for many years in hand-fired domestic furnaces in which the practice is to employ large lutes for efficient combustion.]

Jan 1, 1941

By Harold M. Smith

This publication summarizes the literature on the composition of petroleum, with special emphasis on naphtha and gas oil, and provides a source book for the known qualitative and quantitative facts on crude oil composition. The discussion points out the known facts from supposition, and suggests new researches needed in various areas.

Jan 1, 1968

The design, specification, and performance evaluation of the Communications and Location portions of a Coal Mine Rescue and Survival System are described. The work was performed as part of a nine month effort to develop a mine rescue and survival system using existing technology and state -of-the -art hardware as recommended by the National Academy of Engineering. Three basic subsystems were developed, one for survival, one for communications/location and one for rescue. This report and related equipment manuals describe only the Communications/ Location Subsystem which was designed, fabricated, and tested by the Westinghouse Georesearch Laboratory in Boulder, Colorado. Two basic technologies were used. Electromagnetic signals propagating through-the-earth provide voice downlink and coded beacon up-link communications. Seismic methods were developed to provide means for locating trapped miners. Seismic signalling also provides a backup means for communications. Parallel development programs for the electromagnetic and seismic portions of the system were conducted. The resulting hardware and software have been partially tested in coal mines and under simulated emergency conditions in order to evaluate system performance. The results of these tests are discussed. Further testing is recommended in order to establish quantitative performance limitations tinder a variety of environmental conditions and to develop methods for improving system performance.

Jan 1, 1971

By John J. Mulligan

The Bureau of Mines investigated the tin deposits of the Cape Mountain area during July and August 1962 to test the effectiveness of detrital-cover sampling in permafrost areas as a relatively cheap and simple means of guiding mine development and exploration. Results indicate that systematic detrita1-cover sampling can be used effectively to delineate obscure deposits with sufficient accuracy to permit sampling with a minimum of trenching or drilling. Extensions of known outcroppings were traced in sufficient detail to guide lode sampling and several previously unknown tin-bearing lodes were found and sampled. Lode sampling was limited to the minimum needed to establish the reliability of detrital-cover sampling results. The results of previous lode and placer investigations are summarized and detrital-cover sampling methods and results are described in detail.

Jan 1, 1966

By H. A. Oliveira, A. Azevedo

Physical and chemical characterization and solid/liquid separation of turbid waters from a river affected by an iron tailing rupture disaster (Gualaxo do Norte River, Brazil) were studied at bench scale. Parameters such as turbidity, pH, surface tension, electrical conductivity, total suspended solids (TSS), particle size distribution (micro- and nanoparticles), and zeta potential were analyzed from samples collected at three different river depths. The results in all samples showed the presence of micro- and nanoparticles, ranging in diameters from 100 nm to 200 μm. Best results for flocculation and settling were obtained at pH 7.5, through an innovative combination of eco-friendly reagents: (i) ferric hydroxide precipitates (10 mg L−1 Fe3+) to sweep (enmesh) the dispersed solids and (ii) gelatinized starch (5 mg L−1 ) to form large flocs. The results showed removals between 90 and 100% of total suspended solids (micro- and nanoparticles), resulting in clear water with residual turbidity < 7 NTU. It is believed that this innovative alternative has a high potential for flocculating and treating the turbid water at Gualaxo do Norte River, assisting the water treatment stations.

By H. A. Oliveira, A. Azevedo

Physical and chemical characterization and solid/liquid separation of turbid waters from a river affected by an iron tailing rupture disaster (Gualaxo do Norte River, Brazil) were studied at bench scale. Parameters such as turbidity, pH, surface tension, electrical conductivity, total suspended solids (TSS), particle size distribution (micro- and nanoparticles), and zeta potential were analyzed from samples collected at three different river depths. The results in all samples showed the presence of micro- and nanoparticles, ranging in diameters from 100 nm to 200 μm. Best results for flocculation and settling were obtained at pH 7.5, through an innovative combination of eco-friendly reagents: (i) ferric hydroxide precipitates (10 mg L−1 Fe3+) to sweep (enmesh) the dispersed solids and (ii) gelatinized starch (5 mg L−1 ) to form large flocs. The results showed removals between 90 and 100% of total suspended solids (micro- and nanoparticles), resulting in clear water with residual turbidity < 7 NTU. It is believed that this innovative alternative has a high potential for flocculating and treating the turbid water at Gualaxo do Norte River, assisting the water treatment stations.

Auger operations produced 14 million tons of coal in 1974, or approximately 5% of all surface mined coal. It was the most efficient of all coal mining methods, producing 40.0 tons per man-day. Exhibit 1.1 gives a breakdown of productivity of all coal mining methods. Exhibit 161 PRODUCTIVITY OF COAL MINING METHODS (Short tons per man-day) [Method - 1971 1972 1973 1974 Conventional 11.00 10.00 9.75 9.30 Continuous 13.00 12.50 12.25 11.90 Strip Mines 35.69 35.95 36.00 36.00 Auger Mines 39.00 43.00 45.33 40.00 ] Unlike other surface mining methods, augering produces clean coal, largely uncontaminated by foreign materials, other than those existing in the coal seam itself. However, compared to other methods, the coal recovery rate is relatively low. For example, a triple-headed auger in a 35-inch seam would recover approximately 50% of the coal in the seam as compared to a 90 to 95% recovery rate for strip mining and a 55 to 65% recovery rate for deep-mining. The low auger recovery rate is due to the circular cuts and pillars left in the seam.

Jan 1, 1975