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By Mikko Ahola

This paper describes recent innovative analyses conducted by the Bureau of Mines to demonstrate the application of the boundary-element method in evaluating the effectiveness of caving chambers or sacrificial entries to relieve the stress conditions initiating cutter roof failure in underground coal mines. The analysis assumes that cutter roof failure results when the shear strength of the roof rock at an entry corner is exceeded by the applied shear stress. The applied shear stress is due to large differences between the horizontal and vertical in situ stresses known to exist in many coal mining districts experiencing cutter roof failure. The results of boundary-element analysis suggest that driving an arched lead entry in advance of adjacent rectangular entries and allowing it to cave significantly reduces the difference between the principal stresses at the corner of the rectangular entry, thereby lowering the maximum shear stress. Slippage of the immediate roof along horizontal bedding planes into the caved entry is shown to further reduce the stress conditions in adjacent entries. Practical applications of this stress control technique to longwall and room-and-pillar mining are discussed.

Jan 1, 1987

By C. B. Manula

In this report, the application of the Open Pit Materials Handling Simulator (OPMHS) to a Southwestern surface mine using draglines and front-end loaders is described. The specific objective of the study is to demonstrate the application of the simulator to analyze mine planning and to analyze alternatives for increased production. The simulator was verified by comparing long term production figures to the simulated results from data collected on a mine visit. A short term and a long term alternative are studied with projected productivities and scheduling. No economic analysis of these proposals were performed.

Jan 1, 1977

By A. Romero, M. Carvalho, D. L. Millar

"The number of underground mines replacing diesel by battery powered mobile equipment is growing worldwide. The latter produces locally zero emissions and less heat, improving air quality in the working areas, and can potentially reduce energy costs due to lower ventilation requirements and in the face of higher fuel prices. However, there is a lack of systematic approaches to evaluate the potential economic benefit of switching from diesel mobile technologies to electric ones. This paper presents a method to answer the question of whether a mine with known operating conditions should invest in battery-powered electric equipment to reduce its total costs. Furthermore, this method provides the optimal number of electric and diesel equipment in relationship with their impact on the ventilation system and the total costs of running the mine from the energy perspective. A case study of an underground mine in Northern Ontario (Canada) is presented to validate the method proposed. The scenarios studied include the specific climatic conditions of the region, and the possibility to use heat recovery for the ventilation system. Overall, results show that the use of electric mobile plants is cost competitive, especially so when electricity cost can be lowered through load-shedding strategies.INTRODUCTIONOf the multiple advantages of using electrical vehicles (EV) underground in mining, the potential increase in air quality and comfort is the most significant (Paraszczak, Svedlund, Fytas, and Laflamme, 2014). Until recently, fully battery-powered electrical underground heavy duty machinery (i.e., loaders or trucks) were not available, so that tethered and trolley assisted vehicles were the only electric alternatives to diesel powered vehicles (Bétournay et al., 2011). Today, several commercial battery-based alternatives are available (General Electric Fairchild, 2015; RDH Mining Equipment, 2015; Paraszczak et al., 2014). Operational details can be found in Ewing (2015). The main battery technology used (Lithium Iron Phosphate, LiFePO4, or LFP) was already anticipated in Bétournay et al. (2011) as a good candidate for these types of vehicles. More details on these batteries, along with state of the art and future perspectives can be found in Zubi, Dufo-López, Carvalho, and Pasaoglu, (2018)."

Jan 1, 2019

By Joseph W. Leonard, T. S. Spicer

INTRODUCTION Reasons for Thermal Drying The continuing increase in the percentage of minus %-inch coal produced as a result of the increased use of mechanical mining methods has, over the years, tended to shift considerable portions of the work of producing saleable coal to the fine coal cleaning section of the preparation plant. Because a given weight of fine coal will contain substantially greater surface area than an equivalent weight of coarse coal, it follows that, when subjected to wet cleaning processes, the fines will absorb and retain consider- ably more moisture than coarser fractions. Increased moisture pickup in the finer sizes complicates fine coal cleaning since beneficiation may not be limited to the removal of ash and sulfur but often must be expanded to include the additional step of thermal drying to remove excessive moisture. Thus, water which provides the medium for cleaning fine coal is in itself detrimental and, like ash and sulfur, reduces coal quality. Removal of surface moisture by drying is done for one or more of the following 1 reasons: (1) To avoid freezing difficulties and to facilitate handling during shipment, storage and transfer to the points of use; (2) to maintain high pulverizer capacity; (3) to reduce heat loss due to evaporation of surface moisture from the coal in the burning process, thus increasing heating efficiency; (4) to improve the quality of coal used for special purposes, such as in the production of coke, briquettes, and chemicals; (5) to decrease transportation costs; and (6) to facilitate dry coal-cleaning processes. Because benefits to coal transportation and utilization are the most common reasons for thermal drying, the following sections will examine these areas in greater detail. Benefits to Transportation Initial benefits from drying are the reduction of shipping costs from the mine to the point of utilization since more coal can be concentrated into a given weight of product when worthless moisture is removed. Non- combustible~ such as water and mineral matter in railroad shipments of coal are billed the same as coal at $3.32 per ton, according to the recent average costs. Savings of 10 to 20 dollars from drying on the shipment cost of each 50 to 60 tons of coal contained in a typical railroad car is common. Savings on coal shipments from individual mines which result from coal drying can be expressed in terms of hundreds of thousands of dollars and more each year. For example, a reduction of shipping charges of only 5 percent on one million tons per year would mean a savings of 166,000

Jan 1, 1968

By Harvey S. Mudd

WHEN talking about Europe it is well to endeavor to keep politics and economics apart but they have become so intermingled in recent years that the discussion of one topic inevitably leads to the other. Economic influences formerly prevailed over politics but today national and international economies are governed by political forces. Commerce in raw materials, food, and manufactured products is now so restricted by governmental controls that the capacity of the world to produce and to consume, to exchange goods and to pay for them, cannot be gauged by the past or predicted by a multitude of experts. In prewar days there were some yardsticks but today there are none. Thus it is hazardous to make forecasts, for in all fields of human effort the world has been cast upon an uncharted sea.

Jan 1, 1947

By H. A. Coy, James A. Noble

The Mascot mines of the American Zinc Co. of Tennessee are situated at Mascot, Tenn., 14 miles northeast of Knoxville, on the Southern Railway. The district is centrally located in the Great Valley, or Appalachian Valley Province. Prior to 1900, a small output of zinc was obtained from oxidized ore mined in open pits. In 1900, a shaft was sunk to sulfide ore, and in 1903, a second shaft was put down, neither being as deep as 200 ft. The American Zinc Co. of Tennessee began drilling in 1911, and outlined an ore-body to which its No. 1 shaft was sunk, to a depth of 365 ft. Since that time, the American Zinc Co. of Tennessee has been the only operator in the district. The Federal mining laws have never been in operation in Tennessee and mining lands are as irregular in boundary and area as farm lands. Ownerships are generally held in fee. In most cases the surface and mineral rights are transferred together. Electric power is supplied at 66,000 volts by the Tennessee Power Co., from a hydro-electric plant at Parksville, Polk County, Tenn., 100 miles from Mascot. No other power is used, but an emergency steam plant is held ready in case of interruption of service. Labor is all native and non-union. Negroes are employed for most of the shoveling, and for a few miscellaneous jobs, but for almost no other work. Exploration Exploration is carried ahead of mining largely by surface drilling. Both churn and diamond drills are used. Holes are not spotted according to geometric plan, but to block out ore outlines with the least number of holes. Churn-drill cuttings from each 5-ft. run are mounted for formation record, and in ore ground, all the bailings from each 3 ft. of advance are sampled and assayed. Diamond-drill cores are sampled and a specimen core filed for formation record. In ore ground, all the core

Jan 1, 1925

By Wm. R. Webster

This is a contribution for the proposed new discussion on the physics of steel. The former discussion on the subject started with the consideration of five papers presented at the Chicago meeting in 1893, and continued for several years. The Suggested Lines of Discussion, prepared by Doctor Howe, covered a wide field and added greatly to the success of the work. Naturally, the first step in a new discussion will be to remodel and bring up to date the old Suggested Lines of Discussion so as to embody all the important advances in the metallurgy of steel that have a bearing on the physics of steel and keep the papers and discussions within the field of work undertaken. This paper will be devoted to the practical application, in rolling steel, of the effects of carbon, phosphorus, and manganese on its tensile strength, with some suggestions on further research work. Dr. J. E. Stead, in his paper Influence of Some Elements on the Mechanical Properties of Steel,' gave a complete review of all that had been done during the past thirty years. He gave full credit to all investigators who worked on these lines, also their results, with his views on same, and in many cases his own results. All of this data and much new valuable information were put in convenient shape for reference and study. To do this required a great deal of work, which is fully appreciated by the steel manufacturers and investigators. The variations in the values given by the different investigators for the increase of the tensile strength of steel for each 0.01 per cent. of carbon, phosphorus, and manganese were largely due to the steels they worked on, the large or small variations in the amount of the elcments present, and the omission to take into consideration all the factors, from the blast furnace through to finished rolled material, that affect the character of the steel. For instance, a poorly made dirty steel requires considerably more carbon to give the same ultimate strength than a well-made clean steel with the same phosphorus and manganese content.

Jan 1, 1922

By Wm. R. Webster

This is a contribution for the proposed new discussion on the physics of steel. The former discussion on the subject started with the consideration of five papers presented at the Chicago meeting in 1893, and continued for several years. The Suggested Lines of Discussion, prepared by Doctor Howe, covered a wide field and added greatly to the success of the work. Naturally, the first step in a new discussion will be to remodel and bring up to date the old Suggested Lines of Discussion so as to embody all the important advances in the metallurgy of steel that have a bearing on the physics of steel and keep the papers and discussions within the field of work undertaken. This paper will be devoted to the practical application, in rolling steel, of the effects of carbon, phosphorus, and manganese on its tensile strength, with some suggestions on further research work. Dr. J. E. Stead, in his paper Influence of Some Elements on the Mechanical Properties of Steel,' gave a complete review of all that had been done during the past thirty years. He gave full credit to all investigators who worked on these lines, also their results, with his views on same, and in many cases his own results. All of this data and much new valuable information were put in convenient shape for reference and study. To do this required a great deal of work, which is fully appreciated by the steel manufacturers and investigators. The variations in the values given by the different investigators for the increase of the tensile strength of steel for each 0.01 per cent. of carbon, phosphorus, and manganese were largely due to the steels they worked on, the large or small variations in the amount of the elcments present, and the omission to take into consideration all the factors, from the blast furnace through to finished rolled material, that affect the character of the steel. For instance, a poorly made dirty steel requires considerably more carbon to give the same ultimate strength than a well-made clean steel with the same phosphorus and manganese content.

Jan 1, 1922

By Richard Crowell, James Gillaspie

A concentrate biooxidation process was successfully demon­strated in the field in a remote part of northwestern Mexico. A 275 tonne (300 st) biooxidation heap was constructed using GeoBiotics' proprietary GEOCOAT™ coated concentrate process. The pyrite/chalcopyrite/sphalerite concentrate was bioox­idized in the heap for 60 days. Cyanide leach recovery of the con­centrate increased from 68% gold recovery at a cyanide consump­tion of 1.6 kg NaCN/g Au (llO lbs/oz) in the as-received concen­trate, to 94% gold recovery at a cyanide consumption of 0.37 kg NaCN/g Au (27 lbs/oz) in the biooxidized concentrate. The heap was constructed at a rate of7 tonnes (7.5 st) concentrate per hour, using typical heap leach equipment and easily scalable methods. Heap operations demonstrated that energy dissipation in the humid summer environment was easily controlled by low pressure aeration and management of solution chemistry and application. Observations of the demonstration heap appear to support the presence of reflux of moisture within the biooxidation heap.

Jan 1, 1998

By Animesh Jha, Catherine Davey

"Carbothermic reduction and nitridation reactions using synthetic kaolinite mineral were investigated for the formation of silicon based nitrogen ceramics. The temperature dependence of the reaction rate and its effect on phases formed are reported. The effect of the reactivity of carbon on the kinetics of formation of AIN and ShN4 is discussed. Using the standard Gibbs free energy values for the formation of nitrides and oxides of aluminium and silicon, a log po2 verses I/T diagram is constructed. The experimental data results are discussed and compared with the predicted phase equilibria. We also report the influence of sub-oxide gaseous species on the microstructure of the ceramic phases produced.IntroductionSynthetic kaolinite is a clay containing alumina, silica and water of crystallisation, and has a chemical formula 3(Al2O 3.2SiO2.2H2O). This mineral is relatively inexpensive and, is therefore an ideal candidate for use in the production of ceramic powder mixtures for example silicon nitride and aluminium nitride for composite material formation, When the mineral is heated, the water of crystallisation from the crystal lattice is lost via the 3(Al2O 3.2SiO2.2H2O) = 3(Al2O3.2SiO2) + 6H2O reaction. It has been shown [1·2j that on further heating to 1673K, the anhydrous kaolinite decomposes to a mixture of mulllte and silica, 3(Al2O3.2SiO2) = 3Al2O 3.2SiO2 + 4SiO2 which is consistent with the alumina-silica phase diagram, shown in figure 1.The binary alumina-silica phase diagram has a well-defined sub-eutectic immiscibility dome and this characteristic dernixing behaviour is reflected in the thermal decomposition of anhydrous kaolinite consequently the microstructural features resemble the spinodal decomposition process. It is well established that the spinodal decomposition process raises the nucleation frequency due to their low free energy barrier, (?G). The small magnitude of this barrier consequently promotes the evolution of a very fine microstructure. The process of spinodal decomposition is therefore expected to be influential during the reduction-nitridation of kaolinite minerals."

Jan 1, 1996

ABSTRACT' The first references to gold in New Guinea were by the Portuguese in 1525. The first significant discovery and gold rush was on Sudest Island in 1888 and was a natural extension of the rush that surged up Australia's eastern coast and ended at cook- town. Prospectors made a series of minor discoveries in coastal regions before the first large discovery at Wau/Edie Creek/Bulolo in 1925. Major post war gold discoveries were made at Bougainville, Frieda River, Porgera and Ok Tedi. On Misima Island a large bulk low grade deposit has been recognised surrounding old gold workings. Gold exploration has increased drama- tically since the lifting of a 3 year moritorium on new exploration areas in Noverrber 1982. A new bulk low grade gold discovery has been made on Lihir Island, north of Bougainville and a number of other promising areas are being drilled. Gold production is also expanding dramatically from current levels of 600,000 ounces to an anticipated 1.3 million ounces in 1985 with the opening of Ok Tedi. Other potential developments are likely to increase output above 2 million ounces by 1990. Papua New Guinea's world ranking as a producer is likely to move from 9th to 7th in 1985 reflecting the favourable geological potential, stable political environment and attractive development terms offered by the Government.

Jan 1, 1984

By Desmond M. Connor

"The State of the EnvironmentRecent data from a State of the Environment report prepared in January 1991 and released in April (see references) , indicates that the physical and biological environment across Canada is deteriorating in some important ways. For example: • emissions and atmospheric levels of CO2 are rising at a rate more than 50% of the U.S. increase; global temperature continues to rise, especially during the last decade;• while S02 emissions have been falling since 1984, NOz has declined only slightly since that time; N02 in Canada rose 43% during 1970-87, compared with a 7% rise in the U.S.;• municipal discharges of phosphorus and BOD (biochemical oxygen demand) to fresh water have been rising steadily since 1983);• pulp and paper mill discharges to fresh and Pacific coastal waters have been rising, 1970-87;• migratory game bird populations (Prairie Mallard, Northern Pintail) have been declining for the last 20 years;• total per capita energy use continues to climb.The State of the PublicSimilarly, data from recent public opinion surveys shows that public concerns about the environment are either rising, or are remaining at a high level despite the competing claims of the economy and political events for attention.For example, Professor Reginald Bibby's national survey this year shows that Canadians rank our top three issues as theeconomy, the environment and government incompetence.An Angus Reid survey commissioned by the Mining Association of Canada and other mining organizations in 1989 showsthat, despite general support for its economic benefits:• 67% of the general public perceive the mining industry to be a major source of pollution and environmental contamination;• 68% believe that a new mine should not be developed if it will disturb local wildlife;• 52% would prohibit a new mine if it required a road through a national park;• 49% would disallow mine development if it took as much land as an average farm in an agricultural area or if it limited sports fishing in a local lake."

Jan 1, 1991

By Nicasio del Castillo

INTRODUCTION The tax structure of foreign mining investment into the United States has a significant impact on the financing and the profitability of the operation. For these reasons, it is critical for the foreign investor to develop and implement a well planned tax strategy that will enable its venture to: (1) reduce its U.S. income tax liability (2) lower U.S. withholding taxes when funds are transferred from the United States, and (3) decrease or defer home country taxation on its U.S. earnings ALTERNATIVE FORMS OF INVESTMENT A threshold business and tax consideration is the form in which the investment is to be made. The most common alternatives include: forming or acquiring a U.S. mining corporation, directly establishing a branch mining operation, or entering into a joint venture or partnership with a U.S. mining company. U.S. Corporations The most common structure through which foreign mining companies engage in business in the United States is to form a U.S. mining corporation. Forming a U.S. Corporation. If the investor decides to establish a new U.S. corporation the organization is relatively simple. No distinctions are made in the United States between "public" and "private" forms of incorporation. Minimum share capital is not usually required and share capital may consist of shares with no par value. Since corporate law is the responsibility of the individual states, the foreign investor must choose a state in which to incorporate. If appreciated mining property is transferred to a corporation solely in exchange for stock or securities in that corporation, and the transferors have control of the corporation (defined as at least 80 percent of all voting shares and at least 80 percent of all other shares) immediately after the exchange, no gain or loss will be recognized. However, if the transferors receive cash or other mining properties in addition to stock, any resulting gain may, in certain situations, be taxed to the extent of the cash and the fair market value of other property received. Acquiring an Existing U.S. Corporation. Acquiring an existing U.S. mining corporation is not as straight-forward as forming a corporation. This alternative may be accomplished through either a stock or an asset acquisition. Generally, with a stock acquisition the purchaser inherits all of the business and tax attributes of the former mining corporation. If the investor is able to acquire mining assets, however, the purchaser will usually be able to avoid any unknown or hidden liabilities that could be attached to an existing corporation. Another principal advantage in acquiring assets is that the purchase price may be directly allocated to the acquired mines or other mineral-related assets with the result that the assets' depreciable base may be increased. Assuming the domestic seller and the foreign purchaser can agree, it is generally advisable to allocate the purchase price in the sales agreement to specific individual assets. From the foreign investor's standpoint, it is preferable to allocate the purchase price to depreciable assets such as buildings and equipment versus an allocation to mineral land holdings or intangibles such as goodwill, which are generally not depreciable. It is not uncommon, however, for a seller mining company being acquired to insist for tax reasons that the investor purchase shares rather than assets. If the foreign

Jan 1, 1985

By C. S. Sivil

To modern civilization the platinum metals are of inestimable value. Their distinctive properties, both physical and chemical, render them indispensable in an age in which the processes of the laboratory are becoming an essential part of the daily life of the world. Generally, their function, though vital to particular processes, is not spectacular, and so remains unknown to all except the operators. EARLY METHODS OF MANUFACTURE The properties of platinum were recognized as of prime importance for scientific work at. a very early date, probably between 1750 and 1760. The difficulty of making articles from it seemed almost insurmountable, because no means of attaining the temperature necessary to melt it were known at that time. It is true that solid platinum could be obtained by fusing the metal with a more volatile metal such as arsenic, which was subsequently driven off by baking, but such a method, at its best, would give only a very brittle product, which was totally unsuitable for the purposes for which it was intended. Little, if any, progress could be made until it was discovered that platinum sponge, heated to white heat and hammered in an iron or clay mold, would metallize and retain the shape of the mold. This was a process that could not be wholly satisfactory but from it developed the method of pressing the sponge in a mold and forging it at white heat into wire or sheet. At present a somewhat similar process must be used for fabricating articles of tungsten, molybdenum and other metals of high fusing point, as with these metals we face today the same problems that the scientists of the eighteenth century encountered with platinum, but possibly the next significant advance in the metallurgy of these metals will be the devising of means to melt and cast them.

Jan 1, 1931

By R. E. Reed, C. J. McHargue

Single crystals of aluminurn were reduced 90 pct in diameter by extrusion at 296" and 77°K. The resultant double fiber texture had a strong (111) component with a weak (001) component. The relative anzounts of these components varied with starting orientation. Decreasing the Lemperatuve of defovtnation increased the amount of (001) texture component in crystals with inilia1 orientations near (111). The starting orientation and temperature of deformation strongly affected the morphology of the (001) component. The effects of orientation and Lemperatuve upon the distribution of the (001 ) texture component in extruded aluminum single crystals were rationalized on the basis of deformation band formation and interaction. MANY papers since the early 1920s have discussed the occurrence of the double fiber texture (111) + (001) in wires and rods of deformed fcc metals. Aside from the reporting of experimental results for the various metals under a variety of fabrication conditions, emphasis has been placed on two related problems. One problem deals with the prediction of ideal end orientations based on the glide systems and flow directions. The other problem seeks the reason why different amounts of each component may be produced by the same fabrication schedule for metals apparently having the same deformation systems. Some of the difficulties in developing a satisfactory explanation have their origin in the experiments themselves. One mistake has often been the assumption of an initially randomly oriented specimen or complete ignorance of effects of starting orientation. Recent studies by Grewen and Wassermann,1 Cullity and co-workers,2' and McHargue4 have shown that the initial orientation may be the most important factor in determining the final orientation. Hence only limited comparisons of data from different studies can be made unless all conditions of the initial material are specified. Another question has been the nature of the (001) component. Hibbards suggested that any (001) present was the result of re crystallization during fabrication. Although Fleischer6 found no (001) texture in aluminum swaged at room temperature, and Dayal 7 found that component to disappear at very high reductions, a double fiber texture has usually been reported for aluminum. Vandermeer and McHargue showed that, while some (001) in aluminum may be the result of recrystallization, much of this component has its origin in the deformation process. Ahlborn and Wassermanng found the (001) component in silver deformed at low temperature not to be the product of recrystallization.

Jan 1, 1968

By L. D. Jaffe, F. W. Cotter, E. Cordon

The hardenability of titanium-base alloys was studied by metallographic examination and hardness survey of Jominy specimens end-quenched from the B range. Analyses of the data led to the equation log J = -0.57 + 0.25 @ct Fe + pct Mn + pct Mo) + 0.19 @ct Cr) +0.16 @ct V) + 0.03 @ct Zr). Here J is the distance, in sixteenths of an inch, from the quenched end of a Jominy hardenability specimen in the position of peak hardness, for material quenched from the B range. This equation fitted the experimental data with a standard deviation of approximately 0.29. The effects of the elements Al, Sn, W, Cu, Ni, B, C, N, 0, and H, and of pain size, were not statistically significant or not practically significant. A check against hardenability measurements in the literature showed agreement within the stated standard deviation. The equation should be useful in estimating hardenability of new or modified titanium alloys. HARDENABILITY in a titanium-base alloy is the ability of the alloy to retain the B structure on quenching. An alloy with high hardenability will retain the /3 structure even when cooled relatively slowly from a temperature at which B or P plus a is stable. A low hardenability material will retain P only if quenched extremely rapidly from the range of p or 0-plus-a stability, or will not retain it at all, at room temperature. High hardenability is desirable in titanium alloys to be heat-treated to high-strength levels. Its value is by no means limited to large section sizes. With high hardenability, a material can be solution-treated and cooled at a variety of rates, either to give high strength directly or, more generally, to give a soft ductile condition from which high strength can be obtained by subsequent aging. With low hardenability, high strength can be obtained, if at all, only by very rapid quenching, and there will generally be little increase in hardness on subsequent aging; an alloy of this type is limited in its applicability. On the other hand, alloys of very low hardenability have some advantages in weldability; essentially, they are always in the annealed condition, after welding as well as before. For commercial alloys, hardenability data are usually available, in the form either of property data after cooling from the solution temperature at various rates, with or without subsequent aging, or of results of a standard hardenability test, such as that originally developed for steels by Jominy and Boegehold.' When modifications of an available alloy are considered, or preparation of new alloy compositions, it would be Very convenient to be able to estimate the hardenability of the new material without having to make and test it. A method of estimating hardenability of titanium alloys from their composition was suggested by one of the authors some time ago, on a preliminary basis, utilizing scattered data found in the literature.' It seemed worthwhile to carry out a systematic experimental study of the effect of composition upon hardenability. EXPERIMENTAL PROCEDURE Approximately fifty heats of various compositions, weighing 8 to 10 Ib apiece, were melted in a small inert-gas tungsten-arc furnace with water-cooled copper walls. The starting material was 110 Brine11 titanium sponge, with high-purity metals added for alloying. Each heat was bottom-poured under vacuum through a molybdenum burnout strip into a cold graphite mold, to form an ingot approximately 4-1/2 by 3-1/2 by 3 in.* From each ingot were cut *The material was melted and cast by Pitman-Dunn Laboratory, Frankford Arsenal, to whom the authors must express their thanks. two pieces 4-1/2 by 1-1/2 by 1-1/2 in. These were forged, at temperatures adjusted to the composition, into 1-1/4-in. rounds, from which standard 1-in.-diam hardenability specimens3 were machined. A number of small samples were also prepared from forged materials of each heat, annealed, quenched from various temperatures, and examined metallographically. The P-transus temperature was determined by observation of the degree of resolution of primary a in these pieces. samples for chemical analyses were also taken from the forgings. One hardenability specimen of each heat was solution-treated for 1 hr approximately 50°F above the measured transus temperature, and the other for 1 hr approximately 250°F above the transus. (An additional hour was allowed for the specimens to reach furnace temperature.) These are not necessarily the temperatures that would be selected for

Jan 1, 1964

By M. E. Kuchta

Research is currently being conducted at the Colorado School of Mines in the use of high-pressure water for scaling down loose rocks in underground mine openings. In addition to improved miner safety, the adhesion strength of shotcrete applied to rock surfaces treated with high-pressure water is also increased significantly, resulting in improved overall support capabilities of the shotcrete layer. Test results show an increase in adhesion strength by a factor of four on a concrete test wall cleaned with water at 21 MPa (3,000 psi) as compared to a surface cleaned at 0.7 MPa (100 psi).

Jan 1, 2003

The Lake Rotokaua sulphur deposit, near Taupo, New Zealand, is a lacustrine sedimentary ore body, 220 acres in area and from 7 ft to 96 ft thick, containing, within the area drilled to date, some 20 million long tons of ore averaging 25% elemental sulphur in unconsolidated tuffaceous diatomaceous clay, overlain by about 120 ft of pumice sand and by the shallow Lake Rotokaua. An additional amount of perhaps 4 million tons of sulphur is regarded as probable in the area remaining to be drilled. Current economic studies cover the problems of mining an unconsolidated water-saturated formation with some residual thermal activity nearby; conservation and restoration after mining in a scenic recreation area; beneficiation of the ore and extraction of high- purity sulphur, principally for fertilizer manufacture. The deposit has additional importance as a pointer to possible further discoveries in the Thermal Region.\

Jan 1, 1971

By B. J. Cunliffe

"Filter cloth in the mining industry is an ambiguous title asthis suggests filter cloth use from underground ventilation to the refining processes. The time allowed for this paper would be better served in con-centrating on vacuum filters common to all mine mills and to offer some simple guide lines to the mill metallurgists in the choice of filter cloth for this type of filter.The requirement of the filter cloth is to separate solids from liquids under a vacuum head by forming a permeable layer of solids or cake, through which liquids can flow until the panel or disc sector leave the slurry tank and to continue to pass residual moisture from the cake formed during the cake drying cycle, and to discharge the cake on air-blow so that the cycle can be repeated.Whilst the mill metallurgist should not be expected to under¬stand all aspects of filter cloth manufacturer, it is however, advantageous for him to understand a little of the textile language associated with filter cloth for his own protection against ""trial-and-error"" methods, which are both time consuming and costly.If improvements are to be made over existing filter cloth in use an examination of the limiting factors of the cloth used should be made and the major causes for removal determined, e.g. cloth blinding, high moisture in cake, poor cake discharge on air blow, mechanical damage to cloth.As each of the limiting factors mentioned has a bearing on the choice of fibre used, the yarn type and weave of a suitable cloth, an under-standing of these points will assist the mill metallurgist in avoiding repetitive trials offering little degree of success."

Jan 1, 1971

By David K. Ingram

The objective of this U.S. Bureau of Mines (USBM) investigation was to characterize overburden response due to longwall mining. Subsurface strata and surface deformations were monitored at two sites in southeastern Ohio. Site A included two adjacent longwall panels. Site B consisted of one longwall panel. Both sites had similar mine geometries and overburden thicknesses. The major difference between the two sites was the rock strata within the overburden. Multipoint borehole extensometers (MPBX) were employed to measure subsurface displacements. Survey monuments were installed above the centerline and profile of each panel to measure surface deformations. Subsidence of the surface was observed before and after movement was detected in the MPBX units. Initial and final displacement of the MPBX units occurred at the same time at both sites. No deformation was detected outside the panel area. The development of overburden deformation was different over each panel. The final subsurface failure characteristics also varied between panels.

Jan 1, 1994