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The investigations reported herein comprise preliminary studies to evaluate large scale mining systems adaptable to the thicker oil shale deposits in the deeper central portion of the Piceance Creek Basin. The studies include an evaluation of the geology, hydrology and resources of the Basin., evaluation of a potential prototype mine site, synthesis of rock mechanics data on Green River Formation oil shale, selection and preliminary design and cost evaluation of six potential mining systems and a ranking analysis to aid in selecting the most promising system. Results of the ranking analysis indicate the following four systems to be most promising for large scale underground oil shale mining: - Chamber and pillar (using spent shale backfill) - Sublevel stoping with spent shale backfill - Sublevel stoping with full subsidence - Block caving with LHD's Recommendations for phase II are to investigate the above systems in greater detail, refine present cost data, and perform economic evaluations of oil shale mining using these systems.

Jan 1, 1975

By J. D. Hanawalt, W. H. Gross

Magnesium has long been known as the lightest of our engineering metals. This metal, silvery white in color, has a specific gravity of only 1.74. Aluminum, the next lightest structural metal, is 1 ½ times heavier; zinc is 4 times heavier; iron and steel are 4 ½ times heavier; and copper and nickel are 5 times heavier. Magnesium does not occur in the free state but is very abundant in nature, constituting 2.5 pct of the earth's crust in the form of various ores. It is the third most abundant structural metal, being exceeded only by iron and aluminum. Magnesium is unique, however, in that in the form of magnesium chloride it also exists in the oceans. Sea water is the source most widely used for production in the United States but magnesium is also commercially produced from magnesite, dolomite, and other ores as well as from certain inland brines. The vast quantity of magnesium existing in the waters of the oceans can be visualized when it is realized that the removal of one hundred million tons per year (the approximate annual steel production in the United States) for a million years would reduce the magnesium content of sea water only from 0.13 to 0.12 pct, providing no more magnesium had washed into the sea in the meantime. Not only is magnesium potentially very abundant but it is in addition a very versatile metal and can be shaped and worked by practically all methods known to the art of metal working. It can be cast by sand, die, and the various permanent-mold methods;

Jan 1, 1953

By R. H. Jacoby, V. J. Berry

When dry gas is injected into a reservoir containing a volatile crude oil, a significant amount of the reservoir liquid phase may become vaporized. The resultant rich gas phase, when subsequently produced, con-tributes to tank oil production. This contribution assumes greater importance, the more volatile the oil in-olved. Oil recovery may be sub-stantially greater than that predicted by conventional frontal-drive methods, which do not consider the vaporization equilibrium between the reservoir oil phase and the injected gas. A calculation method has been (developed to account for vaporiza-. tion of the reservoir liquid phase during gas-injectiorz operations, and for the tank oil production which results from this factor. Recovery performance calculations are presented for a reservoir containing a highly volatile oil. Tank oil recovery is calculated to be about twice that predicted by the use of the conven-rional frontal-drive equations. In contrastto usual pressure maintenance performance results, in which the gas-oil ratio rises at an increasing rate after gas breakthrough, the pre-dicated gas-oil ratio rises rapidly to about 12,000 scf/bhl and then rises much less rapidly. During gas inje-tion, most of the reservoir liquid phase contacted is evaporated by the dry injection gar. The gas-oil ratio during this period is dependent upon reservoir pressure. The higher the operating pressure, the lower the gas-oil ratio. The predicted behavior i., in accordance with laboratory PVT tests made to .simulate the vaporization behavior. In addition to recovery performance predictions, results of the calculation procedure include complete wellstrearn composition data of value in the design of gasoline plant facilities often used in con-rrction with gas-injection operations. INTRODUCTION In the cycling of gas-condensate reservoirs, dry gas is injected to maintain reservoir pressure during wet gas production and to thereby eliminate or reduce ultimate loss of liquids due to retrograde condensation within the reservoir. Gas injected into crude oil reservoirs has a dual function. It displaces oil to the producing wells and at the same time serves to partially or fully maintain reservoir pressure. Oil shrinkage which would occur upon pressure reduction is thereby minimized or eliminated. Accepted calculation methods are available'= for predicting recovery performance of either gas-condensate reservoirs or crude oil reservoirs which are being subjected to gas injection. In gas-condensate reservoirs, any retrograde liquid formed does not flow, and it is necessary to account only for the vaporization equilibrium between this liquid and the injected gas. Conversely, in normal crude oil reservoirs, both the oil and gas phases flow, but it has not been considered necessary to account for any vaporization of the reservoir liquid which might occur upon contact with the dry injection gas. Recently, high shrinkage reservoir fluids known as "volatile oils" have been found in increasing amounts. These oils are characterized by tank oil gravities above 4.5" API, solution gas-oil ratios above 1,000 scf/bbl, and reservoir volume factors above two. Special techniques have been devised for predicting depletion performance of reservoirs containing such oils.74.5.1; One of the characteristics of reservoirs producing volatile oils is that the reservoir gas phase carries a significant amount of oil which is recoverable as stock-tank liquid. This unusual vaporization be-havior implies that an appreciable amount of reservoir liquid would be vaporized upon contact of the oil with dry injection gas. In a gas-injection operation, tank oil recovery would he obtained not only through frontal displacement of the reservoir liquid by the injected gas, but also through production of the rich gas phase. This means that not only are improved methods needed to predict recovery of such oils from reservoirs undergoing gas injection, but it would also be expected that high oil recoveries might be obtained by such operations. When relatively dry gas is injected in to a volatile oil reservoir, phase equilibrium between the injected gas and the reservoir oil will tend to bc established. Initially the most volatile components, such as propane, the butanes and the pentanes, will account for most of the material transferred from the oil phase to the gas phase. As the partially stripped oil phase is contacted with additional dry injection gas, the heavier intermediate components, such as the hexanes, the heptanes and the octanes, will gradually transfer to the gas phase in increasing amounts. This is because the supply of lighter components in the oil phase dwindles due to the stripping action of the injected gas. This stripping action will usually continue to be effective down

CYRIL STANLEY SMITH, Chairman CARL E. SWARTZ, Past-Chairman ARTHUR PHILLIPS, Vice-Chairman E. E. SCHUMACHER, Vice-Chairman H. A. MALONEY, Treasurer FRANK. T. SISCO, Secretary 9 West 39th Street, New York, N. 1. Executive Committee 1944 1945 WILLIAM C. ELLIS C. S. BARRETT ALAN MORRIS T. A. WRIGHT KENT R. VAN HORN L. L. WYMAN

Jan 1, 1943

By R. C. Canby

The American water-jacket furnace is the outgrowth of lead-smelting at Eureka, Nev., subsequently developed in Utah and Colorado. Early smelting in Virginia, New England, or the Missouri-Kansas-Illinois district seems to have had no direct influence in the development of this furnace. First Decade, 1870 to 1880. In 1870, the draft-furnace was used in Nevada, coincidentally with the first crude sandstone blast furnaces, which were 2 or 3 ft. sq., with Sturtevant fans or small Roots blowers, and sheet-iron or water-cooled tuyeres. Stetefeldt, Liebenau, Albert Arents, and 0. H. Hahn mere the early metallurgical leaders. Arents's siphon-tap and the re-establishment of the furnace-bosh mere the most important improvements of the decade. Second Decade, 1880 to 1890. At first there were ,many small local plants; but by the time Eureka had reached its maximum production of lead-ore, two custom works (the Eureka and the Richmond) were treating all the ore, the miners having learned the economy of smelting at larger and well-constructed plants. In the early eighties, most of the features of modern practice were already discernible at Salt Lake, Leadville, Denver, and Pueblo. The small square sandstone furnaces had been replaced by rectangular water-jacket furnaces, mostly 36 in. wide, and from 60 to 80 in. long at the tuyeres, which entered between cast-iron water-jackets. Subsequently, Franz Casin, at the Holden works, Denver, put the tuyeres in the middle of the jackets, and many other improvements were made by him and others, so that the cast-iron jacket became the favorite, until the possibility of

Jan 1, 1913

By Sergey Ulianov, Arkady Senchenko, Alexey Shvets, Arkady Bakotin

"This paper contains description of research results of technology development for copper recovery from weathered tails of iron processing plant. The predominant host mineral that contains valuable component is chalcopyrite occurring in its free form and in associations with ore and rock-forming minerals. Copper grade is 0.26-0.30%. Emulsion inclusions of chalcopyrite in pyrite and sphalerite were noted. Major problem is low copper recovery (30-35%) by flotation. When studying chalcopyrite in primary concentrate it was determined that the surfaces of many chalcopyrite grains are covered with oxide films which prevented collector attachment onto them. Second issue was deep association of chalcopyrite with pyrite and sphalerite. Sulfidizing reagent addition did not help to reach the required level of copper recovery to concentrate. In the result of research performed the technological flowsheet was developed including preliminary treatment of head material in a special unit aiming at oxide films removal, followed by copper rougher flotation on head size tails, crude concentrate regrinding and a number of cleaner flotation operations. After the treatment of weathered tails according to the flowsheet developed, copper recovery to flotation concentrate became 71.53%, at 23.46% copper grade. The suggested technology allows one to solve the issue with treatment of technology-related copper-containing stockpile material, as well as to include the ores where copper is represented by sulfide minerals covered with oxide films into processing."

Jan 1, 2014

By Adrian M. Crawford

INTRODUCTION A study has been made of the stability of blocks and wedges of rock subjected to gravity forces in the roofs of underground excavations. Rock wedges may become wholly or partly self supporting with the mobilization of shear resistance of discontinuities bounding such wedges. The influence of in-situ stresses and the relative stiffnesses of the intact rock, and shear and normal stiffnesses of the discontinuities has been investigated. A two dimensional, plane strain model of symmetric rock wegdes in a horizontal stress field has been utilized. A comparison between the results of an extension of a closed form solution proposed by Bray(1981), and numerical analyses with Displacement Discontinuity elements (Crouch, 1976), are presented. These analyses indicate that the stability of the wedge and the stress redistribution around the wedge upon excavation of an opening is markedly influenced by the ratio of intact rock stiffness to seam normal and shear stiffness. It is shown that the analytical solution provides a reasonable measure of the lower and upper bounds of the loads necessary to cause failure of the wedge. MODELS The problem considered (Fig. 1) is a two dimensional plane strain model containing two discontinuities. The discontinuities are symmetrically disposed with respect to a horizontal excavation which forms a wedge of rock bounded by these discontinuities. The angle of the intersecting discontinuities at the apex of the wedge is 2[a]. Mechanical properties of the two discontinuities are identical, being represented by linear normal and shear joint stiffnesses Kn and Ks and angle of friction [o]. The rock wedge is loaded by an in-situ horizontal stress field [ah]

Jan 1, 1982

By S. Terry, J. G. Munro

A unique feature of the recently dedicated pelletizing complex of Hamersley Iron Pty. Ltd. is the dry grinding circuit for the iron ore fines. This facility, located at Dampier, some 800 miles north of Perth, Western Australia, has a rated annual capacity of 2 million tpy of iron ore pellets. The Mt. Tom Price orebody, which supplies the pelletizing plant, is a massive deposit of high-grade hematite containing an estimated 500 million tons of ore averaging 64% iron. The main impurities are ferruginous shales that occur in bands of varying widths in the orebody. An average analysis shows 4.4% SiO2, 2.0% A12O3, 0.05% P and 1.8% LOI.

Jan 5, 1968

By Arthur F. Taggart

TO all Mineral Dressers, but particularly to those in the Coal and Industrial Minerals Divisions: Ted Counselman, retiring after two years at the helm of the Milling Committee, pointed with pride to the continued growth of that committee, and sang the swan song "Why ain't we a Division of Mineral Dressing?" Our genial Secretary pointed out, handily, that, you see, the way the Institute is divided there are several blocks running across this way here, and one running all the way down here, and another running part way down here, and they all cut across each other like this, and anyway the miners want to be a Division now, so why not you Mineral Dressers be good and not upset the big Institute organizational chart? And anyway again, Divisions have vested interests, and a Division of Mineral Dressing would take something away from Coal and something from Industrial Minerals, and any good institutional man can see that a Division would never give anything up. It was all quite confusing, and apparently not too convincing, because then the Milling Committee went ahead and voted unanimously it is a good idea, let's see what the other fellows think about it as well.

Jan 1, 1944

By Yesil MM, Bozdag T

The swelling process is an impor- tant problem causing damages to the structures in or on swelling rocks, both during construction and operating life. To understand swelling problem, a number of testing methods have been developed by many researchers. In these studies, the swelling parameters, in most cases, are derived from oedometer tests. The swelling parameters determined from oedometer type tests represent one-dimensional behaviour (one-dimensional swelling law) therefore, it is quite difficult to extrapolate the oedometer type test results to the three-dimensional in-situ conditions. To overcome these problems, a three-dimensional approach is suggested for clay bearing rocks. Results of triaxial swelling tests conducted on marl from Dodurga Lignite Coal Mine are presented. Triaxial swelling characteristics of the marl are presented and design approach for tunnels is described.

Jan 1, 1992

By A. G. Pasamehmetoglu

The swelling process is an important problem causing damages to the structures in or on swelling rocks, both during construction and operating life. To understand swelling problem, a number of testing methods have been developed by many researchers. In these studies, the swelling parameters, in most cases, are derived from pedometer tests. The swelling parameters determined from oedometer type tests represent one-dimensional behaviour (one-dimensional swelling law) therefore, it is quite difficult to extrapolate the pedometer type test results to the three-dimensional in-situ conditions. To overcome these problems, a three-dimensional approach is suggested for clay bearing rocks. Results of triaxial swelling tests conducted on marl from Dodurga Lignite Coal Mine are presented. Triaxial swelling characteristics of the marl are presented and design approach for tunnels is described.

Jan 1, 1992

By D. W. Evans

Mine subsidence problems due to coal extraction have occurred in a number of areas throughout the United States. Depending on the local geology, the depth of the mined seam, the type of mining method employed for extraction, and other related factors, subsidence can result in anywhere from slight displacements to a total loss of ground. These conditions can have serious consequences on the health and safety of the people living above the mined areas. A number of methods exist to provide support for the ground overlying mines. All of these methods employ some mechanism for providing additional support to either the roof of the mine or the sides of the pillars. Since failure usually occurs due to overburden stresses which are transmitted to the roof and pillars, these methods employ techniques to counteract stresses induced due to the coal extraction. The applicability of any particular method will depend on the availability of backfill material, the areal extent of the affected area, and of course, the cost. The primary use of coal ash for subsidence control has been as a backfill material for the stabilization of large areas. Large scale backfilling projects for subsidence control have been performed in Rock Springs, Wyoming, Wilkes-Barre and Scranton, Pennsylvania, and in Fairmont, West Virginia. Some of these projects have utilized sand, as well as, coal ash as backfill material. Much of the backfilling work performed in the United States has been done in an effort to control mine subsidence in abandoned mines. South Africa, on the other hand, has used backfilling extensively both for ash disposal and to increase extraction in active mines. The utilization of repetitive fill and mine techniques has resulted in extraction increases of as much as eight percent in shallow mines and as much as twelve percent in deep mines.(1) The coal ash injection system which can be used for backfilling depends largely upon whether the mine voids are dry or submerged. For dry mines, hydraulic or pneumatic conveyance systems can be used, while submerged mines are limited to backfilling by hydraulic methods. The use of coal ash as a backfill material has a number of advantages, such as: 1. Coal ash is available in areas throughout the United States and in many instances is conveniently located near areas requiring backfilling. 2. Coal ash is available in significant quantities since many coals when burned will result in about 15 to 30 percent ash by weight. 3. Coal ash as backfill is, in many instances, the most economical alternative fill material. Due to the costs associated with above ground disposal, power companies will often times give the material away to lower their overall operating expenses. 4. Coal ash is usually pozzolanic in nature, that is, this material results in cementitious bonding within the backfilled matrix of material.

Jan 1, 1982

By Kerry M. Masson

Perhaps the hottest item on the agendas of most state legislators this year is the state budget. The main question: Where will all the dollars come from to finance health care programs, state jobs, unemployment compensation programs, and on and on? This is especially so since people are out of work, business bankruptcies are up, sales are down, and incoming revenues from some sources have decreased or dried up. A sure bet is that state taxes will be increased in some form or another. The mining industry could face increased income taxes, property taxes, severance taxes, or even a host of new taxes (if the state does not already have them) like a gross receipts tax, investment tax, or tax on revenues made outside state borders. That's bad news for an already depressed industry, even though increased taxes may be the least of the industry's worries in the current economic climate. While reopening existing mines and developing most new mineral projects depends primarily on higher commodity prices, new taxes still could pose long term concerns for mine project development. Just how mineral tax law impacts a project is not easy to figure. It involves a complex set of calculations based on interpretations of numerous federal, state, and local tax laws that change almost annually. At best, projections of tax effects for the life of a mine are educated guesses. At the same time, projections are necessary to evaluate the economic feasibility of a mineral project. At a recent Technology Transfer Seminar, the US Bureau of Mines introduced a computer software program designed to evaluate the feasibility of a mineral project and to determine the tax effects on the project's discounted cash flow rate of return (DCFROR). The program, called MINSIM, began in 1967 as a 200-statement FORTRAN II program for evaluating a hypothetical large-scale open-pit gold mine. This single-commodity oriented program employed discrete simulation techniques and a continuous DCFROR was used to measure the effect of changes in revenues and costs. Over the past 15 years, MINSIM has developed into a program 70 to 100 times larger than the original. Basically, it will analyze costs and parameters specific to an identified deposit, then determine the DCFROR. Or by using a specified DCFROR, it will determine the primary commodity price required to attain that specified rate of return. MINSIM, which is explained in detail in this article, is available from the Division of Minerals Availability, USBM free of charge. Written in FORTRAN IV, it comes on punch cards or magnetic tape and is compatible with most major computer systems. The MINSIM Program The main objective of any freeenterprise mining venture is to make a profit. To determine profitability of a given project, alternate methods of operating and financing must be evaluated. That is the purpose of MINSIM. While there are a number of methods of evaluating the economic profitability of a mining project, MINSIM uses the Discounted Cash Flow Rate of Return (DCFROR) method as its major criterion because DCFROR considers the time value of money and gives the truest measure of profitability. One disadvantage is that the calculations are deposit oriented. In other words, MINSIM analyzes only those costs and parameters specific to the deposit. It cannot be used to evaluate the overall corporate picture. The program is designed to simultaneously handle five different commodities and a leach operation for any type of mining project. For example, analysis of a coal project would include only one commodity-coal at the mine mouth. Analysis of a copper operation might include numerous commodities-from the raw material to the refined product. Input MINSIM considers capital investment-recoverable exploration, acquisition, and development costs; depreciable capital investments such as mine plant and equipment, mill plant and equipment, and infrastructure costs; all general and commodity specific operating costs; and the cost of alternate financing methods. The program has the capacity to incorporate different types of depletion allowances, numerous commodity-dependent severance taxes, variations of property taxes, and many methods for calculating state or provincial taxes. There are even many different ways to calculate federal and national taxes. The capacity to handle tax variations is generated from an internal subroutine in the program called the "open file." The user can reconstruct, customize, or evaluate any kind of tax desired. Outputs Given this kind of capacity for numerous input parameters, MINSIM is capable of the follow¬ing major outputs:

Jan 3, 1983

By Anderson Azevedo Agra

Esse trabalho teve como objetivo avaliar o efeito da adição de diferentes teores de coque verde de petróleo (5, 15 e 30%) nas propriedades termoplásticas de misturas de carvões contendo carvão nacional da camada barro branco. A caracterização termoplástica das misturas foi realizada a partir de testes de plastometria Gieseler e dilatometria Audibert-Arnu. A caracterização dos carvões mostrou que o carvão nacional possui propriedades termoplásticas muito superiores aos demais carvões. Por consequência, verifica-se que a sua introdução nas misturas causa aumento das propriedades termoplásticas nos testes de plastometria e dilatometria. O coque verde de petróleo, em contrapartida, é um aditivo inerte e atua como um depressor das propriedades termoplásticas. Constatou-se que a adição do coque verde de petróleo às misturas causa redução da fluidez, do intervalo plástico e dilatação nos testes realizados. A sinergia entre do carvão nacional de alta fluidez e o caráter inerte do coque de petróleo mostrou-se vantajoso.

Oct 30, 2017

By J. B. Gwiazda

Maintenance of a constant load setting throughout longwall support units and selection of the proper initial bearing capacity depending on the type of roof strata are the basic factors that ensure good performance of roof support in a longwall. These requirements can only be met by hydraulic support. The greatest advantage of hydraulic support is achieved when uniform pressure is imposed on the roof throughout the length of the longwall. Such support, however, is provided only if each of the support units acts with the same force against the roof, i.e., has the same setting load. In such cases, the roof behaves like a uniform plate without bending and shearing stresses, thereby ensuring an undisturbed structure. Without a positive set value system, achieving an equal setting load for all units of the longwall support is impossible. Due to alterations of the feed line pressure of support units as well as some reasons related to man's psychology, operators extend the height at different setting loads. This produces nonuniform roof stress, and disturbs the structure. Consequently, the roof usually cracks. The author has developed a positive set value system, which is described in this Technical Note. Selection of the setting load Two pressure values in the feed lines are usually applied in longwall hydraulic systems. Lightweight support is fed by 25 MPa (250 bar) liquid, while heavy duty units receive a nominal pressure of 31.5 MPa (315 bar). Such pressure is required not only for the props but also to power the adjust¬ment jacks and the advancing ram. If the feed pressure is too low, there will be difficulty in shifting the unit despite the inversion system of the advancing rams. On the other hand, for many roof types, the feed pressure often appears to be too high when applied as the setting load pressure. An excessive setting load acts too strongly against the roof, crushing weak strata close to the roof. The author has recognized a case where an excessive setting load destroyed not only the nearby roof strata but also the strata above a 2-m (6.6-ft) sandstone layer. In addition, an excessive setting load relieves the side¬walls, increasing the resistance when using cutting machines. As a result, the yield of coarse coal is diminished, and increased fines dominate in the final product, lowering its economic value. As indicated, selection of the proper setting load, depend¬ing on the mining and geological conditions of the extracted seam, is extremely important. In some mines, measures applied to prevent disturbances include reduction of the feed line pressure by adjusting the feed pump valve. The disadvantage accompanying reduced feed line pressure is more difficult operation in advancing the ram. Due to the reduced feed line pressure, the force of the advancing ram is much lower than the designed value. Other designs suggest using a third feed line. However, installation of supplementary valves on the support units is required, a time-consuming and expensive procedure. The disadvantages of the powered supports are eliminated by a system designed by the author. So far, such a method of setting load control has not been used in any type of support. Setting load control unit The designed positive valve set for prop loading and the setting load control correspond to existing control systems for hydraulic powered support. The layout of the unit connected to the hydraulic prop control is presented in Fig. 1. The unit is marked LIDS. It incorporates three valves that may operate separately or connected. Valve A automatically opens and closes with liquid flow in the prop feed circuit. The valve is opened when the canopy touches the roof and closed when the support unit is withdrawn. Valve B serves as the setting load control. Valve C automatically opens and closes the flow in the line connecting the under-piston space of E to the prop F with the separator G. The valve block of each support prop is marked BZ. The UDS unit is connected by the hydraulic lines to the F prop control circuit. A valve is connected by H to pressure line J and by K to the G separator. In the UDS-3 version, line L is connected to M, linking the over-piston space of F prop with the G separator. Valve B is linked with valve A by a connector; it is also connected to the under-piston space E of prop F by line P. Valve C is fixed between lines K and P, connecting space E of prop F with the separator G. When setting the support, the liquid flows from line J through separator G, the BZ valve, and valve C to the space E of prop F. When reaching the roof with the canopy, valve A is opened and C closes. In this way it is impossible for the operator to cause the liquid pressure in space E of prop F to reach the level of line J. The prop pressure is set by valve B of the UDS unit. When withdrawing the support, valve C is automatically opened and A closed. Three UDS units have been fabricated and are designated

Jan 1, 1990

By Peter N. Calder, Garston Blackwell

"The history and analysis of a structurally complex open-pit rock slope displacement are described. The failure involved part of the only haulage access to a major ore zone. The ongoing movement was monitored using an electronic distance measuring device and a continuous electronic system specifically designed for the problem. A major fault, infilled with a thick clay gouge, and intersected by other structural features, resulted in the transfer of weight to a rock mass acting as a buttress in the lower regions. Movements were affected by blasting vibrations and ground-water conditions. Remedial measures included limiting blasting levels and lowering the water table, following which mining was successfully resumed in the area.IntroductionBrenda Mines is situated in a mountainous region of the southern interior of British Columbia; the location is indicated on Figure 1 . The elevation is approximately 5000 ft , giving a climate typical of more northern areas. Temperatures vary from -30°C to + 30°C. A snowfall level of 400-800 cm is experienced from November to April. During the spring, a heavy runoff period occurs, increasing the pumping rate in the pit from a nominal 50* gal/min to 2000 gal/min.The orebody occurs in a fractured Jurassic rock mass referred to as the Brenda Stock; it is approximately 3000 ft in diameter and 1000 ft deep. The Brenda Stock was intruded into the Upper Triassic Nicola Group tuffs, breccias and argillites. Mineralization occurred in several stages in a relatively homogeneous quartz diorite host rock. Shearing, faulting and jointing occured later in many stages, producing mineralized clay gouge zones up to several feet in thickness'> , These gouge zones have a major effect on the stability of the pit walls.The structural geology of the pit walls is otherwise relatively simple. Figure 2 is a conventional pole diagram indicating the orientation of the rock structural systems which are present. The major system has an average dip of approximately 70 degrees to the south and strikes approximately east /west , it is not undercu t by the pit slope. Figure 3 is a photograph of part of the North wall on which this system is indicated.The basic pit design consists of a working bench height of 50 ft, with a final wall height of 100 ft between berm s and a 100-ft-wide berm every second lift. Combined with a local face slope of 50-70 degrees, the resulting wall slope, not including haulage roads, is 45 degrees. Figures 4 and 5 are generalized plans and sectional views of the pit."

Jan 1, 1980

By E. D. Thompson, Y. J. Zhang, K. F. Unrug

This paper presents the results of a recent study on the development of an in situ testing method for determining coal strength in mine pillars. The strength testing is performed in the horizontal holes drilled into the coal rib using a penetrometer, which is an hydraulically powered device that uses an indenter to press on the surface of the borehole until the load reaches the failure point of the coal. The pressure and the penetration of the loading pin are recorded by a data-acquisition unit. The results collected from several coal mines indicate that this testing method is ideally suited for the realistic coal strength measurements. The new testing system not only improves the accuracy of the pillar-strength determination, but it is more cost efficient than the conventional method.

Jan 1, 1997

By Chengxian Lui

Detailed mineralogical and metallurgical investigations were carried out on a phosphorous-bearing manganese carbonate ore from the Huayuan manganese mine, Hunan, China. Microprobe analyses indicate that the Manganese occurs mainly in calc-rhodochrosite and in rhodochrosite. The cOll'pOsitional range of these manganese carbonate minerals is 50 -80 % MnOJ3, 0 -35 % CaOJ3, 5-35 % MgC03 and 0 -15 F~. The manganese carbonate minerals are very fine grained, IOOSt are between 4.6 and 9.4 1m in diameter. The small grains are clustered into aggregates that form bands 0.5 to 10 rnn wide. The phosphorous-bearing mineral in the ore is fluorapatite and is in grains that are generally smaller than 6 1m in diameter. Metallurgical tests show that it is possible to concentrate the aggregates of manganese carbonate minerals by high intensity magnetic separation, and to reduce the phosphorous content by rpasting the concentrate to convert the manganese carl::x>nates to insoluble hausmannite, and then leaching the roast product with HCI to dissolve the fluorapatite.

Jan 1, 1989

By Smith DM Jr

Silver deposits, in which silver forms at least fifty percent of the value of the ore, are abundant and large on the east side of the Pacific and are absent in the western Pacific. To determine if this uneven distribution is related to features of consuming plate tectonic boundaries which dominate the metallogeny of the Pacific Rim, the variation of Ag/Au in porphyry copper deposits was used to estimate the relative silver content of magma generated in subduction zones. Porphyry copper provinces with high Ag/Au occur in regions of the eastern Pacific where silver deposits are abundant, suggesting that the distribution of silver deposits is controlled by the relative abun- dance of silver in subducted ocean crust. Ocean crust being subducted in the eastern Pacific is mostly less than 50 million years old in contrast to most ocean crust in the western Pacific which is much older. Enrich- ment of silver in young ocean crust at spread- ing centers may reflect metallogenetic evolution over geologic time. Silver may be transported to the surface in volcanic rocks, and deposits are common where felsic varieties are abundant. The high ,solubility of silver in natural waters provides a natural storage mechanism for silver weath- ered from these rocks and ultimately circulated in near-surface hydrothermal systems where many silver deposits form. The regional distribution of silver deposits is not influenced by discoverability, vertical metal zoning, or regional tectonic style. The effect of igneous differentiation is unclear.

Jan 1, 1987

By P. Marinos, G. Tsiambaos, H. Saroglou

Anisotropy is a characteristic of intact foliated metamorphic rocks (slates, gneisses, phyllites, schists). ?esting was used to establish the anisotropic behaviour of selected gneissic rocks. The effect of anisotropy on various mechanical properties (strength, deformation) and dynamic properties (wave velocity) was examined. The rock samples were also tested at successively higher confining pressures in order to evaluate the effect of anisotropic behaviour at high overburden pressures. L’ anisotropie characterise les roches foliées (schistes, gneiss, phyllades). Dans ce travail des essais en laboratoire ont été exécutés afin de déterminer le comportement anisotropique des roches gneissiques. L’ effet de l’anisotropie a été examiné par rapport aux propriétés méchaniques (résistance, deformation) et propriétés dynamiques (vélocité ultrasonique). En outre des essais des roches ont été exécutés a des compressions latérales successivement plus grandes afin de déterminer le comportement des roches sous grands charges. Anisotropie ist eine Eigenschaft der geschieferten Gesteine (TonSchiefer, Gneis, Phyllit, Marmor). Versuche wurden durchgeführt, um anisotrope Verhalten von gneis Gesteinen zu ermitteln. Der Einfluss von Anisotropie auf mechanische (Festigkeit, Dehnung) und dynamische Eigenschaften (Wellegeschwindigkeit) wurde bestimmt. Die Dreiaxialversuche wurden unter grossem allseitigen Drücken entnommen, um das anisotrope Verhalten auf grösse herrschende Spannung zu bestimmen.

Jan 1, 2003