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By G. Lyman

The cross-belt sampler is a device that is very widely used even though it has not been ratified by the Standards associations. This paper is concerned with the bias testing of two cross-belt sampler designs against stopped belt samples and a cross-stream cutter at the belt end. The bias analysis is carried out using size distribution as the analyte and conventional t-testing and the Hotelling T squared test, which are compared for their effectiveness. The paper considers the issue of detectable bias and the statistical planning of bias tests.

Jan 1, 2010

By Monika Patrycja Polak - Micewicz

This paper presents an approach for estimating the fatigue life for the base of powered roof supports (shield) manufactured by the FAZOS roof support company. FAZOS?s powered roof supports are designed to operate on an inclined coal seam in full caving with a medium, strong roof strength. This shield support is utilized in conjunction with a shearer and face conveyor for a complete longwall mining system. To design shield support, it is essential for contractor to know the physical (hardness, toughness, etc.) and mechanical properties of material (tensile strength, Young?s modulus, etc.) used for the shield support as well as the geotechnical properties of the mine site. The fatigue strength of the shield support material depends on the mean stress, alternating stress, cycle frequency, transport dimensions, mine environment and other factors. In order to estimate the fatigue life for a powered roof support system, it is assumed in this paper that the support must keep the roof stable in the mine under variable load cycles. The approach selected in this study contains Goodman?s model (Goodman, 1899) for all blocks in the design housing which is subjected to sinusoidal load. On this basis, the degree of fatigue damage was calculated and compared to the results of experimental tests. It will be shown that there is a significant detrimental effect on the fatigue life of the base of the powered roof supports due to geometrical notches. The Ramberg-Osgood model and damage accumulation rule (Palmgren-Miner) (Miner M., 1945) were used and numerical analyses were conducted, utilizing ANSYS finite element software. These analyses play a very important role in longwall casing design. The proposed method allows assessment of the yield state and forecast of the structure cracking, taking plastic strains occurrence into account. The presented method is universal and can be applied for fatigue life estimation of other subassemblies of powered roof supports. The final portion of the paper presents results of variable amplitude loading simulations on the S355N and S690Q steel used to make powered roof supports. The results of the physical tests were compared with the results from finite element methods. The proposed approach to calculate fatigue life gives the best correlation between the experimental results and calculated values of fatigue life for the powered roof support base. Finally, the design process uses a simple approach to predict fatigue life in a short time, reducing design costs and providing longer service life for roof supports.

Jan 1, 2012

By Xuejing Xie, Tianxiang Ren

Paper presented at the 28th International Geological Congress held in Washington DC, July 1989 (International geochemical mapping sessions). Standardised stream-sediment sampling procedures have been used in mountainous and hilly terrains. Special sampling procedures were developed for application in remote environments, such as high mountains, desert, semi-desert, karst and loess-covered regions. The diversified analytical methods used in more than 20 analytical laboratories participating in the project have been unified into two multi-element, multi-method analytical systems. A unified data monitoring procedure was developed based on primary and secondary standard samples. To date the project has covered about 4 000 000 km2 and the aim is to complete the coverage within the present decade

May 1, 1991

By Antonio Karzulovic, Sergio Olavarría, Patricio Adriasola

The economical analyses of different Chuquicamata open pit mine planning scenarios, indicate that the pit closure should occur at latest in the year of 2017. However, about 60,000 m of drill holes have demonstrated that below the pit bottom there is a potential of 2.3 billion tons of ore. Hence, Division Codelco Norte developed the scoping engineering for a large underground panel caving operation, similar to El Teniente mine. This project considers the exploitation of a 2500 m 300 m footprint, with three 250 m lifts. The plan considers to initiate the construction in the year 2009, to begin the production in the year 2015 and achieve a production rate of 45 million tons per year in the year 2021. A large-scale transition from open pit to underground mining like this one presents three main challenges: (1) to include the geotechnical aspects relevant for mine design and mine planning, (2) to define the proper surface and underground infrastructure, and (3) to fulfil the project deadlines and to achieve the production targets. This paper summarizes this transition project and discusses these three main challenges.

Jan 1, 2006

By M. E. Volin

The tungsten potentialities of the Combination mine were examined by a mining engineer of the Bureau of Mines in 1947. A report based upon his personal knowledge of the mine and the results of the examination contained recommendations for further investigation. This report presents factual data from Bureau of Mines field investigations begun in August 1947 and continued until December 1948, except for a 5-month recess during the first winter. The Combinat.ion mining property of 52 patented claims and 15 patented mill sites is in the Black Pine mining district, Granite County, Mont., 11 miles northwest of Philipsburg. The altitude in the mine vicinity is approximately 6,500 feet.

Jan 1, 1952

By Albert L. Toenges

Early in 1944 the Chilean Government expressed a desire for assistance from the Bureau of Mines in a study of the coal deposits, coal-mining methods, and preparation and benefication of coals in Chile. A Memorandum of Understanding setting forth the purpose of the work was executed by the United States Government and the Government of Chile. Parts of this agreement are quoted: On February 4, 1944, the Ambassador of Chile in Washington expressed the interest of his Government in obtaining the loan of a mission of experts to assist in the conduct of a survey looking toward the utilization of the low-grade coals of Chile and the application of such technology as may be developed for the distillation of these coals and the use of oil shales. The matter has since been the subject of correspondence between the Secretary of State and the United States Department of the Interior, and the latter Department has agreed to cooperate with the Government of Chile, through the Bureau of Mines, subject to the following understanding:

Jan 1, 1948

By Donald James Butler

Problems resulting from underground mines in three inactive mining districts in Colorado were investigated. The purpose was to determine how these problems could be reduced or eliminated in new closings -- essentially by benefitting from lessons of the past. Mines in Leadville, Westcliffe and the Cripple Creek-Victor districts were evaluated. Two basic types of problems were found to exist in the districts: environmental degradation and hazardous conditions. Environmental problems result largely from acid and toxic drainage from the runes and from leaching of surface waste rock piles and mill tailings impoundment. The acid drainage contributes high levels of metals to streams and deposits sediment in the stream bottoms. Erosion of waste piles is a lesser problem. Hazardous conditions from open or improperly sealed mine shafts and adits, mine subsidence pits, and from deteriorating and unsafe surface structures are common to the three districts. These problems become worse with the ravages of time and vandalism. Engineering solutions which would correct or reduce many of these problems are presented. These recommendations should also be applied to new mine closures, however, more basic changes are needed to effectively implement improved mine closures. The changes must take place in the areas of legislation, mining practices and education. Legislated regulations should realistically reflect the needs of both the mine operators, protection of the environment and the best interest of the general public. Benefits should be provided for compliance with regulations instead of penalties being assessed for noncompliance. Hazardous conditions and environmental problems associated with mines can be alleviated through improved mine design and effective cloning procedures. Education should provide an appreciation by the general public of past and present problems facing mine operators. This will result in an improved mining climate which, in turn, will insure a continuing supply of minerals to meet increasing needs.

Jan 1, 1983

By James H. Aase

[This study provides data on the physical and hydrological makeup of the ,t hakes waterway system and forecasts quantities, traffic patterns, and ping cost of prospective bulk mineral commerce projected to be transported it. Factors affecting the shipping cost of iron ore, bituminous coal, imestone were quantified and integrated into a computer program that can d to estimate costs under varying sets of conditions. Combined ship of iron ore, bituminous coal, and limestone in 1995 were estimated at million tons. The cost of operating the U.S. vessel fleet for trans-ng an indicated 80 percent of this traffic tonnage was projected to be $163. 5 million.]

Jan 1, 1970

By Yongbin Yang

Cathodic reduction of oxygen is a process involved in many fields. As is well known, the mechanism of oxygen reduction usually varies considerably with electrode substrates. In this paper, cathodic reduction of oxygen on gold electrode was studied by linear sweep voltammetry with regards to cyanide leaching of gold. As the results shows, the electron transfer number increases as potential shifted negatively and decreases as pH value increases. Besides, the increment of electron transfer number as a function of potential decreases when pH value increases. When pH increases to 13.0, the volt-ampere curve exhibits a relative flat section with currents approximate to the limit current density of a 2e process. By varying dissolved oxygen concentration, the electron transfer number was calculated for pH11.0 at different potentials, the results being 2.387e, 2.732e, 2.982e, and 3.227e at, -0.35V, -0.40V, -0.45V, and 0.50V, respectively. The calculated current densities are in good conformity with measured results.

Jan 1, 2010

By B. W. Naugle

Twenty-nine sole-heated-oven expansion teats were made on 9 different coals, and apparent specific-Brevity tests were made on 12 of the resultant cokes. The coals, which ranged in dry, mineral-matter-free fixed-carbon content from 58.7 to 81.1 percent, were tested over a rather wide range of moisture content and dry-coal bulk density to determine the separate effects of these variables on linear coal expansion. The experimental data support the follow expression relating "as-tested" coal bulk density, moisture content, and linear expansion, [ER = (1-MR) (1+Et) - 1; BDt] where ER = fractional expansion at a reference bulk density of 55.0 lb. of 1 percent moisture coal per cu. ft., Et = fractional expansion at Mt and BDt, MR = reference moisture content = 0.01, Mt = moisture content, "as-tested", BDR = reference bulk density = 55.0 lb. per cu, ft., BDt = bulk density, "as-tested", 1b. per cu. ft.

Jan 1, 1957

By C. E. Rork

This paper discusses various mechanical improvements that have been gradually incorporated in the copper-willing plants of the Southwest daring the past 14 years, power plants for concentrators, use of large-size units of equipment, and the effect of plant capacities on costs. The improvements in mechanical equipment and plant design have contributed in the reduction of operating costs; in some instances a saving in the capital cost per ton of daily capacity milled has resulted.

Jan 1, 1935

By L. C. IlsLey, H. H. Clark

In various publications relating to safety in mining the Bureau of Mines has called attention to the hazards attending the use of openBame lamps. An open-flame lamp is a potential source of danger in any coal mine. It may start a fire in a dry mine or an explosion in a gaseous mine. The type of open-flame oil lamp now used in mines is the product of long evolution; its principal merit is simplicity. That such a light is unsafe in an atmosphere containing gas (methane) is evident, and Sir Humphrey Davy immeasurably increased safety in coal mines when he found means of protecting a lamp flame so that it would not readily ignite gas. The safety lamp, however, gives less light than the open-flame lamp, is not as simple in construction, is more cumbersome, and must De carried in the hand .. Consequently, some miners are reluctant to abandon the open-flame lamp for the safety lamp, and risk their own lives and the lives of their fellow workers with the one rather than to be hampered by the other. When small electric bulbs, with their clear, white light, and small electric storage batteries became available, the advantage of combining these elements for a miner's lamp seemed manifest. The combination looked simple and safe, but was soon found to have elements of danger and weakness peculiar to itself. The Bureau of Mines showed, in 1911, that the breaking of a miniature electric bulb in an inflammable mixture of gas and air might ignite the mixture, so that only the fragile glass of the lamp bulb might stand between the miner and injury or death. There Was also a possibility that sparks from the small battery would ignite gas, and the accidental spilling of the contents of a battery on the miner's clothing or skin was a possible source of injury. The first portable electric miner's lamps that were carried in the hand, or with the battery strapped to the back and the light carried on the head, were exceedingly crude and were designed without appreciation of the sources of danger. The possibility, however, of producing a safe and practical miner's lamp by the proper combination and design of the elements available promised to increase safety so greatly that the Bureau of Mines attemr>ted to stimulate better design and construction by careful investigations and the establishment of an approval system that would be an assurance to the miner and an advantage to the maker of the lamp. As a result various manufacturers submitted types of lamps, cords, and bulbs for test and cooperated with the bureau in efforts to so improve the safety features of these devices that the lamps would P&$ specific tests for approval.

Jan 1, 1917

By M. E. Kravetz, E. B. Milosavljevic, L. R. Solujic

Gold ores containing high levels of cyanide-leachable copper minerals, such as covellite, chalcocite, bornite, malachite, azurite, and cuprite have traditionally been difficult to treat economically. A novel hydrometallurgical process for efficient treatment of cyanidation effluents obtained by leaching high copper gold ores (or concentrates) based on the use of Cherokee Chemical organo-sulfur reagents (OSR-A, OSR-B and OSR-C) is described. The process may be modified to selectively precipitate silver, or completely recover silver, copper and zinc, as well as regenerate significant amounts of cyanide. For example, data obtained demonstrate that 100 % of silver and zinc, and 98 % of copper were removed from the solution, while 80 % of cyanide was recovered. The treated barren solutions exhibit enhanced gold and silver leaching kinetics compared to the untreated controls.

Jan 1, 2004

By Francis T. Freeland

In the West many precious-metal mines are worked in patches by lessees, under conditions which closely resemble those of what is called " tribute-work" in Cornwall.* The company has its own foreman or inspector, and usually employs the engineman, blacksmith, pumpman, and perhaps other general workmen. As an inducement to work on a new piece of ground, where no ore is in sight, the company may advance a " footage"

Jan 1, 1896

This Bureau of Mines report concerns two subjects important in the application of electric power in mining systems. Electrical transients and their suppression are discussed, and several considerations are explored with regard to the use of explosionproof or other electrical enclosures.

Jan 1, 1979

By R. O. Burt, D. J. Ottley

"SYNOPSISRecent developments in the use of the Bartles-Mozley table and the Bartles CTS screen are described for the gravity preconcentration of fine heavy mineral and metal particles present in low grade pulps. The B-M table is a relatively new device used for the recovery of particles of up to 100 micron size down to 5 microns or in the case of gold and platinum, down to 1 micron. The CTS screen is a wet screening device used for feed preparation ahead of the Bartles-Mozley table and will size effectively down to about 300 mesh. Results and operating data for a number of different materials are given including outline flowsheets; the effects of the major variables on the performance of the table are briefly discussed. The potential of the B-M table to treat a variety of different ores, coal, tailings, and waste products are considered. The utilization of the B-M table in association with other unit processes to improve overall results as well as to improve the economics of design and performance of plants are also mentioned.INTRODUCTIONA number of new gravity concentration devices have been developed in recent years for the recovery of fine heavy mineral and metal particles but for reasons which include low capacity, high capital or operating costs, competition from other and better processes, the absence of simplicity or reliability in operation etc., only a few which include the Bartles-Mozley table, have been proved to be of commercial application.The name of the machine is derived from the inventors name, Richard Mozley, who developed the B-M table at the University of Bristol in England. The table was subsequently taken up and patented, world-wide, by the National Research Development Corporation a British government agency. An exclusive license to manufacture the table was granted by NRDC to Bartles (Carn Brea) Ltd. in Cornwall, England."

Jan 1, 1973

By M. C. Flemings, F. R. Mollard

Two-phase Pb-Sn alloys, ranging in compositiotz from 12 to 26 at. pct Pb, were unidirectionally solidified in a convection-fvee system, with thermal gradients in the liquid of up to 480°C per cm. Plane front solidification Loas achieved in all alloys at sufficiently steep gradient and slow growth rate. Conditions causing breakdown of the interface to a cellular or dendritic structure were roughly as predicted by a sinlple constitutional supercooling criterion. Structures of alloys of near-eutectic composition, solidified with plane front, exhibited a lamellar structure; the alloys furthest from the eutectic exhibited a rod-like morphology. Assumptions used in a previous paper for calculations of solute redistribution in two-phase plane front growth are shown to be reasonable for Pb-Sn alloys. Results of calculations are in good agveement with experiment. These show that variations in growth rate during solidification of the composite produce marked changes in average composition of the solid. IN a previous paper, Part I,' conditions necessary for plane front solidification of two-phase alloys were discussed and calculations given on solute redistribution in this type of solidification. This paper, Part 11, describes experiments on Pb-Sn alloys, designed to check the assumptions of the analyses presented, and to demonstrate their applicability to a given alloy system (Pb-Sn). APPARATUS AND PROCEDURE General. A vertical crystal growing unit was built for the study as described below, and "normal solidification" employed throughout (i.e., the ingot was completely melted except for a portion near the bottom end and then solidification initiated). The furnace was designed to permit achieving very low interface velocities, and steep gradients, in essential absence of convection; it is sketched in Figs. 1 and 2. Simple heat flow considerations indicated choice of a small-diameter specimen (ingot) to achieve high thermal gradients; ingot size chosen was 0.3 cm in diam. The ingots were held inside silica tubes 0.06 cm wall thickness. The requirement for an essentially convection-free system was met by use of the vertical furnace with the heat source over the heat sink, as well as by use of the small diameter ingots. In addition, by selection of tin-rich Pb-Sn alloys, the diffusion boundary layer (lead-rich) was denser than the bulk liquid and would not cause convection. The only apparent driving force for convection in this system was the small transverse temperature gradient resulting from heat flow into the samples from the furnace. Such convection must have been small, however, since 1) no temperature fluctuations in the melt were noted in the recordings, which would have indicated turbulent convection, and 2) experimental results obtained and described below could not have been achieved in presence of significant convection. Ingot Preparation. Pb-Sn alloys ranging from 12 to 26 at. pct Pb were prepared from high-purity lead and tin (99.9999 pct pure metal). Each alloy was prepared by first melting the pure metals in the proper ratio in air, in a Pyrex container. The melt was then stirred thoroughly with a graphite rod and cast into a preheated graphite mold. Ingots were then prepared from these castings for use in the actual experiments; each ingot consisted of a rod of alloy, 15 cm long in a 25-cm-long transparent fused-silica tube, 0.3 cm ID and 0.06 cm wall thickness. One chromel-alumel thermocouple, made with 0.004-in.-diam wire and protected by a two-hole alumina tube, was inserted into each ingot. The 1.5 cm of the thermocouple nearest the bead were protruding from the alumina tube and were coated with a very thin layer of boron nitride paste which provided electrical insulation while allowing good heat conduction. The electrically welded junction size was about that of each wire and the cross section of the two wires represented about 0.3 pct of the sample cross section. Including the coating, the thermocouple cross section still represented less than 0.5 pct of the ingot cross

Jan 1, 1968

By D. A. Wilson

A cyclic leaching process was developed for selectively leaching and recovering cadmium from nickel-cadmium scrap battery waste. The six major steps in the process are the following: (1) washing the plates to remove KOH electrolyte, (2) roasting at 550° to 600° C to oxidize metallic cadmium and decompose cadmium and nickel salts, (3) leaching with an ammonium nitrate solution, (4) precipitation of the leached cadmium from solution as cadmium carbonate using CO2 gas, (5) removal of CO2 from the lixiviator by adjusting to pH 4.5, heating, and evacuating the system, and (6) removal of small amounts of leached nickel from the lixiviator using a solvent extraction technique. The regenerated lixiviator is then recycled to leach additional plates. Cadmium extraction was 94 percent and the cadmium carbonate product contained 0.14 percent nickel and 0.12 percent cobalt impurity. The leached plates were smelted to a high nickel-low iron alloy with no detectable amounts of cadmium.

Jan 1, 1971

By Jean-Sébastien Lambert, Joseph Kabuya, Richard Simon

Managing a highwall failure risk in an open pit mine by controlling and mitigating the impact of vibrations produced by blasting operations is key to achieving safe and cost-effective operations. The impetus behind this study was the risk of multiple bench failures in an open pit mine that was detected by Slope Stability Radar (SSR) following blasting at the foot of a highwall. The unstable high wall was over 140 meters(459.3 ft)high and 200 meters(656.2 ft)wide. The quantity of associated material was estimated at 3,000,000 metric tons(3,306,934 US tons). The overall slope angle was 44 degrees. In order to continue mining without causing the highwall to fail, this study was initiated as part of a risk management plan to mitigate this major risk by identifying mitigation measures related to blasting operations and assessing the response of the rock mass to each blast. Identifying blasting mitigation measures consisted of optimizing blasting parameters to avoid failure of the highwall. First, a signature hole operation was carried out to obtain seismic records that were georeferenced and associated with known single charges. The method used made it possible to determine the propagation velocity of the P-waves associated with the various lithologies studied and to calculate, from the geomechanical properties of the rock masses, the maximum peak particle velocities to be respected. Subsequently, the targeted area of operation was modelled with the I-Blast software in order to optimize the firing sequences to be used according to the different lithologies present. The model also made it possible to optimally predict the particle velocities associated with each blast and ensure compliance with the previously determined peak particle velocity limits. The assessment of the rock mass’s response using SSR consisted of defining alarm thresholds and an intervention plan for various possible alarms as well as quantifying the damage to the highwall from blasting. Controlling the impact of blast vibrations on the highwall’s stability was successful, as the mitigation measures used during mining did not accelerate the highwall’s movement. No upward trend in the stabilization time of the rock mass was observed by the SSR after each blast. Post-blast geotechnical inspections and analysis of post-blast deformations in the highwall also did not reveal significant damage to the highwall as a direct consequence of the blasting.

By J. M. Ortiz

Grade control and short-term planning are usually based on the samples obtained from blastholes. These samples may carry a large sampling and sample preparation error. At El Tesoro copper mine in northern Chile, an advance drilling grid is used for short-term planning and grade control. These drill holes are sampled well in advance, and a short-term model that incorporates several variables and sophisticated estimation methods can be prepared for decisionmaking. An additional advantage of the advance drilling samples is that reverse circulation can be used instead of conventional down-the-hole equipment, and a very careful sampling and sample preparation process can be implemented, reducing the total sampling error. Advance drilling can be performed on a wider grid than blasthole drilling, hence the decision about the grid requires assessing the economic benefit of different sampling grids. Furthermore, this process allows the cost of poor sampling and the effect of different estimation procedures to be quantified. We demonstrate the optimization of the drilling grid for short-term planning and grade control at El Tesoro mine by means of the economic evaluation of the performance of different drilling grids, with different drilling techniques (which differ in the sampling error). The methodology is based on creating dense (exhaustive) geostatistical simulations of the grade distribution over a volume defined for a production period in respect of the geological model, and assuming each simulation as the true grade distribution. Then, samples are obtained from the exhaustive simulations at a spacing similar to the advance grid to be evaluated, and a sampling error is added. The short-term estimation procedures used on the mine are applied to determine the destination of each block and the profit obtained. This profit can be compared with the maximum profit (unachievable) and with the profit under different sampling errors and grids. The results show that the current 8 x 8 m drilling grid is appropriate and by reducing the sampling error, misclassification is also reduced, leading to an increase in profit of about US$ 5 million in 4 years.

Jan 1, 2012