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By R. D. Willette

The Hector Mine deposit in the California Mojave Desert has a magnesium-rich clay that formed when lithium and fluorine were introduced into isolated fine lacustrine volcanic sediment during the Pliocene. The intensely deformed deposit has been supplying the highest grade thixotropic clay to the coatings industry for over half a century. A thixotropic clay displays the property of changing from a gel to a sol when shaken, and increases in strength upon standing.

Jan 1, 1995

By J. C. May, G. M. Elliott, J. J. Brady

Increased clearance was required in two railroad tunnels that were built about the time of the Civil War. Clearance infringements, whether they be excavation tights or caused by ice accumulation, reduce tunnel serviceability. Achieving increased clearance often means disturbing the ground and old ground support structures. Access and transportation needs dictate how and when the work can be carried out, and strongly influence the design approach and the methods used by the contractor to execute the work. This paper explores the pertinent considerations of the owner, the designer, the field inspection team, and the contractor in bringing this project to a successful conclusion.

Jan 1, 1997

By J. D. Raulerson, R. P. Farias, G. A. Gruber

A flotation process has been developed to successfully treat ore from the Santo Domingo phosphate deposit in Baja California Sur. The ore contained less than 4% P2O5 with quartz, silicates, and carbonates as gangue minerals. Flotation of the low- grade feed in seawater required that the conventional Crago process, comprising direct anionic flotation, deoiling, and inverse cationic flotation, be augmented by an anionic cleaner flotation step, phosphate depression, and a calcite flotation step.

Jan 1, 1988

By Silvia H. M. Grimaldi, Afonso H. Martins

The scope of this experimental work was to study the yttrium extraction and stripping behaviour in a solvent extraction system with mono(2-ethylhexyl)2-ethylhexylphosphonic acid (IONQUEST 801) in a chloride system The study was performed for only one contact between organic and aqueous phases The experiments were carried out according to a factorial design. Due to the statistical analysis and its experimental proof, the optimum conditions for maximum yttrium loading into the organic phase of the extraction stage were 16 minutes for time of contact between phases, 980 rpm of stirring intensity and pH=2.3 for the aqueous phase of the sovent extraction system. The optimized experimental conditions by the statistical approach for the stripping stage were: time of contact between phases equal to 20 minutes, 1050 rpm of stirring intensity and 1.75 M HCI into the stripping aqueous solution.

Jan 1, 1995

By David A. Roberts, Edward J. Cording, James W. Mahar, Robert A. Robinson, Noppadol Phienweja, Harvey W. Parker

Horizontal inclinometer and deflectometer casings were used to measure deformations up to 15.2 m (50 ft) ahead of and adjacent to the heading in highly fractured and sheared shales at the Stillwater Tunnel. The measurements were compared with borehole extensometer and tape extensometer deformations to evaluate ground movements in advance of, adjacent to, and behind an advancing tunnel heading. Ground deformations of up to 127 mm (5 in.) occurred during passage of the innovative "walking blade-gripper" TBM. Deformations were compared with curvometer/distometer and vibrating wire strain gage data from steel ribs to assess rock-support interaction.

Jan 1, 1985

By Venkata S. Vutukuri

Assuming a number of discrete leakage paths and treating the airflow through leaky duct line as a series-parallel combination of airflows along the duct and through leakage paths, exact solutions for auxiliary ventilation problems can be obtained. A computer program "SEGMENT'' has been written to solve problems using this method. However, most of the investigators have treated the duct lines with a uniformly distributed leakage and many have derived formulas assuming various boundary conditions and levels of simplification for the design of a simple auxiliary ventilation system An appraisal of accuracy of the various formulas has been conducted using the results from the program "SEGMENT' as benchmark and the formulas which give accurate results have been identified. The ranges of application for all the formulas have also been determined for 5 %error.

Jan 1, 1993

By William Mark Hart

Newmont Mining's executive management launched an initiative in 1999 that was designed to engage the entire workforce in a continuous effort to systematically drive inefficiency out of the corporation. Built on a foundation of teams and teamwork, Gold Medal Performance (GMP) has had a significant and positive impact on the reduction of costs. At the same time, it has increased productivity, improved cash flow, and helped Newmont to further enhance health and safety programs. Currently, more than a hundred teams are working on improving line-balancing production and external communications at all levels of the corporation. The training and rigorous set of tools avail- able to and used by these teams were designed to help them improve communications, identify inefficiencies and their financial impact, develop and implement solutions, and finally, to measure the results of the process enhancement. GMP harnesses the energy, creativity, and productivity of the entire workforce.

Jan 1, 2001

By D. Greene

The close integration of mine planning and mine operation continues to be the goal of mine operators. Depending upon the complexity, size and sophistication of the mine, limited success has been achieved in this area. Despite tremendous strides in the development of computer-aided mine planning, digital plans must usually be converted to error-prone paper maps and physical ground surveys for actual excavation and reclamation. However, advances in global positioning systems (GPSs), operator displays and mobile computers now enable equipment operators to work directly from on-board digital plans. A computer-aided earthmoving system (CAES) offers reduced survey costs, faster field transition time and improved excavation accuracy, coupled with faster, more informed decision making regarding key mining operations.

Jan 1, 2000

By V. J. Matta, A. A. Pincheira, I. A. Reghezza, Ch. J. Vergara

The growth of solvent extraction in Chile has been astonishing during the last years and has been established as a very successful technology. However, there are still limitations that must be improved, mainly, the problem of carry over from one phase to the other and the losses of organic reagent associated with the crud formation. These are problems that our company has been taking care, solving them with high efficiency and low costs, allowing important increases in the copper output of our plants and capital savings by means of the optimization of the use of nonproductive units in the SX plants.

Jan 1, 1998

By J. B. Pautler, A. E. Gross, M. G. Strominger

The U.S. Bureau of Mines research on the use of cement as an agglomeration aid allowed precious metals heap leaching to become an economically viable method of precious metal recovery during the 1980's. However, many agglomerated ore bodies still exhibited poor heap/agglomerate strength. Precious metal recovery was often too slow or required prohibitively high levels of cement to be economically sound. Problems with heap ponding, blinding, and solution channeling and "wash-out" indicated that there was a need within the industry to improve on existing agglomeration technology. An in-depth research effort was undertaken to satisfy this need. Three years of research led to a patent on the use of vinyl addition polymers as effective agglomeration aids. A close working relationship between Brewer Gold and Nalco Chemical Company aided in the development of this program. This paper details the pilot test work, the full-scale evaluation at Brewer Gold Company, and conclusions.

Jan 1, 1990

By James Wm. White

Mine management now recognizes the value of computer-based truck-shovel dispatching in open pit mines. The key tangible benefits are substantial productivity increases with a given fleet of equipment or, alternately, significant reductions in equipment required to meet production quotas. In this work, we review the literature, report on efficient, optimal algorithms for haul truck dispatching in real-time, and briefly discuss methods used by various mines to evaluate productivity improvements over manual methods. We also present actual results obtained at thirteen mining operations around the world.

Jan 1, 1992

By Ryan Lemmon

Belt turnovers are commonly used in conveyors to rotate the belt so that the clean side of the belt contacts the return idlers. The belt turnover length has traditionally been sized on only the twisting stresses. However, belt turnovers are also subjected to bending stresses due to the weight of the belt. Although bending stresses have in the past been ignored, these stresses are significant and should not be neglected. This paper quantifies and presents a method for calculated twisting and bending stresses and also the belt sag.

Jan 1, 2002

By J. A. Herbst, C Lo. Y, Z. Rogovin

The identification and quantification of incipient overload conditions in mills have recently been found to be very significant in the design of tumbling grinding mills. To investigate these phenomena, a series of experiments was conducted in a Plexiglas mill operated in both dry and wet modes. For on-stream measurement of the mill charge weight, volumetric filling, dynamic angle of repose, and mill power, an electronic system was developed. The mill was filled to various levels with 19.1-mm (3/4-in.) ceramic balls as grinding media. As feed material, grindable limestone or 3.2-mm (1/8-in.) nongrinding ceramic balls were fed at various steady-state rates to determine the incipient overload conditions. The prediction of overload has apparently been reduced to predicting the feed rate that results in 50% mill filling.

Jan 1, 1988

By D. R. Zhu, H. S. Chiang, Y. M. Jiang, S. S. Peng

Two types of underground tests on three types of shield supports, 2-leg, 4-leg, and chock shield, were con- ducted to measure the horizontal movement of the canopy against the immediate roof. In no friction tests, steel rollers were placed between roof and canopy top, while in friction tests normal direct contact was used. Results indicate that the canopy for 2-leg shields always moves forward during setting, whereas there was no forward movement for 4-leg or chock shields. Based on the test results, a model for active horizontal force was proposed.

Jan 1, 1990

By S. K. Kawatra, R. A. Seitz

Nonpolar hydrocarbon oils are commonly used in the flotation of minerals to fulfill a number of roles. These roles include reducing overall reagent costs by replacing part of the collector addition, improving coarse particle recovery without reducing selectivity, as well as several others. This paper will cover the types of oils which are available, their physical and chemical characteristics, and the effect of these characteristics on the function of hydrocarbon oils in flotation. In addition, techniques for improving the behavior of oils will be discussed.

Jan 1, 1986

By R. C. Ford

The advent of solvent extraction-electrowinning (SX-EW) technology for recovery of copper from low grade oxide ores has extended the operational lives of many historic mines in the western United States, and made many other orebodies economically viable worldwide. Many of these operations are mature and face closure within the next decade, depending on market conditions. Closure of a large copper heap leach operation has not been undertaken, and differs in some important chemical respects from closure of gold leach pads. Challenges for closure include prediction of solution chemistry and draindown characteristics, determining the benefit of cover placement in semi-arid climates and evaluation of solution management strategies once the economics of copper recovery are no longer favorable. This paper discusses issues pertinent to copper heap closure in semi-arid and arid climates, and strategies for their management.

Jan 1, 2000

By J. Stachurski, N. A. Abdel-Khalek

The objective of this investigation was to compare the results of countercurrent, column cell flotation vs. conventional (mechanical) cell flotation for the cleaning of a sulfur ore (-0.5 mm, 27.43% S) and its discrete size fractions. The tests were carried out using diesel oil as a collector and alcohol as a frother. Generally, column flotation produced concentrates of higher grade. For example, column cell flotation produced a nonwashed concentrate of 65.3% S with a recovery of 84.1%. However, conventional cell flotation produced a rougher concentrate of lower grade (57.0% S) and higher recovery (92.5%). At a superficial-wash water velocity of 0.265 cm/sec, the column product grade increased to 76.4% S, with a slightly lower recovery (80.3%). However, a concentrate with a similar recovery but a lower grade (74% S) than that of the washed product was obtained after three cleaning stages with the conventional cell. The column gave superior results for the flotation of fine and ultrafine particles.

Jan 1, 1994

By R. Hogg, E. Kaya

The presence of agglomerated particles in airborne dust in coal mines has been confirmed by SEM examination of static samples collected on substrates. In addition, the effect of agglomerated particles on the performance of cascade impactors and cyclone- type personal samplers has been studied. Simple procedures have been developed for evaluating the extent of agglomeration in air-borne dust by comparing the observed size- selectivity of the sampling devices with that expected under idealized conditions. Applications of these techniques in the laboratory and in underground mines are discussed.

Jan 1, 1992

By J. K. Mokka, P. D. Rao, H. K. Lin

Extensive exploration has resulted in delineation of a massive sulfide district on the north flank of the east-central Alaska range. The district covers approximately 400 mi2 and contains numerous stratiform, transposed and some replacement type sulfide deposits ranging in size from less than 1 million st to 20 million st. Five types of ores were sampled for the study. Mineralogical analysis revealed that the minerals are too fine grained for conventional grinding and beneficiation. Hydrometallurgical studies were conducted using ferric chloride as a lixiviant. Ore microscopic studies as well as electron microprobe analyses of minerals in the raw samples and leach residues explained the low recoveries for certain elements as well as sources of impurities that need to be eliminated from the process streams.

Jan 1, 1992

By A. W. Khair, J. A. Organiscak, M. Ahmad

This paper describes research that seas conducted on bit wear and respirable-dust generation. The investigation was performed by the US Bureau of Mines (USBM) and West Virginia University (WVU), a member of the Generic Technology Center on Respirable Dust. The USBM investigated wear, energy and dust characteristics of various conical bit designs when cutting rock. WVU studied the functional relationships between wear, cutting force, energy and dust of one type of conical bit cutting coal. The objective of the USBM study was to identify qualitative bit-selection guidelines. The objective of WVU's research was to determine optimum bit-replacement guidelines. Both research studies found that bit geometry (a function of bit design and wear) influences energy consumption and dust generation. Bit selection and replacement recommendations are given.

Jan 1, 1996