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By Denise Cristina Oliveira Nascimento

Environmental considerations in addition to technical, economical and societal benefits are increasingly promoting the substitution of natural fibers for glass fiber in polymer matrix composites. However, natural fibers are heterogeneous in their dimensions, specially the cross section, which plays an important role in their mechanical strength. It has been found that the equivalent diameter of fibers such as sisal, ramie, pineapple and curaua correlates to different levels of tensile resistance. Piassava is a promising stiff natural fiber for composite reinforcement. In this work, a statistical analysis of tensile strength of piassava fibers using the Weibull methodology was performed. An attempt to correlate the fiber strength, obtained in tensile tests, with the diameter, precisely measured by means of a profile projector, was carried out. The results revealed an inverse dependence between the piassava fiber diameter and corresponding tensile strength. Fracture tip observation by SEM suggested a possible mechanism that could justify this inverse correlation.

Jan 1, 2010

By Russell J. Foster

Public awareness of, and involvement in, recycling has increased significantly in recent years. Nevertheless, recycling is generally perceived as a new development, and is familiar only in the context of municipal solid waste management. The actual magnitude and scope of metals recycling in the United States have gone virtually unnoticed. Over time, both the quantitative and qualitative aspects of secondary metals recovery and reuse have changed substantially, while the attendant regulations have become increasingly stringent. This U.S. Bureau of Mines report examines trends and developments in major metal demand and recycling, and analyzes the possible impacts of regulations with regard to recycling activities.

Jan 1, 1994

By J. Searra, M. Aboagye

"For new mining projects or for medium- to long-term areas of existing mines, drilling data is invariably on a relatively large grid. Direct estimates for selective mining units (SMUs), and also for much larger block units, will then be smoothed due to the information effects and the high error variance.The difficulty is that ultimately, during mining, selection will be done on the basis of SMUs on the final close-spaced data grid (grade control), which will then be available, i.e. the actual selection will be more efficient, with fewer misclassifications. However, this ultimate mining position is unknown at the project feasibility stage and therefore has to be estimated. This estimation is required because any cash flow calculations made on the basis of the smoothed estimates will obviously misrepresent the overall economic value of the project, i.e. the average grade of blocks above cut-off will be underestimated and the tonnage overestimated for cut-off grades below the average grade of the orebody. Similarly, unsmoothed estimates will be conditionally biased and will give even worse results, particularly in local areas of short- and medium-term planning or mining.This paper presents a case study of indirect post-processing and proportional modelling of recoverable resources designed for mediumand long-term mine planning at the Gold Fields’ Tarkwa Mine in Ghana. The case study compares long-term indirect recoverable mineral resource estimates based on typical widely spaced feasibility data to the corresponding production grade control model as well as the mine production. The paper also proposes certain critical regression slope and kriging efficiency control limits to avoid inefficient medium- to longterm recoverable estimates, and highlights the danger of accepting block estimates that have a slope of regression less than 0.5."

Jan 1, 2015

By A. H. G. Mitchell

Most, if not all, of the six recognised post-Cretaceous, predominantly andesitic mineralised belts in the region are now thought to be subduction-related magmatic arcs. The Inner Carpathian arc and the Eastern Bosnia or Drina-Rhodope arc host numerous vein and replacement deposits with epithermal features and Zn-Pb+/-Ag as the predominant economic minerals. In contrast, the south Apuseni Mountains have produced over 1 600 t Au from epithermal veins but very little Zn-Pb. Recent age determinations and geophysical data from the Baia Mare district of the Inner Carpathians suggest that mineralisation succeeded volcanism by 1-2 m.y. and accompanied crustal extension and the cooling of a large, mushroom-shaped pluton whose boundaries define the mineral district. In the south Apuseni district, mineralisation can be explained by mixing of meteoric with low-salinity metamorphic water expelled during intrusion of mafic rocks into the middle or lower crust. The more continental or cratonic crust in the Drina-Rhodope and Inner Carpathian arcs precluded the input of low-salinity, Au-bearing metamorphic water; the Zn-Pb deposits formed where convecting meteoric water mixed with saline water, possibly introduced through carbonate rocks in the basement

Aug 1, 1996

Study on Mineral Processing of Refractory Copper-Nickel Ore

Sep 13, 2010

By José Cuadros

"El presente trabajo señala el proceso de evolución del método de minado en la mina Chupa, perteneciente a la unidad minera de Iscaycruz. La evolución del método de minado se determinó por la búsqueda de mejores condiciones de seguridad y eficiencia en la operación. En ese sentido, los resultados logrados con cada una de las alternativas de minado por subniveles, indica que se ha logrado optimizar las diferentes variables mineras y cumplir con el plan estratégico de Empresa Minera Iscaycruz S.A. (EMISA). Para cumplir con el citado plan estratégico, se debe optimizar el método de minado de Chupa, a través de una mayor producción a un menor costo,así como del aprovecho de las labores de desarrollo y preparación ejecutadas según el planeamiento inicial del minado. Por ello, la secuencia del avance del minado y la reestructuración del sistema de relleno de la mina son los aspectos importantes para lograr este objetivo. "

Jul 31, 2003

By Sam S. Taylor

Disposal of brines produced with crude petroleum and natural gas is a continually increasing problem. The necessity for studying this problem has been realized more generally in recent years, and in August 1934 an agreement was made between the Kansas State Board of Health and the United States Bureau of Mines to conduct a cooperative technical study of methods of brine disposal. To date one paper in the technical press4/ and three reports5/6/ have been published in which are given results of studies carried on under this cooperative agreement. In the Mid-Continent fields, the methods used most generally for handling oil-field brines are: (1) Impounding in evaporation ponds; (2) controlled diversion into surface streams; and (3) injection into subsurface formations through wells assigned for this purpose. Various States recognize one or more of the methods as legally authorized procedure. Impounding brine in ponds and solar evaporation have proved inadequate as a general rule, owing, usually, to the porous nature of the soil, the low rate of evaporation, or both. Diversion, of

Jan 1, 1937

By Sam S. Taylor

Disposal of brines produced with crude petroleum and natural gas is a continually increasing problem. The necessity for studying this problem has been realized more generally in recent years, and in August 1934 an agreement was made between the Kansas State Board of Health and the United States Bureau of Mines to conduct a cooperative technical study of methods of brine disposal. To date one paper in the technical press4/ and three reports5/6/ 7/ have been published in which are given results of studies carried on under this cooperative agreement. In the Mid-Continent fields, the methods used most generally for handling oil-field brines are: (1) Impounding in evaporation ponds; (2) controlled diversion into surface streams; and (3) injection into subsurface formations through wells assigned for this purpose. Various States recognize one or more of the methods as legally authorized procedure. Impounding brine in ponds and solar evaporation have proved inadequate as a general rule, owing, usually, to the porous nature of the soil, the low rate of evaporation, or both. Diversion of

Jan 1, 1937

By Robert S. Archer

THE proper material of construction for a given purpose is that material which meets the requirements satisfactorily at the lowest ultirnatc cost. It is consistent with this principle that most aluminum castings are made of an alloy containing about 8 per cent. copper. This alloy possesses mechanical properties satisfactory for general engineering purposes together with manufacturing characteristics leading to the production of finished castings at low cost. It is to the aluminum industry what gray iron is to the iron and steel industry. Just as some services require "semi-steel," malleable castings or steel castings instead of gray iron, there is a certain and growing demand for aluminum castings of superior strength or ductility, or both. Since the beginning of .the industry producers and others have sought to develop alloys or processes by which such castings could be made. Out of these efforts have emerged many alloy compositions and special processes, of which only a few have had sufficient merit to survive. It is the purpose of this paper to describe those which seem to the authors to offer the greatest promise for the production on a commercial scale of aluminum castings of superior mechanical properties, with special reference to heat-treated castings. The suitability of an alloy or process for actual manufacture is affected by so many factors that the problem of appraisal is not a simple one. Since this is such an important part of the whole subject it is proposed to discuss briefly some of the requirements. The final verdict is of course the result of commercial trial and experience. It will therefore, perhaps, be profitable to employ a somewhat historical method of treatment in discussing the subject of alloy development. The alloys or processes to be used in the production of aluminum castings are to be considered from the standpoint of their effects on both the utility and the cost of the finished casting. Specific gravity and mechanical properties come under the first head, while the properties

Jan 1, 1927

By S. D. Bearden

Color enhances expression and communication in all physical objects experienced in life. Pigments provide color and in some applications have a specific additional function. Natural iron oxides are widely distributed throughout the world but only a few deposits are sufficiently pure and possess acceptable color and brightness properties to merit their processing into pigment form. Ochre, the common name for goethite ore, is the best and most under used material in the buff colored pigment market. The geological occurrence of ochre in the basal Shady Formation of the Cartersville Mining District (Georgia) is described. Exploration, processing, and product applications of New Riverside Ochre Company, Inc. are discussed. An overview of the worldwide pigment market is presented with emphasis placed upon the North American activity in iron oxide production and application. The purpose of this paper is to increase the awareness of ochre and its potential market in the colored iron oxide pigment industry, encourage research on the origin of ochre deposits, and stimulate interest in new applications of this unique substance.

Feb 27, 2013

By Antti Porvali, Vivek Agarwal, Mari Lundström

Hydrometallurgical recovery of rare earth elements (REE) from NiMH battery waste can be performed using sulfuric acid leaching followed by selective precipitation as double salt (REENa(SO4)2·H2O) by adding Na2SO4 as a precipitating agent. The formed double salts can then be further converted with NaOH solution to form REE hydroxides. However, present literature has paid little attention to how to minimize the consumption of reagents in this recovery process. In the current study, a process model was built using HSC Sim software, and metamodeling of the simulated flowsheet was conducted with the design of experiments (DOE), after which the basic functionality of the flowsheet was verified by experimental work, starting from sulfuric acid leaching of spent batteries. As the process is based on chemical circulation internally in the process, the objective was to investigate the accumulation of the elements in solution, specifically Na+ , K+ , SO4 2− ions and impurities liberated in the NaOH conversion step. It was found out that metamodeling could be utilized in obtaining first estimate of the process behavior, prior to any experiments. Flowsheet functionality with circulated solution was confirmed, obtaining at best 96.9% La recovery.

By Antti Porvali, Vivek Agarwal, Mari Lundström

Hydrometallurgical recovery of rare earth elements (REE) from NiMH battery waste can be performed using sulfuric acid leaching followed by selective precipitation as double salt (REENa(SO4)2·H2O) by adding Na2SO4 as a precipitating agent. The formed double salts can then be further converted with NaOH solution to form REE hydroxides. However, present literature has paid little attention to how to minimize the consumption of reagents in this recovery process. In the current study, a process model was built using HSC Sim software, and metamodeling of the simulated flowsheet was conducted with the design of experiments (DOE), after which the basic functionality of the flowsheet was verified by experimental work, starting from sulfuric acid leaching of spent batteries. As the process is based on chemical circulation internally in the process, the objective was to investigate the accumulation of the elements in solution, specifically Na+ , K+ , SO4 2− ions and impurities liberated in the NaOH conversion step. It was found out that metamodeling could be utilized in obtaining first estimate of the process behavior, prior to any experiments. Flowsheet functionality with circulated solution was confirmed, obtaining at best 96.9% La recovery.

By F. W. Wood

The Bureau of Mines has sought clarification of the Ti-TiN system by studying the phases formed by diffusion reactions between titanium and titanium nitride. Reaction couples were prepared by embedding pockets of TiN powder in arc-melted buttons of titanium. Specimens were vacuum annealed at nominal temperatures of 800°, 950°, 1,200°, and 1,500° C. Metallographically mounted cross sections from reacted specimens and from some that were not annealed were examined optically, with an electron microprobe, with an election microscope, and by X-ray diffraction. Each annealed specimen contained a segregated core primarily of d-phase material, an ?-phase diffusion layer, an a-phase diffusion layer, and host metal. On the basis of corresponding microprobe analyses, and considering results of certain other research, a new phase diagram is proposed. It contains no qualitative innovations, only quantitative adjustments. Results were also analyzed from the viewpoint of diffusion behavior. Diffusion coefficients calculated for the ? phase were sufficiently scattered that the parameters are very tentative. Nevertheless, the diffusion behavior reported is in reasonable agreement with one of two prior studies if it is assumed that the earlier investigators were mistaken in their identification of the nitride phase in which the diffusion occurred.

Jan 1, 1974

By Lok M. Sharma

"Construction of a new bridge in a seismically sensitive area requires careful assessment of earthquake impact on the serviceability of the facility. Not only is the superstructure vulnerable, the foundations play a key role in the bridge’s survivability. A new bridge in eastern part of the state of Missouri in the U.S.A. is located in a seismically active area and hence subject to additional thrust on the foundations and superstructure and potential damage due to liquefaction. An eleven span bridge with foundation soils varying from shallow bedrock to over 30 m (100 feet) overburden soils were considered for the bridge support piers. Two of the bridge support bents located within the flood plain area through over 30m (100 feet) of alluvial deposits were considered most affected by an earthquake event due to the additional thrust and lateral ground spreading. This paper describes the determination of site specific seismic hazard, numerical modelling of the foundation system, and methodology of dynamic analyses, effects of lateral spreading and liquefaction potential on bridge support bents. From numerical modelling using FLAC, the increase in thrust on piers and deformations were computed to predict the behavior of the foundations.INTRODUCTIONA newly constructed bridge on route US 40 crosses the Missouri River west of St. Louis, Missouri and upstream of Mississippi River in mid-west USA. The west abutment area has near surface bedrock while the east abutment area has overburden deposits over 30m (100 feet) thick, mostly river sediments comprising of silts, lean clays and sands overlying bedrock. Softer layers of silts and sands in the east river bank area are assessed to be liquefiable during a high magnitude earthquake event. St Louis area has a potential for a high magnitude earthquake due to the New Madrid Fault some 160km (100 miles) south. The bridge foundations were designed as drilled piers, 2 m (8 feet) in diameter and socketed into the bedrock. Bents No. 10 and 11, located in the lower flood plain area of the river, are considered to be most affected by a seismic event.In order to perform dynamic analyses of the foundations, earthquake ground motion time history was developed for the specific site using a Probabilistic Seismic Hazard Analysis (PSHA) and selecting and scaling of a recorded time history. Relying on the U.S. Geological Survey (USGS) Earthquake Hazard Program for the PSHA and AASHTO Guide Specifications for LRFD Seismic Bridge Design, spectral acceleration values for the site were developed. The spectral acceleration values were for a 7 percent probability of exceedance in 75 years (1000 year return). Numerical modelling using FLAC computer program was performed. This paper presents the seismic design parameters, methodology used in the dynamic analyses, static and dynamic analyses, impact and mitigation of liquefaction on Bents 10 and 11 and the abutment fills, and effect of lateral spreading on the foundations in the lower flood plain area of the bridge. From the numerical modelling, increase in thrusts on pier foundations and estimated deformation were computed."

Jan 1, 2017

Urban development to the south of Sydney is approaching areas of current and proposed coal mining. Already some structures and residential areas are affected by mining subsidence.Subsidence resulting from either conventional pillar extraction methods or longwall mining has been monitored for 15 years to enable the characteristics of the surface deformation to be determined.The vertical and horizontal displacements of survey stations on the surface are monitored and the results arc used to calculate subsidence, changes in slope of the surface, curvatures along the subsidence profile, and the ensile and compressive strains. These features are in turn related to the underground extraction to give a description of surface subsidence and the development of subsidence with time.Subsidence investigations have been carried out over all or part of the workings of six collieries in the Southern Coalfield.Two case histories illustrate the procedure in the investigation of subsidence phenomena. The first example is the study of the subsidence over a series of longwall panels in one seam and the second is a study of subsidence over pillar extraction in two seams one above the other. From the results of the investigations the effects of panel widths on subsidence are determined.This and other information assists mine planning in areas where surface movement and deformation are important considerations.

Jan 1, 1980

By J. Douglas Causey

The Bureau of Mines conducted mineral investigations of the Peace Rock and Deadwood River roadless areas in Idaho, in 1992. Literature research was done by the Idaho Geological Survey. The study areas contain black sand placers (thorium, columbium, tantalum, titanium, uranium, and rare earth elements), gold, and molybdenum prospects. Except for unrecorded placer gold, there has been no mineral production from the areas. No mineral resources were delineated, but a multi-million tonne molybdenum resource is in the Big Pine Creek area and a 142 million m' black sand deposit is in the Stolle Meadows, Peace Valley, and Deadwood River areas. The Deadwood mine produced zinc, lead, and silver. There are six mining districts in and adjoining the areas; Warm Lake, Deadwood, Garden Valley/Lowman, Banner, Summit Flat, and Grimes Pass. Few claims, mostly placer, were active in the study area in 1992. The study areas are underlain by granitic rocks of the Idaho batholith. Most of the deposits are alluvial accumulations of heavy minerals weathered out of the Idaho batholith. Stockwork and narrow veins along shears account for the base and precious metal concentrations. Eleven prospects were examined. Workings consist of drill holes, pits and adits. Geothermal resources (hot springs) occur mainly along the Middle Fork Payette River; Vulcan Hot Springs is a designated Known Geothermal Resource Area. Sand and gravel resources are of local interest.

Jan 1, 1993

By Joe Roby

Rolling disc cutters are the business end of hard-rock and mixed-face tunnel boring machines (TBMs). Since their first successful employment on a TBM more than 50 years ago, disc cutter technology has constantly evolved, allowing modern TBMs to excavate very hard and abrasive rock efficiently. Disc cutters have also been employed successfully on earth pressure balance (EPB) and slurry machines, cutting rock under water and ground pressure. The range of materials excavated by machines today is broader, excavation rates are higher and cutter costs are lower than ever before, proving the value of investment in cutter development. Disc cutters are used on a range of tunneling equipment, from pipe jacked slurry micro-TBMs less than 1 m (3.3 ft) in diameter to 15 m (49 ft) in diameter, hard-rock boring TBMs. The geological conditions under which they are employed range from sands and gravels, with several bar of water pressure, to extremely hard, massive rock with UCS up to 420 MPa. Regardless of the type of machine or geology, one thing remains constant: changing worn out cutters is costly. When cutters must be changed in the middle of a tunnel, the contractor incurs the cost of downtime as well as the cost of refurbishing or replacing the cutters. In the case of catastrophic cutter failures, the project can be stopped completely for long periods, and the costs mount up rapidly while tunnel production is at a stand still. Catastrophic cutter failures include the occasion when hard-rock disc cutters are failed in groups (called a ?wipeout? phenomenon) and the operator fails to stop the machine, which results in severe damage to the cutterhead. The cause of this can be either an undetected failed cutter propagating damage to surrounding cutters or operator error in steering. Regardless of the cause, the resulting damage can take days or even weeks to repair. When cutters fail prematurely on EPB or slurry machines in certain geological conditions, it is impossible to evacuate the chamber and, therefore, impossible to get [ ] into the chamber to change the cutters. The solution is frequently an unplanned intervention shaft that must be sunk at great cost. The importance of being able to predict cutter life accurately, and in all geological conditions, cannot be overemphasized. For these reasons, cutters have been developed for specific machine types and sizes, as well as for specific geological operating conditions. Different size cutters are required for different size machines. For example, while 483- and 508-mm (19- and 20-in.) cutters are used on large diameter TBMs, it is impossible to employ cutters so large on a small micro-TBM. Also, the cutter must be designed for the specific geological conditions under which it will be operating. The disc cutter rings required to bore extremely hard rock are the most expensive of cutter rings. However, they provide little advantage in weaker rock formations where less expensive rings will do the job as well. It is important to choose the correct cutter for the machine and the geological conditions in order to get the best balance of cost and risk.

Jan 1, 2009

By R Tweedie

'The politics of mining in New Zealand' is a topic I chose myself because of its importance in the future of the New Zealand mining industry. There are many people in the industry who are cynical about politics, cynical about politicians and definitely cynical and often critical of political decisions. In fact, many industry people say they don't want to get involved in politics, they just want to get on with the business of exploration or mining. The point of my address is that politics is important and the industry cannot afford not to participate in the political process.

Jan 1, 1991

By Paul Laframboise, Nigel MacDonald, Mike Hallewell, Robert Thorpe

"Galmoy Mine, owned by Arcon Mines Limited, has operated since 1997, and is one of three operating lead/zinc mines in Ireland. Changes in ore type starting in mid 2002 created challenges to metallurgical operations at Galmoy. This resulted in unacceptable lead and zinc flotation performance, which prompted initiation of a formal plant review and a subsequent stabilization programme. This involved a structured review of operational practices, development of a new Standard Operating Procedure (SOP) which in turn led to significant changes in process control equipment needs in conjunction with extension of zinc flotation cell residence time.This paper will describe the metallurgy of the Galmoy operation. Reasons for the poor metallurgy experienced in 2002 will be described, as well as the solutions identified to overcome these problems. By the second quarter of 2003, these solutions had been implemented and recoveries had risen to record levels.INTRODUCTIONGeneralGalmoy Concentrator is located in County Kilkenny (Refer to Figure 1 below) and was constructed during 1996 and commissioned in 1997.The concentrator at Galmoy had been designed initially to treat 650,000 tonnes per annum of primarily CW ore type. The main mineral of economic significance was sphalerite (Typically 10 to 11% Zn) with some minor galena (0.7%Pb) in a dolomite (Magnesium Carbonate) host rock.The only other competing sulphide mineral was pyrite (Circa 3 to 5% Fe in Mill Feed. This CW ore type predominated the first 6 years of production, but in August 2002, the ore mineralogy changed due to significantly higher levels of pyrite rich G ore body being blended in with CW ore."

Jan 1, 2005

By Wilton Johnson

Native asphalt was produced by three companies in two States, Texas and Utah. Bituminous limestone, used primarily as a paving material for street and road repair, was produced by one firm, R. L. White Co., Uvalde County, TX. Gilsonite, a solidified hydrocarbon found only in Colorado and Utah, was mined by two firms, American Gilsonite Co., a division of Chevron Resources Co. (a subsidiary of Standard Oil Co. of California), and Ziegler Chemical and Mineral Corp. Hydrocarbon Mining Co. (a subsidiary of Oberon Oil Inc., a Utah corporation) closed its mining operation during the year.

Jan 1, 1988