Search Documents

By J. Kennedy

Rare Earths: Understanding The United States complete failure of status and relevance in Rare Earth Oxides, Elements and Alloys. Although rare earth oxides are strategic and critical in their own right, elements and alloys are even more important for the development of "Green Technologies" and advanced weapons systems. America does not have an active domestic source of rare earth oxides. America does not have any Heavy Rare Earth Elemental or Alloy capabilities. The magnitude of this failure continues to become more apparent as the manufacture of REO based electronics and magnetic components moves eastward towards China. China has succeeded in outmaneuvering The United States and the world in its quest to control the Rare Earth Oxides, Elements and Alloys, and the many industries dependent upon REO. What can be done?

Jan 1, 2010

By B. W. Cavender

"World-class manufacturing" (WCM) techniques can be applied in milling operations to substantially improve productivity and reduce costs. Through the use of "just-in-time" and "total quality control" practices, WCM methods establish an environment for continual and rapid improvement in all aspects of production operations, with particular gains in product quality, costs, flexibility, employee involvement, and responsiveness to customers. This paper examines WCM techniques that can be utilized specifically in the mill, and their influence on plant configuration, organization, and scheduling practices; equipment selection and maintenance methods; training; the role of supporting staff; and methods of data collection and analysis.

Jan 1, 1993

By Laurence M. Demers, Douglas C. Kuhn

It has been suggested that radicals on the surface of dust particles are key chemical factors in the pathophysiology which results from the occupational inhalation of coal and silica dust. In addition, oxygenated derivatives of arachidonic acid (eicosanoids) have been implicated as important biochemical mediators of mineral dust-induced lung disease through their role in bronchial and vascular smooth muscle reactivity, inflammation, and fibrosis. Therefore, we assessed eicosanoid production by the rat alveolar macrophage (AM) exposed in vitro to mineral dusts with varying surface chemical characteristics in order to determine if radicals associated with the mineral dub1 could influence the production of pro-inflammatory mediators in the lung environment. Rat AM were exposed to freshly fractured or "stale" bituminous coal dust, as well as untreated silica or silica calcined to 500°C and 1100°C. Prostaglandin E2 (PGE2) and thromboxane B2 (TxB2) levels in incubation medium were determined by specific radioimmunoassay. When AM were exposed to freshly fractured coal dust, PGE2 and TxB2 production were markedly increased. In contrast, exposure of AM to "stale" dust significantly reduced PGE2 and TxB2 production. In vitro exposure of AM to untreated silica resulted in a significant increase in PGE2 and TxB2 production compared to control. However, exposure of AM to silica calcined to 1100°C resulted in eicosanoid levels which were not significantly different from control. These findings suggest that radicals associated with respirable coal and silica particles may play a key role in the ability of mineral dust to activate AM eicosanoid production.

Jan 1, 1991

By Wenhua Li, Tsuyoshi Adachi

Resource nationalism is essentially mandatory government intervention in natural resources businesses by political or economic means in order to benefit the nation and the people. It is attacking the mining industry more and more rampantly by all kinds of means since the twenty-first century. Poor countries who count on a resource-led economic growth usually find themselves trapped into “resource curse”. The harmfulness of resource nationalism for investors is that one event can quickly escalate and lead to a chain of events which make projects commercially unavailable. In spite of historical and theoretical social investigations in the causes of resource nationalism, rare studies engaged in quantification of dominant parameters of it. The objective of this study is to find significant factors that dominate the occurrence of resource nationalism for important metal and energy resources producing countries and quantify their marginal effects. The study applies binary choice logit model for panel data using pooled method. One feature of the research is that binary data set of occurrence of resource nationalism are sorted out by authors referencing U.S. Geological Survey’s reports. The results indicate that high-technology export (% manufactured export), ores and metals exports (% merchandise exports), rule of law (world governance indicator), trade (% GDP), and natural resource rent except forest (% GDP ) dominant the occurrence of resource nationalism for high and upper middle income group countries; government effectiveness (world governance indicator), policy perception index (The Fraser Institute), high-technology export (% manufactured export), and mineral rent (% GDP) dominant the occurrence of resource nationalism for lower middle and low income countries. According to our model, probability of occurrence of resource nationalism in 90 countries are predicted. Top 10 risky countries in 2012 are estimated to be North Korea, India, Honduras, Indonesia, Kazakhstan, Burkina Faso, Mongolia, Cuba, Bolivia, and Peru. The study is a primary trial of researching on resource nationalism and provides some insights for theoretical building and simulation on the issue.

Jan 1, 2017

By H. Wagner

INTRODUCTION One of the most important tasks facing the opera¬tors of deep-level gold mines is supporting the roof strata in the immediate vicinity of the stope faces. Some of the deeper gold mines operate at depths ex¬ceeding 3.0 km; the extreme mining depths and the tabular nature of the gold-bearing reefs result in high stress concentrations at the abutments of the stope faces. These, in turn, lead to extensive fracturing of even the hardest quartzites. Although most of these fractures develop in a stable manner, there have been many instances where rock failure occurred suddenly, resulting in a considerable amount of damage to the underground workings. Such violent rock failures commonly are known as "rock bursts," and they are typical of many hard-rock mines that are operating at great depths. To safeguard mining personnel and equipment against the effects of stable and unstable rock failures, adequate support must be provided to the fractured roof as quickly and as effec¬tively as possible. Traditionally, timber props and timber packs have been utilized to provide roof support in gold mine stopes up to 1.5 m wide. Both methods of support suffer from the fundamental disadvantage of generating sup¬port only in reaction to movement of the strata. Since unrestrained strata movement often results in a break¬down of the frictional forces that preserve the stability of the intensely fractured roof strata, it is essential that stope supports have rapid load-bearing characteristics. An equally important requirement is that the roof sup¬ports be able to accommodate displacements of the rock mass. A third requirement of roof supports in gold mine stopes is that they must be able to accommodate the high rates of stope convergence typical of rock bursts. The hydraulic prop is the obvious choice for sup¬porting the stope faces in deep-level hard-rock mines. Since hydraulic props can be installed with a positive setting load, they can provide roof support that is independent of strata movement. By equipping the hydraulic props with yield valves, they meet the require¬ment of being able to accommodate rock-mass displace¬ments. However, the requirement of being able to accommodate high rates of stope convergence without overloading or damaging the rock strata was rather difficult to meet. The first introduction of hydraulic roof supports into gold mine stopes showed that conventional hy¬draulic props, such as those used in coal mines, were completely unsuitable for a number of reasons, in¬cluding: 1) Since drilling and blasting are used to break the ore in gold mine stopes, supports installed close enough to be effective are exposed to the vigor of the blast. Conventional coal-mining props suffered extensive blast damage, despite being protected by a blast barricade. 2) The environmental conditions in gold mine stopes favor corrosion. The high quartz content and the abrasiveness of the ore further aggravate the problem by damaging the protective coatings on the hydraulic surfaces. Simply changing the design of gold mine props to have the piston project from the bottom rather than from the top resulted in dramatic improvements in the service life of the props. The improvement was attributable to external water in the stope washing the fine quartz grit away from the hydraulic surfaces, rather than concentrating the particles between the cylinder and piston of the prop. 3) The most obvious deficiency of conventional coal mining props was their inability to yield rapidly enough to accommodate the high convergence rates of rock bursts without overloading the supports. As a result of the first disappointing results with hydraulic supports in narrow hard-rock stopes mined by drilling and blasting, a comprehensive research and development program was undertaken. The hydraulic props resulting from several years of research and exten¬sive field trials are described herein. To date (1978), more than 130,000 of these props have been manufac¬tured and used successfully in a number of mines and under a variety of geological conditions. Although many of the detailed specifications are directed spe¬cifically to gold mining conditions, there are a number of points that are of general importance in the design of underground support systems for tabular excavations in hard-rock mines of any type. SPECIFICATIONS FOR RAPID-YIELDING PROPS Yield Requirements The yield requirements for hydraulic props in deep¬level hard-rock gold mines are summarized in the fol¬lowing paragraphs. Slow Yield Load: The design of the yield valve must allow the yield load to be preset to between 300 and 400 kN. This flexibility is necessary to account for the differences in the strength properties of the roof and floor strata. Drop in Load Under Slow Yield: The drop in sup¬port load during a slow yield should be as small as possible, but it should not exceed 5% of the slow-yield load. Rapid-Yield Load: The load exerted by the prop during periods of rapid stope convergence should be as close as possible to the slow-yield load. The rapid-yield load should not exceed the slow-yield load by more than 15% at yield rates of 1.0 m/s. The limitation of the upper valve of the yield load is important; it deter¬mines the hydraulic performance of the yield valve. The hydraulic props that satisfy this criterion have performed well, even under severe rock bursts. Load Changes Under Rapid Load: On some of the earlier rapid-yielding props, conditions of dynamic in¬stability were observed; these conditions resulted in a complete breakdown of support resistance. It is essen¬tial that the force oscillations during rapid yielding be as small as possible, not exceeding -*5% of the average rapid-yield load at a yield rate of 1.0 m/s. Longitudinal Resilience: During rock bursts, vibra¬tions of the roof and floor sometimes are observed. To

Jan 1, 1982

By D. Robert Weir, Roman M. G. S. Berezowsky

Pressure oxidation of gold containing concentrates and ores is an effective pre- treatment for liberating refractory gold. This is particularly true when an appreciable portion of the gold is associated with sulphides and is not amenable to conventional cyanidation. A brief review of the literature on the pressure oxidation of refractory gold materials is presented. The chemistry of the aqueous oxidation of arsenopyrite and pyrite is discussed. Data obtained on the pressure oxidation and subsequent cyanidation of concentrates and ores tested at the Sherritt Research Centre are also presented.

Jan 1, 1984

By C. J. Kirkland

The paper describes the arrangements for the casting, curing and handling at the casting yard, of the concrete segments for the lining of the UK half of the tunnel, and the plant used for the handling of these linings at the construction site. An outline of the tunnel boring machines being used is given, with particular reference to lining handling and erection, and the extensive muck disposal systems installed. A general progress update will be given to the conference.

Jan 1, 1989

By David Wilburn

Recycled materials are increasingly being used in road construction to supplement natural aggregate derived from crushed stone, sand, and gravel. An understanding of the amount of substitution that is taking place, its economics, and factors affecting the level of substitution is useful in estimating the potential for recycling and in assessing the total supply of aggregate. While U.S. consumption of recycled aggregates from crushed concrete is estimated to have increased 160 percent between 1994 and 1996; it comprised less than 5 percent of total aggregates consumed in 1995. Construction waste supply is regional, and is determined by infrastructure decay and replacement rates. Aggregate recycling rates are greater in urban areas where infrastructure is being replaced, natural aggregate resources are limited, disposal costs are high, or strict environmental regulations prevent disposal. Recycling is expected to increase as construction contractors attempt to save on transportation, disposal, and new material costs. Aggregate producers include recycled material as an option to consumers in order to prolong the life of their reserves and improve their range of products. Recycled aggregates can be a supplement for natural aggregates in selected applications, but their use should be evaluated locally based upon relative cost, quality, and market factors Because aggregate recycling is often affected by local and regional transportation systems, disposal and tipping fees, resource supply, the market for specific products, and municipal support, costs for three representative fixed site operations of different sizes were modeled. Under study conditions, all were found to be profitable, but highly dependent upon local tipping fees and market prices, which can differ significantly by location. Smaller operations were found to have different operational dynamics, often requiring creative marketing or incentives to maintain profitability.

Jan 1, 2001

By P. J. Stewart, S. Tracy

This presentation describes the operation and features of the WCC Carbon Reactivation Kiln. Particular emphasis is placed on minimizing carbon losses, corrosion resistance, fuel efficiency and the fate of mercury during reactivation in the multiple-tube vertical retort. Detailed laboratory work indicates that there is complete vaporization of mercury in the kiln, no refluxing in the upper sections and distinct advantages in using this type of kiln when sizing collection equipment.

Jan 1, 1993

By P. R. A. Andrews

Magnesite, brucite and dolomite occur widely throughout Canada, but deposits of economic significance are found only in Quebec, Ontario and British Columbia. Magnesite occurs in all three provinces, brucite in Quebec and Ontario and dolomite in Ontario. Beneficiation of refractory magnesium minerals has been the subject of many investigations at CANMET and the former Mines Branch. Twenty-three magnesite, four brucite and nine dolomite evaluation studies were conducted between 1920 and 1974. A review of some of the more important studies is presented. The information includes mineralogy, beneficiation methods and flotation data.

Jan 1, 1995

By Feng Cai

"As a new method to support gate roadways, rock bolting has been widely used in the big coal enterprises for its superiority. The disturbed stress field of surrounding rock and anchor pre-stress field were divided into 3 areas in consideration of s1, s3. The surrounding rock failure form and characteristic were analyzed in combination with parameter f, the failure mechanism was explained using the slip line theory, furthermore, the rock bolting mechanism and its arrangement were studied. After roadway excavation, the tensile stress area appeared at the surface of the surrounding rock. The failure type changes from shallow tension-shear form into deep compression-shear form and the failure shape is an “incense burner”, surrounding by high risk failure area in butterfly shape. The maximum principle stress in roof appears discontinuous distribution because of layers separation. The failure type of surrounding rock is intensity-stress environment-weak plane control model. The internal reason of roadway macroscopic failure is the displacement between the surface plastic area and the deep elastic region along the tangential direction of slip line. In condition of rock bolt support, there is one-way tensile stress area in small range at the surface of surrounding rock, inside is the bidirectional compressive zone in uniform distribution form, stress environment is improved by the superposition of anchor pre-stress and disturbed stress field, anchor rock bolt arrangement and pre-tightening force distribution is decided according to the distribution of f parameter. Finally, supporting method and parameter reasonability was proved by the roadway deformation monitoring, damage depth drilling peep test in the 8101 transportation roadway in a mine.Introduction The stability of roadway support is very important to the safety and sustainable development of coal mine. In recent years, the focus of China's coal mining industry began to move to West China, the thick-extra thick coal seam is developed in the West. The latest technology and equipment have been put in to service, the occurrence condition of thick coal seam and the increasing of productivity lead to the cross section of the roadway increasing continually, hence, it is more difficult to control the surrounding rock. At present, the most common way to support the roadway is rock bolt (cable) support (Wang 2007); Scholars have been deeply studied on the mechanism of rock bolt. It is reported (Wang et al 2012, Gao 2007, Zhang and Yuan 2006) that the influence of rock bolt on physical and mechanical parameters of coal and rock mass in the anchorage zone, It is believed that the rock bolt can improve the peak strength of surrounding rock, especially the post peak strength, and the failure mode of rock mass under the rock bolt support is analyzed. It is reported (Wang et al 2014, Xiao et al 2013, Li et al 2007, Yan et al 2012), according to different geological conditions, the failure mechanism of surrounding rock and supporting technology of the whole coal roadway were studied. Focus on the failure mechanism of roadway surrounding rock, different forms of high strength support methods were proposed, which achieved good results. It is reported (Wang et al 2012a, Zhang et al 2011, Wang et al 2012b, Kang et al 2010, Zhang et al 2010, Kang et al 2007) that the supporting mechanism of pre-stressed anchor was analyzed from the point of the distribution of the maximum principal stress in the pre-stressed anchor field, and the influence of the rock bolt support parameters and surrounding rock characteristics on the supporting effects were studied. Based on the latest research results, this paper analyzed the failure mechanism of surrounding rock of coal roadway, proposed the high strength anchor net cable combined supporting technology based on the feature of stress zoning distribution of surrounding rock, to provide reference for the coal roadway rock bolt (cable) support technology."

Jan 1, 2017

By C. M. Lundell, F. S. Kendorski, R. D. Prager

The criteria for the design of the shaft/tunnel system excavation at the Rocky Mountain Project was to provide a stable opening during and after construction to receive the concrete lining and to minimize the disturbance of the surrounding rock mass so that the rock mass resists the displacement of the tunnel mining upon internal pressurization. This paper will summarize the geotechnical design of the shaft, elbow, tunnel, bifurcations, and penstocks

Jan 1, 1986

By D. K. Grubbs

Red bauxites from Breadnut Valley, Clarendon Parish, Jamaica, are very homogeneous in texture. Bauxite minerals are uniformly distributed in a groundmass, the predominant grain size being smaller than l um (Figure 1 Although the deposits have a massive, non-stratified structure, they all seem to have been affected by postformational faulting which is evidenced by shear zones running subvertically through the deposits. These shear zones stand out very clearly because of a yellow staining along their faces. Often yellow zones, ranging from a few m to several cm in thickness, have developed. When the shear zones are cut at an angle, they appear as yellow veins. Near the surface of the deposits, yellow material forms shallow irregular lenses (Figure 2). In most cases, tree roots (hair roots), or their imprints, are associated with the shear zones or stained areas. In fact, the yellowish color is especially pronounced along these roots and often disappears where the roots end (Figure 3). The mineral composition and texture of red groundmass and yellow zones are markedly different. Secondary phosphate minerals and a higher goethite to hematite ratio characterize the mineral composition of the yellow zones. It should also be noted that Al-substitution in goethite from these areas is significantly higher than in goethite occurring in the groundmass (Figure 4).

Jan 1, 1980

By N. P. Reddy, L. Adler

The valuable Maximum Utilization Factor (MUF) concept has been extended to other rotating excavators beyond Stripping Shovels and Draglines. In this concept the boom reach and bucket capacity are multiplied to get an MUF, then normalized by dividing by the equipment weight. Statistical analyses were applied to the remaining shovels (hydraulic and cable), draglines, and backhoes. Positive correlations were found. Stripping Shovels and Draglines were also re-examined. The results provide an estimate of equipment diggability and encourages versatility by the interchange of the boom and the bucket. The concept further clarifies the existing equipment classification by delineating General Excavating, Loading, and Stripping kinds. The results also forecast trends, and noted innovative advances and possible retrogression. Extension to other boom excavators, such as front-end loaders, is recommended. The MUF concept provides one of the few indices of gross external characteristics available to the engineer-user of equipment.

Jan 1, 1991

By S. K. Kawatra, T. C. Eisele

In many mining operations, particularly northern open-pit mines, large seasonal variations in grinding slurry temperature can occur. It is shown in this paper that this temperature shift can cause a winter-time loss in autogenous grinding efficiency of as much as 20% if it is not controlled. Laboratory experimentation indicates that much of this effect is due to increases in slurry viscosity as the temperature is decreased. An additional effect may result from changes in rock strength upon freezing, for which possible mechanisms are discussed. However, no effect clearly resulting from rock strength changes has been definitely confirmed.

Jan 1, 1992

By J. B. Hiskey, V. P. Atluri

Resin-in-leach (RIL) cyanidation experiments were performed on a refractory carbonaceous gold ore. The objective of this investigation was to determine if strong-base ion exchange resins could adsorb the soluble aurocyanide complex in preference to natural "preg robbing" organic constituents. Direct cyanidation of the carbonaceous gold ore used in this study resulted in less than 2% gold extraction in 24 hr. RIL cyanidation resulted in about 70% gold recovery onto the resin. Kinetic experiments indicated that 50% of the gold is extracted after 1 hr of leaching. Resin breakage was investigated for as-received and preattrited resins. Similar results were obtained with three different strong base resins.

Jan 1, 1990

By Paula N. Wilson, W. T. Parry

Carbonaceous and metalliferous black shales occur in close proximity to Mercur-type gold deposits in the southern Oquirrh Mountains, Utah. These shale units, the Manning Canyon shale and the Long Trail shale, have undergone regional hydrothermal alteration. Hydrothermal solutions oxidized organic matter and pyrite, replaced shale by hydrothermal phyllosilicates and silica, and replaced fossils by phyllosilicates. The shales are depleted in organic carbon, calcium carbonate, alkali and alkaline earth metals, and enriched in aluminum and hydrogen. Hydrothermal veins containing illite, chlorite, pyrophyllite, kaolinite, Fe-oxides, and sulfides are present throughout the study area.The illite in veins is an ammonium illite that contains up to 2 % NH4 and is correspondingly depleted in K. Correlations among Au, As, Hg, TI, Sc, and rare earth elements indicate that hydrothermal fluids responsible for formation of ammonium illite were gold bearing. K/Ar ages of illite veins and illite-rich, clay-size separates of altered shales indicate hydrothermal activity occurred in the time range 193 to 122 Ma. Several ages from clay-size separates within the Mercur district cluster near 160 Ma. These ages are coeval with thrust faulting recognized to the north and west.

Jan 1, 1990

By A. Gupta, S. C. Srivastava, K. K. Saroj

Bacterial degasification of methane and conventional methane drainage for generation of power have become accepted practice. Comparative economies of both the techniques have been described. Authors have discussed an alternative technique, involving complete methane biocycle. The first stage of the entire process involves gasification of coal using a consortia of bacteria to generate methane. The generated methane has been proposed to be pumped,as in conventional methane drainage. Technique described is basically similar to underground coal gasification, with the difference that in place of coal combustion, degradation of coal to lower molecular weight compounds by one set of bacteria and then methanogenesis by methanogens, producing methane have been described. Brief account of communities of bacteria that may be employed have been dealt with. Three arguments in favour of proposed technology as an alternative to conventional coal mining are: 1.Total elimination of hazardous operation. 2.Availability of power plants based on methane drainage, assuring comparative economies. 3.Possibility of utilisation of fuel cell technology for power generation giving higher efficiency. All the three phases of complete blocycle viz (1) methane generation from coal (ii) conversion of methane to hydrogen and oxygen (iii) conversion of products so obtained to methane, thereby completing the cycle have been discussed. INTRODUCTION Drainage of methane by conventional pumping process (Boxho,et.al.,1980) not only is helpful in maintaining safe extraction of coal, but with utilisation of extracted gas for power generation, also helps in over all economy of coal mining. This is gradually becoming standard practice for mining of coal in highly gassy mines. An alternative technique (Thakur et. al., 1991) of bacterial degasification of coal seams is also gradually gaining ground. The bye products of this process that is carbondioxide and water, do not contribute towards economy of coal extraction process. However the technique has its own advantage particularly in goaf area for avoiding fire hazard and drainage of methane from coal seams prior to initiation of mining operation. Either of these techniques could be applied in specific situations with success.

Jan 1, 1993

By Carol Cox Russell

More than two thousand abandoned mines within the Animas watershed in Southwestern Colorado are being prioritized for remediation by the Animas River Stakeholders Group (ARSG). Phased collection and assessment of information progressed from large scale to site specific. Prioritization was based on existing or potential environmental impact and technical feasibility of remediation as measured by dissolved Cd, Cu, and/or Zn in the discharge; indicators of habitat degradation; aquatic life in streams; cumulative impacts at the point of compliance; cost effectiveness; treatiblity/feasibility; and cultural and historic preservation.

Jan 1, 2000

By A. Iordanidis

Ieropigi Fe-Ni deposit is located in northern Greece, in Kastoria?s prefecture near Albania?s borders. A laterite profile exposed by opencast mining and placed near the basement of the mine was chosen for sampling. Ten samples, representing ?pure? Fe-Ni ore, ophiolite-bedrock, ?red? ophiolite and ?enriched? ophiolite were collected, based on macroscopic observation. The samples were analysed by X-Ray powder Diffraction (XRD) for the determination of the mineral phases. Iron and Nickel concentrations of the same samples were also determined by X-Ray Fluorescence (XRF) methodology. The Fe-Ni ore samples consists predomi-nantly of hematite, goethite, chrysotile (serpentine), saponite and quartz. ?Red? ophiolite samples consists mainly of chrysotile, hematite, quartz, calcite and small amounts of paragonite and goethite. Bedrock and ?enriched ophiolite samples are comprised of chrysotile, hematite, calcite, quartz, nontronite, paragonite and sepiolite. The Fe content ranges between 13% and 49% in Fe-Ni ore samples and between 7% and 10% in ophiolite samples. The Ni content ranges between 1% and 3% in Fe-Ni ore samples and between 0.3% and 4.5% in ophiolite samples (the higher content is observed in the so-called ?enriched? ophiolite). A correlation between Fe-Ni concentrations and mineral assemblages is being attempted in order to evaluate the nickel-rich mineral phases. It is shown that the nickeliferous minerals are serpentine, hematite, goethite and saponite.

Jan 1, 2006