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By Hamid Maleki

The U.S. Bureau of Mines implemented a monitoring program in a western U.S. coal mine for the evaluation of both conventional and alternative support systems. The conventional support consisted of 2.5-m-long vertical bolts installed in an 5.5-m-wide entry. The alternative system consisted of 2.5- and 3-m vertical and inclined bolts installed at a higher density during widening of a cut from 3.6 to 5.5 m. Roof deformation, roof stress, rib deformation, and bolt loads were monitored during the 2-month test period. In addition, roof failure patterns and lithology were characterized within the six-entry main test section. Results were analyzed using roof deformation and failure profiles, roof stress profiles. bolt loading and bending moment diagrams, and numerical models. The mechanics of roof deformation, failure, and support reaction in three zones in the mine roof were characterized. Significant improvements were shown in roof stability in the section using the alternative system. Results are encouraging and indicate the effectiveness of alternative support systems and excavation techniques for limiting inelastic deformation of roof in highly stressed underground mines.

Jan 1, 1994

By P. Chu, J. A. Finch

The formation of small bubbles in flotation is usually accomplished by the use of frothers, or sometimes is due to the presence of inorganic salts in the process water. The effective mechanism associated with the presence of these solutes is generally considered to be coalescence inhibition. However, recent work has demonstrated that the presence of frothers and salts also reduces the size of bubble at the initial formation stage. In this paper we adapt the same experimental setup to investigate the time that it takes for a bubble to form; for a known system power input, the energy to form a bubble can then be estimated from the time. The hypothesis is that the presence of frother and salt will reduce the time for a bubble to form, which can be interpreted as an added energy component being derived from the solute. Testing different types and concentrations of frothers and salts, the hypothesis is supported: the mechanical energy required to form a bubble decreases by about 10% in the presence of these solutes.

Jan 1, 2015

More than 1,200 professionals from the global tunneling and underground space industries are expected to be on hand for the 2009 Rapid Excavation and Tunneling Conference to be held at Caesars Palace in Las Vegas, NV. The conference, set for June 14-17, is sponsored by the Society for Mining, Metallurgy, & Exploration, Inc. (SME) and the Construction Institute of the American Society of Civil Engineers. The four-day conference will feature more than 100 technical papers in 19 sessions. Two one-day short courses are also planned, as are a pair of field trips. And the show?s exhibit will feature more than 120 of the industry?s leading equipment and service suppliers.

Jan 1, 2009

By Matthias Merzkirch, Volker Schulze, Kay Andre Weidenmann

"Unidirectionally reinforced light weight compounds based on light metals such as the aluminium alloy EN A W-6082 are adequate materials for the future use in transportation means like automobiles and airplanes. Due to the occurring cyclic loads knowledge about the crack growth behaviour of such composites is needed. The investigations at a load ratio of R = 0.18 show that the crack growth rate of the aluminium matrix is reduced if reinforced by spring steel wire with a reinforcing ratio of only about 1 Vol.-%. Additionally, the acoustic emission analysis allows detecting crack growth within the matrix material, crack propagation along the interface wire/matrix and crack closure which could also be determined with the help of a self designed capacitive displacement measuring gauge. The damage behaviour could be verified by metallographic and SEM investigations.IntroductionIn the field of lightweight structures for transportation means the need for light, strong and stiff materials, in particular composite materials, is increasing in order to save resources and costs. Lightweight materials such as aluminium and magnesium alloys are highly efficient candidates to be used in the composite extrusion process [1] which allows for a simple production of unidirectionally reinforced profiles with a large diversity of geometries at low costs. Figure 1 depicts the principle of the composite extrusion process; within the first part of the tool the billet material is split into several strands whereas the middle part of the tool allows the supply of the reinforcing elements. The third part of the tool rejoins the matrix material and the reinforcing elements and defines the final shape of the profile."

Jan 1, 2011

By A. Ordoñez

El presente estudio refiere la metodología y los cálculos para resolver el problema del transporte del fluído en el sistema de bombeo, de forma que ayude al diseñador en la selección de números de plantas de bombeo, sistema de la tubería y los diámetros adecuados, así también se describe las características idóneas para las posibilidades de su operación. Las características técnicas y económicas son programadas en FORTRAN IV y se obtienen para cada alternativa los costos de inversión anual dol proyecto con los que se determina la solución óptima. Una vez obtenida la solución óptima para el sistema de bombeo, el diseñador evaluará un programa donde se determine los anclajes y la ubicación de válvulas de aire, considerando ciertas simplificaciones en la estructura que mejoren el análisis del sistema.

Nov 20, 1972

By G. W. Jones

[As a part of its investigations pertaining to the promotion of safety, the Bureau of Mines is investigating various means, useful for the elimination or mitigation of the explosion hazards of combustible gases encountered in mining and industry. Information has been obtained and a procedure developed whereby the explosibility of many complex, gaseous, combustible atmosphere may be calculated in a simple manner without the necessity of performing laborious laboratory experiment. In a previous publication4/ data were given and a method described whereby the limits of inflammability of gaseous mixtures, including methane, hydrogen, carbon monoxide, nitrogen, carbon dioxide, and oxygen, could be determined by calculation. The information published in that retort enables one to calculate the limits of inflammability of such gases are liberated by mine fires, gases from explosives, automobile exhaust gas, gases present after mine explosions, blast-furnace gas, and other gases containing part of or all of the above-listed constituents.]

Jan 1, 1938

By G. W. Jones

As a part of it investigations pertaining to the promotion of safety, the Bureau of Mines is investigating various means, useful for the elimination or mitigation of the explosion hazards of combustible gases encountered in mining and industry. Information has been obtained and a procedure developed whereby the explocibility of many complex, gaseous, combustible atmospheres may be calculated in a simple manner without the necessity of performing laborious laboratory experiments. In a previous publication4/ data were given and a method described whereby the limits of inflammability of gaseous mixtures, including methane, hydrogen, carbon monoxide, nitrogen, carbon dioxide, and oxygen, could be determined by calculation. The information published in that report enables one to calculate the limits of inflammability of such gases as are liberated by mine fires, gases from explosives, automobile exhaust ran, uses present after mine explosions, blast-furnace gas, and other gases containing part of or all of the above-listed constituents.

Jan 1, 1938

By Juhyung Lee

Numerical analyses were performed to analyze the behavior of two different type of suction piles (mono type and group type) under various soil layer conditions (uniform silty clay layer, uniform silty sand layer, and two-layer deposit consisting of clay and sand layers) and lateral loading locations (top, middle, and bottom of the suction pile). According to the results, mono suction pile shows maximum resistance when load is applied on its middle, regardless of the soil layer conditions, while group suction piles varies significantly according to the allowance on head rotation. When head rotation is allowed, the behavior of group type piles become similar to the behavior of mono suction pile. Whereas, when rotation is prevented, resistance is maximized when load is applied on the top head. Moreover, group suction piles show higher efficiency regardless of the ground condition and geological stratum. For further advances, concrete block on the top of group suction piles are suggested as an effective alternative method to prevent partial rotation and maximize ground resistance for group suction piles.

By Claudio Lechuga, Carlos Scherpenisse, Juan Rafael Otaiza

From the analysis of drilling process, Block Model information, drilling pattern data and expected fragmentation targets; GBlast® software optimizes the explosive charge design in order to standardize the particle size of each blast.

Feb 1, 2020

By E. Siami-Irdemoosa, S. R. Dindarloo

"Pareto analysis was used to investigate the failures database of a Hitachi EX1900 hydraulic shovel over one year of continuous operation. The hydraulic system and hydraulic links, hoses and piping were identified as the most critical system and subsystem, respectively. A three-parameter gamma distribution function was identified as the best fit for a probabilistic modeling of the time between failures (TBFs). This distribution was used in a Monte Carlo reliability analysis of the hydraulic system. Autoregressive integrated moving average (ARIMA), within the context of a time series analysis of the TBFs, was proposed as a viable alternative to the traditional technique of distribution fitting. The mean absolute percentage error (MAPE) metric was used to compare the two models. The MAPE value that resulted from the ARIMA was 66 percent smaller than that from the traditional technique in predicting the TBFs.Resumen ¦ Se usó análisis Pareto para investigar la base de datos de fallas de una pala hidráulica Hitachi EX1900 durante un periodo de un año de operación continua. Se identificó al sistema hidráulico y a los enlaces hidráulicos, mangueras y tuberías como el sistema y subsistema más importantes, respectivamente. Se identificó una función de distribución de tres parámetros gamma como el más apto para un modelado de probabilidades del tiempo transcurrido entre las fallas (Tabes por sus siglas en inglés). Esta distribución fue usada en un análisis de confiabilidad Monte Carlo para un sistema hidráulico. El promedio de movimiento integrado auto-regresivo (ARIMA por sus siglas en inglés), dentro del contexto de análisis de serie temporal de los TBFs, fue propuesto como una alternativa viable a la tradicional técnica de ajuste de distribución. Se usó el porcentaje de la media absoluta de error (MAPE) para comparar los dos modelos. El valor MAPE que resultó de la ARIMA fue 66 por ciento menor que el resultado obtenido con la técnica tradicional de predicción de TBFs."

Jan 1, 2015

By R. H. Reist, R. D. Dey, V. Castranova, J. P. Durham, Y. Rojanasakul

"Silicosis is a fibrotic pulmonary disease produced by inhalation of silica-containing dusts (Peters, 1986). Chronic silicosis may develop 20-40 years after initial exposure to crystalline silica, and the disease may progress from a simple to a complicated form. Few symptoms are evident in simple silicosis with pulmonary function being relatively normal. However, chest radiographs reveal small rounded ·opacities in the upper lobes of the lungs. These silicotic nodules consist of collagen arranged in a distinctive circular pattern. As fibrotic changes become more severe, the disease progresses to complicated silicosis (progressive massive fibrosis). Complicated silicosis is associated with shortness of breath and decreases in pulmonary function characteristic ofrestrictive lung disease. Chest x rays reveal numerous large silicotic nodules which may be associated with scar emphysema. Several mechanisms have been proposed to explain the cellular events which result in silica-induced lung damage and fibrosis (Lapp and Castranova, 1993). They include: ( l) direct cytotoxicity of silica, (2) activation of oxidant and enzyme release from alveolar macrophages, (3) recruitment and activation of polymorphonuclear leukocytes, and (4) stimulation of fibroblast proliferation and collagen synthesis.Tetrandrine is a bisbenzylisoquinoline alkaloid derived from the Chinese herb Radix Stephania tetrandra. It has a molecular weight of 622.73 and an empirical formula of C38H420 6N2. The chemical structure of tetrandrine has been published previously by our laboratory (Castranova et al., 1991 a). Its structure is characterized by methoxy groups at C7 and C12 , uncharged nitrogens at N2 and N’2 and two 17-carbon ring members connected by a double oxygen bridge between Ca-C7 and C11-C12. Tetrandrine has been shown to reduce both silica-induced fibrosis and the elevation of lung collagen content in rats (Huang et al .. 1981; Yu et al., 1983; ldel, 1987). Furthermore, tetrandrine has been used as an antifibrotic agent in Chinese clinical trials (Li et al.. 1981 ). Preliminary results suggest that administration of tetrandrine to patients with silicosis results in substantial improvement of symptoms, increases in diffusion capacity, and decreases in the size of shadows on lung x rays."

Nov 1, 1995

By L. D. Wyant

That natural gas-gasoline can be used to advantage as a refrigerant is suggested by the fact that the "make" tanks and other parts of the equipment of gasoline plants frequently become coated with frost. The experiments reported in this paper confirm this assumption and indicate that volatile gasoline can be use used to advantage in many refrigerating plants. The Bureau of Mines is making a study of wax distillates in order to find out why satisfactory lubricating oils and waxes can be made easily from certain crude oils and only with difficulty from others. In the commercial distillation of crude petroleum it is customary to separate the distillates into the following groups: (A) Gasolines and naphthas, (B) Kerosenes, (C) Gas oil, and (D) Wax distillate (consisting mostly of light lubricating oil together with small amounts of paraffin Wax).

Jan 1, 1923

By Terence M. Gordon, Mati Raudsepp, Gregory M. Dipple

Four methods of measuring mineral abundance in a rock are examined for their potential in assaying for high-tech industrial minerals. One method uses X-ray powder-diffraction data and the other three rely on whole rock chemical data and information on mineral assemblages and mineral compositions. All four methods were employed to estimate wollastonite content in diamond drill core of skarn collected as part of an exploration program and are compared to visual estimates of wollastonite content from core logs. These techniques for assaying wollastonite span a considerable range ofaccuracy and expense, and combined, define a non-linear relationship between these variables. Accuracy increases rapidly relative lo expense up to total costs of about $50 per analysis. Assay methods in the $50-100 per analysis range have associated errors of 5-10% relative and probably suffice for most exploration programs. Improvements in accuracy above this level require a much larger investment. The most expensive assay technique (-$300 per analysis) yields the most accurate measurement of grade (relative error -1%). Its application may best be limited to periodic checks on other assay techniques and for fine-tuning ofmineral separation procedures.

Jan 1, 2001

By Andrei Bagrianski, Marco Nieto, Alexander Prikhodko

Se realizó una adquisición magnetotelúrica helicotransportada con el sistema MobileMT sobre un depósito metálico asociado a un pórfido de cobre conocido como Proyecto Santiago en el Cinturón Metalogénico Mioceno al sur de Ecuador. La adquisición geofísica se enfocó en identificar las respuestas de magnetometría y conductividad eléctrica y paso seguido, realizar inversiones unidimensionales y bidimensionales con el objetivo de caracterizar la respuesta petrofísica del sistema tipo pórfido. Los resultados arrojaron una anomalía de conductividad aparente mayor a 15 mS/m que se identificó como el cuerpo porfirítico en profundidad, llegando a estar entre 200 m a 600 m por debajo de la superficie.

May 10, 2023

By Sergio T. Amancio-Filho

FricRiveting technique is an alternative new spot joining process developed for thermoplastic-lightweight alloy structures. In this technique a cylindrical metallic rivet is used to join one or more thermoplastic / metal components by means of plasticizing and deforming the tip of the rotating rivet through frictional heating. Advantages of this new technique are e.g. short joining cycles, minimal sample preparation, absence of environmental emissions and enhanced mechanical performance in comparison to base materials. Qualitative and quantitative synchrotron X-Ray microtomographic and light optical microscopic analysis of a case-study joint on aircraft materials polyetherimide and aluminum 2024 showed that joint strength is mainly dependent on aspect ratio of the rivet (geometrical dependence) and quality of joint, (microstructural dependence), whereby increasing aspect ratios and lowering the percentage of defects usually yield improved strength.

Jan 1, 2009

By J. Best, K. Gallant

This paper explores the age-old concept of mine-mill reconciliation from a new perspective. Advances in reconciliation processes have been slow to materialize because in the quest for “rightness”, engineers, geologists and metallurgists have become entrenched in their viewpoints, dutifully performing to the metrics and expectations imposed upon them by the siloed organization. Moreover, reconciliation has not been viewed as a primary value creator, but an accounting non-value added task. In reality, the knowledge from reconciliation can significantly enhance yields. Critical review of the direct variables (tons, grade, etc.) and other less-obvious variables (incentives, communication, etc.) reveal a complex web of barriers to be cleared by management in order to realize benefits. Also, mineralogical reconciliation methods may offer renewed faith in the process.

Jan 1, 2004

By Guilherme Liziero Ruggio da Silva, Iara Patricia Vieira de Oliveira, João Ricardo Denicolo Braga, Paulo Santos Assis, Lorena Cristina Amorim Moura

Nos últimos anos diversos trabalhos evidenciam a possibilidade de utilização de small coque como constituinte da carga metálica dos altos-fornos, visando a redução na temperatura da zona de reserva térmica. Esse trabalho avalia a viabilidade técnica, em escala laboratorial, da produção de um determinado small coque altamente reativo, através da adição de 2 catalisadores: pellet feed e cal virgem totalizando 3% em massa, em sua superfície. Foram realizadas caracterizações químicas dos catalisadores por meio de Fluorescência de Raios-X (FRX) e avaliados os impactos destas adições sobre CRI (Coke Reactivity Index) e CSR (Coke Strength after Reaction) das amostras produzidas. Os resultados mostraram aumentos acima de 2% na reatividade do small coque, tanto para a adição de cal virgem quanto para pellet feed, porém mais significativo para a adição de cal virgem, comprovando que a técnica de Pós-adição de catalisadores da reação de Boudouard no small coque, pode ser uma alternativa para redução de custo e emissões de CO2 no Alto-Forno.

Oct 1, 2019

By F. D. Rosi

The plastic properties of extended silver and copper crystals of varying purity were studied as a function of crystal orientation in the early stages of flow. Variations in the gross shape of the shear stress-shear diagram and in the properties of critical Variationsshear stress and shear-hardening coefficient were correlated with changes in slip-band developments. The phenomenon of work hardening is discussed in terms of the existing dislocation theory. IT appears certain from the early studies on the deformation characteristics in metal crystals1-3 that plastic flow takes place in a preferred crystallo-graphic slip system which is determined by the geometry of the crystal (law of maximum shear stress), and that the value of shear stress for this system is independent of crystal orientation (law of critical shear stress). Experimentally, it has been demonstrated further that the law of critical shear stress can be extended to include extensive plastic flow.&apos; Thus, the shear-hardening coefficient, which is defined as the slope of the shear stress-shear curve, also is considered to be independent of orientation. It is noteworthy that deviations from this empirical shear-hardening law have been reported in cubic crystals whose initial orientation favors slip on more than two systems.&apos; Moreover, this law appears to have been derived from stress-strain data relating to relatively high values of shear strain (0.5 to 4), where widespread slip and complex distortions can be expected, regardless of crystal orientation. Since existing data indicate that the strain inhomogeneity in a crystal is manifested particularly in the early stages of flow, it would appear that a more exacting test as to the fundamental nature of the shear-hardening law would be to investigate systematically the shape of the stress-strain curve as a function of crystal orientation in the earlier stages of deformation. With regard to the general form of the shear stress-shear curve for cubic crystals, early studies show a parabolic hardening law, where the shear 1 stress is proportional to the square root of the shear-strain. Since this law was predicted theoretically by Taylor" in his original dislocation model for hard- ening, it has been accepted widely as a fundamental flow characteristic of cubic metals. However, it was recently pointed out by Masing6 hat the parabolic law is not the elementary form of hardening in cubic crystals, but instead is a consequence of complexities in the flow process (e. g., deformation bands and unpredicted secondary slip). Thus, in the very early stages of deformation (< 2 pct extension) where the occurrence of such complexities is unlikely, a different strain-hardening behavior might be anticipated. This view is supported by the recent work of Rosi and Mathewson7 on high purity aluminum where a linear law was obtained for extensions up to 2 pct. A linear hardening over a wider range of deformation also was reported by Rohm and Kochendorfer8 ho deformed aluminum crystals under conditions approximating pure shear. Even more pertinent is the recent evidence of Masing and Raffelsieper9 on high purity aluminum crystals. It was found that for crystals having initial orientations near a <l00> or <1ll> axis, a high hardening was obtained, whereas crystals with a <110> orientation exhibited a low and linear hardening curve followed by a region of more rapid hardening. Since much still remains obscure concerning the details of strain hardening as well as slip-band formation in face-centered-cubic crystals in the early stages of deformation, the present study was undertaken to evaluate the effect of crystal orientation on these two important manifestations of glide. It is important to note here that at the time of this study, Lucke and Lange11 presented information on the orientation-dependence of the shape of the strain-hardening curve in aluminum of various purities. Their work, which essentially represents an extension of that of Masing and Raffelsieper, in many respects is parallel to that of the present study. Experimental Procedure Production of Single Crystals: Single crystals of silver and copper of varying purity were used in

Jan 1, 1955

By B. X. Huang

Hydraulic fracturing technology is presented as a solution to improve permeability and thus solve the extraction problem of coal seam gas in low-permeability gas-bearing coal seams. Given an existing group of original cracks, the propagation of main hydraulic cracks and hydraulic wing cracks was simulated using realistic failure process analysis software. The process represents the structural transformation of hydraulic fracturing and permeability improvements caused by it. In addition, a field test for improving the permeability of gassy coal seams by hydraulic fracturing was also conducted. The propagation of the main cracks and wing cracks by hydraulic fracturing forms a network of original joint cracks, hydraulic wing cracks, and main hydraulic cracks, which improve the permeability of the coal seam. High-pressure water in the drill hole and in the main hydraulic cracks permeates the two flanks of the hole, forming the permeating water pressure. With an increase in drill water pressure and an extension of the main hydraulic cracks, the permeating water pressure on both sides of the main hydraulic cracks in the coal mass also increases. Hydraulic cracks tend to form connections through rock bridges. The extension of hydraulic wing cracks through connections in the rock bridges between the cracks transforms the rock mass to a fractured structure and improves its permeability. Hydraulic fracturing technology for improving permeability in underground conditions can increase the amount of gas drainage by a factor of 15. A stress relief area develops at a radial distance of 10-2.0 m from the hydraulic fracturing drill hole, while an area of rising stresses, called the pressurized area, develops a further 15 m away from the pressurized hole. Practice has proved the existence of the stress transfer phenomenon and the high stress area after fracturing. This kind of hydraulic fracturing technology is more effective in holes drilled from underground than in surface drill holes, with respect to costs and controllability, and is therefore the major trend in gas drainage development in coal mines.

Jan 1, 2012

By Rosa Malena Fernandes Lima, Rodrigo Fina Ferreira

Since 2011 mineral cargo shippers shall comply with the Maritime Solid Bulk Cargoes (IMSBC) Code regulatory framework, established by the International Maritime Organization. Some mineral cargos may liquefy during passage, under certain conditions, if the moisture content is beyond a certain level, and the cargo shifting may jeopardize the stability of the vessel. For cargos which are susceptible to this phenomenon the IMSBC Code stablishes that the moisture content shall be below the Transportable Moisture Limit (TML) for safe transportation by sea. Iron ore fines TML can be determined through the Modified Proctor/Fagerberg Test for Iron Ore Fines. Knowledge related to the TML has become essential to shippers, and research works related to this parameter are increasingly frequent. However, the typical daily productivity for having a TML result through this method is one up to two samples per executant person, requiring approximately 50 kg per sample. This study presents a practical example of the application of a prediction model for estimating the TML. The model application reduced substantially the laboratory work and sample quantity requirement for obtaining conclusions related to the TML.

Oct 3, 2019