Search Documents

By A. Thoraval, K. B. Slimane, O. Ozanam

The REP experiment is part of the research programme conducted by Andra to investigate the possibility of reversible radwaste disposal in a Jurassic (Callovo-Oxfordian) argillite formation at the Meuse/Haute-Marne underground laboratory site in northeastern France. The experiment focuses on the hydromechanical response of the formation to sinking the laboratory access shaft. Modelling of boreholes and shaft sinking operations has helped to optimise measurement point locations based on initial stress tensor anisotropy, while minimising interaction between instrument boreholes. Analyses were made of model sensitivity to intrinsic rock characteristics, hydromechanical coupling properties and sensor installation procedures. L’expérimentation REP fait partie du programme de recherche pluridisciplinaire engagé par l’Andra pour étudier la possibilité d’un stockage réversible des déchets radioactifs dans la formation Callovo-Oxfordienne des argilites du site de Meuse/Haute-Marne (Commune de Bure - France). Cette expérimentation permettra d’étudier la REponse hydromécanique de la formation aux sollicitations engendrées par le fonçage du Puits d’accès du laboratoire souterrain de recherche. Afin d’optimiser le positionnement des points de mesures, compte tenu de l’anisotropie du tenseur des contraintes initiales, et de minimiser les interactions entre les forages d’instrumentation, des modélisations des forages et du creusement du puits ont été conduites. Des analyses de sensibilité aux caractéristiques intrinsèques de la roche, aux propriétés de couplage HM et aux protocoles d’installation des capteurs ont été faites. Die REP-Untersuchung ist Teil des multidisziplinären Forschungsprogramms, das die ANDRA im Callovo-Oxfordian-Tonstein in situ am Standort Meuse/Haute Marne (Gemeinde Bure – Frankreich) im Hinblick auf eine Eignung zur reversiblen Lagerung radioaktiver Abfälle durchführt. Dabei soll das hydro-mechanische Verhalten der Formation auf die Beanspruchungen, die durch das Abteufen des Zugangsschachts zum Untertage-Forschungslabor erzeugt werden, untersucht werden. Zur optimalen Positionierung der Messpunkte unter Berücksichtigung der Anisotropie des Tensors der Ausgangsspannungen und zur Minimierung der gegenseitigen Beeinflussung der Instrumentierbohrungen wurden ein Schachtabteuf- und Bohrmodelle entwickelt. Zur Untersuchung der inhärenten Eigenschaften des Gesteins, des gekoppelten HM-Verhaltens und der Installationsprotokolle der Messsonden wurden Sensibilitätsanalysen durchgeführt.

Jan 1, 2003

By Donald W. Scott

GENERALLY speaking, there is nothing very difficult about taking good micrographs of photogenic thin sections or grains with a petrographic micro-scopecamera setup. However, sometimes it is desired to show some detail that cannot be illustrated satisfactorily by the usual micrographs taken with parallel polarized light, with crossed nicols, or even with two micrographs. A simple procedure giving good results has been used at Battelle Memorial Institute for subjects falling into this classification, and it is believed to be of interest, especially to research people who must sell a point to executives through the medium of well-illustrated reports. The following problem illustrates a typical application: It is desired to photograph a thin section of an iron ore to illustrate the character and association of the iron oxides and the individual quartz crystals. A magnification of 75 dia. is acceptable. A micrograph of the field in question (Fig. I[a]) was taken with parallel polarized light. Due precaution was taken to provide critical illumination, correct exposure, a sharp focus, a good darkroom technique, and other essential conditions. It illustrates correctly the iron oxides, but it fails to show the individual quartz crystals. A micrograph of the identical field (Fig. I[b]) was taken under the same precise conditions, but with crossed nicols. It gives a better idea of the character of the individual quartz crystals but is likely to be misinterpreted unless accompanied by a lengthy descriptive note. This micrograph suggests that the centrally located, large black area is composed entirely of iron oxides. That this is an incorrect interpretation is evident by reexamining the micrograph of Fig. I[a]. The correct interpretation is that the dark area contains quartz crystals oriented with their optical directions parallel to, or nearly parallel to, the vibration directions of the polarizer and analyzer of the microscope. Thus, the executive, or anyone who had not done the work personally, would get no more than a fair interpretation, even if two micrographs were included; and in the interests of both brevity and clarity, one micrograph usually is more desirable. Exactly how many quartz crystals occur in this region cannot be told from the two micrographs, and a printing of the two negatives in register would likewise not show the detail desired. Thus, it is evident that some subjects cannot be satisfactorily illustrated by the usual procedures. In photographing Fig. is the light was subdued and, during the entire exposure of 75 sec., the analyzer nicol was rotated uniformly in its mounting from a crossed position to 45° uncrossed position to introduce the desired amount of contrast in the various individual quartz crystals. The true reproduction of the character and association of the iron oxides, and the additional structure and detail in the quartz areas, is apparent. It might be

Jan 1, 1946

By Enrique Albarrán, Julian Hernández

"In 1942 The “Presa Mixcoac” dam was built, along with 15 other dams, to control the rain fall waterin the mountains west of Mexico City. Mexico City’s population at that time was around 1.5 millionpeople, and the dam was way out of the city."

Jan 1, 2016

These may be of interest to members examining the collection of ores, etc., from Mount Lyell, which is a feature of the Victorian Gold Jubilee Exhibition, and may have some value as geological records. No. 7 and No 8 are analyses of samples of footwall rock from the Lyell Tharsis mine. No. 7 is hard, crystalline, fine-grained, and of homogenous structure. It has a dark-red colour, due to ferric oxide (Fig 1); and was taken from a place eight feet east of the ore body and about half way between the 50 feet and 100 feet levels. No. 8 is from the same excavation and from four feet east of the ore body it is softer than No. 7, being easily scratched with a knife-blade, of a deeper dark-red colour, and has a slaty cleavage.

Jan 1, 1902

By Mikhail P. Nesterov

The paper presents the results of the research that can forecast the development of subsidences and deformations of the earth surface with time in the permanent marginal areas of the movement troughs arising when mining sylvinite beds in the Upper Kama deposit of potash ores where the rock formation support is made by means of interchamber (rib) pillars of various yieldability.

Jan 1, 1997

By Kiko Delgado

Actualmente el problema de los conflictos sociales ha sido abordado por enfoques cualitativos tales como análisis de discurso, mesas de dialogo, entre otros, desde especialidades que provienen de las ciencias sociales, lo cual es entendible por la naturaleza de este problema. Sin embargo, al ser un problema complejo requiere un abordaje multidisciplinario y desde las ciencias y la ingeniería se pueden hacer contribuciones usando enfoques cuantitativos que ayuden a la mejor toma de decisiones para la resolución de la conflictividad social. Por lo tanto, el objetivo de este trabajo es describir, aplicar y validar el modelo de IA, basado en sistemas grises y la entropía de Shannon, en dos proyectos mineros emblemáticos en Perú.

Sep 29, 2023

Jan 1, 1994

By E. R. Dean

A wire-feed mechanism has been employed to fabricute metal alloy film resistors to various sheet resistivities on oxidized silicon substrates. The effect of several thousand hours storage in air at elevated temperatures on the resistance and temperature coefficient of resistance is presented. Unprotected films of- sheet resistivity between 100 and 500 ohms per sq fabricated at 300°C substrate tenzperatures were unstable when stored at 150°Cfor extended periods. The higher sheet resistivity films exhibited the greatest instability; however, even the 100 ohms per sq films drijted excessively for device application. When stored at still higher temperatures, the normalized resistance increases to maximum, then decreases until a minimum value is obtained, then finally increases in resistance until open. The use of a protective overcoating of SiO has had considerable benejicial effects on the film stability, so that 250 ohms per sq films deposited on 300°C substrates are now stable after 1000 hr storage at 250°C and possess a temperature coefficient of resistance less than 200 ppm per C. The use of a low substrate temperature during depositon (100°C) enables the preparation oj resistors with very low tenperature coefficients of resistance (10 to 20 ppnl per 'C). However, these films are less stable than their higher substrate temperatuve counterparts. During extended storage, the resistance of the protected films always decreases with lower substrate films exhibiting larger normalized resistance decreases. This resistance decrease is accompanied by a linearly related increase in the temperature coefficient of resistance. The electrical behavior of these films may be explained by postulating That the structure of the films is in the transition region between thick continuous films and ultrathin island structure films so that the conductivity is the restlt of both electron scattering and tunneling-activated charge carrier creation between neighboring grains. The annealing behavior when thermally aged is the result of defect anneal, grain growth, and selective oxidation. TheRE is a considerable interest in thin metallic films for use as resistor elements in microelectronic circuits.1,2 These resistor films must be stable when exposed to elevated-temperature storage or operating ambient, possess low temperature coefficients of resistance (hereafter referred to as T.C.R.), and be of a high enough sheet resistivity to be useful. The resistivity and T.C.R. of a thin metallic film are determined by the structure and thickness of the film. Hence the stability of the film when exposed to stress would depend on the stability of the structure. The resistivity of a thin film is the result of the electrons' interaction with the lattice vibrations (electron-phonon scattering), scattering of electrons due to impurities, defects, and grain boundaries and specula reflection from the film surfaces.3' All of these effects serve to reduce the electron mean free path and result in a resistivity higher than the ideal bulk. In ultrathin films possessing essentially an island structure consisting of a planar array of aggregates separated by a few to a few tens of angstroms, conduction is dominated by a combination of tunneling and activated charge carrier reation. Thin films would be characterized by relatively low resistivity, positive T.C.R., and reasonable structure stability whereas ultrathin films possess unstable structures, negative T.C.R., and exhibit high resistivity. Feldman6 has investigated films intermediate between the two regions and postulates that the resistivity of a film in the transition region is composed of two linearly additive parts: that due to the resistance of the grains and that due to the gaps. The grain resistivity would represent the scattering of the conduction electrons by defects, surfaces, and phonon interaction while the gap term represents the tunneling contribution. For gold and platinum films, he found as the film structure becomes progressively less continuous, corresponding to thinner films, the absolute value of the T.C.R. becomes progressively smaller until negative values are observed with respective zero T.C.R.'s at about 35 and 150 ohm per sq, respectively. Recently the author7 investigated the behavior of a multicomponent alloy of nickel, chromium, and iron and found the T.C.R.'s of these films decrease with decreasing substrate temperature during deposition. The lower T.C.A. associated with lower substrate temperatures was attributed to an increased contribution to the total resistivity from the negatively temperature-dependent gap tunneling since it is well-known that thin films deposited on low-temperature substrates consist of a higher density of smaller grains than the same sheet resistivity films deposited on higher-temperature substrates. Under conditions of thermal anneal, the author found that, when various sheet resistivity films fabricated at 300°C substrate temperature are exposed to extended storage in air at 300°C, the thinner films increase in resistance until open, while the thicker films

Jan 1, 1967

By DFI DFI

An Online Conference

By Danell. R. E.

A drill monitoring system has been developed which measures performance characteristics of a rotary drill and relates this to the material strength and rotary specific energy. The drill monitor is computer based and is used to produce a profile of the relative in-situ material strength as a function of depth. This information has been used in determining the placement of explosive in selective loading of blastholes and estimating the amount of lump product in a particular section of an ore body.

Jan 1, 1989

By S. K. Singh, J. Shepherd

"Feather edging"- a major source of injury and fatal accidents in Australia, South Africa and USA, refers to a phenomenon where the roof, at the goaf edge, falls as a thin wafer of rock often suddenly, over-riding conventional timber breakerlines. It may run down and affect adversely a working bord at distances of 15 metres or more from the goaf edge. Feather edging typically occurs in relatively massive, strong roof strata such as sandstone or conglomerate. This paper presents the results of a mine trial where a concentrated row of fully grouted bolts were able to resist the feather edging in the first comprehensive, monitored trial in an Australian pillar ('total') extraction coal mine.

Jan 1, 1999

By P. Harris

"Comparison of the two most commonly used classes of depressant in the South African platinum industry is complicated by the fact that these polymers induce different effects on the surfaces onto which they adsorb. The use of carboxymethyl cellulose (CMC), which is ionically charged in solution, can lead to increased particle dispersion in addition to the effect of reduced surface hydrophobicity (depression). Guar is typically only slightly charged in solution. Comparison of these two depressants is complicated since it is uncertain whether differences in their action is a result of either depression of dispersion effects.This work investigates the role of dispersion independently to that of depression in the batch flotation of a platinum bearing ore. An inorganic dispersant, sodium hexametaphosphate (NaHMP) was added in parallel to the uncharged guar depressant to simulate the action of depressants with varying degrees of dispersion. By distinguishing between the material recovered by entrainment and the floatable gangue and by including the effects of froth stability it was possible to decouple the effects of dispersion and depression.The results show that both dispersion and depression led to increased grade of the sulphide minerals. Depression leads to a decreased recovery of floatable gangue minerals. Dispersion leads to an increased recovery rate of these minerals and an accompanying decrease in froth stability."

Jan 1, 2003

By Daniela Venter, Stephen Chryssoulis, Ken Stowe

"A sampling campaign was conducted at Kemess in order to identify and assess the chemical and physical factors, which control free gold flotation kinetics in the rougher and cleaner circuits. The rationale behind this approach was that accurate knowledge of the parameters affecting free gold flotation kinetics, can be used to determine how to accelerate free gold flotation. Collected samples were composites of 5-6 cuts over a four-hour period, at steady plant conditions.In the rougher circuit, coarser equidimensional gold particles floated ahead of the finer grained and the flaky gold. Sulphur followed by molybdenum and to a lesser extent silver enhanced gold flotation kinetics, while hydroxyl followed by carbonate ions induced depression."

Jan 1, 2003

By Matti Kongas, Kari Saloheimo, Antti Remes

"The paper studies the control performance of the flotation process as a function of the measurement accuracy and sampling frequency of an on-stream XRF analyzer, using a simple dynamic model. An additional aim is to assess how the economical result of a mineral flotation process depends on the quality of process control based on the on-line elemental assays.An on-stream XRF analyzer measures the concentrations of slurry lines in a continuous cycle from several process points. The control performance depends on the analytical accuracy and sampling frequency of the concentration measurement. With a long cycle time, the state of the process changes before a new measurement becomes available. With short measurement times the statistical variance of the counted Xray pulses increases, increasing the random error in the analysis. In addition, the measurement accuracy depends on the concentration of the component to be measured from the slurry.To quantify the effect of analysis error and frequency to process control, a simple dynamic process model is created in the Matlab environment. Data from a copper flotation circuit is used as a test case. The process model comprises a first order reaction equation and the grade-recovery -relationship estimated from process data. The control was modeled using the control strategies implemented into a rule based advanced control system. The economical performance of the control was studied by calculating the overall net smelter return at various analyzer parameter combinations."

Jan 1, 2003

By Briony C. Ruse, David V. Boger, Fiona Sofra1

"The sustainability of the mining industry must be addressed through improving tailings management. The use of thickened tailings and pastes stems from a paradigm shift towards designing tailings disposal sites to suit their surrounding environment, rather than manipulating the environment to accommodate the tailings. Thickened tailings and pastes usually exhibit non-Newtonian behaviour, so a thorough understanding of the rheological characteristics of the material is required in order to determine the disposal plant operating conditions.As environmental factors translate into economic issues, minimising waste production using dry disposal methods is gaining popularity. The use of rheological information is of high importance in evaluating the spreading characteristics, the transportation and the dewatering of thickened mineral tailings. The principles outlined may be applied to many industries encompassing a wide range of waste materials. The main obstacle to the widespread implementation of dry disposal methods has been the high initial capital cost of the methods due to the dewatering step, and the high cost of pumping thick suspensions across any great distance. Proper and thorough costing of tailings disposal activities combined with an accounting approach that shows closure and post-closure care costs on a per tonne basis of tailings disposed throughout the life of the tailings facility will show that dry disposal methods are more favourable than they might seem on initial appraisal."

Jan 1, 2003

By C. K. Leith

CERTAIN ideas on iron and steel sanctions to follow originated in a series of conferences held under the joint auspices of the War Department and Brookings Institute in Washington last spring. The views presented may be regarded as those of substantial segments of the steel industry. In view of the fact that steelmaking capacity can be so quickly converted to the production of armament, any effective control must necessarily include the entire steel industry and not solely the parts devoted to the production of implements of war. It must also be exercised all the way from production and shipment of raw materials through their ultimate conversion into finished products and use. Control will be dis- cussed under two main headings: (I) control of raw materials at the source; (2) control of steel capacity within the Axis countries.

Jan 1, 1944

By Sergio N. Monteiro

Polymeric matrix composites reinforced with coir fibers are being used in many industrial applications such as automobile interior panels and cushions. These composites have relatively low mechanical strength due to the weak fiber/matrix interface. The objective of the present work was to investigate the effect of a surface alkali treatment of the curaua fiber on the mechanical behavior of polyester composites with different amounts of these fibers. The treatment, also known as mercerization, was performed with distinct concentrations, 0.1 and 10% of NaOH at 1 min and 1 hour, before incorporation of the coir fibers into the polyester composite. The results showed no significant change in comparison to similar untreated coir fiber composites. A microstructure analysis revealed that, in addition to reducing the hydrophilic characteristic of the fiber,the treatment also affects the surface morphology and impairs the fiber/matrix interfacial strength.

Jan 1, 2009

By R. E. Perry

To develop new or improved flotation methods for beneficiating low-grade red iron ores, the Bureau made many bench scale and continuous anionic flotation tests on ferruginous sandstones and calcareous iron ores from the north-eastern part of the Birmingham, Ala., iron district. The ores contained about 21 to 36 percent iron, a to 11 percent lime, and 22 to 64 percent silica. Production of iron concentrates containing 48 to 52 percent iron was technically feasible in batch tests, and the iron recoveries ranged from 85 to 92 percent. In continuous tests 49 to 51 percent iron products were obtained with 80 to 90 percent recovery.

Jan 1, 1962

By Patrick J. Doig

The Lewis Street CSO Tunnel is an important element in the efforts of the Metropolitan Government of Nashville and Davidson County (Metro) to improve the treatment of waste-water in the area. The tunnel is approximately 1,675m (5,500ft) long with a finished diameter of 2,600mm(102inches). 116m (380ft) of tunnel was constructed in soil with the balance being in lime-stone rock. Excavation was with a 3,700 mm (12ft) diameter Jarva hydraulic shield in soil and a Jarva Mark 12 TBM in rock. The permanent lining of the tunnel comprised concrete pipe with steel end-rings and a vinyl liner. This paper describes the construction of the project with particular emphasis on the excavation and lining of the tunnel.

Jan 1, 1997

By C. J. K. Purdy, H. E. Jamieson

"The comprehensive assessment of the environmental impacts of mining rare earth element (REE) deposits depends on a sound knowledge of the mobility of REEs in low-temperature aqueous environments. Temperature, pH and water chemistry are important factors controlling the aqueous mobility of REEs, while REEs are known to readily form complexes with both inorganic and organic ligands, and it has been shown that sorption and colloid formation may play an important part in dictating REE transport in the low temperature weathering environment. Ore and host rock mineralogy is also a key factor controlling the extent to which REEs are leached from mine waste. INTRODUCTIONThe aqueous mobility of rare earth elements (REEs) has commonly been explored in the past due to their potential application as tracers of geochemical processes in aqueous systems. REE mobility in low-temperature solutions has been shown to be dependent on the pH, temperature, ionic strength, and solution chemistry. For example, the aqueous transport of REEs can be modified by complexation with organic and inorganic ligands (Johannesson & Zhou, 1999; Klungness & Byrne, 2000; Luo & Byrne, 2004; Schijf & Byrne, 2004; Tang & Johannesson, 2010; Wood, 1990, 1993), or through sorption to suspended particles and colloids (Bau, 1999; Quinn, Byrne, & Schijf, 2004, 2006a, 2006b, 2007; Sholkovitz, 1995). Here we review the coordination chemistry, sorption behaviour and potential colloid association of REEs with respect to low temperature aquatic settings.RARE EARTH ELEMENT CHEMISTRYREEs include lanthanum to lutetium of Group IIIA in the periodic table. All share very similar chemical and physical properties. Often included in REE studies is another Group IIIA element, yttrium owing to its similar properties, and occasionally scandium, although its considerably smaller ionic radius makes for different properties and will not be discussed further here. The REEs are often subdivided into the light REEs (LREE), La to Sm, and the heavy REEs (HREE), Eu to Lu, which also usually include Y (hence are often referred to as YREE). The REE may be subdivided further into the LREEs, middle REEs (MREEs), and HREEs, in which case each classification includes La-Nd, Pm to Ho, and Er to Lu as well as Y, respectively, although definitions vary throughout the literature."

Jan 1, 2012