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By B. R. Zernich

Advances in tunneling technology, such as Earth Pressure Balance and Slurry Shield methods, have allowed the tunneling industry to construct tunnels in increasingly difficult ground conditions. In recent years, a number of civil projects including large diameter train tunnels, subway tunnels, water tunnels, sewer tunnels, and combined sewer tunnels have been successfully completed deep beneath the water table in soft ground conditions utilizing modern day Tunnel Boring Machines (TBM). With the increase in difficult ground conditions and higher water pressure comes the inherent need to utilize compressed air to gain access to the TBM?s cutterhead and cutting tools. This paper focuses on one such instance in Los Angeles, CA in which Traylor Brothers Inc. performed a cutterhead intervention by compressing the heading of an 11-foot diameter tunnel to approximately 3 bar gauge pressure. This paper focuses on the environmental controls used to manage ventilation, oxygen levels, temperature, and pressure, as well as discusses the problems associated with toxic gases and the increased risk of fire. The paper will also cover the physical science of the environment and the increased risks of performing basic job functions while in a compressed air heading.

Jan 1, 2009

By L. K. Marshall

Last month's engineering fundamentals article discussed some general considerations of underground mine ventilation. This month's article takes a look at auxiliary ventilation-brattice, fans, and ducting-in underground mines. The need for good, efficient auxiliary ventilation increases as mines get deeper and move farther from ventilation shafts. New mining methods and equipment resulted in faster work area advances, liberating more dust, gas, and heat. As a result, worker health and safety requirements in the face area have become more stringent. For all these reasons the safety and efficiency of any underground mine depends heavily on its auxiliary ventilation. The purpose of such ventilation is to supply sufficient quantities of clean air to the face of the drift and to maintain air quality within desired limits until expelled from the mine.

Jan 2, 1982

By Deepak Vidyarthi

This paper deals with the significance of Explosive Energy in the optimization of blast design parameters, and the benefits emerging out of it. It is based on the original work done by the author in developing and successfully implementing a site-specific software package on ‘Blast Design Optimization’ at Kudremukh Iron Ore Mine in India with a production level of 22.5 million tonnes of crude ore and off-take of Explosives of approximately 5500 tonnes per annum. The software package has yielded tangible results in effecting reduction in Explosive Consumption, substantial savings in the Cost of Explosive, besides Environmental Improvements by way of attenuation of Blast Induced Ground Vibrations as well as Air-Blasts. By carrying out regular ‘Regression Analysis’, and determination of the Rock Constants, it has been possible to further develop software packages as well as prediction curves for prediction of Peak Particle Velocity, Safe Charge of Explosive, Air-Blasts etc. A model has also been developed for the prediction of ‘Fly Rock’ although at KIOCL, fly rock does not pose any problem.

Jan 1, 2006

By Alan B. Wagner

Data from seven instrumented pile load tests in Milwaukee, Wisconsin and two other instrumented load tests reported in the literature, one in Evanston, Illinois and one in Houston, Texas were reviewed. The data were for pipe piles having diameters from 9-5/8 inches to 18 inches, driven to depths between 36 and 96 feet. These data were used to develop a relationship between effective vertical stress and unit side friction and unit end bearing. These relationships were based on readily measured soil parameters, undrained shear strength, Cu, and Standard Penetration Test (SPT) values. This Beta (ß) and Nt approach and four other methods were then used to calculate the bearing capacity of the nine cases analyzed. The results from each of the methods are compared with the measured results.

Jan 1, 1991

By Taylor R. G

This paper reports a biogeochemical study of the Siberia lode of the Herberton tin field. Soil near the orebody contained high levels of Fe, Cu, Pb, Sn, As, Mld Mn. Polycarpaea spirostylis and Indigofera dominii were associated with these high levels but several other species apparently could not tolerate them. The potential of these species as indicator plants is discussed.

Jan 1, 1975

By Héctor Quispe

El presente trabajo señala la aplicacíón de las estrategias en Sistema de Gestión de la producción en la mina Raura, de forma que mejore su administración de flujo de recursos y actividades para lograr óptimos resultados con mayor productividad. Entre sus principales objetivos están: la determinación de los stándares de producción en tonelaje, leyes, costos y plazos, que hagan rentables los procesos de operación minera, la definición de sistemas standarizados que generen valor económico en cada uno de sus procesos. Asmismo, se realizó un diagnóstico previó que abarcó los procesos de geología, planeamiento, exploración, explotación, beneficio de minerales en planta concentradora, mantenimiento y proceso de comunicación gerencial. Los resultados y datos de este diagnóstico tiene como base la referencia para la evaluación y avance del proyecto.

Sep 13, 2001

By H. Boghosian

This paper presents the design and construction of a deep basement in a steeply sloping site in glacial till in Glasgow city centre. Existing foundations, adjacent structures and services, in tandem with asymmetric loading, presented particular challenges in the planning, execution and design of the project. The construction methods and temporary works, analysis by the Finite Element method and monitoring carried out are all described.

Jan 1, 2006

"AQUILA Mining Systems Ltd. is a Canadian company that designs and develops monitoring, control and navigation systems for the surface and underground mining industries. In 1992, AQUILA Mining Systems began the development of technology for monitoring, controlling and positioning mobile mining equipment. In 1993, AQUILA completed its first field test with GPS receivers onboard ablasthole drill, and thus demonstrated the viability and strategic relevance of this technology in surface mining. Since then, AQUILA has installed GPS-based technology on drills and shovels in several Canadian mines. This paper will review the development of these systems and discussthe benefits the mining industry could realise through their production implementation."

Jan 1, 1997

By Miguel Callasi

El proyecto tiene como objetivo mejorar la seguridad y automatizar procesos de monitoreo utilizando sensores e IOT para prevenir accidentes tanto en instalaciones de almacenaje y lugares de trabajo, en cuanto a la monitorización y administración de los datos será realizado por el supervisor en seguridad de la planta minera. Para la realización de este proyecto su utilizará plataformas de hardware libre como el ESP32 se propuso emplear una batería recargable y sensores de medición de ambiente y detección de gases, este sistema es completamente inalámbrico ya que la plataforma integra wifi y Bluetooth los datos se enviarán gracias al protocolo de comunicación MQTT.

Sep 29, 2023

By Stanislaw Siewierski

One of the major problems in the exploitation of deep copper ore deposits in the Legnicko-Glogowski Copper Field is ground control and, in particular, roof control of the headings. The depth of copper deposits ranges from 600 to 1200 m. The parameters of ore-bearing rocks and the surrounding rocks show considerable variance of strength properties along the mining thickness (Fig. 1). The roof of the openings exploitation headings consists of dolomite-calciferous rocks. The roof strata consist of layers, the thickness of which vary from several centimeters to 0.6 m (sometimes to 1.0 m). These strata differ in strength and are characterized by igneous and sedimentary discontinuities. On the basis of studies in structure, properties and geological mining conditions of the roof strata in Polish copper mines, the method of roof classification has been developed. (1) This method uses the stability index "L" of the roof, calculated from [ ] The value of "t" ranges from 0, l to 0,8. Based on the value of "L", four classes of the roof (Table 1) corresponding to different degrees of fall hazard have been developed. The mining of copper ore deposit is carried out by a single lift room-and-pillar mining system or a two-stage room-and-pillar system with roof caving. (3, 4). The single lift room-and-pillar mining system is most often used. It consists in working of the deposit of 2.5 to 4.5 m mining thickness, 150-350 m long mining line, consisting of parallel room faces 6 m wide with pillars 5.7 or 16 m wide. As the mining line advances, cross-cuts joining individual rooms are made, thus forming support pillars 3x5, 7x7, 5x16, and 7x16 m (Fig. 2). The two-stage system (Fig. 3) mines the deposit with rooms 6 m wide into blocks 25 x 35 x 25 x 45 m. During the second step these pillars are worked with rooms and cross-cuts into pillars about 3 x 4 to 4 x 5 m (retreat mining). The pillars are crushed just before the fall of the roof. The maximum opening of workings in the two-step system is about 10 m, i.e. one belt entry and one row of bearing pillars. In single lift room-and-pillar systems it is about 35 m., i.e. three belt entries and three rows of bearing pillars. The support of the headings consists of expansion bolts 1.6-1.8 m installed in a bolting pattern 1.1 x 1.5 m. In both systems the fall step is about 10 m, i.e. the width of a belt and a bearing pillar. The Indications of Rock Mass Pressure Individual Dog Heading Individual dog headings are set wide apart from each other in the unmined ore deposit area where there is no interaction of headings. The indication of rock mass pressure are, in such cases, limited to the deformations and damage of side walls. Radiometric studies of rock mass loosening showed that the maximum range of lifts in side-walls immediately after web was 2 m (4,5). In the course of time the cracked side rocks fall off, thus widening the heading. The morphology of side-walls is influenced by the location of the heading in relation to clump layer/tarry. This layer is characterized by a weak strength and "lubricating" properties. The location of the heading in

Jan 1, 1982

By Zhuofei Yang, Jidong Kang, David S. Wilkinson

The fatigue behavior of AM60 high pressure die casting magnesium alloys was studied in a straincontrolled manner. The fatigue test was interrupted every 2,000 cycles for X-ray tomography scanning. The specimen was removed to be scanned on a desktop micro-CT system. The value of using X-ray tomography in a fatigue properties study was assessed with respect to porosity, cracks and fracture surfaces. The 3D analysis and model results showed porosity could be well measured and modelled in 3D. Defects bands are made of pores under 50 µm in volume-equivalent sphere diameter. Larger pores are randomly distributed in the region between two defect bands. Observation of cracks by X-ray tomography occurs in three ways such that the 3D model gives the best illustration of crack-porosity interaction while the other two methods have better detectability on crack initiation and crack tip observation. X-ray tomography is also of value in failure analysis on fracture surfaces. By summarizing X-ray tomography data during fatigue testing and observing fracture surfaces on a 3D model, a better understanding on the crack initiation, crack-porosity interaction and the morphology of fracture surface is achieved.

Jan 1, 2014

By Jose A. Delgadillo

The hydrocyclone problem has been a challenging task for the last 30 years. In the 80’s and 90’s Computational Fluid Dynamics solution to this problem began to appear. These were unsuccessful due to over simplification. In the past 3 dimensional solution with ?-e model and Reynolds Stress Model have been published. In this paper RSM and ?-e models are compared with velocity profiles measured in 75 mm and 250 mm diameter hydrocyclones. It is shown that results are not satisfactory with RSM or ?-e and that a model called Large Eddy Simulation is needed to describe velocity profile evolution and size classification.

Jan 1, 2005

ignitions caused by cutting tools have occurred at a rate of some 14 per year in UK coal mines since 1965, mostly on the coalface. The rate has held steady despite reducing output and number of collieries. Investigations were carried out over this period into factors affecting both the concentration of firedamp in the cutting zone and the igniting source. A study into detecting and suppressing ignitions on shearers has been undertaken and it is feasible to prevent certain ignitions from spreading outside the cutting zone. Practical measures have been adopted by British Coal to identify frictional ignition sites and to lay down working procedures to minimise risk.

Jan 1, 1988

By J. E. Sepulveda, R. Morrow

"In full scale mineral grinding operations, the steel balls normally utilized as auxiliary grinding media get to be consumed at different specific rates, as determined by 3 basic mechanisms: abrasion/corrosion (wear), impact ball breakage and impact surface spalling, the latter relating to the removal of rather small pieces of steel coming off the exposed surface of the balls due to repetitive impact with other balls in the charge or the surrounding mill liners. In conventional ball milling applications, the clearly predominant mechanism is gradual wear by abrasion/corrosion. In the case of SAG mills, where the make-up balls may be as large as 6”f diameter, breakage and spalling mechanisms are significant contributors to total ball consumption, although not to the extent of overriding wear mechanisms.Ball wear has been well characterized by the Linear Wear Theory, as presented at the last CMP 2014. Impact breakage has been customarily monitored, at the ball manufacturing site, via Drop Ball Tests (DBT) consisting of repeatedly dropping balls from a standard height and accounting for the number of broken balls and the weight loss (spalling) of the remaining unbroken balls. When properly conducted, DBT’s should provide meaningful indications of the breakage and spalling resistance of large diameter balls. The current publication is focused on the interpretation and projection of DBT results to full industrial scale, taking into account all 3 mechanisms of grinding media consumption in SAG mills.INTRODUCTIONA thorough, quantitative understanding of the independent contribution of all active grinding media consumption mechanisms is of the highest practical relevance, particularly in semiautogenous (SAG) milling operations where ball breakage and spalling can not be ignored or neglected, as it has been normally acceptable for conventional ball milling processes. The high severity impact conditions currently imposed in typical SAG mill environments create serious challenges to the manufacturers and suppliers of large diameter (5”–6”) SAG balls, whose products must be capable of surviving such harsh operational conditions with minimum breakage or spalling."

Jan 1, 2015

By Craig Compton

Falls of small pieces of rock from between roof bolts continue to cause fatalities and to injure hundreds of coal miners each year. Roof screen is the most effective way to prevent these incidents, but some mines are reluctant to use it because they believe installing screen can be awkward, expensive and time-consuming. The most common type of roof bolting machine used in mines today is the dual boom, outside-controlled roof bolter. Mines who install roof screen using these machines have developed some machine modifications and techniques to ease roof screen installation. This paper describes some successful techniques and machine modifications that are being used in productive mines to assist with roof screen installation. Since the material handling involved with roof screen installation can expose miners to an increased risk of musculoskeletal injuries, the National Institute for Occupational Safety and Health (NIOSH) ergonomists, designed machine modifications and implemented a series of tests to evaluate roof screen handling procedures for outside-controlled, dual boom roof bolting machines. Roof screen installation can also have a positive economic impact on a mine by reducing the cost of injuries, workers? compensation, required spot or re-bolting, and clean-up of long term travel and belt entries.

Jan 1, 2007

By Jacob Masliyah, Zhiang Zhou, Tshitende Kasongo, Jianjun Liu, Zhenghe Xu, Jeawon Choung

"Slime coating is a recognized challenge in fine particle flotation, not only in decreasing recovery, but also in reducing the selectivity and hence froth quality. In this presentation, a novel method based on electrophoretic mobility distribution measurement to study slime coatings is described. By measuring electrophoretic mobility distribution of individual minerals and their mixtures, the interactions between these minerals can be evaluated.For illustrative purposes, a model system of fine coals, or oil sands with two different types of fine clays was studied. Flotation tests showed a significant decrease in coal (bitumen) flotation recovery with montmorillonite but not with kaolinite clay addition. When electrophoretic mobility distribution of a fine coal/montmorillonite clay mixture was measured, a single modal zeta potential distribution was obtained, in contrast to a bimodal distribution for fine coalkaolinite clay mixture. This finding suggests a stronger adhesion of montmorillonite than kaolinite clays on fine coal surfaces. In the case of bitumen, the bimodal zeta potential distribution was measured for the mixture of bitumen emulsion and kaolinite or montmorillonite, indicating a weak attraction of the clays by bitumen. In the presence of calcium, however, a single modal zeta potential distribution was obtained in the mixture of bitumen emulsion with montmorillonite but not kaolinite clays. These findings are in excellent agreement with bitumen flotation results, demonstrating that the electrophoretic distribution measurement is a powerful tool to study slime coating phenomenon in a complex fine particle flotation system."

Jan 1, 2002

By David Turnbull

IN isothermal recrystallization processes, new crystals generally grow into the matrix until they impinge upon other new crystals or an external surface, at constant linear rates G. Before impingement the perceptible course of growth can be described by the equation: 1 = G(t-7) C1I where, G = dl/dt, 1 is a crystal dimension measured in a constant direction, t is the time, and 7, the nucleation period, is a positive intercept on the time axis. Fig. 1 is a schematic representation of I as a function of time for a recrystallizing grain. G is dependent upon temperature, driving energy (strain or surface energy), relative grain and boundary orientations, but is generally independent of time. The frequency of nucleation, fi, (time" volume") can be defined by the equation: N = 1/fV [2] where ? is the mean nucleation period and V is the volume of the specimen that has not recrystallized. The kinetics of primary and secondary recrystallization generally can be described satisfactorily in terms of the parameters N and G only.'-" After recrystallization is complete the average grain size 7 increases with time by "normal grain growth;" didt, the average rate of grain growth, is strongly time dependent and has not yet been precisely related to G for the motion of the individual grain boundaries constituting the system. It has been suggested4* " that the elementary act in grain boundary migration is closely related to the elementary act in grain boundary self-diffusion. Although the distance of atom movement in the two processes may be somewhat different, there is reason to expect that the activated states may be very similar, so that the free energy of activation for grain boundary migration should be of the same order of magnitude as for grain boundary self-diffusion. Therefore, it is desirable to develop a satisfactory basis for comparing data on self-diffusion and grain boundary migration and to make such comparisons where possible. Theory The formal theory of grain boundary migration rates is analogous to the theory for the rate of growth of crystals into supercooled liquids reviewed elsewhere 6-8. Boreliuss has shown that the latter theory describes, within the theoretical uncertainty, the growth of selenium crystals into supercooled liquid selenium. Motto and more recently Smolu-chowski" have derived expressions for the rate of boundary migration in recrystallization. The treatment to be presented is similar to Mott's excepting that the formalism of the absolute reaction rate theory will be used. The atomic mobility, M, in grain boundary migration is defined by: G = -M6p/6x where p is the chemical potential per atom and x is the coordinate measured in the direction of grain boundary movement. Let AF be the free energy difference per gram atom on the two sides of the boundary and k the thickness of the boundary. For RT>>AF the potential gradient across the boundary (6p/6x) is essentially linear and it follows that: SF/8x = - aF/N\ [4] where N is Avogadro's number. According to the Nernst-Einstein equation, M is related to a diffusion coefficient, Do, for matter transport in grain boundary migration by the equation: M = Da/kT [5] Substituting eqs 4 and 5 into eq 3 gives the basic relation between Do and G: G = DoaF/\RT [6] Do values may be calculated from experimental values of G from eq 6 and directly compared with the coefficient of self-diffusion within the crystal, DL, or the grain boundary self-diffusion coefficient D,. However, a more convenient, though equivalent, basis for comparing atomic mobility in grain boundary migration and self-diffusion is through the constants of the absolute reaction rate theory. According to this theory diffusion coefficients may be written:" D = k2(kT/h) exp [-AF,/RT] 171 aFa, the free energy of activation, is related to the measured energy of activation, Q, by the equation: AFA = Q - T aSx - RT [8] where aSa is the entropy of activation. Substituting eqs 8 and 7 into eq 6 gives: G = ek(kT/h) (aF/RT) exp [(AS,,)C/R] exp C-Qc/RTI C91 where the subscript G refers to boundary migration. The relationship between the driving free energy and the free energy of activation in boundary migration is indicated schematically in Fig. 2. Experience indicates that the variation of G with temperature can be described by: G= Go exp [- Qc/RT] [10] where Go and Qc are generally temperature independent over wide ranges of temperature. Comparison of eq 9 with eq 10 gives:

Jan 1, 1952

By Adam Powell, Matthew Earlam

INFINIUM, Inc. is scaling up a new molten salt electrolysis process for producing rare earth metals. Instead of conventional carbon anodes, this process uses Pure Oxygen Anodes™ which employ a stabilized zirconia solid electrolyte between the molten salt and anode. This eliminates two problems with today's rare earth metal production technology. First, it eliminates carbon anodes and contamination of the product by carbon and its impurities, enabling 10-100 times larger batch size than current practice, and lower labor costs. Second, it eliminates emissions of perfluorocarbons (PFC) such as CF4 and C2F6, which are very problematic greenhouse gases with 6000+ times the global warming potential of CO2. The zirconia also enables a sealed vessel with no LiF emissions, creates a reducing environment enabling use of low-cost welded steel vessels, and either produces a high-purity oxygen by-product or can use natural gas to reduce the necessary electrical energy with no HF production. This paper will describe the technology and its current status for rare earth metal production.

Jan 1, 2014

By V. Brabie, S. Jansson, L. Bohlin

The rate of dissolution of solid MgO-C and doloma into liquid in CaO-Al2O3-SiO2-MgO slag at different temperatures was studied under conditions of forced convection by rotating cylindrical refractory specimens in a stationary crucible containing the molten slag. The corrosion rate was calculated from the change in diameter of the cylindrical specimens. Refractory specimens were 13 mm in diameter and 70 mm long. The specimens were rotated for15 to 120 minutes at speeds of 100 to 400 rpm in the molten slag. The rate of corrosion increased with temperature and with the rotating speed of the rod, and decreased when the slag was nearly saturated with MgO. The experimental results confirm the assumption that the diffusion of magnesium oxide through the slag phase boundary layer controls the corrosion process. The corrosion mechanism seems to be the dissolution of the refractory materials into the slag, followed by penetration of pores and grain boundaries and dispersion of the grains in the slag. Keywords: MgO-C refractory, doloma refractory, molten slag, corrosion rate, corrosion mechanism

Jan 1, 2004

By E. T. Turkdogan

Jan 1, 1962