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By A. Giacomini, M. Nazem, E. Fathi Salmi

"Numerical simulation of collapse of tunnels in weak rocks is one of the challenging problems in rock mechanics. Collapse can impose technical and financial difficulties during the construction of underground excavations. This phenomenon, particularly in shallow excavations, may lead to propagation of a caved zone toward the surface and formation of chimney subsidence. Chimney subsidence has numerous catastrophic consequences such as the adverse environmental impacts and damage to surface structures in vicinity of excavations. Due to the importance of subsidence in civil engineering, the main goal of this study is to propose an appropriate method for preventing the formation of subsidence in shallow tunnels in weak rocks. The Dolaei road tunnel is investigated as a case study, where a large chimney subsidence has occurred. The geology of the area and the geostructural characteristics of the rock mass surrounding the tunnel are briefly reviewed in this paper. Two-dimensional as well as threedimensional numerical simulations are conducted to study the tunnel stability. Moreover, the effects of staged excavation and pre-supporting method on controlling the ground movements are studied. Outcomes of this study indicate that employing forepoling and staged excavation can be a practical remedy to control the ground movements and prevent the formation of chimney subsidence.INTRODUCTIONPredicting the formation of subsidence, mainly sinkhole subsidence over civil or mining excavations, is a very challenging task. An accurate prediction of subsidence is required for selecting an appropriate control and mitigation system to reduce the level of ground movements and its impact on the surface life (Bétournay et al. 1994; Leca and New 2007). Excavations, particularly in weak grounds, could result in surface subsidence; they modify the in-situ stress conditions as well as the hydrogeology of the area. Construction of unsupported excavations in soft soils and relatively weak rocks usually leads to the formation of a failure zone behind the face. In a very soft ground, the failure zone can extend towards the ground ahead of the tunnel face. Propagation of this zone toward the ground surface results in generation of sinkholes."

Jan 1, 2015

By F. P. Hassani, M. Hefni, M. F. Kermani

"This study is part of large and an ongoing investigation into the development of a light-weight and highly fluid mine fill for various applications in mining and civil operations. Foam mine fill is the new material proposed for backfilling mines, and is fabricated by mixing stable foam into a mixture of tailings, binders, and water. This paper investigates the effects of both binder dosage and the amount of foam used upon the mechanical and physical properties of foam fill, mainly in regards to compressive strength, porosity and density.Samples were prepared using tailings from a copper mine as the inert material, Normal Portland Cement as the main binding agent, and a foaming agent with a foam generator. Samples were cured for 7, 14 and 28 days and were then subjected to unconfined compressive strength (UCS) testing. Select samples were subjected to mercury intrusion porosimetry, so as to study the microstructural properties. An empirical model was then developed, using a response surface methodology to establish a relationship between the investigated parameters. INTRODUCTION AND BACKGROUNDThe disposal of mine tailings is a significant issue in the mining industry, particularly as mine production increases. Many mines re-use mine tailings for backfilling, which is a method for reducing environmental exposure to tailings, maintaining underground stability, and increasing ore recovery (Benzaazoua, Belem & Bussière, 2002).This paper introduces a new type of backfill called ‘foam mine fill’. This proposed backfill material is similar to cellular concrete, as air bubbles are entrained in cement or lime mortar, resulting in a cellular structure (Narayanan & Ramamurthy, 2000). Air voids can occupy up to 70% of the volume of concrete, which makes it light- weight, and thus can be used for a wide range of civil applications, including backfilling (Tarasov et al. 2010; Panesar, 2013). Unlike cellular concrete, the incorporation of air bubbles into a mixture of tailings, binder and water makes foam fill a potential new backfilling material. Furthermore, a preliminary investigation on foam fill samples found that pulp densities should be optimized before adding the foam, in order to produce consistent samples without foam segregation or losses (Hefni et al., 2014)."

Jan 1, 2015

The morphology of environmentally assisted cracks in stressed pipeline steel has been investigated, For a dilute and neutral solution (NS4) simulating ground water in contact with the steel, semi-elliptical cracks grow faster on the surface (2c) than in the depth (a), hence, the aspect ratio (a/c) decreases, This is explained using a deterministic concept since corrosion is dominant and the primary constraint is the conservation of charge, By contrast, when mechanistic conditions prevail, significant growth occurs in the depth, When underloads are imposed in the loading history, temporary accelerations in crack growth occur because corrosion rather than mechanical effects become dominant.

Jan 1, 2005

By D. Nie, M. Ren, T. Mo

This paper studied the phenomenon of room temperature creep deformation at crack tip and its effect on fatigue crack growth rate of a X-70 pipeline steel using compact-tension (CT) specimen on a MTS 810 testing machine. Time-dependent deformation at the crack tip under constant load was observed in this steel at room temperature and the amount of deformation produced was seen to depend on loading rate and the magnitude of stress intensity factor. It is found that there exists a critical stress intensity factor below which the deformation decreases with time when the applied load remains constant. It is also found that the occurrence of room temperature creep obviously affects the subsequent fatigue crack growth rate. The observed behavior was explained based on dislocation theory.

Jan 1, 2005

By C. Yoo

"Geosynthetics engineering has made phenomenal advances during the last decade in areas of manufacturing as well as practical applications. As a result, geosynthetics are now being recognized as essential construction materials that can be used to facilitate construction, ensure better performance of the structures and reduce the long-term maintenance in routine civil engineering works. The creative use of geosynthetics in geo-engineering practice is expected to continuously expand as innovative materials and products are becoming available. In this paper, a wide variety of geosynthetic products available to geoengineers to solve a wide range of problems are briefly presented along with their functions and possible applications. Fundamentals of geotextile filter design principles are then introduced for use in the tunnel drainage system. Practical applications of geosynthetics relevant for tunnel engineering are also highlighted with emphasis on the issues associated with the geotextile filter application for use in the tunnel drainage system.INTRODUCTIONGeosynthetics have emerged as essential engineering materials in a wide range of civil engineering applications, e.g., transportation, geotechnical, geoenvironmental, hydraulics, and private development since the first geosynthetic conference in Paris, 1977 (Koerner 2012). Due to their costeffectiveness, ease of installation, and well established mechanical and hydraulic properties, geosynthetics are now playing important roles in the field of geo-engineering.As indicated in the 9th Bucahanan Lecture paper by Holtz (2001), major developments in civil engineering have only been possible with the parallel developments in the technology of construction materials. For example, larger scale structures became possible with the help of developments in concrete, reinforced concrete, and prestressed reinforced concrete technology which replaced wood and building stone as construction materials. The best example of a parallel development in geo-engineering between the material and the geotechnical application may perhaps be the soil reinforcement technology which has a direct analogy with reinforced concrete as a polymeric reinforcement material provides added level of tensile resistance and stability to soils that have little to no tensile strength, thus giving additional margin of safety."

Jan 1, 2015

By K. Nikkhah, N. Dhadli, G. Freeman

Ammoniacal pressure leaching operations have been in commercial use at the Fort Saskatchewan refinery of Sherritt International Corporation since 1954. Recent improvements have significantly increased the capacity of this circuit. The computer modeling of this process has proved to be a valuable tool in facilitating the evaluation of different operating scenarios in an effective manner. Reagent response in the ammonia leach of nickel and cobalt sulphides is examined using the dynamic process simulation capabilities of IDEAS(TM) software. The dynamic simulation enables accurate measurement of the sensitivity of the process to variables such as temperature, feed rate and ammonia concentration as well as compartmental analysis of metals concentration, pulp density, vent gas composition, and the formation of specific complexes. The complexity of the ammonia leach process makes it a logical choice for evaluation by computational analysis. The methodology for dynamic modeling of a pressure leach process is presented.

Jan 1, 2005

By Louise Grondin

Laronde Mine has been working for a number of years to identify substances that could contribute to process water toxicity and to find an effective way of removing these contaminants from the water. Initial studies have identified ammonia, nitrite, cyanide, thiocyanate, cyanate, dissolved organic carbon, copper and zinc as potential toxicants. Bench-scale tests were carried out with Lakefield Research to find a water treatment process that could effectively remove the suspected toxicants. Nine treatment processes were evaluated: 1) granular activated carbon (GAC) filtration followed by zeolite, 2) zeolite filtration followed by GAC filtration, 3) aeration followed by GAC filtration, 4) multi-stage GAC filtration, 5) chlorination followed by dechlorination, 6) addition of clay based polymer, 7) treatment with peroxide and ultra-violet light, 8) bulk addition of GAC and zeolite powder, 9) treatment with bacteria. This article presents a summary of the test results and of the problems associated with the evaluation of technologies for the treatment of toxicity.

Nov 1, 2002

By John A. Allan

The subject chosen for this paper is not a new one, but the subject matter is so extensive that something new can always be said .about it. We are just beginning to realize how little is actually known about the character of Alberta coal, except for a few general facts. The object of this paper is not to explain that our previous information, in whole or in part, on the coal resources of Alberta, has been incorrect, but rather to present some new facts obtained as a result of recent study in the field and in the laboratory. As field investigation continues the problem of determining the character of a coal seam for any great distance laterally becomes more and more complex. Our present knowledge of Alberta coal deposits should not be discussed before due reference is made to those great pioneers who blazed the trails for later geologists, by recording their observations on the general geology of Alberta. Geologists, to-day, particularly those of us who are striving, year after year, to unravel the mysteries of stratigraphy, palaeontology, and structure, in so far as these are related to the coal resources of Alberta, fully realize our indebtedness to those three trail-makers, Dawson, McConnell, and Tyrrell. Had these geologists not recorded their observations correctly, nor interpreted the broad geological facts contained in Nature's book, with still uncut pages, how much slower would have been the progress of our coal knowledge in the succeeding years. It is true that many of the interpretations given to observations by these pioneers have had to be changed as a result of closer studies, but we must also expect that the geological interpretation from present day observations will be changed by future workers, as Nature's book is read and re-read.

Jan 1, 1925

By E. Peters

Roasting processes are divided into several elementary mechanisms, any of which could be significant or pre-dominant in a particular roast. The elementary processes considered in-elude beat transfer, gas-solid inter-actions with accompanying mass transfer between the bed and furnace atmosphere, vapor phase transport processes in solid-solid interactions, and solid phase diffusion processes. Examples are chosen of processes in which one of these mechanisms pre-dominates and some recently obtained data is presented to support the existence and significance of these mechanisms. Proposals are also made for future research in these areas, and for utilizing the information in the improvement of roaster capacities’ OASTING of ores as a preparative treatment for smelting or leaching has been practiced for so long that its origin has been lost in antiquity, but little has been under-stood of its basic nature until fair-ly recent times. The nominal chemistry of roasting processes is now understood; that is, the initial chemical com-pounds present in the ores or con-

Jan 1, 1961

By T. A. Wheat

"The presently increasing world-wide interest in advanced ceramic materials is generally focussed on their exploitation in both structural and functional applications. With the opportunity to engineer microstructures and thereby closely control and tailor the final properties, there are many new applications being made for these materials in both areas.The scope and some of the applications for functional ceramics are reviewed and examples of the present Canadian activity in this field are discussed.BackgroundThere has been progressively increasing international interest in the development and exploitation of ceramic materials in the last five years. The stimulus for this interest arises from several quarters, each of which are independent of the other.• There is a growing awareness of the strategic nature and vulnerability of supply of the raw materials used to produce high performance metal alloys.• The metal alloys are reaching the upper temperature limit for their performance as structural components in engines.• The dramatic increase in oil prices during the late 1970s focussed attention on the need for reduced consumption in many sectors, i.e., there is a need for more efficient engines that operate at higher temperatures - above those tolerated by the present superalloys.• A number of ceramics, especially the structural materials such as SiC, A120 3, AI20rSi02, Si3N4 and the Sialons are produced using non-strategic raw materials and they can exhibit startling performance-auto turbo-rotors are in production mad e of Si3N4 that operate up to 190000 rpm at 600°C, 150000 rpm at 900°C.• Ceramic s are generally of lower density - significant in the weight-reduction of automobiles such as the replacement of a 20-kg five-segment steel leaf spring with a single segment carbon-fibre reinforced unit of 3 kg. • Ceramics also offer major ad vantages in generating, monitoring or controlling the electromagnetic spectrum whether in bulk or thin-film devices that exploit optical, magnetic, pyroelectric, piezoelectric, electronic and I or ionic conductivity characteristics.The opportunity to combine several of these char acteristics in a single material by composition, processing and microstructural design has resulted in an advanced ceramics industry that had world-wide sales in 1980of $4.2 billion (U.S.)(I) and is predicted to grow to sales in the range $7 to $10 billion by 1990 and $16 to $24 billion by the year 2000(2). However, at present, advanced ceramics account for less than 20010 of the total ceramic market."

Jan 1, 1987

By Graeme G. Strathdee

"IntroductionThis paper presents an overview of the industry status, describes current potash industry practices at three mills, and summarizes developments that have taken place since the previous review by Banks (1985).The commodity potash is produced in both New Brunswick and Saskatchewan from the evaporite ore sylvinite. This ore is a mixture of co-crystallized halite, NaCl, and sylvite, KCl, and a minor assortment of silica, carbonate, sulphate, and clay minerals. Carnallite, KMgCl3.6H20, is also dispersed throughout the bedded deposits and can affect the recovery of sylvite for fertilizer and industrial uses.Canada continues to be a principal source of supply of agricultural and industrial potash products. Figure 1 shows the sector performance between 1989 and 1997 in the context of the world supply and demand situation as reported by Prud'homme (1997) of Natural Resources Canada.Potash industry output is traditionally measured as the quantity of potassium nutrient and reported as tonnes ofK20. Mineralogically, the principal form of potash produced in Canada is sylvite, KCl, and 1 nutrient tonne K20 corresponds to approximately 1.64 tonnes of sylvite of agricultural grade, about 95% KCI. In 1997, the Canadian industry milling capacity was 13.4 million metric tons (Mt) ofK20 (22 Mt KCl) while the actual production was 9.0 Mt K20 (14.8 Mt KCl). Worldwide milling capacity in 1997 was 35.9 Mt K20 (58.8 Mt KCl) and global consumption was 25.3 Mt K20 (41.6 Mt KCl). Canadian producers can deliver about 35% of the global demand for potash commodities"

Jan 1, 2000

By C. Van Den Heuvel, C. B. Van Buuren

BIOX® has been successfully demonstrated over the past 2 decades for the recovery of gold from refractory sulphide concentrates. To date 12 successful BIOX® plants have been installed in 8 countries spanning 4 continents with the 13th installation currently nearing completion in the Philippines. In 2010 BIOMIN introduced the ASTER™ process for improved water balances in commercial BIOX® applications by supporting tightening environmental legislation on water usage and availability in both arid and tropical regions. Previously, a common challenge for BIOX® plants was the inability to recycle thiocyanate containing water due to the low tolerance of the organisms. ASTER™, a biological thiocyanate and cyanide destruction process, renders a non-toxic solution for re-use in BIOX®. Two commercial ASTER™ plants are in operation with the 3rd ASTER™ plant under construction in the Philippines. A 3rd BIOMIN technology, specifically developed for double refractory ores is available for implementation. The HiTeCC process has shown considerable success on ores where competition from disseminated carbon has rendered ineffective gold recoveries. Through HiTeCC, gold is desorbed from the carbonaceous matter by manipulating the ionic strength and temperature of conventionally treated CIL product. One Australian commercial plant utilises HiTeCC while a 2nd installation is set for commissioning 4th Quarter 2014. BIOMIN’s premier solutions for refractory gold processing are described herein.

Jan 1, 2014

By B. Yamamoto, D. Post, J. De Leon, A. Meike

"This paper describes the theory, design, building, and testing of the passive magnetic bearing stabilizing system which is the core of the passive magnetic bearing system. The stabilizing system is made up of two large magnetic disks opposing themselves with a stabilizing disk in the center which allows the system to self-locate in a null position without the need for external power sources or sensors. When outside forces act upon the stabilizer, the magnetic fields interact with the stabilizing plate to return the system to its null position. Collaboration between two industry leaders has allowed an actual prototype to be built and tested providing real data to prove out the theory.INTRODUCTIONMagnetic bearing/stabilizer systems have many advantages over conventional mechanical bearing systems. These include near-zero drag losses and no need for lubrication since the rotating elements make no mechanical contact with the stationary elements of the bearing system. However all magnetic bearing systems must contend with a constraint known as Earnshaw’s Theorem in the early 1800’s, this theorem asserts the impossibility of constructing a stable, non-contacting, electrostatic or magnetostatic levitation system using only fixed charges or fixed magnetic poles, such as those produced by permanent magnets. Because of the constraint imposed by Earnshaw’s Theorem virtually all present-day commercial magnetic bearing systems are of the “active” type. That is, they employ electromagnets that are powered by amplifiers the inputs to which come from sensors embedded in the bearing system. These sensors are a part of a feedback loop that operates to keep the levitated rotating parts of the bearing stable and centered. The resulting complexity means that active magnetic bearings are expensive, require periodic maintenance, and continuously consume electrical power to energize their amplifiers and their electromagnets.Passive magnetic bearings are, of course, also subject to the constraints imposed by Earnshaw’s Theorem but they solve this problem in a straightforward and simple way, with only “passive” elements that take advantage of a loophole implicit in the derivation of Earnshaw’s Theorem. This loophole is that Earnshaw’s Theorem as derived applies only to static systems, i.e. an assembly of stationary permanent magnets arranged so as to levitate an object containing other permanent magnets. The theorem can be overcome if dynamic effects are taken into account. In active magnetic bearings the “dynamic effects” involve the afore-mentioned sensors, amplifiers, and electromagnets."

Jan 1, 2012

By A. Khodadadi, M. Abdolahi, P. Taimory

Cyanide is used by the mining and chemical industries in tremendous quantities without attention being given to its hazardous properties. The use of cyanide compounds in mining is one of the most important environmental issues for the mining industry due to the acutely toxic properties of many cyanide compounds to humans and aquatic life. Cyanide tends to react readily with most other chemical elements, producing a wide variety of toxic, cyanide-related compounds and because cyanide is carbon based an organic compound it reacts readily with other carbon-based matter, including living organisms. This research is aimed at investigating a feasible and economical technique for the removal of cyanide from tailing wastewater of Muteh gold mine. In this research, removal from Muteh factory's waste water, was achieved at Tarbiat Modares University's mineral processing laboratory through the oxidation of cyanide by calcium hypochlorite. Cyanide oxidizes and changes to cyanide (CNO-) which is 1000 times less environmentally hazards than cyanide. Cyanide titration was accomplished using Rhodanine solution and silver Nitrate. Cyanide concentration in the wastewater, was 270 mg/L. Cyanide removal was achieved at an optimum pH of 12.3. However, at higher temperatures, cyanide removal was complete at this pH level. Optimum Dosage for complete removal of cyanide using calcium hypochlorite was 1.43g/L.

Jan 1, 2005

By R. A. L. Drew, J. P. Immarigeon, F. Jalilian, M. Jahazi

In the present work TLP bonding of Inconel 617 is investigated. The influence of the main processing parameters i.e. time and thickness of the interlayer were studied with optical and scanning electron microscopy. Boron containing interlayers with two different thicknesses were used and the influence of various holding times from 5 min to 24 hours on the microstructure of the bond region was investigated. The results indicated that, for the testing temperature of 1065°C and holding times above 2 hours with an interlayer of 25.4 microns thick no liquid phase was observed. The same phenomenon occurred only after 6 hours for a 76.2 microns thick interlayer. Precipitate growth started at grain boundaries and continued inside the grains. The composition, size and morphology of the precipitates were studied using electron microprobe analysis. No noticeable changes were observed in the grain size of the base metal with increasing holding times.

Jan 1, 2004

By M. Normandin

The performance of various polymers and other macromolecules used to flocculate red mud particulate materials in the Bayer process can be evaluated on the basis of their efficiency to achieve adequate settling velocity and turbidity level, The Jar Test is widely used in the mineral industry to determine the efficiency of solid-liquid separation processes, particularly for gravity settler of the Bayer process. However, a high level of variability is found in the data obtained by this methodology, In this study, different parameters of the cylinder test procedure are evaluated to determine their role in the overall variability of the method, As demonstrated by laboratory testing, the overall variability can be considerably reduced by good laboratory practices.

Jan 1, 2005

By Alan E. Renshaw

"This paper is a practical overview of ways to reduce cost in the design and operation of an Arctic mine. The economically important issues of the Arctic mine that will be addressed include: permafrost and the active zone in general terms; road building in and over permafrost; Arctic geotechnical mine design considerations; pit dewatering techniques in sub-zero temperatures; and blasting frozen materials with techniques to obtain optimal results. A final section on a few special topics conclude this paper.Although this paper primarily refers to near surface conditions more closely associated to an Arctic surface mine, many of the ideas and techniques contained in the paper also apply to the surface construction of an Arctic underground mine."

Jan 1, 1996

By Z. Gostynski

The paper is a historical cross-section through a 28-year period of operation of the direct-to-blister Flash Smelting Furnace in the KGHM Glogów Copper Plant. It presents the origin of the furnace as well as the path of numerous changes and modifications both in technology and process introduced in the furnace in response to the production and cost-reduction challenges. The authors provide justification of the statement that continuous improvement of the "Polish" Flash Smelting Furnace has ranked it among the most modem smelting units in the world.

Jan 1, 2007

By C. Barlow

The White Mesa Mill (WMM) began operating in 1980 as a regional processing mill owned by Energy Fuels Nuclear, Inc. Original mill design was for 656,000 Mtpa of U ore producing 1,250 tpa of U3O8 concentrate. Sustained market downturns delayed facility upgrades during most of the 1980s and 1990s. The new owners of WMM, Denison Mines, elected to advance the regional mill concept in 2007 with the modernization of these facilities. This paper details decisions taken and lessons learned in plant redesign, choice of leading-edge instrumentation, motor controls and process automation, training and some example benefits from process control stabilization.

Aug 1, 2010

By R. E. Bou Serhal

Many miners are exposed to dangerously high levels of noise on a daily basis. Over the past 15 years, a continually increasing number of occupational hearing loss has been reported from the mining community in the United States, of which, more than 95% is attributed to prolonged noise exposure. Although the noise exposure levels may differ between coal miners and metal and non-metal miners, in the absence of noise control at the source, the solution is the same: use of personal hearing protection devices (HPD). While protecting the miners? hearing it is also essential to no longer hinder their ability to communicate. With access to an advanced HPD that is customized to the miners? ears we are able to combine these two requirements. Using an intra-aural instantly custom molded HPD miners are protected from high levels of noise. The HPD is equipped with wireless capabilities, and contains both a speaker and an In-Ear Microphone (IEM). Therefore, the miners? speech may be captured from inside the ear and transmitted to the remote listener. This IEM signal is relatively noise-free since it is isolated from the background noise. The IEM speech signal, however, is ?boomy? and is missing some high frequency content, making fricative consonants hard to understand. Nonetheless, the IEM speech signal is correlated with the natural speech signal and may be manipulated through statistical techniques to more closely resemble natural speech. By improving the intelligibility and quality of the IEM signal, numerous applications may be enabled. One use of the enhanced IEM signal will be for radio communication. Using wireless radio communication in a noisy mining environment is sometimes the only practical and affordable solution to allow communication between miners equipped with personal hearing protection devices. Traditionally, one of the weaknesses of such wireless radio communication lies in the lack of designating receivers: whether they are the intended receiver or not, all those carrying a radio receiver are subjected to the broadcasted signal. The current work will detail a new concept of a "radio-acoustical virtual environment" where the radio signal will only be received by miners within a given spatial range, such range depending on the user?s vocal effort as well as the ambient and perceived background noise levels.

Aug 1, 2013