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By Francis Dakubo, Courtney Young, Avimanyu Das

"Hydrometallurgy of copper ores typically involve acid leaching followed by solvent extraction and electrowinning (SX/EW). EW is the final purification stage in which a voltage is applied across two electrodes causing the copper ions to reduce and deposit on the cathode. Applied voltages are near 2 volts with current densities around 300 amps/m2. In this study, research was undertaken to decrease the energy consumed in the EW process. To do this, various cell designs were constructed and tested in which a membrane was used to separate the cathode and anode compartments with concentrated solution from SX serving as catholyte and raffinate from SX serving as anolyte. Therefore, copper in the concentrated solution would be deposited on the cathode while ferrous in the raffinate would be oxidized to ferric at the anode. Because it is assumed that ferric acid leaching is used, resulting ferric would be recycled to the leaching process. A positive side effect of the envisioned process would be the elimination of oxygen evolution at the anode and thus the prevention of acid-misting. After a cell design was selected, it was used to test a number of variables: flowrate, concentration, temperature, ion-exchange membrane, and applied voltage. Following experiments in which variable ranges were determined, statistical modeling was conducted using STATEASE software. Optimal results indicate the voltage can be decreased to 1.5-1.7 volts with current densities of 300-400 amps/m2. Significant reduction in the energy consumption was accomplished by reducing the applied voltage. Furthermore, current efficiencies and copper production rates was increased by application of the membrane.INTRODUCTIONLeaching of copper ores is achieved using mostly sulfuric acid. The copper pregnant solution is contacted with an organic solvent or resin adsorbent which picks up copper ions as in Equation 1:"

Jan 1, 2016

By J. Asfahani

"The inverse slope method (ISM) was applied to reinterpret vertical electrical soundings (VES) data from pits at the Al-Sharquieh phosphate mine, in order to demonstrate applicability and suitability of the ISM for interpreting VES data from sedimentary phosphatic environments. The ISM overcomes limitations of the curve matching method and the complexity of lithological sections. The ISM geo-electrical interpretation results correlated well with lithologies of the pits. This method characterized resistivity and thickness of the phosphatic layer, and identified favourable phosphate-prospecting areas using the newly developed thickness/depth parameter. The ISM is recommended for interpreting VES measurements in similar sedimentary phosphatic regions.RÉSUMÉ La méthode d’inversion de la pente (ISM) a été utilisée pour réinterpréter les données de sondages électriques verticaux (VES) effectués dans des puits de la mine de phosphate Al-Sharquieh, afin de démontrer l’applicabilité et la pertinence de cette méthode pour interpréter les données VES dans des environnements de sédimentation de phosphates. Cette méthode (ISM) surmonte les limitations de la méthode de comparaison de courbes et la complexité des sections lithologiques. Les résultats de l’interprétation géoélectrique ISM correspondaient bien aux lithologies des puits. Elle a permis de caractériser la résistivité et l’épaisseur de la couche phosphatique et d’identifier les secteurs favorables à la prospection pour le phosphate en utilisant le paramètre nouvellement développé épaisseur/profondeur. ISM est recommandée pour l’interprétation des mesures VES dans des régions semblables où se trouve du phosphate sédimentaire."

Jan 1, 2016

By Ismael Gottreux Vollet, Carlos A. Muñoz Lira, Alejandro Ferrada Vergara

Currently, underground mining of deeper massive deposits with lower grades, harder rock conditions in high strength environments, entails difficulties in caving, fragmentation and seismicity of the ore body. So far, the use of Pre-Conditioning (PC) with Hydraulic Fracturing (HF) has shown positive results in terms of seismic response and caving ability, while preconditioning combined with explosives aims to weaken the rock mass, causing an additional effect on fragmentation.

Jan 1, 2016

By Binbin Luo, Northeastern University, Chuanyao Sun, Jie Liu, Yimin Zhu, Yanjun Li

"A series of new type collectors a-bromo-saturated fatty acids, CH3(CH2)5CHBrCOOH (a-BHA), CH3(CH2)7CHBrCOOH (a-BDA), CH3(CH2)9CHBrCOOH (a-BLA), CH3(CH2)11CHBrCOOH (a-BMA) were synthesized from saturated fatty acids and bromine by solvent-free method (Hell-Volhard-Zelinski reaction) in laboratory. The micro-flotation tests of quartz mineral were conducted at a relatively low temperature of 15 °C. The adsorption mechanism of such collectors on quartz mineral surface were established by zeta potential measurements, in conjunction with the results of quartz micro-flotation tests. The flotation results showed that the collecting ability is in the order of a-BMA > a-BLA > a-BDA > a-BHA for the flotation of quartz mineral, which also demonstrating that the a-bromo-saturated fatty acids (a-BFAs) are new selective collectors for reverse flotation to remove quartz mineral from iron ores at a relatively low temperature.INTRODUCTIONThe requirement of higher pulp temperature to maintain the activity of fatty acid anionic collectors which have been widely applied in technological process of iron ores reverse flotation lead to a great deal of energy consumption.The purpose of this paper is to synthesize a new modified collector with carbon chains from eight to fourteen atoms, with strong electronegativity bromine atom introduced into a-carbon position to improve the activity and solubility of the reagent so that it can be adopted at a comparatively low pulp temperature. The collecting performances of these new collectors on quartz surface were studied, and the structure - properties were discussed in light of zeta potential measurements and quantum chemistry calculations."

Jan 1, 2016

By Ruilin Yang

This paper provides a theoretical analysis of shockwaves in an air-deck induced by detonation of an explosive charge and shows that the initial shock pressure in the air-deck at the interface with the explosive charge is only about 1% of the detonation pressure. A rarefaction wave with the low pressure travels back into the explosion detonation products greatly reducing the post-CJ detonation pressure. Additionally, AUTODYN modelling shows that the pressure attenuates further during shockwave propagation along the air-deck. Although the pressure increases at the bottom of the blasthole due to shock reflection, the overall pressure in an air-deck does not increase and is still around 1% of the detonation pressure which is too low to break most rock.

Jan 1, 2016

By Johannes Jäger

"A composite shell lining typically consists of an outer permanent sprayed concrete shell, a water proofing layer and an inner sprayed or cast concrete shell. Composite shell linings become more and more popular and have been built recently on large scale infrastructure projects. Surprisingly there is very little published literature on the actual structural design of composite linings. As a consequence there is a lack of common understanding on how to design a composite lining structure. Composite action of the outer shell (primary lining) initially carrying short term ground loads and the “unloaded” inner shell (secondary lining) require nonlinear concrete modelling to be able to assess the bearing capacity of the composite lining structure adequately. The composite action of the waterproofing membrane and the inner and outer shells can be considered either by simplified closed form solutions or by numerical models. Strength and stiffness parameters of membrane and concrete govern interaction of inner and outer shell. This paper should contribute to understanding composite lining behaviour with focus on the bearing capacity at limit state by taking into account the actual loading history. Possible ways and concepts on how to deal with these topics are presented, however a broader discussion on limit states of the composite lining materials – also in the long term will be required to come to an agreement on composite lining design methodology. INTRODUCTION Composite Lining Technology Traditionally the construction of shotcrete lined tunnels incorporates primary and secondary linings, separated by a sheet or a sprayable waterproofing membrane. The primary lining shotcrete is considered to be structurally temporary and the secondary lining to be permanent, leading to designs which ignore the bearing capacity of the primary lining in permanent condition. There was general perception that the shotcrete lining installed immediately at the tunnel face, experiencing strains up to 1% and even cracking in the early age, combined with mesh reinforcement additional support measures like lattice girder, spiles and bolts cannot be considered as a permanent structure. But also former shotcrete mixes showed significant weakness with respect to durability suggesting a more temporary nature of primary lining shotcrete. On the other hand it was clear that primary lining shotcrete does not disappear, it may lose probably a certain percentage of its bearing capacity, but discounting any contribution from the primary lining at all was considered inherently conservative. There were different strategies to account for the risk of reduced durability and bearing capacity of the primary lining, either by selecting moderate ground loads for the secondary lining design, by assuming that some residual load will be carried by the primary lining. This approach is very much based on experience. Another more rational possibility is to assume that the primary lining degrades into a rocklike material, which is weaker than the primary lining shotcrete but still imparts some strength to the ground around the secondary lining, but does not need to comply with any concrete design codes any more."

Jan 1, 2016

By David Stephenson, Hugo Granados, Steven Klohn

"HudBay’s Constancia project is a copper molybdenum concentrator located in southern Peru. In 2010 Ausenco was contracted to perform a feasibility study optimization review which resulted in an improved design with significantly increased throughput capacity at a minimal increase in capital cost. Construction began in 2012 with commercial operation commencing in May 2015. This paper outlines the process plant design as well as describing the plant’s major equipment selections, start-up and early operations experiences.IntroductionHudBay Mineral’s Constancia project is located at 4200 meters above sea level (masl) in southern Peru, approximately 630 km south-east of Lima, Peru. The property can be accessed by road from Cusco, Peru, (approximately 110 km to the north), or from Arequipa, Peru (approximately 215 km to the south). Matarani, accessed via Arequipa, is the closest port.Constancia is located within the Yauri-Andahuaylas metallogenic belt. The region contains several large copper-gold-molybdenum porphyry deposits such as Antapaccay (by Glencore) and Los Chancas (by Grupo Mexico), and copper skarn deposits such as Tintaya (by Glencore) and Las Bambas (by MMG). Constancia’s ore reserves contain copper and molybdenum with trace amounts of gold and silver.Ore is mined by an open-pit operation. The process plant recovers copper and molybdenum concentrates, storing tailings in a conventional tailings management facility. Infrastructure at the site includes a grid power supply (via a 70 km overhead transmission line from Tintaya), water supply, workshops and an accommodation camp. Mine life is 22 years.Site construction works began in 2012 with first copper concentrate produced in late 2014. The project was executed for approximately 1.75B$USD.Ausenco’s design approach focussed on developing a capital efficient copper molybdenum concentrator. This paper outlines key features incorporated in the concentrator design, plant layout and equipment selection, as well as start-up experiences and early operational results."

Jan 1, 2016

By Sanna Mustonen, Seppo Mellanen, Mellanen, Pekka Kantia

In Finland Posiva Oy (Company) is responsible for implementing the final disposal programme for spent nuclear fuel of its owners. Company is preparing for the geological disposal in Olkiluoto crystalline bedrock. Excavation will be executed using drill and blast method. Method unavoidably causes variable excavation damaged zone (EDZ) on tunnel surfaces. The EDZ constitutes a risk for long term safety and therefore good control methodology of the blasting technique is required. The thicker the EDZ, the greater is the likelihood for detrimental transport pathways for ground water to transport radio nuclides, should those be present.

Jan 1, 2016

By Kari Niiranen, Andreas Boehm

LKAB (Luossavaara-Kiirunavaara AB) is operating underground iron ore mine, with three beneficiation and pelletizing plants in Kiruna, Northern Sweden. The wet low intensity magnetic separation (WLIMS) is regarded as the crucial part of silicate mineral separation from the ore. The Kiirunavaara iron ore deposit shows a rather low content of silica (ca. 2.3 to 3.3 % SiO2) but the silica grade is expected to increase in the deeper parts of the deposit. This can be problematic in the case of DR pellet quality with an average silica grade under 0.75 % SiO2. A laboratory scale methodology was developed for the systematic characterization of the ore for mineral processing with the focus on silicates at the Institute of Mineral Processing, University of Leoben. This methodology is combining mineralogical, geochemical and process mineralogical characteristics. Automated mineralogy (QEMSCAN) was used to study the modal mineralogy, the distribution of silicate minerals in different particle size classes after comminution, the deportment of silicon (Si) between various silicates and degree of liberation and intergrowth of magnetite and silicates. Based on the mineralogical investigations, actinolite, phlogopite and even quartz and albite are the predominating SiO2 bearing minerals in the ore. The important result of the investigations was the discovery of two separate subtypes within the high silica ore type B2 based on their mineralogy and mineral processing characteristics. The crucial part of the investigations of intergrowths and liberation of magnetite results was the magnetic separation tests carried out with the Davis magnetic tube. The binary intergrowths of magnetite and the silicate minerals (mostly actinolite) are the most common type of mineral association discovered. The significant characteristics in the intergrowths of magnetite and actinolite are the fine-grained magnetite inclusions in actinolite which may end up increasing the SiO2 grade in the magnetite concentrate despite magnetic separation.

Jan 1, 2016

By Joshua A. Bennett

"Lawsuits where owners allege their property has been damaged by nearby blasting routinely costblasting companies, explosives engineers, and others in the field both time and money. When ownersfeel the vibration of a blast, they immediately begin to look for damage and usually find cracking thatwas, in fact, present prior to the blasting occurring. When those owners begin to talk to their neighbors and legal counsel, blasting entities suddenly have multiple lawsuits being filed as a result of the same blast."

Jan 1, 2016

By Frederik H. Kriel, John Ralston, Craig Priest

"Stream-based microfluidic solvent extraction offers a novel alternative to bulk-scale mixer-settler operations. However present maximum throughputs are restrictive and there are engineering challenges that need to be overcome before the technology is robust. This is especially the case for mineral processing, where circuits must be able to handle variable feed streams with long retention times and where maintenance should be minimized. This paper highlights research directed at investigating and evaluating these challenges for actual mineral leach solutions of metal ions. Molecular and particulate channel fouling is discussed. Most extraction systems studied to date show no effects that would preclude use of the technology. For rare earth elements (REE) with fast extraction rates, scale-up of volumetric throughput to 100 L/h using suitable arrays of channels, microfluidic chips and modules is shown to be achievable using a small contactor (approx. 2 m3) platform. This requires only 2–3 % of the typical aqueous phase inventory and residence time used in an equivalent mixer-settler. For a circuit with 100 contactors, the overall residence time would be less than 1 h, using an aqueous inventory of 40 L.INTRODUCTIONHydrometallurgy is of pivotal importance in many mineral processing circuits around the world, with liquid-liquid solvent extraction (SX) a key step in the separation of many base metals (e.g. Cu and Ni), radioisotopes, precious metals, and the ‘technology’ metals, such as rare earth elements (REEs) (Ritcey & Ashbrook, 1979). The standard equipment for SX in mineral processing is the mixer-settler, in which liquid dispersions are created, by agitation, to increase the surface-to-bulk ratio and, thus increase the mass transfer rate between the liquid phases. In stream-based microfluidic SX (microSX), these high surface-to-volume ratios are achieved by contacting microscopic streams (Ciceri, Perera, & Stevens, 2014), rather than forming small droplets, so that phase disengagement can be accelerated (essentially instantaneous via branching of the two streams of liquid at a channel junction). MicroSX is profoundly different from bulk mixer-settler SX operations and offers exciting opportunities for processing hydrometallurgy solutions (Kriel, Holzner, Grant, Ash, Woollam, Ralston, & Priest, 2015; Priest, Zhou, Klink, Sedev, & Ralston, 2012). Nonetheless, the advantages of using microfluidic environments are presently balanced by very significant challenges relating to throughput, process control, coupling of stages, flow stability, and fouling. If these challenges can be met using smart chip designs, process control and clever engineering, high-value/low-volume SX processes stand to benefit greatly."

Jan 1, 2016

By K. C. Corin, Z. G. Song, J. G. Wiese

In the present investigation flotation was used as a diagnostic to understand the effects of changes to the media during the grinding stage. The observations from flotation for different media are discussed in terms of particle size distribution, water recovery, solid recovery and valuable mineral recovery. The chemical parameters; pH, redox potential (Eh) and dissolved oxygen (DO) levels were measured. A Base Metal Sulphide (BMS) ore was ground under media of different shapes and compositions to determine the effect of different rod/ball material on the flotation performance of the ore. For a given grind (D80 = 75 µm), media shape had no effect on flotation performance of a BMS ore. Different grinding media had significant effect on slurry chemical properties and flotation performance. Mild steel rods (RMMS) produced the highest solids recovery, nickel and pyrrhotite (Po) recovery, with the highest ethylenediaminetetraacetic acid (EDTA) extractable iron and the lowest DO level. Chrome steel balls and stainless steel rods produced the lowest metal recovery, EDTA extractable iron and the highest DO level. A complementary study was conducted to investigate the effect of using different grinding media compositions, viz, ceramic, forged steel, 15% chrome steel, stainless steel and a mixture of stainless steel and 15% chrome steel (50:50) balls were investigated using a Platinum Group Mineral (PGM), UG2 ore. Grinding products of five different media produced the same solids and water recovery, but the grades and recoveries of Platinum Group Elements (PGE) and chromite were different. Grinding products of ceramic media showed the best flotation performance, with the highest PGE recovery and the lowest Cr2O3 recovery. While grinding products of stainless steel balls (SS) produced the lowest PGE recovery and highest Cr2O3 grade and recovery in the concentrates.

Jan 1, 2016

By Cancelli Paolo, Bragonzi Gianluca, Pelizza Sebastiano

"In May 2015 the New Monte Bianco aerial cableway, operating on the Italian side, have been completed. It connects the lower station in Pontal d’Entreves (1300 metres above sea level (m a.s.l.)) with the intermediate station at Pavillon de Mont Frety (2160 m a.s.l.) and with the top station at Helbronner Peak (3460 m a.s.l.). A new underground link between Helbronner Peak and New Torino Refuge has also been built. The link is divided into two different sections: the first one, a 70 meters deep vertical pit created using the “Raise Boring”, descends underground from Helbronner Peak station; the second section, a 160 meters long sub horizontal tunnel, emerges at Torino Refuge. After a first introduction focused on the general layout of the project, the paper will present the geomechanical survey aimed to evaluate the effect of permafrost on the stability of intensely fractured granitic mass. Finally, it will describe the relevant issues related to the highest construction yard in Europe (3400 m a.s.l.): difficult conditions such as extremely cold and windy weather and restricted spaces. INTRODUCTION The new cable way connects the lower station in Pontal d’Entreves (1300 m a.s.l.), close to Courmayeur, with the top station at Helbronner Peak (3462 m a.s.l.) and its territory, as well as links with France and, through the French territory, with the town of Chamonix (1000 m a.s.l.). The overall layout is divided into two sections (as shown in Figure 1): the first section, “Pontal d’Entreves – Mont Frety”, has a length of 1700m, elevation differential of 886m, a capacity of 800 persons/hour and cable cars for 80 passengers; the second one, “Mont Frety – Punta Helbronner”, has a length of 2630m, elevation differential of 1276m, a capacity of 600 persons/hour, and cable cars for 75 passengers. The new system is designed for fully rotating cable cars moving at a constant rate of 9.0 m/s. The track requires constructing special cables supports, three for the first section and two for the second one."

Jan 1, 2016

By McGill Metals Processing Centre, S. Chang, L. Calzado, X. K. Cao, C. H. Hsin, M. Isac

"Due to the increasingly stringent cleanliness requirements for final steel products, there has been a growing interest in the possible use of micro-bubbles for the removal of inclusions with diameters smaller than ~50µm, present within the steel passing through a steelmaking tundish. However, several technological barriers have prevented the adoption of this technique in industry. These are related to a) the generation of micro-bubbles in liquid steel, b) the measurement of bubble size distributions, and c) the optimization of bubble injection conditions to create micro-bubbles. In the present study, a novel Aqueous Particle Sensor (APS) system was developed for the in-situ, on-line, detection of micro-bubbles in water, generated by a newly designed full-scale ladle shroud, located at McGill Metal Processing Centre (MMPC). Measurement results from the sensor were validated against bubble size data collected through a high speed camera and post-processed through the commercial software, Image J.Control variables and orthogonal experiments were designed to assess the dependence of average micro-bubble sizes and bubble size distributions on key experimental parameters. Those chosen were the air inlet flowrate, the distance of the gas injection port from the slide gate, and the number of injection ports used. The investigation demonstrated that the APS system can be successfully adapted to detect micro-bubbles up to ~800 micron diameters. Using this novel sensor, it was shown that multi-port injection using low air inlet flowrates, closer to the slide gate, were useful in forming small micro-bubbles within the flow through the ladle shroud. The results from the APS system were compared and validated against data resulting from an optical technique. INTRODUCTIONModern industry expects increasingly stringent cleanliness requirements for final cast products. Therefore, the numbers and sizes of inclusions need to be strictly controlled in steelmaking operations. Thus, the cleanliness of steel products depends on the amount, morphology and size distributions of nonmetallic inclusions in steel (Zhang L. & Thomas B., 2003). Since large, deep, tundishes provide longer nominal residence times for liquid steel passing through it to the exit SEN’s, this can provide the ideal place to separate inclusions, and bubbles can assist by removing help attach inclusions and float them to the top surface."

Jan 1, 2016

By T. W. Camm

"Search Amazon.com using the keyword “leadership,” and you are rewarded with a list of over 144,000 titles. There is no shortage of books and articles, many of them well written, with excellent ideas. So why is there still a constant cry for effective leadership in organizations? Often, the person in charge has personal blinders that prevent them from seeing or understanding how to implement the newest leadership idea or method. Either deliberately or subliminally, there is a disconnect from learning about leadership, and actually modelling and implementing what has been learned. Some current research in leadership theory can provide insight and tools to address this issue. INTRODUCTION Let’s start with a discussion of terms. Pseudo is defined by Webster (2015) as “Being apparently rather actually as stated.” Synonyms include affected, assumed, contrived, fake, false, phony, pretended, and artificial. Antonyms for pseudo provide additional clarity, especially when we consider terms normally associated with effective leadership: genuine, natural, unaffected, unforced. A similar type from my world of academia is a pseudointellectual, “A person exhibiting intellectual pretentions that have no basis in sound scholarship” (Dictionary.com, 2015). This is a person pretending to have an interest in intellectual activities for status; a fraudulent intellectuality. The thought of applying the term pseudo to leadership first occurred to me while reading Power and Innocence by Rollo May (1972). In discussing the dynamics of power, and how the innocent are often victims of the exercise of power, especially the more aggressive and destructive types of power, he saw two types of innocence. The first he called authentic innocence, which he described as a childlike clarity that carried into adulthood. The second type he called pseudoinnocence, a type of naïveté that makes a virtue of powerlessness, weakness, and helplessness; being more childish than childlike (p. 48-50). Just as there is the potential for pseudoinnocence and pseudointellectuals, it is also possible to experience pseudo leadership. (I hope the gentle reader is not troubled by my decision to use pseudo leadership as two separate words, in contrast to the use of compound words for pseudoinnocence and pseudointellectual cited above. Since there is no official definition of pseudo leadership, I have exercised my author’s prerogative to treat it as two words, both because I think in this particular application this makes the most sense, and also I think it is easier to read). As we will see, there are numerous theories applied to leadership. What is so troubling to many of us in organizations, there are a myriad of “leaders” in companies espousing pet theories, but very few instances where the actions of these individuals match their words. This is a particularly important problem when we look at the effect this has on the day to day operations of a mine, and where effective leadership (or its absence) can have a profound impact on both productivity and safety."

Jan 1, 2016

By C. B. Espag de Klerk, J. de Goede, M. Le Roux, Q. P. Campbell

"Excessive amounts of moisture in product coal can influence the efficiency of downstream utilization processes due to a decreased calorific value and handling problems. Stockpiles can be used to decrease the moisture content of coal by means of gravity drainage and evaporation. This paper is focused on the evaporation of moisture from a coal stockpile surface with the aim of investigating the effect of particle size on the rate of evaporation as well as the depth to which evaporation extends.It was observed that moisture initially evaporates at a higher rate from a stockpile consisting of fine particles (-6.7 mm) than from coarser particles (-13.2 mm +6.7 mm). This high rate of evaporation is restricted to the outer shell of the fine coal stockpile. However, for coarse coal, the porous nature increases the depth at which evaporation occurs. Evaporation of moisture was observed up to the fourth day of each experimental run, after which steady state was obtained. It was shown the water can evaporate from the surface into the body of the stockpile, depending on the coal particle size and void spacing. An experimental reclaim depth of 0.4 m was achieved after 4 days. IntroductionCoal stockpiles serve as surge capacity for downstream utilization processes and can also be used for moisture reduction by means of gravity drainage and evaporation. Excessive amounts of moisture in coal can cause handling problems and, most importantly, will decrease the calorific value, leading to inefficient combustion.Research has shown that evaporation by means of wind and solar action is considerably more effective than gravity drainage(Williams, D.J. 2006), but the effect is limited to a restricted depth from the exterior of the stockpile (Boyapati, E. and Oates, A. 1994; CSEM-UAE, 2010). The effectiveness of wind and solar action can be improved by orienting the stockpile perpendicular to the predominant wind direction, maximizing the surface area of the pile, and reclaiming the coal from the pile gradually in shallow cuts over a large area (Williams, D.J. 2006)."

Jan 1, 2016

By Eleanor Kentish, Edward Batty, Alan Skarda

"The design of the tunnels at Bond Street Station includes a final sprayed concrete fireproofing layer. The performance of this layer was verified by a program of testing to Crossrail’s KT24 specification, which proved that a dosage of 1kg/m³ polypropylene fibers and a layer thickness of 50mm would be sufficient to limit spalling in the event of a fire. Application of this thin layer was achieved using a state of the art spraying robot, with the ability to scan the profile and automatically apply a uniform layer of concrete. To provide assurance and calibrate this spraying robot, BFK developed a bespoke survey system for checking SCL thicknesses in the field. This provided an instant independent check of the spraying robot and allowed areas of inadequate thickness to be rectified without risk of cold joints. This paper describes the practical application of the fireproofing layer and how design compliance was ensured. INTRODUCTION Fire is one of the most serious risks to a tunnel. The nature of tunnels — being long enclosed spaces — can increase the intensity of a fire, and make fire-fighting and rescue operations difficult. The damage that can be caused has been demonstrated by a number of historic tunnel fires, such as the Channel Tunnel fires of 1996 and 2008, and the Mont Blanc Tunnel fire in 1999. Without any intervention, the high temperatures in a fire create thermal stresses and a build-up of vapor pressure within the pores of concrete, which eventually exceed the tensile strength and trigger explosive spalling. Spalling exposes the core of the section to severe temperatures, leading to a loss of concrete and steel reinforcement strength or further spalling of successive layers. The concrete used in tunnel linings is particularly susceptible to explosive spalling, due to its low permeability achieved by the addition of microsilica (Bailey 2011). The sprayed concrete lined (SCL) tunnels on Crossrail have been designed to resist the worst anticipated fire in operation, in order to prevent collapse and minimize damage to the structure. The design called for a system of passive fire protection, the efficacy of which was validated by the contractor through a testing regime. It was critical that the application on site reflected the test conditions, which demanded special control of the profile and thickness of the lining. In order to meet these constraints on tolerances and quality, BAM Ferrovial Kier joint venture (BFK) developed a reliable method of working with the Meyco Logica spraying robot, and a bespoke survey system for accurately checking thicknesses in the field. These innovations are the focus of this paper."

Jan 1, 2016

By Tom Barry, Kameron Ray, Dr. Gavin Yuill

Imerys Talc, Yellowstone Mine in Montana faces significant geotechnical challenges such as poor wall quality and local instabilities. These instabilities are driven primarily by the characteristics of the rock mass, but are aggravated by drilling and blasting operations.

Jan 1, 2016

By Pedone Ezio Michele, Mohamed Dahir Holad

"The 4c segment is a part of the ""Oman National Railway Project” linking the mining area in the surroundings of Thumrait and the port of Salalah. It is 90 km long and the last 40 km stretch crosses a mountainous area near the city of Salalah. The project includes the excavation of a 33 km double and single bore tunnel and 10 km of safety tunnels. This mountainous area is a holiday destination for Omanis, thanks to its beautiful landscapes, especially in summer time due to the monsoon rains. The tunnelling design had to take into account both these environmental constraints and the limestone rock formations crossed, which are affected by significant karst features. Given the context, the conventional tunnelling method has been preferred. INTRODUCTION The Oman Railway Project (Fig. 1) covers the construction of approximately 2,150 km of railway line for freight and passenger transport which will connect together Oman’s main towns and industrial sites and it will form part of the Arabian Peninsula railway system “GCC Project”. The non-electrified double-track railway line must guarantee a speed of 220 km/h for passenger trains and 120 km/h for freight trains and must guarantee the transit of AAR (Association of American Railroad) H and D plates using clearance envelope according to AREMA (American Railway Engineering and Maintenance-of-Way Association) requirements. The design alignment must have maximum radiuses of curvature of 3,250m and a maximum gradient of 1.0%. The project is divided into 9 constructional and functional segments. •,Segment 4c will be constructed in the southern region of Oman, close to the border with Yemen, to connect the town of Thumrait with the Port of Salalah. •,Segment 4c will run through the Dhofar region and will be mainly used by the freight traffic which currently travels by road."

Jan 1, 2016

By J. D. Steenkamp, J. Muller

"Excavation of an industrial-scale submerged arc furnace, utilized in the production of silicomanganese, identified two high-wear areas in the refractory lining: the tap-hole, built with cold rammed carbon paste and SiC bricks, and the hearth, built with cold rammed carbon paste. To obtain insight into the potential causes of wear, thermodynamic calculations were conducted on eight sets of data, obtained for seven furnaces on three plants based in South Africa. FACTsage software and associated databases – FACTPS, FToxid, and FSstel – as well as the Mn-Fe-Si-C database of Tang and Olsen (2006), were applied. Theoretical indications are that chemical reaction between carbon refractory and slag, as well as dissolution of carbon and SiC refractory in metal, contributed to tap-hole refractory wear; and dissolution of carbon in metal contributed to hearth refractory wear. IntroductionDuring the excavation of a 48 MVA submerged arc furnace (SAF) used for silicomanganese (SiMn) production, it was found that the taphole and hearth were high refractory wear areas (Steenkamp, 2014). In both these highwear areas, carbon-based cold ramming paste formed the hot face refractory lining (crucible). The wear profile of this SAF is presented in Figure 1.The hot face refractory lining was formed by cold ramming of high-grade carbon ramming material. This material consisted of 50–70% anthracite, 15–25% graphite, 6–12% resin, 2–7% tar, 1–5% clay, and 1–5% alumina. The tap-hole was built using SiC bricks, consisting of 75% SiC, 23.4% Si3N4, 0.3% Fe2O3, 0.3% Al2O3, and 0.2% CaO.In the tap-hole area, the wear of the SiC refractory material was estimated at 0.4 t, and that of the high-grade carbon ramming material, at 1.9 t (Steenkamp, Pistorius, and Tangstad, 2015). The amounts of slag and metal tapped during six years of operation of the tap-hole (September 2007 to April 2013) were estimated at 33 088 t (Steenkamp et al.,2015) and 41 360 t, respectively."

Jan 1, 2016