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By Sandin E. Phillipson

"On April 5, 2010 a massive dust-fueled explosion at a longwall mine in southern West Virginia claimed the lives of 29 miners. The mine had experienced large gas inrushes from the floor on two known previous occasions, and natural gas was found emanating from floor fractures behind the longwall shields after the explosion, indicating a likely fuel source for the initial ignition. In succeeding months, another longwall mine operating in the same seam 15 miles away encountered smaller inflows of natural gas that halted production from two different longwall faces. Production was halted at a third longwall mine, 30 miles south of the first, in May 2011, when explosive levels of methane were detected inby the longwall face on the headgate. The same mine was evacuated on March 20, 2014 when a series of floor gas feeders were encountered on the longwall face. A literature review indicated that there has been little documentation or description of these events, and that their size and frequency are unknown. The most significant floor gas inrushes in the United States are believed to have been associated with longwall mining in the Pocahontas No. 3 Seam of western Virginia, in which an estimated 5.8 x 107 ft3 of natural gas was expended from a floor feeder on the longwall face over a two-week period (Aul, pers. comm.).A variety of mechanisms and circumstances are associated with methane emanations from underground mines. Hyman (1987) defined an outburst as a violent, simultaneous release of gas and comminuted rock material into a working face or the interior of a borehole, and indicated that certain soft or fractured coals have a propensity for outburst based on gas desorption rates. In this mechanism, reservoirs of autogenic gas hosted in pockets of soft, crushed coal surrounded by harder coal are released suddenly as confining stress is removed by mining. Hyman (1987) also suggested that highly stressed, relatively gassy coal that is penetrated by mining-induced fractures could be outburst-prone. Clayton et al. (1993) and Ulery (2008) recognized the importance of faults as potential conduits for gas from adjacent strata into coal mines, and suggested that biogenic gas trapped in adjacent strata could migrate into mined coal seams due to a pressure differential. Ulery (2008) distinguished between an outburst and a blower, the latter defined as an event expending a large amount of gas over an extended time period, most often emanating from underlying strata, but without expulsion of coal or rock. Methane feeders are further defined as a subset of blowers that continually expend gas over a long period of time but at a lower rate. Many of the mechanisms discussed by Ulery (2008) relate to geologic features that can impound gas within the seam, releasing a voluminous amount when mining breaches the elastic dike, fault gouge, or other geologic structure that had restricted and compartmentalized coalbed methane migration. Thus, the events discussed in this paper can be described as blowers and feeders. However, detailed geological observations of the three longwall mines discussed in this paper appear to indicate a mechanism that is different from those described by Hyman (1987) or Ulery (2008), in that they did not involve coalbed-sourced gas, and the reservoirs were not hosted by coal seams."

Jan 1, 2016

By C. Horstmann, D. Andreo, G. Barthold

"The concept of large single line grinding circuits provides a valid answer in project feasibility studies by reducing capital investment requirements compared to parallel lines for the same plant throughput rates. The benefits of this concept are reflected as well on the operational aspects, in terms of higher and greater process stability, and reduced operational costs mainly due to the associated lower maintenance expenditures. However, concerns exist in the minerals industry on whether large single line grinding could reduce the overall concentrator plant availability. The mechanical design and integrity, the mill and gearless mill drive integration, as well as assets management aspects of this type of equipment are the key to guarantee successful availability records. Together with an overview of the added value provided by large single line grinding circuits, this paper focuses on risk mitigation strategies during mill and gearless mill drive integration, as well as on the design of the equipment itself, for the key aspects which could put at risk the operations availability.INTRODUCTIONDespite a large long term demand for commodities, the mining industry has never faced complex challenges as it is doing today. Decreasing high-quality and accessible deposits, declining ore grades in existing mines, shortages of electrical energy (e.g. in Chile) and an aging workforce are the most significant among the megatrends affecting our industry. In addition to this, flat underlying commodity prices and high price volatility are currently posing strong requirements to miners when entering into the process of approving investments.Nowadays to get projects financially approved (optimizations, expansions, new plants), capital expenditure has to be reduced, as observed up to 30% compared to the last decade, and at the same time the plant design has to be such to demonstrate that operating costs will also be significantly lower than in the past.When it comes to the concentrator plant, the concept of large single line grinding circuits provides a valid answer in project feasibility studies by significantly reducing the capital investment requirements compared to parallel lines for the same plant throughput rates. The benefits of this concept are reflected as well on the operational costs, in terms of higher and greater process stability and reduced maintenance expenditures."

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 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 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 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 Patricia Pride, Kurt Bettger, Jack Raymer

"INTRODUCTION The Jefferson Barracks Tunnel is in the final stages of design and is expected to go out to bid in the summer of 2016. The project is located in south St. Louis County along the west bank of the Mississippi River, about 13 km downstream of the St. Louis Gateway Arch. The project consists of a deep sanitary sewer tunnel, a deep pump station and several intakes. The intakes will divert sanitary flows into the tunnel and the tunnel will convey the flows by gravity to the Lemay No. 3 Pump Station, which will pump them up into the Lemay Waste Water Treatment Plant. The tunnel is about 5.4 km long and will be lined with 84-inch (2.1 m) fiberglass pipe. It drops at a gradient of 0.1 percent from south to north and will be bored through strong limestone using a hard-rock tunnel boring machine (TBM). The diameter of the TBM is anticipated to be about 3.4 m. The Owner’s original concept was for a relatively shallow tunnel so as to minimize construction and pumping costs. The preferred alignment ran close to the river, next to the existing force main, which was to be abandoned. Keeping the tunnel close to the force main would reduce the amount of shallow sewer work needed to connect the existing feeder sewers to the new tunnel. Several geotechnical investigations were performed, with shallowly focused geophysics and the borings all going exactly down the conceptual tunnel depth. Limestone bluffs run along the Missouri side of the river. These bluffs are pockmarked by sinkholes and riddled with karst. Large, well-known caves occur both north and south of the alignment. Karst features, including deep crevices and possible caves, were found in those early geotechnical investigations. Many of these features extended well below the level of the Mississippi River and would have been encountered by the tunnel. If a large crevice or cave were encountered, then the inflow of mud and water into the tunnel could have been large and possibly uncontrollable. Something had to be done to mitigate this situation. Pre-excavation grouting was considered, but the program would have been huge and extremely expensive. Using a closed-face TBM with bolted and gasketed lining was also considered, but that too was both risky and extremely expensive. The Owner could have abandoned the tunnel altogether and built a new force main, but that would have brought a whole new set of problems and was undesirable to the Owner. The last option was to move the tunnel away from the karst."

Jan 1, 2016

By Olivier Kraft, Olaf Kortz

"Project-specific optimized tunnel boring machines represent the spearhead of technological progress in tunneling because with their use, very long-lasting, high quality tunnel structures in almost any geology, depth and topography can be produced with a high degree of automation. The mechanized excavation of tunnel structures ensures the greatest possible environmental protection during tunneling itself. Professional, systematic and high quality rebuilds and reuse of already proven equipment also ensures maximum efficiency in the use of materials and energy resources. It offers an enormous potential for a highly optimized environmental balance. Here the manufacturers of tunnel boring machines and their users in particular have a duty to ensure transparent, high quality and binding standards in the entire rebuild cycle and in the refurbishment management of innovative tunneling technology. This paper deals with the comprehensive processes with rebuild levels of tunnel boring machines and highlights some exemplarily implemented projects. 1 INTRODUCTION All over the world, the number of tunnel boring machines (TBM) in which equipment rebuilds from previous projects are re-used has increased over the last few years. This text presents the technical and economical aspects of this market development. It also takes a look at the practical implementation of rebuild measures. The ""ITAtech Guidelines on Rebuilds of Machinery for Mechanized Tunnel Excavation"" from 2015 lay down the requirements that the machine manufacturers must meet. 2 ECONOMICAL AND ECOLOGICAL ASPECTS OF RE-USING COMPONENTS The globalization of the construction sector and the consideration of environmental aspects promote an increased re-use of machines and machine components. Nowadays, large-scale construction projects are often carried out by international joint ventures of several individual companies that are established specifically for this purpose. After the completion of the project, the joint ventures are dissolved and they liquidate their project-specific equipment, such as tunnel boring machines. Today, it is much more uncommon for such machines to remain permanently in the possession of construction companies. Joint ventures offer TBMs on the free market, or they exercise contractually agreed repurchase options with the manufacturer. On the whole, this increases the number of re-usable components or complete tunneling systems available on the market."

Jan 1, 2016

By Uli Leiste

Two papers are presented which examine Air Deck Blasting, one from a computational aspect and the other from a shock aspect.

Jan 1, 2016

By Z. Hyder, M. D. Cleason

"INTRODUCTION Mine Ventilation has come a long way over the years. The main purpose of mine ventilation is to keep conditions in the mine safe for the worker so that the mine will be productive and profitable. Technological developments to the mine ventilation system itself and the development of mining techniques have helped improve the safety and productivity of the miners and the mine. Most of the developments to mine ventilation and to safety devices came as the result of serious mining disasters. Another effect of those mining disasters, especially in the late 19th century and after, was legislation to set specific safety standards for mines, especially in the underground coal mines. This paper will focus on the connection between mines disasters and the mine safety legislations promulgated because of those disasters. A BRIEF HISTORY OF MINE SAFETY LEGISLATION Mine legislation has a long history in the U.S. dating back well in the 1800’s. However, mine safety legislation is considerably newer. In 1891, the U.S. Congress passed the very first version of mine safety legislations setting up minimum safety standards. By today’s standards, the 1891 legislation was incredibly basic (7). It took a series of horrific mining disasters for Congress to take action a second time. In 1910, Congress established the Bureau of mines. The role of Bureau developed and changed over next 60 years. In 1995, Congress voted to disband it (27). Initially the Bureau was only charged with investigating and coming up with ways to reduce accidents in coal mines. It was not until 1941, when Congress formally allowed Bureau of Mines’ Inspectors into the mines. In 1947, the Congress enacted and adopted a set of federal safety regulations for the inspectors to follow (1). Finally, in 1952 Congress granted the Bureau of Mines the authority to inspect the mines and to issue citations and/or orders of withdrawals. This act was known as the 1952 Coal Act and the penalties were limited to civil penalties. It would take a couple more iterations of mine safety legislation for monetary and criminal penalties to be introduced (10). Up until 1966, mine safety legislation was directed primarily at underground coal mines and surface coal mines. Congress passed the Federal Metal and Nonmetallic Mine Safety Act of 1966, thus providing a set of standards for all mines to follow (1). The 1952 Coal Act was amended again to be the Federal Coal Mine Health and Safety Act of 1969. This amendment was the beginning of modern mine safety legislation (13). In 1973, Congress created what can be considered the first ‘version’ of the modern day MSHA (Mine Safety and Health Administration). The initial version was the Mining Enforcement and Safety Administrations or MESA. Congress created MESA to act as the enforcement agency, relieving the Bureau of Mines of that responsibility so they could focus on their initial purpose, the development of countries natural resources (14). As mining industry grew, mine safety and health became a greater concern and priority. More efforts were put in legislating the industry. The Federal Mine Safety and Health Act of 1977 provided the platform for today’s mine safety and health legislation. Under the Federal Mine Safety and Health Act of 1977, also known as the Mine Act, MSHA came into being (1)."

Jan 1, 2016

By Corby G. Anderson, Caelen D. Anderson, Patrick R. Taylor

"The United States contains a variety of domestic rare earth element mineral sources containing such as ancylite, bastnasite, monazite, and xenotime. Research has been performed to investigate the fundamental surface chemistry involved in the froth flotation of these minerals, and apply the knowledge gained to substantiate the results through experimental testwork on a domestically sourced rare earth ore. This paper will outline the fundamentals and literature of rare earth mineral flotation, review its industrial applications and provide some recent research updates.THE RARE EARTH ELEMENTSRare earth elements (REE’s) are a unique family of elements with nearly identical physical and chemical properties. They account for approximately 1/6th of all naturally occurring elements, but the entire group occupies only one position on the periodic table. These 15 elements make up the lanthanide series (atomic numbers 57–71), and all but one (promethium) occur naturally. In addition to these 15 elements, yttrium and scandium are also considered rare earths since they tend to occur in the same deposits as the rare earths and share similar physical and chemical properties as seen in Figure 1. In particular Figure 2 denotes, a cartoon of the subtle differences in each caused by the 4f atomic sub shell (Gschneidner Jr., 1964). These subtle differences result in very difficult challenges in the selective concentration and final separation of each rare earth. (Anderson, 2015, Kronholm, Anderson, Taylor, 2013)Rare earths are separated into two different subsections; the “lights” or LREE’s (lanthanum57 through europium63) and the “heavies” or HREE’s (gadolinium64 through lutetium71). Yttrium is generally considered a heavy rare earth since its ionic radius is close to that of the HREE’s, while scandium is not considered either a light or a heavy."

Jan 1, 2016

By Sepulvedam Jaime E., Levi Guzmán Rivera

"Grinding media consumption rates and their dependence on key operating conditions in semiautogenous grinding mills is analyzed on the basis of a detailed mathematical model recently developed by Moly-Cop´s specialists which describes and takes into account the three primary media consumption mechanisms, namely: abrasion/corrosion, surface spalling and impact ball breakage. The influence of key mill operating conditions – such as ball filling, discharge grate opening, mill speed, lifter profile, and ball quality – on their corresponding grinding media consumption rates is explored via a variety of model simulations, discussing in every case the independent contribution of each of the indicated consumption mechanisms to the estimated total ball consumption rate.INTRODUCTIONA thorough understanding of the independent contribution of each grinding media wear mechanism is extremely important, especially in semi-autogenous grinding (SAG) operations where macrowear (spalling) and ball breakage cannot be ignored or neglected. The high impact conditions imposed in modern SAG milling environments has created serious challenges for grinding media manufacturers since their products must be able to perform with minimal breakage and surface spalling.GRINDING MEDIA WEAR MECHANISMFor SAG milling operations, at least 3 different mechanisms have been identified as the main contributors to the observed overall grinding media consumption, here referred to as: abrasion / corrosion, ball breakage and surface spalling.Wear by Abrasion/CorrosionThe abrasive/corrosive wear mechanism has been discussed in depth in previous publications (Benavente Hector, 2007; Guzman Levi, 2014; Sepulveda and Morrow, 2014). The most widely accepted approach to mathematically characterize the consumption (wear) kinetics of grinding media in rotary tumbling mills is known as the Linear Wear Theory (Prentice, 1943; Norquist, 1950; Sepulveda, 2004) which claims that—at each instant 't' after a grinding body enters the mill load—the rate at which the body loses weight is directly proportional to its surface area exposed."

Jan 1, 2016

By Steve Skelhorn, Dan Ifrim

"A tunnel project poses many challenges; the operation of the Tunnel Boring Machine (TBM) being one of them. Mechanized tunneling is known as a safe and effective alternative to other methods in terms of schedule and cost; however, efficiency can be severely affected by a bad TBM selection and qualification and employment of inexperienced operators. The success of a mechanized tunneling project involves a comprehensive and interdisciplinary consideration of all contributing factors such as TBM technical specification and selection, TBM design and procurement including ancillary equipment and tunnel linings. The tunnel equipment selection along with the operation can make or break the project. The objective of this paper is to address the importance of the skills and qualifications of the TBM crew with particularity to the TBM Operator. The study includes the Owner and Consultant involvement in the selection and pre-qualification of the TBM crew and specifically the TBM operator as well as the role of Contractor and TBM manufacturer in TBM operator training. This paper also analyzes the possibility of issuing a TBM operator certification, and discusses the benefits and significance of periodic training and certification programs. INTRODUCTION Training in the tunneling industry is not a new topic. The industry continues to evolve and become more complex with technology advances and expansion of mechanical tunnelling to mechanized shaft construction, large diameter drilling and mining industry applications. The need for professionals trained to operate mechanized tunnelling equipment is ever increasing, while there is a significant number of veterans who will be ageing out in the next 5 years. Consequently attracting young professional is a very important aspect of sustaining a qualified pool of professionals. For any given tunnel project, the owner and the engineer spend up to several years, studying the ground conditions during preliminary and final design. Post contract award the contractor spend additional months studying the ground again to develop the optimum means and methods for construction. All this time and money spent at the beginning of the project has the purpose of developing the optimum tunnel design, assessing the risk associated and implementing mitigation measures to reduce risks to acceptable levels. Following the tunnel design process, sophisticated TBMs are being specified and sourced to ensure the best tool for the job. The question raises here: Are there available experienced/trained professionals capable of operating these sophisticated machines?"

Jan 1, 2016

"One of the major issues that the Rare Earth Elements Mining Industry has to deal with is the legislation vacuum that exists in many countries around the world. Among these, are countries which have long history and tradition in mining. In many cases the lack of direct legislation for REE mine management as well as for other potentially polluting industries can be a barrier to sustainable development. Moreover, the case of lax legislation in China has led to environmental pollution problems and extended smuggling of rare earth elements. This paper looks into the current regulatory status on the mining of REEs, identifies the loopholes and suggests some elements for a new global legislation framework for sustainable development in the REE mining industry. The setting of this regulatory framework will be in line with the present and future challenges of the rare earths market as well as with the policy strategies that are defined internationally. The aim of such a legislative framework will be to strengthen the global rare earth elements supply chain, appease social concerns and ensure the preservation and conservation of the environment. INTRODUCTION The general public received their first introduction to rare earth elements (REEs) in 2010, when the previously inconspicuous commodities became the subjects of front-page headlines. It was when China created a furore in global high-tech markets after imposing an embargo on Japan following a minor marine dispute (Barakos et al. 2015b). Soon enough the Chinese embargo was extended on REE export restrictions all over the world and thus aroused concerns to many countries over potential supply disruptions. The world had suddenly realized that these wonder materials underpin products that they care about. Governmental and industry executives, policymakers and material scientists voiced concerns and conducted numerous reports stating the situation and the risks of a supply crisis. The price spike of 2011 intensified the crisis and the public turmoil, yet the drama did not last for long as the prices declined significantly in 2012. Nevertheless, the world was nonplussed by the fact that China has the total control of the market with more or less the 90% of the global production. More potential entrants became interested, thus initiating an exploration boom during the recent years that has resulted in a significant increase in known global REE reserves that could have potentials for exploitation."

Jan 1, 2016

By D. D. Gertenbach

"The successful commercialization of a pressure oxidation (POX) process for recovering metal values, including gold, copper, zinc, nickel and molybdenum, is the result of a carefully planned development program. The initial task involves developing one or more conceptual flowsheets, including the POX autoclave and downstream purification and recovery steps. A laboratory program is completed to determine the technical viability of the flowsheets, define the operating parameters for each step and provide information for an initial economic assessment of the process. The process is then confirmed during a continuous pilot plant program, providing engineering design data and other information for the commercial design. A well-thought-out development program has been shown to be critical for reducing the risk of commercializing POX processes. Experiences developing POX processes for refractory gold ores and copper concentrates are briefly discussed. IntroductionPressure oxidation (POX) has become a common commercial operation for processing sulfide-bearing feedstocks. These feedstocks include gold ores and concentrates; copper concentrates; nickel concentrates and mattes; zinc concentrates; and molybdenum concentrates. Drivers for the development and commercialization of POX processes include:• The high cost for pyrometallurgical processing of sulfide ores, much of which is attributed to environmental controls.• The motivation to implement safe and more environmentally attractive alternatives for sulfide ores.• The need to process increasingly difficult ores with complex mineralogy.• Improvements made over the last 25 years in POX equipment design and experience operating commercial POX plants.Although the capital and operating costs for commercial POX processing can be high, this technology is capable of rapid oxidation of most sulfides and arsenic minerals in the feed, with little noxious gases and environmentally stable iron arsenate and other iron compounds in the POX residue (Marsden and House, 2006).In POX operations, sulfides are oxidized to either sulfates or elemental sulfur in an autoclave at elevated temperature and pressure with oxygen gas. An example is the overall oxidation reactions of chalcopyrite when sufficient oxygen is present, shown in the following reactions:"

Jan 1, 2016

By P. James

"INTRODUCTION Control of target stream acidity is widely used in MIW (mining influenced water). Tailoring pH (a measure of acidity) finds application for controlling key chemistry in both process and waste streams. Traditional lime addition for neutralization and precipitation is most often used but has high reagent costs and results in large amounts of mixed metal sludge requiring costly disposal. A new adaptation of BPS’s patented DEMET™ technology (Dynamic Electrolytic Metal Effluent Treatment) platform offers a potentially improved and “reagentless” alternative to traditional chemical addition for pH adjustment. Electricity rather than chemical addition utilized in BPS’s proprietary approach controllably tailors target stream pH. The method offers a simple, low-cost processing technique yielding cleaner treatment chemistry. BPS’s “green” approach may yield lower operating (OPEX) and life cycle costs and significant reductions (up to 50%) in sludge generation compared to conventional lime treatment. It can also allow new opportunities to generate revenue via selective recovery of valuable processing byproducts. Specific savings and revenues depend on the target site chemistries, details, and processing goals. A more detailed discussion of the process and its operational principles may be found in Reference One.[1] Here application of the BPS treatment to POx (Pressure Oxidation) leaching as an alternative to traditional chemical addition is examined. An example operation process flow for gold mining is considered.[2] Promising processing points for potentially replacing conventional processes with DEMET are noted. The possibilities for lowering OPEX costs, lessening sludge creation, and capturing various valuable byproducts and residuals are examined. Financial life cycle benefit estimates of the principal gains provided by DEMET application to the example operation are noted. Extension and generalization of the analyses to a wider range of scenarios is explored."

Jan 1, 2016

By Michael N. Maltezos

"There is certainly no argument that LED lighting systems have taken a strong foothold in the lighting marketplace over the last several years. This has even proven true in the world of transportation and transit lighting, for which new LED cobra head style luminaires are replacing traditional HID cobra head luminaires on North America’s roadwaysand linear LED light fixtures are replacing conventional linear fluorescent light fixtures in North American rail transit facilities. However, LED technology has taken a while longer to penetrate the very specific market of vehicular tunnel lighting in this continent. Though both the New York/New Jersey Holland and Lincoln Tunnels have recently been retrofitted with LED lighting, and an LED Lighting RFP is currently out for Boston’s Central Artery Tunnels, very few vehicular tunnels in North America to date have been illuminated with LED light fixtures. This is largely because cost effective LED lighting, that met our typically stringent tunnel lighting standards, was until recently simply unattainable. However, with the rapid advances in LED technology over recent years, owners and specifiers of North American tunnel lighting projects have finally begun to adopt LED lighting systems as the norm. In fact, a recent Lux Fit/Yole Development “LED in Road and Street Lighting Report” stated that “LED luminaire growth will be driven firstly by tunnel lighting, and then relayed into highway, road, residential and amenity lighting applications starting in 2014.” 1 Our highways are continually becoming more congested. As a result, Provincial and State Departments of Transportation (DOTs) are constantly looking for innovative ways to improve traffic flow. One way DOTs are now helping to ease congestion is by expanding the use of tunnels and long underpasses in large interchange reconstruction projects. With less available right-of-way to work with, and the high costs of maintaining elevated bridge structures over the years, it often makes more sense to “go under” (rather than over) the traffic congestion points. With the addition of these new tunnels and long underpasses comes the issue of proper illumination within these structures, for a safe and efficient driving task. DOTs use recommended lighting practices and guidelines for highway lighting, which include specific criteria for tunnels, set by either the Illuminating Engineering Society of North America (IESNA) or the American Association of State Highway and Transportation Officials (AASHTO). However, both IESNA and AASHTO point out that these recommended practices and guidelines are not a mandate, and DOTs are free to make their own decisions about lighting criteria. Accordingly, effectively illuminating tunnels is often times a challenge. This paper will examine the key considerations of the tunnel lighting application in generalas well as what LEDs now bring to the table and how, accordingly, traditional lighting technologies will be phased out in the future illumination of tunnels."

Jan 1, 2016

By Marc Tardif

"The way alarm information is provided to an operator can make a huge difference in the minutes following an upset. Process alarms are often looked at as a way to help avoid catastrophic failure and serious accidents. But knowing that mineral processing is so energy consuming and that raw material is not consistent, all small upsets should also be seen as a catastrophe because they can have significant impact on product cost and quality.This paper will demonstrate how it is possible to use data from process alarms to provide operators with real time, value added information that will help them take the right decision at the right time and in turn, reduce unplanned downtime by 20 to 80% and incidents by up to 50% (number and cost),and optimize energy and capacity usage.In the era of Big Data, living in a world where we are submerged with information, one of the biggest challenges is to find the right information at the right time.Alarm rationalization projects will often focus on alarm quantity, but alarm quality is also very important. It is possible, by following a simple 6-step process to turn “alarms” into truly valuable information for operators. Based on known standards (ANSI/ISA 18.2 and EEMUA 191), this process will capture the knowledge of the best and most experienced operators and process engineers, and make it readily available to everyone, right on time, when it matters the most.INTRODUCTIONWhen spending some time in a modern control room, it is easy to notice the huge quantity of information that is available to the operator. Modern operation stations feature multiple screens with HD capability. These screens display information like process display, history trends, alarms and events list, maps with geo-located information, images from live cameras, etc. However, it is harder to assess whether all this information is really helping operators: Is all the information relevant? Are process screens overcrowded? Is the information easy to understand? Does the operator know what to do with all the information? Are there too many alarms?"

Jan 1, 2016

By Thomas Konstantis, Spyridon Konstantis, Panagiotis Spyridis

"Tunneling and Underground works are unequivocally subject to a diversity of inherent uncertainties associated with the geotechnical, hydro-geological and environmental regime that surrounds them. On many occasions, these uncertainties can provoke loss events of considerable consequences. The present contribution elaborates on losses that the insurance market has suffered in the recent years, following a construction failure event. These losses are being considered and analysed on a quantitative basis through evaluation of cost related data, with explicit discretization of the applied construction methodology and of the subsequent developed failure type since both of which are considered of major importance. Given the identified persistence and regularity of some loss-contributing factors, recommendations are provided on the basis of a proactive risk engineering management approach that are envisaged to reinforce the understanding of project risks and alleviate the incurred insurance cost. 1 INTRODUCTION The underground construction sector has always been a very challenging area for all involved parties, including the insurance market. Main reason for that remains the uniqueness of the uncertainties sources and the subsequent inherent risks that the tunneling and underground projects are exposed to. In many instances, these risks materialize, leading to loss events with substantially high impact on reinstatement cost and incurred delays, which depending among others on the insurance coverage will have to be bared by the Insurance market. In the recent decades and as the tunneling industry boomed and expanded with many major and significant projects undertaken around the world, the insurance market was faced with additional challenges. Increased competition during tender coupled with the scale and complexity of the projects and politically driven decision making exerted pressure on the project timelines, completion dates and budget. The pressure for on-time or even early project completion- to avoid liquidated damages or achieve bonus payments, respectively- along with cost reduction efforts and the incentive for innovative failure events. That, in turn, put additional pressure on the Insurance market which had experienced a significant amount of losses with substantial cost. One of the triggered mitigation actions was the introduction of the Code of Practice for Risk Management of Tunnel Works (ITIG, 2006 & 2012; MunichRe 2006, Wannick, 2007, Spencer, 2008, Adeyemo, 2011)."

Jan 1, 2016