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By Esterhuizen S. Gabriel, Su W. H. Daniel, Tulu B. Ihsan, Klemetti M. Ted, Mohammed M. Khaled, Gearhart F. Dave

"A numerical-model-based approach was recently developed for estimating the changes in both the horizontal and vertical loading conditions induced by an approaching longwall face. In this approach, a systematic procedure is used to estimate the model inputs. Shearing along the bedding planes is modeled with ubiquitous joint elements and interface elements. Coal is modeled with a newly developed coal mass model. The response of the gob is calibrated with back analysis of subsidence data and the results of previously published laboratory tests on rock fragments. The model results have been verified with the subsidence and stress data recently collected from a longwall mine in the eastern United States. INTRODUCTION In 2015, there were 40 longwall mines operating in the United States, each producing an average of 4.5 million tons of coal per year, and they supplied 60% of the U.S. underground coal production. This represents a substantial increase from 50% three years earlier (Sears, Tulu, and Esterhuizen, 2017). During this period, reportable roof fall rates in U.S. longwall mines also increased. Large roof falls that can block the gateroads are not only a ground-fall hazard, they can disrupt the ventilation system, block the escapeways, and increase the potential for elevated methane levels in the gob. To address these hazards, the National Institute for Occupational Safety and Health (NIOSH) Pittsburgh Mining Research Division (PMRD) is conducting research to improve the design of ground control systems in longwall gateroads. Gateroad stability is primarily determined by the longwall pillar design. Generally, the required dimensions of the pillars around a longwall panel are determined first, which then dictates the location of the gate entries relative to the mined panel. The Analysis of Longwall Pillar Stability (ALPS) method is the most accepted gateroad pillar design procedure in the United States (Mark, 1992). The ALPS method accounts for local roof geology in the gateroad stability assessment by including the Coal Mine Roof Rating as an input parameter (Mark, 1992). The key assumption in the ALPS method is that unstable pillars result in unstable gate entries. However, experience provides examples of mines where pillar stability and gateroad stability are only loosely correlated (Su, Draskovich, and Thomas, 2003)."

Jan 1, 2017

By P. T. Bissert, L. Yan, J. R. Srednicki, J. A. Yonkey

"Refuge alternatives (RAs) are required in underground coal mines to support life post-disaster. RAs are mandated by MSHA to maintain an apparent temperature (AT) at or below 95°F (35°C) while providing a safe and livable shelter for a minimum of 96 hours. Because strata composition and mine temperatures will affect the final AT within an occupied RA, NIOSH researchers have collaborated with five underground coal mines across the US to characterize the effects of geographic location and seasonal temperature fluctuations on mine air temperature, relative humidity, and mine strata temperatures. The data collected indicates that some mines will experience greater temperature fluctuations than others, based on geographic location. The mine which demonstrated the greatest temperature differential over the course of the year resulted in a mine air temperature that ranged from 53.4°F (11.9°C) to 84.2°F (29.0°C) and a rib surface temperature that ranged from 55.4°F (13.0°C) to 82.8°F (28.2°C). This data suggests that the location and seasonal peak temperature can significantly affect the mine strata temperature, which could lead to a fully occupied RA exceeding the 95°F (35°C) AT limit over the course of 96 hours. The data reported in this paper could be used to examine the heat buildup inside an RA for actual mine conditions. Thermal simulations could be implemented to evaluate maximum occupancy ratings based on actual mine temperatures and strata compositions. INTRODUCTION In the event of a mine disaster, miners’ primary focus is to escape. Should their attempt be futile, they can enter a refuge alternative (RA) to await rescue. In 2008, the Mine Safety and Health Administration (MSHA) mandated that underground coal mines implement RAs within 1,000 ft (304.8 m) of the working face and spaced within one-hour travel distances in outby areas where persons work such that persons in outby areas are never more than than a 30-minute travel distance from an RA or safe exit. These RAs are required to provide a safe and habitable shelter for a minimum of 96 hours and to prevent the apparent temperature (AT) from exceeding 95°F (35°C) [1]. There is concern throughout the industry that in some cases the internal ambient of occupied RAs may exceed the 95°F (35°C) AT limit due to the potentially hot mine atmosphere as well as the metabolic heat generated by RA occupants and the carbon dioxide scrubbing system. The National Institute for Occupational Safety and Health (NIOSH) has conducted tests in its Safety Research Coal Mine (SRCM) and its Experimental Mine (EM) to investigate heat buildup in RAs. It was found that the number of occupants in an RA may need to be reduced based on the ambient mine temperature, which varies from mine to mine [2]. Further testing and analyses were completed to evaluate the mechanisms (conduction, convection, radiation) by which heat is transferred from an RA to the mine surroundings. Additionally, the effects of varying mine strata compositions on the heat buildup inside an RA were studied [3]. The mine strata temperatures will increase due to heat transfer from within an RA. Depending on the mine strata composition, some mines may be more thermally conductive than others. For example, sandstone is much more conductive than shale or coal (i.e. it disippates heat at a quicker rate). All things being equal, the air temperature inside of an RA after 96 hours will be higher for a mine with strata that has low thermal conductivity compared to a mine with high thermal conductivity."

Jan 1, 2017

By Natalie Zeleznik, Brian Hawkins, David Bradley, Rachel Gooding, Patrick Wilson, Brian Somes

"To perform a probabilistic risk assessment (PRA), a method of quantifying the risks associated withinfrequent, high consequence events, consequence models that generate representative estimates of human health consequences for a wide variety of representative scenarios are commonly used. Criteria that suitable models must possess include: (1) input requirements necessary to generate large volumes ofprobabilistic simulations; (2) the capability to output injuries with the necessary details and resolution;(3) the ability to capture the variety of different scenarios inherent in an assessment; (4) acceptablecomputational requirements; and (5) sufficient stakeholder buy-in for community acceptance."

Jan 1, 2017

By P. Lind, A. Gagnon

"Goldcorp has embarked upon an ambitious, industry-leading, multi-year water use reduction effort. This is a proactive, voluntary effort that reflects our commitment to truly sustainable mining. This effort will focus on increasing water re-use and recycling, and reducing water inputs ultimately towards zero. All of our operating mines are expected to contribute to this effort and are currently in the process of developing plans to meet short and long term objectives. One of the largest needle movers to increase water re-use and recycling is in the area of tailings management. Within five to ten years at Goldcorp, it is envisioned that the need for wet tailings dams will be eliminated and that all new tailings facilities will consist of only filtered or dewatered tailings. Filtered tailings is developing into a mature technology with wide application in mine waste management. This paper describes a conceptual level evaluation on the transition from a slurry to a filtered tailings operation at the Cerro Negro mine in southern Argentina. Key benefits and challenges are highlighted.INTRODUCTION Goldcorp’s Cerro Negro operation is located in the Santa Cruz province in the Patagonian region of Argentina. Cerro Negro has been in operation since 2014 and commercial production was achieved on January 1, 2015. The processing capacity of the plant is 4,000 tonnes of ore per day and in 2016 produced 363,000 ounces of gold and 3.1 million ounces of silver (Goldcorp Inc., 2017). As the mine is located in a semi-arid area, it is important to evaluate technologies that could reduce freshwater consumption and maximize water re-use and recycle rates. The current tailings operation at Cerro Negro incorporates pumping of tailings slurry into a conventionally lined Tailings Storage Facility (TSF). Water is reclaimed from the tailings supernatant pond to the process plant via pumps, however, water losses occur due to evaporation and solution retention within the slurry tailings voids. Converting to a filtered or dewatered tailings operation would allow for increased water recovery prior to tailings disposal, and decreased water losses from evaporation and from retention in the tailings solids void space. This paper describes a conceptual level evaluation on the transition to filtered or dewatered tailings with the primary objective of moving closer Towards Zero Water."

Jan 1, 2017

By T. Resende, J. Sismour

"Signs in underground mines are subject to variable airflow, which carries dust and moisture. Dust buildup reduces their visibility, hampering production efficiency and safety. Underground workers commonly must stop to clean signs in order to gauge their location, or find critical supplies or services. There are currently a variety of coating products, including dust and water repellants, available on the market that have the potential to reduce dust accumulation on sign surfaces. This paper describes a preliminary study to determine their effectiveness. The study involved a practical testing protocol using a trickle rock duster and samples cut from a clean, used road sign. Product effectiveness, under both dry and wet conditions, was evaluated based on photographic evidence by comparing changes in sign luminosity after a period of rock dust application. By analyzing the frequency of different pixel luminosities on the dust-covered samples, both uniformity of dust coverage and the total amount of accumulation was assessed. Results indicate that at least one product may reduce the amount of dust buildup on sign surfaces and increase visibility. INTRODUCTION In all underground mines, visibility of signage is critical. Signs inform miners of their location, direction toward escape routes, and location of supplies. Over time, sign surfaces can collect dust and can eventually become unreadable. The rate of dust accumulation on surfaces is often particularly high in coal mines, where both mining (e.g., cutting and drilling) and rock dusting activities can contribute significant amounts of dust to the airways. Several factors may contribute to dust buildup on sign surfaces. First, basic principles of fluid and particle flow are at play. When a fluid travels past a stationary surface, the velocity of the fluid at the surface boundary is zero. If a very small dust particle moving with air collides with a surface, it does not immediately fall off since the air velocity is zero at the sign surface. (This is the same reason that dust can collect on a rotating ceiling fan.) Further, once the collision occurs, other mechanisms may help keep the particle there – including friction that resists particle falling due to gravity, and adhesive forces due to humidity and/or static charges the particle and others already on the surface. Currently, the most common way to deal with reduced sign visibility due to dust buildup is for mine personnel (e.g., a compliance foreman, supply worker) to periodically clean sign surfaces – usually just by wiping them with a cloth. As a regular activity, this solution is inefficient; in cases of emergencies, it can also pose unnecessary risks. Application of an off-the-shelf coating to sign surfaces may represent a simple yet effective way to reduce the rate of dust accumulation. There are currently a variety of products on the market that may be suitable for this purpose, including dust and water repellants."

Jan 1, 2017

By K. L. Boyd

"Can the ever-increasing tonnages of ore and waste being mined today be accommodated simply by using bigger and better crushers? This paper reviews the latest primary crushing and large cone crusher designs. It highlights how—in addition to using the larger crushers now available—maximizing the utilization percentages in each of the four stages of the rock size reduction circuit will assist in meeting the larger production requirements of existing and new mining operations. Its goal is to help consultants and operators select the optimal equipment and custom-designed items in the material handling flowsheet from the mine to the mill, maximizing operating hours per year. INTRODUCTION Are larger crushers the answer to meeting the demands of existing or new mining projects for increased tonnage? Boyd (2002) predicted that larger crushers for primary and fine crushing would be beneficial and contribute to the further development of mineral processing. Larger crushers for primary and fine crushing applications are now available. The rock size reduction process from the mine to the selected milling process facility has not changed since man first broke a rock to get at the interesting mineralization within. The rock size reduction process circuit from the mine to the mill can be summarized in four stages: • Stage 1: Mining (rock breakage and fragmentation) • Stage 2: Pre-screening (scalping) • Stage 3: Primary crushing • Stage 4: Fine crushing (secondary, tertiary and quaternary) Plant throughput and ore delivery schedule will form the basis for flowsheet design and equipment selection. Once the project design criteria and the mine plan have been established, the circuit’s utilization percentage (percentage of hours when the circuit is being utilized) can be optimized for each of the four stages. The mining and process departments are the key stakeholders in the selection of the final comminution circuit, and both departments should be familiar with and contribute to the design of the circuit. This paper focuses on the four stages of a rock size reduction circuit from the mine to the mill, equipment selection, various ore and waste handling flowsheets, and improvements in crusher station design, all with the purpose of maximizing availability and plant utilization percentages. What is a large tonnage? From 1907 to 1914, the American Panama Canal excavated 300 million tonnes of material in 7 years (History of the Panama Canal, Wikipedia). Today’s large mining operations can move the same material in 10 months, using large crushers or multiple crushers for ore processing and large crushers and a mixture of truck haulage and conveyors for handling the large waste tonnages. Some examples include:"

Jan 1, 2017

By C. Xiao, F. Mohamm, A. Borsoi

"Nitrogen compounds produced by cyanide destruction and/or blasting are often a cause of concern for environmental compliance and at times, for water re-use in metallurgical circuits. Natural attenuation in tailings ponds and wetlands is not always sufficient to ensure compliance and/or achievement of overall water management objectives. This paper provides a general overview of active treatment methods for nitrogen management followed by an investigation of selective adsorption combined with electro-oxidation as the potential treatment method for thiocyanate. Results from bench scale treatability study are presented. The concept of holistic assessment of nitrogen management at mine sites using Risk Adjusted Life Cycle Cost is introduced and discussed in the context of gold mining operations using sodium cyanide.INTRODUCTION Unlike metals, nitrogen compounds present in mine waters originate entirely from anthropogenic sources rather than mineral deposits. Table 1 summarizes the main sources of nitrogen compounds reporting to mine wastewater.The best management practice related to the use of ANFO involves minimizing contact between ANFO and water, control and monitoring of blasting to reduce the occurrence of misfires, and reducing the consumption of blasting reagents for a given ore body. The most common practice for the management of NaCN is the incorporation of cyanide destruction in the metallurgical flowsheet and the use of tailings impoundments and holding ponds for natural attenuation of cyanide destruction residues such as NH4-N and CNO. At most mine sites there is no active management of NO3-N and SCN in wastewater. While current practices have produced satisfactory results, new enhanced methods to manage nitrogen compounds at mines are needed due to: 1) Increased scrutiny over the adverse effects of nitrogen compounds released into the environment; 2) New effluent standards; and 3) The shift away from wet tailings towards dry stack systems resulting in diminished natural attenuation and dilution of nitrogen residues prior to effluent discharge or water re-use in mineral processing."

Jan 1, 2017

By J. F. Burr, D. Snyder, W. Calder

"INTRODUCTION “Explosion protection” refers to techniques used to minimize the potential for electrical and electronic equipment to create an ignition while operating in a hazardous location (HAZLOC). In particular, U.S. coal mines are required to use equipment in certain areas of the mine that has been approved by the Mine Safety and Health Administration (MSHA) for use in a methane and coal dust environment to limit the risk of the equipment creating an ignition-capable spark or a thermal energy ignition. In general, MSHA’s regulations for explosion protection recognize two techniques: the use of explosion-proof enclosures (XP boxes) and 2-fault intrinsic safety for electrical and electronic equipment. For 2-fault intrinsically safe (IS) equipment, the U.S. mining industry requirements are unique in that the equipment is certified by MSHA. The criteria MSHA uses to evaluate equipment for intrinsic safety, as required by Title 30 of the Code of Federal Regulations (30 CFR) [30 CFR, Sections18.20(b), 18.68(a)(1), 19.1(b), 20.1(c)(2), 22.6, 23.6, and 27.20(a)], is published in a document referred to as ACRI2001 (1). Outside of U.S. underground mining, many industries and countries accept equipment that is designed to a consensus-based international standard (ANSI/ISA 60079-11 is the U.S. version). The purpose of this study is to provide an overall assessment of the ANSI/ISA 60079-11 standard on 2-fault intrinsic safety and the MSHA ACRI2001 acceptance criteria, and determine if the ANSI/ISA document can be an alternative to ACRI2001 while maintaining an equivalent or better level of safety for miners. There are many drivers for this study. First, immediately after the 2006 MINER Act (2) was passed, there was a perception in the industry that the unique MSHA requirements were contributing to delays or restricting the availability of equipment to meet the requirements of the Act. Additionally, the MINER Act required that mine operators submit an accident response plan for MSHA approval, to be reviewed every six months. MSHA is required to determine if these plans reflect the most recent credible scientific research and make use of currently commercially available technology. There is a concern, as expressed in a recent National Academy of Science (NAS) study (3), that the unique requirements for U.S. mining may be limiting the technologies available to coal miners and technology options for mine operators. Accordingly, the study recommended that the National Institute for Occupational Safety and Health (NIOSH) and MSHA re-examine their technology approval and certification processes to ensure they are not deterring innovation, and explore opportunities to cooperate with other international approval organizations to harmonize U.S. and international standards without compromising safety. Lastly, the National Technology Transfer Act (NTTA) and the accompanying Office of Management and Budget’s OMB-119 circular mandate the use of consensus-based standards by federal agencies. However, for U.S. mining operations, MSHA cannot accept such standards unless a determination is made that such standards provide an equivalent level of protection for the miner, per the requirements of the 1977 Mine Act, the 2006 MINER Act, and 30 CFR Part 18 regulations."

Jan 1, 2017

By M. Gobla

"Since 1994 the Bureau of Reclamation has used risk analysis to evaluate dams. Risk considers both the likelihood of failure and the expected consequences should failure occur. Risk analysis relies on the detailed formulation and critical analysis of all possible potential failure modes. Potential failure modes are formulated by describing the sequence of events that must occur to result in failure, where failure is defined as the uncontrolled release of the impounded reservoir. Failure occurs in response to loadings such as water seepage through a dam (static forces), shaking from an earthquake (dynamic forces), sudden flood inflows (hydrologic forces), or accidental overfilling (operational errors). Reclamation has applied risk analysis methods to inactive and abandoned mines to evaluate tailings dams and flooded underground mines. Case histories of potential failure mode analysis as applied to mine impounded water illustrates what critical technical information is needed to determine if failure is likely, what the consequences of failure are likely to be, and what are the highest risks that should be addressed first. INTRODUCTION Impounded water, and high water content wastes, at mining and industrial processing sites are potential threats to public safety and the environment. Recent failures such as the TVA Kingston flyash impoundment failure in Tennessee in 2008 (5.4 million yd3 released), the Mt Poly Tailings Dam failure in British Columbia in 2014 (5.8 million yd3 released), and the Smarco Fundao Tailings Dam failure in Brazil in 2015 (78 million yd3 released) has renewed attention to this issue. Potential risks from impounded water at mining and industrial sites originates not only from tailing dams, but also from water in process ponds and conveyance pipelines, sediment retention dams, water retention dams, mine pit lakes, and flooded underground mine workings. Conventional water retaining dams also have a record of failure. Notable examples of failure include Vajont Dam in Italy in 1963 (2,600 lives lost), Banqiao and Shimantan Dams in China in 1975 (171,000 lives lost), and Machhu-II Dam in India (10,000 lives lost). After the 1976 Teton Dam failure in Idaho, the Bureau of Reclamation (BOR) established a Dam Safety Program. By 1984 the agency developed and began using risk analysis methods. Reclamation operates and maintains an inventory of hundreds of aging dams which were designed and constructed over a period of one hundred years. Many of these facilities were constructed using engineering design and construction methods which would not be considered good practice according to present day standards. Diligent observational monitoring, detailed site investigations, and the application of risk evaluation to the BOR dam inventory has identified many deficiencies resulting in significant demands on available funding for remediation efforts. The application of risk analysis has allowed the agency to rank sites by risk. By giving priority of remedial efforts to high risk sites, significant improvements to dam safety have been achieved. BOR has also applied risk analysis to evaluate and reclaim inactive and abandoned mining and industrial sites. The application of risk analysis methods in the mining industry is not new, the methodology was transferred to the mining industry more than 15 years ago as discussed in ICOLD Bulleting 121 (ICOLD, 2001), yet failures persist. This paper is meant to convey the lessons learned from BOR’s use of risk analyses in its work on mine sites."

Jan 1, 2017

By Clemens Kuhnert

"Nickelhütte Aue GmbH is specialized in the recycling of waste materials containing non-ferrous metals. We treat nickel, copper, cobalt, vanadium, molybdenum and precious metal containing materials like spent catalysts, ashes, dusts, grindings, liquids, slurries and sludge's as long as they contain one or a combination of the above mentioned metals. In our pyrometallurgical works we produce non-ferrous metal concentrates suitable for further treatment in our hydrometallurgical plant where we refine Ni-, Cu-, Co- and V-chemicals. Our production is based on synergy effects due to the combination of pyro- and hydro-metallurgy. As an example we can mention our heat recovery system and internal recycling of by-products. Furthermore, the use of alternative fuels instead of fossil fuels contributes to the economic and environ-mentally friendly treatment system.INTRODUCTION Nickelhütte Aue GmbH (NHA) can look back on nearly 400 years of tradition as a pyrometallurgical works and recycling company. The existence since its foundation in 1635 as a blue dye works shows responsible and successful action in the past. Therefore, we see highest customer service, minimization of interferences with nature by closing material cycles and maximized health and occupational safety protection by avoiding injuries and diseases, still as our future duties. These duties are evaluated and monitored by an integrated management system that meets the standards of DIN EN ISO 9001, 14001, 50001 and BS OHSAS 18001. We commit ourselves to the observance of all juridical and customized demands. The management and the department managers perceive their model function. We require responsible action from all employees. To protect the continuity of our enterprise, we will also perform in future continuous improvement of products and their quality, as well as steady progress in the areas of environment protection, health protection and industrial safety. Equally the effectiveness and propriety of the management system is checked and developed regularly. In order to obtain the objectives resulting from this policy, our company determines activities and measures by involving all employees."

Jan 1, 2017

By A. Navarra, F. Mucciardi, H. Marambio, R. Parra, F. Oyarzún

"Discrete event simulation (DES) is an appropriate framework for the plant-wide analysis of copper smelters. These smelters apply a common set of chemical reactions: copper-iron sulfides are blasted with oxygen-enriched air, sending the iron into a slag phase and the sulfur into the offgas. Moreover, conventional copper smelters exhibit similar operational dynamics: a smelting furnace operates continually, feeding into an alternating set of converters that produce batches of blister copper. The thermochemical and operational commonalities of copper smelters are integrated within the DES framework. This serves as a common basis to begin evaluating the system dynamics of individual smelters. For complex problems, the simulation framework should be developed in phases, incorporating feedback from different personnel who have complementary perspectives. Sample computations are provided in this paper based on the Hernán Videla Lira smelter, whose production is constrained by meteorological conditions. IntroductionWorld copper production is approximately 18.5 million t/y (Brininstool, 2015), worth $80 billion a year. Out of this total, 75 percent comes from the pyrometallurgical processing of sulfide minerals (Fig. 1), which occurs in copper smelters. The remaining 25 percent is from the hydrometallurgical treatment of oxides and complex ores (Rotuska and Chmielewski, 2008), which uses solvent extraction and electrowinning.The current paper describes the pyrometallurgical processing, recognizing that the underlying thermodynamics and kinetics are well known (Degterov and Pelton, 1999), with the notable exception of minor element transport, such as arsenic (As), antimony (Sb), bismuth (Bi), silver (Ag), gold (Au). The latter is an ongoing area of research, as smelters are faced with increasingly complex ores (Devia, Wilkomirsky and Parra, 2012; Swinbourne and Kho, 2012). This paper focuses on the system dynamics of copper smelter operations, which has received considerably less attention than the chemical thermodynamics and kinetics.Smelter engineers and managers may contribute to the sustainability of their plant by improving their understanding of operational system dynamics. Indeed, we have prompted smelter improvement projects (Navarra, 2016; Navarra et al., 2016; Navarra and Mendoza, 2013) simply by adapting methodologies that are commonly used in other sectors. These previous works incorporate principles from computer-integrated manufacturing (Groover, 2000) and theory of constraints (Dettmer, 2007), featuring the use of discrete event simulation (DES)."

Jan 1, 2017

By Z. Scopa, E. Tarshizi, R. Setterlind, L. Frost, R. Livernois

"THE MINES OF THE FUTURE The mines of the future present a host of challenges, which may appear exciting or daunting depending on one’s perspective. Whether some sectors of the public recognize it or not, the demand for raw resources is not going away any time soon. In fact, it is rising as global population grows, urbanizes and attempts to steadily increase quality of life. Yes, at the same time that much of the highly developed world is calling for greener goods, reduced consumption, and cleaner production, in other areas there are cries for clean water and sanitation, consistent energy supply, access to health care and education, personal security, and support for basic human rights. The balancing act for sustainable development of our global society is indeed precarious, and the mining community is necessarily a key player. Fortunately, many industry members have accepted this role and the responsibility to provide leadership and a solid foundation for progress. Looking ahead, we need new generations of leaders, many of whom will be mine engineers, which are ready to tackle all sorts of complex problems. There are tremendous needs just for technological innovations. Increasingly tough deposits will require that we continue to expand scale toward “super” pits and “deep” underground mining fully develop unconventional recovery techniques like in-situ leaching and gasification or deep-sea extraction, and seriously consider off-earth endeavors. Such work will take entirely autonomous equipment; novel separations, processing and recycling methods; and systems that can withstand extreme physical conditions – just to name a few. It will also take a level of systems integration never-before seen in our field, complete with big data issues, sophisticated analytics and modeling efforts, and cyber-security challenges. Moreover, increasingly complex environmental problems will require creative solutions. Addressing issues like pollution control across multiple media, emerging contaminants, optimal management of wastes, selective mining, and shared use of resources between mine operations and surrounding communities and ecosystems are among top priorities. Really, a complete paradigm shift must occur, such that our focus is on overall improvement of environmental conditions, rather than minimization of impacts. A similar shift will be required in the social realm. How can we make miners safer and healthier on-site and off? How can we contribute to communities such that they are better off, now and long-term, for having a mine next door? How can we help transform artisanal mining practices to also contribute to sustainable development? How can our work be a factor in increasing economic and political stability? How can we improve the public understanding of raw resources and the need for mining enterprises?"

Jan 1, 2017

By Sara Moshfeghi, Seyyed Majdeddin Mir Mohammad Hosseini, Abolfazl Eslami

"Due to variety of current pile bearing capacity methods based on the cone penetration test (CPT), for optimum design, it is necessary to evaluate the performance of such methods in different geotechnical conditions. Geotechnical databases including piling and in-situ testing records have been recognized as useful tools for analysis, design and economical construction. In order to evaluate pile bearing capacity methods, AUT-CPT&Pile database has been compiled including 450 full scale pile load tests and CPT sounding records. This database consists of different pile types with a relatively wide range of geometries and various soil conditions. Forty three records of piles driven in sand deposits were then employed to evaluate effects of ultimate capacity interpretation criteria from load displacement diagrams. The Davisson offset limit criterion, the Brinch Hansen 80% criterion and the load at the displacement of 10% of the pile diameter were compared to estimated capacities from ten CPT based design methods currently used in practice. The Brinch Hansen 80% criterion and the load at the displacement of 10% of the pile diameter lead to reasonable results, the Brinch Hansen 80% criterion showed less scatter. For evaluating the accuracy and the precision of CPT-based methods, the results were compared to estimated capacities. Results of comparison indicate that the CPT-based methods mainly predict the pile capacity withreasonable accuracy.INTRODUCTIONAmong the different approaches of estimating the pile bearing capacity, in-situ tests, especially, the cone penetration test (CPT) are favored due to the cone similarities with piles in modes of installation as well as fast and continuous profiling. This trend is practically well established where deep foundations are to be constructed in soft to medium subsoil deposits (Eslami and Fellenius, 1997; Mayne and Niazi, 2009).Employing different design methods results in a wide range of values which complicates the selection of an appropriate one to determine the pile bearing capacity. Several studies by Briuad and Tucker (1988), Eslami and Fellenius (1997), Abu Farsakh and Titi (2004), Schneider et al. (2008) and Eslami et al. (2011) confirm disparity of different design methods predictions. Thus, for optimum design, it is necessary to evaluate and compare the performance of current methods.Geotechnical databases are known as helpful tools in research and practical applications for optimizing analysis and design and are mainly used for management and interpretation of data, evaluation of design methods, calibrating LRFD or ASD design factors, etc. Pile lateral and axial load tests are examples of databases in geotechnical engineering. A summary of several CPT and pile load test databases is presented in Table 1."

Jan 1, 2017

By Gautam Benerjee, Veera Reddy Boothukuri, Bhattacharjee Ram Madhav, Panigrahi Durga Charan

"India’s tryst with mechanized longwall coal mining started with the introduction of the first self-advancing powered support longwall (PSLW) face at Moonidih Colliery of Jharia Coalfield in 1978 and at Godavarikhani (GDK)7 Incline of Singareni Collieries Company Limited (SCCL) in 1983. During the last 37 years, about 30 longwall units in Coal India, Ltd., (CIL) and 10 longwall units in SCCL have been introduced with powered roof supports of varying capacity, ranging from 280 to 800 tonnes, in many mines in India under varying geological and geotechnical conditions. The majority of the longwall faces in India have been worked under relatively shallow cover (up to 200m), and significant strata control problems have been encountered due to poor caveability of the roof, inadequate capacity of the supports, a lack of knowledge on longwall caving mechanisms, less than adequate strata monitoring systems, and the non-availability of quality spare parts, etc. This has resulted in structural damage to supports and increased downtime of the equipment, thereby making longwall mining in India a case of technology failure. Energy demand for a developing country like India with a population of 1.2 billion is huge, and the thrust on increasing coal production continues. However, the share of coal production from underground mines in India continues to decline (current share is around 6%) because of absence of successful mass production technology in underground coal mining. Under this backdrop, a high-capacity longwall with state-of-the-art technology was introduced in 2014 at Adriyala Longwall Project (ALP) of SCCL for the first time in Indian Coal Mining Industry. The first longwall panel (LWP) has been completed successfully. This paper highlights the major geotechnical challenges encountered during development of the longwall gate roads due to the presence of two overlying clay bands, significant in-situ horizontal stresses and the experience of using rigid (welded) steel wire mesh with resin-anchored roof bolts. Efforts have been made to analyze longwall weighting and caving behavior, such as main and periodic weightings, the effect of front and side abutment pressures, and the behavior of gate roadway support systems under immediate friable weak roof with overlying massive sandstone."

Jan 1, 2017

By J. R. Schafler, J. L. Brinkman

"The US coal mining industry has suffered a recent decline in profits caused by a combination of decline in commodity demand and more restrictive government regulation, forcing coal mining companies to cease production in numerous mines. A 40% decrease in the total number of coal mines occurred from 1994 to 2000. The number of mines remained relatively constant until 2008 when a change of government sparked a series of new environmental regulations which have contributed to another 15% decrease from 2008 to 2016. In contrast, production has only decreased by 3%, increasing from 1994 to 2008, and then decreasing since 2008. However, this value is skewed by large increases in sub-bituminous coal production and decreases in other coal ranks. Several aspects assist in executive decisions on mine longevity and economic worth. Studies of open source mine data collected by mandated government surveys coupled with commodity history can be used to find relationships between mine closures and these elements, which include statistics on production tonnage, seam height, coal rank, etc. This paper looks at coal mining trends since 1994 by comparing mine, market, and regulation factors that may influence mine closure. INTRODUCTION The US coal mining industry is currently experiencing a decline in both demand and commodity price while facing implementation of more stringent air and water pollution regulations. Company profits have decreased significantly, forcing several major companies to declare bankruptcy. The industry was required to adapt to survive. Many of these companies have adjusted by abandoning mines; the last two decades have seen a drastic decrease in the number of mines. To discover the primary causes of this downturn, three major aspects must be studied: properties of abandoned mines, commodity history, and regulatory impact. TRENDS SINCE 1994 Each year, US coal mines are required to submit data on a wide variety of categories to the Mine Safety and Health Administration (MSHA) and the US Energy Information Administration (EIA). This data includes administrative records, production values, and information regarding the attributes of the mined material and the mine itself. Each year since 1996, EIA has released a report summarizing the data from two years prior. Additionally, MSHA maintains a database containing a collection of all the most current data. These resources are the primary sources for the following figures."

Jan 1, 2017

By Andrea Koschinsky, Luise Heinrich, Stefan Gößling-Reisemann

"Germany, like several other countries, has entered a contract with the International Seabed Authority (ISA) to explore the prospects of commercial manganese nodule mining in the Clarion-Clipperton Zone (CCZ). Ensuring a maximally sustainable deep-sea mining operation requires a thorough understanding of the environmental impacts associated with every step of the mining process from the extraction of the nodules at the seafloor to the refinery on land. Against this background, the project presented here applies a combination of scenario-building and life cycle assessment (LCA) to assess and evaluate the sustainability performance of the individual process steps as well as the entire mining operation.Life cycle assessment (LCA) is a comprehensive methodological framework that allows the identification and quantification of impacts occurring during a products life-cycle, as well as the analysis and evaluation of their contribution to pre-defined impact categories, such as climate change, acidification and toxicity (Rebitzer et al., 2004). Until now, LCAs with a focus on raw material extraction have almost exclusively been applied to terrestrial processes. Noteworthy exceptions are offshore drilling, offshore wind farms and ocean fishing. Hence, the first part of the project is to investigate in how far LCA can be applied to deep-sea settings and if and in what way it could be adapted to be used in a deep-sea mining context."

Jan 1, 2017

By B. Berg, J. Stephenson, J. Mansanti, C. Nyikos

"Intrepid Potash, Inc.’s Carlsbad East facility has refined sylvite and produced muriate of potash (MOP) since 1965. In addition to MOP, Intrepid Potash began recovering the mineral langbeinite from a mixed ore reserve in 2005. In 2011 a new langbeinite recovery process for the coarse (+850 micron) size fraction was constructed to enhance the overall langbeinite recovery. Based on the limited mixed ore reserve and an abundance of langbeinite ore reserves the transition of the East plant to a langbeinite only facility was targeted for 2021. Due to a decreasing grade of the mixed ore reserve, declining sales pricing, and high sylvite operating costs a strategic decision was made to accelerate this transition into 2016. To enable a successful transition, a fines recovery system needed to be developed, constructed and implemented. This paper describes the advancement of langbeinite processing at Intrepid Potash and the planning, development and successful execution of the transition to a langbeinite only operation. BACKGROUND Langbeinite (K2SO4·2MgSO4) is a double salt containing potassium sulfate (K2SO4) and magnesium sulfate (MgSO4). It is used as fertilizer and in the industry is described as Sulfate of Potash Magnesia. It is attractive as a specialty fertilizer and in addition to containing a ready source of a primary nutrient potassium, it also provides two secondary essential nutrients, magnesium and sulfur. It is especially attractive for chloride sensitive crops. Langbeinite has a specific gravity of 2.8, a Mohs hardness of 4.2, and is brittle thus very friable. It is the hardest of the saline minerals, and despite its relative softness on the Mohs scale can be very abrasive in process environments and in field applications, probably due to its conchoidal cleavage. Its solubility at 240 g/l is less than the solubility of sylvite (KCl) or halite (NaCl) and due to even slower relative dissolution kinetics washing with cold water has been a common practice for upgrading langbeinite ores. The solubilization/crystallization relationship for langbeinite is different from the majority of other evaporite minerals in that once langbeinite is solubilized it does not form langbeinite again. Instead it gives up one mole of magnesium sulfate, takes on various waters of hydration and precipitates out as either schoenite (K2SO4·MgSO4·6H2O) or leonite (K2SO4·MgSO4·4H2O) depending on temperature. Due to its partial solubility and phase transitions at its surface when exposed to moisture, there is strong cohesion between wetted particles; the resulting stickiness of the upgraded products can create significant materials handling issues unless processed in slurry form or at relatively low moisture levels. Langbeinite has been produced commercially from two locations, the Kalush and Stebnik regions in the Cartpathian Mountains of former Poland and now the Ukraine and from the Permian Basin in New Mexico (Garrett, 1996; Smith 1949). Current production is from two operators in the U.S., Mosaic and Intrepid Potash."

Jan 1, 2017

By Stephen C. Tadolini, Robert Hawker, Peter Mills, Colin Grubb, Tom Meikle

"In unfavorable strata conditions, it is often necessary to install additional long tendon support as part of a primary support cycle. Although these support systems provide the required additional stability to the roadway installation does have a significant effect on the rate of development. To overcome the slow cure time of Portland cement-type grouts, the use of two component resin systems, such as polyurethanes and urea silicates, have become favorable. However, concerns over low modulus and creep properties has led to the development of a two-component grouting medium that displays the properties of traditional cable grouting materials with the rapid reaction times of pumpable resin systems. This paper describes product testing, application, surface trials, underground trials, and full-scale applications of the Tekthix System in a dynamic underground environment. INTRODUCTION Single-component cement grouts have been used to anchor long tendon supports for many years. They range from high- to low-slump Portland cement and can be slow-setting to fast-setting grouts. However, current cement grouting systems, which includes the grout and equipment, have some disadvantages: 1. Low-slump grouts require pumps that can handle a thick, high-viscosity grout, so choice of pumps is limited. 2. Pumping distance is limited with current cable bolt grout pumps; operators often tend to add water to allow pumping long distance, which adversely impacts the quality and strength of the material. 3. Fast-setting grouts tend to cause issues with pump and line blockages due to the reduced working life of these single-component materials."

Jan 1, 2017

By E. Kumar, L. A. Kumar

"A methodology is proposed to develop an optimization model to understand the impact of transporting minerals, from mines to the final destination, on air quality. Recently, there has been increasing concern about the combined effects of multiple activities over many years, and the regional environmental changes brought about by a single project. Environmental issues in the iron ore industry have highlighted the need to broaden the cumulative impact assessment. In this study, we simulated the optimal routes and quantity of materials needed to meet the destination plant demand based upon environment constraints (level of air pollution), as well as the cost of transportation and availability of materials. Multiple scenarios were developed to analyse the effects of changes in routes, alternative transport system (or multi-modal split), traffic congestion, and the cumulative impacts on air quality. The air quality impact zones of the study area were demarcated using a GIS technique. The expected outcome of the study is the selection of a suitable transport system for a particular site with the least impact on air quality, including the transportation route, relative to the minimum cost of transportation of the minerals from the mines to their final destination. The proposed methodology is evaluated with a case study. IntroductionIn India, the process of environmental impact assessment (EIA) has been focused primarily on the local impacts of projects, without considering regional environmental effects. Environmental clearances for proposed projects are based on reports of local impacts. However, any developmental project poses a potential risk to the environment as a whole, and not just in the immediate vicinity of the project. Recently, there has been increased concern about the combined effects of multiple activities over many years—the regional environmental changes due to development of a single project (Dutta, Mahatha, and De, 2004). Environmental issues throughout the country, particularly in the iron ore industry, have emphasized the need to broaden the analysis to include the combined impacts, or those forecast for a proposed region, on an existing environment. The most significant adverse environmental consequences of iron ore transportation are the deterioration of biodiversity and air quality (Kumar and Ajay, 2015)."

Jan 1, 2017

By Martin McKinnon, Guy Reed, Russell Frith

"It is arguable that the development of reinforcing roof bolting systems has largely stagnated in recent times, primarily due to the prevailing industry view that few, if any, further improvements can be made to what currently exists. However, this paper contends that reinforcing roof bolting systems can be further refined by considering both the specific manner by which horizontally bedded roof strata loses its natural self-supporting ability and the specific means by which reinforcing roof bolts act to promote or retain this natural self-supporting ability. The Australian coal industry insists on minimising bolt-hole diameter to maximise load transfer and on targeting full-encapsulation by any means necessary. This has led to a significant, albeit unintended, consequence in terms of overall roof bolting effectiveness, namely increased resin pressures during bolt installation and the associated potential for opening bedding planes that may have, otherwise, remained closed during the bolt installation process. Given that the natural self-supporting ability of roof strata is strongly linked to whether bedding planes are open or closed, logically, minimising resin pressures should be a significant benefit. This paper focuses primarily on three key issues that relate directly to the function of the roof bolting system itself: (i) the importance of proper resin mixing in the context of maximising load transfer strength and stiffness, (ii) the importance of minimising resin pressures developed during bolt installation, and (iii) the importance of maximising the effectiveness of the available bolt pre-tension. All mine operators should be invested in improving the individual effectiveness of each installed roof bolt, even by relatively small incremental amounts, so this is an important topic for discussion within the mining community."

Jan 1, 2017