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By B. M. Eiter, J. Hrica, D. R. Willmer

"Mineworkers are routinely tasked with making critically important decisions about whether or not a hazard presents an imminent danger. Researchers from the National Institute for Occupational Safety and Health (NIOSH) collected formative data to investigate mine safety professional perspectives on workplace examinations, which revealed a potential gap in how mineworkers are assessing risk. During interviews, participants indicated having processes in place for what should be done once an imminent danger situation is identified. Critically, however, they report having no systematic methodology for mineworkers to use to determine if a hazard is considered imminent danger. While this is important for all imminent danger situations (e.g., failure to lockout/tagout), it is especially important for those situations that are not immediately recognizable as imminent danger. In this paper, we identify and describe, three distinct categories of imminent danger complexity and discuss potential steps that could lead to improved identification of imminent danger situations. Finally, we identify potential practices to incorporate into risk management efforts, including feedback, communication, and specialized training to increase awareness of imminent danger situations. INTRODUCTION In recent years, the metal and nonmetal (M/NM) mining sector, as categorized by MSHA, experienced an increase in the number of fatalities occurring at mine sites. From 2013 to 2015, 69 mineworkers were fatally injured; that is twice the number of fatalities that occurred in each of the previous two years (MSHA, 2015a). As a way to address this increase, the Mine Safety and Health Administration (MSHA) issued a program policy letter (P15-IV-01) suggesting that “miners would benefit from rigorous workplace examinations conducted by experienced and trained examiners (MSHA 2015b).” The goal of workplace examinations is to find hazards in the field and mitigate them before they cause injury or death to mineworkers. While it is important to identify all hazards in the workplace, it is critically important to identify those hazards that are considered imminent danger because they require an immediate response to avoid a severe or even fatal injury."

Jan 1, 2018

By L. Muhr, Y. -T. Tang, M. -O. Simonnot, B. Laubie, R. -L. Qui, Z. Chour

"Agromining aims at recovering metals from different secondary resources with hyperaccumulating plants. These natural plants can selectively concentrate metals at very high level and can be transformed to produce commercial compounds. The classical strategy to recover metals from hyperaccumulator plants is based on hydrometallurgy. It consists of: i) burning the plant to obtain ash, which is a very rich bio-ore without organic matter, ii) transferring the target element(s) into aqueous solution by acid leaching and iii) purifying the leach liquor to obtain the target element(s) in the desired form. This method has enabled us to obtain nickel salts, nickel oxide, zinc and cadmium from different plants. However, it is not possible to apply this approach to recover rare earth elements (REEs) from the fern D. dichotoma, growing on mine tailings in South China. Actually, this plant is very rich in silicon: plant burning gives an amorphous ash, very stable despite severe leaching conditions. Therefore, the strategy has been changed and processes are currently developed to extract REEs by direct leaching of the biomass, without burning the plant. Several conditions (i.e. leaching solutions) have been investigated, showing that a good extraction yield was obtained with HNO3 0.5 N (around 84%). This yield was increased to 99% by adding a complexing resin into the leaching solution. After two-steps of elution, results have shown that is possible to recover 75% of the REEs at 81% purity.INTRODUCTION The demand of rare earth elements (REEs) (including 15 lanthanides, yttrium and scandium) has been growing sharply over the past years, because of their industrial applications. REEs are essential elements for emerging technologies, and are used for example in permanent magnets, lamp phosphors or rechargeable batteries. China is the main producer, and the market supply became tense in 2010 when this country decided to limit exports of these elements. Exploitable mineral resources, as well as REE separation capacity are concentrated in a few countries (e.g. USA, Australia, Malaysia, France), which increases the supply risk. Therefore, these elements are considered as critical raw materials (CRM) for many countries and especially for EU (Fortier and Gambogi, 2017)."

Jan 1, 2018

By A. Javadi

"Our recent studies revealed that the sulfide minerals in contact with water during grinding produced hydrogen peroxide (H2O2) where the amount of H2O2 production by the minerals found to be in the order of pyrite > chalcopyrite > sphalerite > galena. The H2O2 effect on the oxidation of pulp components and its influence on the concentrate grade and recovery in flotation have been studied and the results have been presented and discussed in this paper. Studies have also been carried out to build correlation between percentage of pyrite in the concentrate, grinding conditions and concentration of OH•/H2O2 in the pulp and as well of controlling the formation of these species through known chemical means for depressing the generation of the oxidant. Flotation tests using a complex sulfide ore with the same reagent scheme that is being used at Bama concentrator in Iran but with the addition i) Na2S reductant and ii) inorganic (EDTA) and organic (TETA) surface modifiers, during grinding stage have been performed to judge the beneficial or detrimental role of H2O2 on the selective flotation of sulfides. The results demonstrate that the selectivity of metal sulfides against pyrite increases with increasing generation of H2O2 in the pulp liquid.INTRODUCTIONOur recent studies have illustrated the formation of hydrogen peroxide (H2O2) by metal-sulphides during grinding in the presence and absence of oxygen (Javadi Nooshabadi & Hanumantha Rao, 2013a; Javadi Nooshabadi & Hanumantha Rao, 2013b; Javadi Nooshabadi & Hanumantha Rao, 2013c; Javadi Nooshabadi & Hanumantha Rao, 2014). In the absence of oxygen, it was found that pyrite surface is catalytically active and able to breakdown water molecules to form OH• free radical and thereby deriving oxygen in the formation of H2O2 from water molecules. The in-situ formation of H2O2 and its influence on sulphide flotation has not been addressed yet. The presence of strong H2O2 oxidant in the pulp liquid and its selective oxidation of pyrite would be beneficial in depressing pyrite flotation. Therefore, it is important to build correlation between percentage of pyrite in the concentrate, grinding conditions and concentration of OH•/H2O2 in the pulp as well as to study possible ways of flexibly controlling the formation of these species through known chemical means for depressing the generation of the oxidant."

Jan 1, 2018

By G. Morin, F. Chiesa, B. Tougas, B. Duchesne, Jocelyn Baril, N. Giguère

"An aluminum A356 compressor impeller was sand cast using the Low Pressure technique. The casting was limited in size (170 mm in diameter, 1.2 kg in weight) and very intricate in shape thus making 3D mold printing particularly favorable; indeed, producing this part by the traditional pattern-core box route would involve mounting 12 cores inside the mold while stringent dimensional tolerances are required as the impeller blades are only 2 mm thick. Consequently the molds were produce on the X-One MFlex printer of Quebec Metallurgy Center - CMQ. A dozen castings were produced with different casting temperatures and filling times so that it was possible to assess under which conditions complete filling of the mold cavity would be achieved. Filling and solidification modeling allowed predicting misruns and metallurgical properties inside the A356 (AlSi7Mg04) casting.INTRODUCTION Recent advancements in additive manufacturing enable foundries to produce molds without the tooling (pattern and core boxes) necessary when conventional technology is used (Eyad, 2016). This is particularly advantageous when dealing with intricate shapes and/or when a limited number of parts must be produced within a few days rather than in 5 weeks. An additional advantage is gained when producing prototypes (Johnson, 2016) as changes are much less costly and time consuming when made on a numerical 3D drawing rather than on patterns and core boxes. 3D printing is normally economical for a small number of parts; however, if the part is not too big and very intricate in shape such as the part that will be studied in the present work, 3D printing can be economical even for an important number of castings to be produced. On the other hand, low pressure casting is a high integrity casting process in which the mold cavity is filled from the bottom via a transfer tube in which the liquid aluminum rises under the pressure applied at the surface of the melt as illustrated in Figure 1. The filling can thus be precisely controlled, eliminating the turbulence created when the mold is filled from the top (gravity casting). Also, the pressure applied on the melt during solidification results in excellent feeding of the casting when conditions of directional solidification are met. In the present work, the compressor impeller shown in Figure 2 will be sand cast by low pressure."

Jan 1, 2018

By Alexey Musatov, Georgy Cherkashov

Based on geochronological data it was confirmed that hydrothermal discharge has an episodic character: active and inactive periods of the seafloor massive sulfides (SMS) formation alternate (Cherkashov et al., 2017). There is an assumption of correlation of the periods of magmatic and hydrothermal activity with the stages of glaciation (Lund et al., 2016). During the cold periods, the level of the ocean was reduced from 70 to 150 m depending on the glaciation scale (Spratt, Lisiecki, 2016). As a result, the hydrospheric pressure on the upper mantle decreased and could provide increased magmatic and hydrothermal activity (Lund, Asimow, 2011). This assumption is confirmed by the correlation of warming and cooling stages with increasing of hydrothermal input to the bottom sediment near hydrothermal fields. According to data (Lund et al., 2014, 2016; Middleton et al., 2015) the peaks of hydrothermal activity, expressed in the layers of metalliferous sediments at the East Pacific Rise and the Mid-Atlantic Ridge, roughly correspond to the last two periods of cooling (20 and 60 ka). To test this hypothesis, we tried to compare the sequence of warm and cold periods in the Pleistocene with the dating of SMS reflecting the periods of hydrothermal activity. Results SMS samples were obtained from 12 sites within the Russian Exploration Area at the MAR segment 12-20°N. The results of dating 198 samples by the 230Th/U method demonstrated the absence of correlation between hydrothermal activity periods in different hydrothermal fields (Cherkashov et al., 2017). It was proposed that each field has its own evolutions scenario. Considering this point, only the oldest SMS dating for each field which fixed the beginning of hydrothermal activity was selected for comparison with the cold/warming periods.

Jan 1, 2018

By Cees van Rhee, Rudy Helmons

INTRODUCTION Seafloor Massive Sulphides are typically found near the oceanic ridges at larger water depths (>1km). The physical properties of SMS, as shown in table 1, are comparable to the properties of weak rock. One of the technical challenges to enable extraction from these locations is the cutting or excavation process. Experiments have shown that the energy needed to excavate the material may increase with water depth (Alvarez Grima et al. 2015). Besides that, it is demonstrated that rock that fails brittle in atmospheric conditions can fail more or less in a plastic fashion when present in a high pressure environment, as would be the case at large water depths. The goal of this research is to identify the physics of the cutting process and to develop this into a model in which the effect of hydrostatic and pore pressures is included. The cutting of rock is initiated by pressing a tool into the rock. As a result, at the tip of the tool a high compressive pressure occurs, which leads to the formation of a crushed zone. Depending on the shape of the tool and the cutting depth, shear failures might emanate from the crushed zone, which will eventually expand as tensile fractures that can reach to the free rock surface. Through this process intact rock will be disintegrated to a granular medium. For an overview of the process (figure 1). Additionally, the presence of water in the pores of and surrounding the rock influences the cutting process through drainage effects. The most relevant effects are weakening when compaction and strengthening when dilation occurs in shearing and tension. Deformation of the rock causes the pore volume to change, resulting in a under or over pressure. As a result, the pore fluid needs to flow. The magnitude of the potential under pressure is limited through cavitation of the pore fluid, limiting further reduction of the pore pressure (figure 2). The drainage effects cause the rock cutting process in a submerged environment to show a stronger dependency of both the hydrostatic pressure as well as the deformation rate (figure 3).

Jan 1, 2018

By J. Gallegos, R. Faber, T. Cox

"An innovative method to reduce acid rock drainage (ARD) and sediment loading of a recreational lake was used in the Red River watershed in northern New Mexico. The Red River drains a mining district that contains multiple naturally occurring hydrothermal alteration zones that release ARD and sediment to the river during episodic summer rain storms. A lake is near the mouth of the watershed and is filled with water from the river through a sluice gate and diversion. An automated actuator was installed on the sluice gate to close when the river is impacted by high-suspended sediment. Water quality probes were installed at the sluice gate to monitor the river water for turbidity, specific conductivity and water depth. If high turbidity is measured, the sluice gate closes automatically. Remote access is setup with a computer view screen to review the real-time system status. Once the turbidity drops below a threshold, the sluice gate is reopened remotely. The automated sluice gate has successfully reduced the amount of ARD and suspended sediment entering the lake. This reduction has resulted in an improved aquatic habitat for the fishery and benthic macroinvertebrate community. BACKGROUND The Red River is located within the Sangre De Cristo Mountain Range in northern New Mexico. The river drains an area of approximately 190 square miles and spans elevations from 6,600 feet at its confluence with the Rio Grande to its headwaters near 12,000 feet (Figure 1). The river generally flows to the west along most if its length.The Red River watershed includes several hydrothermal alteration zones. The alteration zones were created by intrusion of high-silica granites and subvolcanic porphyries, with associated hydrothermal fluids, into the volcanic rocks of the Questa Caldera. The hydrothermal alteration is also responsible for the molybdenum deposits in the area. Rapid chemical weathering and physical erosion of pyrite-rich hydrothermally altered rocks has resulted in the formation of alteration scars. The alteration scars are characterized by steep, erodible slopes with little vegetation and incised gullies. Debris fans from the drainages containing active alteration scars have formed and typically consist of poorly sorted sand and gravel that is distinctly pale yellow in color. Some of the more prominent scars are located in the Hansen, Straight and Hottentot Creek drainages downstream of the town of Red River."

Jan 1, 2018

By I. Casasbuenas, K. A. Nguyen, E. I. Ngoma, H. Kim, D. Borja, J. H. Park, R. A. Silva, S. Choi

"This study aimed to determine the optimum operating parameters of a continuous bioleaching system to leach arsenic (As) from mine tailings using a mixed mesophilic bacterial culture. The microbial consortium, previously adapted for effective growth at high pulp density and metal concentrations, was mainly composed of Leptospirillum ferriphilum, and Acidithiobacillus caldus. The mine tailings, collected from the Janggun mine (South Korea) contained 11% (w/w) of As. The tests were performed in a laboratory-scale unit composed of three reactors connected in series following a cascade configuration. Agitation speed, air supply, solid concentration, residence time and temperature were systematically optimized by assessing the leaching activity. Several parameters were monitored on a daily basis, including the As released into solution, iron oxidation rates, pH, cell concentration, dissolved oxygen and redox potential. Overall, improvement of oxygen transfer, by optimizing the agitation speed and air supply, presented the most tangible impact on the leaching performance. The highest As leaching efficiency observed in this study was 82%, which supports the feasibility of the process. INTRODUCTION Worldwide, around of 65 billion tons of mine tailings are produced every year (Jones & Boger, 2012). These materials comprise the waste minerals produced after ore beneficiation. Mine tailings usually contain heavy metals (e.g., Cobalt (Co), Lead (Pb), Zinc (Zn) and Arsenic (As) (Falagán, Grail, & Johnson, 2016; Nguyen, Lee, Park, & Lee, 2014). The exposure of these materials to the environment can produce serious health damage and environmental degradation (Martin, Dowling, Pearce, Sillitoe, & Florentine, 2014). Mine tailings management represents a major issue in South Korea. There are more than 1,000 abandoned mines containing stockpiled mine tailings within the territory (Choi, Park, Hong, Park, & Kim, 2013; Kim, Kim, Ahn, Ko, & Lee, 2005; Lee, Lee, & Kim, 1998). These tailings comprise high concentration of arsenic. Therefore, the Korean Government has directed its efforts to developing eco-friendly technologies, for the arsenic detoxification of mine tailings Continuous bioleaching is explored as a remediation technology (Borja et al., 2016). The present study aimed to develop a mixed mesophilic bacterial culture for optimal growth at high metal and solid concentration; and optimize the operating conditions of a continuous bioleaching unit. This investigation forms part of a larger study aimed to develop a bioleaching technique to treat Janggun mine tailings (Borja et al., 2017; Ngoma et al., 2017)."

Jan 1, 2018

By A. L. Miller, A. J. Chambers, P. R. Griffiths, D. A. Parks

"Diesel engines are one of the primary contributors to the presence of nano and ultrafine aerosols in ambient air and occupational environments. Exposure to diesel emissions has been shown to contribute to various adverse health outcomes of the pulmonary system and cardiovascular system. Currently diesel emissions in the workplace are monitored by way of collecting the aerosol onto filters, which are then sent to a lab for thermal-optical analysis using the NIOSH 5040 method, which measures elemental and organic carbon explicitly. This process can take days or even weeks, and workers can potentially be exposed to excessive levels of diesel particulate matter (DPM) before the problem is identified. To remedy this, researchers from the National Institute for Occupational Safety and Health (NIOSH) are seeking to develop a field-portable method for measuring elemental and organic carbon in DPM aerosols. In the current study, we investigated the use of Fourier transform mid-infrared (FT-IR) spectrometry, which lends itself more readily to implementation in a real-time system than do the thermal-optical analysis methods. We have demonstrated a method for measuring organic and elemental carbon in DPM for a broad range of organic carbon (OC) to elemental carbon (EC) ratios (from 50.3 to 0.8). The ability to handle a wide range of OC to EC ratios is critical given the evolving diesel technology. INTRODUCTION Respiratory illnesses are common in mining industry workers [1] and exposures to toxic aerosols such as DPM can result in serious respiratory illness [2]. Health studies show a correlation between workplace exposure to diesel exhaust and an increased risk of lung cancer [3-8]. The International Agency for Research on Cancer (IARC) has characterized diesel exhaust as a human carcinogen [9], and similar classifications have been made by the World Health Organization and the California Air Resource Board. A recent study [10] suggests that the risk of lung cancer is approximately three times greater for heavily exposed workers. When compared to other aerosols in the mine environment, the settling time of DPM is significantly longer than that of dust due to their small particle size (typically < 1 µm) [11]. Additionally, submicron particles (such as DPM) are deposited in the lungs much more efficiently than their larger counterparts such as dust [12]. Previous studies focusing on particle morphology [13] show that the largest mass contributor to lung disease in mining is elemental carbon, which provides a solid core onto which hydrocarbons are adsorbed. In accord with those findings the Mine Safety and Health Administration (MSHA) decided on submicron total carbon as a surrogate for monitoring diesel particulate matter in the mining environment."

Jan 1, 2018

By Xinzhi (Thomas) Du

"In order to monitor the overburden strata deformation over a longwall mining area in the Pittsburgh Coal Seam, three boreholes were drilled across the longwall panel. Each borehole employed multiple-point borehole extensometers (MBE) to monitor overburden strata movement during and after the longwall face passed under the study area. The longwall face in the study area was 1,428 ft wide and 4,000 ft long. The average mining height was about 7 ft. The overburden depth ranged from 550 ft to 650 ft with an average of 600 ft. The final extensometer readings indicated that overburden strata initially showed sign of movement when the longwall face was 700 ft inby the MBE. The rate of strata movement accelerated when the face was 300 ft inby MBE. When the face was directly under MBE, a sudden anchor displacement occurred, indicating rapid strata movement once under-mined gob. The readings showed insignificant strata movement after the longwall face was 400–700 ft outby MBE.INTRODUCTIONThe longwall mining method is an efficient mining method of underground mining. Surface and subsurface strata are inevitably disturbed above the longwall mined out gob. Figure 1 shows the four zones of disturbance in the overburden strata in response to longwall mining.A longwall shear cuts the coal seam and allows the immediate roof strata to cave into irregular blocky material to fill the void. This is called the caved zone. The caved zone extends from the mining horizon to six or eight times the mining height, depending on the bulk factor of each caving strata layer. The fractured zone is located above the caved zone, in which the strata breaks into regular blocks by vertical or sub-vertical fractures caused by bending forces due to the weight of the underlying strata. The surface soil and rock crack zone extends to approximately 50 ft below the surface. The surface cracking is caused by downward movement of the surface. Between the fractured zone and surface crack zone is the continuous deformation zone. The strata in this zone deforms gently without causing any major cracks that extend long enough to cut through the thickness of the strata, as in the fractured zone (Peng, 2006).The objective of this project is to provide fundamental rock mechanics research about overburden strata movement response to longwall-related activity. The findings aid in better understanding pillar stability, gas well subsidence management, hydraulic impacts, and numerical modeling."

Jan 1, 2018

By M. Fig, B. Treffner, J. Brune, C. Strebinger, G. Bogin, D. Pardonner

"Methane gas explosions in a longwall coal mine can originate from in or around the gob and can seriously harm nearby workers and equipment. In order to fully understand the explosion flame and pressure wave propagation in the mine, it is important to investigate methane flame propagation in confined spaces as well as flame interaction with rock rubble and other mine structures. The latter can lead to enhanced turbulence causing high-speed deflagrations and/or detonations. Researchers ignited methane-air mixtures in horizontal, cylindrical reactors that contained inserts to simulate various gob characteristics. Rock surface topology and ignition location were investigated. Results show rock surface roughness increased fluid motion, thereby increasing methane flame front propagation velocity, overall pressure rise of the explosion, and time of pressure decay. Moving the point of ignition away from the open end of the reactor resulted in an increase in peak overpressure and an overall pressure rise of the explosion. Experiments were used to validate a computational fluid dynamics (CFD) combustion model that will be incorporated into a mine-scale explosion model to simulate and predict explosion hazards of large scale methane gas deflagrations in longwall coal mines. INTRODUCTION Coal mining is an integral part to our global society with coal-fired power plants providing about 40% of our global electricity [1]. A common method of extracting coal underground is by longwall mining. Researchers and investigative reports have found that explosive gas zones of methane-air mixtures can form along the longwall face and within the longwall gob, presenting an explosion risk to nearby workers and equipment [2]. In an explosion, the resulting flame and pressure wave presents a fatal traumatic injury hazard and can cause serious damage to equipment. In order to evaluate and mitigate the explosion risks in longwall coal mining, researchers at the Colorado School of Mines are developing a coupled CFD and combustion model of a longwall coal mine. The purpose of the model will be to better predict the explosion hazards under various mine conditions in order to build stronger prevention and mitigation strategies for miners."

Jan 1, 2018

By Caibin Wu, Ali Lei, Ningning Liao, Jingsheng Ye

"The particle size distribution characteristics of ground product can influence the quality of the classification overflow and the next beneficiation indexes in an ore concentrator. Usually, the size distribution of ground product is considered to be determined by that of new ball mill feed. However, based on large amounts of data from industrial grinding circuit surveys, this paper has clearly shown that the size distribution of ground product should be determined by the size characteristics from classification underflow unless the circulating load was small, because the new feed is an important component and occupy a dominant position of mixed ore from belt feed and classification underflow. On the other hand, the correlation coefficient of the size distribution between ground product and classification underflow can be more than 0.99 when the relevance principle and its method are used. Meanwhile, their P80 value also keeps a synchronous correlation. The greater the capacity of classification underflow is, the higher the correlation of size distribution between the ground product and the mixed feed is. Furthermore, the correlation coefficient of the size distribution between ground product and classification overflow which is from primary or secondary can be 0.96. It is another discovery that the correlation coefficient is related to the type of classifier. The coefficient of size distribution of overflow and underflow from hydrocyclone is superior to that of spiral classifier, which can explain the reason why the hydrocyclone is widely used to replace the spiral classifier in concentrator.INTRODUCTION It is well knows that ball mill circuits closed with cyclones or spiral classifier such as a primary grinding circuit, a secondary grinding circuit and SAB mill have become an industry standard. Which grinding process employed will be determined by the P80 value of ground products. When the primary closed circuit ball mill or SAB that it is different throughout between the two processes was employed, a grinding fineness with -200mesh under 68% will be available. However, the secondary grinding circuit with the fineness of -200mesh above 80% can be conducted. Of course, the grinding fineness is determined by the grain size characteristics of the mineral."

Jan 1, 2018

By Stephen C. Tadolini, Anand Bhagwat

"Intrinsic supports installed in mines with limited seam or mining heights have always proven to be difficult when the required support length is longer. To date, three solutions have been used to ensure that the correct length bolt is installed to achieve the required anchorage or to maintain immediate roof material: combination bolts, milled-notch bolts, and hot-notch bolts. The combination bolts use threaded sections and couples, which can be screwed together to form the required length. The primary bolt of choice, to minimize costs and achieve the desired support, has been milled- or hot-notch rebar bolts. These notches can be placed at strategic (required) locations along the bolt axis, so the bolt can be successfully bent and straightened during the installation process. However, these notches can reduce the strength of the bolting system; special reductions are detailed in ASTM F432-13 (2013). Technical advances in steel rolling and forged heading processes have led to the development of a deformed rebar bolt termed, the BORE bolt, which stands for Bendable Oval REbar. The BORE bolt can be bent at any location and straightened during the bolt installation cycle. This support exceeds the minimum designed capacities described in ASTM F432-13 and meets the yield and tensile strength requirements of a full diameter no. 6 rebar bolt. The profile and shape also reduces the resin annulus during the installation process to enhance mixing and shreds the cartridge film to help eliminate glove fingering.INTRODUCTIONThe height or depth of competent strata material, in the immediate mine roof, can be greater than the developed mine openings heights. This is especially true in coal mine openings where 50% of the minable seams in the US are less than 50 inches (132 cm). When this scenario occurs, it can be difficult to insert steel bolts in a solid single length. Figure 1 illustrates what difficulties can be experienced when a roof bolter operator is working and supporting a thin seam coal mine. There are three viable options currently available. Lengths of the bolt can be threaded and a steel coupler can be used between the sections to reach the required depth of anchorage. These systems, called “coupled bolts,” usually require a larger diameter hole to facilitate the larger coupler diameter and can be anchored with an expansion shell, resin, or a combination of both. To ensure that the coupler will develop the tensile capacity of the bolting system, required by ASTM 432-13 Standard Specifications for Roof and Rock Bolts and Accessories (2013), the threaded bars should be completely rotated and engaged into the coupler. Premature failures can occur when the threads “strip out” if not inserted completely."

Jan 1, 2018

By R. D. Clarke, E. De Souza

"A framework for ventilation planning, with a focus on planning to the end-of-mine life, was developed for the Diavik Diamond Mine, Northwest Territories. This framework was successfully used by Diavik’s mine engineers to select a cost-effective ventilation plan that met the life-of-mine requirements. The framework achieved this result by reconciling the production plan with the ventilation plan. A set of design acceptability criteria was created and a PICK (possible, implement, challenge, kill) chart was used to quickly narrow down the generated ideas for detailed assessment and economic analysis. RÉSUMÉ Un cadre de planification de l’aérage, qui met notamment l’accent sur la planification jusqu’à la fin de vie de la mine, a été développé pour la mine de diamants Diavik. Les ingénieurs miniers de Diavik ont su mettre à profit ce cadre pour sélectionner un plan d’aérage rentable qui répondait aux exigences propres à la durée de vie de la mine. C’est en conciliant le plan de production et le plan d’aérage que cet objectif a pu être atteint. Un ensemble de critères d’acceptabilité de la conception a été créé et un tableau PICK (de l’anglais possible, implement, challenge, kill, une méthode donnant la priorité à certaines actions proposées ou à des idées visant à résoudre des problèmes) a été utilisé pour rapidement limiter les idées générées et les soumettre à une évaluation et une analyse économique détaillées.INTRODUCTION The Diavik Diamond Mine, Northwest Territories, has been an underground-only operation since 2012 and has a remaining mine life of 8 years. In the first year of underground-only operations, the production rate increased from 60 kt of ore per month to more than 160 kt of ore per month. In subsequent years, this rate was continuously increased (Table 1) because the operation went through various improvement initiatives. By the end of 2016, Diavik’s total production was 0.41 Mt (+22.8%) ahead of the 2012 budget for 2016 production."

Jan 1, 2018

By Xinyang Xu, Chen Zhang, Lixia Li, Zhitao Yuan

"Density functional theory was employed to clarify the mechanisms of the activation of a quartz surface and its collection by the flotation method at the molecular level. The calculation results indicated that hydrogen bonds on the quartz surface (1 0 1) existed in pairs while in contact with water. The simulation was carried out to investigate the different effects of Ca2+ and Ca(OH)+ on a quartz surface with hydrogen bonds, and the results suggested that Ca(OH)+ most likely adsorbed onto and activated the quartz surface. Mulliken population analysis of the external oxygen atom of the quartz surface, calcium atom of Ca(OH)+, and the oxygen atom of oleate showed that there were electron transfer and the formation of a chemical bond between Ca1-O1 and Ca1-O3, which were indicative of strong interactions between the three atoms. In addition, the –OH of the Ca(OH)+ contributed to the activation, which suggested that the Ca(OH)+ group acted as a bridge between the surfaces of oleate and quartz.INTRODUCTIONFlotation is an effective separation method in mineral processing that takes advantage of the physicochemical differences between minerals and gangue, and the properties of the mineral surfaces play a key role in this process (Liu et al. 2016, Qin et al. 2017). In the reverse flotation process of iron ore, gangues are captured by cationic or anionic collectors and floated with air-bubbles as tailings, and the pre-depressed iron oxide minerals are left at the bottom as concentrates (Lima et al. 2013, Yianatos et al. 2015, Zhu et al. 2015). Quartz (SiO2) is one of the major gangues of hematite ores and cannot be easily removed. It is a naturally hydrophilic mineral, in which silicon is the cation in its crystal structure and has very limited solubility. Therefore, quartz must be activated, usually by metal ions, for its effective rejection as a float-product by reverse flotation (AIME. et al. 1976)."

Jan 1, 2018

By C. S. Chen, Y. J. Luo, M. W. Gao, B. Li, Z. F. Zhang

"To obtain large-sized billets with fine grains and homogeneous elements distribution, uniform direct chill (UDC) casting process, based on annular electromagnetic stirring coupling with intercooling, was employed to produce 7055 alloy billets with a size of F584 mm in this study. The results indicated that there were the coupled effects of annular electromagnetic stirring and intercooling on grain refinement and element homogenization, and also the billets produced by the UDC casting process showed excellent hot workability in comparison to the normal direct chill casting process.INTRODUCTION The high solute 7055 aluminium alloy has a wonderful combination of high specific strength and hardness, good resistance to stress corrosion cracking and high fracture toughness, which is very useful in aerospace application (Yan et al., 2013; Mondal & Mukhopadhyay, 2005). The production of large-sized 7055 alloy billets with high quality is the basic condition for the subsequent application of 7055 alloy to the aircraft. Inhomogeneous microstructures and performances of 7055 billets result from the high alloying element content and the inhomogeneous cooling condition in different regions of billets during the conventional direct chill casting (Paramatmuni et al., 2004; Lalpoor et al., 2011), which will bring bad influence to processing property, functional performance and utilization rate of materials. To alleviate segregation and obtain fine and uniform grains, some effective treatment methods were proposed including electromagnetic stirring (EMS) (Vives, 1989), ultrasonic vibrating (Zhang et al., 2011) and melt conditioning (Fan et al., 2013), on the melt to obtain fine and uniform grains. However, these methods could not effectively decrease the large temperature difference between central and periphery parts of the billet, because the solidification mainly depends on outside cooling including mould cooling and water spraying cooling. To change the heat extraction pattern of the billet functioned solely from the outer surface, based on annular electromagnetic stirring (A-EMS) invented by Xu et al. (2010), Luo et al. (2017) proposed uniform direct chill (UDC) casting coupling A-EMS with intercooling in the direct chill (DC) casting process. An in-mold cooler was inserted to the melt sump, and thus the alloy melt temperature and concentration at solidification front become more uniform."

Jan 1, 2018

By V. Z. Kozin, E. A. Bekchurina, P. S. Volkov, Yu. P. Morozov, A. S. Komlev

"The current sampling systems of ore flows or concentrates are based on the method of cross sections in point sampling and the method of scooping in reducing. The limited number of point samples in sampling and microsamples in reducing lead to big random and probable systematic errors. The paper defines the principles of sampling, which assure the absence of systematic errors and also provides calculation formulas of probable errors in sampling methods of cross and longitudinal sections as well as in samples preparation. The article sets the fundamental laws of sampling: the dependency of minimal mass of gross sample and number of point samples from mass of point sample in sampling from heterogeneous body; the dependency of a sample minimal mass from lumps’ size in preparation of carefully mixed samples; the dependency of point samples’ dispersion from duration of control period. The paper introduces the fundamental notions: lump variance; probable systematic error; methodical error. It also provides a solution of outstanding sample correct application in analysis results calculations. In application of automatic analyzers, mounted in material flows, the probable error connected with sampling, is calculated by the formulas for carefully mixed sampling bodies. The paper describes the developed and introduced sampling systems on the base of combined application of cross and longitudinal sections methods in sampling and preparation of samples. The advantages of this equipment are compactness, reliability, simplicity in service and operation, and for pulps it is adaptability in pipelines. Application of the developed equipment entirely excludes probable systematic error. The new systems of sampling and preparation of samples are introduced at 25 concentrating plants. Introduction of the developed systems at sampling balance points of concentrating plants allowed double reducing balance deficiency."

Jan 1, 2018

By Zhu Yangge, Zheng Guibing, Hu Xiaoxing

"Because of the similar crystal structure and surface properties, it is very difficult to realize the efficient separation of magnesite and dolomite by flotation, which is the main reason restricting the utilization of magnesite resources with dolomite symbiotic. To deal with a magnesite resources with high content of calcium impurity in northwest China, a novel decalcification technology by combining flotation with leaching is proposed in this paper. In flotation process, a novel flotation collector with good efficiency and low temperature resistance was developed, and the depression effect of sodium hexametaphosphate was investigated. In leaching process, the leaching rate difference of calcium and magnesium was observed. By industrial test, from the magnesite ore with MgO content of 43.96%,the grade and recovery of obtained concentrate ( calculated by MgO) are 47.28% and 67.68% respectively, at the same time, CaO content decreases from 3.91% to 0.30%, which means that more than 95% of CaO impurity is removed.INTRODUCTIONMagnesite is one of the main raw materials for the production of refractory materials, and it is widely used in metallurgy, chemicals, ceramic, construction and other industries. China is the most important supplier of highquality magnesite resources, accounting for about 60-70% of the world's identified supply of magnesite products is provide by China (Jewell, 2014). In recent years, high-quality magnesite ores can be directly used are going to run out in China, and the utilization of magnesite resources with high impurity content have drawn more attention.The main purpose of purification for magnesite is to remove SiO2 and CaO impurities which affects the strength of the refractory material. Flotation is the commonly used method to remove impurities in magnesite ore. Reverse flotation with cationic collector is usually adopted to remove silicon containing impurities, and a great deal of literature has been reported (Santana A. N. and Peres A. E. C., 2001; Wang and Sun, 2008; Zhu et al, 2014; Wu et al, 2015; Ivan B. et al, 2017). But when the major gangue component is dolomite, it is very difficult to realize the efficient separation due to the similar crystal structure and surface properties between magnesite and dolomite. To solve this problem, researches have studied the surface properties of magnesite and dolomite, such as wettability, electrical property, solubility and solution chemistry (Nermin and Nurgul, 2006; Nermin 2006; Ozbek and Abali, 1999; Lacin et al, 2005; Bayrak et al, 2006; Bakan et al, 2006; Chen G. and Tao D., 2004), but the commonly studied direct flotation using oleic acid as collector is still hard to receive an ideal effect."

Jan 1, 2018

Low-grade ore bodies, increase in rock competency, finely disseminated valuable minerals in the ore bodies, ore variability and water scarcity are among the technical challenges faced by the mining industry. These challenges have increased the business risk, capital investment and operating cost of the mining projects. Since the last 20 years, many large-scale concentrators have been built to cope with the above-mentioned challenges. Comminution, especially the fine grinding is an energy-intensive process. For example, the ball mill has a limitation in the fine grinding regime where the energy consumption increases exponentially when the product size is below 45 µm. The industry has been seeking for solutions that have a minimum risk and total cost of ownership. The stirred milling technology such as the TowerMill is well accepted by the industry as it has demonstrated the attributes required for fine grinding. TowerMill is a matured technology that has been adopted since the 80s for regrinding duty. Recently, this technology was installed in secondary and tertiary grinding duty to prepare a finer feed to rougher flotation. Four units of TowerMills were installed in a magnetite concentrator in Western Australia in tertiary grinding duty. Recently, Nippon Eirich has conducted process performance evaluation on the TowerMill circuit. The outcome of the exercise had indicated that the circuit is consuming 3.4 kWh/t to reduce from 55 µm to 35 µm with a narrow product size distribution. The effect of operating variables such as the specific energy, grinding media size, mill content % solids and mill feed configuration on the grinding efficiency were evaluated at the plant scale. Furthermore, the scale-up methodology was validated. The scope of this paper includes the performances of TowerMill and the validation of scale-up methodology.

Jan 1, 2018

By Tina Schneider

Scientists show that polymetallic nodules and massive sulfides from deep sea mining contain valuable metals. These metals have the potential to overcome future shortages of supply. Hence, companies, government agencies and industrial associations increasingly evaluate deep sea mining as a promising supplement of land mining. Technologies to extract, exploit, transport and smelt polymetallic nodules and massive sulfides industrially are still in conceptual stage and not sufficiently advanced for operation. According to the International Seabed Authority, large scale exploitation would require a successful pilot mining test in order to demonstrate e.g. the technological feasibility but also the conservation of environmental systems services. At the same time, NGO´s and a some scientists point out that large scale extraction of polymetallic nodules and massive sulfides could disturb the habitat of benthic organisms, with unknown long-term effects. Aside from the direct impacts of mining, indirect consequences about leakage are likely. In the oral presentation I will show how companies, government agencies, scientists and association/interest groups perceive and assess economical/technological, social and environmental risks and opportunities of deep sea mining. In order to analyze the perspectives of each stakeholder group on deep sea mining, we conducted 15 interviews with four stakeholder groups and a large scale survey (n = 500, return rate = 13 %) in Germany. We used the concept of sustainability with its economical/technological, ecological and social dimensions for the interpretation of the results. The empirical research shows the following core results:

Jan 1, 2018