Search Documents

By Alper Turan, Hesham El Naggar

"The use of aggregate pier foundation systems has become widespread as the engineering practice moves towards cost-effective ground improvement solutions that provide accelerated construction schedules. Increased bearing capacity, effective settlement control and potential for liquefaction mitigation are commonly acknowledged benefits of aggregate piers. This paper studies the mechanisms by which aggregate piers interact with each other and with the surrounding ground when excited by seismic loads. A particular emphasis was placed on the response of a raft foundation supported on a site improved using aggregate piers. Three-dimensional nonlinear finite element analyses were conducted using commercial software package, ABAQUS. Non-linear soil behaviour is modelled using a three-dimensional total stress-based bounding surface plasticity model, which is able to simulate stiffness degradation and damping increase in the soil. The soil stratigraphy considered in this study was a 30 m deep soil deposit that comprised a very stiff base layer and a shallow soft surficial clay layer. Ricker Wavelet time histories with different frequency contents are used as the excitation force in the analyses. Various area replacement ratios (ARR) for aggregate piers are studied for a square plan layout. The results presented in this study are considered to be of interest to researchers and designers in evaluating the seismic ground response of the sites improved using aggregate piers. INTRODUCTIONThe schedule and cost limitations imposed by the traditional over-excavation and replacement method for the stabilization and settlement control for poor soils resulted are underlying factors for the significant increase in the use of aggregate pier foundation system, particularly in the last two decades. Various well known advantages of aggregate pier systems including increased bearing resistance, settlement reduction, and increased uplift capacity have been studied by various authors. The use of aggregate pier systems for settlement control in soft soil deposits was studied by various researchers including Lawton and Fox (1994), Lawton et al. (1994) and Wissmann et al. (2001). Lien and Fox (2001) studied the behaviour of aggregate pier systems supporting embankments and retaining walls. The stabilization of slopes by means of aggregate piers was studied by Lien and Fox (2001), Wissmann et al. (2002). Thompson et al. (2009) reported on a performance monitoring study of aggregate pier systems supporting MSE walls. The interaction mechanism between the aggregate pier system and the surrounding soil attracted attention of various researchers. Handy and White (2006a) and (2006b) studied the changes that occur less than 2 m from centers of the piers, and further away, respectively. The support mechanism of aggregate pier systems subjected to compressive loading were studied experimentally and numerically by White et al. (2007) and Pham and White (2007), respectively."

Jan 1, 2017

By I. Moreno-Ventas, G. Ríos, J. C. Fernández-Caliani, M. Bacedoni

"This paper delves into the constraints on the nature, origin and thermal evolution of the accretions formed in the uptake shaft of the flash smelting furnace operated by Atlantic Copper in Huelva, Spain, outlining recommended practices for preventing accretion buildup. The accretions were investigated using quantitative electron probe microanalysis, X-ray diffraction and digital imaging techniques, and the experimental data on mineral composition, crystal chemistry and textural relationships were interpreted in terms of thermodynamic phase equilibrium in the SiO2-Fe-O-S system. The results suggest that two distinct types of accretions were formed by the fractional crystallization of two coexisting immiscible melts, under changing conditions of oxygen partial pressure (pO2). The type I accretion of magnetite + delafossite ± cuprite ± tridymite ± metallic copper crystallized from a fractionating copper-rich melt at pO2 above about 10-5 atm, while the type II accretion of magnetite + fayalite + metallic copper + chalcocite derived from a melt with lower copper concentration when pO2 levels dropped below that critical level. Phase compositions and textures were consistent with a cooling history of both compositionally contrasting liquids from about 1,250 °C, the liquidus temperature of magnetite, to eutectic or near-eutectic temperatures of around 1,100 °C. The maintenance of appropriate temperatures — above the liquidus temperature of magnetite — and oxygen partial pressure levels may be critical for the prevention of accretion buildup. IntroductionCopper flash smelting with oxygen-enriched air, an autothermal process developed half a century ago by Outotec (Espoo, Finland), formerly Outokumpu, currently accounts for about 50 percent of the world’s primary sulfide-based copper (Schlesinger et al., 2011). The partial reaction of copper sulfide concentrates produces two separate molten streams, copper-iron-sulfide matte and iron oxide-rich slag, and releases sulfur dioxide (SO2) gas. The matte is sent to converters to remove the remaining iron and sulfur, leaving blister copper with grade of about 99.5 percent copper (Cu), which is cast into anodes for electrolytic refining.The SO2-rich gas generated by the oxidation of sulfide feed particles contains a significant proportion of dust that is entrained in the process off-gas. The gas from smelting is transferred into a waste heat recovery boiler, where it is cleared of dust and cooled before it is converted into sulfuric acid. If the process is not operated properly, the dust-bearing gas may form accretions between the uptake shaft of the flash smelting furnace and the waste heat recovery boiler, causing severe problems in the gas handling system (Swinbourne, Simak and Yazawa, 2002; Miettinen, 2008; Stefanova et al., 2012). Removing the dust accretions usually requires a greal deal of time, effort and resources. Understanding the buildup of accretion may help in reducing the problems and optimizing the process"

Jan 1, 2017

By Matthew Kowalczyk, Steve Bloomer, Peter Kowalczyk

"Mineral deposits found near seafloor hydrothermal venting are of great economic interest. Valuable metals such as gold, copper, zinc, and other polymetallic sulfides are found in appreciable grades in seafloor massive sulfide (SMS) deposits associated with these vents. For mapping these deposits, electromagnetic prospecting is one geophysical method that is very useful because copper/gold rich deposits are highly conductive.Ocean Floor Geophysics (OFG) in 2008 developed the first EM system to successfully map the limits of conductive mineralization in a survey at the Solwara 1 deposit (Kowalczyk, 2008). Since then, towed coincident loop time domain systems have been developed by Waseda University (Nakayama and Saito, 2016) and have successfully detected known mineralization buried at 30m depth. Using a deep tow controlled source electromagnetic (CSEM) array, very clear anomalies have been measured (Murton, 2017) over known mineralization at the TAG field on the mid-Atlantic ridge.In 2014 and 2015, OFG partnered with Fukada Salvage and Marine Co. Ltd. and the Scripps Institution of Oceanography to map methane hydrate deposits off the coast of Japan using a towed controlled source electromagnetic (CSEM) system developed by Scripps. These hydrate deposits are resistive targets, and the Scripps system successfully mapped subsurface electrical resistivity distributions to depths of several 100 metres below the seafloor. OFG is attempting to extend the Scripps CSEM technology to map subsurface conductive SMS deposits to a similar range of depths below the seafloor."

Jan 1, 2017

By Chandramohan P. V., Ravi Kishore

"An underground reservoir was to be constructed at Doha in Qatar. Simsima lime stone is present at the bottom. When the reservoir is empty, there will be uplift at the bottom but this will change to downward load when it is full. The rock at the bottom had high bearing capacity to resist downward load. But uplift had to be resisted by piles or anchors. The reservoir has a size of 120mx80m. Shrinkage and creep of concrete coupled with thermal contraction imposed a horizontal movement of 26mm on the extreme piles. So, piles have to accommodate this as well. This unique situation needed a unique solution. The solution was to provide piles with flexible high tensile strands to take tension. An annular space near the head of the pile would facilitate horizontal movement as well. Compression load was directly passed on to the raft bearing on rock.INTRODUCTIONAn underground reservoir for storage of drinking water was to be constructed at Doha, Qatar. The reservoir was proposed to have a plan size of 120m x 80m. Clear height inside the reservoir was proposed as 17.2m, from the bottom of roof to the top of bottom raft. Overall height of the reservoir at the outlet from the top of the roof to the bottom of raft was to be 21.2m. For the sake of inspection and in order to prevent pollution from the surroundings a gallery was planned around the reservoir. This could accommodate pipelines as well. This gallery was 3.0m wide on three sides and 8.4m wide on the outlet side.The gallery had removable gratings as cover in order to facilitate maintenance. Capacity of the reservoirwas proposed to be 40million gallons. The reservoir is divided into four compartments with baffle walls in each one for water circulation. Roof of the reservoir is kept at 300mm above ground level. There are two levels of car park on top of the reservoir. Top of the reservoir roof is at +14.35. Bottom varies from - 6.68 to -7.08. Lowest water table is at +6.00. Concrete structure of the reservoir was designed by a local consultant. The Navayuga Engineering Company was entrusted with the construction. Please see Figs 1 and 2."

Jan 1, 2017

By L. Chanderman, C. E. Dohm

"Mineral Resource estimation (MRE) and classification are highly dependent on the confidence in the model of the orebody geometry, known as the geological model, within which the estimates are constrained. An understanding of the geology of a deposit is thus fundamental to the Mineral Resource evaluation process. The geological model is a function of the structural and depositional complexity of the geology captured by drilling information, which is limited in the early stages of a project. The information effect has a significant impact in terms of the interpretation of the geology as well as the estimation of grade continuity and the resultant risk associated with the Mineral Resource estimate and classification.Therefore, as new drilling information becomes available, it is necessary to update and refine the geological model to appropriately constrain the resource estimates. The grade information is also updated, including statistics and the spatial correlation characteristics. This refinement is based on geological interpretations derived from the drillhole information that becomes available throughout the life of the mine; orebody knowledge that comes from working experience of the deposit, as well as familiarity with the software package used for modelling, is also important.In updating, the potential to identify new resources in previously unknown areas may be realized. The opposite may also occur where previous interpretations of ore continuity are refuted. Both scenarios could result from a better understanding of the geology of the deposit and thus a more realistic MRE, which reduces geological risk. This paper describes how newly drilled advanced grade-control holes for a gold deposit in Mali were used to refine the 3D geological model for the deposit in an attempt to identify the potential for additional oxide ore using conventional geostatistical evaluation techniques."

Jan 1, 2017

By Mohammad Ali Rowshanzamir, Mehdi Aghayarzadeh

"This article is an effort to improve our understanding of the performance of geogrid retaining structures (GRS) through numerical analyses. The numerical modeling utilized a commercially available finite difference program, FLAC3D. In this context an extensive parametric study has been carried out on two different GRS walls (vertical reinforced block and inclined reinforced block) to investigate the influence of internal design factors such as soil strength properties and reinforcement stiffness on the performance of these walls. The main purposes of the parametric study were to (1) investigate the sensitivity of the modeling results to the input material properties, (2) examine the influence of the internal design factors on the performance of GRS retaining structures, and (3) improve the internal design of GRS walls on the basis of the working stress information obtained from the parametric study. Based on the analyses results, it was revealed that GRS walls with oblique reinforcement and reinforced block (rotated against natural backfill) have much better performance in terms of reduction in the stresses and strains of reinforcing elements as well as decrease in the wall lateral and vertical displacements in comparison with vertical reinforced block (conventional wall). For example, with 12° inclination of the wall reinforced block there was 50% reduction in the backfill settlement. Also increasing the reinforcement stiffness amount from 10MPa to 50MPa decreases the wall face displacement more than 50% in both GRS walls.INTRODUCTIONOver the past few decades, Geosynthetic- Reinforced Soil (GRS), a soil mass reinforced by geosynthetic layers to restrain the soil lateral deformations, has been employed in the construction of many types of earth structures, including retaining walls, embankments, slopes and bridge abutments. In fact GRS structures are typically more flexible (hence more tolerant to differential settlement), more adaptable to low quality backfill, easier to construct, require less over-excavation, and more economical. Nevertheless, there is a need for an accurate design tool that can predict the performance of GRS structures under working stress conditions and can predict their failure loads as well.Many studies have been published on the performance of the soil reinforced walls such as Isabel et al., 1996; Bathurst et al., 2000; Kazimierowicz-Frankowska, 2005; Nernheim and Bathurst, 2008; Chen and Chiu, 2008 Correia et al., 2012; Erlich et al. 2012. Several numerical studies have also been made throgh finite elements and finite difference techniques on reinforced soil retaining walls to analyze the wall deformations (e.g. Hatami et al. 2001& 2006, Liu and Won 2009, and Abdelouhab et al. 2011). A limited laboratory research has been reported indicating of improving effect of tilting face on GRW performance (Chen and Chiu, 2008). However no major numerical study was found on the effects of face or reinforcement tilting."

Jan 1, 2017

By Jin-Wei Huang, Bradley J. Fleming, Sri Sritharan

"Although soil improvement and its application to deep foundations is gaining popularity in the engineering community, this technique is not widely used in high seismic regions due to lack of fundamental understanding of both the behavior of improved soils under high-strain cyclic loading and the interactions between the pile, improved soil, and unimproved soil. This paper describes part of an ongoing Network for Earthquake Engineering Simulation (NEES) project, where two identical full-scale steel pipe piles were driven at a soft clay site in Oklahoma. The soil surrounding one of these piles was improved using the cement deep soil mixing technique in order to enhance its lateral load behavior. Both piles were tested for seismic resistance using dynamic and quasi-static loading.The pile in unimproved soil provided larger displacements with limited lateral force resistance. This pile was subjected to lateral displacements of up to 400 mm, but experienced minimum inelastic actions. On the other hand, the pile in improved soil reached its lateral capacity at a displacement of 100 mm, at which point the critical region at the base of the pile just above the improved ground experienced buckling and fractured due to low cycle fatigue. Compared to the pile in unimproved soil, the improved ground increased the system strength by 42%. Although the soil was improved over 2900 mm, the effective improvement depth was approximately 1300 mm below the ground surface.In this paper, it is demonstrated that the effects of block type soil improvement of limited horizontal and vertical dimensions can be described using a simplified theoretical approach involving a modification to the well-known p-y representation of soil response. An example using this method is presented and shown to give adequate support to a standard 12-inch diameter steel pipe pile embedded in soft soil,IntroductionPilings are the preferred foundation support for many civil engineering structures including highway bridges, railroad bridges, and port wharves. These structures and their foundations are subjected to forces created by earthquakes, wind, waves, water current, vessel impact, ice, and gravity. All loads applied to the superstructure must be transmitted to the foundation where they are resisted by the surrounding soil. With significant lateral loads, use of pile foundations may be the only solution to transmit large structural loads to competent soils. Piles supported by competent soils are relatively easy to design and costs are often attainable. However, thick layers of weak soils such as soft clays are widespread in high seismic areas (e.g., San Francisco, southern Nevada, Washington, Eastern Missouri, and Arkansas), exacerbating design challenges. Soft clays reduce the lateral resistance of the pile-soil system, making the pile foundation less cost effective. In this case, the current design practice is to use an increased number of larger diameter piles, which is a costly alternative (see SDC, Caltrans 2010). An innovative and more cost-efficient solution to this problem is to improve the soil within a short depth surrounding the foundation, thereby increasing its lateral stiffness. Some well-known methods for improving soil include deep soil mixing, stone columns, and simple soft soil replacement with select granular material."

Jan 1, 2017

By Tatiana ?. Sedysheva, Vladimir V. Ivanov, Michail E. Melnikov, Irina A. Pulyaeva

"INTRODUCTIONHydrogenetic Fe-Mn crusts are ubiquitous in the ocean basins and play an important role in marine mineral-deposit research because of their widespread occurrence and high concentrations of valuable and rare metals. Directed research, which started in the last quarter of the 20th century, has provided significant results, with substantial amounts of data produced on Fe-Mn crusts structure, composition, and distribution in the global ocean [3, 4 - 8]. Now, commercial interests gain more and more attention. Mining systems are being developed which involve fragmentation of the crusts and their separation from the substrate. The effectiveness of such activities greatly depends on physico-mechanical characteristics of the crusts and rocks on which they form. This determines the importance of the engineering geological study of the objects.This article comprises the results of the engineering geological studies of the crusts samples (72 samples) and their underlying rock substrates (75 samples), which were carried out during the research cruises 6-06, 6-07, 6-08, 6-13 (2006-2013) on the Magellan Seamounts guyots in the Western part of the Pacific Ocean by the specialists of the State Scientific Centre Yuzhmorgeologia [10 - 13, 19, 20]. The authors of the article directly participated in the studies mentioned above.MethodsEngineering geological studies were carried out on board of the research vessel Gelendzhik and in the laboratories of NPA «Sevmorgeologiya». The studies involved the determination of the following parameters:"

Jan 1, 2017

By Joe Wickline, Mark A. Van Dyke, Wen H. Su

"Geological factors and mine design contribute to mining-induced seismic activity, and this is especially true in longwall mining. Massive rock units are a key cause of seismic activity due to catastrophic failures that release large amounts of energy. Other factors, such as overburden depth, panel design, pillar design, rock strength, and proximity of the massive rock unit to the coal seam, all have a role in the potential and size of a seismic event. A recent seismic event was recorded by a deep longwall mine in Virginia at 3.7ML on the local magnitude scale and 3.4 MMS by the United States Geological Survey (USGS) in July 2016, which had no impact on the mining operations. Further investigations by NIOSH and Coronado Coal researchers have shown that this event was associated with geological features that have also been associated with other, similar seismic events in Virginia. Detailed mapping and geological exploration in the mining area has made it possible to forecast possible locations for future seismic activity. In order to use the geology as a forecaster of mining-induced seismic events and the energy potential, two primary components are needed. The first component is a long history of recorded seismic events with accurately plotted locations. The second component is a high density of geologic data within the mining area. In this case, 181 events of 1.0ML or greater were recorded by the mine’s seismic network between January, 2009, and October, 2016. Within the mining area, 897 geophysical logs were analyzed from gas wells, 224 core holes were drilled and logged, and 1,031 fiberscope holes were examined by mine geologists. From this information, it was found that overburden thickness, sandstone thickness, and sandstone quality contributed greatly to seismic locations. After analyzing the data, a pattern became apparent indicating that the majority of seismic events occurred under specific conditions. Three maps were created using MineScape geological mapping software. MineScape deploys an interpolator known as FEM (finite element method) and is based on a series of gridded triangles to forecast the probability and magnitude of an event if a particular panel were to be mined. The forecast maps have shown accuracy of within 74%–89% when compared to the recorded 181 events that were 1.0 ML or greater when considering three major geological criteria of overburden thickness of 1900 feet or greater, 20 to 40 feet of sandstone within 50 feet of the Pocahontas number 3 seam, and a longwall caving height of 15 feet or less."

Jan 1, 2017

By T. Gammatikopoulos, C. Gibson, M. Aghamirian

Lithium is an alkali metal found in brine deposits in the United States, Chile and Argentina, as well as in hard rock deposits in Australia and North America. In hard rock deposits, spodumene (LiAl(Si2O6)) is the major economic lithium bearing mineral. Spodumene is typically upgraded through a combination of dense media separation, flotation and magnetic separation. One of the major spodumene concentrate quality specifications is the iron oxide content because it will help determine if the concentrate is considered ceramic grade for use in ceramics and glass or chemical grade for use in lithium ion batteries. The rejection of iron bearing silicate minerals from artificial ore composites (high amphibole and low amphibole, high quartz/feldspar) from a hard-rock spodumene deposit was investigated using magnetic separation and flotation. The efficacy of Wet High Intensity Magnetic Separation (WHIMS) in iron rejection was found to be dependent on the mineralogy of the iron-bearing silicate minerals including modal distribution, liberation and association. When magnetic separation was conducted prior to flotation, the Fe2O3 grade in the final flotation spodumene concentrate was reduced from ~3% to ~1% Fe2O3 , and improved lithium recovery in flotation was observed. It was determined that it was most effective to conduct WHIMS on the flotation feed after scrubbing and de-sliming because this reduced the required magnetic field to recover iron-bearing minerals, likely because slime coating was greatly reduced. Flotation collector screening of four different collectors with varying rosin acid content demonstrated a potential increase in selective flotation of spodumene over some iron silicate minerals with decreasing rosin acid content in the fatty acid collector. However, due to marginal difference in flotation results with the various collectors tested, further testing is required to confirm the observations made and establish a hypothesis regarding the effect of rosin acid content.

Jan 1, 2017

By Tano Balbin, Valery Astakhov, Juha Timperi, Lauri Koresaar

"Online elemental analysis is the basis of optimal flotation control in mineral concentrator plants. Traditionally XRF analyzers have been used as the online analysis method. However, online XRF analyzers struggle to measure elements below calcium in atomic number (Z=20). For many processes lighter element assays would be beneficial to improve control of grade and recovery. Processes where elements below Ca are required include P, Mg and Si in phosphate concentrators, Si, Mg and Al in iron concentrators, and S and C in gold concentrators. Laser-Induced Breakdown Spectroscopy (LIBS) based elemental analysis can readily be applied to these processes. LIBS is based on generating plasma in the slurry sample by a high energy laser and analysis of the plasma by optical emission spectroscopy. Capabilities of a new Courier® 8 analyzer based in LIBS technology are demonstrated for elemental analysis starting from lithium (Z=3). Results of a plant installation in a sulfide gold concentrator provide a good agreement with the analyzer and laboratory assays.IntroductionEffective process control can be regarded as one of the fastest paying investments for a mineral processing plant. Process optimization in flotation circuits requires constant feedback of the process state. If only manual laboratory samples are available, this optimization becomes difficult due to the long delay between taking the sample and acquiring the laboratory result. If the element grades are available in online basis, the operator or automatic process control system can make corrective actions in real time.Online X-Ray Fluorescence (XRF) analyzers have been in use at concentrators for decades. The XRF analyzers can provide a fast, accurate and precise analysis from slurry streams. However, the drawback of XRF analyzers is their lack of capability to measure elements below Ca (Z=20) in atomic number. The low energy X-rays of the low atomic number elements get absorbed by water in the sample, protective window of the analyzer, or air between the sample and spectrometer."

Jan 1, 2017

By John Jiang, Brian R. Hart, Stamen S. Dimov, Aparup Chattopadhyay, Barun K. Gorain

"This paper presents a systematic approach to metallurgy diagnostics using an integrated gold deportment methodology developed for complex refractory gold and copper-gold ore bodies. Quantification of gold deportment for these ore bodies is a challenging task due to reasons such as lower grades, high variability of visible and invisible gold content in different sulphides and iron oxide phases, significant presence of disseminated and composite carbonaceous matters along with associations of various copper sulphide phases. Some case studies are presented in this paper to demonstrate the value of a high confidence gold deportment methodology in developing insights for problem diagnostics and to identify opportunities for metallurgical improvements. A holistic approach involving different fields of expertise is critical for successful development and delivery of solutions for complex ore bodies.INTRODUCTION Studies were initiated on various complex ore deposits and also on samples representing various process streams. These complex copper-gold single refractory, double and triple refractory gold ores are mainly composed of silicates and/or carbonates with moderate amounts of clay and mica, along with minor amounts of sulphides and organic carbonaceous matter. Variable proportions of visible gold and “invisible gold” (sub-microscopic gold) were noted in different mineral phases for various ore types and process stream samples. Invisible gold commonly occurs as solid solution or as colloidal-sized particles in different sulphides and other phases for different refractory ores. The dominance of invisible gold and presence of highly preg-robbing along with finely disseminated carbonaceous matters adversely affects gold recovery in flotation and leach circuits for most of these double and triple refractory ores. This paper discusses applications of an integrated gold deportment technique developed for different types of gold and copper-gold ores, namely, complex copper-gold, double and triple refractory gold ores (Chattopadhyay & Gorain, 2014; Chattopadhyay et al., 2016). Various process streams from flotation and gold leaching circuits were investigated. Different concentrates and tailings samples from flotation circuits whereas feed and discharges from pressure oxidation (POX) and carbon-in-leach (CIL) residues were used from gold processing circuits."

Jan 1, 2017

By K. Liu

"In the present work, two-step heat treatments with preheating treatments at different temperatures (175, 250 and 330°C) as the first step followed by the peak precipitation treatment (375°C/48h) as the second step have been performed in Al-Mn-Mg 3004 alloys to study their effects on the formation of dispersoids and evolution of elevated-temperature strength and creep resistance. During the two-step heat treatments, the microhardness is gradually increasing with increasing time until to a plateau after 24 hours when first-treated at 250°C and 330°C while there is a minor decrease with time at 175°C. Results show that both the yield strength and creep resistance at 300°C reach the peak values after the two-step treatment of 250°C/24h+375°C/48h. The formation of dispersoids is greatly related to the type and size of pre-existing Mg2Si precipitated during the preheating treatments, in which that coarsened rod-like ß’-Mg2Si strongly promotes the nucleation of dispersoids while finer needle-like ß’’-Mg2Si has less influence. Under optimized two-step heat treatments and modified alloying elements, the yield strength at 300°C can reach as high as 97 MPa with the minimum creep rate of 2.2×10-9 s-1 at 300°C in Al-Mn-Mg 3004 alloys, enabling them as one promising candidate in lightweight aluminum alloys for elevated-temperature applications.INTRODUCTION Due to the rapid demand from weight-sensitive automotive and aerospace industrials for the light alloys, such as aluminum alloy on the elevated-temperature applications, Al-Mn 3xxx alloys has been developed to obtain the good properties at both room temperature (RT) and elevated temperature, in which the dispersoid-strengthening mechanism plays a significant role (Li & Arnberg, 2003; Li, Muggerud, Olsen & Furu, 2012; Liu & Chen, 2015, 2015). In our previous works (Liu & Chen, 2015, 2015; Liu, Ma & Chen, 2017), the yield strength and creep resistance at 300°C of Al-Mn-Mg 3004 alloy were further improved by modifying the alloying elements, such as Fe and Mo, to optimize the characters of dispersoids, including the size, distribution and the dispersoids free zone (DFZ). For instance, Mo was introduced in aluminum alloy to further improve the volume fraction of dispersoids and reduce the area of DFZ, leading to increasing on both the strength and creep resistance at 300°C (Liu, Ma & Chen, 2017). On the other hand, the mechanical properties became worse at higher Fe content due to its consumption more Mn to form Al6(MnFe) intermetallics, resulting in less available soluted Mn for the precipitation of dispersoids (Liu & Chen, 2015). Therefore, optimizing the characters of dispersoids is always the key to improve the elevated-temperature properties of dispersoid-strengthened aluminum alloys for elevated-temperature applications."

Jan 1, 2017

By B. Haugrud, E. McConaghy, M. Collins, G. Smith

"Laterite ore processed by the Ambatovy joint venture in Madagascar is primarily limonitic in nature, containing approximately 40–45 wt.% Fe and 1.1 wt.% Ni. The process selected for treatment of this ore considered the behaviour and deportment of iron in each step of the commercial flowsheet. Such considerations included nickel and cobalt recoveries, reagent consumptions, liquid-solid separation characteristics, and intermediate and final product purities. In this paper, the results for the first three years of commercial operation at Ambatovy are compared with the design parameters, with emphasis on the behaviour of iron.RÉSUMÉ Le minerai latéritique traité par l’entreprise commune Ambatovy au Madagascar contient principalement de la limonite, composée de 40–45 % en poids (wt%) de fer (Fe) et de 1,1 wt% de nickel (Ni). Le procédé choisi pour le traitement de ce minerai tenait compte du comportement et du maintien du fer à chaque étape du schéma de traitement commercial. Parmi les facteurs pris en compte figuraient les récupérations de nickel et de cobalt, les consommations d’agents réactifs, les caractéristiques de séparation des liquides-solides ainsi que la pureté des produits semi-fini et final. Cet article compare les résultats des trois premières années d’exploitation commerciale à Ambatovy aux paramètres d’étude, en insistant notamment sur le comportement du fer.INTRODUCTIONThe main component of nickeliferous laterite ore is iron, and the Ambatovy deposit in Madagascar is no exception. Ambatovy ore is primarily limonitic in nature, containing approximately 40–45 wt.% Fe and 1.1 wt.% Ni. The nickel content of the ore is approximately 1/40th that of the iron content by weight; therefore, successful recovery of nickel depends on close control of the behaviour of iron in the selected process.The Ambatovy area is located 80 km east of Antananarivo, the capital of Madagascar. Exploration dates back to 1960, when the Malagasy Service Géologique carried out a limited pitting and auger-drilling program. Phelps Dodge Corporation (now Freeport-McMoRan Copper & Gold, Inc.) was granted the mining rights to the property in 1995 and carried out significant resource definition, environmental assessment, and engineering studies between 1995 and 2001 (Chou, Rooke, Williams, & Hanks, 2000). In 2003, Dynatec Corporation, which was formed in 1997 by the merger of Dynatec International Ltd. and Sherritt International Consultants Inc., signed a joint venture agreement with subsidiaries of Phelps Dodge to evaluate the Ambatovy nickel project. Dynatec became extensively involved in the development of the project, including process selection and pilot plant testing in Fort Saskatchewan, Alberta (Collins et al., 2004, 2005; Collins & Vardill, 2005; Collins, Buban, Holloway, Masters, & Raudsepp, 2009). Dynatec acquired 100% of the project in 2005 and a joint venture between Dynatec, Sumitomo Corporation, Korea Resources Corporation (KORES), and SNC-Lavalin Inc. (SLI) was formed shortly thereafter to provide funding for further development. SLI was responsible for engineering, procurement, and construction management of the commercial facilities. Sherritt International Corporation reacquired Dynatec Corporation, including 40% ownership in the Ambatovy nickel project, in 2007. The current Ambatovy joint venture consists of an integrated nickel and cobalt mining, processing, refining, and marketing enterprise between subsidiaries of Sherritt (40% owner and mine and plant operator), Sumitomo Corporation (32.5% owner), and KORES (27.5% owner)."

Jan 1, 2017

By Weiying Zeng, Shouwei Wang, Jinbei Zhong, Xiangdong Meng, Lingtian Meng

"Due to a drainage problem, the Lanzhou to Chongqing high-speed rail line had been out of service during the 2015 wet season, so a drainage tunnel is to be constructed for the line and required to be accomplished before the 2016 wet season. This drainage tunnel is only 5 meters below the line which is in service, therefore blasting vibration needs to be strictly controlled. This paper introduces all theapplied blasting methods, parameters and detonation throughout the entire project, finally bringing in the electronic detonator stagger phase technique and corresponding time difference for detonation."

Jan 1, 2017

By F. Wendling, R. C. Nascimento, S. S. Wendling

"The objective of this research is to study the quality of blast-furnace iron ore pellets with binary basicity 1 fired on a pilot scale using the two main firing processes that are presently in use in the world and comparing them. Currently, the great majority of pellet producers use the traveling grate process because of its higher production capacity. In this study, the physical and chemical qualities of the pellet feed, limestone, anthracite and bentonite were determined and the amount of additives for a blast furnace pellet with the defined basicity was calculated. The physical properties of the green and dried pellets were determined accordingly. Produced pellets, after being fired on a pilot scale using traveling grate and grate kiln, were subjected to chemical analysis and physical testing. No significant difference was observed in the metallurgical quality — that is, reducibility index (RI), reducing disintegration index (RDI) and swelling index (SWI) — of the pellets produced by both processes. However, a comparison of cold physical tests — tumble and cold compression strength — shows improved quality of the pellets fired using the grate kiln process.IntroductionThe development of human civilization owes much to iron and steel (Sun et al., 2015). Iron is the most used metal in the world, and it is the main component of steel, which is present in materials for structural engineering, automotive and general industrial applications (Liu et al., 2014). Increased global demand has led to a decrease in the resources of ore with high iron content (Zhang et al., 2015), and currently 95 percent of the iron ore in China needs processing before smelting as its iron (Fe) content is only about 30 percent on average (Liu et al., 2014).Pelletizing is a process to economically agglomerate iron ore pellet feed into pellet form. After balling, green pellets are conveyed to the final step of the manufacturing process (Pena, 1982). The process is a multifaceted one, involving high temperatures, air flow gas turbulence and complex equipment geometry (Larsson et al., 2009). The pellets are fed into blast furnaces, which are now predominantly used in the extraction of iron. Ore processing also requires physical separation, including crushing, grinding and water removal (Sun et al., 2015).The increase in steel consumption favors the exploitation of low-concentration ores and the production of pellets (Halt and Kawatra, 2014). Pellet quality is affected by various factors, such as their physical and chemical characteristics and their temperatures and residence times in the furnace (Halt, Silva and Kawatra, 2015). Different geological settings lead to a wide range of different minerals (Graça et al., 2015).This work aims to generate important information for the pellet industry in the area of physical and metallurgical qualities of the agglomerates obtained by two processes: traveling grate and grate kiln."

Jan 1, 2017

By Austin Metz, Kevin Stanton, Ramin Motamed

"A recent study calibrated Load and Resistance Factor Design (LRFD) resistance factors for local soil conditions in the Las Vegas Valley. As a part of this calibration, an extensive database of drilled shaft load tests and associated subsurface soil information were collected and compiled. This database, deemed the Nevada Department of Transportation Deep Foundation Load Test Database or NDFLTD, was designed with the presentation of load test data, the subsurface soil conditions, and the spatial distribution of the data in mind. In addition, the NDFLTD was developed in a way that allows additional data to be added as it becomes available. As such, the rules of database normalization were followed to allow for additional and different types of data to be added to the database and reports. Microsoft Access was chosen to present the data because it is easily accessible to anyone with Microsoft office software, it has a quick learning curve, and it has the ability to present a relational database. The largest obstacle faced when creating the NDFLTD was normalizing the data used in the LRFD calibration, with the goal of reaching the 5th normal form.INTRODUCTIONLRFD is based on statistical performance of engineering components, as opposed to the more traditional Allowable Strength Design (ASD), which divides the strength of a component by a safety factor. Calibration of resistance factors for LRFD requires a robust statistical analysis of past performance. For drilled shafts this requires a database of full scale load tests (Abu-Hejleh et al. 2014). The FHWA developed the largest US based deep foundation load test database, deemed the DFLTD, collecting data from 1985 to 2003 when funds ran out (Abu-Hejleh et al. 2014). Recently, the DFLTD has been updated to modern standards (Petek et al. 2016). In October of 2007, the FHWA mandated state department of transportations (DOTs) to follow AAHSTO LRFD guidelines for their highway foundation designs (Abu-Hejleh et al. 2014). Since then multiple state DOTs have developed their own, region specific deep foundation load test databases. Florida has a long history of developing databases for deep foundation LRFD resistance factor calibration, with the two main databases being the FL database, and The Deep Foundations Database (Abu-Hejleh et al. 2014). Iowa developed a Microsoft Access based database in 2014 (Garder et al. 2014). Oregon developed a database compiling pertinent data from the DFLTD, Florida DOT’s Deep Foundation Database, as well as from other databases (Smith et al. 2011). Illinois developed the “International Database” for static and dynamic reliability based calibration (Long et al. 2009). Louisiana developed a database for LRFD Calibration of driven piles in 2009 (Abu-Farsakh et al. 2009). The California Department of Transportation has its own internal foundation database, which is housed within the Foundation Testing Branch archive (Smith et al. 2011). In 2016, the Nevada Department of Transportation (NDOT) presented its own LRFD calibration for the Las Vegas Valley (Stanton et al. 2017), and the NDFLTD was developed as a part of that project (Motamed et al. 2016)."

Jan 1, 2017

By S. J. Schatzel, J. D. Addis, V. Gangrade, L. L. Chasko, C. A. Hollerich

"A ventilation study using tracer gas was conducted at a western US coal mine. The objective of the study was to evaluate the movement of longwall face air exchanges between the face and worked-out area and to document the presence or absence of face airflow pathways between these locations. The mine operator uses a bleederless longwall ventilation system with a back return and a blowing mine ventilation system. The study was conducted on an active panel and included both underground and surface monitoring sites. The study used sulfur hexafluoride (SF6) released as a slug on the longwall face and in the front of the gob inby the face. The velocity of the tracer gas movement in the gob was 0.019 m/s (3.7 fpm). The rate of movement for the overall tracer gas slug averaged about 0.0091 m/s (1.8 fpm). A separate tracer gas test initiated with the release of SF6 into the legs of the first shield showed the existence of more than one pathway of face air in the general direction from the headgate towards the tailgate corner. Maintaining adequate ventilation air on longwall faces is important for worker safety and for the dilution of methane emitted from the face and caved gob. A more detailed characterization of longwall system air and gas movement allows a mine to better assess its ventilation design for controlling gas on the face and in the gob. INTRODUCTION During a series of stakeholder meetings, a near unanimous concern was expressed related to maintenance of effective ventilation airflow on longwall faces. There was a strong interest expressed regarding the impacts of face length and caving characteristics on the ability to maintain adequate face airflow levels. This study seeks to understand and improve a mine operator’s ability to monitor and control ventilation and methane concentrations across the longwall face by assessing airflow variations in terms of roof caving characteristics and face length. National Institute for Occupational Safety and Health (NIOSH) researchers seek to identify flow paths of ventilation airflow on longwall panels with variations in roof caving characteristics and longwall face lengths. The project research aims to develop an understanding of the role of gas dynamics in variable broken rock, interactions with ventilation airflow and methane concentrations across the longwall face area. The research also addresses continuous ventilation monitoring along the shield line to provide early detection of gas exchanges between face and gob, and thus improve a mine operator’s ability to monitor and control ventilation and methane concentrations around the face. In the context of this paper, the longwall gob refers to the pillared area behind the shields. This work reports on results from one project task to conduct field based research using a tracer gas to describe face air and gob area gas movement in a bleederless longwall ventilation system that incorporated a back return."

Jan 1, 2017

By M. M. Veras, C. H. Sampaio, A. S. Young, D. Neto, C. O. Petter

"Due to new technological developments, automatic sensor based sorting has made progress within industrial minerals, precious metals, diamond, and coal mining in recent years (Lessard et. al. 2016). In order to re-introduce the technology to other mining sectors, this research discusses its application to iron, manganese, and zinc ores through test works performed by the authors. These test works were performed using Dual Energy X-ray Transmission (DE-XRT) sensor technology. In each case, pre-concentrations of the ore were created demonstrating the possibility to reduce waste material, energy costs, and water consumption while improving product quality of the ores. INTRODUCTION Sorting of mining ores is as old as mining itself (Salter, 1991). Sensor based sorting applications in coal mining began as early as the late 19th century (Louis 1928). New sensor technologies were developed and implemented sequentially for uranium, nickel, coal, and gold mining (Refining, 1949, Rose et al, 1950, Bloomfield et al, 1966, Clayton et al, 1987, Robben and Mosser, 2014). While these sensor technologies were developed decades ago, computational capacity to keep pace with the vast amount of information required utilizing the sensor technology did not arrive until recently (Lessard et. al., 2016). The sensor based sorting (SBS) process was effectively described by Salter and Wyatt in Minerals Engineering in 1991, and Wotruba and Harbeck in 2010 in the Ullmann’s Encyclopedia of Industrial Chemistry under Sensor Based Sorting. Both descriptions include the following key steps: 1. Presentation of the material or particles. 2. Examination or detection of the material or particles. 3. Processing or analysis of the data generated. 4. Physical separation of the material or particles by external means. Effective presentation of the material or particles is achieved when the sensor is capable of identifying each particle individually. This step requires that each fragment of the material be isolated, and it often involves acceleration of the material fragments by chute or mechanical means, as well as the spreading of particles by vibratory feeders (Salter and Wyatt, 1991, and Wotruba and Harbeck, 2010). The isolated particles typically are conveyed into an area wherein they are subjected to electromagnetic irradiation (except in cases of some radioactive ores), either in the form of x-ray, visible light, infrared, or other energies. A wide range of applications for sensor based sorting exists in the literature. The majority of applications fall into one of two camps, (1) pre-concentration of mineral ores, or (2) characterization of the material during processing (Buxton and Benndorf 2013). While there is much to be gained from in-line material characterization and the resulting control both of quality and processing, this article focuses primarily on the camp of pre-concentration of mineral ores."

Jan 1, 2017

By Jimin Su, Enguang Zhu, Kangning Zhang, Yang Li

"The effect of interburden on overlying strata movement during the mining of a lower group coal seam is still a challenge in China. Based on the multiple coal seams in western China, numerical simulation and field tests are applied to study the interburden and overburden movement during the undermining process. This study focuses on the impact of the thickness and structure of the interburden, the proportion of hard rock, and the ratio of the overburden thickness to interburden thickness (OB/IB). In this paper, four typical underground coal mines are simulated for lower seam longwall mining with different interburden parameters. The results indicate that the ratio of the overburden thickness to the interburden thickness is not the dominant actor for multiple seam longwall mining, especially in the mines in western China,which feature shallow depth. The thick and hard interburden could strongly affect the lower coal seam mining process. INTRODUCTION The project background is based on four typical underground coal mines in western China.The information on the overburden and interburden is shown in Table 1. Different overburden to interburden thickness (OB/IB) (Ellenberger, 2009) values of the four coal mines are also studied: 6.2 in Bulianta coal mine, 7.2 in Kaida coal mine, 8.2 in Shigetai coal mine, and 9.4 in Halagou coal mine. The proportions of hard rock in the interburden of the four coal mines are also different: 0% in Kaida coal mine, 70% in Shigetai coal mine, 80% in Bulianta coal mine, and 100% in Halagou coal mine. To be specific: the thickness of interburden are listed as follows: 7m in Halagou coal mine, 6m in Kaida coal mine, 10m in Shigetai coal mine, 28m in Bulianta coal mine. The depth of the upper coal seam are: 66m in Halagou coal mine, 54m in Kaida coal mine, 79m in Shigetai coal mine, 182m in Bulianta coal mine. NUMERICAL SIMULATION UDEC 4.0 is applied in this paper to analyse the overlying strata movement and the interburden failure.(Liu, 2007) This is based on mining in the lower coal seam under the mined-out upper coal seam (Majdi, 2012, Morsy, 2006)."

Jan 1, 2017