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By Edoardo Misano, Magali Schivre, Martino Semeraro, Alain Bochon

"INTRODUCTIONThe Laboratoire Souterrain de Modane (LSM) is an underground research laboratory located in the Western Alps on the French – Italian border. It is located in the middle of the 13km long Fréjus highway tunnel that links Modane (France) to Bardonecchia (Italy) in correspondence of the highest overburden of 1800m. The LSM current activity is mainly based on the investigations about the dark matter and requires very sensitive instrumentation which shall be protected from cosmic rays. To comply with the new legislation about safety in tunnels, the highway tunnels owners agreed in 2007 the construction of a parallel safety tunnel, at an average distance of 50m from the existing tunnel and the laboratory owner CNRS (Centre National de recherche scientifique) also decided to extend the existing laboratory with the construction of a new 17000 m3 cavern allowing the installation of wider and more powerful instruments that could increase chances of success of research. Preliminary studies stated that, considering both geological and functional issues, the most appropriate location for the new laboratory shall be in between the two tunnels and parallel to the existing laboratory (see Figure 1).Hence, the CNRS asked Systra, already in charge of the works supervision of the safety tunnel, to realize the design of the new cavern. The laboratory extension includes the construction of a 40 m long cavern with 300 m² cross section and two smaller tunnels connecting the safety tunnel and the existing laboratory to the new cavern. The minimum distance between the front face of the new LSM and the highway tunnel is about 25 m.The French and the Italian authorities, responsible of the exploitation of the Fréjus highway tunnel, asked the CNRS to develop an accurate study indicating that the construction of the laboratory extension would not have any negative impact on the existing structures of the highway tunnel. The main results of the developed study by Systra are summarized hereafter. The construction works should begin prior to the end of the construction works of the Fréjus safety tunnel in 2018."

Jan 1, 2016

By Yiming Sun, David Tsztoo, Rick Nolting, Adam M. Wirthlin, Rebecca Fusee

"Excavation and initial support of the New Irvington Tunnel presented significant challenges, including rapidly changing ground conditions, heavy ground loads, and squeezing. Such behaviors were anticipated from historic tunneling records of the adjacent Existing Irvington Tunnel, and extensive site investigation, but clearer understanding of their actual extent and causes has resulted from convergence measurements, observations of ground behavior, initial support monitoring and detailed geologic mapping. Time-dependent movements, documented hours to months after excavation in clay-rich rock and in moderately to intensely fractured rock, identified squeezing areas, allowed classification by currently-used predictive methods and added to the list of lessons learned in tunneling such ground. INTRODUCTION In March 2003 the San Francisco Public Utilities Commission (SFPUC) authorized funding for the $4.6 billion Water System Improvement Program (WSIP) to repair, replace, and seismically upgrade its water system. The program consists of 35 local projects located within San Francisco and 48 regional projects located in several counties from the Sierra foothills to the San Francisco Bay Area. The New Irvington Tunnel (NIT), a key component of the WSIP, is located east of Fremont in Alameda County, on the east side of San Francisco Bay. The NIT is a new 18,660 foot (5,689 m), redundant tunnel, 190 to 670 feet (58–204 m) offset from, and subparallel to the Existing Irvington Tunnel (EIT). Built between 1928 and 1932, the EIT was constructed with an unreinforced cast-in-place concrete lining and is vulnerable to damage in the event of a major earthquake along the two closest active faults. The Hayward Fault is located less than a mile west of the tunnel, and the Calaveras Fault is located half a mile east of the tunnel. Although the alignment does not intersect these faults, the shaking and sympathetic displacement along secondary faults that cross the tunnel alignment are potential hazards. The NIT provides a seismically reliable water transmission facility capable of withstanding earthquake damage and maintaining continuous water service after a major earthquake. The NIT also adds system redundancy and provides for operation flexibility of running water through both tunnels, or through one tunnel while the other is out of service for inspections and maintenance."

Jan 1, 2016

By Pedro Alejandro Samané Tuni

El presente texto describe la metodología de investigación adecuada para la excavación subterránea a través de la clasificación geomecánica según: RMR (Bieniawski), Q (Barton), Romana, Deere y Palmstrom, quienes determinan los tipos de sostenimiento y el span de autosoporte para cada tipo de roca e influyen en el método adecuado de excavación según clasificación de excavabilidad. Sin embargo, no se encontró el método adecuado y solo se define cuál de estas clasificaciones son factibles de usar en la excavación de cada tipo de macizo rocoso.

Jan 1, 2016

By J. Noll, D. Yantek, B. Kendall, J. A. Organiscak

"A self-tramming remotely controlled mobile Dry Scrubber (DS) was developed by J. H. Fletcher and Co. under a contract with the National Institute for Occupational Safety and Health’s Office of Mine Safety and Health Research (NIOSH OMSHR) to reduce exposure of miners to airborne dust. NIOSH OMSHR laboratory testing showed that the DS averaged greater than 95% dust removal efficiency with the disposable filters and averaged 88% and 90%, respectively, for the optional washable filters in their pre-washed and post-washed test conditions. Although the washable filters could be reused, washing them generated personal and downstream respirable dust concentrations of 1.2 and 8.3 mg/m3, respectively, for a 10-minute washing period. The DS’s velocity pressure regulated variable frequency drive (VFD) fan maintained a relatively consistent airflow near the targeted 1.43 and 4.25 m3/s (3000 and 9000 ft3/min) airflow rates during most of the laboratory dust testing until reaching its maximum 60 Hz fan motor frequency or horsepower rating at 2610 Pa (10.5 in. w.g.) of filter differential pressure and 3.97 m3/s (8420 ft3/min) of scrubber airflow quantity. Laboratory sound level measurements of the DS also showed that the outlet side of the scrubber was noisier and the loaded filters increased sound levels as compared to clean filters at the same airflow quantities. With loaded filters the scrubber reached a 90 dB(A) sound level at 2.83 m3/s (6000 ft3/min) of scrubber airflow, indicating that miners should not be overexposed in relation to MSHA’s permissible exposure level (PEL) of 90 dB(A) at or below this airflow quantity (1). The DS’s washable filters were not used during field testing because of their lower respirable dust removal efficiency and the airborne dust generated from filter washing. Field testing the DS with the disposable filters at two underground coal mine sections showed that it can clean a portion of the section return air and provide about a 50% dust reduction at the face area downstream of the continuous miner (CM) operation. INTRODUCTION Coal mine worker overexposure to coal and quartz dust continues to be a problem at underground coal mining operations in the U.S. The U.S. Mine Safety and Health Administration (MSHA) recently changed the standard for coal mine worker respirable dust exposure from 2.0 mg/m3 average during an eight-hour shift to 1.5 mg/m3 average over the actual working shift, effective as of August 1, 2016 (1). If more than 0.1 mg/m3 quartz mass is found in the coal mine worker dust sample, the applicable respirable dust standard is further reduced to the quotient of 10 divided by the percentage of the quartz in the sample (1). Over 90% of the mechanized mining units operating in U.S. underground coal mines are continuous mining machines (2). MSHA inspector dust samples from 2009 to 2012 showed that 3.7% of continuous miner operators exceeded the 2.0 mg/m3 dust standard, while 8.8% of these dust samples exceeded the new 1.5 mg/m3 dust standard and 9.7% of these samples exceeded the reduced quartz standard (3). Additionally, roof bolter dust samples at these mechanized mining units during this same period have exceeded the 2.0 mg/m3, 1.5 mg/m3, and reduced quartz levels at 1.1%, 3.7%, and 10.6%, respectively (3)."

Jan 1, 2016

By Tsunenori Shibata, Kazunori Jimbo, Kaoru Toya, Masafumi Matsumoto, Jinya Mitsui, Toshinori Tsuji

"The Toyama Line is under construction as a natural gas pipeline with a length of 102 km from Itoigawa City to Toyama City. A 2 km-long tunnel section of the pipeline that we are reporting here is being excavated in a mountain area away from an urban area. The geology under which the tunnel is constructed is collapsible fractured breccia slate and Holocene sandy soil. Other tunnels of the Hokuriku Expressway and Hokuriku Shinkansen are in service above the tunnel route. From the starting shaft on Toyama side, conventional tunneling was adopted to facilitate excavating the base rock layer and maintain enough distance from the Hokuriku Expressway tunnel. From the starting shaft on the Itoigawa side, TBM tunneling was adopted to cope with the unconsolidated soft ground for a 200 m-long section from the shaft. We will discuss the issues and countermeasures concerning the selection of a tunnel route and excavation methods, performance of both conventional and TBM tunneling, and underground connecting of these tunnels excavated by conventional (NATM) and TBM methods under a high groundwater pressure up to 1.2 MPa. INTRODUCTION AND BACKGROUND The International Petroleum Exploration Teiseki Co., Ltd. (INPEX) is constructing a high-pressure main pipeline network in the Toyama Prefecture area to promote the use and reliable supply of natural gas as shown in Figure 1. As part of the Toyama line project that has a total length of 102 km, A-1 construction, the nearest section to the tunneling starting point in Itoigawa City, where various tunnel excavation methods have been adopted to install the high-pressure pipeline 20 inches in diameter, a 2 km tunnel in the A-1 construction section discussed here is to be excavated by conventional and TBM methods in a mountain area. Based on environmental studies such as traffic jams due to frequent traffic of heavy vehicles disposing of soil, and the effects of dust, noise and vibration during construction, we selected the route to install the gas pipeline in a mountain area as shown in Figure 2, where the impact on the surrounding environment could be minimized."

Jan 1, 2016

"Metallurgical process development in greenfield projects must define the comminution flowsheet and establish the equipment sizes that are required to deliver the project design criteria. These are critical steps that heavily influence the financial performance of the project, requiring a detailed understanding of the ore properties of the project resources and the best practice methods to size comminution machines. This paper reviews current practices for determining the ore characteristics relevant to comminution circuit design. Particular attention is given to the design of sampling and testing programs, and the methods commonly applied to size crushers and mills for conventional size reduction applications in mineral processing. IntroductionMetallurgical process development in greenfield projects requires the selection of a comminution flow sheet and must establish the equipment sizes required to deliver the project design criteria. This necessitates a detailed understanding of the ore properties that define the project resource. For brownfield projects the same objectives may apply for plant expansions, or the project objective may be simply to define the capacity and operating cost of an existing facility for a new ore source. The process development phase in either instance will typically comprise the following key activities:• Geometallurgical classification and sampling of the ore deposit or deposits.• Determination of comminution energy requirements.• Benchmarking similar projects.• Identification of flow sheet options.• Equipment selection and sizing.This paper is concerned specifically with process development testing and will as such focus on the first two activities on the list: sampling and testing of the deposit. The discussion will focus on testwork programs to support the design of comminution circuits commonly in use in mineral processing today, specifically crusher, tumbling mill and stirred mill technologies.It is important that any testwork program is designed giving consideration to the types of flow sheets that are viable for the project, and the data that will need to be generated to support the final equipment sizing. Designing a testwork program to only provide information about one particular type of flow sheet will not allow sufficient information to be generated for a rigorous trade-off analysis of options, and may therefore preclude financial optimization of the project. Testing programs should be designed to collect sufficient data to ensure that any backtracking at a later stage to fill in missing information is minimal."

Jan 1, 2016

By S. Banisi, M. Maleki-Moghaddam

Direct observation of charge shape and its motion in industrial mills is not possible; therefore, a combination of analytical and physical studies is used to determine charge trajectory. Software packages, which predict charge motion consider only the outermost layer of charge (single ball) and ignore the charge and the interactions of grinding elements. In the new version of the GMT (Grinding Media Trajectory) software, the effect of liners specification and bulk load on charge shape and trajectory are considered. The charge trajectory was measured in a laboratory mill with the diameter of 100 cm and length of 21.5 cm with the transparent end and compared with that of the old version of GMT. Four types of polyurethane rings were accurately machined to scale down the liners arrangements at two industrial mills. The model mill was operated at 55, 70 and 85% of the critical speed for five levels of mill filling (10, 15, 20, 25% and 30% by volume). The experiments indicated that the end walls effect was negligible for the model mill with the length of 10.8 cm and beyond. The proposed relationships to correct the trajectory and charge shape were validated by using the new liner of the Gol-E-Gohar iron ore company AG mill. The positions of shoulder, toe, toe departure and impact points were predicted with the relative errors of 5, 0.7, 2 and 0.2%, respectively. The GMT software was updated with the new relationships. The results of GMT simulation indicated that when the lifter face angle increased from 7 to 30°, the distance between the charge impact point and the toe decreased from 40.1 to 11.2° for 30% filling. The change in the position of the impact point meant increasing the probability of charge impacting the toe, not the liner which favored more efficient comminution practice.

Jan 1, 2016

By H. Huang, R. N. Gow

"In Part I, Gibbs’ phase rule was applied to mass-balanced EH-pH diagrams for the Cu-As-S-H2O system. The diagrams were generated using the stoichiometry of enargite as a basis. In this study, the calculations were expanded to cover the stoichiometries of three other Cu-As-S minerals – tennantite, sinnerite and lautite – and compared with enargite. Stability regions within the resulting EH-pH diagrams were found to change with stoichiometry such that a particular mineral would predominate if its stoichiometry was used in the calculation. Solution speciation was also found to vary, with thioarsenate being the best example. This stoichiometric effect helps to explain results reported in the literature and would be difficult to realize if it were not for mass-balanced calculations. IntroductionA comprehensive thermodynamic review has been conducted on the aqueous copper-arsenic-sulfur (Cu- As-S) system (Gow et al., 2014, 2015a, 2016b; Gow, Huang and Young, 2016c). Data on the free energies of more than 100 species were collected from various authors, and thermodynamic databases collated to produce mass-balanced EH-pH diagrams using the thermodynamic equilibrium calculation software STABCAL (Huang, 2014). The full database is listed and discussed in Gow et al. (2015a). Diagrams were generated for enargite and confirmed with Raman spectroscopy using bulk mineral electrodes in order to identify reactions spectroelectrochemically. Theoretical calculations agreed well with the experimental results under alkaline conditions (Gow et al., 2015a), acid conditions (Gow et al., 2014) and alkaline sulfide leaching conditions (Gow et al., 2015b).In the present study, additional mass-balanced EH-pH diagrams were generated by changing the Cu-As-S stoichiometry from enargite (Cu3AsS4) to tennantite (Cu12As4S13), sinnerite (Cu6As4S9) and lautite (CuAsS). Regions for the thermodynamically stable species were shown to change with the four different mineral compositions. Potential leach conditions, both for co-dissolution and selective dissolution techniques, were examined for differences in predominant species according to changing copper-to-arsenic ratios, sulfur compositions and sulfur oxidation states."

Jan 1, 2016

By Andrzej Luszczkiewicz, Magdalena Duchnowska, KGHM Polska Miedz S. A., Witold Pawlos, Jan Drzymala, Alicja Bakalarz, Przemyslaw B. Kowalczuk

Numerous data in the literature confirm that the chemical composition and consumption of grinding media influence electrochemical properties of flotation suspension as well as effectiveness and selectivity of upgrading processes. During a milling process, attrition of grinding media is observed. Depending on the susceptibility to abrasion, the grinding media influence, to a different extent, the redox potential, pH as well as flotation efficiency. As a result, different upgradeability of sulfide minerals is observed. The paper presents laboratory scale flotation results, obtained for the copper sulfide ore from Polkowice Region of KGHM Polska Miedz S.A. in Poland ground in the presence of forged steel, highchrome iron and stainless steel as the grinding media. The investigated flotation feed contained 36 g/t (ppm) of silver and 1.86 % of copper. Several flotation tests were conducted using fixed amount of frother and a mixture of sodium ethyl and isobutyl xanthates as the collector at three different doses of 75, 100 and 125 g/t. A comparison of the obtained results confirmed that the application of grinding media with different chemical compositions influenced the electrochemical properties of the suspension and recovery of silver and copper in the final concentrate. The highest values of redox potential were observed for the stainless steel as the grinding medium. Moreover, in the presence of this type of grinding media, regardless of the collector dosage, the best silver upgrading was observed. For the forged and high-chrome iron media, the recovery of silver depended on the collector dosage. It is indicated that higher levels of the redox potential, together with smaller amount of iron released from the grinding medium, improve the flotation of the silver-bearing mineral compounds from the copper sulfide ore.

Jan 1, 2016

By R. V. Fox, L. K. Sinclair, D. L. Baek

"In this study, rare earth elements were recovered from bastnasite concentrate and waste fluorescent lamp phosphors using supercritical carbon dioxide extraction with a nitric acid/tributyl phosphate adduct. Several pretreatment methods were used to alter the crystal structure of the source materials, and thus improve rare earth element recovery. Pretreatment methods included 1) dry roasting of the source material at 730oC, 2) decomposition with 50% sodium hydroxide solution at 150oC for 4 hours, and 3) decomposition with 12 M sulfuric acid at 300oC for 4 hours. Treated and untreated samples underwent supercritical extraction at 24 MPa and 65oC for 1 hour. Untreated bastnasite and phosphor samples showed <10% rare earth element recovery, but sodium hydroxide digestion resulted in >60% recovery for most rare earth elements. Dry roasting of the bastnasite concentrate was also effective, resulting in >60% recovery for cerium.INTRODUCTIONRare earth elements (REEs) consist of the 15 lanthanides, scandium, and yttrium. Scandium and yttrium are included because they are in the same group as lanthanum, appear in many of the same ore deposits as the rest of the lanthanides, and exhibit many similar chemical properties. REEs are used in a wide array of applications including electronics, magnets, catalysts, glass, and solid-state lighting (Xie, Zhang, Dreisinger, & Doyle, 2014). Because of China’s continued dominance of worldwide REE production, the United States Department of Energy has sought to diversify domestic supplies of REEs (United States Department of Energy, 2011). A key part of this strategy is the development of improved extraction methods for both ores and recycled sources.Supercritical fluid extraction (SFE) is a promising technology for extraction and separation of rare earth elements. Contact with an acid adduct dissolved in supercritical carbon dioxide allows for the rapid extraction of REEs from solid matrices. Supercritical CO2 has several potentially useful properties as a solvent, including high diffusivity and the ability to tune solvation properties by adjusting pressure. Such tunability may have applications in separating the REEs once they have been extracted from the solid phase. Tributyl phosphate/nitric acid adducts (TBP:HNO3) are a particularly promising class of adducts for SFE extraction of rare earth elements. Using TBP:HNO3 adducts in supercritical CO2, several researchers have successfully extracted REEs from their oxides (Wuhua, Pijia, & Yongjun, 2010; Zhu, Duan, Xu, & Zhu, 2009). However, there is a complication in applying this technique to many types of ores and recycled sources: REEs are often locked in refractory minerals which are resistant to acid attack, resulting in limited recovery in supercritical extraction."

Jan 1, 2016

By N. Weidner, V. A. Samaranayake, K. Awuah-Offei, S. Que

"This research sought to facilitate improved stakeholder (community) analysis using discrete choice theory (DCT). The work considered 16 project attributes and four demographic factors. The discrete choice experiment was conducted in Salt Lake City, Utah to illustrate the usefulness of DCT in mining stakeholder analysis. The data was used in discrete choice modeling of individual preferences. The approach answers three important questions for enhanced stakeholder analysis: (1) What are the factors that affect individual preferences? (2) What is the effect of demographics on individual preferences? (3) What is the value of environmental and social impacts to individuals in the community? INTRODUCTION Stakeholder analysis is crucial for effective stakeholder engagement because it is important to identify and characterize stakeholders in order to effectively engage in dialogue with them. This is not only true for all stakeholders but true for characterizing the members of a particular stakeholder. The local community is usually the largest and most diverse single stakeholder group. Also, the local community is perhaps the most important stakeholder group. Thus, analysis of the local community is essential for project management. Conventional mining stakeholder analysis is a three-step process, which involves evaluating: (1) each stakeholder’s view of the project (positive, neutral, or negative); (2) how influential each stakeholder is (high, medium, or low); and (3) how they will be impacted by the project (high, medium, or low) (ICMM, 2012). The results of this evaluation are documented in a stakeholder analysis matrix (Table 1), which is used to classify the stakeholders into three groups: highly influential supporter of the project, neutral about the project, and highly influential opponent of the project. This process can be used to describe groups of stakeholders (e.g. community, non-governmental organizations, etc.) or individuals making up a particular stakeholder group (e.g. members of the local community)."

Jan 1, 2016

By J. W. van der Merwe, A. S. Bolokang, M. J. Phasha, V. J. Matjeke, C. Moopanar

"Excessive wear rates on railway wheels can result in rolling-stock derailments. If wear is detected early the possible derailments can be prevented by prematurely replacing wheelsets, although the inventory cost and maintenance downtime remain a challenge. In the current study, wheels were introduced and monitored in-service for two years to investigate the cause of excessive wear rates. The wear rates and stresses were calculated for the wheels suitable for a maximum load of 26 t per axle. Microstructural and mechanical properties were analysed. As expected, the general microstructure of all the wheels tested was pearlitic. Although all the wheels complied with the tensile strength requirements, stress calculations confirmed material distortion on excessively worn wheels whereas trial wheels revealed yield strength exceeding the yield criterion. High wear rates observed on the wheels were a result of low yield strength relative to the load per axle. The typical wear mechanism found was due to a combination of rolling contact fatigue and abrasive brake wear. Despite compliance of the wheels with existing requirements regarding material and mechanical properties (hardness, ultimate tensile strength), it is recommended that the yield strength must also be taken into consideration as a critical parameter.IntroductionRailway wheels are used to support the wagon mass and guide the wagon along the tracks (Park, 1974). The wheels and rails must be able to tolerate the applied tangential forces in order to effect wagon dynamic performance and reduce material deformation (Ghidini et al., 1994; RSE_TE_SPC_0045, 2011; AAR M107/M 208 Specification, 2011. Over the past ten years, the South African coal wagon maintenance depot has experienced excessive hollow wheel wear rates on the heavy haul line wheels. The maximum load of Jumbo wagons on the coal line is 104 t, or 26 t per axle. Although the maintenance intervention cycle for wheelsets was two years, between February 2011 and August 2012 some wheels experienced excessive hollow wear. Hollow wear is regarded as wear exceeding 2 mm on the central portion of the wheel tread (RSE_TE_SPC_0045, 2011). This happened despite the fact that these wheels were manufactured and certified according to the requirements of AAR M107/208 standard for carbon steel wheels (AAR M107/M 208 Specification,. 2011) and the local wheel RS/ME/SP 021 standard specification (RS / ME / SP / 021 REV 5 (2013). The AAR standard only specifies a minimum hardness as a required mechanical property and the local standard specifies hardness and minimum tensile strength only. In general, an increase in hardness will improve the rolling/sliding wear resistance of steel. This relationship of hardness and wear resistance was found to be true only in a situation where solid and similar alloys are in contact (Singh, Khatirkar and Sapate, 2015). The sliding wear resistance of a material is usually estimated using Archard’s equation (Liu and Li, 2001)."

Jan 1, 2016

By Markus Papst, Denise Millier, Daniel Beckers, Axel Preusse

"At an open-pit lignite extraction mine in Germany, groundwater has to be pumped over a large area, which leads to subsidence at the surface. As long as the geology of the area of influence is homogeneous, the subsidence is uniform and has marginal influence on buildings.Since the geology of many regions is characterized by faults, there are different rates of subsidence along those faults, which can lead to considerable consequences. Those different rates of subsidence on both sides of a geological fault are associated with the structure of the geology and soil mechanical properties. Horizons with various thicknesses and types of soil are affected differently by the groundwater pumping because of the offset of the faults, and thus react dissimilarly to dewatering.The smaller the grain of the geological horizon, the stronger the chance of shrinking, which leads to a stronger effect at the surface; therefore, dewatering impacts on clayey soil are different to those on sand and gravel. Regions consisting of meadows with turf inclusions are endangered as well; compared to the surrounding geology, those areas react in an entirely different way to water removal, which leads to immense differences in subsidence.The differences in area and respective subsidence impacts, as well as if it is possible to localize those areas, is an issue which needs to be analyzed. Furthermore, detailed mapping can help in the development of future forecasts about those subsidence differences and can also help with monitoring geological faults. In the context of subsurface spatial planning, this mapping has to be kept under review medium- to long-term.INTRODUCTIONThe utilization of underground mining is of increasing significance and of high interest, both for the common good and for future generations. For decades, humanity has been extracting resources from the subsurface, and salt, coal, lignite and water - just to mention a few resources - have been extracted from underground (Sailer, 2013)."

Jan 1, 2016

By Grigor Mishev, Georgi Petrov, Benjamin Cebrian

Before designing a single blast or all the blasts on a pit level, it is critical to assess the main goal on each. To do this, a series of constraints must be taken into account: wall protection, vibration control, flyrock hazards, fragmentation required, desired displacement as well as economy, equipment efficiency. The tool to do this is the Blast Master Plan. Many mines fail to integrate on its elaboration key stakeholders such as planning, operations, geology/geotechnical and milling departments. Designs not only have to provide consistent behavior of the blasts, but have to make sense all in one with the geological and geotechnical conditions as a starting point. Once blasts are designed under an organized set of priorities, and complemented with quality controls, optimization is possible on a large scale.

Jan 1, 2016

By W. Griffith

"While oxalic acid precipitation practices are commonly applied on purified rare earth elements (REEs) pregnant leaching solutions (PLS), few efforts have been reported using oxalic acid (OXA) to recover REEs directly from untreated PLS. High oxalic acid demand is the most significant issue in all these direct oxalic precipitation (DOP) practices. Preliminary research on DOP of REE from a dilute PLS originating from an acid bake followed by water leaching was conducted. At 75°C, the oxalic acid demand was between 12 and 18 times the stoichiometric requirement for complete REE precipitation. Conducting DOP at 25°C had superior REE recovery but the product purity and filterability declined. Between 75°C and 100°C, REE recovery increased with increasing temperature. When sodium hydroxide was used to adjust the pH during DOP, in the range of 0.5 to 1.5, higher pH benefited REE recovery. Using ammonium hydroxide in place of sodium hydroxide, the REE recovery was reduced by close to 5%. Sodium chloride addition to the PLS was also investigated and the results showed that at both 75°C and 25°C, the REE recovery was enhanced substantially. At 25°C, when the oxalic acid addition was controlled at 4.7 times the stoichiometric requirement, the overall REE recovery reached 95% with the addition of 240 g/L NaCl. Other reagents such as KCl, NH4Cl also showed significant enhanced REE recovery at the same oxalic acid addition. The addition of sodium sulphate appeared to largely enhance the precipitation of LREE but inhibited the formation of HREE oxalate. All results indicate the formation of rare earth double salts may play an important role in REE DOP sulphate media.INTRODUCTIONThe conventional routes for recovering rare earth elements (REEs) from a sulphuric acid pregnant leaching solution (PLS) involves an initial purification step for removal of iron, aluminium for example by precipitation through neutralization, followed by precipitation of REEs as hydroxide, oxalate or carbonate salts, or by bulk solvent extraction for REE recovery (Xia, 2013). Another route was used by Bayan Obo in their historical flowsheet, where the PLS was first subjected to double sulphate precipitation, then the remaining REEs, mostly heavy rare earth elements (HREE), were recovered by oxalate precipitation (Li, 2011)."

Jan 1, 2016

By R. V. Kumar, C. Schwandt, S. Subramanian, S. Sampath, S. Vimalnath

Waste waters and industrial effluents containing toxic heavy metals such as Pb, Hg, As and Cr, beyond permissible limits (0.1 ppm, 0.01 ppm, 0.02 ppm and 0.05 ppm, respectively) (WHO, 2011), pose serious threats to the ecosystem, when discharged into the environment. It thus becomes imperative to monitor the concentration of the toxic heavy metals and treat them before discharging. In this study with the above objective in mind, a microbial sensor has been developed using P. aeruginosa cells drop coated onto a carbon paste electrode (CPE) for the detection of Pb(II) ions in aqueous solutions. Detailed biosorption experiments confirmed that complete bioremoval of lead could be achieved using P. aeruginosa cells under optimum conditions of pH and biomass loading. For the electro-analytical determination, the Pb(II) ions were initially preconcentrated on the P. aeruginosa modified CPE, reduced and then anodically detected with oxidation of Pb0 using differential pulse anodic stripping voltammetry (DPASV) technique. All the experiments were carried out in the presence of 0.1 M sodium acetate buffer and KNO3 as background electrolyte. The parameters namely pH, scan rate, biomass loading, deposition potential, deposition time and concentration of Pb(II) ions were optimized for the biomass modified CPE, to obtain maximum voltammetric response. Under the optimized conditions of pH 5.6, scan rate of 0.008 V/s, biomass content of 1.7–1.8×109 cells/mL, deposition potential of –1.2 V, and deposition time of 500 s, the developed microbial sensor showed a linear response for the peak current between 0.5×10-5 M and 1×10-8 M of Pb(II) ions with the R2 value of 0.9979. The lowest limit of detection (LLOD) was determined as 2.4×10-7M of Pb(II) ions (0.05 ppm). The redox mechanisms of Pb(II) ions on the P. aeruginosa modified CPE surface are discussed.

Jan 1, 2016

By J. Weyer

"Colored gemstones are most often mined in small scale artisanal mining operations. Sri Lanka is well known as source for precious stones since thousands of years. Gemstones are mine in small open pits, directly in rivers (river dredging) and in underground mines. Almost all mined deposits are alluvial deposits. PRECIOUS STONES AND DEPOSITS Precious stones from Sri Lanka are well known for thousands of years. Tales and legends from Arabia, India, China and reports from discoverers like Marco Polo describe the fabulous stones from Ceylon which was the name for Sri Lanka before 1972. Already 1000 BC King Salomon got valuable gemstones from the legendary Queen of Sheba on her visit to Jerusalem. Paintings (frescoes) of the “cloud maidens” with huge gemstones can be seen at the “mirror walls” of the Sigiriya rock fortress - one of the eight World Heritages Sites of Sri Lanka.And even today some of the most valuable and most desired gemstones come from Sri Lanka. The term “Ceylon Sapphire” stands for an excellent royal blue color of high quality corundum from Sri Lanka. Reason enough to look a bit closer how these gemstones are mined. Sri Lanka has rich gemstone deposits which are mined underground, in small open pits or directly within a river. Some of the primary deposits in magmatic and metamorphic rock are also known, but most gemstones are mined in secondary alluvial deposits. Gem bearing deposits can be found in a band from NW to SE. Highly probable deposits and main mining areas can be found around Ratnapura – the city of gems, down to the coast (Matale) and up to the region around Elahera. These secondary deposits are mostly thin layers of gravel and sand, so called “illam”. The depth can vary between some dm to 10 25 m or even almost 40 m. But the average depth is about 12 m. Gemstone mining is controlled, licensed and regulated by a special authority – the National Gem and Jewelry Authority - which was founded in 1993. Another task of this authority is the promotion and development of the gemstone industry and the control of import and export of gemstones. Any violence of the NGJA law can lead to a fine or even up to 5 years imprisonment. To increase the confidence in the gemstone industry the Authority offers a unique service to foreigners. All bought gemstones can be tested free of charge in certain laboratories in Ratnapura and Colombo. So visitors can be sure they got no imitations, wrong stones or even synthetic stones or glass. It was said that detected synthetic stones will be destroyed and the seller will do all he can to replace the stone with the right stone. Otherwise he will lose his license."

Jan 1, 2016

"A commercially available Through-the-Earth (TTE) communications system was evaluated at an active underground longwall mine in West Virginia. This TTE system uses electric field (E-field) sensing to send text based communications using two separate antenna arrays connected in parallel. Each antenna array is composed of interconnected, grounded metallic rods or other such structures. Two-way communication between subsurface locations was investigated in this study using various antenna configurations. This field study was conducted as a part of a larger multi-site evaluation of available TTE systems in an effort to determine their operational sensitivity. INTRODUCTION Wireless, Through-the-Earth (TTE) communication technology is designed to achieve point to point communication through solid strata using very low frequency (VLF) and ultra-low frequency (ULF) electromagnetic waves. This ability allows TTE communication to function without the need for intermediary communications infrastructure, such as repeaters. As a result, such communication systems have the potential to provide reliable, robust communications between surface and underground personnel. Exploration into the use of TTE technology for this purpose dates back to the 1920s (Jakosky and Zellers 1924; Pittman, Church and McLendon 1985), but U.S. permissibility requirements slowed the development of TTE equipment for widespread implementation (Durkin 1980; Pittman, Church and McLendon 1985). One of the primary challenges in producing wireless TTE communications is the counteraction of signal attenuation when propagating through solid strata (Barkand, Damiano and Shumaker 2006; Wadley 1949). The long wavelengths of TTE transmissions make them well-suited for reducing the rate of attenuation. However, even when operating within the VLF to ULF range, the performance of TTE systems is still affected by geologic and anthropogenic factors (Geyer 1973; Geyer and Keller 1976; Geyer, Keller and Ohya 1974; Jakosky and Zellers 1924; Large, Ball and Farstad 1973). Although commercially developed TTE systems have demonstrated the ability to communicate through a variety of conditions, their range and performance have been highly varied (Barkand, Damiano and Shumaker 2006; Geyer and Keller 1976; Geyer, Keller and Ohya 1974; Ilsley, Freeman and Zellers 1928; Jakosky and Zellers 1924; Yenchek et al. 2012)."

Jan 1, 2016

By Charles Zdazinsky

"The Multiple Seed Waveform (MSW) blast vibration model, a type of waveform superpositionmodeling developed by Orica Inc., uses vibration data that is collected from a signature hole blast tocharacterize the ground’s seismic properties and determines the ground resonant frequency andfrequency range that is well supported by the ground. Additionally, the MSW model uses thisvibration data as input parameters to predict the resultant dominant frequency of a production blast. This information may in turn be used in conjunction with precise timing control to target theoptimum dominant frequency which promotes ground control."

Jan 1, 2016

By Carlos Henrique Turolla Maia, Ulrich Maidl, Marc Comulada, Julio Claudio Di Dio Pierri

"Pure sands are typically the domain of slurry shields due to their high permeability and their granular characteristics. However, the Earth Pressure Balanced (EPB) shield machine technology has advanced in recent years with improved conditioning agents and shield machines that are equipped with slurry injection facilities and alternative mucking methods. These new so-called hybrid EPB machines have steadily increased the range of application of the EPB technology. The contribution discusses the capacities and operational features of hybrid EPB vs. slurry shield technology in pure sands. At the example of the Metro Line 4 in Rio de Janeiro (Brazil), the contribution shows that hybrid EPB tunneling in pure sands is possible and it is compared with a state-of-the-art slurry shield project as the KASIG project in Karlsruhe (Germany). Furthermore, the control of the support pressure by means of foam conditioning and slurry injection in conjunction with a close, real-time monitoring of machine parameters is discussed. INTRODUCTION Slurry shield and EPB technologies have both undergone significant developments in recent years, leading to the use of parts of one technology in the other and even to completely hybrid systems. Also the ranges of application (see recommendations by DAUB (DAUB 2010)) of both technologies have been shifted far beyond their original limits and are largely overlapping by now. Nevertheless, the basic principles of face support remain unchanged. Exploiting the possibilities of process data analysis (Maidl 2014), the interactions between the ground and the shield machine are a matter of research and have been intensely investigated. PRINCIPLES AND CALCULATION OF FACE SUPPORT PRESSURE Figure 1 shows the principles of two approaches for the determination of required support pressures: kinematic methods and numerical methods. Kinematic methods that are employed for the assessment of face stability only consider the situation in front of the TBM. The required face support force is determined by means of an assumed failure wedge that would form in ultimate limit state. Based on the ground properties, the vertical surcharge and the self-weight is transformed into a horizontal force along a virtual sliding surface. This horizontal force is to be balanced by the face support. The calculation results are amended by respective partial safety factors for water and earth pressure and the method-specific support pressure fluctuations are added."

Jan 1, 2016