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By Jun Dai

Based upon research findings from several countries, the combination of microwave and mechanical means to break hard rock holds promise for the future. To achieve this goal, it is essential to understand the laws governing strength reduction of hard rock, such as granite, induced by microwave irradiation. Two aspects to consider are: 1) laws associated with the tensile strength of hard rock after microwave irradiation and 2) the sensitivity of different types of rock strengths to microwave energy. In this study, granite with a range of tensile strengths was exposed to microwaves for various time periods to compare the response of rocks with different strength values exposed to the same microwave irradiation. In addition, a method based on hotspots is presented to explain the mechanism by which granite strength is reduced by microwave irradiation. Granite extracted from Qinling Mountain in Shaanxi Province, China is used in the research. ?50 × 50 mm cylindrical granite specimens were exposed to microwaves at a specific power level. The strength values of the heated granite specimens were compared with those of unheated specimens. Through the comparison and analyses, relationships were determined between 1) reduction in granite strength and microwave irradiation time period, and 2) granite strength and sensitivity to a given energy of microwave irradiation. Finally, a mechanism to explain the experimental results is proposed. Research findings will aid in the design of a microwave + machine rock-breaking system for use in rock breakage in underground mines at depth and for future mine applications on earth and other planets. In addition, the experimental approach could be used to test other rock types to further our understanding of rock damage induced by microwave irradiation.

Aug 1, 2013

By S. M. J. Mirazimi, F. Rashchi

Recovery of vanadium from LD (Linz-Donawits) converter slag was evaluated by means of microbial leaching. Vanadium leaching was performed in two stages. In the first stage, the bacteria were grown in a culture medium and in the second stage; vanadium containing slag was added to the metabolites produced by bacteria. Bioleaching was performed using heterotrophic bacteria Pseudomonas Putída. Control tests without bacteria inoculation were also performed and the results were compared with bioleaching outcomes. Optimal conditions for the bioleaching of vanadium containing slag were determined.

Jan 1, 2011

By Shengwu Song, Xuemin Feng

Jinping I hydropower station is located in Sichuan Province in Southwest China. It is built on the Yalong River as a controlling cascade hydropower station in the middle and lower reaches, with power generation as its major function. Jinping I arch dam concerns many engineering issues and has attracted worldwide attentions due to its huge scale and unique settings. It is one of the most challenging projects in China with its 305 meters high arch dam and complex geological conditions for construction, including large-scale tectonic faults, intensively unloaded rock masses and geological asymmetry in its foundation. At present, the concrete arch dam construction has been completed and preliminarily impounded, most of the foundation treatments have been implemented, and four of six generator units had been put into operation in July 2014. In this paper, the analytical methods, design concepts, treatment measures and technical features of strengthening the geological defects in the dam foundation will be presented. Upon geological investigation into the dam foundation, a few large-scale weak discontinuities are observed. The rock masses in the left dam foundation are intensively unloaded, approximately to the horizontal depth of 150–300 m. These serious geological defects lead to a geological asymmetry on the left and right banks, and thus some major difficulties of dam construction are encountered. The influences of geological defects on the dam construction and safety are analyzed comprehensively, followed by the concepts and methods of treatment design. Based on this, the treatment methods of the weak rock masses and discontinuities are carefully determined by numerical analysis and scheme optimization, including the concrete cushion, concrete replacement grids, drainage system, anti-seepage curtains and consolidation grouting, which work together to enhance the strength and integrity of the dam foundation. Evaluations and calibrations through geo-mechanical model tests in combination with field monitoring results in early impoundment period show that the arch dam and its foundation are generally stable and function normally, which suggests that the research methods and treatment design schemes are reasonable and effective. The proposed treatment methods and concepts in the context are helpful for similar complex rock projects.

Jan 1, 2015

By B. Van den Bogaert, K. Binnemans, T. Van Gerven

Europium is one of the most critical rare-earth elements due to the limited supply of this element combined with a high demand for red lamp phosphors. Therefore, the recycling of europium from end-oflife lamp phosphors has become increasingly important. Photochemical reduction of europium(III) to europium(II) and subsequent removal from rare-earth mixtures by precipitation as EuSO4 is a very selective and efficient method to recover europium from binary europium/yttrium solutions. It is shown that full separation of europium and yttrium is feasible from laboratory prepared non-equimolar Eu/Y mixtures up to a ratio of 1/20, which reflect the composition of red lamp phosphors. Optimal conditions were determined at pH 4 with isopropanol as a radical scavenger, which is a less harmful and toxic compound than the commonly used formic acid scavenger. Europium removal efficiencies of more than 95% were achieved, with a purity of 98.5% of the EuSO4 precipitate. The irradiance of the used light source, expressed in mW/cm2, has a large impact on the illumination time needed to remove europium from the solution. It is observed that higher irradiance results in a shorter induction time, i.e. a period during which virtually no europium is removed, and a faster removal rate once the induction time has passed. The photochemical separation technique was applied to recover europium from leached industrial red lamp phosphor (YOX) powder, with a Eu/Y ratio of 1/30. Europium recovery of 50% was reached with a purity of 96%, proving the feasibility of this method for the recycling of europium from end-of-life lamp phosphors.

Jan 1, 2016

By P. Cavanagh

Summary This paper discusses the fundamental principles which allow the development of a new method for studying the deformation and failure of metals in terms of 'internal microstrains'. Internal microstrains mechanical and magnetic properties are defined and their influence on of metals is outlined. A research programme at present in progress will determine whether magnetic measurements of internal microstrains give sufficiently accurate values for predicting the performance of metals under service conditions. These magnetic test techniques are also being used to detect the beginning of plastic deformation and to trace the development of deformation processes and failure. Results of the experimental work in each field will be published. Introduction Any attempts are being made to develop a complete theory embracing the mechanical behaviour of metals. In spite of the amount of experimental data available, the theoretical approach is rather difficult, since most of the mechanical properties of a metal are determined by deviations from the pure chemical composition or the perfect crystal. Both types of deviation are difficult to reproduce experimentally and to describe theoretically. In general, there are three main avenues of approach to the problem being followed today.

Jan 1, 1950

By J. K. Szymanski

"RÉSUMÉPour maintenir de bonnes performances technique et économique dans l’exploitation par chambres vides (open stope) il est primordial d’assurer un contrôle efficace des limites réelles des chantiers d’abattage. C’est pour cette raison que, de plus en plus souvent, les opérateurs miniers utilisent un dispositif de laser (Cavity Monitoring System: CMS) qui permet de mesurer les dimensions réelles de chantiers en vue de calculer principalement la dilution et les pertes du minerai ainsi que d’autres paramètres. Malheureusement, il n’existe présentement aucune méthodologie commune, qui permettrait d’interpréter ces résultats selon les mêmes critères pour faciliter d’évaluations juste et précise de la réalisation par rapport à la planification en vue d’en apporter de corrections, dans les différentes opérations minières, si nécessaire. Dans la première partie du présent article on discute les principales séquences d’exploitation utilisées dans l’extraction par chambres vides. Par la suite, à l’aide des sections transversales et longitudinales on illustre toutes les phases des travaux miniers. Ceci en vue de permettre au lecteur de comprendre mieux c’est qui peut se passer effectivement dans les chantiers d’abattage. Par après on donne les définitions générales de principaux facteurs de performance technique. Finalement, l’exemple numérique, élaboré à partir des résultats de l’arpentage au laser effectué par la mine Bousquet 2 dans un chantier d’abattage, donne les détails concernant les définitions ainsi que les valeurs de nombreux facteurs de performance technique, qui pourraient être utilisés, par après, par les opérateurs miniers dans le suivi de leurs exploitations souterraines."

Jan 1, 1997

By L. P. Connolly, M. J. Fraser

"Hydraulic transport of solids has long been an important technique in mining and beneficiation. More recently, slurry pipelines have proved to be economic for longdistance overland transport of many commoditieis, including iron ore concentrates and coal. Now, the Marconaflo system brings the many advantages of hydraulic transport to bulk storage, loading, transportation and unloading of ships and other carrying equipment, thus providing important new means for delivering mineral commodities to market. In this paper, the authors describe the Marconaflo system and the potential economies which can be realized when applying it for loading, transporting, storing, reclaiming and blending a variety of mineral commodities, using several commercial installations as examples."

Jan 1, 1972

By M. Massinaei

Recently constructed circuits have included multiple stages of columns in a variety of applications, from roughing to cleaning. The Miduk copper concentrator (in south-eastern Iran) is one of the unique mineral processing plants which use column flotation cells as rougher. As the bulk of final concentrate is produced by rougher columns, optimized metallurgical performance of these cells is crucial. This paper will present the study and optimization of, a froth washing system of columns. For this purpose, the cross-sectional area of orifices was increased and their orientation altered. Concentrate assay for copper and silica, in addition to bias rate were found to be the assessment criteria. Modification of the wash water system resulted in increasing the purity of rougher and final concentrate. Negative bias and short-circuiting of wash water into the concentrate launder were the main causes of improper froth zone washing in the former system.

Jan 1, 2007

By Rolf Andreas Lauten, Adam Pratomo, Dani Ramdani, Helminton Sitanggang

A universal challenge for the mineral processing industry is the diminishment of high grade ores. Instead, low grade ores, sometimes also containing problematic gangue minerals is the reality. With lower head grades the industry has to put more effort into processing to maintain the output and achieve suitable recoveries. In an effort to reduce the impact of declining head grade, a biopolymer was evaluated as an additive in the gold leaching operation at Antam Pongkor in Indonesia. Laboratory testing revealed that biopolymer usage lead to an increased gold recovery without apparent negative impact on the other parts of the process. Further plant trials revealed both a recovery increase around 1.3% and higher throughput (9%) in the presence of the biopolymer. Some scenarios that can explain these findings will be discussed.

Jan 1, 2014

By R. Cammack

"A fundamental component of the Hoek–Brown empirical rock failure criterion is assessing an appropriate mi constant. In developing their empirical criterion Hoek and Brown normalised triaxial test results by dividing the principal stresses at failure by the uniaxial compressive strength to provide mi values for typical rock types. Experience shows that Hoek triaxial tests for individual lithology types commonly have a large inherent scatter. In addition, tests are often conducted on core from random locations, which although being of one parent rock type, display variations in density as well as minor variations in grain size and alteration.This paper presents experience from projects the authors have been involved in which large sample populations of triaxial and UCS tests on similar rock types were available. Geophysical logging data was also available for some projects. The methods used to estimate the compressive strength for each sample and the effects on normalising the data sets are described. The variability of the data and uncertainties and assumptions involved in the process of assigning a mi value from the normalised data are also discussed."

Jan 1, 2015

By A. Sobering, G. N. Carlson

"This paper describes the conversion of the grinding section of the W a bush Mines pelletizing plant from conventional wet, open-circuit trunnion overflow ball milling, with filtering, and bentonite mixing on a common conveyor belt, to dry, open-circuit, grate discharge grinding, with pug mill mixing of bentonite and water at individual mills.The test work and data on operating economies to justify the cost of conversion are given. It is too early, at the time of writing, to have complete operating confirmation, but data are available. A brief description of the original plant is included."

Jan 1, 1971

By M. Lindgren, M. Latva-Kokko

Process performance can be significantly influenced by proper design of hydrometallurgical reactors. Optimal reactor configuration is case specific and depends on process requirements such as reaction rate limiting factor and particle size distribution. Choice of materials and manufacturing methods also play important roles in highly corrosive and abrasive environment often involved in hydrometallurgical industry. In this paper performance of different reactor designs has been compared in some typical hydrometallurgical applications. Results show that significant improvement in energy consumption, gas utilization efficiency and equipment lifetime can be achieved with process specific reactor design.

Jan 1, 2014

By A. Rao, J. A. Davidson, B. L. Jones, K. W. Bowes, D. Craib

Supported by ANSTO, Groundwater Science and Inception Consulting Engineers, Boss has embarked on a series of technical projects aimed at reinforcing the Project’s capability to meet its export permit production capability. This paper will focus on three aspects of this technical program: Reducing the cost of resource expansion through smart use of low cost, surface target generation techniques; Improving the rate of uranium leaching and solution stability (gypsum, jarosite) through lixiviant chemistry modifications; and Development of an ion exchange (IX) process to increase production capacity, and integration of IX and the current solvent extraction circuit with the existing uranium precipitation and product preparation circuits.

Jan 1, 2020

By Z. S. Shao, X. Z. Li

"Sub-critical crack growth plays an important role in long-term creep failure in brittle rock. Based on micromechanics established by using relationship between micromechanical wing crack growth model and macroscopic strain, and comparing theoretical model with testing results, a method, which applies the theory to real rock, is suggested in this paper. Using this method, properties of creep, damage and progressive failure in brittle rock are investigated. Effects of stress state on creep failure time and steady-state creep rate are analyzed and graphically presented. The results are helpful to support structure design and service life evaluation of underground structures with high geostatic stresses. INTRODUCTIONDuring the long-term operation in underground space with brittle surrounding rock, due to chemical action between pore water and rock, the failure of rock often occurs at stresses below its short-term failure strength, which brings serious effect on the long-term stability of underground structure. Thus, the long-term strength of brittle rock attracted wide interests of scholars around the world. The static fatigue limit was predicted by exponential function that is derived from abundant experiment data of stress level and failure time(Schmidtke & Lajtai, 1985), and similar result by relationship between stress state and failure time was also suggested (Lau & Chandler, 2004; Aubertin et al., 2000; Sangha & Dhir, 1972). According to relationship between steady creep rate and stress state during creep, a critical stress that transforms steady-state creep to accelerated creep was studied and the long-term strength was suggested (Tsai et al., 2008; Ma & Daemen, 2006; Lajtai et al., 1991). Based on the results of experiment in compression, the long-term strength of rock was defined by stress at volume strain reversal. When applied stresses are larger than the long-term strength, the microcracks in the rock will grow constantly, damage of rock will increase and failure of rock will occur finally (Chandler, 2013; Bieniawski, 1967; Brace et al., 1966)."

Jan 1, 2015

By A. H. Lang

THE recent production of important quantities of high-grade muscovite at the Purdy mine, near Eau Claire, Ontario, bas brought that district into prominence and bas added another strategic mineral to the list of Canadian products. The discoveries are thirteen miles west of Mattawa and about two miles north of the Trans-Canada highway and the Canadian Pacific railway. HISTORY Clear mica of low power factor is in considerable demand in Canada and in the United States for war purposes such as radio and telephone condensers, aircraft spark-plugs, radio tubes, and transformers. Some muscovite (white mica) bas been produced in North Carolina and New Hampshire, but the United States trade bas depended largely on importations of muscovite from India and of phlogopite (amber mica) from Madagascar. For many years Canada bas been a substantial producer of phlogopite, but was unable to compete extensively in the United States with importations from abroad. Canadian production of muscovite bas been negligible as no important deposits were known. Ever since the construction of the Canadian Pacific railway, attempts have been made from time to time to mine the pegmatite dykes in and near the Eau Claire area, but, although some feldspar has been mined, no appreciable muscovite was produced. Lace in 1941, J. Purdy and H. MacDonald discovered a dyke containing large crystals of high-grade muscovite from which they are reported to have sold $700 worth of mica. They recorded claims 35974 and 35975 in December, 1941, and claim 36095 in May, 1942.

Jan 1, 1943

By Omkar N. S. Beruar

Extraction of sill pillars has always been problematic because of high risk of seismicity and rockburst. Depending on a number of factors, a sill pillar can undergo different failure modes and cause problems in the mine. Of these, sudden and uncontrolled failure of part(s) of the pillar leading to highenergy seismic events and rockbursts is a main concern because it is not possible to predict the location and time of a rockburst apart from its potential to cause extensive damage to the mine structures. To date, a comprehensive technique for sill pillar design and recovery does not exist. Conventional methods of pillar design, such as the pillar stability graph method, are utilized to design stiff sill pillars. In these design approaches, the post-peak response of the pillar-rock system is not considered. This is in part due to a lack of clear and comprehensive understanding of the post-peak behaviour and failure mechanism of sill pillars. In general, the strength of a rockmass is described using a failure criterion. When stresses reach the strength of the rockmass, the rockmass does not necessarily become unstable and knowledge of the loads alone is not enough to assess the instability conditions accurately. In fact, it is not possible to predict instability of rockmass based on the strength/stress ratio alone because instability depends not only on this ratio but also on the loading condition and loading system characteristics. The loading system can dictate whether the sill pillar will go through a stable or unstable failure process. This paper examines the influence of various parameters such as the pillar width to height ratio, the extraction rate, and placement of backfill on the Loading System Stiffness (LSS) and the Pillar Stiffness (PSS). The ultimate goal is to design yielding sill pillars that would yield in a stable manner and will reduce the risk of pillar rockburst. Plane strain finite element analysis is conducted using the generalized Hoek-Brown failure criterion with elastic-brittle-plastic parameters. Examples are given to demonstrate how to calculate these stiffness values and assess the stability condition of sill pillars. It is found that increasing the rate of extraction increases the likelihood of unstable yielding of the pillar as has been found in other studies. Placement of backfill in a timely fashion in the stopes above and below the sill pillars increases the stiffness of the loading system. This indicates that backfilling of stopes while creating the sill pillar increases the likelihood of stable yielding of the sill pillar.

Aug 1, 2013

By Marcelle A. Hauseux

"The Turgeon Lake granite lies 5 miles north of Baie Johan Beetz, Quebec, at the eastern margin of the Grenville Province. The rocks are classed as granites, granulites, quartzites, biotite schists and gneisses, and amphibolites. The granite's uraniferous character is manifested by phosphuranylite, uraninite, and metamict .zircons associated with magnetite. Field anomalies occur in irregular pods, conformable with the tectonic foliation, in bands roughly paralleling sedimentary bedding. Associated features diagnostic of uraniferous granite are smoky quartz, brick-red feldspar, magnetite and a coarse to pegmatitic grain size. The granite is chemically and physically heterogeneous. Metasediment-granite contacts are diffuse or sharp, and usually conformable to bedding. The regional foliations within all rock types are coherent, and sedimentary structures are often preserved within both metasediments and granite. Autometasomatism probably was a strong granitization agent.A uranium reconcentration into fold-axial zones from original sediments which have been highly granitized during at least two phases of folding is suggested from the available data."

Jan 1, 1977

By W. L. Ott, C. L. Lewis

"AbstractA technique is described for preparation of palladium sponge and for spectrochemical analysis of the metal in this form. The precision and accuracy of the method are discussed. Analyses are compared with previous spectrochemical analyses of palladium in the black form. Good agreement was found in the two sets •of results and it is concluded that they are more reliable than wet chemical .analyses of the same material.IntroductionFOR SEVERAL YEARS the problem of platinum metal analysis by spectrochemical methods has been under investigation at the Spedtrographic Laboratory, Department of Geological Sciences, Queen's University. The problem, briefly -stated, is as follows: Samples of platinum, palladium,-rhodium, ruthenium, and iridium are received as fine metal powders, called sponge. Direct spectrographic analysis of this material has not been found satisfactory due to its heterogeneity •as regards contaminant metals, which may be present up to a total of one per •cent or more. Further-more, spectrographic standards are difficult to obtain and difficult to prepare accurately by adding weighed portions of contaminant metals to the sponge. The fact that •contaminant metals in original samples are probably alloyed with the major constituent is a further difficulty since complete fusion of these refractory metals proved impractical in the present case as a means of standard preparation. It •has, therefore, been found most satisfactory to dissolve the metals, prepare standards by addition of solutions of contaminant metals, and to reduce both standards and samples to a homogeneous form. A previous paper, by Hawley, Wark, Lewis and Ott (2) dealt with a method for spectrochemical analysis of platinum and palladium in their black form. Since completion of research on the black technique, the possibility of analyzing palladium accurately in its sponge form has• been investigated."

Jan 1, 1953

By J. -C. Sztuke, M. Cao

ABSTRACT The correlations between froth recovery of coal and air recovery were investigated using a hybrid mechanical flotation column. The particle slurry was fed onto the surface of air-water two phase froths to carry out the tests. Froth recovery was taken as the recovery of particles into the froth product, whereas air recovery was determined by the froth height method. The relationships between froth recovery and air recovery were nearly linear, with greater slopes for more hydrophobic particles. Inside the froth phase, the particles were stratified, with hydrophobic particles concentrated in the upper region and hydrophilic particles in the lower region.

Jan 1, 2013

By L. Dorador

"In block caving projects, the rock mass fragmentation process plays a controlling role in the design and success of the operation. Poorly understood, however, is the secondary fragmentation that occurs as blocks of caved ore move through the draw column and interact with one another. The initial size of these blocks can be considerable, as can their strength and stiffness as the presence of non-persistent joints and veining will be variable. Intuitively, more planes of weakness within the blocks should facilitate early fragmentation, but this assumption could depend on additional factors such as contact type between adjacent blocks and loads imposed through varying heights of the draw column. This paper reports the findings from a laboratory investigation examining the role of block strength and planes of weakness on secondary fragmentation. Testing was carried out on small-scale concrete cubes of uniform size, with and without embedded planes of weakness. The results obtained demonstrate the significance of veining and other planes of weakness on secondary fragmentation under one-dimensional compression, and allow for the development and constraint of empirical guidelines.INTRODUCTIONThe fragmentation process during block caving involves the initial (primary) fragmentation of rock in the cave back through stress-induced fracturing, release and fall of individual blocks onto the broken ore muck pile. This is followed by secondary fragmentation involving splitting and rounding of blocks as they move downwards through the draw column towards the draw point. The degree of secondary fragmentation achieved involves many variables related to the mechanical properties of the rock blocks as well as different operational factors. With respect to the block properties, the presence of planes of weakness in the form of veining and non-persistent joints is a topic of special interest given the significant influence it potentially has on the overall fragmentation process. However, the inherent heterogeneity and variable size of individual blocks generated from the cave back makes it difficult to develop any empirical relationships relating secondary fragmentation to compressive loading based on insitu observations and mine data. More preferable would be to keep constant block parameters, such as shape (aspect ratio and angularity) and size, through controlled laboratory testing. This work presents an efficient technique to fabricate concrete cubes in order to keep constant different block properties. These are then tested under one-dimensional compressive loading. The objective of these tests is to emulate a tight packing condition of single blocks such as that which would occur when the air gap between the cave back and broken ore in the draw column is small. When the air gap is small, detached blocks are unable to fall and rotate but instead maintain a very tidy arrangement with minimal voids left between adjacent blocks."

Jan 1, 2015