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By P. Su

Friction stir spot welding of a range of Mg-alloys is investigated (AZ91, AZ31, AM50 and AM60). The peak temperatures during friction stir spot welding of all Mg-alloys are close to their solidus temperatures. Also, the apparent material viscosity of Mg-alloy sheet is lower than that when Al-alloy sheet material is spot welded. This is important since it means that the widths of the stir zones forming during spot welding of Mg-alloy sheet are smaller than those when Al-alloy sheet is welded (when identical welding parameter settings are applied). These lower apparent viscosity values must be taken into account during numerical modeling of the Mg-alloy spot welding process. The efficiency of energy utilization is very low when Mg-alloy sheet is spot welded and is of the same order as that when fabricating Al-alloy sheet. The energy generation contributions of the rotating pin and the tool shoulder are investigated. When the spot welding operation is carried out without the application of a dwell period, the contribution made by the rotating pin vis-à-vis energy generation is around 66%. The contribution made by the tool shoulder increases to about 65% when a dwell period of four seconds is incorporated during the spot welding operation. This increase results from a longer contact time between the tool shoulder and material within the stir zone, The failure load during overlap shear testing increases when the bonded area and the energy input increase during spot welding. Sample failure initiates from unbonded regions and from discontinuities at the edge of the stir zone. The formation tendency of discontinuities is increased when Mg-Alloy sheet is spot welded because of the limited deformation characteristics of the base material at lower temperatures.

Jan 1, 2006

By J. Q. Chen

The elastic-plastic behavior and the fracture mechanisms of two 2198 Al-Cu-Li thin sheets are investigated. The first material (2 mm thick) is in a recrystallized state after cold rolling. The second material (6 mm thick) is hot rolled and has a fibrous grain structure. The two materials are studied in both T351 and T851 conditions. Tensile tests are carried out along different sheet directions using flat and notched specimens. Fracture resistance was characterized using Kahn tear specimens and M(T) panels. Macroscopic fracture surface of smooth tensile specimens depends not only on testing material but also on the loading direction. For Kahn tear specimens, fracture is initiated in a small flat triangle whereas slant fracture is observed during crack propagation. Fracture mechanisms were investigated using scanning electron microscopy (SEM) and X-ray 3D tomography.

Jan 1, 2011

By A. Coulombe

"RésuméL’analyse des séquences d’exploitation, actuellement en usage pour les gisements très inclinés, a démontré qu’elles ne sont pas toujours optimales du point de vue du contrôle des terrains et de la concentration des travaux d’abattage (nombre de chantiers simultanément en opération). Effectivement plusieurs séquences sont très propices à la création des nombreuses zones de hautes contraintes, qui sont à l’origine des effets de pilier. L’étude de cas de la mine Lac Shortt a démontré que certaines séquences d’exploitation, actuellement en usage, ne sont surtout pas adéquates dans le cas d’un état élevé des contraintes naturelles. En effet la mine a eu de sérieuses problèmes avec le contrôle des terrains (coups de terrains et les effondrements des épontes). Ces effondrements étaient responsables de la dilution excessive et des pertes importantes des réserves minières. Les deux nouvelles séquences proposées, visent la meilleure redistribution des contraintes d’exploitation en vue d’éliminer la création des effets de pilier. En plus elles permettent une concentration plus élevée des travaux d’abattage.À notre avis les séquences proposées pourraient améliorer substantiellement la stabilité des chantiers d’abattage et par la suite les performances technique et économique des opérations souterraines. ABSTRACTThe planning of underground mining sequences represents an important aspect of the mining operation. The analysis of mining sequences actually in use for very steep orebodies has demonstrated that they are not always optimal, considering ground control and the number of stopes simultaneously in extraction. These sequences are conducive to the creation in the rockmass of several stressed zones caused by pillar effects. The case study of Lac Shortt mine showed that the sequences of exploitation currently in use are not adequate especially in the case of a high state of the natural constraints. Indeed, the mine had serious problems with ground control (rock bursts and collapse of walls). These collapses were responsible for excessive dilution and significant losses of mining reserves. The two new sequences suggested aim for the best redistribution of exploitation constraints in order to eliminate creation of pillar effects. Moreover, they allow a higher number of stopes to be extracted simultaneously. In the opinion of the authors, the sequences suggested could substantially improve the stability of working areas and, thereafter, technical and economical performances of the underground operations."

Jan 1, 1998

By Jerry Handford

Investing in the Development of our Future Workforce ?Collaborative partnerships with educational institutions, industry associations, governments and other businesses. ?Programs: »Co-op / Discipline Student Program »Trades Development Initiatives »Operator Training Programs »General Student Program »Careers Next Generation / Community Careers Co-operative

May 1, 2006

By B. Holaday, H. McLaughlin

Orano Canada Inc. (Orano) operates the McClean Lake mill, located in the Athabasca Basin region of northern Saskatchewan. It processes high concentration uranium ore, delivered in slurry form from the Cameco Corporation operated Cigar Lake mine. After the ore slurry is leached at the McClean Lake mill, the leach residue solids are washed in a process known as counter-current decantation (CCD). This process uses six thickeners to facilitate counter-current washing of solids with diluted acid, flocculation and settling, as well as pumping the washed leach residue to the tailings neutralization circuit (TN), and the uranium laden aqueous to the solvent extraction circuit (SX). Challenges in settling the slurry in CCD started in early 2017. This is largely due to the variation in fines content of the slurry (D80≤75μm), and clay content. There are several changes that have allowed the mill to adapt to the evolving challenges of settling leached Cigar Lake leach residue. Flocculant selection and mixing, temperature effects, bed level management philosophy, and centre-well feed density are key parameters that have been explored as part of adapting to changes in Cigar Lake ore quality.

Jan 1, 2020

By G. Marchand, R. H. Hay, E. C. Pearson

"AbstractA polishing .technique is described together with two anodic etching methods for aluminum and its alloys. Some of the optical and structural characteristics of the film formed by •these etching methods are discussed and it is shown to what degree these properties of the film are related to the crystallographic orientation of the metallic substrate. Applications to the study of recrystallization and twinning phenomena and to the study of plastic deformation, banding, and texture estimation are discussed. Micrographs are shown .to illustrate the manner in which the technique is particularly well suited to the study of such phenomena.IntroductionThe physical metallurgist is constantly faced with the problem of polishing and etching of metallic sections. Mechanical polishing is tedious, time consuming, and not applicable whenever a surface entirely free from plastic deformation is required. Etchants are generally required to reveal the grain structure in order to determine its size, shape, and regularity, or to bring up constituents. In the case of aluminum, the .most common etchant to reveal grains is a mixture of three acids: HC1, HN03, and HF. This etchant is fairly satisfactory on certain alloys and for certain metallurgical conditions but in general fails to give a good definition of the grain on castings, on highly alloyed products, and whenever the grain is smaller than 100 microns in diameter. Besides size and shape, a grain, or crystal, has an orientation and may be endowed with several types of imperfections."

Jan 1, 1952

By W. Swidzinski

"Zelazny Most" post-flotation copper mine tailings pond is the only place to of storeing wastes for KGHM POLSKA MI EDZ S.A. The flotation tailings is are the main waste stream in copper mining in Poland. Sufficient storage capacity for tailings is crucial for , thus uninterrupted production of copper is crucially related to the possibility of storing wastes in the pond. The pond covers a Its over 14 km2 arca, almost 50 m high dams making this dame this construction one of the largest in the world. The risk assessment of potential damage due to un stable ility loss of dams or environmental contamination, as well as safely constructing damsincrease of dams within the design criteriaprocess, require quick access to a large amount of the monitoring data , which in vast amount have to be monitored, that needs to be analyzed and processed and reported, every day. This In the paper describes the numerical information system "SyZeM" , used for designated to the "Zelazny Most" pond, baseding on the Oracle database and Geographical Information System , to manage the graphical and descriptive data in coherent way., is presented. The main structure of the system, as well as the methodology of storing, processing and reporting the geological, geotechnical, hydrogeological, geophysical, chemical and survey data are shown. The aspects of Optimizing optimal and risk mitigation and safe management of copper wastes and risk mitigation with the help of "SyZeM" are discussed.

Jan 1, 2007

By D. F. Malan

"This document highlights some of the topical problems associated with the design and support of deep tabular excavations in hard rock. The displacement discontinuity boundary element method has been used for at least five decades to analyse stress and displacement distributions around narrow width excavations with complex plan outlines. The assumption is made in most cases that the rock mass surrounding the excavation is perfectly elastic. Although this approach works well to minimise stress concentrations in practice, it has limitations as important parameters, such as the effect of mining rate, cannot be investigated. Recently, a limit equilibrium model has been studied as a means to enhance standard layout design exercises by including an interactive on-reef damage model. This approach can include explicit energy release dissipation computations. A second problem faced by engineers in the mining industry is the evaluation of pillar and remnant stress. The paper highlights two aspects namely the effect of element size in displacement discontinuity modeling on pillar stress and the difficulty to estimate the effect of total closure on the regeneration of stress in old mining areas. Regarding the support of the tabular excavations, current efforts are focussed on providing improved aerial coverage using hangingwall bolting and temporary nets. An unresolved issue is the installation of permanent mesh in low stoping width areas. INTRODUCTIONSince 1886, more than 50 000 tons of gold has been mined in the Witwatersrand Basin of South Africa (Hartnady, 2009). The nearby platinum mines also saw significant growth in recent years and more than 80% of the world’s platinum group metal reserves are contained in the Bushveld Complex of South Africa (Nell, 2004). Apart from the economic aspects, the mines served as an outstanding rock engineering “laboratory” for many decades owing to the deep, tabular nature of the excavations. The period from 1960 to 1980 was especially lucrative in terms of research and world-renowned researchers investigated the support and rockburst problems (e.g. see Cook et al., 1966; Salamon, 1968; Bienawski, 1973; Wagner, 1984). Many of the rock-related problems nevertheless persist up to the present day and this paper explores some of these problems and recent progress. The production of gold declined substantially in recent years (Hartnady, 2009) and well-directed rock engineering research can play a meaningful role to slow this trend. The objective of the document is to highlight critical areas requiring additional research and not to discuss the topics in detail. The reader is referred to the many references for additional information. The paper only focuses on three areas namely numerical modelling, pillar stress estimation and aerial support. Although these are diverse topics, it is included in one paper to illustrate the many unsolved and practical problems associated with deep tabular excavations."

Jan 1, 2015

By A. J. Giroux

"The use of Ishikawa cause and effect diagrams in an analysis of requirements for improving safety and productivity at Falconbridge's Strathcona Mill is presented. The analysis lead to numerous small improvements being made with the cumulative effect being a significant improvement in both areas.INTRODUCTIONMill management in the 90's involves the major requirements to improve both safety and productivity in the workplace. These objectives, once seen as unrelated or even mutually exclusive, are now accepted as being complementary. Managers, trained either on the job (coming up through the ranks) or in an engineering discipline followed by first and second line supervisory experience are now turning to methods developed in consumer product manufacturing to ensure that all the components are in place to ensure the ore processing facilities are safe and efficient.This paper shows how management at Falconbridge' s Strathcona Mill used the Ishikawa ""fishbone"" diagram ( 1) , a method further developed by Deming(2), to put into place a comprehensive safety and productivity process. The Ishikawa/Deming concept is that no one element or program will itself continually improve a process or service. It is only by examining and then improving all the elements that are involved in the process or service that continuous improvement is obtained. The process was built on the Deming principle of worker ownership where management is the facilitator for putting into place the mechanisms whereby workers can themselves improve the operation. The process is illustrated mainly by examples of the changes made in the hope that these may be of direct help to other operations."

Jan 1, 1993

By W. A. Gow, V. F. Harrison, H. H. Mccreedy

A semi-continuous bench-scale, countercurrent-decantation system, in which the ore was moved countercurrently to the flow of leaching solution, was used to conduct acid-leaching tests on uranium ore with the aid of bacteria. This method, which involved a low degree of agitation, was successfully applied to extract uranium in practical amounts and at practical rates. The acidity of the leaching solution was the main variable investigated in the bench-scale tests done at the Mines Branch, Ottawa. Over 90 11er cent of the uranium was extracted in a six-stage system. The results suggest that this technique could be ap-plied in the utilization of bacterial oxidation and leaching as a method for treating Elliot Lake uranium ore.

Jan 1, 1969

By A. Y. Senchenko, Y. V. Kulikov

"In recent decades HPGR technology has proven itself in comminution circuits of mining plants. High technical and economic performance, lower specific energy consumption and reliability of HPGR equipment makes it an efficient alternative to conventional circuits using stage crushing and rod/ball milling, as well as to AG/SAG circuits. However, despite all the advantages of this technology the correct selection of key and auxiliary equipment is very important since errors at testing and design stages may lead to discrediting of the whole concept of HPGR application. There is a great variety of possible circuit configurations using HPGR, e.g. with circulation of edge product, with crushing of the whole discharge and circulation of screen oversize, successive two-stage crushing, etc. Each type of minerals will require its own optimal crushing circuit. In this context the testing methodology for selection of an optimal configuration becomes of prime importance. It is common knowledge that the best simulation of material crushing and softening within a HPGR can be obtained only in the course of a large-scale pilot test. The main approaches applied to this kind of testworks are described in this article. Special aspects of HPGR technology design and industrial operation are revealed as well. Some operational issues of HPGR equipment and of circuit as a whole were detected. They are related to regions specifics, plants location, and other factors. Process solutions proposed to deal with these issues are also indicated in the article. INTRODUCTIONDesign and construction of the processing plants involving High Pressure Grinding Rolls (HPGR) technology becomes more and more common in mining as this technology has specific technical and economic advantages against the circuits with autogenous/semiautogenous mills (AG/SAG) and other circuits. The main advantage of the technology is low energy consumption and low operation costs respectively. The presence of microcracks and increased content of fine size fractions in the crushed product contribute to reduction of energy required for further ball grinding. Besides, HPGR technology applies a special wear resistant liner that enables significant reduction of operation costs of grinding media and liner comparing with AG/SAG circuits."

Jan 1, 2016

By E. Heikkinen, J. Suikkanen, T. Siren, J. Valli, M. Hakala

Diametrically faced borehole breakout observations are a fairly good indication of magnitude of the secondary stresses acting perpendicular to the borehole. In cases of low in situ stresses, where borehole breakouts are not observed naturally, it is possible to increase the prevailing stress state around the borehole by increasing the rock temperature. When the temperature is increased sufficiently, thermally induced borehole breakouts will occur. By implementing the temperature increase in boreholes located at excavated tunnels, it is also possible to study the effect of the near-field stresses caused by the excavation. The near-field stress state changes as a function of borehole depth, thus increasing the information available from experiment. To study the feasibility of this proposed low cost method, a Borehole Thermal Spalling (BTS) experiment was executed in ONKALO Underground Rock Characterization Facility, in Western Finland in 2014. The first borehole pilot test with the method was conducted in ONKALO at the POSE niche in already at May 2010, with the second pilot test following in August 2010 at Äspö HRL. The major objective of the experiments was to define the trend of the maximum in situ stress component, while also providing knowledge of the in situ spalling strength of the ONKALO rock mass. The stress state in ONKALO is nearly isotropic in horizontal layer, causing problems for the use of more traditional stress measurement methods. With boreholes heated over long interval, the weakest rock parts are observed to fail, thus providing statistical confidence. For these reasons, continuous test sections have an advantage in ONKALO, compared to spatially limited stress measurement methods such as overcoring and hydraulic fracturing. The BTS experiment is conducted in 9 meter deep vertical boreholes located at the POSE niche, situated -345 m depth below the ground surface. The boreholes used within the BTS experiment are located in migmatitic granite, in an experiment area where the surrounding stress state and the rock strength are fairly well known. The prior knowledge of the stresses is favourable for the experiment, as it requires careful planning and iterations to determine the appropriate heating power domain. Too low heating power will not be sufficient to cause borehole breakout, while too high heating power causes breakout in all directions thus making determination of stress direction hard or impossible. The initial state of the borehole and induced borehole breakouts will be monitored using acoustic televiewer logging (ABI) and optical borehole logging (OBI) imaging techniques. Fracture mechanics modelling is used in planning of the experiment, also in back-analysis to link the observed breakout angle to stress state. Both the pilot test in 2010 and BTS test in 2014 resulted in similar borehole breakout direction. The results are in line with so called EDZ & VT1 stress interpretation, revealed the maximum horizontal component bearing the magnitude of 21.5 MPa, with the trend of 166°.

Jan 1, 2015

By M. S. Diederichs, G. Walton

"Developments in understanding the brittle fracture of rock over the past two decades ultimately led to the acceptance of a cohesion-weakening-friction-strengthening model as an appropriate strategy for the modelling of spalling using a continuum approach. This strength model has been used to replicate observed failure depths and geometries for a number of case studies in the literature, most notably the AECL Underground Research Laboratory in Manitoba. One thing which these case studies typically ignore, however, is the influence of rock dilatancy on the evolution of brittle failure. Physically, this phenomenon is the volumetric expansion of the rock due to fracture opening; numerically, this phenomenon is captured by the flow rule, which is often characterized by the dilation angle, ?. Accurately modelling rock dilatancy in conjunction with strength evolution is necessary both to predict the magnitude and distribution of ground displacements, as well as the exact depth and shape of the fracturing zone. Both of these factors can have significant implications for support design. This paper is focussed on presenting some of the recent developments in this field in the context of a number of numerical modelling case studies. Initially, a new model for the dilatancy of brittle rock is presented, as well as some representative data and model parameters for different rock types. Next, several case studies of highly stressed tunnels and shafts are presented. The results of continuum numerical models are presented to demonstrate the ability of the back analyses to match observed in-situ measurements and obtained. The predictive capabilities of the material model are also highlighted for cases where sufficient “a priori” information (such as laboratory compression testing data) are available. The issues of model nonuniqueness and strain-localization/bifurcation are also addressed."

Jan 1, 2015

By I. Demers

The abandoned Manitou mine site covers an area of approximately 190 ha near Val d?Or, Quebec. This old site has been generating acid mine drainage for several decades. In 2006, a partnership was established between the Quebec Ministry of Ressources Naturelles (MRN) and Agnico-Eagle Mines to reclaim the Manitou site using tailings from the nearby Goldex mine. These neutral tailings were to be deposited on top of the Manitou site. An extensive study was performed to evaluate specific reclamation scenarios to control acid mine drainage using Goldex tailings as cover material. The article first describes the global approach used for this evaluation, which includes in-situ hydrogeological monitoring, tailings characterization, laboratory column tests, and numerical modelling. Of the thirteen column tests, three were conducted to evaluate the parameters affecting the performance of covers made of Goldex tailings placed over the spillage area of the Manitou site. Geochemical and hydrogeological parameters were assessed during the leaching column tests for almost two years. The tests aimed at evaluating the effect of water table level and monolayer cover thickness on the overall performance. The testing procedure involved monthly leaching and measurement of geochemical parameters. Results indicate that water table position is the most important factor affecting the monolayer cover performance to control AMD. Based on these results, it was established that the water table must be located near the interface between the Goldex and Manitou tailings to effectively reduce AMD generation. Cover thickness also has an impact on cover performance, which is however less significant than the water table position. The testing scenario with a water table located at the interface with a one-meter Goldex tailings cover showed progressive improvement in effluent quality.

Aug 1, 2013

By Michael Samis

Conventional project valuation techniques, such as discounted cash flow (DCF) method, are more frequently being criticised for the manner in which they consider the interacting effects of uncertainty and project structure (including management flexibility) on project value. Modern asset pricing (MAP; often called ?real options valuation? when applied to the analysis of flexibility) is a more general valuation framework that corrects many of the shortcomings of common valuation methods. Previous mining applications of MAP have tended to treat the ore deposit as a homogenous entity. While useful for demonstration purposes, this is inadequate for practical application in industry. This paper presents a MAP valuation example that allows for the heterogeneous nature of an ore deposit. It shows that deposit structure may increase the complexity of the mine planner?s decision so that results of a standard DCF analysis, or a simple MAP analysis that ignores the details of deposit structure, are misleading. In the example, a management is considering the development of an adjacent low-grade zone while mining operations in a high-grade zone are ongoing. If the low-grade zone is developed before high-grade reserves are exhausted, the proposed development will include both low-grade zone development and a capacity expansion to handle additional low-grade reserve production. If development of these reserves is delayed until the high-grade reserves are depleted, then the low-grade reserves can be developed without a capacity expansion. A typical DCF analysis would reduce the management?s decision problem to three alternatives: 1) continue mining only in the highgrade reserves, 2) immediately develop the low-grade reserves and expand capacity, and 3) delay low-grade zone development until the high-grade reserves are exhausted. The model presented here allows the management to reconsider the development and capacity expansion decision on a discrete half-year basis. It delineates price regions, for given levels of high-grade zone reserves, in which it is optimal to develop the low-grade zone, defer low-grade zone development and abandon the mine irrevocably. The model presented here extends the ability of mine planners to describe actual project structure while using the MAP valuation framework that is already noted for its capacity to combine project uncertainty and risk insights with a dynamic project description.

May 1, 2001

By Junhyun Choi, Allan Gomez-Flores, Chonbuk National University, Siyoung Q. Choi, Gahee Kim, Seungkon Kim

In this study, to confirm the effect of depletion attraction on the flotation, we theoretically and experimentally investigate the effect of the depletion attraction force on flotation. While varying the concentration of the depletion agent (polyethylene glycol), three different systems are studied: pure malachite, pure silica, and a 1:1 mass ratio of malachite and silica binary system. We find that recovery increases significantly as the concentration of the depletion agents increases for all three systems, as the depletion agent facilitates the adsorption of the particle on the bubble surface. However, the recovery suddenly decreases in a certain concentration range, which corresponds to the onset of the decreased surface tension when high concentrations of the depletion agent are used. This non-monotonic overall recovery trend implies the surface adsorption of the depletant on a surface. The decreased surface tension of the air/water interface suggests that the recovery rate is lowered due to the adsorption of the depletion agent to the bubble surface, acting as a polymer brush. Based on our observations, we conclude that the depletion force can greatly improve particle adsorption, as predicted in the accompanying theory paper, while simultaneously the adsorption of the depletion agent on the bubble surface plays an important role because it hinders particle adsorption. We also perform experiments in the presence of a small amount of a collector, sodium oleate. An extremely small amount of the collector leads to the increase in the overall recovery, which eventually reaches nearly 100 percent. Nevertheless, the grade worsens as the depletant provides the force to silica particles as well as target malachite particles.

Jan 1, 2016

By Carrasco .. P. J. A., R. Parada, I. Saavedra, F. Parada, R. Parra, E. Balladares

In most of the smelters, the management of flue dust has a double objective: the control of minor elements in the anodes and the management of volatiles compounds that can cause contamination due to fugitive gas emissions. This is a special concern when high content of Va elements (As, Sb & Bi) are present in concentrates. We present the results of the experimental study to prove the principle of a novel process that recovers, via volatilization, the As, Sb and Bi in the flue dust as gaseous sulfides, due to a previous sulfidization. In the case of as control any further classical treatment for its stabilization is possible from the gas. The clean calcine can be returned to the smelter avoiding any concentration of these minor elements in the circuit. This process is now tested at pilot scale and shows better indices on carbon footprint than the classical hydrometallurgical process for flue dust.

Jan 1, 2011

By C. P. Jenney

"Exploration for copper, in a region of 7,000 square miles on the Arctic coast between longitudes 114 and 118 degrees west, has covered a period of nearly 200 years. Occurrences of native copper, used by the natives for tools and weapons, have been reported since the early part of the eighteenth century. In J 771 Samuel Hearne of the Hudson's Bay Company, in the course of his classic 3-year journey from Fort Churchill, became the first white man to see the deposits, and incidentally the first to reach the Canadian Arctic coast by land. During the next 140 years the deposits were mentioned by every explorer and traveller who passed through the area. A good historical summary of this literature has been presented by Tyrrell (1912).In 1911-12 the Douglas-Sandberg party did the first geological mapping along the Coppermine River and Dismal Lakes (Douglas, J., 1913; Douglas, G. M., 1914), and described the copper occurrences there. In 1914 J. J. O'Neill (1924) of the Canadian Arctic Expedition investigated the showings on Bathurst Inlet. In 1929-31 two Canadian exploration companies sent prospectors and geologists to the area (Gilbert, 1931; Norrie, 1931; Duncan, 1931). Since that time only brief references have been published (Kidd, 1931; Stockwell and Kidd, 1931; Lord, 1941, 1951; Washburn, 1947). In 1943-45 an area of more than 1,500 square miles was prospected by American Metal Co. of Canada, Ltd., under the direction of the writer. Forty-nine showings were examined; seven of these were mapped in detail by plane-table and two were sampled by 27 short diamond drill holes totalling 3,061 feet. All holes were in permanently frozen rock, and the deepest vertical distance reached was 206 feet. Five groups of claims were staked. These later lapsed, but one of the groups was restaked in 1951, and assessment drilling and some trenching were carried out in 1952-53. Results were disappointing, and the claims have been allowed to lapse.The area is within the Arctic Circle, northeast of Great Bear Lake and 360 miles north of Yellowknife on Great Slave Lake. For exploration purposes, access is by aircraft from Yellowknife. During the short open season heavy freight can be brought by sea to Coppermine at the mouth of the river, either from Aklavik at the mouth of the Mackenzie or around Alaska. Concentrates would have to be moved by these routes.Although none of the deposits so far found is mineable under present conditions, the total volume of copper in the numerous showings marks the district as a major area of copper mineralization, which may some day be of economic importance."

Jan 1, 1949

The system of keeping geological plans and sections for the Geco Mine at Manitouwadge, Ontario, is described. Special methods employed to save draughting time with-out sacrificing accuracy, such as the extensive use of black line prints, are discussed. The uses made of the plans and sections by the mine planning engineers in their designs of stopes, and by the blast-hole engineer in ~is preparation of blast-hole layouts, are noted. An unusual scheme for portraying the distribution of .copper, zinc and silver values within the ore zone is de-scribed. The method of estimating the grade of ore to be "blasted in each ring of blast holes is outlined, as is the method of estimating the annual ore reserves. The design of an effective but simple transparent geo-logical and mine development model, used as a display for -visitors, is discussed. A large-scale model used for the study of problems in geological structure is also de-scribed.

Jan 1, 1964

By Matej Petružálek, Tomáš Svitek, Tomáš Lokajícek

"Migmatite from the Skalka region (Czech Republic) was chosen as the experimental rock material. It has macroscopically visible plane parallel structure (foliation). The foliation was caused mainly by biotite grains arrangement. The cylindrical samples of migmatite with subhorizontal, subvertical and oblique foliation were uniaxially loaded up to the failure. Network of 8 broad band sensors was employed for acoustic emission monitoring and ultrasonic sounding. A grid search method with anisotropic velocity model was used for AE hypocenters localization. The source types of successfully localized events were determined from the average first arrival amplitude. Structural anisotropy of tested rock material caused the anisotropy of its mechanical properties (peak strength, Young’s modulus) as well as a different way of fracturing process in dependence on the angle between axial stress and foliation plane. The combination of splitting, shearing and sliding was found to control the fracturing of sample with subhorizontal foliation. The shearing and sliding was dominant in fracturing of samples with oblique foliation. With greater dip of foliation, the role of sliding increased at the expense of shearing. Due to the favorably oriented system of microcracks already present, the shearing and splitting was at the same level during fracturing of the sample with subvertical foliation before nucleation began.INTRODUCTIONThe process of failure of low porosity rocks depends on their mechanical properties and actual stress and temperature condition. At the low pressure and low temperature, the most common way is brittle failure, which is a progressive process requiring the initiation, growth and coalescence of cracks (Lockner, 1993). Stress strain behavior of low porosity crystalline rocks, during the laboratory compression experiments, is divided into four characteristic stages: crack closure, elastic region, stable crack growth and unstable crack growth which leads to the brittle failure, Brace et al. (1966) , Bieniawski (1967), Lajtai (1974), Cai et al. (2004), Nicksiar and Martin, 2012 and 2013.The fracturing process of stressed rock begins with the crack initiation (sci), which for low porosity rocks occurs approximately at 40-50% of peak strength (sp) (Cai et al., 2004; Nicksiar and Martin, 2013). After the sci, the dilatancy begins and stable crack growth follows up to the crack damage threshold (scd), which is approximately at 80% of sp (Cai et al., 2004). After crossing the crack damage level, there is an unstable crack growth accompanied with nucleation of fault plane (sn) at 97-100% of sp. (Rao et al., 2011). The stress drop accompanied with formation of macro scale shear failure plane follows after peak stress is crossed."

Jan 1, 2015