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By R. W. Lawrence, A. Bruynesteyn

"Pre-oxidation of refractory pyritic concentrates by biological leaching to enhance the recovery of gold and silver in cyan ideation has been investigated. The results of laboratory tests on three concentrates are presented. In all cases substantial increases in precious metal recoveries were obtained following the pre-treatment. For one concentrate, gold recovery of 81% was achieved following an 87% oxidation of pyrite, compared with 24% recovery by direct cyanidation of non-oxidized concentrate. Gold and silver recoveries from the other concentrates were increased from the range 60-78% to over 90% and from 80-86% to over 98% respectively. Operating parameters are discussed and methods of maintaining high oxidation rates are evaluated. Methods of employing this pre-oxidation technique in commercial practice are described.IntroductionMany of the gold and silver deposits now being developed contain precious metals finely disseminated in sulphide minerals such as pyrite. These ore s often present considerable resistance to metal recovery. The ease with which gold may be extracted is usually related to grain size and its manner of distribution within the host mineral. In many cases, a significant percentage of the gold may occur in submicroscopic form, or in solid solution with pyrite, so that even very fine grinding fail s to liberate the metal for recovery by cyanide leaching. Such ores are often termed refractory. Even in cases where liberation by fine grinding is practicable, high cyanide and lime consumption may be experienced due to the presence of specific sulphide minerals, and poor metal recovery may result.Pre-oxidation methods for refractory ore s and concentrates are commonly used to improve precious metal recoveries. Roasting, for example, as a pre-treatment to cyanidation, removes harmful constituents by oxidation or volatilization, and liberates gold from pyrite. In some cases, however, this method of pre-oxidation can result in poorer metal recovery, particularly of silver, due to fusion and the formation of clinker, and the formation of compounds which consume cyanide in the subsequent metal recovery stage. Difficulties in compliance with environmental pollution regulations may also be encountered."

Jan 1, 1983

The rate of liquid copper deoxidation during top blowing of reducing flames has been investigated using a high capacity thermogravimetric unit at 1200 °C. For 1 kg copper samples, it was observed that the rate of deoxidation was proportional to the flow rate of the reducing reagent (H2 or CO). Under similar experimental conditions, it was found that H2 is more effective than CO even though both have similar thermodynamic potential to deoxidize liquid copper. The rate of deoxidation of liquid copper with reducing 0 2/CH4 flames was measured for 0 2/CH4 molar ratios of 1.5 to 2. The deoxidation rate depends on the 0 2/CH4 ratio and decreases as it approaches the stoichiometric ratio (02/CH4 = 2). Estimation of the rate of deoxidation of liquid copper with top blowing flames based on the thermodynamic composition ofH2 and CO in the product gases, agrees well with measured values.

Jan 1, 2007

By Georges Croisé, Les-Lee Thompson, Adrien Debergé

Membrane filtration systems have regained focus in recent years as an effective means of liquid-liquid separation to increase the concentration of valuable elements, recover reagents or remove impurities. ORANO Mining (formerly AREVA) investigated this cost optimization process opportunity as early as 2011 for implementation at the Trekkopje project (Namibia). The key focus was to separate and recycle bicarbonate from the uranium bearing eluate solution. The performance targets were successfully achieved at lab- and pilot scale with an ultrafiltration and nano-filtration configuration system. Early 2015, ORANO Mining further launched an investigation into the use of membranes for acid recycling at the KATCO In Situ recovery mine in Kazakhstan based on the favorable results from the original bicarbonate application. KATCO is the world leader in ISR uranium mining with an eluate processing capacity of 80 000 m3/yr. This site consists of two processing plants namely, Muyumkum and Tortkuduk, located 40 kilometers apart, both operating under acidic conditions whereas precipitation and packaging are based in Tortkuduk only. This paper serves to present the results from the integration of a nano-filtration system at the Muyumkum satellite processing plant. The project consisted of screening laboratory bench studies conducted at ORANO-CIME followed by process validation at KATCO through further bench and pilot test work. The feasibility study assessments were successfully concluded which led to the implementation at an industrial scale in Muyumkum of a nano-filtration process to reduce eluate volumes being sent to the uranium precipitation section whilst achieving effective separation of uranium from sulfuric acid. Nano-filtration technology has drawn significant attention due to the efficiency and reproducibility of the process and its moderate capital cost relative to operational savings. The reliability of the previous results is a great opportunity to reduce operative expenditures within ORANO’s next ISR mining project in Mongolia.

Jan 1, 2020

By G. P. van Greunen

"The rehabilitation of underground excavations has been undertaken as long as mining has existed. The conventional methods have proven to be dangerous, time consuming and expensive. During the construction of Styldrift Mine at Royal Bafokeng Platinum several vertical and horizontal excavations had to be rehabilitated. With a zero tolerance attitude towards working in unsafe conditions, together with a non-negotiable timeline to construct and ramp up the mine, the project team could not rehabilitate these excavations using conventional methods. This paper details the approach used to rehabilitate excavations using remote methods and how it was adapted to suit varying operating conditions and requirements - ensuring that no person ever entered an unsafe excavation before it was fully rehabilitated and safe. INTRODUCTION Styldrift Mine is an expansion project of the Royal Bafokeng Platinum group. It is located in South Africa in the North West Province some 10 km south of the Sun City resort (Figure 1). The mine consists of a twin shaft system (Main Shaft and Services Shaft). Capital construction of the shaft and associated infrastructure started in 2009 and is projected to be completed during 2020. The designed steady state production capacity of the shaft is 230 ktpm of Merensky ore. Production ramp-up commenced in 2017 with steady state production set to be achieved 36 months later in the fourth quarter 2020.Merensky Reef was intersected at a depth of 600 m below surface and the shaft design has a mean mining depth of 630 m. The project was approved for execution in 2008 on the basis of a suitable mine design and bankable feasibility study. One of the main excavations that required rehabilitation was an underground reef silo, Silo 4. It is a key piece of infrastructure on the critical path to allow steady state production at Styldrift Mine to be achieved. During construction excessive scaling within the silo along its 64m length necessitated urgent rehabilitation to be able to meet the ramp-up schedule. The criticality and urgency of these excavations prompted the project team to reduce the risk of failure while ensuring safe and cost-effective rehabilitation. This paper will focus on the rehabilitation of Silo 4 while capturing the essence of the learnings of all the excavations that were rehabilitated remotely."

Jan 1, 2019

By K. Meshinchi Asl

In this study the effects of T4 and T6 heat treatments on microstructural characteristics of AZ91 alloy containing Rare Earth elements have been investigated. Formation of intermetallic Al1 1RE3 needle shape particles which have a good thermal stability reduces both formation of ß(Mg17A112) and discontinues precipitation in AZ91 alloy which are dominated at the grain boundaries and are responsible for poor mechanical properties specially in elevated temperatures. For AZ91-RE samples both T4 and T6 heat treatments led to a continuous precipitation of ß particles at the grain boundaries after aging. However, in AZ91 samples (with no Rare Earths) precipitation was discontinuous at grain boundary areas. This type of precipitation is one of the main reasons of poor mechanical properties of this alloy at elevated temperatures.

Jan 1, 2007

By Mike Broczkowski, Laura Dewhirst, Kieran Large, Angelo R. Fernando, Heather Daigneault, Jim Johnson, Randy Wiens

The radioactive isotope radium 226 is a contaminant of potential concern in effluent waters from metal mining operations in Canada. Acceptable release levels of radium 226 are governed by Metal and Diamond Mining Effluent Regulations. Since radium is invariably present as a companion element in uranium ore, monitoring and controlling of radium 226 is a must for uranium mining operations. Measurement of radium 226 is traditionally carried out through a radiochemical technique involving selective co-precipitation of radium with barium sulphate followed by alpha spectroscopy for quantification. As of 2010, Cameco has also been using an ICP-MS based radium analysis method developed in collaboration with a research team at Trent University, Peterborough, Ontario. This method, which is highly automated and requires significantly less sample handling, with improved turn-around-times, is being used by Cameco site laboratories at the McArthur River and Cigar Lake mines as well as the Port Hope Conversion Facility. This paper compares the benefits and drawbacks of this new method, compared to the traditional alpha counting procedure drawing from almost ten years of field experience.

Jan 1, 2020

By B. H. Sadagah

"Construction of mountain roads at north westerly Saudi Arabia is a difficult task in rugged terrains, where the rock masses are steep slopes, and full of geomorphological constraints.Werka descent lies at the north west region of Saudi Arabia. The Werka descent, constructed four years ago harmed due to rainstorm. The rock masses are metabasalt and metaryolite tuff rocks. The road is eight m-wide, surround by unsupported sharp manmade slope cuts, reaches up to 15 to 40 m height on both sides. Failures took place at both sides of the road, and blocked it. The road of almost 2 km long subjected to all modes of slope instability such as rockfalls, manmade slope failures and debris flows in the absence of the remedial measures. The very precipitous 40 m-high rock slope-cut along the road has no benches, backed by a natural slope of almost 80 m height. Both types of slopes suffer from rockfalls and slope failure’s incidents, frequently took place mainly in rainy seasons. The steep manmade rock slope cut is less than 1 m close to the road, with no ditches, form a potentially source area for rockfall’s hazards.Intensive geotechnical study includes utilization of the RMR and GSI rock masses classifications indicates that the rocks are fair to poor quality. The DIPS, RocFall, Swedge, RocTopple, RocPlane computer program, in addition to GIS and DEM image utilized to perform modeling and deterministic analysis, in order to suggest the mitigation measures for the natural and manmade slope cuts and rockfalls. The seismic coefficients of 0.1 to 0.4 taken into consideration in modeling processes. Input parameters to model the rockfalls and slope failure’s characteristics were studied such as GSI, block size; seeder points, locations of fallen blocks; slope angle, restitution coefficients, and slope roughness. The programs modeled the proposed location, height and energy of the rockfall barriers, collectors, and rock bolts. Two manmade slope cuts studied and modeled utilizing the integrated techniques were to eliminate the risk of slope failures and rockfalls through the construction of remedial measures, this is the study objectives."

Jan 1, 2015

By Robert Boutilier

For more information on what the social licence means, see the following: Joyce, S. and Thomson, I. 2000. Earning a social licence to operate: Social acceptability and resource development in Latin America. The Canadian Mining and Metallurgical Bulletin, 93(1037) Nelson, J. and Scoble, M. 2006. Social License to Operate: Issues of Situational Analysis and Process. Vancouver, BC: Department of Mining Engineering, University of British Colombia. Thomson, I. and Boutilier, R.G. 2010. The Social License to Operate In P.Darling, (Ed.), SME Mining Engineering Handbook: Littleton, CO: Society for Mining, Metallurgy and Exploration. Much of what has been written and said about the social license to operate focuses on what the company has to do or not do. But the social license is a two-sided relationship. We also need to look at what the community has to do, or not do, in order to be capable of issuing a social license that is meaningful.

May 1, 2010

By A. Mukherjee, C. Kelly, B. Markovich, G. E. Agar, G. E. Robertson, F. Khan, B. Shea

"Laboratory batch flotation tests were performed on a sample of bulk slow cooled converter matte (Cu:Ni = I) to optimize the time in each of the separation stages. Numerical simulations were carried out to estimate a continuous circuit material balance for the conditions selected. An experimental simulation of a continuous circuit (locked cycle test) readily came to steady state and there was reasonable agreement between the numerical and experimental results. The use of nitrogen as the flotation gas and the addition of collector to the grinding mill minimized the oxidation of chalcocite, which has previously resulted in increasing circulating loads, and led to a stable circuit with very low weights in the recycle streams.IntroductionINCO Limited developed a flotation process for separating the components of copper-nickel matte [Sproule, Harcourt and Rose 1945; Sproule, Harcourt and Renzoni 1960] in 1945 to replace the Orford process and continues to use the flotation process in almost the original mode to this day. Initially the matte processed was the result of smelting a nickel concentrate that analyzed about 12% nickel and 2% copper and all of the recycle material that was generated in the smelting process. The matte generated analyzed about 25% copper and 53% nickel, roughly 2: 1 nickel to copper. This matte was blown in Pierce-Smith converters to be sulfur deficient in order to produce a metallic phase that collected the precious metals contained in the smelter feed [Wilson and Stratton-Crawley 1991]. This process continued with little change until 1994 when the separation of chalcopyrite from pentlandite in the Copper Cliff mill was discontinued after 63 years of operation. As a consequence of the elimination of the primary separation of chalcopyrite from pentlandite in the milling process a bulk concentrate was produced for smelting. Bulk concentrate smelting came into practice in 1994 as part of the initiative to meet government legislation that restricted the emission of sulfur dioxide to the atmosphere. Previously, the copper concentrate was smelted in an INCO oxygen flash furnace which resulted in the capture of a high strength sulfur dioxide stream from which liquid sulfur dioxide was produced. Nickel concentrate was smelted in reverberatory furnaces that produced low strength sulfur dioxide gases which were difficult to treat. The action taken by INCO to meet the environmental constraints was to smelt a bulk concentrate in oxygen flash furnaces which would produce gases suitable for the production of liquid sulfur dioxide and another stream that was high enough in sulfur dioxide to be readily converted to sulfuric acid [Bell et al 1990]. The end result of this decision was that all the copper-nickel separation would be done in the matte separation plant."

Jan 1, 1996

By J. W. Reynolds

"The use of approved fire-resistant hydraulic fluids in equipment operating underground was made mandatory in British Columbia by amendment to the Provincial Mines Regulation Act effective January 1, 1975. This paper covers the action taken to achieve this, in the largest underground metal mine in British Columbia. Some evaluation of costs and effects based on experience to date is included.BackgroundAn amendment to the Mines Regulation Act of the Province of British Columbia was passed in July 1974 as follow s: "" Rule 111 (b) Hydraulic Fluids. After the first day of January 1975, all hydraulic fluids used in equipment operating underground shall be of a fire-resistant type accept able to the chief inspector.""Unquestionably, its intent was justified as a safety improvement measure. The list of fires in mines involving machinery where hydraulic fluid was a factor in the fires is long and sobering. In British Columbia, in a 22-month period from 1972 to 1974, there were six fires in metal mines resulting in extensive equipment damage and injury to four workmen. Nevertheless, no provision was made for research or development of systems modifications compatible with conditions encountered in B.C. and, as late as June 1977, the Mining Association of British Columbia continued to argue that fire suppression systems should be considered sufficient until a universal suitable hydraulic fluid could be developed. The sole concession was to issue permits for continued use of mineral oil in equipment bought prior to 1975 in order to allow producing operations to continue. The burden of developing the necessary technology was laid on the industry.The Sullivan Mine at Kimberley, the largest and longest established underground mine in the province, and Cominco's most important source of ore s for its smelter at Trail, B.C., was at the outset of a conversion from conventional to trackless mechanized mining methods in pillar recovery operation s. Introduction of fire-resistant hydraulic fluid s had to be done in a period of change, in many instances on equipment for which no data existed, and called for research which had to be done while retraining the work force.The introductory phase is complete. All equipment is on FRF, the requirements of Rule 111(b) are being satisfied, and a number of research and development programs continue."

Jan 1, 1980

By E. Mohammadi Zahrani

In this study, Mg-doped fluorapatite (Mg-FA) nanopowders were prepared through a sol-gel, technique and characterized. Designated degree of Mg2+ ions incorporation into the apatite structure was indicated by the x value in the general formula of (Ca10-xMgx (PO4)6F2), where x=0, 0.25, 0.5, 0.75, and 1. XRD, AAS, FTIR and TEM techniques were utilized to characterize the synthesized nanopowders. In vitro bioactivity of the powders was evaluated in simulated body fluid. Powders had a crystallite size less than 100 nm. It was concluded that Mg-substitution could alter bioactivity and dissolution behaviour of Mg-FA. These two parameters were proportional to magnesium content of the powders.

Jan 1, 2010

By M. A. Cawley, J. W. Jordan

"IntroductionTHE ORE PILLARS in the lower ""A"" ore body of Waite Amulet Mines, Limited, can be divided into two groups, those mined in the open by sub-level blast-hole methods, and those to be mined .against coarse rock fill. Of the three pillars in the last group one has been mined and is dealt with in this paper. The method of mining pillars against coarse rock fill was suggested by the late Dr. Oliver Hall, who was Consulting Engineer for the Company when recovery of No. 2 East pillar was being planned.HistoryThe Waite Amulet mine is in northwestern Quebec, nine miles north of the town of Noranda. The property is approximately three miles long by one mile wide. The present Company, which was formed by the amalgamation of Amulet Mines, Limited, and Waite Ackerman-Montgomery Mines, Limited, commenced operations in the summer of 1937. In the fall of 1939 a new .flotation mill was erected with a capacity of 1,200 tons per day, which was increased to 1,800 tons per day in 1943. The mill is presently operated at 1,400 tons per day.To date, seven orebodies have been found, the major ones being Lower A, East Waite, and Waite. Three separate concentrates are produced, copper, zinc, and pyrite. Total tonnage mined to the end of 1954 from all orebodies has been 7,340,000 tons, which averaged 4.6 per cent copper, 5.3 per cent zinc, and 0.037 oz. gold and 1.27 oz. silver per ton."

Jan 1, 1955

"In the present study, the reduction behavior of composite pellets comprising of iron oxide, synthetic graphite and slags were investigated in a laboratory-scale horizontal tube furnace. Two different types of slags indicating silicate base and aluminate base slags were chosen to examine the effect of slag chemistry on the reduction behavior of pellets. Slag composition of binding materials has influences on the reactions occurring in composite pellets during direct reduction. In-situ high temperature visualization approach was used to observe the slag / iron / carbon interactions at 1773K (1500°C). The off-gases were measured by means of infrared analyzer to determine the reaction rates of the pellets. Different physical appearances during the in situ reaction inferred a strong correlation between the slag composition and internal reactions. In addition, compression tests were conducted to examine physical strength of the pellets. This investigation was carried out to establish feasibility of physical property control of pellets by selecting optimum slag compositions of binding materials INTRODUCTIONCurrently, most of the iron ore mines have facilities that make an ore more usable for the blast furnace operation by improving its physical properties (e.g. pelletizing and sintering). However, during the process, a large amount of fuel is supplied to indurate materials which consequently deteriorate energy efficiency and produce more CO2 emission. Along with increased interests, direct reduced iron (DRI) making process; simply without coke oven or sintering process, has opened the era of clean and environmental friendly iron making process. While some of the established DRI technologies such as Midrex and HYL were restricted to certain locations where natural gas is abundant, coal based technologies using Rotary Hearth Furnace (RHF) such as FASMET and ITmk3 have been developed with regardless of expensive fuel deposit. In addition to the direct use of pulverized non coking coal and fine iron ore, RHF process also has advantages of utilizing waste materials such as EAF dust, biomass and recycled plastics. Nevertheless, there are still many challenges in the coal utilizing technologies as the unprocessed coal and the waste materials contain huge volatiles and ashes. Although recent investigations on volatiles in a RHF process (Sohn and Fruehan, 2005, 2006) have indicated the benefits of coal in terms of iron oxide reduction and have shown feasibility of multi-layer process, carbon composite pellets still have disadvantages because of its weak mechanical bonding strength. As the mixed system with carbon and oxides generates intermediate gases (e.g. CO and CO2) between solid particles, it is difficult to keep its physical state without the help of binding materials. In this reason, industries have been tried to use various binding materials such as bentonite, kaolinite and Portland cement. However, they are still struggling to find out new materials that provide not only sufficient mechanical strength but also metallurgical properties, such as porosity, reducibility and swelling throughout the reduction reaction. Recently, Canadian researchers (Aota et al, 2006) observed enhanced mechanical strength of pellets by using high alumina cement as a binder and concluded that the method could be used to recycle EAF dust as well, but in depth mechanism of reinforced strength has not been concerned. Most of the ashes coming from binders formulate certain type of slag during the reduction process due to its incombustibility. Thus, observation and regulation of slag property is an essential for the control of carbon composite pellet. Yet, only a little thermodynamic consideration from the perspective of slag chemistry has been adapted in the iron and steel making industries as ash has been easily ignored for its tiny proportion. In this study, effect of CaO-SiO2- Al2O3 slag system on the reduction of iron oxide was investigated in terms of"

Jan 1, 2012

By M. Sagedahl

The off gas from a smelter is cooled and dust removed in an electrostatic precipitator before approximately 95% of the sulphur dioxide (S02) is converted to sulfuric acid. However, the tail gas may need to be polished to remove the rest S02 to meet demands. A flue gas desulphurization (FGD) system, as usually applied to S02 removal on coal and oil fired Power Station, is suitable for polishing tail gases from copper smelters. The ALSTOM Seawater FGD process makes use of the alkalinity in the seawater to absorb and neutralize S02. Before being returned to the sea, the seawater is treated to comply with environmental regulations. As the ALSTOM Seawater FGD process uses no reagent and produces no byproduct, it is extremely cost-effective for coastal installations. The first SWFGD plant started operation in 1968. Over 60 of these units have been installed worldwide. The ALSTOM Seawater FGD process removes S02 from flue gas flows corresponding to a total of 70,000,000 Nm3 /h. Suitable for thermal power stations, smelters and oil refineries, ALSTOM Seawater FGD plants efficiently treats flue gases in the range of 300,000 Nm3/h to 2, 700,000 Nm3 /h per FGD plant, containing 20 - 6,500 ppm of S02.

Jan 1, 2007

By J. O. Wheeler

"DEFINITION OF THE REGION, ITS BOUNDARIES, AND PHYSICAL AND GE'OLOGICAL CHARACTERISTICSTHIS PAPER concerns the Western Cordilleran region, embracing most of British Columbia, the southern half of Yukon Territory and the southwestern most part of the District of MacKenzie. It excludes Vancouver Island and the Queen Charlotte Islands, which are discussed in a background paper on the Pacific Continental Shelf. The region is bounded on the south by the northwestern United States, on the west by the continental shelf and Alaska, on the north by the front of the Ogilvie Mountains, on the northeast by the axis of the MacKenzie Mountains and on the east by the Rocky Mountain Trench.The region is dominated by two mountain chains that con tain icefields and glaciers: the St. Elias, Coast and Cascade Mountains in the west; the Selwyn, Pelly, Cassiar, Omineca and Columbia Mountains in the east. The Intermontane region between these mountain chains consists of lower mountains and plateaus. In the mountains, the region above the timberline and many of the steep valley-walls provide good exposures of rock, but these areas are subject to rockslides and landslides and in winter to snow avalanches. Much of the Western Cordillera was covered by ice-sheets at various times during the Pleistocene epoch. Consequently, the larger valleys in the mountains and much of the Intermontane region contain much glacial drift and alluvium and only limited exposures of rock. This same terrain in the Southern Cordillera, however, is the most favourable for agriculture. Parts of the region, particularly in the two mountain chains, are heavily forested. Elsewhere, the forest cover is less, with grassland prevailing in the south and tundra in the north."

Jan 1, 1969

By J. O. Wheeler

"DEFINITION OF THE REGION, ITS BOUNDARIES, AND PHYSICAL AND GE'OLOGICAL CHARACTERISTICSTHIS PAPER concerns the Western Cordilleran region, embracing most of British Columbia, the southern half of Yukon Territory and the southwesternmost part of the District of MacKenzie. It excludes Vancouver Island and the Queen Charlotte Islands, which are discussed in a background paper on the Pacific Continental Shelf. The region is bounded on the south by the northwestern United States, on the west by the continental shelf and Alaska, on the north by the front of the Ogilvie Mountains, on the northeast by the axis of the MacKenzie Mountains and on the east by the Rocky Mountain Trench.The region is dominated by two mountain chains that con tain icefields and glaciers: the St. Elias, Coast and Cascade Mountains in the west; the Selwyn, Pelly, Cassiar, Omineca and Columbia Mountains in the east. The Intermontane region between these mountain chains consists of lower mountains and plateaus. In the mountains, the region above the timberline and many of the steep valley-walls provide good exposures of rock, but these areas are subject to rockslides and landslides and in winter to snow avalanches. Much of the Western Cordillera was covered by ice-sheets at various times during the Pleistocene epoch. Consequently, the larger valleys in the mountains and much of the Intermontane region contain much glacial drift and alluvium and only limited exposures of rock. This same terrain in the Southern Cordillera, however, is the most favourable for agriculture. Parts of the region, particularly in the two mountain chains, are heavily forested. Elsewhere, the forest cover is less, with grassland prevailing in the south and tundra in the north."

Jan 1, 1970

By M. Jiang, X. Fan, W. X. Chen, Z. K. Guo, H. H. Zou

"Some improvements are carried out for elasto-plastic model by taking the shear dilation effects and relaxation effects of deep rocks into accounted. The high pressure equations of states with Mie-Grüneisen form are also introduced to describe the relation of pressure-volumetric strain. Numerical simulations of free field responses for deep underground explosions are conducted by using the user subroutines which compiled by means of the secondary development functions of LS-DYNA9703D codes. It is indicated that the dynamic responses of free field are well simulated based on this improved elasto-plastic model, and the analytical results are in good agreement with the data of U.S. Hardhat nuclear test.INTRODUCTIONDynamic behaviors of deep rocks for underground explosions are obviously different from that of shallow underground explosions and have aroused great attentions of international experts who work for rock engineering. The dynamic models of deep rocks could be roughly divided into classic elasto-plastic model and fracture damage model according to different theoretical foundation. M. E.Kipp and D. E.Grady et al. are the outstanding representatives who engaged in the researches of fracture damage mechanics. Researches of dynamic problems for geomaterials were carried out by C.C.Grigorian and the conclusion that incompressible elasto-plastic medium model could not be used to solve the problems of closed underground explosion was derived, and therefore C.C.Grigorian model was proposed. In this model, C.C.Grigorian assumed that the average hydrostatic pressures and the densities of medium had one to one relationship, and the path of loading or unloading is different from each other. For shear deformations, analytical solutions of the problems were derived according to the model which was slightly different from Prandtl-Reuss model, the constitutive equations were closed by Mises-Schleiher constitutive model. However, the analysis showed that there were two inadequacies in C.C.Grigorian model. Firstly, the shear dilation effects of fractured medium after wave front could not be considered. Secondly, the relaxation characteristics of the rocks in fractured region were not taken into account."

Jan 1, 2015

By L. Gasser, N. Bellinger, H. Awatta, A. Merati

As aircraft age, the extent of interactions between fatigue and other damage mechanisms, such as corrosion and fretting, increases. At present, however, there is no generally accepted methodology within the Aircraft Structural Integrity Program (ASIP) framework to account for the effects of these interactions on life and the residual strength of aging aircraft components. A comprehensive program is being carried out by the National Research Council Canada in collaboration with Analytical Processes/Engineered Solutions, using the Holistic Structural Integrity Process (HOLSIP) to address time and cyclic load issues. This approach predicts the evolution of a discontinuity state in a material from production to retirement. This paper summarizes the results of a study on the 2024-T3 aluminium alloy in different forms (clad and unclad), thickness, and specimen geometry. This study consisted of identifying the microstructural features associated with crack nucleation sites and relating them to the testing parameters and fatigue life. Several coupons were fabricated and fatigue-tested. The fracture surfaces were carefully examined, and the physical characteristics of the microstructural features found near the crack nucleation sites were analyzed. Effect of stress level, loading direction, coupon geometry and surface condition on the number of crack nucleation sites, and fracture origin size has been discussed. Four distinctive mechanisms were found to be responsible for crack nucleation: for unclad materials constituent particles, oxide residue, surface irregularities and for clad samples the clad layer was the sole fracture origin.

Jan 1, 2006

By Paul-Henri Girard

La Mine Agnico-Eagle division Laronde situé à Cadillac, est un producteur d?or, d?argent, de cuivre et de zinc. Cette propriété est situé dans les cantons Bousquet-Cadillac le long d?une des ceintures géologiques les plus productives au monde. La mine Laronde a débuté la production en octobre 1988 à un rythme de 1360 tonnes par jour. Ensuite, elle a augmenté son rythme de production successivement à 1800 TPJ en 1990, 3300 TPJ en janvier 2000 et 4500 TPJ en octobre 2000. Agnico-Eagle, fondé par feu Paul Penna, a toujours eu comme politique la participation des employés aux décisions de la compagnie pour le déveleppement de celle-ci. Cet écrit va permettre de mieux comprendre la façon dont la division fût développé.

May 1, 2001

By G Zahary

THE most acceptable approacl1 to analyzing rock behaviour, at the present time, is based on the application of principles of mechanics and strength of materials. Analyses have been made in which the criterion of failure is based on maximum stress (1) and on Mohr's rupture theory (2). If such analyses are to be carried out, the mechanical properties of the rock must be known within acceptable limits. Although an adequate correlation of laboratory test results with field conditions has not been established, test results have been published (3) on the basis of their comparative value. That is, test results may be useful for comparing the behaviour of different rocks under similar loading conditions or of a particular rock under different loading conditions. This study aims at establishing some of the mechanical properties of an andesite rock by testing specimens cut _from diamond drill core. Drill core (EX) was provided from run-of-mine drilling by New Dickenson Mines Ltd. and Campbell Red Lake Mines Ltd.

Jan 1, 1963