Search Documents

By R. Ghomashchi

Wear, fatigue and corrosion are the most widely encountered modes of failure in materials used in engineering applications, including aero-gas turbines. Although wear is distinctly classified as adhesive, abrasive, erosive, fretting and so on, there are usually more than one wear mechanism involved in the failure of components in service because there are many systems and materials variables active in materials wear that makes it more difficult to study. This is further complicated by the discrepancies between the results of laboratory tests and field data. The present investigation was set up to examine the wear characteristics of M50 and T1 high-speed steels at both room and elevated temperatures to draw a thorough understanding of the wear behavior of this class of high-speed steels. This article focuses on the mechanical and microstructural characterization of wear for T1 and M50 high-speed steels using a pin-on-disk wear machine.

Jan 1, 2005

By G. Shen, W. R. Tyson

In most fracture toughness test standards, such as ASTM E 1290 and BS 7448, crack-tip opening displacement (CTOD) is measured by using three-point bend (SE(B)) or compact (C(T)) samples with deep cracks. The loading mode and crack depth in these tests sometimes are different from that of pipelines. Pipelines usually have shallow defects and experience tensile loading when the supporting ground moves. As a result, the CTOD measured by these samples is lower than that of pipeline in tension. Recent researches suggest using single-edge-notch tension (SE(T)) samples to measure fracture toughness for pipelines. In the present study, shallow and deep SE(T) samples under fixed grip loading were analyzed by using the finite element technique. An equation to relate the CTOD to the area of the load/plastic crack mouth opening displacement (CMOD) is proposed. With this equation, the CTOD of a SE(T) sample can be evaluated by measuring the area under the load/plastic CMOD curve of a SE(T) sample.

Jan 1, 2005

By Simon C. Dominy, Patrick R. Stephenson, Alwyn E. Annels

Abstract - The often complex, erratic, and localized nature of gold is a common feature of many vein-style gold deposits. This style of mineralization is often referred to as being nuggety or possessing a high-nugget effect. As a result of these complexities resource estimation is difficult and in general, only Exploration Results can be provided or an Inferred Mineral Resource estimated from surface drilling data alone. Underground development, further drilling, and probably bulk sampling will be required to delineate Indicated and Measured Resources. Tonnages can generally be estimated from diamond drill and development information with a reasonable degree of confidence. Grade is much more difficult to define with confidence because it is commonly highly erratic and discontinuous in nature. The dependency of higher confidence Resource categories on development information may create a Catch 22 situation, with funding for such development often depending on the prior definition of at least Indicated Resources. There are no easy solutions to these challenges posed by high-nugget effect deposits, and it is important when classifying and reporting not to downplay the uncertainties often associated with Mineral Resource and Ore Reserve estimates for such deposits. However, in common with all deposit types, if the principles that underpin the estimation, classification, and reporting procedures are borne in mind and common sense applied, most issues can be satisfactorily resolved. This paper discusses the classification and reporting of Mineral Resources for high-nugget effect gold vein deposits within the framework of the JORC Code (JORC, 1999).

Jan 1, 2001

By Min-Yuan Cheng

Landslides not only cause interruption of road traffic but also cause damage to passing by vehicles and injure people in Taiwan. Due to the budget limitation of government, the overall assessments and maintenance of all road slops cannot be fulfilled. Priority of road for maintenance is a crucial task for road maintenance department to identify. The purposes of this research are to develop an assessment method for the landslide risk and to make strategies to maintain or repair the slopes along mountain roads. To aim both needs to take into account the environmental conditions of the slopes, the engineering measures for stabilizing road slopes, the transportation issues, and the human concerns when dealing with the slopes maintenance along the mountain roads. This study firstly establishes the Landslides Damage Risk Evaluation Model (LDREM) to calculate the risk of slope failure, considering the probability of landslides, temporal probability, spatial impact probability, the value of human life, transportation time increased, and travel cost due to detour etc., and then the loss of life and transportation can be calculated. Secondly, based on the value of risk and the risk evaluation, considering the risk acceptance criteria for loss of life could provide assistance for road maintenance department to determine the priority of mountain roads for maintenance.

Aug 1, 2013

By D. L. Millar

The hydraulic air compressor (HAC) is driven only by water, held up by a dam, to create relatively low head (typically 10-20 metres), such that the developed hydropower is used to cause flow in openings deeper underground. Air is entrained in the water at the inlet to the sub-surface openings (an air to water volume ratio of 1:1 is reported to be optimal) and is compressed as it is carried along by the deepening water flow. At depth, and with lower water velocities arising from larger cross sectional area tunnels, air bubbles separate out of the water flow and are collected in a receiver space above the flowing water. Water, free of air, then passes back up a return shaft (up-pipe) and rejoins the river or stream flow. In principle, an HAC can produce any pressure and flow rate required, given large enough shafts and enough water supply with head sufficient to overcome frictional resistance in the sub-surface tunnels. Practically, as air solubility in water increases with pressure, HAC installations with depths greater than 100 metres may lead to higher rates of compressed air loss, without special separation measures. A modern HAC application for mine refrigeration and cooling is presented.

Aug 1, 2013

By G. Q. Liu

"The application of oxygen-enriched cyanidation to three Canadian gold ore samples has been investigated. The results showed that the use of oxygen can improve gold dissolution kinetics, reduce grinding time, and lower cyanide and lime consumptions. To obtain the same gold extraction, the required cyanide leaching time was reduced from 48 hours in slurry containing 8 ppm O2 to 12 - 24 hours in 20 ppm O2 slurry. Reagent consumptions were reduced by 23 - 37% for cyanide and by 35 - 54% for lime. There was little advantage to further increasing the dissolved oxygen to 32 ppm from 20 ppm. Gold extraction from the +200 mesh fraction improved 4 - 14% in oxygen-enriched slurry. A general kinetic model derived from the cyanidation of three ore samples can be described by the following equation: <equation>where E is the gold extraction (%) at time t (hours), EI is the ultimate gold extraction (%) , and &apos;P and k are constants depending on cyanide concentration, level of dissolved oxygen, and the characteristics of the ore samples. Comparative studies of conventional carbon adsorption and carbon adsorption in oxygen-enriched slurry have also demonstrated that oxygen enrichment resulted in more favourable conditions for gold adsorption."

Jan 1, 1995

By R. Binning

"Economic high density mineral reclamation and subsequent transportation of solids through a pipeline presents many formidable engineering problems.Mineral reclamation system design by theoretical formulas is almost impossible because solids composition, ie. concentration, velocity, moisture content, solid size, etc. can only be controlled within a broad pumping range.Traditionally this has restricted pumping to relatively dilute slurries whereas it is usually preferred, because of economic considerations to reclaim as high a concentration as possible.At Toyo/De-Velde Corp. we recognized these pumping limitations and began to develop and manufacture a range of standard and auxiliary equipment that would exceed these technical restrictions.MATERIAL RECLAMATION & PIPELINE INJECTIONTo minimize fluid usage and increase material reclamation efficiency we designed a submersible dredge mixing pump that uses most of its energy to pick up material from rest, mix it with fluid into a highly concentrated slurry then push it firmly into a pipeline.Where material is too compacted to be mined by the standard submersible mixer pump, auxiliary high torque self contained submersible excavators can be fitted around the periphery of the mixer pump. This is to facilitate excavation and break up of the compacted material into a slurry.High flexibility of this system can be achieved by combining the many equipment variations available into the most efficient format to fit individual site requirements.Whatever combination of equipment is selected, torque is nullified by counter rotating excavators against each other. This increases effective excavator/material bite torque but also allows mixer/excavator rig suspension by cable for deep water material recovery."

Jan 1, 1985

By Michael T. G. Brown

Syncrude Canada Ltd. has recently completed construction of its ambitious tar-sand mining and processing facilities at Mildred Lake, Alberta. The Syncrude site is approximately 48 km (30 miles) north of Fort McMurray near the west shore of the Athabasca River. The Syncrude operation involves the open-pit mining of approximately 270,000 tonnes (300,000 tons) of tar sand daily using draglines and a conveyor system. Bitumen is extracted from the tar sand, upgraded to oil-gas and transported to refineries in Edmonton and other locations for final processing . The Beaver Creek Dam forms part of the mining facilities for the Syncrude tar-sand mining operation. Water from Beaver Creek is diverted from the open-pit mine site south to the Athabasca River via Ruth Lake and the Poplar Creek Dam. General site layout is shown on Figure I . Design of the dam was completed by R. M. Hardy and Associates Ltd. of Edmonton, Alberta (now Hardy Associates (1978) Ltd) . Construction was undertaken during the summers of 1974 and 1975 under the direction of Canadian Bechtel Limited, managing contractors for Syncrude Canada Ltd. Total length of the dam is approximately 2.8 km (1.7 miles), with a maximum height in the order of 16 m (50 ft) The Beaver Creek Dam is located in a broad, flat, poorly drained valley. About 50 per cent of the site is covered with treeless peat deposits, which ranged in thickness from in excess of 5 m (15 ft) at the east end of the dam to less than 1 m (3 ft) at the central portion. The peat deposits overlie Pleistocene meltwater sediments on top of clay/clay shales of the Clearwater Formation and the tar sands of the McMurray Formation. The peat deposits and high groundwater levels at the site combine to make the excavation and construction of a conventional rolled clay cutoff impractical. For these reasons, the slurry cutoff trench technique was utilized to produce an efficient and effective seepage cutoff under various sections of the Beaver Creek Dam .

Jan 1, 1979

By Dani J. Alldrick, Alastair J. Sinclair, Colin I. Godwin

"The Stewart mining camp has a long history of precious and base metal mining. The camp is abundantly mineralized, with more than 200 widespread, varied, vein prospects, deposits and orebodies. These show wide variations in the mineralogy of ore, gangue and alteration assemblages, and wide variations in textures and structural settings. This report establishes the timing of the different metallogenic epochs and suggests a specific exploration application for systematic leadisotope analyses.Galena lead isotope ratios from a range of mineral occurrences indicate that all these varied deposits formed during two main mineralizing events. Lead isotope data from the Stewart mining camp do not provide absolute ages for the formation of mineral deposits, but the relative distributions of data are consistent with dates determined in other studies. One ore-forming episode occurred in the Early Jurassic and the other in the Middle Eocene. Both metallogenic epochs were brief, regional-scale phenomena. Some deposits from the younger mineralizing episode were emplacedadjacent to or superimposed on the older deposits.Field and laboratory studies show that the two metallogenic epochs are characterized by different base and precious metal suites: Early Jurassic gold-silver-zinc-lead-copper; and Middle Eocene silver-lead-zinc. Therefore, showings of different ages have different base and precious metal potentials and deserve different exploration emphasis. Lead isotope studies provide a reliable, cost-effective method for evaluating the age and commodity potential of small or recently discovered mineral showings and for setting exploration priorities on properties with several varied mineral occurrences. The determination of the age and metal potential of a prospect at an early stage of exploration may govern the urgency, intensity or even the necessity for further exploration work."

Jan 1, 1993

By T. Takahashi, K. Oyamada, Y. Miyata, T. Isoo

The carbonation reaction of steelmaking slag has been known for many years. However, the size of blocks manufactured from this by-product material has been limited due to the difficulty of achieving a uniform reaction throughout the block. Using newly developed conditions, large porous slag blocks (1.0 x 1.0 x 0.5 m) were produced by car¬bonation of steelmaking slag with the optimum amount of water and supplying CO2 deep into slag powder compacted in molds. The development of these blocks has great poten-tial to solve the problem of slag utilization, for example, by recycling slag in large car¬bonated blocks for artificial fish reefs and seaweed cultivation beds. This paper de¬scribes the carbonation reaction, the new process for producing large slag blocks, and the utilization of blocks in past and recent years.

Jan 1, 2004

By Andrew Bamber

Outline ?Background to Mine-Mill Research at UBC ?Mine Mill Integration ?In situ mining methods ?Underground Pre-concentration ?System Design and Supporting Technologies ?Case Studies: ?INCO -McCreedyEast Mine ?Placer Dome ?Porcupine JV ISL Study ?Musselwhite, South Deep ?Falconbridge ?Fraser Copper ?Thayer Lindsley ?Wayside Gold, other scoping studies? ?System Designs ?Summary ?Future work ?Conclusion

May 1, 2006

By Marty Hudyma

Mining-induced seismicity and rockbursting is one of the primary risks in deep mines. Seismic data management software has been created to facilitate analysis of mining-induced seismicity. The Mine Seismicity Risk Analysis Program (MS-RAP) is a purpose built database with mine seismicity analysis tools. One of the primary features of MS-RAP is the creation of seismic hazard maps in quasi-real time. The seismic hazard maps identify areas that are more prone to large seismic events and rockbursts, allowing risk management measures to be focused on the areas of greatest risk. These maps allow mining engineers to be more proactive about identifying and managing seismic related geomechanics risks in mines.

Oct 1, 2009

By M. R. Shadnam

This contribution provides an assessment of research and development efforts to optimize SOx, NOx and mercury capture in flue gas. Coa, characteristics and combustion conditions in a power plant have an impact on the types and concentration of flue gas pollutants. These factors can also affect the amount of pollutant removed. This contribution would also provide a comparative study of the technologies that holistically aim remova, of SOx, NOx and mercury altogether in coal-fired power plants. A portion of this contribution provides background information on regulatory drivers.

Jan 1, 2010

By Roger St. C. Smart, Paul Weber, Joan E. Thomas, William M. Skinner, Warwick Stewart, Stuart Miller

For mine sites affected by acid rock drainage (ARD) or with a potential future ARD issue, the prime consideration is not only the classification of different waste rock as potentially acid forming or non acid forming but also the peak acid (and metal) release rates and expected ARD duration during which effective ARD management and acid neutralisation capacity (ANC) are required. Methods for assessment of this ANC (e.g., Sobek tests) are already available but can be unreliable in ARD containing significant proportions of framboidal pyrite or iron carbonates. The measurement of negative ANC values and the release of S to solution showed that significant sulfide oxidation may occur prior to and during testing in samples containing reactive (particularly framboidal) pyrite resulting in serious underestimation of the original ANC. A simple methodology with dissolution in Ar-purged water before ANC testing, removing ferrous salts, and sulfate assay after ANC testing corrects these effects. Results also showed that a significant lag period (up to 432 h) may be needed for complete hydrolysis of Fe associated with the standard Sobek ANC testing of, for instance, siderite. Hence, the ANC of iron carbonates is usually significantly overestimated. By filtering and the addition of H202 until there was no subsequent pH drop (due to Fe hydrolysis reactions), followed by back titration to pH 7.0, the ANC for siderite was similar to the ANC determined after 432 h lag by the Modified Sobek ANC test and to the mineralogical carbonate ANCcarb determined by calculation based on electron probe micro-analysis. A chemical ANC calculation, based on neutralising cations released to solution, has provided a method to quantify the short-term ANC of carbonates and silicates in simple mixed mineral assemblages and waste rock samples. Results showed that silicate ANC can be more important in short-term neutralisation than carbonate ANC in low carbonate samples. In the longer-term, decreasing sulfate and metal loads with increasing pH values suggests that eventually sulfide acidity generation rates will match the longer-term inherent acid neutralisation rates of the sample derived from silicates. A kinetic ANC measurement for silicates, after steady state dissolution is reached, that indicates the number of hydrogen ions neutralised/m2/yr has been developed. These values can be used in estimates of the net acid production profile from wastes with low (and decreasing) pyrite content after the short-term ANC is exhausted.

Jan 1, 2004

By Roger J. Goodman

"Major industrial restructuring, which started to manifest itself in the mature economies of the Western World and Japan in the 1970s, will accelerate in the 1980s and 1990s. Conventional heavy manufacturing industries will continue to lose ground to lighter processing/assembly operations and the new wave of high technology, information and service sectors. The decline in heavy manufacturing has severely impacted on the steel industries of Western Europe, the U.S.A . and Japan.World trade in metallurgical coal has shifted correspondingly, with declining demand in the mature developed countries being only partially offset by large increases in the steel intensity of the newly-industrialized countries (NICs) of the Far East, Latin America and, to a more limited extent, the Middle East and Africa. These trends will be accentuated in future years with direct implications for the distribution of metallurgical coal trade. This paper discusses, in quantitative terms, such changes in the 1980s and 1990s, and examines the implications for, and impacts on, Canadian metallurgical coal exporters.IntroductionThe twenty-year period from the early 1950 s to the early 1970s was characterized by inexorable growth in consumer demand and industrial expansion in most of the advanced countries of the western world. Long- term forecasting during this period typically used linear extrapolation techniques which , despite their simplicity, invariably ended up predicting future demand and production level s with uncanny accuracy. Times have changed!The last decade has been characterized by a n abysmal failure of our economies to respond to simple long-term, linear growth patterns. We appear to have entered a new world in transition, where we can observe a wave of dying or sunset industries reluctantly being submerged by a wave of emerging or sunrise industries.This paper is aimed a t examining the evidence for long-term industrial restructuring trend s. For want of a better word, these so -called, megatrends are then used to predict future demand level s and spatial distribution of steel development and , hence, metallurgical coal trade. It is tempting to correlate the decline in economic activity in the western world with the first Organization of Petroleum Exporting Countries&apos; (OPEC) crisis of 1973. This crisis was probably no more than the straw that broke the camel&apos;s back, as the megatrends and embryo s of major industrial restructuring were already evident. Today these megatrends are merely more apparent and transparent than they were ten years ago.While the concept of industrial restructuring is the new economic buzz word, the process was at work, to a lesser degree even throughout the period of strong economic growth of the post-Second World War boom. Many people still remain convinced that our present-day sluggish economy is just part o f the typical , though rather more prolonged, recessionary cycle. Yet, we have always been part of a dynamic economic system and industry throughout history has been the subject of a continuous process of evolution, restructuring and reconstitution . Now the time is ripe to examine the evidence for such restructuring in order to develop coherent policies of adjustment in this transition from one industrial regime to another."

Jan 1, 1985

By C. Kuehmann, B. Tufts

QuesTek Innovations has applied its Materials by Design® methodology to computationally design a new ultra high-strength corrosion resistant steel. Ferriurn® S53 eliminates the need for toxic cadmium coatings currently used on conventional steels in landing gear systems. S53 has the strength of 300M steel, and corrosion resistance similar to 15-5PH stainless steel. S53&apos;s corrosion resistance improves stress corrosion cracking resistance and reduces susceptibility to hydrogen embrittlement, improving component reliability and providing an opportunity for extended overhaul and repair intervals. Ultimate tensile stress is 1965 to 2000MPa. S53 was designed to be mechanically equivalent to 300M, with the key addition of intrinsic corrosion resistance. Alloy design, microstructural characterization, and mechanical properties are discussed herein.

Jan 1, 2006

By Jonathan Tsang, Ali Merati, Jonathan Beddoes

Due to economic factors, many aircraft in service today have been operating for more than 30 years even though they were initially designed with a service life of 20 years. Improved damage management models are therefore needed for use in life prediction and management of the aging fleets of aircraft. Currently, the generally accepted procedure in fatigue life prediction methodologies is to back calculate the equivalent initial flaw size (EIFS) using established long crack growth data. However, it was observed from studies carried out at the National Research Council Canada that nucleation and short crack growth constitute up to -95% of the fatigue life. As a result, it seems that the significance of the short crack regime has been underestimated and must be further investigated and fully understood before an accurate holistic life prediction methodology can be realized. Unlike long cracks, local microstructural features such as grain boundary, grain size, inter-particle spacing, and texture play dominant roles in the behavior of short cracks. An extensive study has been carried out to evaluate different crack detection and monitoring techniques in the short crack regime for AA2024-T3. The results will be presented in detail.

Jan 1, 2004

"Coupon testing has been used to investigate stress corrosion cracking (SCC) of rockbolts in a laboratory based experimental program. This program has focused on the use of ASTM G39 three- and four-point bent beam coupon specimens, immersed in an acidified sodium chloride test solution containing hydrogen sulfide. The specimens were loaded to a range of stresses from zero, to just above the materials yield strength. It was found that only specimens above an applied stress of 580MPa failed by means of SCC, showing that rockbolts loaded to near their yield strength may be susceptible to SCC in-situ.INTRODUCTIONStress corrosion cracking (SCC) is a failure mechanism that affects material through the growth of hairline cracks when exposed to a corrosive medium while under stress (Jones and Ricker, 1999). SCC has been found to affect rockbolts in the Australian underground coal mining industry and has the capacity to cause the catastrophic failure of ground support systems, potentially leading to falls of ground in underground excavations, injury or death to mine personnel, damage or loss of equipment, and loss of productivity through the loss of roadway access (Crosky et al, 2002).Coupon testing utilises small scale samples that are intended to be indicative of the behaviour exhibited by a material in-situ (ASTM G39). The small scale, and usually high surface area to volume ratio of coupon specimens mean that they corrode at faster rate proportional to their mass, greatly reducing testing times. The small scale of the specimens allows them to be more easily prepared and handled, loaning them to mass manufacturing techniques.A previous study conducted by Vandermaat et al (2012b) into the use of three- and four-point coupon testing in-situ in an underground coal mine failed to result in SCC of the specimens. This paper serves as a follow up laboratory investigation in order to understand why these specimens did not fail. Previous studies into the SCC in rockbolts carried out by Gamboa and Atrens (2003) determined that rockbolt steel has a critical stress threshold of approximately 90% of the material ultimate tensile strength (800-900MPa). This study will focus on this critical stress threshold as a possible explanation for the lack of failure in the in-situ specimens (Vandermaat, 2012b)."

Jan 1, 2015

By L. Mercier, A. El-Hsaeri, L. Amaratunga

Laboratory scale studies of the development and application of high capacity heavy metal ion adsorbents with uniform nanoscale porosity (denoted MP-HMS, mercaptopropyl - hexagonal mesoporous structure) to extract gold from solutions is described. The adsorbents are selective towards gold ions. The adsorption capacities of these materials are also among the highest reported. MP-HMS has shown the capability to adsorb 330-mg gold per gram adsorbent (up to 30% of their weight). Gold uptake by the adsorbent was found to increase dramatically with solution agitation. The adsorbent was found to be extremely effective in adsorbing gold ions from ultra- low concentrations, like those found in mine effluents. Experimental studies indicated that MP-HMS maximum adsorption of gold (99.9%) occurred under all solution concentrations. Another promising attribute of these materials is their favorable adsorption kinetics. The contact time required for 80% adsorption of gold was found to be less than 60 seconds. The efficiency of these nanoporous materials for the recovery of gold from mining effluent is evaluated and their prospect for application in the mining industry discussed. The process thus has the prospect of becoming an efficient and environmental friendly method to recover gold from aqueous solutions, such as gold mill effluents.

Jan 1, 2004

By S. Brophy

Controlled Short Circuit ? Metal Inert Gas (CSC-MIG) welding is a process that can be referred as a "Cold Welding" technology. The CSC process is based on accurate control of the welding wire position, thus the mandatory requirement for the automation of the process. One of the main advantages of the CSC-MIG process is the rapid solidification of the deposited material, resulting in weldments displaying low porosity contents, and enabling the joining of thin sheet materials. These characteristics render this process an ideal one for freeforming of components, where rapid solidification would be efficacious. This presentation will focus on the progress made towards the freeforming of Al-based components in the NAIN laboratory at McGill University. The relationship between the filler metal used, freeforming (deposition) parameters, resulting microstructure and mechanical properties will be presented.

Jan 1, 2011