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By R. L. Christie

"THE ISLANDS lying north of the Canadian mainland, and the large Boothia and Melville peninsulas, form one of the great archipelagos of the world; this sparsely vegetated and nearly unpeopled region extends about 1,500 miles east to west and 1,200 miles from the mainland to the northern tip of the northern-most island. Sea access to most of the islands is restricted by ice to the summer season, and the 'polar pack' ice of the Arctic Ocean presses the year round against the northwest margin of the archipelago. Although the region is remote, the accessibility has greatly increased through a network of weather stations, airfields and air routes connecting with southern centres.The area considered in this paper is that part of the island region underlain mainly by sedimentary rocks. In broad terms, this includes the land and sea areas of the archipelago and the adjacent continental shelf, but excludes the dominantly 'Shield' terrain of Baffin Island, and of Melville and Boothia peninsulas. An impression of the size and potential of this sedimentary region may be gained by comparing some areas: the land area of islands underlain mainly by sedimentary rocks is over 300,000 square miles or about 50,000 square miles greater than the area of Alberta. The total area of the region, including the continental shelf and the inter-island areas, may be double this figure, and may approximate one-seventh of the land area of Canada."

Jan 1, 1970

By D. C. Downing

"I THANK YOU for the invitation which The Mining Society of Nova Scotia extended, originally to Gordon Berry, manager 'of our Point Tupper Refinery, to join you at this meeting and discuss refining and petrochemicals in their relation to this region. There are natural advantages in Nova Scotia which have made possible, and will continue to make possible, sizeable developments both in petroleum refining and in chemicals. Equally, however, as is the case everywhere, there are certain constraints. For clarity in this presentation, I will state some of these constraints right at the beginning. First, of any future developments from now on, only a small proportion of the products can be expected to go into local markets. I can make the point best with a few figures. Petroleum companies all have market forecasts. None ever work out to be perfect, but the trends are relatively predictable and the orders of magnitude are certainly correct. Estimates for the use of all refined petroleum products in the four Atlantic provinces are:"

Jan 1, 1973

By V. I. Lakshmanan, I. G. McColl

"Heap leaching of gold ores in permafrost conditions is feasible provided certain criteria are met. These criteria include relatively short heap leach residence time and the availability of waste heat.This paper describes the conceptual design of such a system for a mining operation in the North West Territories of Canada. The design includes the concept of continuous countercurrent leaching in enclosed ore heaps.Indicative capital and operating costs are given.INTRODUCTIONIn April 1984, Acres Davy McKee Engineering Inc. (ADM Eng.) in association with Ontario Research Foundation (ORF), was invited to carry out a preliminary design, cost estimate and financial analysis to assess the viability of gold heap leaching in a permafrost region in North West Territories, Canada.An orebody was being explored which could, by nature of its mineralogy, be upgraded substantially by crushing and screening in the size range of 1/4 in. to 3/4 in. It was proposed to process the screen undersize through an existing gold mill on site and to treat the oversize material in a heap leach facility to be constructed adjacent to the existing mill.Despite the formidable challenges imposed by isolation, permafrost and harsh winter conditions, the heap leach project was considered worthy of examination because of the relatively high grade of the heap leach material (> 0.1 oz/ton), very short leach times (in the range of 1 to 4 days) and the availability of substantial quantities of waste heat from the diesel generating station on site.Design challenges included the necessity to maintain the permafrost in frozen condition, to prevent freezing of ore and leach solution, to limit size of construction materials to that which could be carried in a Hercules freight plane and to contain water usage at an absolute minimum level."

Jan 1, 1987

By Gregory C. More O'Ferrall

Generally pillars in the Southern African hard rock tabular underground mining environment are designed using either empirical pillar design formulae or numerical modelling (analytical) methods utilizing the Hoek-Brown failure criterion. However, none of the pillar design methodologies employed takes cognizance of weak layers either within the pillar material or in the immediate foundation of the pillar. Over the past few years, the presence of a weak layer either within the pillar material or within the immediate foundation of the pillar has resulted in the closure of one platinum mine (Everest Mine), closure of one chrome mine (Wonderkop Chrome) and large-scale instability in a couple of chrome and platinum mines in South Africa and Zimbabwe. A study has been initiated to better understand the failure mode and strengths of the pillars where pillar failure associated with weak layers occurred. Owing to the infancy of the study into the failed pillar strength and failure mechanism, the purpose of this paper is to highlight the circumstances that led to the collapse of mining sections and a shaft, and the difficulty associated with designing pillars in the Southern African chrome and platinum mining operations.

Jun 1, 2012

By Muhammad Zaka Emad

Cemented rockfill (CRF) is a mixture of rock aggregate and binder slurry. It is a stiff backfill, it is fast curing, its operation is simple, placement rate is reasonably high and no drainage is required. The main demerit of CRF is failure of exposed faces causing ore dilution, which can be associated with the fill placement method. This paper discusses the effects of two placement methods being practiced by mines and numerical modelling is used as a tool to evaluate stability of the backfill column. In the first method, practiced in longitudinal retreat mining of a narrow vein deposit, the rockfill is hauled and dumped into the stope with a LHD scooptram. Once dumped, cement slurry is sprayed into the stope. In the second method, a raise situated centrally above the mined stope is used to convey already mixed CRF into the stope. Stopes are mined out transversely in primary and secondary blocks in a sublevel stoping system. Problems of poor mixing in combination with both placement methods are discussed. The two backfill placement methods are analyzed for blast induced vibration damage using the dynamic Flac3D modelling technique accounting for rock mass and fill damping characteristics, and a pressure wave is used to simulate the blast vibrations. Fill heterogeneity has also been considered for the two cases and results are compared.

Jun 1, 2012

By P. K. Gummer

Gold was fir t di covered on the Seabee property in 1947 by the Con olidated Mining and Smelting Company Limited. Acquired by Claude Resource Inc. in 1984, the property is now being explored by Placer Development Ltd . in joint venture with Claude Re ources. Between Augu t, 1985 and March, 1986, Placer completed 54 drill holes, extending the main o. 2 and o. 5 vein y tern to a depth of 1000 feet below surface and di covering two new satellitic gold zone 800 feet west of the o. 5 gold zone. Drill proven and probable geological re erve in four zone ( os. 2, 5, II, 14) to a vertical depth of 1000 feet, are approximately 1,120.000 tons averaging 0.32 oz. Au/ton.

Jan 1, 1986

By Narasimha Mangadoddy, Balraju Vadlakonda

"Bubble size distribution, bubble rise velocity and gas and solids hold-up are the key major hydrodynamic parameters that are extensively used for column flotation design and performance evaluation. The distribution characteristics of mean gas hold-up is studied using electrical resistance tomography (ERT) coupled with pressure transducers (PT) in column flotation. The ERT technique facilitates non-invasive and nonintrusive visualization of different flow regimes even in the presence of particles in a column flotation. The effect of superficial gas velocity, feed flow rate and slurry height in the column on mean gas hold-up and its radial distribution has been analysed for both two-phase and three phase flows. Experimental results show ERT coupled with PT is suitable as an online monitoring tool to provide useful information on the three-phase flow hydrodynamic parameters of the column flotation. The tomography images, which were generated using a modified sensitivity back projection algorithm, are employed to explore the influence of parameters in two phase flow in column flotation. Mean gas and solids hold-up values extracted from ERT have been critically analysed for the column operating in various flow regimes. Gas hold-ups and solid hold-ups results using ERT are in very good agreement with conventional estimation and correlations obtained using pressure transmitter methods. Meanwhile, the results show that the gas hold-ups in the centre region increase constantly with an increase in the superficial gas velocity, whereas solid hold-ups distribution is very heterogeneous for high gas velocity. Furthermore, the results also indicate that ERT is a very powerful tool for diagnosing the 'inside' flow behaviour of gas –liquid–solid three phase flow in columns operating for a wide range of flow regimes.INTRODUCTIONColumn flotation is perhaps the most significant technological innovation in flotation machinery and its successful introduction in mineral processing plants. There has been a lot of attention in understanding the various mechanisms that take place during operation. Due to many reasons column flotation has been found to yield better performance than conventional flotation cells, particularly with fine particles (Honaker & Mohanty, 1996). Due to complex flow behavior in nature, the performance of column flotation influenced by on flow characteristics of the process, (Jena, Biswal, Das, & Reddy, 2008). Previously basic research is carried out to evaluate the effect of the hydrodynamic parameters on performance of column flotation (Finch, J.A.;Dobby, 1991). Many techniques have been developed that could be used to experimentally analyse the hydrodynamics of column flotation. Tomography techniques are well sound to investigate the hydrodynamics for process equipment. Among that, Electrical resistance tomography (ERT) has been used in various industrial investigations for visualization of the concentration profiles and characteristics of the fluid dynamics in gas–liquid two-phase systems (Wang, Dickin, & Mann, 1999; Williams, R.A; Wang, 2000). ERT is an imaging technique to analyse the internal flow behavior non-intrusively. ERT provide very useful tools for measuring and monitoring of column flotation process on line. Due to its high speed capability, low cost measurement, robust sensors, ERT is considered to be the most powerful tool among other tomography techniques such as positron emission tomography (PET), magnetic resonance imaging (MRI), optical and infrared tomography. Application of ERT has extended in process systems due to its improved speed of data acquisition, sensitivity, flexibility and noise immunity. In multiphase flow of bubble columns, gas hold-up and solid hold-up are explored by using the coupling of ERT and difference pressure method (Jin, Han, Yang, & He, 2010)."

Jan 1, 2016

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 R. Charlier, G. Radioti, J. -P. Radu, S. Delvoie, F. Nguyen

"In order to investigate the fracturing of the bedrock and its possible heterogeneous distribution in situ, four boreholes equipped with double-U geothermal pipes of 100 m long were installed on the campus of the University of Liege (Liege, Belgium) over a surface area of 32 m². The bedrock, which starts at a depth approximately of 8 m, is quite fractured and consists mainly of siltstone and shale interbedded with sandstone.Different geophysical methods are applied at two different phases, after drilling the boreholes and after injecting the grouting material. The first approach consists in lowering an ultrasonic borehole imager (borehole televiewer; Zemanek, Glenn, Norton, & Caldwell, 1970), an instrument that acts as an ultrasonic transducer and receiver, into the boreholes to obtain high-resolution, continuous images with 360° coverage of the local geology and fracturing. Moreover gamma-ray logs of the four boreholes are obtained and inclinometry is conducted.After drilling the boreholes fiber optic cables are attached along the pipe loops and the double-U pipes are installed inside the boreholes. Then the grouting material is injected. The second approach consists in measuring the temperature along the fibers by applying the Distributed Temperature Sensing technique (Soto, Sahu, Faralli, Bolognini, Di Pasquale, Nebendahl, & Rueck, 2007). A laser pulse is injected into the optical fiber and the temperature along the fiber is determined by the intensity of Raman stokes and anti-stokes reemitted signals. Temperature evolution is measured during hardening of the grouting material. Local maxima of the temperature curve are probably due to a local lower thermal conductivity and/or a local larger quantity of grouting material due to gathering of fractures.A detailed fracture characterisation (position, opening, orientation, dip angle) is obtained based on the acoustic signal travel time and amplitude. The fractures are characterised by the same dipping and orientation but significantly vary in number and location in the four boreholes, despite the close distance between them. Gamma-ray data and observation of the cuttings during drilling result in rock identification through depth as well as in determination of the layer dipping. The inclination of the four boreholes tends to be perpendicular to the dipping. The combination of the two geophysical methods as presented provides information useful for the hydro-thermo-mechanical behaviour of the bedrock. The contribution of the thermal behaviour of borehole heat exchangers to bedrock investigation will be further studied by conducting Distributed Thermal Response tests (Fujii, Okubo, & Itoi, 2006). During the tests we will measure the temperature variation thanks to the installed fiber optics. These data will allow us to correlate any anisotropic thermal behaviour to the geological characteristics. The available information could be used for a detailed numerical model."

Jan 1, 2015

By F. J. Guevara

A two-dimensional mathematical model for fluid flow and heat transfer in a sixin- line electric smelting furnace was developed to study the effects of temperature on slag viscosity in both the liquid and mushy zones. The model focused on the fluid dynamics of the molten slag and the effects on the formation of a slag freeze layer on the hot face of the furnace wall. Previous experimental and mathematical work, carried out under Ra number of 109 and using a fluid with Pr number of 65, showed that it is possible to mathematically describe the freeze layer formation over a vertical wall using a fixed-grid model. The chemical composition of the slag was taken into account through its effect on the viscous activation energy as well the solidus and liquidus temperatures. The results show that the flow pattern is strongly modified in areas of high viscosity, in front of the cooling system and at the slag-matte and slag-calcine interfaces. The results are discussed in terms of heat flux over the refractories and their effects on cooling system design.

Jan 1, 2007

By P. Blonde

Recent analysis has suggested that a balanced recovery profile can improve flotation bank performance. Test work was conducted to test the balanced profile concept at the Penhorwood talc mine near Timmins, Ontario, Canada. Plant trials were devised to determine how to control the recovery profile and the resultant impact on grade and recovery in a rougher bank of four cells. Accompanying gas dispersion measurements revealed a maintenance issue with one cell that was corrected. By manipulating air and frother addition it was possible to bring the bank closer to a balanced recovery profile and the down-the-bank grade/recovery improved. Plant production showed an increased talc grade at similar yield with the balanced profile. The results provide justification for a long term plant trial.

Aug 1, 2013

By Dallas W. Davis

Twin - Kennecott Deal Announced April 15, 2004 ! Kennecott earns 56% interest, if in 4 years, spends C$10 million and recovers at least 200 cts of +1 mm diamonds in all dimensions from any contiguous body ! Earn-in can take up to 6 years, but incurs stepped reduction of interest from 56% to 46% or 0% if $C10 and 200 carats not achieved ! By funding all costs through feasibility study, Kennecott earns 71% in 7 years, or, stepped reduction to 62% if completed after 8 years ! By achieving production within 10 years and funding Twin?s share of development and construction costs, Kennecott earns further 4% ! If no election to develop a mine within 2 years of feasibility study completion, Twin may present development proposal which Kennecott has 60 days to elect to follow or transfer management to Twin and dilute to 49% ! Each party has one time right to elect to market its diamond share ! On signing and annually, Kennecott will purchase $C250,000 of Twin shares at 130% of then prevailing market price until achieved earn-in

May 1, 2004

By K. Sakai, M. Miyaue, T. Aoki, T. Tani, S. Tanaka, N. Kudo

In the planning stage of a tunnel, due to limited available technology in the geological survey and the financial restriction, tunnel supports are often designed from unsatisfactory information, and the tunnel construction is started. Therefore, "observational construction" is carried out in the construction stage, in which the design is rationally verified and modified by observations/measurements. Moreover, the ground conditions ahead of a tunnel face must be predicted for efficient and safe tunnel construction. The authors have examined effective prediction methods to the ground conditions ahead of a tunnel face under construction of a mountain tunnel (Aoki et al., 2010) in view of the established method (Schubert et al., 1995). Though the prediction method of Schubert et al. requires the displacement in the direction of tunnel axis, it is difficult to obtain its accurate data by the electro-optical distance meter. Then, we have proposed a method that uses tilt sensors installed at the tunnel crown near the face to obtain the slight tilting information. To measure inclination of the tunnel crown, this inclinometer was originally developed as a daily management measurement, such that the geological condition and its possible change behind the face could be detected early, and a steady advance and construction safety could be ensured. This paper describes the method of forward prediction mechanism and advantages of this proposed method. It then presents the typical results of a field demonstration test at a tunnel under construction. Lastly, the predictable range from the stratum boundary at which ground stiffness changes are discussed based on the results of three-dimensional numerical analysis.

Jan 1, 2015

By Michael Boyle, John Zeni

"The Blind shaft boring method is a mechanised process of excavating large diameter vertical shafts downward from the surface. It is a rotary drilling technique eliminating any requirement for personnel to enter the shaft or access underground workings during drilling and lining phases. Excavated material is delivered to surface carried by a flow of circulating fluid through the centre of drill rods. The drill assembly is suspended from a large A-frame rig and powerful winch at ground level providing vertical thrust to a hard rock cutter head. INTRODUCTION The Southern Coalfields Ventilation Shaft was constructed at a mine, 45 km north-west of Wollongong. The 5 m finished diameter (6.2 m drilled) shaft reaches a final drilled depth of 517 m, the deepest, fully lined blind bored vent shaft to date in Australia. Operated by a mining company in the Southern Coalfields, the expanding mine required a new ventilation shaft and associated surface infrastructure to service future operations. An assessment of future ventilation requirements for the coal seam operations identified a need to improve the capacity and reliability of the existing underground ventilation system in order to ensure a safe and efficient underground working environment. Installation of the new upcast ventilation shaft was determined to be the most cost effective and reliable solution to provide adequate ventilation for underground operations. The completed shaft is smooth and fully lined with steel/concrete composite liners that are hydrostatically sealed. The shaft lining is designed to meet the mine ventilation requirements for a service life of 20 years. The shaft intersects the top of the working section of the coal seam at approximately 513 m of depth. This includes the shaft collar depth and shaft bottom profiled intake section.PROJECT METHODOLOGY AND INDUSTRY BEST PRACTICE The shaft was drilled using the blind bore method, an innovative construction technique and an alternative to the traditional methods of sinking deep and large diameter shafts, such as raise boring and conventional drill and blast shaft sinking. The blind bore method allows the shaft to be drilled from the surface down without anyone having to enter the shaft or the mine during the construction process. This is by far the safest method of shaft construction and is especially suitable for difficult ground conditions where there may be unstable or water-charged strata. As this method involves drilling from the surface downward, shafts can be completed ahead of the underground mine development. Thus, allowing underground operations to focus on development and production without the conflicts of managing ventilation priority for underground contractors and mucking out spoil from excavation workings."

Jan 1, 2019

By Cummings. J. B., R. Haworth

"THE OPERATION of the Potash Company of America, Ltd., at its plant near Saskatoon, Saskatchewan, is the result of many years of exploratory and development work, culminating in the construction of a shaft, milling, concentrating and other facilities necessary to the production of potash in a marketable form.The possibility that potash existed in •commercial quantities in Saskatchewan was first indicated in 1943, although it was not until mid-1946, when Bata Petroleums penetrated a potash bed at its Verbata No. 2 well near Unity that substantial in-ter.est was developed in the possible exploitation of this important mineral product.The Potash Company of America, which is the largest producer of pot-ash in the Carlsbad, New Mexico area, a district that has been sup-plying about 90 per cent of the North American potash demand, be-came interested in the Saskatchewan deposits •at an early stage. Its engineers made an intensive study of the western Saskatchewan area in 1947 and continued their review of operating problems throughout the next three years.""Potash"" is the commonly used general term applied to the minerals of potassium, of which there are several. The most common mineral forms in which it is produced are potassium chloride and potassium sulphate. The potash content of potassium compounds is ordinarily ex-pressed in terms of potassium oxide (K20) equivalent."

Jan 1, 1960

By R. H. Wallis

Weighted moving-average contour maps have been constructed for molybdenum, copper and zinc using 7850 stream-sediment samples from 5430 square miles (14,063 sq. kms) of south-central British Columbia. Regional trends for molybdenum and zinc are northeast, north and northwest and those for copper are north and northwest. These trends are interrupted by zones markedly low in metals . The metal-rich trends cross rocks of different lithology and age and thus appear to be structurally controlled. The northeast trend may have exerted control on metal distribution at two different times.

Jan 1, 1978

By R. Le Houillier, M. Nagamori, A. J. Plumpton

"Asbestos tailings are a typical serpentine, hydrated magnesium silicate, consisting primarily of antigorite and a few per cent of unrecovered fibrous chrysotile. Serpentine has unique thermal properties in that dehydroxylating calcination at 600 to 700°C can yield an amorphous structure in which most of the magnesia is liberated from the original bond with silica and thereby rendered chemically active. The amount of activated magnesia can be quantified by selective leaching with a weak acid such as acetic acid. Many wet processes have been proposed to extract magnesium values from calcined or natural serpentine by means of various acids and their ammonium salts. However, the only commercial utilization of serpentine today is found in dry processes such as the production of fused magnesium phosphate fertilizer .The present paper reviews the physical chemistry of the dehydroxylation of serpentine and also various wet and dry processes in order to provide a general view regarding the chemical transformation of asbestos tailings.IntroductionAsbestos fibers occur as chrysotile, a serpentine polymorph. More than nine tenths of mined asbestos ores consist of massive non-fibrous serpentine, primarily the polymorph antigorite, which is discarded as tailings after fiber extraction. For many decades, Quebec has been a world leader in the production of asbestos fibers. As a result, colossal tonnages of serpentine have accumulated in the Eastern Townships'!'. Serpentine minerals are found in large deposit s throughout the world, and significant research efforts have been made, particularly in Japan and the USSR, mostly in attempts to extract magnesia or silica values therefrom.The chemical composition of serpentine (chrysotile and antigorite) may be ideally expressed as Mg3Si2Os(OH). which corresponds to 43.7% MgO and 43.3% SiO2. Natural serpentines often contain a few per cent of Ni-bearing magnetite and other impurities, and therefore the contents of MgO and Si02are both about 40% or lower.Serpentine (hydrated magnesium silicate) is virtually insoluble in weak acids. However, when dehydroxylated under controlled conditions, ' it decomposes to an amorphous state in which magnesia and silica are isolated and chemically active. The magnesia so activated is readily soluble in weak acids. This unique characteristic of calcined serpentine, first discovered in 1942,, has since attracted the attention of innumerable researchers, whence many processes have been proposed."

Jan 1, 1980

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. R. Naji Meidani, A. Cameron, A. Richardson, M. Isac, R. I. L. Guthrie

The supersonic core of shrouded jets remain coherent over longer distances vs conventional supersonic jets. This phenomenon should allow for greater penetration of oxygen into slag/steel reactor systems. As such, they hold the promise for faster slag/metal mixing in BOF type metallurgical reactor systems, possibly creating greater surface area/volume ratios of reacting phases, and thereby faster kinetics, as compared to conventional supersonic jet systems. In order to assess the potential of shrouded supersonic jets versus their conventional counterparts, an experimental investigation of impinging shrouded supersonic jets into a water model of a simplified BOF system was carried out in the MMPC's water modelling laboratory. The experimental results for three different designs of a shrouded supersonic jet nozzle have been compared in terms of greater penetration depths and reduced mixing times. Based on a novel dimensional analysis, the depth of penetration of a gas jet into a liquid bath is shown to depend on the nozzle-bath distance, the liquid's Froude, Reynolds and Weber numbers, reflecting the ratios of gravity, viscous and surface tension forces to the jet's inertial, or momentum, forces. Good agreement between the mathematical model and experiment was obtained in terms of predicted and observed depths of penetration. Further efforts have been made to study jet penetration into liquid metals. The effects of mean liquid density of slag/metal mixtures and a wide range of gas flow rates on the penetration depth were investigated theoretically. The results show that the penetration depth can be increased with increasing gas flow rate and decreased bath density.

Jan 1, 2004

By C. Harold Riches

This article is directed co a commentary on the patent system in its relation to the public interest. As man gained supremacy over his environment, he could devote progressively increasing portions o his time to improving his standards of living. In the history of the human race, we have advanced from the hollowed floating log to the modern steamship of the present age; from the sickle and flail to the reaper and combine; from the trumpet and drum as a means of communication co the telegraph, telephone, and radio; from the horse and ox cart to the automobile, truck, aeroplane, and train; and so on ad infinitum through the list of inventions on which are based the industrial and political economies and standards of living we enjoy today. It has also been a long road from the day of the alchemist and his closely guarded secrets to the era of the patent system and its storehouses of knowledge open to the world. The alchemist and the craft and merchant guilds closely guarded their secrets. In fact, they largely opposed innovations on the grounds that they might injure profits and restrict employment. In these days of unrest, with great clamour out of doors for radical changes in our political and industrial economies, it may not be untimely to examine one of the keystones which support the economic structure we know as the free enterprise system, the system which is predicated upon the right of the individual to own property. Many, through impractical idealism, ignorance, confused thinking, or blind political prejudice, advocate the substitution of ownership by the State ? for the right of ownership by the individual. As civilization has advanced to the high standards of living we enjoy today through the efforts of a comparatively few inventors, the patent system which has provided the incentive that created the inventions on which our industries and our employment are based is fully understood and appreciated by a comparatively small percentage of our people. As a result, the patent system, as a keystone in our free enterprise economy, is an apt target for destructive criticism, with the thought, possibly, that by eliminating or drastically restricting the several rights to individual ownership one by one, ownership by the State will progressively replace ownership by the individual.

Jan 1, 1949