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By N. Aslin, R. Clark, G. Heferen

The methods of harvesting copper from stainless steel mother plates has been investigated from fundamental and operational experience perspectives. At least five different harvesting techniques have been identified that have different effects on product quality, current efficiency, current distribution, growth morphology and ease of stripping. Each method is examined from fundamental principles to understand what occurs during the harvesting process and why the particular effects are manifested. Experience from plants operating the harvesting method is provided to show that the fundamental understanding is relevant. Best practice harvesting method and harvesting management are described.

Jan 1, 2014

By William Winsor, Harold L. Snyder

"AbstractShould oil and gas be proven in commercial quantities on the Labrador Shelf, current technology is not adequate for production operations in this severe environment, which includes yearly invasion of pack ice and icebergs. The fishery of this section of the North Atlantic is a vital resource to which a major oil spill or blow-out would impose an intolerable burden, This means that production systems must be designed and built to be fail-safe.The experiences of mining in Bell Island and Cape Breton have shown that it is possible to operate beneath the ocean floor, and this technology may hold the key for safe, reliable and economic production, This paper attempts to define particular problems and outline possible solutions.IntroductionOUR DISCUSSION is subject to the assumption that large hydrocarbon reservoirs will be discovered in the sedimentary basin of the Labrador continental margin. The petroleum industry has not attempted to operate in a harsher area. The Labrador coastline is exposed to North Atlantic storms and icebergs year’round, Arctic pack ice occurs up to six months of each year. However, there is no doubt that, if sufficient hydrocarbon potential is outlined, development will proceed."

Jan 1, 1977

By G. H. Agnew

When water floods are initiated after gas-oil ratios have increased, the transition period from the start of injection until" the gas-oil ratios are returned to the solution gas-oil ratio may be important for either economic or technical reasons. The transition period is longest, and consequently most critical in water floods where injection is equal to withdrawals. This paper describes a theoretical basis for predicting the behavior of such a system and outlines a procedure for making the necessary calculations. The calculation procedure is illustrated for two actual cases: a line drive water flood and a five spot water flood. In each case there is a reasonable similarity between the actual and calculated performance.

Jan 1, 1960

By C. A. Hardie, G. F. Leichtle, J. A. Finch, J. A. Watson

"The recycling of wastepaper has become an important and common process worldwide. Techniques similar to those used in the mineral processing industry are used to produce high quality recycled fibres for use in newsprint. The mineral processing group at McGill University, in conjunction with the Pulp and Paper industry (Mechanical and Chemi-mechanical Wood Pulp Network), has adapted one of these techniques, column flotation, for the purpose of deinking wastepaper. This article describes the typical process of recycling wastepaper from a mineral processing point of view. It also presents results from McGill University’s flotation column test work at a Québec wastepaper recycling facility. IntroductionThe recycling of wastepaper has become an important and common process worldwide, including Canada which is now the world’s largest importer of wastepaper (CPPA, 1996). Much of the current drive to increase the utilization rate of recovered paper is a reaction to the solid-waste disposal problem that faces many Canadian and United States municipalities. The real problem in the disposal of solid waste is not the absolute amount of garbage that must be disposed of each year, but this amount in relation to available disposal capacity.Environmental restrictions on the creation of new landfill sites and incinerators (the two main options for disposal of municipal solid waste) have tightened the demand/supply balance in the solid waste disposal market. This shrinking availability of waste disposal sites in the face of increasing population with greater disposal requirements defines the Developed World’s solid waste crisis. Not only are there fewer disposal sites available, but the costs of using them is skyrocketing. These factors have increased government regulations mandating recycled paper content in newsprint. Conservation and environmental issues make the current drive for wastepaper recycling a real issue and business opportunity."

Jan 1, 1999

By Y. O. Fortier

"ForewordTHE Arctic Archipelago and northern Greenland contain an orogenic region that is as much as 300 miles wide and over 1,400 miles long. It occupies much of what was formerly classified with the Arctic Plains and grouped with other plains and lowlands of Canada as one main geological division. It is proposed that this folded region be designated the Innuitian Region and be recognized as one of the main geological divisions of Canada.Canada's main geological divisions (see Geological Survey of Canada, 1947) have been considered as consisting of a central shield, largely surrounded by plains that separate it from eastern and western mountains. The plains include the Interior Plains, the St. Lawrence Lowlands, the Arctic Plains or Low-lands, and the Hudson Bay Lowland, which is in the central part of the Shield. Plains and mountains are, strictly speaking, physiographic terms, but because mountains are generally folded regions and plains are generally made of undisturbed strata, such terms are useful vehicles to express the fundamental make-up of the land. Nevertheless, it is preferable to use the terms Appalachian and Cordilleran 'Regions' rather than 'Mountains', as those geological divisions are not exclusively made of mountains.Because of the lack of more definite information, the 'Arctic Plains' have included, in the past, regions with plateaux two to four thousand feet above the nearby sea, mountain ranges reaching approximately 10,000 feet above sea level, and regions of folded strata."

Jan 1, 1955

By John L. Rich

A New Field for the Mining Industry A new field for the mining industry is in prospect. This is the recovery of the petroleum which has been left in the ground in the older oil fields whose yield has declined until they are no longer profitable to operate in the ordinary way. The fact that an oil field has reached the economic limit for operation by pumping does not necessarily 'mean that the oil has ? been exhausted. In many such cases not over one-fifth, or even one-tenth, of the total oil content of the field may have been taken out when this stage has been reached. This means that there exists a large reserve of oil which can be recovered by whatever process best takes advantage of the natural conditions under which the oil occurs. Mine drainage is one of the processes by which this oil may be recovered. Its relative importance will depend partly on the ingenuity and wide-awakeness of mining engineers, and on mining capital. The opportunity is undoubtedly at hand. In order that we may be in a position to judge the possible advantages of mining methods for the recovery of this oil, I have reviewed, on the following pages, the methods now in use, and have discussed the physical conditions of the reservoir rocks in which the oil is found, and the suitability of the various recovery processes, in use or proposed, in the light of these reservoir conditions.

Jan 1, 1927

By Charles G. Kemsley

IN view of the truly remarkable development of special steels for special purposes, the mining industry has for years looked forward to a time when steel makers would come forward with a product which would be an improvement over the straight carbon steel which has always held the field for drilling rock. In order to avoid making changes in conventional shop practice, the industry has perhaps been too insistent upon obtaining a water hardening steel which could be handled in the blacksmith shop by long established methods. As early as 1932 or 1933, an oil-hardening tool-steel of the one per cent carbon, plus chrome, plus molybdenum type was applied to hollow drill steel. It was known as a hard as well as a tough steel, and one that, theoretically, should give a good account of itself as a rock drill, if properly heat-treated; and so it has proved in actual trials. There were numerous deterrents which retarded adoption of this steel. For several years there has been a constant improvement in the drilling qualities of the straight carbon steel, and, considering the higher unit price ? of the alloy, there has been considerable doubt in the minds of some mining? men as to what advantage there might be in the use of alloy over straight carbon for hollow drill steel. The alloy being an oil-hardening steel, its adoption meant having two kinds of steel in the mine, for a time, and that spelled trouble, unless some positive means of identification was adopted. The hardening and forging ranges of alloy steel being narrow also made necessary much closer control over these operations if poor results were to be avoided. These thoughts undoubtedly prevented its use becoming wide-spread, for, as a matter of actual record, less than fifteen per cent of all the hollow drill steel used in Canada today is alloy.

Jan 1, 1942

By Jas. E. Thomson

"The Omega mine is in McVittie township in the Larder Lake area, Ontario. Production at the mine commenced in 1936, and, until the end of 1946, ore milled amounted to 1,558,604 tons, from which 207,074 oz. gold and 28,205 oz. silver, valued at $7,585,470, were recovered. The mine workings extend to a depth of 1,975 feet.GEOLOGYThe geology of the mine has been described in detail by C. P. Jenney (l) and the writer (2). The general geology and structure in the vicinity of the mine is discussed on an earlier page in this volume. The rock formations found in the mine workings are indicated on the accompanying plan and section (Figs. 1and2). They consist of an intermingled, south dipping complex of volcanics, sediments, and secondary talc-chlorite schists and carbonates. The carbonatized rocks, which are often referred to as 'dolomite' in the Larder Lake camp, are siliceous-carbonate replacements in the talc-chlorite schist zones. In places they contain green mica, probably fuchsite, and are cut by a stockwork of quartz veinlets and stringers. A stock of syenitic intrusives lies south of the mine workings.STRUCTUREThe main structural features are indicated in Figs. 1 and 2. The formations and orebodies have a pronounced southerly dip, which flattens with depth. The talc-chlorite schist and 'dolomite' zones are part of the Larder Lake fault or 'break' on which there appears to be very large displacement. Evidence throughout the district would indicate that the south side moved up and, in the case of the Omega mine, the thrust may have been distributed throughout the several intensely sheared zones. This slice faulting could account for the repetition of sediments and volcanics. An alternative possibility would be original interbedding of volcanics and sediments."

Jan 1, 1954

By George B. Saunders

The mines in western Canada producing steam coal will find a better opportunity this year to market their product in Winnipeg - for two reasons: First, the new wage schedules, signed with local unions at each mine, have enabled them to reduce the selling price materially. Second, the duty on slack coal coming in from the United States has been raised to 50 cents, which is equal to the duty on run-of-mine coal. This has had the effect of raising the cost of mine-run to .the importer. Formerly, it was the practice to bring in slack coal under a duty of 14 cents and lump coal under a 53-cent duty and, by judicious mixing of the two, manufacture a mine-run coal at an average duty cost of about 22 cents. Fortunately, through efforts of the Alberta Government, and other friends of the Canadian coal trade, the Federal Government was persuaded to adjust the duty on slack coal as indicated. While it will be found that the Manitoba market, this season, is slightly more easy of access we have still a long way to go before we reach the desired goal. Geographically and economically the Manitoba market should belong to western Canada. However, it has been found a very profitable market for United States mines because large tonnages of coal can be shipped, practically at the convenience of the mines, via the Great Lakes, during seasons of slack business. They will therefore not relinquish this market without a struggle.

Jan 1, 1925

By M. H. Allan

SASKATCHEWAN POWER CORPORATION is a Provincial Crown Corporation responsible for the production transmission and distribution of electric power and natural gas in the Province of Saskatchewan. Through the electric power responsibility, we became interested in the coal reserves in Saskatchewan, which, although still somewhat of an "orphan fuel" in the early and mid 1950's, gave the promise of providing a low-cost source of energy for electric generation. Coal in Saskatchewan, a lignite with an "as-received" heating value of from 5000 to 6500 Btu's per lb and up to 40% moisture, was first recorded in 1853 . By the end of the 19th century, many small mines were in operation in the Estevan, Coronach and Shaunavon areas supplying local inhabitants with a cheap source of heat. These small mines, some of them prosperous, some of them not, continued operation right up to the late 1940's, when oil replaced coal in the market place. The year 1930, however, saw the introduction of the new technique of strip mining in the Estevan area. This technique revolutionized coal mining. It was now possible to use large machinery to uncover the coal and cast the overburden to one side instead of burrowing through thin seams of coal varying from 2 to 10 feet thick. The overburden cast aside by these large mechanical shovels, or later draglines, created heaps of spoil which at that time, during the depression, were a sure sign of prosperity and the welcome news that people had jobs. By the late 1940's, coal production had dropped off, but the spoil piles remained and were now labelled by some as "scars on the landscape", even though there had been some natural succession of grasses. In addition, some people had planted trees in experimental plots and even some aerial seeding had been done.

Jan 1, 1978

By F G. Cooke

"This paper describes a medium-sized copper mine's results in making innovations and changing operational practices to combat increasing expenditures due to higher labour and supply costs, extended workings, scarcity of experienced manpower and problems created by deteriorating ground conditions.OPEMISKA COPPER MINES (QUEBEC) LIMITED is located at Chapais in the Chibougamau area, in central eastern Quebec, approximately 300 miles north of Montreal and 150 miles north west of Lake St. John. The latter area, developed by lumbering and farming, has supplied the majority of the employees, who, with training and experience and a desire to work and improve themselves, have become the backbone of the Company's 600 personnel.Opemiska began production in 1954 at a rate of 400 tons per day, using diesel power and road transportation. The rate was progressively increased and, by 1959, with hydro-electric power and rail transportation, the mine had reached its present production rate of 2,000 tons per day. It has produced concentrates containing over 430 million lbs of copper."

Jan 1, 1968

By W. B. Boggs

This is a rather comprehensive subject and cannot be thoroughly covered in the short rime allowed for its presentation. This article will touch only upon a few of the chief points of the difficulties encountered in recovering copper from brass shell cases in a primary smelter which was not designed to treat scrap metals. Owing to the fact that the plant is at present (Dec., 1946) closed, and our tests were not completed, full details of the results are not available. As is well known, most primary smelters are situated near the mines in the interior of various countries and are not close to seaports or large industrial and railway centres. Consequently, iris unusual for a primary smelter to be asked to treat scrap metal of any kind. When so required, iris obvious that the primary smelter is at a great disadvantage, for the simple reason that it probably has to pay the freight on the scrap from the seaport or industrial centre to the smelter and then also pay the freight on the recoverable metal from the smelter to the refinery, or seaport or industrial centre. Another disadvantage is that a primary smelter is not equipped to sample and unload the scrap nor bas it usually the equipment adaptable for treating the scrap efficiently, as the plant bas been designed to handle large tonnages of ores and concentrates. This short paper will describe some of our difficulties> and how they were corrected. However, it might be advisable to state briefly some of the methods used in treating brass shell cases in other plants. In the first place, a brass plant producing new brass- especially those producing brass billets for extrusion to make brass tubes or rods, or to be drawn into wire, or making brass cake to roll into brass sheets- generally insists upon using new electrolytic copper and zinc and is opposed to using any scrap or secondary brass . Consequently, such a plant usually will not treat brass shell cases. Therefore, the usual procedure is to ship brass shell cases to a secondary smelter, where it is generally sorted, melted, fire-refined, and returned to the market in the form of a high or low brass ingot which can be sold to brass foundries for making brass castings. This evidently is the cheapest and simplest method. Another method is to ship to a smelter which is a combination of a primary and secondary smelter attached to or near an electrolytic refinery. In plants of both these types, that is a primary smelter with Cottrell dust collectors or a combined primary and secondary smelter with Cottrells or a bag house, the zinc may be wasted. However, if a bag house is used, some of the zinc is recovered, but it is usually contaminated with other metals and further processing is required to recover it.

Jan 1, 1947

By Roderick C. McDonald

Great Bear lake, the fourth largest body of water on this continent, comprises an area of approximately 12,000 square miles, and is set astride the Arctic circle, with a large portion of it witnessing both the Arctic winter night, and the Arctic summer day with its midnight sun. The very name itself, Great Bear, suggests an Arctic region. The seasonal contrasts at Great Bear lake are very marked by the cold and darkness of winter, and the warmth and brightness of summer. Signs of winter such as low clouds, snow, sleet, fog, and night frosts, generally appear the latter part of August, while ice forming on bays during the last two weeks in September ends boat travel on the lake about September 30th.Early in June the ice leaves the river mouths, during the last ten days of the month it disappears from small bays, and at some time during the last two weeks of July the main body of the lake becomes navigable. In 1916, the ice disappeared earlier than usual, and the lake was navigable on July 5th. Great Bear river generally breaks up about June 1st, but, on account of ice cliffs and floes, it is not navigable with safety until early in July. Even then, the traveller is confronted with the Charles rapids, but these might be overcome by a wagon or motor road, such as the one from Fitzgerald to Fort Smith: However, in 1931, Mr. A. W. Boland, Fort Norman, N.W.T., carried with scow and motorboat practically all freight between Fort Norman and LaBine point and Hunter bay, at the east end of the lake. During July and August, two types of clothing are required, for, although the days are mainly ones of warm sunshine, the nights are cloudy and cold. In the winter season, fur clothing is used exclusively. Considerable timber, mainly white spruce, suitable for fuel and building purposes, borders the lake and extends eastward to the Coppermine river. North of the lake, no timber is found except in the river valleys, but with oil and coal possibilities near Fort Norman, the fuel situation might be solved.

Jan 1, 1932

By C. D. Kaeding

IN the summer of 1937, the Algoma Steel Corporation, Limited, decided to embark on the full-scale development o their Helen mine and the erection of plants to produce commercial iron sinter from its ores at a rate ? of fifteen hundred tons per day. The Helen deposit has long been known as one of the largest bodies of non-commercial iron ore in Canada, consisting almost entirely of siderite with a band of pyrite along the north wall and some lenticular inclusions of pyrite throughout the mass. It originally contained a nominal amount of hematite (2,800,000 tons), localized at the western end of the ore-body, but this was mined out during the years 1900 to 1918. For details of the:-geology of the Helen range and of the surrounding district, the reader is referred to Memoir 147, Michipicoten Iron Ranges, Geological Survey of Canada, 1926 (1). The siderite mass was explored by diamond drilling in 1917 and the portion so drilled was estimated to contain 67 million tons of siderite averaging 36.0 per cent Fe, 3.2 per cent S, and 8.2 per cent SiO,, without establishing its ultimate depth or extent. The variation in the sulphur content shown by drilling was from 1.5 per cent in 72 per cent of the tonnage, to 7.2 percent in the remaining 28 percent. The pyritic ore aver-aged about 38 percent iron, but otherwise its composition was substantially the same as that of the siderite mass.

Jan 1, 1940

By T. G. Phillips

"This paper gives an inside look at a bulk terminal and describes the preparations that must be made by a company in developing such a terminal and its position in today's traffic pattern. The following headings cover the subject material: (a) Traffic pressures, their detection and measurement, (b) position in the traffic flow -selection of site, (c) transportation connections -present and possible future routes, (d) engineering studies and costs, (e) contracts, the basic material for insured traffic, (f) financing, (g) budgetary control, (h) development of new techniques, (i) growth into new cargoes or cargo-handling methods and (j) consolidation."

Jan 1, 1968

By Muhammad Usman Siddiqui

Managing and analysing the vast amounts of data collected in a mining project effectively is crucial for enhancing the project's economic feasibility. The efficient utilization of this data is critical to minimising the time spent on projects and increasing project value. Process engineers can effectively integrate geometallurgical data into plant operations by employing analytical tools like Python, significantly optimizing the mine-to-mill process. This practical approach is a game-changer in the mining industry. Classifying a geomet dataset into units of similar characteristics (properties of the ore) is an important outcome of a geomet study. This approach simplifies data classification, allowing for class-by-class process modelling, which improves the decision-making process in mine planning and development. Classifying a geomet dataset involves using grade, lithology, and test work data (if available) to create blocks of similar characteristics, known as ‘geomet units.’ Compared to conventional methodologies, these units provide context and empirical evidence that can be more accurately mapped onto block-by-block process flowsheet development and net present value (NPV) estimation. This robust classification method reduces a project's technical risks and influences the initial mine planning sequence to maximise profitability. Defining robust geomet units with data sets with similar material is challenging due to the vast amounts of data available and the database's high heterogeneity. The methodology's purpose is to minimise time-consuming low-value-adding aspects of geometallurgy. The approach is different for a greenfield and a brownfield study, as all the valuable data in a brownfield process can be utilised to define the geomet units. Python has various libraries providing multiple machine-learning algorithms to assist in classification. The k-means algorithm is used for clustering, and the SHapley Additive exPlanations (SHAP) method is used to quantify the effect of each feature on the clustering results. However, even with automation, the methodology still requires a keen eye to account for the nuances that appear from project to project.

Oct 1, 2024

By J. M. Newell, G. R. Peatfield

"The Red-Chris porphyry Cu-Au deposit is located between Ealue and Kluea lakes, southeast of the village of Iskut on the Stewart Cassiar highway in northwestern British Columbia. It was explored by Texasgulf Inc., in a joint venture with Great Plains Development Company of Canada, Ltd. and Silver Standard Mines Ltd., during the period 1973 to 1980. Exploration resumed in 1994, following acquisition of the interests originally held by Texasgulf and Great Plains Development by American Bullion Minerals Ltd.Prospectors were first drawn to the area by prominent limonitic stain zones exposed in creek gullies in the western part of the property. These zones are developed on the alteration halo at the western periphery of the deposit. The potential ore zones do not crop out and were first exposed in a bulldozer trench excavated in 1971. Subsequent exploration was by percussion and diamond drilling, guided to some extent by induced polarization surveys. In 1976, estimated resources contained within two crudely designed open pits were 41 million tonnes with an average grade of 0.56% Cu and 0.34 g/t Au, with a cutoff grade of0.25% Cu. New resource estimates based on a major drilling program completed by American Bullion in 1994 were released as this paper goes to press. These estimates were calculated using various copper cutoff grades; at the 0.4% Cu cutoff, the ""in-situ geological reserve"" is given as 100 million tonnes grading 0.58% Cu and 0.46 g! t Au (American Bullion Minerals Ltd., 1995).The deposit consists mainly of pyrite, chalcopyrite and increasing bornite at depth, in zones of quartz-vein stockwork hosted by an elongate body of altered monzonite porphyry of latest Triassic or earliest Jurassic age. The stock intruded volcanic and sedimentary rocks of probable Stuhini Group affinity and is in faulted contact with sedimentary rocks of the Jurassic Bowser Lake Group. Gypsum stockworks are developed in the higher levels of the subvolcanic porphyry system. Late-stage quartz-carbonate veins carry small amounts of galena and sphalerite. Complex faulting within the deposit makes drill-hole correlations difficult. Alteration assemblages include an early potassic phase, almost completely destroyed by later phyllic alteration, and surrounded by a propylitic assemblage dominated by ankeritic carbonates in altered sedimentary rocks.The deposit has characteristics of bath the alkalic and calc-alkalic classes of porphyry copper deposits. The development of quartzvein stockwork suggests a calc-alkalic affinity, but the hostrocks contain little or no free quartz, molybdenum is present in trace amounts only and gold values are significant. Copper grades vary between wide extremes with unusually high grades in some sections of the deposit. The weight of evidence available in the 1970s led us to place the Red-Chris deposit firmly in the alkalic family. The quartz-sericite alteration assemblage was attributed to breakdown of potassium feldspar in a near-surface alteration environment in which seawater may have had a significant role. These interpretalions are retained here, but preliminary conclusions from the most recent work suggest that they may require some modification."

Jan 1, 1995

By Siavash Zamiran, Abdolreza Osouli

"One of the most concerns of room and pillar mining system is subsidence of the ground surface due to coal mining particularly in room and pillar mines. Subsidence of ground surface is a result of floor, pillar, or roof failure of the mine. At the same, due to many difficulties associated with surface disposal facilities of coal refuse, some mining companies are trying to use underground space as a disposal storage place. In this study, stability and subsidence analyses of an underground coal mine located in the Illinois Basin are conducted. This room and pillar mine was abandoned and later on was used as a storage place to accommodate the coal fine refuse with slurry backfilling method. The geological stratigrophy and geomechanical properties of the mine floor and roof were collected. Floor and pillar stability analyses were conducted for areas with various extraction ratios. The stability of the mine was evaluated both prior and after slurry backfilling. The floor and pillar stability analyses results of the mine due to moisture exposure after slurry backfilling are discussed. The subsidence potential due to mine failure is also evaluated.INTRODUCTIONA typical lithology of coal seams in the Illinois Basin consists of weak underclay stratum. The immediate weak underclay causes frequent floor instability problems in Illinois underground coal mines. There are two different stages in assessing floor stability of the mines where slurry backfilling is planned. The first stage is during the mining operation when weak underclay layer squeezes under pillar stress and results in punching or bearing capacity failure. The second stage is after slurry backfilling. During this stage, the slurry material soaks non-durable floor layers and causes strength reduction in floor material. Pillar stability conditions should also be taken into account during both the operational period and after the slurry backfilling."

Jan 1, 2015

By S. Sakurai

"Gravitational force is an external body force acting on underground structures. It should be noted that gravitational force cannot be replaced with the surface traction vector (Cauchy stress) which is an internal force. This fact should be properly taken into account in a numerical analysis of underground structures, particularly for structures such as vertical shafts, tunnels, and caverns constructed at great depths. It is obvious that the gravitational force must be conserved at all times.In conventional numerical analyses, the initial state of stress of the ground medium is firstly calculated under the gravitational field. This means that the gravitational force is replaced with stress (surface traction vector), and after that only the initial stress is considered in the calculation of the stresses and displacements of the structure. It should be noted that the initial stress is Cauchy stress consisting of a surface traction vector, while the gravitational force is a body force acting on the mass of the materials. This computational approach may be acceptable for elastic problems because the principle of superposition is valid for elastic materials. However, this approach becomes questionable for elasto-plastic materials because there is no guarantee that the principle of superposition is valid for them.Furthermore, another problem exists in elasto-plastic analyses: The stress state in a plastic zone must satisfy a yielding criterion such as that of Mohr-Coulomb. In order to make the stress state satisfy the criterion, an excess stress beyond the yielding criterion should be transferred to an elastic zone existing outside of the plastic zone. This seems to always be possible, because an elastic zone always exists, no matter how large of a plastic zone appears. In some cases, however, the excess stress cannot be transferred to the elastic zone because the gravitational force must be conserved. Therefore, it is obvious that the magnitude of stress around underground structures may become large and surpass the yielding criterion at great depths where a large gravitational force exists.In this paper, it is demonstrated that in a conventional elasto-plastic numerical analysis of a vertical shaft at a great depth, all the stress components around the shaft become very small, even though a large gravitational force exists. This strange result may be due to the fact that the gravitational force is not properly taken into consideration in the numerical analysis."

Jan 1, 2015

By J. S. Laskowski

Anisotropic minerals are important constituents of many ores. This group includes both valuable minerals (e.g., molybdenite in Cu-Mo ores) as well as gangue minerals (e.g., talc in platinumbearing sulphide ores in South Africa, graphite in Cu-Ni sulphide ores in Canada, chrysotile in Ni sulphide ores in Australia, and clay minerals in all types of ores). Aqueous suspensions of anisotropic minerals exhibit different properties than suspensions of isotropic minerals. The presence of anisotropic minerals in flotation circuits affects the flotation process.

Jan 1, 2012