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Stress induced, gravity-assisted failure processes typically dominate long before stress levels approach the strength of the intact rock (at approximately smax > 0.4UCS where smax = 3s1 ? s3 and UCS is the Unconfined Compressive Strength of the intact rock (Martin et al. 1999)). Under these conditions, discontinuities typically become clamped and the failure process becomes brittle. This brittle failure process is dominated by new stress induced fractures growing subparallel to the excavation boundary. While it is possible to identify areas with the potential for brittle failure, for example, using the general assumption that brittle failure will occur in areas at right angles to the major principal stress (Hoek et al., 1995), when the threshold smax > 0.4UCS is reached in areas around the tunnel boundary, or elastic modelling and the Hoek-Brown brittle parameters proposed by Martin et al., (1999) (i.e. m? 0 and s ? 0.11), amongst others, recent observations discussed by Everitt & Lajtai (2004), and Kaiser (2005; 2006) suggest that brittle failure processes are enhanced when structural features such as joints, weakness zones, bedding planes or foliations are preferentially orientated around the excavation boundary creating stress raisers which in turn facilitate the stress-driven rock mass disintegration process (e.g., as illustrated by Everitt & Lajtai (2004) on Figure 1b). Such weaknesses induce stress heterogeneities that thus promote tensile-spalling failure processes (Diederichs 2000). The observations suggest that stress induced damage can occur ?prematurely? depending on the orientation of micro and macro structures in situations where the known stress conditions should not yet initiate brittle failure processes. In general, when structural features (micro and/or macro), especially foliations, are present in a rock mass, the strength is effectively reduced, largely due to tensile strength heterogeneity in areas depending on the orientation of the structural features with respect to the excavation boundary. As a result, stress induced damage could occur in areas not normally considered due to the influence of anisotropy (Figure 1).

May 1, 2009

By Silvana Costa

In the last two decades, there have been nearly no new mining towns built in Canada. Governments and mining companies have viewed long distance commuting (LDC), commonly known as fly-in-flyout or fly-in mines, as a way to avoid problems associated with building a new community and providing for its sustainability after mine closure. LDC is also considered more cost-effective than building a mine town. The intensification of the use of LDC in the Canadian mining sector has been quite rapid, particularly in northern regions. However, LDC has implications to employees, their families and communities, which deserve further examination, particularly considering the significant expansion in Northern mining and Aboriginal participation in this sector. This paper presents a review of the major issues in long distance commuting, both from an industry and community perspectives. It is a result of preliminary investigation for a PhD research project that will be pursued by a Bridge Fellow and UBC Mining Sustainability Working Group member, and guided by an interdisciplinary research team at the University of British Columbia (UBC). The Bridge Fellowship Program is research-training program linking the UBC?s Faculties of Medicine, Engineering and Graduate Studies. Its mission is to develop creative evidence-based prevention measures for public, environmental and occupational health problems. The SWG is an interdisciplinary student group based in the UBC Department of Mining Engineering, committed to respond to the complex sustainability-related challenges currently faced by the mining industry. In other to pursue this project, it is paramount that industry and local communities alike participate in the development and clarification of research questions as well as in the research design. It is hoped that this paper will function as an invitation for industrial and community partners for such study. The main themes identified for this research are occupational health and safety of LDC employees, family life impacts and community health impacts of this model of resource development.

May 1, 2004

By Y. P. Malhotra, JE. C. Carter

"Syncrude's overburden removal requirement ranges from 20 million to 30 million bank cubic metres per year to meet tarsand demands for the production of 129,000 barrels of synthetic crude oil per day. The economic tar-sand lies beneath a variable thickness of overburden materials, composed of silts, clays, some sands of lacustrine origin, wind-deposited sand dunes, and out-wash sands and gravels.For the removal of overburden, Syncrude commissioned its own mobile equipment fleet in January 1981. This fleet consists of two Demag 241 hydraulic shovels, ten Titan 33-15B trucks and support equipment. Prior to this, all overburden removal was being carried out by contractors.This paper presents an overview of overburden removal at Syncrude, with particular reference to the performance of its own fleet.IntroductionThe Syncrude Tar Sands Plant was officially opened on September 15, 1978. After an expenditure of approximately $2.26 billion, the second and the largest commercial tarsands plant was on stream toward a permit production rate of 129,400 barrels of synthetic crude oil per day. The Syncrude Plant, a joint venture of six oil companies, the federal government and the Alberta government, is a major step forward toward the goal of Canadian energy self-sufficiency.The Mildred Lake operation of Syncrude Canada Ltd. Is located 40 km north of Fort McMurray and 480 km northeast of Edmonton in the Province o f Alberta.Synthetic crude oil leaving the plant is a blend of two-third s gas oil and one-third naphtha. The two streams combine in a pipeline and flow to Edmonton. The product takes six days to make the journey, arriving at four locations in the city Imperial's Strathcona Refinery, Gulf's Edmonton Refinery, the Interprovincial pipeline terminal and the Trans-Mountain pipeline terminal. Each Syncrude owner receives a share of oil equal; to its percentage of ownership in the project. At the present time, the oil is being utilized by Canadian refineries from Vancouver to Montreal."

Jan 1, 1983

By E. Fried

Cemented paste backfill (CPB) is an innovative tailings management method that consists in returning considerable amounts of mine tailings into the underground mine openings. The filled stopes thus participate to the ground support that allows maximizing orebody extraction and a safer environment for the mine workers. There are also significant environmental advantages of using CPB. Indeed, up to 50% of the concentrator tailings can be backfilled, leading to a smaller volume of problematic waste materials to be managed at the surface. Once the CPB is placed, or when the mine is flooded at its end-life, the backfill is subjected to underground water flows that may leach and spread the pollutants (mainly metals, sulphates, and acidity) which can contaminate the underground waters. The aim of this study is to characterize the leaching properties of CPB material and to identify the cement phases that ensure the metal fixation. A laboratory procedure was implemented consisting in the preparation of various paste backfill mixtures using sulphide-rich and sulphide-free materials, different types of binder, and mixing waters having various sulphates, copper and zinc concentrations. After 90-days curing time, the samples were submitted to column leaching tests. The CPB materials were flushed each day with 100 ml of deionised water during 100 days. The collected leachates were then analyzed for pH, Eh, electric conductivity and chemical composition. For some samples, a differential acid neutralisation test was carried out. The objective of this experiment is to dissolve selectively the hydrated phases by adding incremental acid concentrations. By analyzing punctually the equilibrated solutions, the composition of the dissolved phases and their metal content can be estimated. The leaching test results showed that the pH of the leachates remains alkaline during the test period. When the pH decreases under 10 (after 30 days), different behaviours in terms of chemical element release (especially for zinc) were observed. During the test, the oxidation of pyrite seems to slow down, probably due to passivating phenomena. Moreover, the differential acid neutralisation test results allowed a better understanding of the CPB mineralogy and the Zn-bearing cement phases. Zinc and the other metals seem to be fixed within a calcium-magnesium silicate.

May 1, 2007

By D. Simon

This paper studies the effect of binder type and content on the early age development of cemented paste backfill (CPB). The early age development of the mixtures is analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDX). These tests show that the early age development of CPB is sensitive to changes in the paste composition. The properties of the CPB depend on the cement content and hydration time. The quantity of hydration products increases with hydration time for all of the mixtures containing cement. However, the high cement content pastes (at least 50% PC) exhibit complete coverage of the PC grains and mine tailings by C-S-H, while the low cement content paste shows scattered coverage of the PC grains and mine tailings and a higher void ratio.

May 1, 2007

By Louis Frost

"A FIRE which forced the sealing -of the east side of Dominion No. 16 Colliery in the Town of New Waterford, Nova Scotia, occurred on October 6th, 1952 (Figure 1).So far as can be ascertained, the fire was first noticed in the roof of No. 7 East Lateral, after a brushing shot had been fired in the pavement. There appears to .be no doubt that this shot •blew out, igniting a small feeder in the roof.Regular air measurements and air samples, taken over a long period prior to the fire, indicated that the ventilation was adequate, for at no time had the percentage of CH4 in the general air current exceeded one per cent in this location. The last regular monthly samples and air measurements, taken at the end of September, showed the condition of the ventilation to be:Return at the Top of No. 8 East WallQuantity .... 27,700 cu. ft. per min.CH4 .......................... 0.32 per centC02 ................................ 0.10 per centHowever, in the week preceding the fire the mine examiner on four occasions had reported small feeders of gas at the face of the brushing in No. 7 East Lateral.Figure 2 is a diagram of the working place where the shots were fired. The face brushing had been shot down at 3 :45 p.m. and cleaned up. Two 'hurdle screens' had also been erected, one close to the face brushing and the other fifteen feet from the face."

Jan 1, 1953

By L. Connolly, F. R. De Luca

"Rubber liners at Denison Mines Limited are used in 10 1/2x 24' low discharg0 pebble mills. These were originally 10 1/2 x 13 Dominion overflow type ball mills. Experience here shows that the wear of rubber and ni-hard lifters is approximately the same in the feed end half of the mill, while the wear of rubber lifters is much greater in the discharge half. The wear of rubber plates is considerably less than white iron in the feed end half of the Mill and slightly more in the discharge end half of the Mill. Rubber components are lighter to handle but their installation is time consuming. This leads to the conclusion that a combination of ni-hard lifters a~~ rubber plates is the most economical compromise in Denison's case, for the Mill. Rubber discharge grates are superior to steel grates, while steel feed end liners are superior to rubber.The Use of Rubber Mill Liners at Denison Mines LimitedGrinding is done in two identic0al circuits each consist-ing of one 10 1/2 x 14' Dominion overflow rod mill, two Dorr Oliver quadraplex rake type classifiers, two 10 1/2 x 24' Dominion low discharge grate pebble mills and ancillary pumps and conveyors for pebbles. There is one centrally located distributor box that receives the discharge of the 4 pebble mills and splits it out to the classifiers."

Jan 1, 1974

By C. Moctezuma

Since the start up of the IMMSA electrolytic zinc refinery in 1982, the dissolved iron coming from the acid attack of the ferrites has been precipitated by the jarosite process. At the beginning of operations, sodium jarosite was produced; however, the plant was converted to ammonium jarosite in 1990. The final storage of the residue is on the company&apos;s property adjacent to the plant, over the natural surface of the land. Before the construction of the refinery, several studies were done in order to evaluate the characteristics of the ground, such as, permeability, underground water localization, etc. The results showed that the site was adequate for the storage of this kind of material. For several years, the jarosite residue was filtered on rotary drum filters and was sent as a pulp to the storage area for settling. The water from the storage pond was recycled to the re-pulp tank for the jarosite residue. These filters were replaced in 1999 by an automated filter press. Since then, the jarosite residue has had a lower water content, and the zinc recovery improved. At present, a second filter press for the jarosite circuit is in the acquisition process to diminish the soluble zinc content in the residue from the present value of 2% to < 1% Zn.

Jan 1, 2006

By André Desbiens, Jocelyn Bouchard, René del Villar

"The metallurgical performance of the column flotation process is determined by the concentrate grade and recovery. Although the former can be continuously measured using an on-stream analyzer, the latter must be estimated by a material balance calculation based on seldom verified steady-state assumptions. Consequently, the automatic control and optimization of flotation columns should be performed using secondary variables having a strong influence on the metallurgical performance, such as froth depth, gas hold-up or bubble surface area flux and bias. The aim of this paper is to present a model-based automatic control strategy using froth depth and bias measurements obtained from virtual sensors developed at Laval University. Preliminary pilot plant results on two-phase (water– air) and three-phase system (water – minerals – air) will be presented and eventual industrial implementation of such a strategy as well as the possibility of achieving effective real-time optimization from bias and froth depth measurements will also be discussed.INTRODUCTIONFlotation columns have been widely studied and used in mineral processing for about twenty years. Although a great deal of work has been accomplished to understand the influence of different variables such as froth depth (H), bubble surface area flux (Sb) and bias (Jb) on the metallurgical performance, the measurement of some of these variables is still difficult to be performed – except at the laboratory level – because in most cases, no commercial device yet exists.As a result of this, it is almost impossible to achieve neither efficient control nor optimization of the process at the industrial level, even in open-loop operation. This paper aims at presenting a simple control strategy of froth depth and bias. Description of the sensors used to achieved measurements, preliminary pilot plant results for froth depth control, eventual industrial applications and possibilities for process optimization are also treated."

Jan 1, 2003

By P. Clinton Milne

Uranium mines in Washington State include the producing Midnite and Sherwood mines and several mined-out deposits, the most productive of which was the Daybreak mine. The Midnite mine is generally classified as a hydrothermal deposit consisting of tabular orebodies in Precambrian pelitic and calcareous metasedimentary host rocks. The host rocks occur as roof pendants in a Cretaceous porphyritic quartz monzonite intrusive; the quartz monzonite averages 12 ppm U308 The uranium deposit appears to have undergone a complex genesis, involving a series of depositional and enrichment stages. The Sherwood uranium deposit, approximately 4 miles south of the Midnite mine, occurs near the bottom of a basal Late Cretaceous to Paleocene arkosic conglomerate. The conglomerate lies nonconformably on the porphyritic quartz monzonite that is associated with the Midnite deposit. The Sherwood and Midnite uranium deposits may have had a similar genetic history linked by a common uraniferous pluton source, ground-water action, and/or leaching of uranium-rich ash flows from now-eroded, overlying, Eocene volcanics. The Daybreak deposit, in northeastern Spokane County, consists entirely of secondary uranium mineralization (metaautunite) in a quartz monzonite pluton. Mineralization is confined to a low-angle fault zone and is most highly concentrated at the intersection of primary and secondary shears. Both hydrothermal and ground-water origins are feasible. Besides the Midnite-Sherwood area, 14 other areas in the western Okanogan Highlands physiographic province and Cascades region have favourable characteristics for uranium potential. Criteria include the existence of uranium occurrences, Tertiary basin sediments with intercalated volcanic and volcaniclastic rocks, favourable geochemical data, alkaline plutons associated with uranium occurrences or borders of Tertiary basins, and structural controls.

Jan 1, 1979

By Sunil Koppalkar, Liming Huang

"Since late 1980s the research group led by late Professor Andre Robert Laplante at McGill University undertook fundamental studies and applied research of the Knelson Concentrator (KC) and developed a sustainable method to correctly estimate gravity recoverable gold (GRG). In the early time a concept of ‘free gold’ was used, it was defined as the gold that could be separated and recovered from gold ore by amalgamation. Due to health and safety hazards, its practical use had declined. Around 1994, a methodology using a 3-in Knelson Concentrator to measure gravity recoverable gold was established at McGill University. Through more than 10 years’ improvement and optimization, this technique had become a standard method to evaluate GRG for gold ores, gold plant streams and platinum group metals. Until 2006, about 200 GRG tests had been carried out at McGill University for the ores from all over the world. Recently, a modified version of GRG test (short test) with the advantages of reduced processing time and lower cost had been developed for the mundane needs of gold industry.INTRODUCTIONGold gravity recovery has evolved significantly over the past twenty-five years, mainly because of the advent of the Knelson Concentrator (Knelson 1988, 1990, 1992, Laplante 2000). Now, a series of Knelson Concentrators for different applications are manufactured and used in gold industry all over the world (Knelson Concentrators 2004).In 1980s the Knelson Concentrator gained acceptance from mining industry as an effective device for the recovery of gold from grinding circuit. Knelson Concentrator became the obvious choice because of its design features: a relatively long processing time without concentrate discharge (compared to some other centrifuges, such as Falcon Concentrator and Chinese Yunxi Centrifuge at that time), large throughput capacity, treating a wide size range of material, yielding a high grade concentrate with small mass that could easily be smelted. As more and more Knelson Concentrators were accepted in gold industry, mineral processing engineers faced with challenges: what are the separation mechanisms of the Knelson Concentrator? How much gold can be extracted for an ore if a Knelson Concentrator is installed? For answering these questions, a laboratory scale Knelson Concentrator was created."

Jan 1, 2007

By Euler De Souza

This paper presents a study conducted to assess sillmat behaviour during undercut mining and to provide a comprehensive understanding of the effects of arching and sillmat thickness on stability. The design study investigated the effects of such parameters as stope width and height, closure strains, orebody geometry and inclination, wall roughness, fill properties and cure time on the stability of cemented sillmat during undercut mining. Arching effects have been quantified based on centrifuge modeling studies for the different mining conditions. Observations have indicated that the degree of arching is a function of stope geometry, wall roughness, fill cohesion, and wall closure. Arching effects increased with decreasing stope width, increasing backfill cohesion and frictional resistance, increasing wall roughness and with wall closure.

May 1, 2002

?? Intro ?? Mass blast principle ?? LaRonde evolution toward mass blast ?? Overview ?? Mining method ?? Longitudinal ?? LaRonde evolution (2002 to today) ?? Drill and blast design ?? Consumptions and statistics ?? Mucking strategies ?? Case study ?? Examples ?? Conclusion ?? As underground mines extends to greater depths, few questions must be asked: ?? How to: keep operations safe eep operation effective reduce the cost maintain and control the dilution ?? Geomechanic method and practices; significant advances have been observed in the field of: ?? ground support ?? mining sequencing ?? Drilling and blasting; research and development has been less extensive, probably due to the following characteristics: ?? Drill and blast are mainly production-oriented ?? Drilling and blasting are more oriented toward productivity ?? Technology relies heavily on suppliers ?? Highly stressed ground conditions ?? generally help the explosives to break the rock for fragmentation ?? intensify over-breaks or blast-induced

Feb 1, 2008

By Turgut Yalcin

"Recent years have seen a resurgence of interest in flotation cell design, and one of the areas where attention is being focused is flotation in centrifugal fields which aims at increasing the flotation rates by forced bubble-particle contact.A new cycloflotation device was developed at Laurentian University and tested on the nickel ore of Falconbridge Limited in Sudbury. In comparison with conventional flotation, cycloflotation yielded at least seven times faster flotation rates in terms of the mass of solids floated per unit time per unit flotation volume, while producing concentrate grades similar to those of conventional flotation. These results, which were obtained with a bench-scale ""cyclofloat cell,"" suggest that cycloflotation has the potential of setting a new direction in flotation technology.IntroductionFroth flotation is no doubt the dominant separation technique in the mineral processing industry. Since its inception early in this century, much research effort has been and is still being expended on this process. Until recent years, emphasis seems to have been placed on the chemical aspects of flotation, but there is now an increased awareness for the need to improve flotation machine performance and more and more attention is being directed towards this area. In a 1982 article on ""Flotation Machines"" (Young 1982) it is stated that "" ... by now the design of the machines used would have reached a high level of perfection, ... In fact, this is not the case ... "".The process of flotation in a flotation device may be considered to take place in several distinct stages as follows:"

Jan 1, 1994

By K. Leung, J. E. Udd, L. B. Geller, F. Kitzinger

"Sixteen miners died tragically at the Paymaster gold mine in Timmins, Ontario, in February 1945 when a badly corroded hoist rope broke. The investigation of the Royal Commission that followed arrived at a number of recommendations (The Legislative Assembly of Ontario, 1947) aimed at avoiding future disasters of this kind. One consequence was the development and legislated use in Canada, several decades ago, of powerful electromagnetic (EM) instruments for the non-destructive testing of mine shaft wire ropes. The authors have been involved for many years in the design, production, and testing of EM instruments (Geller and Udd, 1990, 1992; Geller and Kitzinger, 1991; Geller et al., 1992). Since the mid-1990s, particular attention was paid to the design and operational results obtained from the computer controlled portable MagnographTM II wire rope tester (Geller et al., 1995, 1998).In the present paper, the authors summarize further hardware- and software-related developments of this instrument. Further, an account is given of the results obtained from the most recent design known as the Perma- ScanTM testing system. This is also a computerized dual-function system. In it, however, the sensor head is designed primarily, if not solely, for permanent installation and for remotely controlled operation. This represents a basic departure from traditional designs, which were intended for ad hoc temporary installations. The remote-controlled instrument described in this paper has now been in operational use for more than four years."

Jan 1, 2003

By H. A. Dakin

"An introduction to the metallurgical requirements of the Flin Flon concentrator reveals the magnitude of ore blending which is required in its operation of three flotation circuits. The resulting variability in flotation heads which has in-creased the separations complexity justified the development of an on-line analysis system.This paper provides a summary of the development and operation of that system. Particular attention is devoted to the problems encountered and where possible their solutions; as the requirements of accurate information and minimum downtime of the sampling system and x-ray analyzer are considered essential. The addition of a recess central computer has provided information in a more easily understood form and as well has allowed the start of automatic reagent control.An indication of the on-line analysis system's value to the concentrators' operation is provided by an examination of the plant in metallurgical data and reagent costs in previous years.The metallurgical plants of Hudson Bay Mining and Smelting lie adjacent to the city of Flin Flon on the Manitoba-Saskatchewan boundary. Plant operations commenced in 1930 treating copper-zinc ore from the local mine. In recent years ore bodies near Flin Flon and in the Snow Lake area, about seventy-five miles east, have been brought into production.By the beginning of 1973 the number of producing mines had increased to nine; with all the ore being handled by the Flin Flon concentrator. Figure l, showing mine ore assays during 1973 indicates the variation in metal content possible."

Jan 1, 1974

By Khosrow Ebrahimi

We document the occurrence, mineralogy and firing properties of magnesite from hydrothermal deposits in the upper Cretaceous ophiolites of Eastern Iran. These deposits occur as thin veins of nearly pure cryptocrystalline magnesite with only trace amounts of quartz, calcite, and dolomite. Ratios of CaO/SiO2 in the bulk ore are variable. The composition of dead-burned magnesite from these deposits, calcined at different temperatures and durations, is predictable from phase equilibria. Textures of the calcined magnesite were studied by SEM; results show that the principal impurites produced during calcination are forsterite, monticellite, merwinite, dicalcium and tricalcium silicates, and that these are located principally at triple junctions of the periclase crystals. The size of periclase crystals increased with temperature and duration of calcination and the amount of periclase-periclase grain contacts was reduced by increasing the concentration of impurities in the starting products. EPMA show: 1) that CaO and FeO contents in periclase increase steadily with an increase in the CaO/SiO2 ratio and the FeO content of the bulk ore, respectively, and 2) that limited solid solution exists between impurites. This study demonstrates that high quality dead-burned magnesia refractories can be produced from the Iranian magnesite with low CaO, SiO2 and FeO contents.

May 1, 2004

By Knut F. Garshol

Quality and durability of sprayed concrete depends on the concrete mix design, the type and use of accelerator and all the aspects of the placement onto the rock surface in the underground working. A large number of influence factors are involved and they must be managed for a successful and durable permanent sprayed concrete structure to be produced. The paper discusses some of the central issues, including how to view the long-term effects of chemical admixtures and accelerators in wetmix sprayed concrete. Permanent lining sprayed concrete for rock support is increasingly being used today and the durability can be equally achieved as for any other concrete.

May 1, 2003

By Gerald Whittle

What is Enterprise Optimization? Releasing value through better planning decisions: Philosophy, Methodology, Software The key to 5% -35% increase in enterprise value (NPV) The culmination of 25 years development in optimization for the mining industry ?Jeff Whittle Simultaneously optimizing: ?all steps in the value chain ?all assets in the enterprise portfolio ?all periods together

May 1, 2010

By H. Harzer

Statistics Canada record s indicate that in recent years 70 to 80% of the entire Canadian coal production originated from Western Canadian mines, in which about 55 to 65% of the coals are bituminous. Until recently, less than 20% of the latter were extracted by underground methods , the remainder being surface-mined. However, it is estimated that within the foreseeable future up to 80 or 90% will have to be gained by underground techniques. Although Western Canadian coal resources are considerable, they are unfortunately locked in severely distorted, steeply pitching and faulted seams of variable thickness. Consequently, their economic extraction poses serious engineering problems. One possible solution to the problems is to apply hydromechanical methods to underground mining. This is a well-proven method shown to be economically viable under Western Canadian conditions. This paper endeavours to widen the scope of published data on hydraulic coal mining and is based on practical engineering and cost data gathered through contacts with West German designers and operators of hydraulic mines.

Jan 1, 1978