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By A. J. Keen

"Cominco's Polaris Mine is an underground lead/zinc operation located on Little Cornwallis Island in the Canadian High Arctic. Polaris is the world's most northerly base metal mine, situated at about latitude 75°N and longitude 97°W (Fig. 1). The closest community is Resolute Bay about 100 km to the southeast.During the construction and development phase Cominco adopted a unique scheme to save time and money. Many facilities including concentrator, powerhouse, shops and warehouse were built on a barge in southern Canada. The barge was towed 4800 km to the site in August 1981. Production at Polaris began in November 1981. The current mining rate is 1 million tonnes per year. The mine employs 250 people with about 190 on site at any time.GeologyThe deposit is a Mississippi Valley type orebody and lies near the top of the Ordovician Thumb Mountain Formation. Ore minerals consist of sphalerite and galena with the gangue being predominantly dolomite with calcite and marcasite. The orebody is situated completely within permafrost, consequently the voids frequently found in the ore are filled with ice. The orebody strikes north-south, dips approximately twenty degrees to the east and takes up an area about 400 m wide by 700 m long. The upper portion of the orebody (60 m to 150 m below surface) lies in an area called the Panhandle Zone. The deeper portion of the orebody known as the Keel Zone extends to 300 m below surface (Fig. 2). The deposit is strongly zoned with a high grade zinc/lead and iron-rich tabular core overlain and underlain by vein, stringer and breccia mineralization. The ore reserves at January 1991 were 14.6 million tonnes at 3.6% Pb, 13.7% Zn, 3.2% Fe, after producing 8 million tonnes at 3.9% Pb and 14.2% Zn since November 1981"

Jan 1, 1992

By G. Simard, D. Boudeville, A. Leclerc, A. Boivin

"The objective of this work is to study the various parameters that affect the overflow clarity of gravity settlers used in the precipitation circuit of alumina hydrate from the Bayer process. A mathematical model incorporating the size distribution of the feed suspension (Multi Size Group model), its diphasic nature (Schiller Naumann model) and the presence of turbulence (Shear Stress Transport model) has been solved numerically using ANSYS-CFX software. Preliminary results indicate that the overflow clarity is mainly controlled by lateral diffusion of fine particles (~20µm) from the exit of the feed well and by their upward transport from the sediment bed interface. Also the turbulence pattern in the settling zone seems to play a significant role in this vertical transportation. The validity of the model has been verified by comparing the measured solid concentrations from a pilot classifier with the calculated ones. This model could provide mineral processing plant operators and designers with a tool to optimize the configuration of classifiers with respect to the overflow clarity.INTRODUCTIONProblemIn the Bayer process, alumina hydrate precipitation from the saturated liquor is initiated in settler by adding crystallization seeds. Most of the precipitated alumina settles to the bottom of the tank while the liquor and the remaining alumina rise to the top, where they are removed at the overflow. Ideally the overflow clarity, which depends on the operational mode of the classifier, should be controlled within targeted limits."

Jan 1, 2016

By J. E. Danoczi

Shore Gold Inc. (Shore) is presently designing a diamond processing plant for the Star and the Orion South kimberlite deposits in the Fort à la Corne area kimberlite field in central Saskatchewan. The first step in the plant is diamond liberation and occurs in the comminution section. Diamond liberation is the process of breaking up the kimberlite rock, as ?gently? as possible since essential to the diamond liberation process is the minimization of diamond damage, particularly for the larger, high value diamonds. The Southern African diamond mines traditionally use Jaw and Gyratory crushers as their primary comminution method. However, these diamond mines generally process the harder, competent kimberlite that is located in the diatreme zone as well as the root zone of the volcanic pipe. Softer kimberlite is typically located in and around the crater area of a volcanic pipe and it is this source of kimberlite that makes up the majority of kimberlite for both the Star and Orion South deposits. These softer kimberlites can be readily broken up using abrasion and attrition imparted by AG mills, this being the preferred method of comminution for minimizing diamond damage.

Nov 1, 2011

By R. B. Casault, J. D. Boyd, D. R. Bell

"Full-scale sections of three different types of Grade 483 line pipe have been evaluated extensively. The variations in chemical composition, optical microstructure, tensile properties, hardness and Charpy impact toughness with specimen orientation and location were determined. Significant variations in several properties, notably Charpy shelf energy, impact transition temperature, inclusion content and ferrite grain size, were observed for different locations in the pipes. The results indicate that current specifications call for test samples for the most conservative locations, except for impact tests. Minimum Charpy impact values generally occur at the II2-width location, which may be a more appropriate specified test location than the present I/4-width location. The anisotropy of impact toughness, and the importance of low sulphur content and inclusion shape control for adequate toughness in the transverse/rolling-direction orientation were demonstrated. The orientation of impact specimens is critical for spiral-weld pipe, and the current specification test is non-conservative in that it can give results which are two to three times higher than the minimum value for the steel.IntroductionThis report presents the results of an extensive metallurgical evaluation of three different Grade 483 line-pipe steels. The sample material came from full-scale sections of line pipe, which represented current commercial practice at the time of manufacture (1975-1977). Since then, significant improvements have been made in the manufacturers' procedures for producing skelp and pipe, and the line-pipe specifications have been revised. Hence, the information in this report is dated in terms of current design, but it is unique and significant in several respects:"

Jan 1, 1982

By R. G. L. McCready, R. O. van Everdingen, M. Kalin, R. van Everdingen

"This paper is based on data generated between October, 1986 and October, 1989, during the implementation of an Ecological Engineering close-out for a zinc mine in Northern Ontario, where 690000 tonnes of tailings contain 41.1% pyrite and 4.1% pyrrhotite. The objective was to determine rates of sulphide oxidation and iron precipitation in the tailings. Those rates are relevant for the assessment of the long-term effectiveness of biological systems employed in the removal of heavy metals from contaminated drainage issuing from tailings.Data were collected on the topography and stratigraphy of the tailings basin, subsurface temperatures and groundwater levels, and chemical analyses were made of water samples collected from a number of piezometers. The thickness of unsaturated tailings varied widely between individual piezometer locations; annual maxima ranged from 0.67 m to 3.55 m, and annual minima from 0 to 2.68 m. Sulphate concentrations ranged from 36 mg/L to 20180 mg/L; iron concentrations from 0.36 mg/L to 9938 mg/L; and zinc concentrations from 0.33 mg/L to 1123 mg/L.The geochemistry of the piezometer samples suggests that some of the initial Fe content, resulting from metal sulphide oxidation, is subsequently precipitated in the tailings pile and, possibly, in the underlying unconsolidated sediments, probably in the form of iron-hydroxide and Na-jarosite. Other metals such as Zn may be co-precipitated with Fe. The discharge of a portion of these metals to the environment would be delayed by this process. Some of the initial sulphate may also be lost from solution, probably by precipitation of gypsum; approximate saturation degrees for gypsum ranged from -3.27 to +0.47. The precipitated minerals will somewhat decrease the porosity and permeability of the tailings.Sulphide-oxidation rates, calculated using the analytical results and the estimated amount of annual recharge at the tailings site, average 0.0057 mol/kg/yr. Calculated iron-precipitation rates average 0.000386 mol/kg/yr. It is concluded that the characteristics of seepage from mining wastes may change with time, reflecting the solubilization of precipitated secondary minerals."

Jan 1, 1992

By B. Hart, D. J. Miller, J. T. Francis, M. C. Biesinger, Smart. R. St. C.

Diagnosis of the surface chemical factors playing a part in flotation separation of a valuable sulfide phase requires measurement of the hydrophobic and hydrophilic species that are statistically different between the concentrate and tail streams. Time of flight secondary ion mass spectrometry (ToF-SIMS) can be used to identify sufficient particles of a specific mineral phase for reliable statistics determining a mean value for each species with 95% confidence intervals (1). Using the region of interest (ROI) facility in the Tof-SIMS software, a mass spectrum from each particle, at 1-2 monolayer sensitivity, is recorded and stored. This analysis is reported for a chalcopyrite / pyrite / sphalerite mineral mixture conditioned at pH 9 for 20 minutes in order to study transfer of copper from chalcopyrite via solution to the other two mineral surfaces since this mechanism can be responsible for their inadvertent flotation in copper recovery. Analysis from mineral selection based on specific ToF-SIMS signals (eg. Pb, Zn, Cu, Fe, Fe/Cu) indicated no statistical difference in the copper intensities on pyrite and sphalerite after this conditioning. Principal component analysis (PCA) of the ToF-SIMS imaging data identifies combinations of factors strongly correlated (positively or negatively) in images or spectra from mass spectra recorded at each of 256x256 pixels in a selected area of particles. PCA is a better method of selecting minerals due to multi-variable recognition. It has clearly separated a statistical difference in copper intensities between the sphalerite and pyrite phases. The method has been extended to samples from an operating plant again with excellent phase recognition and diagnostic surface chemistry.

Jan 1, 2004

By J .. Carignan, Y. Dembele, J .. Guha, A. Fowler, A. Gobeil

The Barlow Lake stratigraphic section comprises the top of the Gilman Formation, the Blondeau Formation and the three sills of the Cummings Complex. Representative samples were analysed to allow characterization of the chemo-stratigraphic profile and geochemical affinity of the six rock facies found in the section. All the mineralized horizons are associated with sedimentary units. Geochemical signatures associated with the mineralizations are either very weak or very localized and shown by increases in K20 around the mineralizations and Fe203 near them. The mineralizations are stratiform, synvolcanic but resedimented and remobilized by regional metamorphism and possibly by hydrothermal activity initiated by the intrusion of the Cummings Complex. The evolution of the sedimentary basin with the decrease of its depth is confirmed by the chemo-stratigraphic profiles. Stratigraphic position in the section is important in order that the chemo-stratigraphy may serve as a guide for mining exploration in the distal facies of the Blondeau Formation.

Jan 1, 1984

By H. D. S. Miller

"This paper introduces a new approach for the design of rib pillars. The approach involves an empirical method for pillar design and a discussion of the pillar stability used for open stope mining methods.The empirical method predicts the degree of stability of rib pillars. Pillar load is estimated using two and three dimensional numerical modelling. Rock strength and the shape effect of pillars are used to account for pillar strength. The method has been calibrated with case histories from Canadian open stope metal mines and is compared with other methods used [or pillar design.INTRODUCTIONThe role of rib pillars in open stope mining is to provide stability to a mining block by limiting rock mass displacements and restricting the exposure of a rock mass in stope backs and stope walls. They also provide flexibility in ore extraction by dividing a stope block into multiple working faces.The use of backfill in open stope mining methods has reduced somewhat the need for optimum pillar design. In contrast to permanent pillar methods, the dimensions do not need to be minimized because the pillars are usually recovered in a later stage of mining. However, the consequences of poor pillar design are often overlooked and can still be severe. A pillar that does not perform its intended role may result in excessive stope or pillar sloughing, difficult and expensive pillar recovery, loss of permanent access and remedial costs such as development rehabilitation, artificial support or low productivity.Pillar design concepts of the past were not developed for open stope mining conditions and generally have not been confirmed for open stoping. The focus of this paper is to introduce an empirical design relationship specifically for open stope pillars. It provides a stable, yielding or failed pillar assessment for a given design."

Jan 1, 1989

By J. R. Meyer, P. L. Dean

"The Department of Mines and Energy is at present investigating the dimension-stone potential of the Nain anorthosite complex. These rocks are known to host occurrences of labradorite, a semiprecious gemstone known for its beautiful play of colours (chatoyance). Test blocks that contain 5% to 18% chatoyant labradorite were extracted from three prospects south of Nain. These have been slabbed and polished for further evaluation.Second-grade labradorite stockpiled around the Grenfell quarry on Tabor Island is also being evaluated as a potential source of aggregate for use in terrazzo tiles, precast concrete and epoxy-backed wall panels.IntroductionThe Nain anorthosite complex consists of approximately 10000 km2 of anorthosite and related basic rocks , which are well exposed along the coast of Northern Labrador (Fig. 1) (Emslie et al., 1972). These rocks have been known for centuries to host deposits of gem-quality labradorite. The chatoyant nature (i.e. the play of colours or labradorescence) of this semiprecious feldspar has been utilized mostly in the making of jewelry and other polished, handcrafted products. In the early sixties, Brinex Limited (now Brinco Limited) attempted larger scale commercial exploitation of labradorite, including use 'as building stone and in polished precast concrete for facings on buildings' (Brummer, 1984). After six years of work, which included market studies, Brinex decided that, at that time, the demand did not warrant further production.In recent years, there has been a dramatic increase in the markets for dimension-stone. In the period from 1980 to 1985, the demand in the United States for granite, much of which is imported, has increased 1735070 (Marble Institute of America, 1986). The dimension-stone industry's remarkable growth rate has, in part, resulted from new technology that makes it easier and faster to quarry and cut stone. This has allowed natural storie to compete with other building materials. Now, it is not only used for exterior cladding and walkways, but also on interior walls and floors, and in home and office furnishings, such as countertops for kitchens and bathrooms, table and desk tops, stairways, window sills, and fireplaces."

Jan 1, 1988

By J. R. Meyer, P. L. Dean

"The Department of Mines and Energy is at present investigating the dimension-stone potential of the Nain anorthosite complex. These rocks are known to host occurrences of labradorite, a semiprecious gemstone known for its beautiful play of colours (chatoyance). Test blocks that contain 5% to 18% chatoyant labradorite were extracted from three prospects south of Nain. These have been slabbed and polished for further evaluation.Second-grade labradorite stockpiled around the Grenfell quarry on Tabor Island is also being evaluated as a potential source of aggregate for use in terrazzo tiles, precast concrete and epoxy-backed wall panels.IntroductionThe Nain anorthosite complex consists of approximately 10000 km2 of anorthosite and related basic rocks , which are well exposed along the coast of Northern Labrador (Fig. 1) (Emslie et al., 1972). These rocks have been known for centuries to host deposits of gem-quality labradorite. The chatoyant nature (i.e. the play of colours or labradorescence) of this semiprecious feldspar has been utilized mostly in the making of jewelry and other polished, handcrafted products. In the early sixties, Brinex Limited (now Brinco Limited) attempted larger scale commercial exploitation of labradorite, including use 'as building stone and in polished precast concrete for facings on buildings' (Brummer, 1984). After six years of work, which included market studies, Brinex decided that, at that time, the demand did not warrant further production.In recent years, there has been a dramatic increase in the markets for dimension-stone. In the period from 1980 to 1985, the demand in the United States for granite, much of which is imported, has increased 1735070 (Marble Institute of America, 1986). The dimension-stone industry's remarkable growth rate has, in part, resulted from new technology that makes it easier and faster to quarry and cut stone. This has allowed natural storie to compete with other building materials. Now, it is not only used for exterior cladding and walkways, but also on interior walls and floors, and in home and office furnishings, such as countertops for kitchens and bathrooms, table and desk tops, stairways, window sills, and fireplaces."

Jan 1, 1988

By A. G. Matyas, B. Wasmund, R. C. Francki, K. M. Donaldson

"The construction of large. high-power electric furnaces has been an important factor in the growth of electric smelting technology . New developments in the design and operation of electric furnaces have been spurred by the escalating cost of electric power and increasingly stringent environmental constraints. Key areasofprogress include the application of high voltage to enhance furnace productivity; the installation of novel furnace cooling elements and robust binding systems to extend furnace life; development of process schemes to reduce power consumption by preheating and prereduction of the charge; and environmental control improvements for handling fine dusty feedstocks, and for furnace sealing.This paper reviews these developments and outlines a systematic approach for their application in the custom design of new or retrofit electric furnace facilities.IntroductionThe use of electric smelting furnaces has continued to progress during the last decade. Electric furnaces offer high throughput capacity and productivity. In addition, they produce minimum environmental impact, as the furnaces can be readily sealed, and only a small quantity of off-gas is generated. Electric furnaces present the most favourable choice of smelting technology where high process temperatures in excess of about l400°C are required.Their application is burdened by the escalating cost of electric power, hence it is important to seek new opportunities through further technological development. This paper reviews recent developments in the design and operation of high-power electric smelting furnaces, in the following areas:"

Jan 1, 1993

By J. E. Nesset

"As an alternative to conventional dewatering by vacuum filtration and oil-fired rotary dryers, Brunswick Mining conducted extensive pilot-scale testwork on its copper, lead, zinc and bulk concentrates using a Larox Oy (Finland) automatic pressure filter. The results showed that pressure filtration readily produced final cake moistures of 6-8.5 per cent on this very fine sulphide material.An in-depth analysis examines pressure filtration in terms of metallurgical performance and projects energy savings of 78 per cent for pressure filters over the current dewatering operation. Potential energy and operating cost reductions are also estimated.IntroductionVacuum filters followed by oil-fired rotary dryers are one of the most common means of dewatering mineral concentrates. They represent, however, a level of technology which is exceedingly wasteful in terms of manpower, space utilization equipment and fossil fuel dependence. In addition, the use of thermal dryers is leading to increased environmental concerns both in plant and out.These were the primary factors which prompted Brunswick Mining to consider alternative dewatering methods as the existing equipment came up for replacement and upgrading. In late 1979, company engineers were encouraged by automatic Larox pressure filters seen at several Scandinavian operations. Subsequent laboratory tests by the manufacturer (Larox Oy of Finland) on several concentrate samples were sufficiently promising for Brunswick and Noranda to lease a trailer mounted filter-lab unit and a technician from Larox for a five-week period. Extensive on-site testwork on all four Brunswick concentrates (zinc, lead, copper and 'bulk' lead-zinc) confirmed the potential of pressure filtration."

Jan 1, 1982

By M. Sokoto, H. Hata, K. Nishina, K. Haiki

Fluoride ions in zinc electrolyte cause corrosion to aluminum cathode plates at zinc electrowinning process, so we have developed an iron compound as a fluoride ion adsorbent used in zinc sulfate solution. The iron compound is synthesized from FeC13 solution with a small amount of sulfate ion by neutralizing reaction with Na2CO3 solution. The fluoride ions adsorbed on the surface of the iron compound are desorbed in alkaline solution and the iron compound can be reuse as a fluoride ion adsorbent. Moreover, if adsorption capacity of the iron compound decreases, it can be dissolved in HCl solution and re-synthesized.

Jan 1, 2008

By Tim J. Carew, Dennis C. Martin

"One approach to stabilization of rock slopes is to place a buttress at the toe of the slope to provide additional resisting forces and increase the length and strength properties along the failure surface. This paper describes the rock mechanics and mine planning aspects of incorporating a buttress of intact rock in the lower part of the slope as part of the slope design for the south wall of the final pit at Cassiar Mine. Stability analysis techniques and results are described. Analyses results have indicated that, in order to maintain steep over-all slopes in the final pit, a buttress of intact rock shoud be incorporated into the lower section of the slope until late in mine life. The effect of the buttress is to flatten the slope and reduce the slope height thereby improving slope stability. The mining plans would be such that the buttress would be mined out during the last four months of mining when the consequences of instability would be least severe.IntroductionThe concept of using a buttress to stabilize slopes has been used in mining and civil engineering construction in may locations (Richards and Stimpson, 1977). Most buttresses involve placement of coarse rock fill timber cribs or other material as a load at the toe of an already unstable slope to provide forces which resist failure by counteracting driving forces and increasing the length and strength of the failure path.This paper describes the geotechnical and mine planning aspects of incorporating a buttress of intact rock in the design of the south wall of Cassiar Mine. The effect of an intact rock buttress is to flatten the slope and reduce the slope height, thereby improving slope stability. No actual construction is required other than normal excavation of the slope. The ""mine plans would be such that the buttress would be mined out at the end of mine life when the impact of instability would be less severe and additional ore might possibly be recovered from the slopes. Mining of the buttress could induce instability at the very end of mine life at a time when maximum ore extraction has been achieved."

Jan 1, 1986

By V. G. Papangelakis, G. P. Demopoulos

"Recovery of gold from refractory ores and concentrates presently constitutes one of the most important, challenging, and exciting areas of R&D activity in the gold processing industry. New technologies are being tested for the treatment of refractory gold materials, some of which have been advanced to the level of commercial operation. In this paper, some recent technological developments in the hydrometallurgical processing of pyritic matrix-refractory gold ores are highlighted. Key operational steps of each of the alternate hydrometallurgical technologies are analyzed and potential advantages and drawbacks are identified. The processes which are reviewed are: hydro chemical oxidation, biochemical oxidation and pressure oxidation. INTRODUCTIONOver the years the term ""refractory"" has been applied in gold ore processing to denote situations in which straightforward cyanidation failed to yield high gold recoveries. A number of mineralogical and chemical factors may be responsible for this ""refractoriness"" problem. A systematic classification of the different options for their treatment has been discussed in a recent review paper. In this paper, the pretreatment of the submicroscopic gold encapsulated within the matrix of pyrite and arsenopyrite minerals is considered. This type of gold is the ultimate refractory material because complete breakdown by reaction of the host mineral structure is required.The method which has been traditionally applied for the treatment of pyritic-type refractory gold ores is an oxidation roast (single stage or double stage depending on the As content) of a flotation concentrate to produce a porous calcine, the latter being more amenable to cyanidation. Despite its established practice, oxidation roasting is not considered particularly attractive with today's standards for high product recovery and clean environment. Roasting is known to be very sensitive to heating parameters and feed composition and deviation from optimum conditions can result in reduction in permeability which is translated to incomplete gold liberation."

Jan 1, 1989

By Törbjorn Naarttijärvi, Bengt Ludvig, Agne Rustan

"Falling rock is one of the major causes of serious injuries and deaths in Swedish mines. The research at the Division of Mining and Underground Construction was therefore directed toward controlled blasting in hard intense jointed rock.The project was started with an extensive literature review. Model tests with a new equivalent model material have been initiated to find ways of improving blasting techniques. The result showed that long cracks arise at the perimeter holes when there is a long time delay between adjacent holes. This led to the theoretical development of a new initiation method with ultra short delays (1,5 ms) f or controlled blasting, called ""Cutblasting"".Full-scale tests have been done at LKAB in Malmberget in hard intense jointed magnetite ore. Four different types of perimeter charges have been tested, namely: tube charges, ANFO mixed with plastic beads, detonating cord and linear shaped charges. Three types of initiation of the perimeter holes have been used, conventional (half-second delay detonators), instantaneous and ultra short ""cutblasting initiation"" (1,5 ms delay). The change in rock strength before and after blasting has been studied with bore hole periscope, vibration measurement and ocular observation of the rock surfaces.Thefull-scale tests showed that ""cutblasting"" with detonating cord in the perimeter holes gave the smallest damage to the surrounding rock. A combination of cutblasting initiation and tube charges are anticipated to give an even better result. A new method of controlled blasting using linear-shaped charges has also been tested, however, this charge type needs further development.The full- scale test also showed that the damage which can be seen on the rock surf ace is about the same for different controlled blasting methods but the not-visual-damage zone varies as much as from 0,1 to 0,7 m.A new classification system for controlled blasting regarding the damage to the surrounding rock has been devised."

Jan 1, 1985

By W. Blum

Progress made in improving the creep resistance of Mg alloys is reviewed with the emphasis on microstructural interpretation. Experimental results on the increase of creep strain with time at constant stress a measured for limited times and strains are displayed in a transparent form as creep rate-strain diagrams from which the minimum creep rate stress is safely derived. In addition, data on the thermal stress component a derived from high-precision a-reduction tests are reported. Within a simple statistical dislocation model these data allow one to quantify the relation between dislocation velocity v and a . In combination with structure evolution laws this relation serves as a basis for modeling the creep rate. New alloys have distinctly higher creep resistance than AZ91 where precipitation hardening plays a minor role. This is due to hardening by intermetallic phases which may form a continuous skeleton along the grain boundaries (e.g. Ca-alloyed AZ91) and/or submicron-sized precipitates within the grains (MRI230D, Mg-Zn-Ca alloys).

Jan 1, 2006

By J. G. Henning, T. R. Yu, J. E. Croxall

"Test work was carried out to investigate the thermal response of loose and solid rock under varying environmental conditions. The primary interest was to develop a technique that could be used to increase the thermal variation between loose and solid rock for better detectability of loose rock underground with a thermal imaging infrared scanner.A variety of thermal enhancement methods were evaluated both in the laboratory and in the mine environment. Air temperature variation created by the exhaust from diesel driven, mobile mining machinery was studied in detail. When sufficient hot exhaust was supplied to the air, unsteady thermal conditions became more pronounced on the rock surf ace. This allowed a greater percentage of loose rock to be detected by a high-resolution infrared scanner within minutes.The degree of thermal enhancement of loose rock was found to be dependent directly on the thermal conductivity of rock, looseness, air temperature change, and inversely on the size of loose, airflow rate and distance downwind from the heat source. It was also found that an air temperature rise of at least r c, or rock temperature differential of1°C was necessary for minimal thermal enhancement required f or infrared detection."

Jan 1, 1990

By P. Mottahed, E. K. S. Passaris, J. Q. Ran

"The jointed roof of underground mine openings in stratified rock can be analyzed in terms of a voussoir beam. Because of the essential indeterminacy of the structure, previous attempts of theoretically solving the equilibrium equation have been unsuccessful. Numericalanalysisby the finite element method taking the geometrical and joint non-linearity into consideration combined with the experimental method has been adopted to study the performance isopara of the voussoir beam. Deformation and failure mechanism is analyzed in relation to the failure modes. Equations are proposed to estimate the elastic buckling strength and the crushing strength of the voussoir beam and to verify the failure mode of shear sliding. For application of the mechanism of the voussoir beam in mining operations, methods are described to predict the stability of a jointed roof and to design the dimensions of mining openings.IntroductionThe roof stability of an underground mine opening has direct effects on the selection of support methods, opening dimensions and, more importantly, on the safety of mining personnel. The prediction of the roof stability can be of importance in the design of a mining method and in mining operations. The jointed roof of mine openings in stratified rock can be stable under transverse load depending on the roof geometry and properties of the roof material and joints. The stability of this type of roof can be analyzed in terms of a voussoir beam which was introduced by Evans (1941) to study the strength of underground strata. Brady and Brown (1985) analyzed the voussoir beam and suggested that the mechanism of the voussoir beam could be used in the design of underground mine openings in stratified rock instead of the traditional continuous beam theory."

Jan 1, 1993

By Robert M. Hopkins, Craig C. Monahan

A corrosion survey was performed on ten selected H-piles which support a reinforced concrete wharf located at Trepassey, Newfoundland. Approximately 900 thickness measurements were taken at twelve different locations in each off our zones on the steel piles: the splash (atmospheric) zone, the intertidal zone, the low tide zone and the submerged zone. Results show that over the 2o-year life of the wharf, corrosion has been most severe in the splash, low tide and submerged zones with average corrosion rates for the flanges of 6.95, 9.45 and 6.86 mils per year (mpy}, respectively, and average corrosion rates for the webs of 5.13, 4.12 and 3.45 mpy, respectively. Minimal attack was found in the intertidal zone where the average corrosion rate was only 1.66 mpy on the flanges and 1.37 mpy on the webs. Such a pattern of attack is frequently observed f or steel piles partly submerged in seawater. The abnormally low corrosion rate associated with the intertidal zone is generally explained as being due to cathodic protection induced by the high corrosion rate in the adjacent low tide zone. Analysis of the corrosion data obtained for the Trepassey wharf would suggest that this explanation might be incorrect. An alternate hypothesis has been brought forward which better accounts for the extremely low corrosion rate observed in the intertidal zones of these piles.

Jan 1, 1990