Search Documents

By A. T. Jakubick, A. MacG. Robertson

This paper reviews key issues related to the placement of dry (soil) covers on extremely weak, compressible fine tailings. The design and construction of soil covers on such tailings often presents a formidable challenge to the geotechnical as well as the environmental engineer due to the low shear strength, poor traffic ability, and high settlement of under consolidated tailings at the time of reclamation. The geotechnical issues to be considered include: (1) consolidation of near-surface tailings to achieve strength gains, improve traffic ability, and allow safe placement of initial cover layer; (2) stability of tailings slopes during dewatering of tailings ponds and/or cover placement; and (3) long-term settlement of tailings and its impact on cover integrity and final surface shaping. The environmental issues to be considered include: (1) management of contaminated (free) pond water; (2) management of contaminated pore water expelled during tailings consolidation; and (3) management of (uncontaminated) surface water on top of the cover. This paper summarizes recent experiences gained in a large uranium tailings reclamation project. It is concluded that a careful consideration of both geotechnical and environmental issues during the planning stages greatly reduces the costs and environmental risks associated with fine tailings reclamation.

Jan 1, 2000

By A. E. Kurie

The Great Salt Lake occupies about 1000 square miles whereas its predecessor, Lake Bonneville occupied 20,000 square miles and its shoreline reached 1000 feet above the present lake level. The sediments of Lake Bonneville range from peripheral gravel and sand deposits to central basin calcareous clays and silts, gypsum sands, and saline precipitates. The drilling and engineering tests conducted by the Utah State Department of Highways for many highway structure sites and the construction of Federal Interstate freeway provided engineering and hydrologic properties of Lake Bonneville sediments. Ground water and surface brine exploitation have contributed hydrologic and chemical data; the geologic and mineralogical data are scientific research contributions.

Jan 1, 1967

By Y. Luo

Cuando se diseña y operan minas de carbón subterráneas con el método de cámaras y pilares, es siempre difícil obtener un buen equilibrio entre la prevención de subsidencia de la superficie y la obtención de un alto coeficiente de recuperación. En este trabajo se propone una metodología de diseño aplicando la teoría de arco de presión y se detallan los principios y modelos matemáticos involucrados. Se desarrolló un programa de computadora a fin de realizar el proceso de optimización del diseño y fue aplicado a la examinación de un caso documentado en el que había sucedido una falla masiva de un pilar en cascada sobre un área grande en una mina de carbón poco profunda. Los resultados indican que el método de diseño propuesto puede ser aplicado para prevenir la subsidencia y a la vez obtener un alto coeficiente de recuperación para operaciones mineras de cámara y pilares.

Jan 1, 2014

By Y. Luo

In designing and operating underground room-and-pillar coal mines, it is always difficult to achieve a good balance between preventing surface subsidence and achieving high recovery ratio. In this paper, a design methodology applying the pressure arch theory is proposed, and the principles and mathematical models involved are detailed. A computer program was developed to carry out the design optimization process and was applied to the examination of a documented case in which a massive cascading pillar failure had occurred over a large area in a shallow coal mine. The results indicate that the proposed design method can be applied to prevent subsidence while achieving reasonably high recovery ratio for roomand- pillar mining operations.

Jan 1, 2014

By H. H. Schrenk

One phase of Bureau of Mines work in health and safety is promotion of the use of safe, satisfactory, and reliable respiratory protective devices. To insure that such devices will be. available, the Bureau has established schedules of minimum requirements for oxygen breathing apparatus,3/ gas masks,/ supplied-air respirators (hose masks, air-line, respirators, and abrasive blasting helmets, hoods, or masks),5/ and dispersoid (dust, fume, and mist)

Jan 1, 1943

By Emerson F. Heald

A systematic study was made of new and old data on chemical activities in Fe-Pt alloys at elevated ternperatuves. Experimental results may be expressed in terms of the excess free energy using Least-squares analysis of the data gave the following values for the constants: for the temperature range 1130° to 1350°C, and tentatively to 155O°C, B = -3.326564 and C = 0.221051; for the temperature range 650" to 850°C, B = -2.555690, C = 1.762735, and D =0.097196. In the study of iron-containing silicate systems, it is sometimes desirable to have a direct experimental measure of the activity of iron in the system. The well-known solubility of iron in platinum, often a headache in experimental work on iron compounds under reducing conditions, can be used to advantage in this respect. If the activity of iron in an Fe-Pt alloy in equilibrium with the silicate is known as a function of the composition of the alloy, chemical analysis of the alloy will give a knowledge of the activity of iron in all of the phases in the system. The present study was undertaken in order to elucidate the characteristics of Fe-Pt alloys as iron activity indicators. This work is intended to tie together some previous work, which may be summarized as follows. Larson and Chipman1 determined the activity of iron in Fe-Pt alloys at 1550°C by equilibrating platinum metal with calcium oxide-iron oxide-silica melts of known iron activity. Compositions of the resulting alloys were determined by chemical analysis. A similar study was carried out by Taylor and ~uan,' who worked at 1300°C. They brought the Fe-Pt alloys into equilibrium with iron oxide under conditions of known partial pressure of oxygen, and thus, from the work of Darken and ~urr~,~ conditions of known iron activity. Compositions were determined indirectly, by following the change in weight of the sample. Sundaresen et el* used the electromotive force of cells in which the alloy formed one electrode in order to measure the activity of iron in the alloy at 650" and 850°C. These temperatures were chosen to be above and below the first-order phase transition which takes place upon the ordering of Fe3Pt and the second-order transition which occurs upon the ordering of FePt3. EXPERIMENTAL 1) High Temperatures. The starting materials used were thin platinum foil, about 0.002 mm thick, and Fisher Certified reagent ferric oxide, Fez03, which had been heated for 24 hr at 1000°C. An intimate mixture of 80-mesh Fez03 and platinum platelets was placed in a thin platinum foil envelope. The latter was suspended from thin platinum wires in the hot zone of a vertical-tube, platinum-wound furnace of the type described by Muan and ~sborn.~ A capillary gas mixer similar to that used by Darken and Gurry3 was used to prepare a precisely known mixture of carbon dioxide and hydrogen, which was allowed to flow upward through the furnace tube. The partial pressure of oxygen in contact with the sample was thereby fixed at a value which was calculated from the charts prepared by porter? Temperatures were measured with a Pt-10 pct Rh-in-platinum thermocouple, which was calibrated using the melting points of gold (1062 .@C) and diopside, CaMgSizOB (1391.5"C). Temperature control was maintained to within i3"C with a Geophysical Laboratory proportional controller, using the furnace resistance as the sensing element. Samples were quenched by passing a small current through the platinum suspension wires, allowing the sample to drop into a bath of dibutyl phthalate at the bottom of the furnace tube. Prior to chemical analysis the samples were washed with acetone and dried. 2) Chemical Analysis. It proved possible, in almost all cases, to separate the Pt-Fe platelets physically from particles of iron oxide. The platelets were dissolved in a small volume of aqua regia, evaporated to dryness, and redissolved to 0.1 M HC1. In order to determine iron in the platinum alloy potentiometrically, it is necessary first to remove the platinum. A 10-cm column of Amberlite IR-120 cation exchange resin in the hydrogen form provided separation quickly and quantitatively: The mixture of iron and platinum in 0.1 M HC1 was added to the top of the column, and washed with about 100 ml of 0.1 M HC1. Under these conditions, the iron, principally in the form of cations such as FeC1" and FeCl;, is held quantitatively in the uppermost centimeter of the column. The platinum, in the form of anions such as PtC&- , is washed through without being adsorbed. After a qualitative test with stannous chloride indicated all of the platinum was removed, the iron was

Jan 1, 1968

By N. E. Rogen, N. J. Grant

AGE-hardening in nickel-chromium-titanium-aluminum alloys in the composition range characterized by the Nimonic alloys, is dependent upon the precipitation of the Ni3(AI,Ti) (y') phase.1 This phase is found to precipitate at about 700°C.1 Ni,Al is a face-centered-cubic ordered structure with a lattice parameter of 3.560 A. The atomic configuration is such that the aluminum atoms occupy the cube corners and nickel occupies the cube faces with titanium substituting for the aluminum preferentially. A maximum of three out of every five aluminum atoms can be replaced by titanium atoms in the -y 'phase.' When the solubility of the y'-phase is exceeded for titanium the T(Ni,Ti) phase is formed. The T-phase is an ordered close-packed hexagonal intermetallic structure which shows little solubility for the other elements in these alloys. The lattice parameter for T-phase is a - 2.5454 kr and c = 8.2900 kx units."

Jan 1, 1959

By T. I. . I. Sibbald, D. E. Jiricka

The Goldfields area on the north shore of Lake Athabasca , was active in the thirties and early fortie . In 1934, Tom Box discovered gold mineralization in quartz veins in pyritized 'granite' at the ite of what wa to become the Box Mine of the Consolidated Mining and Smelting Company of Canada Ltd . In the rush of activity that followed numerou other gold occurrences were found. the most significant of the e being the Athona and Frontier prospects which underwent underground development bur did not reach production. Probable reserve identified to date in the Box and Athona deposits amount to some 3.5 million ton grading an average 0.ITT oz gold/ton . Some 10 to 15 million tons of lower grade, po ible reserve are also reported at the Box. From 1939 to 1942, the mine produced, from underground , 64,066 ounces of gold from ore grading 0.0452 oz gold/ton at a cost of between $1.5 and $2.0 a ton. The Goldfield area is underlain by upracrustal rock intruded by mafic bodies and invaded by ·granite'. The upracru tal . thought to be of Lower Proterozoic age are characterized by a helf-type ucce ion metamorpho ed under lowermiddle amphibolire facie conditions into quartzites, quartz-mica chi ts. dolomitic marbles, diop idic calc-silicates and cordierite-anthophyllite-biotite schi t . Amphibolites of presumed igneou origin form concordant to subconcordant units up to a few ten of metre thick in the upracrustals and occur as le regular masses in the 'g ranite·. Compositionally they vary from gabbroic to granodioritic. with the more mafic varieties being most common. Granitic rocks exhibiting a variety of textural , structural and compositional characteristics underlie most of the area. Four main units are recognized: foliated (older) 'granite', 'leucogranite', feldspar augen 'granite· and pyritic mine 'granite', however, in geological mapping the e are somewhat arbitrarily differentiated due to transitional relationships and admixture of types. Although there is no unambiguous age data available for the e 'granite ' adjacent northshore 'granite' of geologically similar age yield Rb-Sr isochron dates around 2000 Ma. The area is characterized by two major deformation events of which the earliest gave rise to the dominant regional foliation and to rare minor and outcrop scale folds. This foliation which in general parallels compositional layering is folded into the major Goldfields syncline, whose axis plunges weakly to moderately outh. Related open minor folds have subvertical axial surfaces which are locally paralleled by a weakly defined schistosity. Most rock display a pronounced rodding fabric, coaxial with second fold axes and apparently the product of this deformation event. However, a note of caution is introduced into this interpretation, as the rodding fabric is also parallel to first fold axe .

Jan 1, 1986

By Shigeru Tsutsumi

The rapid development of transportation facilities in Japan focused the attention of this country on the possibility of converting the existing coal resources (of which there was an abundance) into liquid fuels, for which there was a constantly increasing demand. Previous work had indicated that this could be accomplished by utilizing one of two processes - the Bergius process, in which high temperatures and high pressures were employed to effect direct liquefaction of the coal, and the Fischer-Tropsch process, in which an indirect liquefaction of coal was accomplished by the production of liquid hydro-carbons from hydrogen-carbon monoxide mixtures. This report describes some investigations into the latter process, which was first developed by Fischer and his colleagues in the Coal Laboratory in Muhlheim, Germany, in 1923. By 1932, these investigators had achieved a 60-percent theoretical yield (152 ml. of liquid hydrocarbons per cubic meter of 2H2:ICO synthesis gas) by using a precipitated Co-Th02 catalyst.3/ At the same time (1932), Dr. Kita of Kyoto Imperial University and Messrs. Fujimura and Tsuneoka obtained 145 ml. of gasoline (C5+) per cubic meter of synthetic gas by using a Co-Cu-Th-U catalyst. 4/ This report is a description of the experimental results subsequently obtained at the Fuel Research Institute, Kawaguchi City, Saitama, up to 1935.

Jan 1, 1951

By Michael R. Norland

This U.S. Bureau of Mines report on U.S. and Canadian 1iterature pertaining to soil characterization and the use of soil amendments as a part of the reclamation process of coal surface-mined lands contains 1,280 references. The references were published during the 1977 to 1988 period. Each reference is evaluated by keywords, providing the reader with a means of rapidly sorting through the references to locate those articles with the coal mining region and subjects of interest. All references are annotated.

Jan 1, 1991

By Hakan Uyguçgil, Beril Bayraktar, Adnan Konuk

Mining is one of the industries with the highest risk of occupational accidents in Turkey and globally. The most important feature that distinguishes the mining industry from other sectors is the constantly changing working conditions. The risk of accidents is very high, especially in underground mining, and can happen for several reasons. Therefore, it is essential to carry out all necessary measures in coordination with other disciplines to adapt to changing workplace conditions. The dangers that might occur underground must be determined in advance, controlled at their source, or eliminated since it is critical to take the necessary precautions before the accident. Accident prevention will protect miners’ living conditions by contributing to the country’s economy through reduced labour and production losses. In this research, the data from 13,653 accidents reported in the Karadon Hard Coal Enterprise between 2000 and 2011 were analysed and compared using the Life Table and the Kaplan-Meier methods. Accident records were classified and analysed into four categories: environmentalrelated accidents, equipment-related accidents, person-related accidents, and other accidents. Findings in terms of survival time indicate that environment-related and person-related accidents had the highest risk in Karadon, with equipment-related accidents having the lowest. This study established the reliability of using survival analysis methods to investigate occupational accidents in the mining sector. Given that environment-related and person-related accidents occur in a relatively short period, such as 1 year after starting work, it has been recommended that research be done to improve workplace and occupational safety measures and broaden the training given to miners. Additionally, it has been determined that increasing the use of automation and mechanisation in underground coal mines, combined with developing a thorough equipment safety training programme to raise awareness of the danger, can help prevent person-related occupational accidents caused by the interaction between equipment.

Aug 5, 2023

By Yu. A. Polozov, V. A. Lagunov, O. Yu. Lushinkova, Yu. I. Svirskiy, Eh. Ya. Kipko, Roy A. Williams

4.1 THE GENERAL COMPOSITION AND PROPERTIES OF CLAY-BASED GROUTS Clay-based grouts are visco-plastic systems; they are made by adding structure-forming reagents to a clay mineral mortar. Small amounts of cement and various chemical ad¬ditives constitute the reagents. If necessary, fillers also are added. The distinguishing feature of clay-based grouts is that throughout their entire stabilization period they do not form a crystallized structure as does cement grout. The structure of stabilized clay-based grouts does not deteriorate during minor rock movement or upon the initiation of blast¬ing during the construction of a shaft or a drift. Because they can possess good rheological properties during the ini¬tial structure-forming period relative to cement grouts, clay¬based grouts are not easily eroded from large fractures and karstic cavities by flowing ground water. In addition, their finely dispersed clay particles facilitate a greater fracture penetration capacity, especially in dual porosity rocks. Numerous investigations of the structural-mechanical and rheological properties of clay-based grouts by STG have demonstrated that the most effective grouts for pre¬venting the inflow of ground water into underground work¬ings are grouts that have a cement content of 8 to 10% (90 to 120 kg/m3) of the clay grout by mass. The grout should have a density of 1.18 to 1.30 T/m3. Various additional substances and chemicals can be added as additional fillers and structure-forming reagents. In pure ground water at temperatures above freezing, sodium silicate in the amount of 0.8 to 1 % by mass normally is the only structure-forming reagent that is necessary if the proper clay is selected and if it is available. The production process for making clay-based grout is divided into two stages: 1) the production of an initial clay mortar with specified properties and 2) the production of a clay-cement additive grout mixture using the initial grout along with the structure-forming reagents, including the ce¬ment. The properties of clay-based grouts depend on the phys¬ical-mechanical properties of the initial clay mineral, the properties of the cement and the properties of the chemical reagents that are added. 4.1.1 TECHNOLOGICAL PROPERTIES OF CLAY-BASED GROUTS The dynamic shear stress' To, the viscosity 11, the static shear stress2 0, the maximum shear stress of the structured that the rheological and structural-mechanical prop¬erties of clay-based grouts must fall within the following limits: the dynamic shear stress To = 50 to 200 Pa; the viscosity -9 = 0.02 to 0.07 Pa sec; the static shear stress 0 = 150 to 600 Pa; the plasticity strength Pm of the structure one minute after preparation (according to P.A. Rebinder's method) equals 150 to 500 Pa. The plasticity strength 10 days after preparation is ? 0.15 MPa. The general relationship of the change in the structural strength of clay-based grouts relative to stabilization time is shown in Fig. 32. The figure shows that the structure-form¬ing process for clay-based grouts is characterized by three stages. These stages correspond to the time periods required for conducting the principal operations during the injection of the grout into a fractured aquifer as described below. Stage I, corresponding to the time period T1, reflects the small development of structural strength during early stabi¬lization. During this time, the structural strength must not preclude the capability to pump the grout. The time Tl must correspond to the length of pumping time from the moment water is shut off and mixing occurs until the pump stops forcing the grout through the manifold block and pipeline into the fractured rock as described subsequently herein. Stage II, corresponding to the time interval T2, reflects a sharp but controllable increase in the structural strength of the grout. The length of time period T2 is controlled by the addition of appropriate reagents. Stage III produces the final value of the structural strength. This final strength is used to design the dimensions of the isolation curtain. Consequently, the development of grouts is guided by two principal criteria: 1) the grout must develop the highest possible structural-mechanical properties and 2) it must be able to be pumped by a piston pump prior to final stabili¬zation. Successful grouting depends to a large extent on the correct design of a grout for each specific case. It is impor-

Jan 1, 1993

By B. B. Wood, M. J. Rzasa, E. W. Hough

An apparatus for the determination of fluid-fluid interfacial tension by the pendant drop method has been constructed. The apparatus is refined beyond those previously described in that the samples are introduced into an evacuated windowed cell without contacting air or mercury. Interfacial tension data are reported for the water-methane system between 74 and 280°F and 15 and 15,000 psi. The variation of wettability of the stainless-steel dropper tip with pressure and temperature was observed incidentally to the measurements. INTRODUCTION The most refined previous apparatus --for the determination of fluid-fluid interfacial tension at reservoir conditions was built by Hauser and Michaels.' These authors used the pendant drop method, previously investigated by Andreas, Hauser, and Tucker.' Recently, Fordham3 has made the pendant drop method an absolute one by numerical integration of the differential equation of drop shape. It is necessary to know the difference in density of the two fluids and the acceleration due to gravity in order to evaluate the interfacial tension from measurements of drop dimensions. Contact angle is not involved in the measurements by this method. Some precise tests of the method have been made at atmospheric pressure and 77°F by Douglas," who found agreement with established values to within about 0.1 per cent for water and air, cyclohexane and air, benzene and air, and benzene and water. No values of interfacial tension from the recent pendant drop apparatusJ have been published by Hauser and Michaels. However, values for the water-benzene and water-decane systems are given in Michaels' thesis5 or Dressures from 15 .to 10,000 psi and temperatures from 73 to 268ºF. Some determinations on gas-oil and gas-water systems in the range of 15 to 4,000 psi and 78 to 178°F have been made by Hozott,' by the drop-volume method. The capillary rise method has been used to investigate the interfacial tension in gas-oil systems at 88°F to several thousand psi by Swartz.7 Other determinations in gas-oil systems at pressures under 1,000 psia have been made by Jones: and Beecher and Parkhurst.9 The scarcity of data for pressures above 5.000 psi is apparent. APPARATUS An assembly drawing of the working section of the interfacial tenqion apparatus is given in Fig. 2. 'The endanant drop (A) is housed in a pressure chamber having glass windows (B). An agitator (6) is provided. The metal parts of the apparatus coming into contact with the sample are made of AISI: Type 316 steel. Drain grooves are provided around the whdows so that the sample in contact with the O-rings is not returned to the working section when the pressure is reduced. A schematic arrangement of the apparatus is given in Fig. 3. The working section containing the pendant drop (A) is filled by samples from bombs (B) with the aid of the vacuum system (C). The O-ring sealed pistons (D) used to separate the sample from the hydraulic fluid are shown together with the pressure production and measurement system (E). A front view of the apparatus is shown in Fig. 1. Most of the hydraulic system is at the top of the panel. The pump and displacement piston are at the lower right. The Variacs for the air bath heaters. the camera. and the vacuum gauge are a1so visible on the panel. The working section together with a window closure and a drop-forming tip closure are shown in Fig. 9. The carbon arc light source with filter is visible in the upper part of the picture. Two sides of the air bath with the impeller and a part of the convection shield can also be seen. The assembled air bath is shown in Fig. 10.

Jan 1, 1951

By E. W. Hough, B. B. Wood, M. J. Rzasa

An apparatus for the determination of fluid-fluid interfacial tension by the pendant drop method has been constructed. The apparatus is refined beyond those previously described in that the samples are introduced into an evacuated windowed cell without contacting air or mercury. Interfacial tension data are reported for the water-methane system between 74 and 280°F and 15 and 15,000 psi. The variation of wettability of the stainless-steel dropper tip with pressure and temperature was observed incidentally to the measurements. INTRODUCTION The most refined previous apparatus --for the determination of fluid-fluid interfacial tension at reservoir conditions was built by Hauser and Michaels.' These authors used the pendant drop method, previously investigated by Andreas, Hauser, and Tucker.' Recently, Fordham3 has made the pendant drop method an absolute one by numerical integration of the differential equation of drop shape. It is necessary to know the difference in density of the two fluids and the acceleration due to gravity in order to evaluate the interfacial tension from measurements of drop dimensions. Contact angle is not involved in the measurements by this method. Some precise tests of the method have been made at atmospheric pressure and 77°F by Douglas," who found agreement with established values to within about 0.1 per cent for water and air, cyclohexane and air, benzene and air, and benzene and water. No values of interfacial tension from the recent pendant drop apparatusJ have been published by Hauser and Michaels. However, values for the water-benzene and water-decane systems are given in Michaels' thesis5 or Dressures from 15 .to 10,000 psi and temperatures from 73 to 268ºF. Some determinations on gas-oil and gas-water systems in the range of 15 to 4,000 psi and 78 to 178°F have been made by Hozott,' by the drop-volume method. The capillary rise method has been used to investigate the interfacial tension in gas-oil systems at 88°F to several thousand psi by Swartz.7 Other determinations in gas-oil systems at pressures under 1,000 psia have been made by Jones: and Beecher and Parkhurst.9 The scarcity of data for pressures above 5.000 psi is apparent. APPARATUS An assembly drawing of the working section of the interfacial tenqion apparatus is given in Fig. 2. 'The endanant drop (A) is housed in a pressure chamber having glass windows (B). An agitator (6) is provided. The metal parts of the apparatus coming into contact with the sample are made of AISI: Type 316 steel. Drain grooves are provided around the whdows so that the sample in contact with the O-rings is not returned to the working section when the pressure is reduced. A schematic arrangement of the apparatus is given in Fig. 3. The working section containing the pendant drop (A) is filled by samples from bombs (B) with the aid of the vacuum system (C). The O-ring sealed pistons (D) used to separate the sample from the hydraulic fluid are shown together with the pressure production and measurement system (E). A front view of the apparatus is shown in Fig. 1. Most of the hydraulic system is at the top of the panel. The pump and displacement piston are at the lower right. The Variacs for the air bath heaters. the camera. and the vacuum gauge are a1so visible on the panel. The working section together with a window closure and a drop-forming tip closure are shown in Fig. 9. The carbon arc light source with filter is visible in the upper part of the picture. Two sides of the air bath with the impeller and a part of the convection shield can also be seen. The assembled air bath is shown in Fig. 10.

Jan 1, 1951

By John Hanna

Over the years the coal industry in Alabama has generated about 150 million tons of fine waste coal, increasing at a rate of 2 million tons/year, during mining and cleaning operations. Reclamation of the fine-size wastes containing 20-60% by weight clean coal provides, free of charge, mined and crushed feedstocks for coal recovery and eliminates a major source of acid water pollution. Tests were made on the impounded wastes and current plant discharges to recover the coal fraction by sizing, gravity and flotation techniques. Gravity separation of the plus 100 mesh material produced commercial grade coal averaging 8.2% ash, 0.8% sulfur and 13,350 Btu/lb. However, the coal recovery was relatively low at 50-65%. Froth flotation using mechanical and froth column methods gave similar coal products at much higher coal recovery of 87-93%. The coal produced analyzed 10% ash and 1.1% sulfur.

Jan 1, 1991

By T. R. C. Aston, C. M. K. Yuen, J. L. Gilby

"The access tunnels for the Donkin-Morien Mine in Cape Breton, Nova Scotia, comprise two parallel tunnels driven through a sedimentary sequence of sandstone, siltstone and mudstone to intersect the Harbour Coal Seam under the Atlantic Ocean, approximately 3.5 km offshore (Fig. 1). The No. 2 tunnel was driven a total distance of 3579 m using a 7.6 m diameter Loyat full-face tunnel boring machine (TBM) and was supported by steel sets. The No. 3 tunnel was initially driven a distance of 1027 m using drill and blast methods (dimensions 7.6 m wide by 5.3 m high) supported by rock bolts and shotcrete. This tunnel was then completed (front March 1986 to February 1987) using the tunnel boring machine to a distance of 3573 m.During the period May 1983 to December 1984, a major geotechnical research program was undertaken in the Donkin-Morien tunnels by Golder Associates in conjunction w,ith CANMET and the Cape Breton Development Corporation (Yuen et al., 1985). The research program included the monitoring of the performance of the TBM and drill and blast drivages, and the study of the thrusting characteristics and rock-interaction of the TBM excavation. The main emphasis of the research program was on the collection of field data which was to be made available in the form of a comprehensive report for the future use of others who might wish to carry out a detailed interpretation and analysis. The information gained from the program was also used during the tunnel"

Jan 1, 1988

By John D. Smith, Robert J. Mitchell

"There is a world-wide trend toward underground bulk mining methods employing hydraulically placed backfill. This trend is recent and therefore there is little in the literature to assist an operator in the design of backfill properties, the design of drainage facilities, the calculation of the operating forces on a bulkhead, and the control procedures considered necessary before, during and after pouring. This paper presents recommended procedures that are based on over to years of experience in the various aspects of backfilling large openings. Free-draining timber or concrete block bulkheads are shown to be a viable alternative to massive reinforced concrete bulkheads for the containment of backfill pours. Hydrostatic pressures cannot develop in backfills provided adquate drainage facilities are installed.IntroductionThe increasingly adverse relationship between mining costs and mineral values has led mining companies to develop more productive, lower-cost, bulk mining methods. This has led to the increasing use of large, more or less continuous, hydraulically placed backfill pours to enable the recovery of a higher proportion of pillar ore. The success of any bulk mining method depends on the degree of stability maintained during the stoping operations with reference to the mining rate, the performance of the backfill with respect to the per cent extraction of pillar ore, and the control of the mine structure with respect to safety and productivity. One such method has been previously described(I) where a steeply dipping orebody is being mined with a sub-level method that employs large, hydraulically placed tailings pours for delayed pillar recovery. The paper describes the rock mechanics analysis undertaken to establish the stope and pillar geometry and the approach taken to establish backfill strength requirements to prevent dilution during pillar recovery. Production with this method started in 1970 and because few, if any, large bulk pours had previously been used in- this way (judging by the lack of information in the literature), design data and criteria were needed for several aspects of the work. Methods to establish backfill quantities and pertinent ""in-place"" fill properties are described in 2, 3 and 4 in the list of references. Results of field measurements taken to establish fill pressures for bulkhead design purposes are described in 5 and 6. Laboratory large-scale model tests undertaken to confirm a fill strength design equation, which takes into account fill arching, have recently been completed. A paper describing these tests and the results will be forthcoming in the near future."

Jan 1, 1982

By J. Huisman

With the introduction of ever-stricter environmental operating guidelines, capital expenditure restrictions and operational budget cutbacks, the biological method of SO2 removal becomes more and more attractive. Biological treatment of dilute flue gases is a more cost effective technology in comparison to conventional sodium hydroxide scrubbing. Although the investment costs for sodium hydroxide scrubbing is lower, the operational costs are significantly higher. In addition, the end product of the biological installation is sulfur instead of sodium sulfate; and no further wastewater treatment of the bleed from the biological installation is required since heavy metals are removed simultaneously. Another option for the treatment of SO2 containing gas at a sulfuric acid plant is the production of extra sulfuric acid of the discharged SO2 by applying an additional converter. Comparing biological treatment with this option shows much lower investment costs for the biological installation. Sulfur is produced which can be converted to sulfuric acid, so the bio-route will be more cost-effective than an additional converter. In principle, the biotechnological gas cleaning system is an integration of an absorber with a wastewater treatment facility. In the absorber, the SO2 containing gas is brought into contact with the washing water. The effluent absorber liquid contains a mixture of sulfite and sulfate that is converted into elemental sulfur. This conversion takes place in an integrated system; first, the sulfite/sulfate mixture is converted anaerobically into sulfide; secondly, the sulfide is converted aerobically into elemental sulfur. Subsequently the sulfur is separated and the water is returned to the absorber. Due to the buffer capacity of the washing water, removal efficiencies over 98% are possible. In addition to SO2 removal, it is possible to convert for example other bleeds streams such as scrubber acid or weak acid to sulfur in the same SO2 installation. Recent evaluations concluded that biological desulphurization of flue gases is not only economically attractive in comparison to convention sodium hydroxide scrubbing but also in comparison to gypsum producing systems and even seawater scrubbers. This paper describes the technological and economical viability of biological flue gas desulphurization.

Jan 1, 2005

By L. D. Boughton

Solution mining projects are conducted through one or more boreholes which penetrate en ore body. Proper drilling, completion and maintenance of the boreholes, therefore, is essential to the success of any solution mining operation. Wells drilled for solution mining encounter problems quite similar to problems encountered by the petroleum industry in drilling, completing and maintaining wells for the production of oil, gas or water. Many of the services developed and much of the experience gained by the petroleum industry is applicable to solution mining wells. As in the petroleum industry, each individual wellbore and ore body in a solution mining project provides its own problems. These vary greatly from well to well, and it is not possible to set down data or outline programs that will apply to all wells. Instead, the design of the drilling, completion, production and maintenance programs should be worked out for each individual well. The purpose of this paper, then, is to generally describe materials, equipment and techniques available for these programs and to discuss the purpose and sequence of their use.

Jan 1, 1971

By Edward Saibel

The various theories that have been advanced to explain or predict the conditions under which a metal fractures may be divided into two categories: First, there are the macroscopic theories generally used in engineering practice. These are empirical in nature and limited in application. For example, the maximum normal stress criterion, which is quite satisfactory for a mild steel in simple tension at atmospheric pressure,' no longer suffices when this steel is pulled under hydrostatic pressure.2 In all of these empirical theories, the critical condition characteristic of the material and of the loading conditions must be obtained experimentally. Secondly, there are the theories based on interatomic forces,3'4 or on the energy required to form new surfaces.5,6 These have all dealt with the theoretical evaluation of the tensile stress necessary to bring about rupture in a purely brittle manner; that is, without plastic flow preceding fracture. All of these attempts have led to values of the tensile strength of crystals or of polycrystalline bodies that are 100 to 1000 times higher than observed values. On this account, it has been thought necessary by some investigators to conceive of a microcrack structure or distribution of flaws throughout the specimen such that the resulting stress concentrations provide the factor necessary to bring about agree- ment between calculation and experiment. It has been pointed out by several observers' that this point of view is highly unrealistic, in that the weakening effect of these flaws or microstructures must be very uniform from specimen to specimen, since the fracture stresses found for various specimens of the same material tested under similar conditions are so nearly constant. Furthermore, since calculations based on atomic forces or atomic energy are for purely brittle fracture, a condition probably never satisfied in tests, agreement is hardly to be expected. Thermodynamic Theory of Fürth In order to resolve this apparent discrepancy between the theoretical cohesive strengths and the observed fracture strengths, Fürth8 advanced a thermodynamic theory of the tensile strength of isotropic bodies based on work of Born relating to the melting of crystals. Assuming an isotropic material free from imperfections and flaws, behaving elastically up to the breaking point, and assuming a connection between rupture and the melting phenomenon, Fürth obtains an expression for the rupture stress a, in the form where Q is the melting energy per unit mass, p is the density, and is Poisson's ratio. Furth compares fracture stresses computed from Eq I with the fracture stresses of metals as given in the Landolt-Bernstein Tables (1927) and in the Hand-

Jan 1, 1947