Search Documents

By H. Akgun, J. J. K. Daemen

Design of plugs for abandonment of boreholes and shafts may be governed by the bond strength between the plug and host rock. Presented in this paper are the results of push-out tests on two types of expansive cement grout plugs emplaced in rock salt. The average interface shear strengths range from 2 to 12 MPa. Peak shear stresses (assuming an elastic stress distribution along the interface) are up to eight times higher. Dissolution along the interface may be enhanced by clay inclusions in the salt and appears to reduce bond strengths. Application of the results to the design of plugs for larger openings (e.g., shafts, drifts, or boreholes) is discussed.

Jan 1, 1995

By W. W. Roepke, B. D. Hanson

A major problem facing the coal mining industry today is the need to meet more stringent dust standards due to quartz. When secondary suppress ion is not adequate, the time-consuming and costly cut-and-try method of modifying the mining machine is used in the hope that it will reduce dust generation. The Coal Cutting Technology Group, at the Bureau of Mines' Twin Cities Research Center, has developed an inter-active computer program for drum- type cutting systems to help identify, in advance, modifications that offer the best potential for reducing dust. The program, Relative Dustiness Indicator (REDI), evaluates machine dimensions, seam characteristics, and operator-controllable variables for dust generaton, energy, forces, and product ion.

Jan 1, 1986

By R. Lai

This paper describes the application of a cyclonic flotation column (CFC) for coal cleaning. A CFC makes use of centrifugal force to create a density gradient in a column to augment the froth flotation process. In a CFC, a series of angular helical inserts is attached to the wall of a conventional column, and coal slurry is mixed with a series of impellers attached to a central shaft. The hydrophobic froth concentrates near the center shaft and moves upward, while the relatively heavy hydrophilic particles concentrate near the wall and are guided downward by the helical inserts. The results of pyritic sulfur removal from an Upper Freeport coal during CFC flotation are discussed.

Jan 1, 2003

By R. L. Grayson

Based on the relationships between severity measure vs. productivity and other factors, this paper presents a comprehensive analysis of US underground coal mine injuries in 1996 by mine size. From the 1996 data, it was concluded that, generally, the larger the mine, the more productive it is (in tons per employee-hour) but the more severe is its injury experience (r = 0.65). However, within very large, large and medium mines, the more productive the mine, the less severe is its injury experience (r = -0.43, - 0.36 and -0.26, respectively). For small and very small mines, a deeply nested analysis would be required to understand relationships. Other interesting relationships and comparisons are presented.

Jan 1, 2002

By R. B. Inturi, R. G. Reddy

Solid-state reduction of roast Movat chromite ore with carbon was carried out as a function of the C/FeO ratio at temperatures ranging from 800°C to 900°C. The reduction was studied using thermogravimetric analysis (TGA). A two¬stage mechanism consisting of the reduction of FeO with carbon monoxide and the regeneration of CO by the oxida¬tion of carbon with CO2 was proposed. The rate-controlling step is the carbon oxidation reaction. A kinetic equation, that of random nucleation, was proposed. The activation energy for the reduction was determined to be 55,800 J/mole and is compared to those activation energies determined for other chromite ores.

Jan 1, 2000

By M. S. Celik, G. Onal, S. Atak

The beneficiation of boron minerals flotation with well defined systems has been only slightly, investigated in the literature. The difficulty arises from fact that boron minerals cover a spectrum of solubilities. Colemanite (a calcium-containing, relatively insoluble, boron mineral) and borax (a highly soluble boron mine, have been used to exemplify the flotation of boron minerals. Using sodium dodecylsulfonate (SDS) and dodecylamine hydrochloride (DAH), the floatability responses of these boron minerals are considerably different. This has been ascribed to variations in the solubilities of boron minerals and the presence of cations in the lattice structure. In study, flotation tests and zeta potential measurements used to determine the flotation mechanisms of boron minerals.

Jan 1, 1994

By Michael E. Allen

The building of sanitary and storm drainage sewers in urban or environmentally sensitive areas often requires the use of tunnel construction procedures. While hydraulic considerations may require only small diameters, traditional tunneling techniques make small sizes the least economical. Current state-of-the-art techniques using highly mechanized systems of pipe jacking can provide cost effective solutions to the problems of construction of small size tunnels. The characteristics of mechanized pipe jacking allow rapid advances under difficult ground conditions. The basic pipe jacking cycle is used with a variety of excavation systems to permit the contractor to satisfy engineering as well as economic parameters. These characteristics and several of the systems available are outlined.

Jan 1, 1981

By Z. T. Bieniawski

In the past 15 years, rock mass classifications have experienced unprecedented development and have emerged as powerful practical methods for assessing ground conditions and tunnel support. Such methods as the RMR System (Geomechanics Classification) and the Q-System have provided many advantages over the classical Terzaghi rock-load method introduced in 1946. These new classifications have found wide applications all over the world but some doubts have been expressed and shortcomings pointed out. The author, who developed the RMR System, takes a penetrating look into the promises and the pitfalls of modern rock mass classifications. He dispels some misconceptions and shows how rock mass classifications can serve as effective and dependable design aids in tunneling.

Jan 1, 1987

By Hill McDonald

Sand and gravel deposits may be explored by many different methods. The methods used by The Standard Slag Company are primarily two in nature. One is using an auger which is limited in depth by various soil conditions. The other is a heavy wall dry sampler and a heavy wall wet sampler. The heavy wall dry sampler takes continuous uncontaminated samples up to seven inches in diameter. The heavy wall wet sampler takes continuous uncontaminated samples up to six inches in diameter. For us, the maximum depth of the heavy wall samplers has been two hundred fifty feet of which one hundred feet was above the water table and one hundred fifty feet was below the water table.

Jan 1, 1972

By A. J. Hudson, M. R. Yenchek

Faulty insulators on mine trolley/track haulageways may allow leakage of currents into the mine roof, which may ultimately result in the combustion of the roof material. The National Institute for Occupa¬tional Safety and Health (NIOSH), Pittsburgh Research Laboratory (PRL), devised a passive means to detect overheating insulators on di¬rect current systems. The detector consists of a spring- loaded car¬tridge that ejects a reflective streamer of white Teflon tape when subjected to elevated temperatures. The cartridge assembly can easily be installed over the outer metallic shell of an existing trolley line insu¬lator. If an insulator overheats due to ground leakage currents, the vis¬ible streamer alerts mine personnel traveling on the haulageway.

Jan 1, 2000

By D. M. Richards, A. D. MacPhail

Highland Valley Copper currently mines two low-grade ore bodies, Lornex and Valley. The partnership was formed in 1986. As a cost reduction measure, it was decided to use an in-pit crushing and conveying system to deliver the ore from the Valley Pit to the Lornex mill 3 km (1.8 miles) away and 175 m (575 ft) above the pit rim. The system uses two gyratory crushers that feed a series of conveyors to transport up to 130 kt/d (143,000 stpd) to the main stockpiles. This paper describes the performance of the in-pit crushing system as it is currently configured, as well as its evolution to date and future planned moves.

Jan 1, 1995

By M. S. Klima, M. Fofana

The use of a laboratory-scale magnetic fluid-based separator for coal separations was examined. A Frantz laboratory magnetic separator was modified by fabricating new pole pieces of the appropriate geometry to provide the proper magnetic field gradients. Two separation chambers, which were constructed of Plexiglas, were designed to fit between the pole pieces. A commercially available, water-based, ferromagnetic fluid was used as the separating medium. The separating density was changed by varying the current intensity of the electromagnet coil. Both batch and continuous separations were made using 0.59 x 0.50-mm and 0.18 x 0. 15-mm coal. The results are compared to those obtained using organic liquids.

Jan 1, 1998

By W. Allen Dupree, Charles D. Campbell

A field investigation was conducted by the Ventilation Division, Pittsburgh Health Technology Center (PHTC), Mine Safety and Health Administration (MSHA) to evaluate the effectiveness of a blowing face ventilation system utilizing a water sprayfan system and a single inlet flooded bed dust collector (scrubber) in controlling methane liberation in the face area while mining at brattice distances up to 12.2 meters (40 feet) from the face. The rated capacity of the scrubber was 117 m3/s (4,145 cfm) of air. Results from the investigation indicated a methane dilution capacity of 0.57 m3/s (20 cfm) with the air quantity behind the line brattice averaging 138.7 m3/s (4,900 cfm).

Jan 1, 1991

By F. M. Doyle, S. M. El-Raghy, M. F. El-Demerdash, E. Peters

The Activity Distribution Diagrams (ADD) developed by the authors are computed for Cu-S-H2O and Mo-S-H2O systems. The distributions of metal and sulfur between all species are estimated against pH at different potential levels. Both M-H2O and S-H2O distributions are compared to the M-S-H2O distributions to estimate the changes occurring due to the presence of sulfur. The method of computation follows the Activity Term Criterion, taking into consideration the multi-equilibrium interrelations and conservation of mass. Results are analyzed in terms of dividing a distribution curve into three basic segments. These segments are formation, stability, and dissolution.

Jan 1, 1993

By F. F. Aplan

Estimations have been made of the tonnage of raw ores and coal treated by various beneficiation processes. The amount treated by gravity concentration is substantially greater than that treated by flotation, with coal representing the bulk of the material treated by gravity means. A discussion is given of the trends and anticipated improvements in gravity methods. Except for the concentration of iron ores, magnetic and elec- trostatic separation processes find their greatest use in the beneficiation of non-sulfide ores. Exciting new developments in magnetic materials and separation process (and, to a lesser extent, in the electrostatic process) indicate a substantial increase in the application of such processes to ores and a broad variety of non-ore uses.

Jan 1, 1989

By D. J. McKee, D. M. Wiseman

The usefulness of simulation as a technique for metallurgical process design and optimization studies has been greatly extended over the last few years by the development of a number of general purpose simulation packages. The packages, or simulators, all have the common objective of presenting the mathematical models and simulation methods in a form which is readily usable by plant engineers and metallurgists. To date, most simulators have been concerned with steady state simulation, but packages capable of dynamic simulation are now becoming available. The paper outlines the essential features of versatile steady state and dynamic simulators. Typical applications are presented by considering examples of design and optimization studies. Limitation on the use of simulators are also presented.

Jan 1, 1991

By H. Sis, S. Chander

The pressure filtration behaviors of dispersed and flocculated alumnae slurries at high percent solids were investigated with the objective of determining the effect of surfactant type and concentration on slurry properties. A high-purity alumina powder was used as a model solid. Dispersion of the alumina was controlled by pH and by surfactants that are known to act as electric and steric stabilizers. The effects of both ionic and nonionic sutfactants were investigated. Surface charge measurements of the slurries were carried out by an electrokinetic sonic amplitude (ESA) method to better understand the mechanisms. The effect of surfactant type and concentration on the kinetics of pressure filtration and cake properties are discussed.

Jan 1, 2000

By S. Chander

The fundamentals of flotation are reviewed with an objective to understand the limitations in predicting the performance of a sulfide mineral flotation system and in its scale-up from laboratory studies to plant practice. The difficulties can often be traced back to complex interactions between chemical and physical parameters and nonequilibrium effects. The physical and chemical changes that occur during the long sojourn of sulfide minerals that begins with mining, continues through crushing and grinding, and ends when they emerge from the flotation cell as a concentrate, are reviewed. The benefits of new techniques that have become available in recent years to identify and estimate the amount of surface species are discussed.

Jan 1, 1999

By Murray Malott

The Sheppard Subway extension is currently being constructed in Toronto, Canada for the Toronto Transit Commission (TTC). McNally International Inc., in a joint venture with PCL and the Foundation Company of Canada were awarded the Twin Tunnels contract of the Sheppard extension. The Twin Tunnels project is approximately 4.4 km in length and consists of two separate twin bore drives each 3.3 km and 650 m in length and approximately 400 m of cut and cover construction. This paper presents a case history of the construction of the soft ground tunnels through the complex Toronto glacial deposits using two 5.9 m outside diameter Lovat earth pressure balance (EPB) tunnel boring machines.

Jan 1, 1999

By J. W. Choung, J. A. Finch

Acid rock drainage (ARD) is a recognized environmental challenge facing mining industries. An ambient temperature ferrite (ATF) process has been investigated for treating ARD. Most nonferrous metal and calcium ions present in typical ARDs were found to be detrimental to the ATF process. Three approaches were examined, including C02 aeration, addition of complex agents and use of magnetic seeds. By introducing magnetic seeds in the ATF process, the interferences were minimized and all the precipitates formed with lime neutralization were magnetically recovered from a simulated ARD. The residual concentrations of major metal ions in the treated water were environmentally acceptable. The XRD pattern confirmed the spinel ferrite crystal structure of the products

Jan 1, 2000