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By Charles D. Litton

This Bureau of Mines paper describes a novel fire detector that can be used to discriminate between smoke produced by a fire and smoke produced by a diesel engine. The detector uses a pyrolysis technique whereby a sample of smoke- laden gas passes through a short, heated tube within which fire smoke particles pyrolyze and increase their number concentration and decrease their average size, while diesel smoke particles are unaffected. The detector is designed for use in mines that use diesel-powered equipment where the detection of fires is complicated because of the diesel emissions background levels of smoke and other products of combustion.

Jan 1, 1989

By Bob Clayton, David Readett

Jameson Cell technology has found applications in the cleaning of entrained material in copper Solvent Extraction - Electrowin plants. The materials involved are largely organic substances that have not been totally removed prior to treatment of the rich electrolyte in the tank house. This paper discusses the recovery of the entrained organics in the rich electrolyte streams at Phelps Dodge Morenci in Arizona. Mount Isa Mines in Queensland. Australia and the Olympic Dam Operations in South Australia. The paper details the design, performance, the feed and product characteristics, capacity and operation. In one operation the entrained material has been observed to include crud that has been formed in the SX train. The mechanism of recovery is also discussed.

Jan 1, 1993

By K. J. Shoop, S. J. Ripke, T. C. Rao, T. C. Eisele

This study investigated the use of a 7.6-cm inside diameter, 344.2-cm-tall horizontally baffled column to reduce the ash content of a low-sulfur bituminous coal. Tests were carried out to determine how the baffled column responded to changes in feed rate, reagent dosage and feed quality. The tests were also carried out to compare the columns performance to a conventional column installation in an operating plant. In this paper, the results of this investigation are reviewed and discussed.

Jan 1, 1999

By J. B. Gwiazda

In designing mine workings and adequate roof supports, it is indispensable to determine properties of the strata surrounding the workings. The proper selection of roof supports is based, before everything else, on a thorough knowledge of the roof rock strength, especially tensile strength. This parameter is a vital factor in the delamination of roof rocks and eventual cave-in. It is also important to know the properties of the floor on which the roof supports are set. While driving galleries, it is essential to know beforehand the strength of rocks that will be encountered in the near future during the work. The devices described will help to obtain this information.

Jan 1, 1987

By S. Formby, J. Avraamides

Transportation of sodium cyanide from factory to minesite often attracts adverse comment from both the community and government agencies. In Western Australia the transportation of 30% w/w aqueous sodium cyanide solution raised fears in the community concerning the safety of such material in the event of spillage. The Chemistry Centre of Western Australia initiated a study of the effects of such a spill, to determine appropriate short and long term response strategies. Factors which were considered included the rate of hydrogen cyanide gas release under various climatic and soil conditions and the effect of alternative treatments in reducing such emissions. The data collected have been used to plan emergency response procedures.

Jan 1, 1989

By S. Liu

A general account of nitrogen-generating systems, including the surface fixed, surface-mobile and underground-mobile types is presented. These systems have recently been adopted in coal mines in China to prevent and extinguish fires. The paper stresses nitrogen -injection technology and relevant systems of monitoring and stopping air leakage.

Jan 1, 1998

By D. I. Phillips, P. J. Bethell

This paper focuses on the -1/2 mm cleaning at Elk Run Coal. The original circuitry incorporated desliming cyclones. Problems with slimes entrainment in the cyclone underflow (froth cell feed) resulted in poor froth cell selectivity. Laboratory test work led to the installation of high frequency desliming screens. Consequently, great improvement in cell performance was brought about by enhanced desliming with the ability to use split flotation. The modifications resulted in significant improvement in total plant performance and overall yield while maintaining clean coal quality.

Jan 1, 1987

By Douglas J. Pendrell, Marvin D. Simmons, E. Raymond Boc

The U. S. Army Corps of Engineers is in the early stages of design for an estimated 14 m (46 ft) diameter tunnel in northeast New Jersey. This tunnel will carry flood waters from the upper end of the Pompton River in Wayne County, to an outlet in Newark Bay, a distance of 33 km (20.5 miles). The tunnel will be constructed by a tunnel boring machine (TBM), the size of which is unprecedented at the present time. The alignment is through Triassic and Jurassic sandstones, siltstones, and shales that include three beds of basalt that range in thickness from 76 to 310 m (250 to 1020 ft).

Jan 1, 1991

Machine breakdowns and maintenance delays are large contributors to lost production and increased operating costs in the mining industry. The US Bureau of Mines is investigating the applications of expert system technology to diagnostic and predictive maintenance for mining equipment. This will help increase mining productivity and decrease operating costs by reducing the frequency of equipment failures and repair times. The Bureau has begun this effort by applying expert system techniques to the diagnosis of hydraulic system problems on a continuous mining machine. This paper discusses the development of the hydraulic diagnostic expert system.

Jan 1, 1992

By P. R. Busmann, D. J. Rogers

The Bureau of Reclamation's Syar Tunnel project included excavation of a 9.2 kilometer (5.7 mile) long, 3.6 meter (11.8 ft) diameter tunnel through gently dipping sedimentary rocks consisting of shales, siltstones, sandstones and limestone. The tunnel was supported full length with precast concrete invert segments and lightweight steel sets and lagging. Several world records for advance rate were set, including 57 meters (187 ft) in an eight hour shift and 127 meters (417 ft) in a 24 hour day. The tunneling system utilized a remanufactured and modified Robbins hardrock TBM and a 9,280 meter (30,450 ft) long, 61 centimeter (24 inch) wide, continuous conveyor system.

Jan 1, 1991

By H. Kandemir, G. Neeling, P. A. Spencer

Gold extractions from three refractory sulphide concentrates have been increased by bacterial oxidation with T. ferrooxidans prior to cyanide leaching. Arsenopyrite, pyrite and stibnite were the major sulphide components associated with gold in the concentrates examined. Kinetic oxidation tests were conducted for each concentrate by monitoring iron and arsenic levels in leach slurry. A correlation has been established between the level of bacterial oxidation and gold extraction from cyanide leaching of oxidised residues. High levels of bacterial oxidation have been achieved in approximately 8 days at pulp densities of 20-25/ w/v solids, resulting in 70-90% gold extraction.

Jan 1, 1987

By Stephen H. E. Phillips, Michael J. Beus

A pneumatic impact breaker is used to fragment the rock at the shaft bottom, replacing the drill and blast cycle. A backhoe-type mucker removes the broken rock. The operators are in protective cabs below the bottom work deck in the shaft. Preliminary testing has been accomplished at underground and surface test sites in Arizona. Seven, approximately 6.4 m deep by 7.3 m-diameter (21 ft by 24 ft) test holes, (a total of 45 m (148 ft)), were recently excavated in various rock types, including jointed and massive quartz monzonite and rhyolite. An average advance rate of .4 m/hr (1.24 ft/hr) has been achieved. This includes breaking and mucking the rock. Further data is being sought from an in-shaft demonstration.

Jan 1, 1981

By W. P. Stroud, R. S. Dennen

A ground penetrating synthetic pulse radar system has been used by the US Bureau of Mines to probe into a coal pillar to locate hidden structures or anomalies. Direct matrix inversion was used to obtain a velocity image of the interior of the pillar. The reconstructed image showed the existence and location of a relatively low velocity material within the pillar. Core samples were taken from the pillar in a region surrounding the low velocity material. Analysis of the cores showed the presence of a clay vein coinciding with the low velocity material imaged in the tomogram.

Jan 1, 1992

By C. K. Nworu, L. O. Asuquo, C. O. Nebo

Selective flocculation studies of Agbaja iron ore with starch-type and nonionic polyacrylamide-type flocculants has been conducted to determine the effect of flocculant type. The results indicate that corn starch was slightly better than cassava starch in selectivity performance. Cassava starch was in turn better than Superfloc 16, while the poorest results were obtained with commercial starch. Sodium humate shows better dispersive capability, and thus enhanced flocculation results, than sodium silicate. Pulp pH affects the zeta potential, polymer chain configuration and hence selective flocculation. Overall results indicate that recovery and separation of this very fine grained iron oxide by selective flocculation is feasible.

Jan 1, 1995

By N. Edmonson

Frasch sulfur production/pricing decisions are based on market demand, less nondiscretionary sulfur supply. Price covers the cost of Frasch production and byproduct sellers accept the Frasch price structure. Large stocks have led Canadian byproduct producers to price aggressively at times, but their near-term drawdown suggests more passive price policies in the 1990s. Expanding continental nondiscretionary supply is combining with sizable Frasch supply increments to weaken prices. Simulations using a market model embodying these structural characteristics indicate that expanding demand may not result in substantial recovery from 1992 price lows before 1996.

Jan 1, 1995

By M. R. Bowie, J. M. Barker, J. S. Hingtgen

Techniques of testing perlite require a combination of art and science. The modifications made to the perlite Corp. vertical laboratory furnace include addition of instrumentation, flowmeters, vibrators, automatic feeders, and regulators. The basic testing sequence consists of expanded density, furnace yield, compacted density, percent sinkers, and compaction resistance. These tests are modified versions of those specified by the Perlite Institute. This sequence is designed as a preliminary evaluation of a material's suitability for horticultural-aggregate end uses rather than a detailed measure of filtration capability.

Jan 1, 1988

By C. F. Lee, Bezalel C. Haimson

A 300 m deep test hole at Ontario Hydro's Darlington nuclear plant site, 65 km east of Toronto, was used to determine the state of stress in the Paleozoic limestones (O-22O m depth) and the Precambrian granitic gneiss (220-300 m). The results of the hydrofracturing measurements indicated a state of high horizontal stress along the depth of boring and a consistent orientation of principal stresses in each geologic unit. These results were confirmed by a borehole TV camera survey, and by overcoring tests. The magnitudes and orientations of the measured in situ stresses were used in a feasibility study of siting an underground nuclear plant, and in particular in the geotechnical design of proposed reactor caverns in Precambrian rocks. Their implications on cavern stability under operational and accident conditions were analytically studied, taking into consideration the potential superposition of thermomechanical stresses under loss-of-coolant condition, and the possibility of thermal spalling in the host rock.

Jan 1, 1979

By J. Holmes Armstead, John L. Dobra

This paper examines some lesser known risks in foreign investment by U.S. companies that derive from international judicial activism by U.S. courts and the potential for extending U.S. anti-trust regulations to companies' foreign operations. The discussion of international judicial activism reviews the implications of the U.S. Second Circuit Court's ruling in the Union Carbide/Bhopal case for U.S. companies investing abroad and the discussion of extending U.S. anti-trust regulations focuses on proposals coming out the Clinton administration's Justice Department.

Jan 1, 1996

By Drupad B. Desai, Alexander Rosenbaum

In recent years, there has been an increasing use of two-pass tunnel lining system consisting of segmental unbolted expandable precast concrete initial lining and cast-in¬place concrete final lining in the United States. Used so far in soft ground tunneling performed under free air, it often includes a waterproofing or gasproofing membrane placed between the initial and final linings. This paper describes the utilization of this two-pass system for an extension of the Baltimore Metro, constructed in part under compressed air. It offers a description of the extension project, known as Section C; addresses the tunnel lining selection process and the design of the lining elements; examines the effect of the adopted lining system and tunneling technique on the design of the project's major structural components; and describes design modification instructions in order to accommodate constantly changing field conditions.

Jan 1, 1993

By John A. Bischoff, Francis S. Kendorski

A technique that has been used for inspection and appraisal of rock tunnels is described. It enables a rapid and complete record to be made of those factors necessary for the engineering assessment of the rock conditions surrounding a tunnel. Full understanding of the regional geology, and a careful recording of data concerning the principal geological and construction factors is essential basic data for a tunneling project, whether the tunnel is under construction or is already in service. A methodical recording of data concerning general geology, shears, fracture orientations, spacing, persistence, rock classification, water condition, shear frequency, excavation method, blasting procedure, and rock stabilization and support methods, combined with a photographic record, can be completed by experienced engineers and geologists at the rate of over 1000 feet of tunnel per shift.

Jan 1, 1976