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By M. M. Kim

Zn-27% Al was pressure infiltrated into a column of 20 micron diameter abrasive grade SiC particles to give billets with particle loading of 50 voli.une %. Some billets were heated to a temperature where they became semi-solid and diluted with liquid Zn-27% Al alloy to give billets with particle loadings of 12 and 16 volume %. Some of these billets were then extruded into wire with an area reduction of approximately 98%. Tensile properties of the as-cast billets were always inferior to those of the matrix alloys; however, the extruded composite samples showed at 37% improvement in ultimate tensile strength compared to their extruded conventional counterparts. The fracture surfaces of these samples are described.

Jan 1, 1990

By Keith G. Wallace

Coal mine ventilation systems are often subject to high leakage rates. As a result, changes in airflow resistance will strongly affect the efficiency with which air is delivered to the working place. One major source of airflow resistance is the line brattice used to direct air from the last open crosscut to the working face. Because it is a great distance from the fan, the resistance of the line brattice can result in more overall leakage than an equivalent resistance closer to the fan. Substituting auxiliary fans for brattice eliminates this source of resistance, with improvements in system efficiency and cost. Also, in some mines, the leakage that leads to spontaneous combustion can be reduced. The benefits obtained by several different brattice and fan substitutions have been studied by Mine Ventilation Services, Inc., Lafayette, CA, under contract to the U.S. Bureau of Mines. Changes in main fan duty were compared with additional costs associated with auxiliary fans. Results indicate that in some circumstances, considerable leakage reductions and cost savings are possible.

Jan 1, 1990

By D. J. Cook, R. H. Fan, D. R. Maneval, Y-H. Shen

In this study, two placer mine processing plant effluent waters of significantly different characteristics were tested to determine the applicability of polymers along with other techniques to achieve reduced levels of turbidity. The waters from a Gilmore Creek mine and a Crooked Creek mine were characterized both as to their chemical and physical properties. The inorganic minerals were in large measure identified, and the principal cations were identified. The fine solids were studied as m their mineral identification and the extent of their electrical charges. Test work was done using polyrthylene oxide (PEO) and a liquid cationic polymer along with adjunct additives to determine optimum amounts of these coagulants for minimum consumption and optimum settling efficiency.

Jan 1, 1990

By V. C. Wittchen, T. R. Yu, J. E. Croxall

"The consolidated rockfill at Kidd Creek Mines is a weakly cemented, minus 15 cm aggregate which posed problems for conventional drill/blast drifting methods. Consequently, lateral access to mineable ore adjacent to backfilled areas was gained by drifting around the fill in shattered rock.In mid-1987, Kidd Creek Mines began to investigate means of mechanically excavating drifts in backfill . The results of this investigation led to a trial program using a Dosco MK-2A Roadheader to excavate the required drifts in backfill.The roadheader was tested at Kidd Creek Mines from July to November 1988, in 28-735 X /C to be used as the top access for drilling and blasting 32-74/ ST. During this period, the roadheader excavated 54 m of a 4.3 m by 3. 7 m arched drift in backfill. Cutting rates over the period averaged 0.8 m/cutting hour as projected with a daily high of 2.0 m/cutting hour.Wood-lagged 2-piece steel arches on 1.2 m centres were chosen as ground support for the trial. Shotcrete will be tested in a roadheader drive for its potential to improve productivity by replacing the steel arches.The trial program included evaluations of point-attack picks, two sizes of cutter motor, 20 MPa (3000 psi) water-assisted cutting, cuttings-removal systems, and environmental control devices."

Jan 1, 1990

Prevent collisions between large mine-haulage trucks and smaller vehicles parked in areas not visible to the haulage-truck operator, Approach Two electronic systems were developed to detect the presence of vehicles in the blind areas of a parked haulage truck. The systems can warn haulage truck operators of presence of vehicles that are blocked from view. The systems do not apply for trucks in travel. How It Works The systems use electronic transmitting techniques-one system is based on low-frequency radio waves and the other on very-high-frequency radio waves. Each system requires that a signal transmitter be mounted on the smaller vehicle to be detected. Continuous signals from this transmitter are sensed by receiving antennas mounted on the right front and rear of the large haulage truck. Upon receiving a signal, the receiver energizes warning lights and a buzzer in the cab of the haulage truck, alerting the operator to a possible collision hazard. Detection distance is adjustable, depending upon the size of the haulage truck, but a minimum of 30 feet was the design goal.

Jan 1, 1990

By Douglas C. Peters

Part of the ground control research at the U.S. Bureau of Mines is involved with improving ground control data collection and analysis methods. A geographic information system (GIs) is being used within this research effort to standardize the data collected and provide a common graphical and tabular format and analysis system for researchers to access information on underground coal mines. In addition, GIS's can perform relational analyses on multiple map and tabular data sets which are not possible through map-creation or CAD packages or through data bases alone. In addition to standardizing ground control analyses, there is an increasing need for rapid analysis of ground control data in connection with increasing production rates at longwall mines. The examination of a large number of interrelated parameters and their impact on short-term mine safety and productivity under the time constraints imposed by rapid production requires computer-aided techniques. A GIs provides the means to quickly, quantitatively, and reproducibly evaluate mine-wide conditions. This overview of GI8 techniques for mine data integration and analysis, using a mine in Colorado as an example site, will cover the input of data into a GIs, including mine-wide monitoring system data and general data such as roof control plans and geology. The methods to geographically reference these data sets and retrieve and combine them also will be covered. Automation of such processes briefly will be reviewed to allow future users to automate their mine data analyses.

Jan 1, 1990

By Perring CS, Vearncombe J. R, Ho SE, Groves DI

Large Late Archaean greenstone belts in Western Australia, Canada and Zimbabwe, contain abundant mesothermal gold, volcanogenic massive base-metal sulphide, and komatiite-associated Ni-Cu mineralization. These greenstone belts are similar in many respects to convergent and accretionary plate margins found in the Pacific rim; modem environments which are cor-respondingly rich in gold and base-metal mineralization. The giant gold placer deposits of the Late Archaean Witwatersrand Basin (the world's largest gold producer) formed in a foreland or retro-arc basin; in a similar tectonic setting to much modem placer mineralization around the Pacific. Gold and volcanogenic base-metal sulphide mineralization are abundant in Late Archaean terranes and the Pacific rim because1. gold mineralization is a product of convergent margin tectonics, and 2. accretion in convergent margin orogens provides the best chance of preserving base-metal mineralization related to submarine volcanism.It is therefore likely that the abundance of gold and base-metal sulphide mineralization in the Late Archaean reflects the widespread growth and sta-bilization of continental crust via tectonic processes broadly similar to those operating in the present Pacific basin.

Jan 1, 1990

Synthetic hollow microspheres have demonstrated reliable sensitization and detonation characteristics in industrial explosives for almost two decades. During that time, water gel formulations and use conditions have changed. The introduction of emulsion explosives has also dictated technical improvements in microsphere sensitizers. In contrast to microspheres, gassing or other sensitizing techniques often cannot satisfy the manufacturing and blasting characteristics required of today's explosives. This paper discusses the sensitizing properties of microspheres, formulating guidelines and quality considerations. Packaging, sampling, transfer, metering, mixing and pumping information is also provided.

Jan 1, 1990

By Jay S. Gunasekera

Since great emphasis is being placed on the manufacturing science and processing science programs in the Department of Defence and other government research agencies and industries; currently, extensive research on computer aided design(CAD)/ computer aided manufacturing (CAM)/ and computer aided engineering (CAE) is being conducted at Ohio University (OU) . OU has invested over a million dollars in CAD/CAM hardware and software. Design and analysis packages like ALPID, NIKE, STREAM, SHEAR, POLY_FLON, RINGROLL have been developed or modified at OUusing finite element method, finite difference techniques or enhanced slab analysis. Packages like ABAQUS, FLUENT, and NASTRAN have been extensively used.

Jan 1, 1990

By P. K. Davis, B. Gharib

The results of a previous basic study of the flow and design characteristics of hydrocyclones demonstrated that a recovery as high as 99% with a product rating* of 0.95 can be achieved on a batch+ basis with a single, water-only cyclone if it is configured properly. The next logical step was to demonstrate continuous processing of gob for the efficient recovery of coal by means of a laboratory-size demonstration system. A project to design and construct such a single-¬cyclone system was sponsored by the US Department of Energy, which also sponsored the initial study. A recovery of 93% with a product rating of 0.89 was demonstrated. The system design and the data taken are discussed.

Jan 1, 1990

By Sven A. Wehrwein

Leveraged buyouts are a fixture in today's market place. This paper will include comments on how LBO's are analyzed, structured and sold, as well as an overview on the present environment of LBO's.

Jan 1, 1990

By J. Béland, C. Giguère

"The auriferous mineralization at the Sigma-2 gold mine occurs in quartz-carbonate-tourmaline veins emplaced in a fractured granaphyre layer in the upper part of a differentiated gabbro-diorite sill. Kinematic indicators show that fracture planes were active as strike slip, dip-slip (reverse) and tensional faults.Measurements of attitudes of fractures and movement vectors indicate eight different sets that can be grouped into three systems: (I) an east-west oriented system includes a subvertical set and two other sets dipping north and south respectively; (2) a subhorizontal system of two conjugate sets bisected by a third tensional set; and (3)a system of sub vertical conjugate northeast and north-northwest trending sets.Kinematic analysis indicates that the subvertical set of the east west system was subjected to dextral strike-slip movement activated by a northwest-southeast compressive stress whereas the bulk deformation resulting from the remaining and subsequent seven sets can be explained by a protracted subhorizontal north-south compressive stress.The valuable gold mineralization is found principally in the fracture-filling veins of the subhorizontal system and subordinately in the other sets; among these other sets, the NE trending subvertical one is slightly more favourable.The over-all tectonic picture is that of an early mild dextral strike slip faulting in a ductile-brittle medium followed by a general flattening involving, first, a vertical and, later, a lateral extension by fracturing in a medium that had become brittle.The structural features are such that the differentiated sill could not be the source of the auriferous hydrothermal solutions."

Jan 1, 1990

The U.S. Bureau of Mines conducted a series of laboratory tests in a full-scale model to determine the respirable quartz dust capture efficiency of an irrigated-filter collection system while testing different filter densities, different filter materials, preconditioning water sprays, and wetting additives in the spray water. Impactor samplers were operated upstream and downstream of the filter unit to determine overall dust collection efficiency. The impactor filters containing the 0.7-to 4.7-J.l-m size fractions were analyzed for quartz content, and these data were used to calculate quartz dust collection efficiency. The results of this testing indicated that (1) increased ftIter density improved quartz dust collection, but also resulted in a significant increase in pressure drop across the filter, (2) an alternate synthetic filter material improved dust collection without increasing pressure drop, (3) preconditioning sprays mounted in the system ductwork can have a beneficial effect on dust collection, and (4) additives to the spray water did not significantly increase dust collection.

Jan 1, 1990

By G. T. Lineberry, R. S. Mateer

Often only after years of "technical dormancy" do errors in published literature become apparent and meaningful. To prevent duplication of effort for future generations, the following corrections are offered. These errors were discovered during a recent study in which a computer program for mine hoist rope selection was developed (Lineberry and Mateer, 1988). In order of increasing gravity: Captions for Figs. 3 and 4 are transposed. Purported to be a more accurate method of rope selection than the process of successive approximation, the direct method assumes linearity between a given rope's minimum breaking strength, T, and unit rope weight, WV. Because of the sensitive location of the constant, K, in equation (8) for breaking strength, the significance of this nonlinearity is magnified. For a typical 6 x 37 class fiber core wire rope (Wire Rope Corp. of America, 1985), K actually varies from 43,650 to 52,190, depending upon rope diameter. Although the direct solution permits a rapid selection of hoist rope, an indirect (iterative) solution procedure is favored because of its improved accuracy and ease of computerization. Equation (8) for minimum breaking strength is in error. It should read:

Jan 1, 1990

By Smith R. N

The Olympic Dam copper-uranium-gold-silver deposit is located approximately 520km north-northwest of Adelaide, South Australia. The deposit was discovered in 1975 by the Exploration Division of Western Mining Corporation (WMC). A joint venture, to facilitate development of the deposit was formed in mid 1979 between WMC (51%) and the British Petroleum Group (BP) (49%).

Jan 1, 1990

"Cambior now holds a 49% interest in the Valdez Creek Placer, having acquired American Barrick's 23.125% interest in May 1990. At the same time, the company assumed the management of the operation and received environmental permits to divert the river. Plans are underway to divert the Valdez River in order to continue mining the deposit upstream, and to construct a new, higher capacity wash plant (by 60%) closer to the operations. Mining operations, which were suspended in October 1989 pending higher gold prices, resumed in August 1990. The mine is expected to produce 10000 ounces of gold in 1990and more than 80 000 ounces in 1991.IntroductionThe Valdez Creek Placer is located in the Valdez Creek mining district of Alaska on the western flank of the Clearwater mountain range, about 150 miles northeast of Anchorage by air (Fig. I) . The mine is accessible by air or by road.The mine is situated at an elevation of about 3000 ft and is isolated from towns and villages. Consequently, the mine site contains the facilities necessary to house and feed 135 people at any given time. The Valdez Creek Placer has 159 employees, including 130hourly and 29 salaried employees. The hourly employees are divided into three rotating teams. The daily schedule consists of two shifts of 12 hours, and each team works 14 days followed by seven days off, resulting in a weekly rotation of teams.The salaried employees work normal hours for ten consecutive days followed by four days off. A weekly rotation ensures continuity of services and management.Gold was first discovered at Valdez Creek in 1903, when a team of four men led by Peter Monahan left the village of Valdez to explore the area up the Susitna River, to the east of Mount McKinley. They discovered gold at the mouth of a creek that they immediately named Valdez Creek, in honour of their native town. In 1904, they discovered the Tammany Channel to the right of Valdez Creek. This was the beginning of a long period of mining in the area which continued until the beginning of World War II .In 1980, the Denali Mining Co. was formed. Geophysical work and drilling carried out through 1980 and 1981 led to the discovery of Channel A, a second channel which is older than the Tammany Channel. In 1983, Denali Mining optioned its claims to Camindex to explore, develop and mine the Valdez Creek property. A joint venture agreement was signed among Camindex, Talcorp, BCP Alaska (Barrick), Sum Resources (Cambior), Norfran and WGM to form Valdez Creek Mining Co., Inc., and production began in 1984. Valdez Creek Mining Co., Inc. (VCMC) was subsequently restructured and in 1989 was held by the following three companies: Camindex Mines Ltd. - 51070; Cambior Inc. - 25.875%; and American Barrick - 23.125%.VCMC is managed by a committee of the partners. Decisions made by the committee are subject to a 70% majority vote. Cambior receives its share of production in kind, and contributes in the same proportion to the expenses of the joint venture (VCMC)."

Jan 1, 1990

By Richards RG

The Australian glass sand industry produces some 2.8 million tonnes per annum of silica sand, of which about 2.0 million tonnes are exported and the rest is for the domestic market. Approximate production rates for each Australian state are listed.The variety of processing methods used in the currently exploited deposits reflects the size, location, and characteristics of the various deposits and the requirement of the end market/s. The industry uses to a large extent equipment developed for the separation of mineral sands, particularly as it applies to low grade heavy mineral deposits, where low cost, high capacity and metallurgically efficient equipment has proved eminently suitable for the production of the low value glass sands.The requirements of the domestic market, as well as those of the present and potential export markets are discussed covering quality requirements, distribution channels and other factors critical to success.

Jan 1, 1990

By N. Kyriazi

The U.S. Bureau of Mines subjected the CSE SR-lOO self-contained self-rescuer (SCSR) approved by the National Institute for Occupational Safety and Health (NIOSH) and the Mine Safety and Health Administration (MSHA) to a series of laboratory treatments designed to simulate various environmental conditions in underground coal mines. The tests were designed to predict the ability of the self-rescuers to withstand those environmental stresses without causing a decrease in wearer protection. The apparatus were heated to 710 C for 48 h, cooled to -450 C for 16 h, vibrated for 9 h, and dropped 1 m on each axis. A critical concern was internal damage to an apparatus, without any obvious external signs, that would cause it to malfunction or seriously degrade its performance. Carbon dioxide (C02) levels in apparatus with combined treatments were higher than in apparatus with individual treatments and untreated apparatus. The higher levels remained within safe limits, however. None of the treatments caused venting of the small oxygen cylinder that provides starter oxygen. Some bottles were found to be empty because of manufacturing defects in the burst disks. This problem was corrected in later models. The heat treatments did make the case ends more difficult to remove and the breathing bag sticky and subsequently more difficult to unfold. An apparatus that was dropped and vibrated had a broken desiccant bag that released some of its contents which compromised the seal of the relief valve. The case was dented from the drops. As with the first-generation self-rescuers, if there is visible damage to the case of the apparatus, the apparatus should be considered to be internally damaged and must be removed from service.

Jan 1, 1990

By Corbett GJ

Epithermal gold-silver deposits occur in young volcanic terrains where post-mineral cover commonly impedes the search for mineralisation. At the Togi Project in Honshu, Japan, a complex mineralised system is largely covered by post mineral volcaniclastics. A combination of high resolution electrical resistivity surveying and detailed airphoto interpretation has, with close geological control, enabled synthesis of structural and alteration characteristics of the Togi geothermal system, in turn permitting ranking of the prospects for drill testing.

Jan 1, 1990

By L. D. Smith

"Those who submit competing proposals for projects seek to present senior management with complete and fully supported material that will not fail under questioning. Hopefully, misleading notions and omissions will have been minimized and there will have been testing of the assumptions regarding the economic, social and political environments.A capital project evaluation team can do management and itself a service by including a sound approach to the impact of inflation (and its twin problem, interest) on a project and a great disservice with an inappropriate approach to inflation.InflationHandled deftly, inflation can alter a project evaluation to show almost any result the handler desires. It must be a constant source of frustration for design people and cost estimators to spend weeks perfecting the technical aspects of a project in order to minimize costs, only to have all of their efforts set awash in a sea of financial and economic assumptions that submerge all of the detail. In all of this, inflation is perhaps the largest offender, with inflation criteria often being brought to bear at the last minute, almost as an afterthought. Perhaps this tardiness reflects the difficulty of the subject and the belief that senior management will take its own approach to the problems of inflation. Such a belief is unfair to senior management, for it is entitled to not being misled by omission. It is entitled to the full use of the skills of the evaluating team, including reasonable assumptions of the impact of inflation.Working in a consulting context, one has the opportunity to participate in the evaluation of a large number of projects."

Jan 1, 1990