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By Andrew B. Cecala

The Bureau of Mines conducted a brief laboratory study on the 10-mm diam Dorr-Oliver nylon cyclone to investigate (1) whether high wind speed (>300 ft/min), or sampler inlet orientation with respect to wind direction, can introduce errors when sampling respirable dust, and (2) whether any such errors can be reduced by using an inlet shield. Being preliminary in nature, the study was not structured to produce definitive results, but rather to discern likely trends and to indicate whether or not a more in-depth study of the problem is warranted. Photometric mass sensing measurements suggested that as the wind velocity increased, the cyclone sampling directly into the high-velocity airstream tended to oversample, relative to the cyclone sampling in a low-velocity airstream. Orientation of the sampler introduced measurable differences in sampling efficiency at higher wind velocities. A shield placed around the cyclone diminished the effects of wind velocity and sampler orientation on sampler performance. Results of this work offer sufficient evidence to substantiate the need for a more in-depth study.

Jan 1, 1983

Provide long-term measurement of mine sidewall closure in backfilled stapes subject to flooding. Approach A water resistant extensometer is made by enclosing a rod-actuated transducer in a telescoping tube which is enclosed within an oil-filled outer housing. How It Works To assemble a water resistant extensometer, a cylinder -shaped transducer and two support rings are pushed into the small-diameter section of the telescoping tube where the transducer is held in place by friction. The outside of the small-diameter section of the telescoping tube is then greased and slid into the slightly larger-diameter section. See drawing. The cylinder-shaped transducer contains a potentiometer whose actuating arm is attached to a stainless steel extension rod that passes through one end of the telescoping tube. A similar rod is attached to the opposite end of the transducer body, and extends through the other end of the telescoping tube. A coil spring inside the large diameter end of the telescoping tube extends the tube

Jan 1, 1978

By Christopher J. Bise

INTRODUCTION The level of analysis for the selection of extraction practices and equipment for surface mining differs significantly from that found in underground mining. In underground mines, manufacturers establish the operating ranges of the equipment, such as continuous miners, loaders, and boring machines, based upon required clearances. Even in conventional mining, the drilling and blasting operation is usually based upon experience. The selection of extraction methods and equipment for surface mining is more complex. Since the equipment is not as confined as in deep mining, and the topography tends to be highly variable over the limits of the mining property, primary extraction equipment must be sized according to reach and capacity. Further, due to the depositional characteristics of the over- burden, drilling and blasting patterns must be well- designed to provide proper fragmentation. The following sections provide a general outline for the selection of surface excavation practices and equipment. The topics covered include drilling and blasting and the selection of both primary extraction equipment (draglines and stripping shovels) and secondary extraction equipment (bulldozers, scrapers, and front-end loaders). EXCAVATION FUNDAMENTALS Before discussing surface excavation, a few concepts need to be defined. A bank cubic yard of material is equal to one cubic yard as it lies in its natural or undisturbed state. A loose cubic yard is that portion of a bank yard that after being disturbed has expanded to measure one cubic yard. Swell is the volume increase of a material when it is removed from the natural state. Finally, load factor is the percentage decrease in the density of a material from its natural state to a loose state. Table 1 summarizes these concepts for various materials. When the amount of overburden to be removed to meet a predetermined production rate is established, a suitable bucket size for the primary stripping equipment must be calculated. The following equation can be used: NBSIZE = TBC/[(OF) (BF)] (1) where NBSIZE is the actual bucket capacity after considering the swell percentage, the bucket fill factor, and the operating efficiency; TBC is the theoretical bucket capacity (TBC = COB/NTCPM); OF is the operating efficiency; BF is the bucket fill factor; COB is the cubic yards of overburden to be removed; NTCPM is the number of theoretical cycles per month [NTCPM = (SMH) (3600)/(CT)]; SMH is the scheduled monthly hours; and CT is the cycle time in seconds. FRAGMENTATION PROCEDURES Drilling Where the strength of overburden material is such that blasting is required prior to excavation, drilling is conducted before using explosives. Two methods of drilling are found in mining-percussion and rotary. Penetration of overburden by percussion drilling is carried out by successive impacts of the bit into the rock. Emphasis in this section will be placed on rotary drilling, because for surface mining it is the most versatile form of overburden penetration. Rotary drilling is conducted by rotating a rigid string of tubular rods to which a rock-cutting bit is attached. The drilling energy is supplied by rotation as well as thrust and the cutting action consists of abrasion, scraping, spalling, or chipping. The size range for rotary-drilled blastholes is from 4 in. to 15 in., with 9 in. and 12 in. being common sizes. There are two types of bits used for rotary drilling-drag and rolling cutter. Drag bits are applicable in soft to medium-soft shales or their equivalents. Since their effectiveness is dependent upon a successful scraping action, drilling thrust is lower for drag bits than for rolling cutter bits; the opposite is true for torque requirements. The bits are usually fitted with replace- able tungsten-carbide cutters. Rolling cutter bits, though available in a two-cone configuration, are usually of the three-cone style (Table 2). The rolling cones have either large steel teeth for drilling through soft formations or small tungsten-car- bide inserts for drilling through hard formations. Table 3 relates bit size and weight to the strength of the rock. The major advantage of rotary drilling is its rapid drilling rate. This is due to the fact that, unlike percussion drilling, rock penetration is uniform with depth. Blasting Effective bank preparation deals not only with the fragmentation of overburden but also with the mini-

Jan 1, 1986

Electrical trailing cables are frequently damaged in usage, especially on continuous minors, and because of their weight and damaged condition present a safety hazard to personnel required to handle them. The U.S. Bureau of Mines and FMC Corporation signed Contract No. HO 122011 in August 1971. One of the contract tasks was to study the feasibility of techniques to improve trailing cable support and handling of power cables on underground coal mine machinery and to design a cable-handling device for a continuous mining machine. This report presents the results of the feasibility study, describes the design for a proposed cable handling device and concludes with a recommendation for future action to construct a test rig to evaluate the cable reel system.

Jan 1, 1972

Develop a new technique of in situ rock stress measurement which can be used when and where the conventional methods, such as the overcoring stress relief methods and the hydrofracturing method, cannot be effectively applied. Approach The Bureau of Mines developed basic principles to determine existing biaxial stresses in rock mass by using an instrumentation package consisting of one 3.8-cm-diameter hydraulic cylindrical pressure cell (CPC) and two 5.7-cm-diameter cement-capsulated flat hydraulic borehole pressure cells (BPC) to he installed in a single drill hole.

Jan 1, 1988

By Cyril Smith

THE following table, which is composed of data given in the author's first paper on the thermal conductivity of copper alloys1, contains the results which have been obtained by previous workers on the thermal conductivity of the copper-tin, the copper-phosphorus and the copper-tin-phosphorus alloys (the phosphor bronzes). TABLE 1.-Previous Investigations Composition, Per Cent. by Weight Thermal Conduc¬ Investigator tivity, Cal/Sq. Cm./ Copper Tin Phosphorus CM./Sec.. °C. Hardebecka 95.0 5.0 0.176 (20° C.) Grossmanb 90.1 9.9 0.105 75.5. 24.5 0.059 24.9 75.1 0'.139 (13° C.) 9.7 90.3 0.131 0.0 100.0 0.142 Griffiths and Schofieldc 91.7' 8.0 0.30 0.108 87.2 12.4 0.40 0.087 (20° C.) 90.0 10.0 Small amt. 0.100 Donaldsondd: 87.8 1 11.3 0.35 0.128 Pfleiderere 99.4 1 0.63 0.250 (30° C.) 98.0 1.98. 0.125

Jan 1, 1930

The mining industry is generally regarded as a high risk industry, mainly because of the difficulties in estimating the tonnage and grade of mineral resources, the fluctuations in metal prices, mining problems and other problems which occur with mining in offshore and remote locations, such as appropriation or disruption to supply. As a consequence, finance providers require a high reward from mining projects. In the past two decades, the development of "mega" projects has led to the packaging of the finance becoming more sophisticated. Some would see this move as a measure of the evolution of banking rather than an intrinsic facet of mining finance itself. Project financial managers now require a thorough knowledge of all the financial tools which are available and have to be aware of the funding options so that they can put together a finance package which minimises the cost of the financing with the risk spread adequately between the partners of the financing. The different sources and types of finance for mining projects are described herein along with the factors which determine their costs. To understand the ramifications of financing mining projects, it is essential to appreciate the fundamental difference between debt and equity, which illustrates the importance of gearing. Costs of finance are determined by the interaction of supply and demand forces. Bankers and other financiers have become more adept at isolating a wide selection of risk elements and have devised a formidable range of insurance mechanisms. There is still a lot of money looking for good project risks and if a good project is properly presented and structured, financing can be obtained in today's market.

Jan 1, 1990

By V. R. Spironello

The Bureau of Mines is involved in research directed toward the utilization of municipal solid waste. One of the primary objectives is the recycling of the magnetic fraction of municipal solid waste (raw refuse). This is consistent with one of the Bureau's goals, which is to minimize the requirements for mineral commodities by maximizing metals recovery from secondary domestic resources, In this investigation, cupola trials were made using combinations of refuse scrap with shredded automobile scrap under basic and acid slag practices. Furnace operating information and the behavior of alloying and tramp elements was obtained. The research showed that it is possible to utilize up to 60 percent refuse scrap in the cupola under basic practice and 30 percent under acid practice, Aluminum in refuse scrap, present in bimetallic cans, increased the recoveries of silicon and manganese charged to the cupola. Increased use of refuse scrap provided iron of lower sulfur. The alumina resulting from oxidation increased the slag volume. The aluminum and tin contents of the iron increased with increasing levels of refuse scrap in the charge. Lead was not a problem with respect to contamination of the iron. In basic practice, operation of the cupola was satisfactory since all slags were adequately fluid. In acid practice, operation became troublesome above the 45-percent level. Under both practices, the cupola iron melting rate decreased. Particulates in scrubber water and stack condensate samples contained lead, zinc, and tin, and the dust load increased. The tensile and transverse strengths of the iron produced under both practices are reported.

Jan 1, 1980

By Gary E. Sherman

Preliminary economic mining feasibility studies were conducted by the Bureau of Mines to estimate mining costs in the Juneau gold belt area of the Juneau Mining District, southeastern Alaska. Investigations were conducted on the economics of two mineral deposit types: (1.) Berners Bay vein gold deposits, and (2.) stockwork gold deposits containing gold, silver, and lead. Cost estimates were developed using the Bureau of Mines Cost Estimating System (CES). Discounted cash flow return on investment (DeFROI) was calculated using the Bureau's MINSIM computer program. Underground mining of a Berners Bay vein gold deposit was found to be economic (15 pct DCFROI) at a recoverable metal value of $353.67/mt for a 100 mtpd shrinkage stoping mine with a 10 yr mine life, $324.76/mt for a 20 yr mine life, $138.63/mt for a 500 mtpd longhole stoping mine with a 10 yr mine 1 ffe, and $127.50/mt for a 20 yr mine life. Block caving mining of a large stockwork gold deposit was found to be economic at a recoverable metal value of $15.28/mt for a 18,000 mtpd mine with a 20 yr mine life.

Jan 1, 2011

By D. S. Bird

The Kennecott Utah Copper Modernization Project, initiated in 1986, was directed to provide an expansion and modernization of mining and process facilities at the property's Bingham Canyon Mine and ore concentrators. Major components in the project included installation of an in-pit ore crusher, transfer conveying system, and construction of a new copper ore concentrator with a design capacity basis of 70,000 tonnes/day. The Copperton Concentrator was commissioned in February 1988. A principal feature of the plant is the grinding circuit, comprised of three identical lines, each consisting of a 10.37 m (diameter) by 4.57 m (length) Semi-Autogenous Grinding (SAG) mill and two 5.54 m (diameter) by 8.62 m (length) ball mills. The SAG mills are driven by two variable-speed 9,000 kW DC motors coupled through a clutch-pinion gear-ring gear assembly. The ball mills are driven by 4,125 kW synchronous motors coupled through a typical clutch-pinion gear-ring gear system. The expansion and particularly the Copperton Concentrator performance was so successful that by early 1989, management began examining options to further expand production capacity. With regards to the concentrator, numerous alternatives were considered, ranging from installation of a grinding line similar to one of the existing lines, to a "super" line consisting of a 12.8 meter (diameter) SAG mill and a 20,000 kW motor with a capacity of 50,000 tonnes per day. The technical and economic analysis of the various scenarios indicated that one "large" 11.0 meter (diameter) by 4.88 meter (length) SAG mill with a production capacity of 32,000 tonnes per day and a 12,000 kW drive would be optimum. The key question to be answered in the project was whether to continue with the pinion-ring gear combination, or install a gearless drive. The following paper outlines many of the items that were evaluated in the mill selection process followed by actual plant performance, and a discussion of ongoing plant continuous improvement projects.

Jan 1, 1995

By O. Naiker, T. Riley

Keywords: Pyrometallurgy, furnace, Xstrata, ferrochromium, Premus Technology The presentation will give a basic overview of Xstrata Alloys. Included will be a brief history of the Alloys division as well as of each plant within the division. The Xstrata chrome plants utilise a wide variety of production processes, including Xstrata's Premus process, the Outokumpu process, and the conventional process. Xstrata?s Lion Project is underway, with commissioning expected in the third quarter of 2006. The new smelter will utilize Xstrata?s patented Premus process, and the competitiveness of the Premus process is discussed.

Jan 1, 2006

By Cz. Mora, A. Pawelczyk, D. Hreniak, P. Nowak, A. Dyonizy, S. Strek, W. Strek, K. Grabas, A. Ostrowski

Globalization and a growing demand for limited raw material resources have forced changes in the approach to the supply chain. This is particularly true in the case of rare earths, which are regarded as one of the most important development indicators of modern technologies. To ensure a secure supply of commodities, the European economies have been prompted to investigate REE recovery from sources which until recently, for technical or economic reasons, were considered not sufficiently attractive. An interesting example is apatite phosphogypsum waste dumps. The REE content in these waste dumps averages around 0.5-1 %. One of the most important phosphogypsum locations in Poland is the Lower Silesia region where a phosphoric acid Chemical Plant "Wizów" operated for several dozen years. In this work, rare earths are leached from the phosphogypsum crystalline structure by a chemical treatment and can then be separated into individual chemical compounds. The technology used in these recovery tests, matches up to a coherent European raw materials policy supporting effective management of resources and promoting waste materials recycling.

Jan 1, 2014

By P. Tsang

The mechanisms and functions of yield pillar are analyzed by employing finite element method that takes time dependent and plastic failure of rock into consideration. The design criteria for different geological conditions are discussed. The results provide further evidences that yield pillar design will improve floor or roof condition, especially when the floor and/or roof strata are weaker than the coal. Based on this study, the yield pillar size is determined for one cod1 mine located in southern West Virginia.

Jan 1, 1989

By C. J. Van Niekerk

The study comprised of the investigation into the sensitization characteristics of AISI 409 titanium stabilized ferritic stainless steel during low heat input welding. AISI 409 is a fully ferritic stainless steel used in catalytic converters and tubing for automotive exhaust systems due to the supposition that sensitization does not occur during low heat input welding. Two plates of 2 and 4 mm were tested for sensitization during low heat input welding. The study confirmed that chromium carbide (M23C6) precipitation occurs on the grain boundaries in the heat-affected zone with consequent depletion of Cr adjacent to the grain boundaries during welding. In the 2 mm plate sensitization occurred in the heat input range of 0.1 kJ/mm to above 0.25 kJ/mm and in the 4 mm plate sensitization occurred in the heat input range of 0.2 to 0.9 kJ/mm. Ti stabilization is ineffective at the heat inputs used in this investigation due to the rapid cooling rate through the temperature region where TiC precipitates. The presence of N was found to be detrimental since it consumes Ti on cooling, forming TiN, effectively lowering the amount of Ti available for TiC formation during rapid cooling after welding. Annealing for 5 minutes at 725°C does not improve the sensitization characteristics of the welded plate. There is a linear increase in grain size as heat input increases. The resistance to pitting corrosion decreases in the sensitized, welded plate in theheat-affected zone adjacent to the fusion line of welding. Keywords AISI 409 ferritic stainless steel, sensitization, grain growth, resistance to pitting corrosion, low heat input welding.

Jan 1, 2011

By R. G. Horvath

In the Hamilton area, and in many other areas of Ontario and around the world, large diameter drilled pier (caisson) foundations are frequently selected as the most appropriate foundation system for heavily loaded structures. Locally, these drilled piers are typically founded in competent glacial till or in the underlying shale bedrock depending on the anticipated design loads. Drilled pier foundations socketed into shale bedrock were selected for the Hamilton General Hospital Addition. The structural loads applied to socketed pier foundations are supported through shaft resistance, which is the shearing resistance developed along the vertical pier-rock interface, and by end-bearing resistance. The factors which control the load-displacement-time behaviour of socketed pier foundations are the strength and deformation characteristics of: a) the concrete pier, b) the rock mass, and c) the interface between the concrete pier and the rock.

Jan 1, 1987

By G. L. Gates

The waters used to waterflood the Wilmington oilfield were studied by the Bureau of Mines, in cooperation with the city of Long Beach, Calif. Increases in the pressure of the injection wells indicated that they were being plugged by materials suspended in the waters. This study was made to identify the suspended materials, determine their origin, and find methods of preventing their formation. The suspended oil-coated materials were iron sulfide, barium sulfate, calcium carbonate, clay, and sand (or silica). Results indicated that the sulfide, which was as high as 90 milligrams per liter, was the product of sulfate-reducing bacteria. The injection of ocean water increased the sulfate content of the waters in the petroleum reservoirs from 3 to 250 milligrams per liter, thereby furnishing sulfate for growth of the bacteria. The waters were supersaturated with barium sulfate. Laboratory tests showed that sulfide could be removed from the waters by adding iron at a cost of 1 to 2 mills per barrel. The solubility of iron sulfide and calcium orthophosphate in the injection waters was also determined.

Jan 1, 1975

By Alexander Nikolic

The paper presents the foundation design and construction of a landmark urban redevelopment scheme in central London, UK. The scheme comprises the new Tottenham Court Road Underground station, Crossrail interchange box and associated over-site commercial development. The paper focuses on the design, procurement and construction of large diameter bored piles, up to 68m in depth, which form the foundation support system for the over-site commercial development at Denmark Place. The congestion below ground required an intricate foundation design solution which has been a catalyst for developing innovative load transfer arrangements and has resulted in the advancement of pile construction technology in the UK. The foundation system was also designed to cater for the construction of two significant elements of proposed below ground infrastructure. Selected large diameter piles have been constructed within 1.1m of live underground railway tunnels. An innovative D-shaped pile was constructed in a zone subject to particular spatial constraints. The proposed Crossrail tunnels will be bored within 1m of selected over-site development piles. In addition, a 30m deep excavation forming a new escalator box will be constructed in direct contact with the over-site development piles. The stakeholder engagement process is described together with the foundation design development and buildability assessment. The benefits from early collaboration between the designers and specialist contractors are highlighted. From an analytical design perspective, the entire foundation construction sequence was modelled in detail in order to assess the soil structure interaction and any potential adverse effects on existing elements of underground infrastructure. The results from the three dimensional numerical modelling simulation are compared with field monitoring data.

Jan 1, 2011

By Wallace W. Roepke

The Bureau of Mines conducted a series of experiments using Illinois No. 6 coal to determine the effect of asymmetric wear on airborne respirable dust (ARD), specific energy, cutting force, and normal force. Plumb-bob-type bits--one new bit and four ground with different sized flats--were used. Constant-depth linear cuts at 0.32, 0.64, 1.27, and 2.54-cm cut depths were made. Both cutting force and normal force increased as the flat area increased. Specific energy demonstrated a statistically significant increase with flat area at the 0.32-and 1.27-cm cut depth only. Specific ARD showed a statistically significant decrease with increasing flat area only at the 0.64-cm cut depth. Increasing cut depth increased cutting force but decreased specific energy and specific ARD. Normal force increased with increasing cut depth for the new bit but exhibited a maximum at 0.64 cm for the bits with flats.

Jan 1, 1983

By Dennis P. Martin, Michael M. Fitz, James E. Friant

Methods for reducing the cyclic nature of drill and blast tunneling operations have been long needed. A miniature blasting system using 10 mm (.375 in.) holes, 0.91 m (36 in.) deep, and blasting only one hole at a time makes it practical for men to work behind a shield, remaining at the face during the entire process. A prototype automated module was developed to drill, load the hole and initiate the detonation without moving from the hole. A unique cost effective gell explosive and a novel, low cost initiation method were developed.

Jan 1, 1989

By C. Dinis da Cama

In order to reduce the complexity of mechanisms influencing rock- fragmentation by blasting a simulation approach is proposed, using the capabilities of micro-computer interactive graphics. Situations involving cratering and bench blasting are simulated, and both jointed and intact rocks can be subjected to explosive action, taking into consideration its breakage mechanisms. Size analysis curves relating rock distribution before and after the blasts are determined and compared with field data.

Jan 1, 1984