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Circulating Air Classification of Manufactured Sand Due to environmental concerns, the supply and use of natural gravel has been limited by the Swedish government. The Swedish concrete industry is therefore examining manufactured sand as an alternative that has equal or better product quality, and which the Swedish quarry industry already has the ability to deliver. However, in order to comply with the specifications set by the concrete industry, a better means of classification is needed, as the proportion of fine particles (filler) smaller than 63 - 125 ¦m in size must be reduced. One classification technology that meets the requirements may be air classification. This paper examines the process of circulating air classification, which is not yet commonly used in the Swedish quarry industry; suggesting that a better understanding of the process is needed. The circulating air classifier in this study has two internal machine parameters that can affect the separation point; namely, the speeds of the circulating fan and the separator fan. We study their effect on the separation point as well as the interaction between these parameters. Full-scale parameter tests are also conducted, in which size distribution is measured before and after the circulating air classification. This study shows how the different parameters affect the separation point and that it is possible to produce manufactured sand according to specifications. Computational fluid dynamics (CFD, Fluent) is used to study the internal flow of the air circulating within the classifier. A single-phase study of the flow field is conducted to support and explain the findings from the full-scale tests.

Sep 13, 2010

By W. Bullen

A hypothetical economic model has been developed for diamond projects in the Canadian Arctic using data from recent exploration and mining projects. The model reflects economic conditions applicable to the diamond mining industry in the Canadian Arctic at the present time. The economic model captures pre-production expenditures, production data, and post-production costs. Before- and after-tax cash flows are derived from the data along with the relevant economic criteria. From the corporate perspective, the model provides guidance concerning the minimum size and/or in situ value per tonne requirements of targets being sought in order to ensure economic success and predict exploration and development expenditures. From the government perspective, the model provides an indication of income and mining tax revenues that can be expected from a particular diamond project. The model shows, on average, diamond projects in the Canadian Arctic are expensive to explore for and develop, but are economically robust under the present conditions. They generate great economic return for mining companies and significant amounts of tax revenue for governments. The fact that diamonds can be transported directly from the minesite by air makes them particularly attractive targets for mining companies that operate in the Canadian Arctic.

Jan 1, 2006

By Forrest T. Moyer

To keep the mineral and allied industries informed of trends in the causes of accidents and to point out the need for corrective measures, the Bureau of Mines collects, analyzes, and publishes, periodically health and safety statistics. This report includes data for 1961 on injury experience, with related employment statistics, at coal mines in the United Status. These data are presented in tabular form under the following headings; General Injury Experience Tables 1 to 6: Current data on number of injuries, degree of injury, frequency and severity rates, average severity, and related employment and production data by work location.

Jan 1, 1963

By J-T Zhu, Q-Y Tu, S-L Kong, L Wang, Y-P Cheng, H-Y Liu, Q-L Yang

China is the largest coal-producing country in the world, while the geological conditions of deep coal mining are extremely complicated with high ground stress, high gas pressure and low permeability, which results in the difficulty of gas drainage and aggravation of gas explosion and coal and gas outburst disasters. Co-extraction of coal and gas is an effective method to eliminate coalmine gas disasters and realise the safe exploitation of coal and efficient gas drainage at the same time. This concept is widely accepted by the main coal-producing countries around the world, while the concrete definition of co-extraction is vague and not unified, and there is little accurate theoretical support for co-extraction of coal and gas, which makes it hard to determine efficient gas drainage methods correspondingly according to the features of coal seams in a comprehensive and systematic way. Based on theoretical analysis, laboratory test and field observations, basic thoughts and specific definition of co-extraction of coal and gas were put forward after analysing the occurrence characteristics of coal seams in China. We obtained the mechanism of mining-enhanced permeability and established the corresponding theoretical model, which is the process of fracture network formation through opening recovery of the original fractures and new fractures produced by unloading damage. Based on the core idea of ‘mining-enhanced permeability’, engineering approaches of ‘unloading by boreholes drilling’ for the single coal seam and ‘unloading by protective seam mining’ for the coal seam group were proposed to realise safe and efficient co-extraction of coal and gas. Meanwhile, combined with engineering practice, we put forward the construction principle of coal exploitation and gas drainage system in different coal seam occurrence conditions. The above methods were applied successfully in the Tunlan coalmine in Shanxi Province and the Panyi coalmine in Anhui Province, which had established the ‘underground-surface united’ spatial gas drainage modes, and could ensure safe and efficient co-extraction of coal and gas in the outburst coalmines.CITATION:Cheng, Y-P, Wang, L, Liu, H-Y, Kong, S-L, Yang, Q-L, Zhu, J-T and Tu, Q-Y, 2015. Theory of safe and efficient co-extraction of coal and gas and its applications, in Proceedings The Australian Mine Ventilation Conference, pp 79–92 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 31, 2015

By Charles Merguerian

In medium- to high-grade metamorphic terrains such as found in New York City(NYC), rock mass texture and mineralogy are important factors in predicting TBM penetration destiny. Integration of data from over two decades of traditional field and tunnel mapping suggest that hard-rock TBM penetration in the NYC area depends upon textural, mineralogic, and structural control. The bedrock of NYC consists of many different lithologic units of varying age, composition, texture, and metamorphic grade including many varieties of intrusive rock. In addition, brittle faults of numerous orientations cut the polydeformed crystalline bedrock, producing zones of highly fractured and disturbed ground and high water inflows. Pre-bid compilation of published bedrock data, drill core analysis by geologists to establish lithologic and mineralogic trends, integrated surface geologic mapping along a proposed alignment, and targeted petrographic and geotechnical investigations to characterize the rock mass conditions together constitute an important prelude to successful subsurface bidding and tunneling. A carefully planned program of as-built geological mapping, structural analysis, fracture class mapping, and monitoring of machine performance data provide important information for adjusting to changed conditions. In complex terrains, a clear understanding of the structural geology of any proposed tunnel line is the simplest and most cost-effective method to mitigate losses encountered during TBM tunneling.

Jan 1, 2005

The principle activities of the Explosives Research Laboratory from July 1, 1961 to June 30, 1962, are described briefly in part 1. Part 2 gives short abstracts of publications that appeared during fiscal year 1962; in general, the research reported in these publications antedates the report period. Part 3 gives the results of an investigation which, although too limited to warrant separate publication, merits presentation in some detail because of current interest in ammonium nitrate-fuel oil compositions.

Jan 1, 1964

By Jean R. Garcia, Paulo J. R. Albuquerque, Renato P. Cunha, Osvaldo Freitas Neto

"Abstract Results obtained from in-situ load tests carried out on drilled displacement piles sunk in a porous, lateritic and unsaturated soil deposit, are analyzed in this paper. Three slow-maintained load tests were performed on deep instrumented piles with a diameter of 0.37 m and around 12 m long. The soil deposit consists of a superficial, silty clay “porous” layer 6 m thick, with an average standard penetration blow count (NSPT) of 4 and cone tip resistance and sleeve friction (qc and fs) of 1.5 MPa and 48 kPa, respectively. Under this layer there is a residual stratum 10 m thick, geotechnically consisting of a “porous” clayey silt with an average NSPT of 7 and qc and fs of 2.4 MPa and 202 kPa, respectively. The water table was reached at a depth of 17 m below ground level. The results of the field load tests yielded a maximum pile load (average for the tests) of 1428 kN, which is twice as high as corresponding experimental values from standard bored piles with similar geometric conditions. Exhumation of one of the tested piles was carried out after the test, in order to check integrity and shaft conditions. Numerical finite element analyses, using the commercially available French Code LCPC Cesar®, were performed in order to back-analyze the geotechnical soil parameters for a post execution pile condition. The results permitted a better understanding of the improvement of the subsoil given the intrinsic execution characteristics of this particular pile. It was also possible to note that drilled displacement piles have great potential to become an economically viable solution in tropical soils, given the enhanced behavior of such piles when compared to alternative (cheaper) techniques. In fact, it has several advantages which should make it a key foundation type in the Brazilian market in the future.IntroductionMost buildings in tropical soils use, as the main type of foundation, deep bored or auger type piles. These types of foundations can be performed in various ways, for example with or without soil extraction, with or without bentonite mud and so on. Two main processes maybe formulated: the first execution process is typified by bored pile types, continuous flight auger piles etc., which do not cause excessive soil displacement during excavation. With respect to the second process, one could mention, amongst others, driven piles (precast concrete or steel), Franki piles and drilled displacement piles, which do displace the soil during excavation by pushing the soil laterally around the hole in order to allow either the penetration of the pile or the excavator auger."

Jan 1, 2014

By M. R. Campbell

"IntroductionON THE LAST DAY of December, 1951, a half-century of steel production was completed in the open hearth department of Dominion Iron & Steel, Limited, in Sydney, Nova Scotia.During that period, almost every known variation of basic steel making practice was used in working out a steel making process which would overcome the difficult metallurgical problems imposed by the use of Cape Breton coal and Wabana ore.This paper is presented as a brief review of these steel making practices, setting forth the fundamental metallurgical factors involved in their success or failure.Establishing the IndustryThe story of steel production at Sydney is closely interwoven with that of coal. The steel industry owes its inception to a desire on the part of the Dominion Coal Company, which was incorporated in 1893, to improve its marketing position by increasing sales of slack coal and providing a year-round demand for its product. Accordingly, the Dominion Iron and Steel Company, Limited, was incorporated on March 30th, 1899, with Mr. H. M. Whitney -who was President of the Dominion Coal Company -as its first President. The new Company was given powers to manufacture and process iron and steel, and to mine all minerals, including coal.A strong inducement to the industry was the bounty offered by the Dominion Government for the production of both iron and steel."

Jan 1, 1952

By Rose L. Ballard

This chapter summarizes data on crude nonfuel mineral production for the United States, its island possessions, and the Commonwealth of Puerto Rico. Included also are the tables that show the principal nonfuel mineral commodities exported from and imported into the United States and that compare world and U.S. mineral production. The detailed data from which these tables were derived are contained in the individual commodity chapters of volume I and in the State chapters of volume II of this edition of the Minerals Yearbook. Although crude mineral production may be measured at any of several stages of extraction and processing, the stage of measurement used in this chapter is what is ordinarily termed "mine output." It usually refers to minerals or ores in the form in which they are first extracted from the ground, but customarily includes the output from auxiliary processing at or near the mines.

Jan 1, 1983

By Francis E. Federspiel

In 1984 and 1985, at the request of the U.S. Forest Service, the U.S. Bureau of Mines examined the 87,720-acre South Boise Yuba study area (formerly known as RARE II Wilderness Recommended area I-4553) to evaluate mineral resources. The study area and additions are in Blaine, Camas, and Elmore Counties, 10, about 60 mi east of Boise. Granitic rocks of the Cretaceous age Idaho Batholith occupy the western two-thirds of the study area. A Tertiary age granitic complex has intruded, and broken into small blocks, Paleozoic age sedimentary rocks in the eastern third of the study area. Tertiary Challis Volcanics overlie both of these rock types. Principal mineralized structures are gold-and silver-bearing quartz veins and shear zones trending northwest to easterly in the Cretaceous granitic rocks. Copper, lead, and zinc are accessory metals in many mineralized structures.

Jan 1, 1987

By T. M. Tharp

Attempts to analyze the stability of slopes, foundations and underground openings in discontinuously jointed rock have generally assumed full joint continuity or ignored the role of stress concentration at the tips of discontinuous joints. The most common approach in rock slopes is to consider a failure plane consisting of coplanar, but discontinuous joints separated by intact rock. The intact rock is assumed to fail in shear as a MohrCoulomb material and to contribute a strength component proportional to the fraction of the failure plane that is intact rock (Jennings, 1970). An alternative approach by Stimpson (1978) applies Lajtai's (1969) theory for shear strength of discontinuously jointed rock masses to slopes. Lajtai allows tensile failure in the intact rock of a composite surface. This theory yields lower shear strength than that of Jennings (1970) except in the presence of high normal compression, however it also fails to account for the stress concentration at the tip of a discontinuous joint. For a given slope geometry, stresses increase with slope height, but in both of these models rock mass strength is independent of size. A fracture mechanics analysis shows that particularly for small slopes, rock mass strength decreases with size.A continuous stepped failure surface produced by propagation of preexisting joints may develop at lower shear stress than pre¬dicted by the Jennings (1970) or Lajtai (1969) models. This fracture mechanics model applied to slopes in competent rock is more realistic in its assumed failure mechanism, and for large slopes more conservative than the Jennings (1970) or Lajtai models (1969).

Jan 1, 1984

By A. R. Dover

The Richmond San Rafael Bridge (Figure 1) is a 4.3 mile long major toll bridge span across northern San Francisco Bay. Tutor-Saliba/Koch/Tidewater (TSKT) conducted a comprehensive seismic retrofit, which was at the time Caltrans? largest-ever construction contract at $484 million. The robust foundation retrofit design of 11 bridge piers included the installation of 26 new, large diameter (126 to 162 inch OD, wall thickness 1.5 to 2.25 inches) CIDH and CISS piles, with steel pipe piles installed to tip elevations of Elev. ?140 to -220 ft, in water depths up to 70 feet. The open-ended steel pipe piles had initial sections ranging from 71 to 172 feet long, with full lengths that extended to the bay bottom and then through 100 to 130 feet of marine sediments to top of bedrock. The marine soils of most interest consisted mainly of soft to firm Young Bay Mud (YBM), a silty, moderately-sensitive clay common to SF Bay. A key constructability issue was the prediction of pipe piles ?running? under self weight (198 to 625 kips in air) and pile driving hammer weight (IHC S-500 with total assembly weight of 322 kips). The term "pile running" is used to describe the penetration of the pile into the soil due to the self-weight of the pile only. This issue was critical because 1) there was limited head room under the bridge deck, and 2) if piles run too deep, the pile splicing on several piles would be problematic (the lowest desirable pile top elevation after running was +10 ft). While running measurements are sometimes made during marine/nearshore construction, there is little published data on predicted vs. actual running. This paper discusses the running prediction under self weight for 26 piles, and the methodology used in developing the predictions, which ranged from 15 to 94 ft of penetration below mudline. Pile running was recorded and compared with predicted values. The prediction methodology was quite good, and no significant constructability problems were encountered. The authors ?tweaked? the model to provide a slightly improved prediction method. The paper presents the model, predictions, observations, and discusses important lessons learned.

Jan 1, 2006

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 E. H. Boswell, E. M. Cushing

The Mississippi embayment east of the Mississippi River is part of a vast geologic and hydrologic province. The abundance of water available is largely responsible for the agricultural history of the area and is perhaps the key factor in the rapidly accelerating trend toward industrialization. The multiple artesian aquifer systems that underlie the region and the alluvial aquifer along the Mississippi River are virtually undeveloped sources of fresh water in that they are yielding only a fraction of the water available. The potential yield of the 12 aquifer systems is estimated to be about 25,000 mgd (million gpd) of which only about 600 mgd is presently being withdrawn. The amount of water in storage in these systems is about 1600 trillion gal. Ground water having a dissolved-solids content of less than 500 ppm is generally available at depths of less than 1000 ft, and water having a dissolved-solids content of less than 1000 ppm is available in some places to depths of more than 3000 ft. Iron is the most common troublesome chemical constituent in the ground water. Water in varying amounts is also available from streams within the region. The amount of water which originates within the region and which leaves it as streamflow during a year averages about 50 million acre-ft (about 45,000 mgd). An additional 375 million acre-ft (about 340,000 mgd), which originated outside the region, leaves the region as streamflow during an average year. Some streams have considerable flow during periods of no precipitation and the water during these periods generally has a low dissolved-solids content. Large quantities of water from streams and waterbearing sands (aquifers) are available in the Mississippi embayment east of the Mississippi River. Most of the region is underlain by aquifer systems that will yield large quantities of water to wells, making ground water the most readily available source of fresh water. About 90% of the water used in the region is obtained from wells. Streams have been used primarily to dispose of, and dilute, wastes that have been dumped into them. The Mississippi, Ohio and Tennessee rivers, and the lower parts of the Tombigee and Yazoo rivers also serve as a means of transportation. This nominally water-rich region receives from 48 to 56 in. of precipitation in average years and is crossed by several large rivers. The largest, the Mississippi River, is the western boundary of the region discussed in this paper. The economy of the region is basically agricultural, but industry has become increasingly important since World War 11. The diversification and mechanization of agriculture have resulted in a surplus of manpower, most of which is being absorbed by the expansion of industry. Further industrial expansion probably will occur because of the available manpower, natural resources and economical transportation. Increasing demands on available water supplies will be made and the future economic growth of the region will be largely dependent upon wise utilization and management of the water resources.

Jan 1, 1969

By Jean-Sébastien Lambert, Serge Roberge

"At the end of 2014, Holcim Canada (Demix Aggregates Division) considered the possibility of drillingand blasting a big volume of rock in order to expose a high-quality limestone bench in one of their urbanarea quarries in Laval, Quebec (Canada). The project includes many challenges and has thus been qualified as a high-risk operation."

Jan 1, 2016

Currently in Canada there are 15 major mining companies with a minimum of $1 billion in market capitalization or net private value. This group forms the core of an important sector for Canada. The mining sector had gross revenues of about $35 billion in 1988. This compares to a Canadian GDP of $410 billion in 1988. There are at least three different sub-groups within the mining group, each facing the future with very different prospects for the coming years.

Jan 1, 1989

By W. K. Overbey

The Bureau of Mines conducted surface joint and stress measurements, airborne remote sensing imagery studies, compass-oriented borehole televiewer surveys, numerical simulation of fractured wells, and well productivity studies in a four-quadrangle study area of Ohio, to determine the effects of earth fracture systems on the deliverability of gas storage fields. The results of these studies indicate that much useful information about a gas storage reservoir can be obtained and put to practical use by studying--(1) oriented cores for fractures and directional permeability, (2) orientation of induced hydraulic fractures for alignment of well patterns, and (3) aerial photos and multispectral scanner imagery for general surface geology comparison and to determine if some, development patterns can be generated by such results. The absence of known tectonic elements associated with flat-lying sediments, such as faults or fracture zones that can be seen on the surface, indicates that the use of remote sensors such as radar or aerial photography is not likely to be useful in picking well locations for drilling. Studies similar to those discussed here should be conducted in gently folded and strongly folded sedimentary formation areas to determine if the increased knowledge of earth fracture systems under these conditions might be beneficial in gasfield and gas storage reservoir development.

Jan 1, 1974

By M Ash, P Bellairs

The world class iron ore mines at Mt Whaleback, Tom Price and Paraburdoo located in the Hamersley Province of Western Australia must mine the Mt McRae Shale to obtain high grade ore from the Dales Gorge Member of the Brockman Iron Formation. The Mt McRae Shale contains a Black Pyritic Shale lithology that reacts with Ammonium Nitrate based explosives. This paper provides an overview of the problems associated with mining this reactive rock type as well as the development of a comprehensive procedure to safely and efficiently blast, excavate and dispose of this material.

Jan 1, 1995

By C. J. A. Mcewan, C. M. Rice

The Rosita Hills contain rich, vein- and breccia pipe-hosted precious metal deposits. Volcanic activity occurred in two cycles - an early, mainly andesitic cone-building phase that terminated in the formation of a caldera and breccia pipes and a later phase characterised by trachytic lavas and dykes, rhyolite domes and lamprophyre dykes. Alteration consists of weak propylitic and argillic and, locally, intense advanced argillic, K-feldspar sericitic and silicic types. Marked trace-element depletions (Rb, Sr, Zn, Mn) are associated with K-feldspar-sericitic alteration and with advanced argillic alterations, whereas enrichments (Pb, Ag) are associated with K-feldspar-sericitic alteration. Gold distribution is highly localised and is controlled by breccia pipes and a caldera ring fault; it is not related to district scale alteration. In general, the geochemical and alteration patterns are complex, but they are clearly influenced by linear structures, the caldera ring fault and breccia pipes. Pipe-hosted Au-Ag and vein-hosted Ag mineralisation are associated, respectively, with early andesitic and late, post-caldera rhyolitic activity. The pipe-hosted and, especially, the vein-hosted mineralisation show affinities with adularia-sericite-type epithermal deposits

Jan 1, 1991

By Sohta Takatsu, Hachiroh Mizubata, Shigeki Kudoh, Kazuya Takekuni, Yoshinori Yamada

A special type of shotcrete is used to improve the performance of open-type TBM in difficult situations. The Hakamagoshi and Johana tunnels are expressway evacuation tunnels of 3.2 km and 5.1 km in length, respectively (total 9.1 km) that were excavated by one open-type TBM. The geological conditions at the sites were estimated to be good before excavation. However, 95% of the rock turned out to be two ranking orders worse than the estimated classes. Therefore, we used a special shotcrete for bad rock conditions, and succeeded in excavating the tunnel at an average rate of 270 m/month.

Jan 1, 2001