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By T. Wang

A new generated NaNO3 ? NaNO2 ? KNO3 ternary thermal energy storage system which has low melting point as 124°C and high specific heat capacity was studied for the short and long?term thermal stability by using the Thermogravimetric Analyzer (TGA). Based on the actual working condition of molten salt in solar two, the simulated cyclic thermal stability measurement was also conducted. The ternary system demonstrates excellent short ? term thermal stability and thermal reliability after cyclic heating and cooling processes. However, in the long ? term as well as the simulated cyclic stability measurement, large amount of weight loss was observed. Moreover, the stepwise long ? term isothermal study reveals that below 440°C the weight change is minimal and this temperature is viewed as the upper limit temperature of thermal stability for this ternary system. To determine the lost phases at high temperature above the upper thermal stability limit, techniques such as XRD and SEM are used to compare the condition of the salt mixture before and after the long ? term thermal stability study. On the basis of the comparison, it can be concluded that the major weight loss was due to the decomposition of sodium nitrite.

Jan 1, 2012

The global tunneling industry has many challenges, both technically and financially, with the latter likely to be a significant feature over the next few years. Many industries have ad-opted standard practices in order to overcome specific technical challenges, from which standard out-comes are anticipated. In tunneling, however, every project is unique so standardized practice is not easy. This requires original thinking and being open to adopting new techniques and technologies as they emerge. Sprayed waterproofing is a hot industry topic and a paper recently presented at the North American Tunneling conference not only discussed this methodology for achieving a dry tunnel but also how it can reduce build costs and construction time. Despite their being relatively few ?universal truths? throughout the tunneling industry, there is one opinion that appears to be shared by most in the sector, ?all tunnels leak.?

Jan 1, 2010

The Coeur Rochester Mine is one of the largest and lowest cost primary silver mines in the United States. In January, the mine surpassed 3.1 kt (100 million oz) of historic silver production. Rochester is owned and operated by Coeur d’Alene Mines, the world’s largest primary silver producer. Rochester is the world’s seventh largest silver mine. It also produces gold — more than 31.1 t (1 million oz) in historic production. Cash operating costs have averaged 8 cents/g ($2.58/oz) of silver since operations began in 1986.

Jan 1, 2004

By John Kinneen, Sunghoon Choi, Arne Fareth, Edward S. Barboe, Kyle R. Ott

A new water treatment plant is to be constructed for a portion of the water supply system of New York City. The project includes construction of new water conveyance tunnels crossing perpendicular and sub-parallel to the existing pressurized water tunnel at two locations. A study was conducted to evaluate the impact of new tunnel construction on stability of the existing tunnel and hydrojacking potential in the surrounding rock mass. This paper introduces a practical approach to evaluate tunnel interaction, expressed in terms of rock-liner interaction, stress-induced stability and hydrojacking failures. A simple method to evaluate hydraulic and mechanical properties of concrete liners and jointed rock mass is also presented.

Jan 1, 2007

By L. F. Ruppert, P. A. Freeman, R. C. Milici, S. J. Tewalt, L. J. Bragg

The U.S. Geological Survey has completed a dig-ital coal resource assessment of six of the top-producing coal beds and coal zones in the northern and central Appalachian Basin coal regions. These include the Pennsylvanian-aged Pittsburgh, Upper Freeport, Lower Kittanning, Fire Clay, Pond Creek, and Pocahontas No. 3 coal beds and coal zones. Resources were calculated on all of the coalbeds/zones, with the exception of the Lower Kittanning coal bed. Preliminary original resources are estimated at about 93 billion short tons (84 billion tonnes), of which about 66 billion short tons (60billion tonnes) remain. Much of the remaining coal in all five coal beds/zones is thinner [<3.5 ft (1.07m)] and deeper [>1,000 ft (305 m)] than the coal that has been mined, but economic resources are still available and mining in each coal bed/zones will continue throughout this decade and into the next given current market conditions.

Jan 1, 2001

By William R. Yernberg

SME’s Arizona Conference was held at the Doubletree Hotel at Reid Park in Tucson on Dec. 5and 6, 2004. The annual conference is organized by the Arizona Conference Board of Directors, which represents SME sections in Arizona and adjacent areas. The conference provides an opportunity for individuals and corporations associated with mining in the region to get together each year to discuss the status of the industry. The meeting featured a keynote address and more than30 technical papers. Two years ago, the U.S. copper industry was facing on a run for two years now,” and “both precious metal and base metal prices are going up.” The increases in metal prices were attributed to development in China and other Asian countries. “With a population of 1.6 billion, China has recently created 80 million jobs,” said Silver.

Jan 1, 2005

By J. C. Schneider, G. Van Weert

Hydrochem Developments Ltd. has developed and put into full scale operation a novel type of vertical flotation column incorporating a multiplicity of mechanically agitated stages. Characteristics of this flotation column include a low height to diameter ratio, high upgrading factors and the possibility of modifying geometry and operation to specific flotation requirements. A commercial unit is currently handling up to 100 tpd rougher concentrate at Dickenson Mines Limited, Balmertown, Ontario. Design parameters and plant performance will be discussed.

Jan 1, 1988

The structural design of a mine haul road involves the determination of cover thickness requirements above the in-situ or sub-grade material. The specification of these layerworks is a critical component in the overall road design process. Poor design often leads to premature failure of the road, safety is often compromised and productivity and equipment service-life will certainly decrease. Historically, the California Bearing Ratio (CBR) cover-curve design method has been widely applied to the structural design of mine haul roads. More recently, established mechanistic design principles have superceded the CBR approach to haul road design, using a multi-layer model to represent the various road structural layers. The structural design and associated layer thickness requirements are then determined following a maximum strain criterion. This paper develops a case-study evaluation of the CBR cover-curve and mechanistic design methodologies and through a comparative analysis of layerworks and materials, highlights how improved structural design can be achieved mechanistically.

Jan 1, 2011

By Douglas D. Campbell, Alan S. Imrie

INTRODUCTION Mica Dam is located on the Columbia River just downstream of the "big bend" of the Columbia, where it leaves the Rocky Mountain Trench and begins to flow southwards, approximately 85 miles north of Revelstoke, B.C. (Fig.l). The dam was built as one of three Columbia River Treaty dams in British Columbia which regulate the flow of the river and provide flood control downstream in Washington and Oregon. In addition, the three Canadian dams make possible greatly increased power generation at existing power plants in the United States and further development along the Columbia and its tributaries in British Columbia. History Mica Dam, constructed during the period 1967 to 1973, is a zoned earthfill embankment 650 feet high, which has 12,000,000 acre feet of live storage and an available head of 550 feet. Power intakes which would serve either a six-unit surface or underground plant were incorporated into the design and construction of the right abutment of the dam (Fig. 2). Prior to 1971 alternative 2500 MW capacity surface and underground powerplant arrangements were studied. Cost estimates for the two alternatives were the same within the limits of estimating procedures. However, it was believed there was a certain continuing risk in locating a surface plant at the toe of a steep canyon wall. Therefore, in 1971 a tentative decision was made to proceed with an underground plant, provided that additional exploration confirmed assumptions of

Jan 1, 1976

By Christof Metzger

This paper discusses the process utilized by the Kiewit?Bilfiger Berger Joint Venture (Contractor) to select, design, and procure the largest mixshield tunnel boring machine (TBM) ever implemented in North America. The mixshield will excavate the 8,534 linear m × 6.7 m ID (28,000 linear ft × 22 ft ID) tunnel for the City of Portland Oregon?s, Bureau of Environmental Services (Owner) East Side CSO Tunnel Project. TBM selection was conducted under a preconstruction contract in which the Contractor, Owner, Construction Management Consultant and Designer collaborated on TBM selection prior to commencement of construction. This paper focuses on TBM design considerations, including the use of one versus two machines, machine configuration,extended-wear protection, hyperbaric interventions, boulder digestion, and erection of a steel-fiber-reinforced segmental lining

By Klaus Rieker

The main train station of Leipzig in Germany is currently being upgraded from a head station to a partially thru station. In order to achieve this, significant ground improvements are necessary. Soil freezing for example is used to create the excavation box retaining walls. The freezing works will be carried out from two tunnels with an inner diameter of 2.4 m (~ 8ft). The tunnels were constructed by the pipe jacking method. The cutter head of the machine was equipped with discs and scrapers. Driving and excavation was carried out using a bentonite supported face. Due to the small arrival shafts, the machine had to be lifted out in components. The essential limitation of settlements during the drives was achieved even better than expected.

Jan 1, 2008

By Anthony D. Hammond

The use of geographic information systems (GIS) as a tool to analyze and display data is gathering momentum in the mining industry. Of particular interest is the capability of GIS to link spatial features and tabular data. The application of GIS in underground mining discussed here concentrates on four technical areas. They are land ownership and mineral claims, exploration management, production and mine safety.

Jan 1, 2002

By Bernhard Leist, William D. Leech, Johann Kröyer, Holger Evers

Landsvirkjun—the national electric power company of Iceland—is building the Kárahnjúkar Hydroelectric Project in eastern Iceland. Two glacial river systems will be dammed and channeled through a series of tunnels into a 690 MW underground powerhouse. The Project has a total of 73 km of tunnels to be excavated of which mosthave been completed. From three access adits, three large diameter (7.2 m to 7.6 m),main-beam, gripper-type, Tunnel Boring Machines (TBMs) are being used to complete50-km of the waterway tunnel. Using the TBMs was a first in Iceland to excavate the complex Icelandic basalt formations, which consist of inclined layers of hard basaltic flows with weaker scoriaceous and sedimentary interbeds. Faults, fissures and dykes that frequently cross the lava flows posed both geologic and hydrogeologic difficulties to the TBM tunneling. This paper describes the extreme challenges that the men and equipment had to endure to complete the tunneling, including the harsh winter weather on the surface and the cold, abundant ground water inflows within the tunnels.

Jan 1, 2007

By Leon Maday, Dan L. Pecha, Jeremy Johnson, Daniel N. Adams

The Brightwater conveyance system includes 26 km of tunnels, a 130 mgd pump station, 2 km of micro tunnels, and a 2.4 km outfall. The tunnels extend from Woodinville to Puget Sound through varying soils in 1 to 7 bars of hydrostatic pressure and depths to 185 m. The tunnel diameters range from 4 to 6 m and include numerous lining systems. This paper highlights major shaft and tunnel design, including dual cellshafts, multiple pipe configuration tunnels, polymer concrete segments, and the use of a one pass lining designed to convey high pressure effluent.

Jan 1, 2005

By J. O. Marsden

Part I in this series of papers considered the chemistry of medium-temperature pressure leaching of copper sulfide concentrates and reviewed the metallurgical testing and initial process development for this technology. This initial work resulted in the development of a process flowsheet utilizing superfine grinding (to a P98 of 12 to 15 µm and P80 of 6 to 7 µm), pressure leaching at 160° to 170ºC, followed by conventional solution extraction (SX) and electrowinning (EW) for the recovery of copper. However, this process required a significant amount of concentrated acid to be fed to the pressure leach vessel to meet the reaction requirements, representing a cost of between $0.03 and 0.05/lb copper (2006 basis) produced by the process. It was immediately recognized that the development of a process that did not require such a large acid addition would be advantageous. This paper, which is Part II in the series, describes the development of a process that incorporates medium-temperature pressure leaching and direct electrowinning (DEW) in a novel and innovative process flowsheet. Phelps Dodge (a subsidiary of Freeport-McMoRan Copper & Gold Inc.) refers to this as the ?MT-DEW-SX? process. Part III in this series covers the large-scale demonstration of the MT-DEW-SX process at Bagdad, Arizona; and Part IV addresses the development and design of a full-scale commercial application at Morenci, Arizona.

Jan 1, 2007

By K. N. Panigrahi

India bestowed with 6000km of the coastal belt, contains some of the richest and largest placer deposits with a mixture of heavy minerals like ilmenite, rutile, leucoxene, zircon, monazite, sillimanite and garnet. Each of the minerals is having economic value due to its inherent characteristics for industrial use in fields of paints, metallurgy, refractory, abrasive and so on. The reserves of titanium bearing minerals (ilmenite, leucoxene, and rutile) in the country is around 378 million tonnes. More than 90% of the titanium based minerals produced worldwide are utilised for making value added products in the pigment industries. Approximately 8 million tonnes of monazite reserves are available in the country from which several rare earth elements like cerium, neodymium, lanthanum, yttrium etc. can be extracted for use in several industries. The country contains a deposit of about 20 million tonnes of zircon, which is used in foundries, refractories, ceramics and chemicals. India has a reserve of 107 million tonnes of garnet and 131 million tonnes of sillimanite required for the abrasive and refractory industries respectively. Keeping in view the multifarious uses, the beach sand minerals are being exploited to have the economic growth of the nation. Although the process adopted for the separations are simple, the equipment involved are specially designed because of the nature of the material of construction. Starting from the spirals to magnetic separators, all equipments are manufactured outside India, which is not only costly, but the availability also takes much time for fulfilling the import formalities. Unlike open cast mining, beach sand mining is a environment friendly mining because dredging is implemented to cut and pump the loose sand through a slurry pump causing less damage to the surface topography as both mining and backfilling takes place simultaneously. Therefore all out efforts are made to explore the beach sand placer deposits in an economic manner to emerge as a leader in the global mineral industries.

Jan 1, 2005

By Robert M. Valentine, Randall L. Lentell

Interpretive geotechnical investigations were performed for the construction of approximately 15,250 m (50,000 ft) of wastewater interceptor tunnels in Austin, Texas. Subsurface materials consist of claystone (or clay shale), siltstone, altered volcanic tuffs, chalk and limestone. Special conditions include multiple crossings of Onion Creek with cover ranging from about 1/2 to 3 m (2 to 10 ft.), and the potential for mixed-face conditions consisting of water-bearing gravels overlying clay shale or siltstone. The methods and results of the geotechnical investigations are discussed and the inferred construction conditions are compared to those encountered during tunneling. A suggested format is presented for interpretive geotechnical reports for underground construction projects.

Jan 1, 1985

By Don Rose

INTRODUCTION A number of tunnels supported and permanently lined by steel-fiber-reinforced shotcrete (SFRS) have been built in North America in the 1980s. The material is more economical than, and technically equal or superior to, conventional shotcrete using wire mesh. The design and construction of SFRS-lined tunnels is straightforward, and only a few new design principles, laboratory tests or construction equipment modifications appear necessary in order to use this material. Modern tunnel Contractors may use cyclic drill-and-blast methods on some tunnels, with intermittent shotcreting as part of an orderly cycle. The Dry Mix method is most suitable for cyclic, intermittent, relatively small-scale shotcreting. However, modern Contractors excavating tunnels continuously using large long Tunnel Boring Machines (TBMs) or Roadheaders may prefer Wet Mix shotcreting on a mass production basis. In either case, the use of steel-fiber-rein¬forced shotcrete (SFRS) promotes the rapid and economical excavation of tunnels. The addition of microsilica will improve SFRS properties and reduce rebound, and is expected to become standard practice with SFRS in North America, as it now is in Scandinavia. HISTORICAL REVIEW Steel-fiber-reinforced shotcrete (SFRS) at the present time (1985) is essentially conventional shotcrete with straight or deformed steel fibers added, and in general SFRS for tunnel linings encounters the same problems that conventional shotcrete does. Shotcrete history is well known. The use of sprayed plaster on wire frames for mounting animal skins by Carl Akeley of the Smithsonian

Jan 1, 1985

By M. F. Bradley, G. M. Schoen

The Magmont Mine, a 50/50 venture between Cominco American Incorporated (the Operator) and Dresser Industries, Inc., (Halliburton), is a metallic mining and milling facility in the new lead belt of Missouri. The mine is located approximately 100 miles southwest of St. Louis. Legislation passed in 1992 by the Missouri legislature requires all metallic mining and processing facilities to apply for a Metallic Minerals Waste Management permit (MMWM) for their waste facilities. Regulations were subsequently promulgated by the Missouri Department of Natural Resources (DNR). Cominco obtained a MMWM permit (MM-006) from the Missouri DNR in 1992.

Jan 1, 2001

By H. Razavizadeh

The recovery of copper from oxide ores containing from 2% to 4.1% acid-soluble copper from the Sarcheshmeh mine in Kerman province of Iran was investigated by agitation leaching in sulfuric acid media. Quartz, as a major constituent, and malachite, as the major copper mineral, were identified in the ore by X-ray diffraction (XRD) and microscopic studies. A series of leaching experiments on the ore was performed over a concentration range of 10 to 20 g/L and temperatures from 15° to 50°C for a maximum of 3 hours. An initial high dissolution of copper was followed by a very slow reaction. By increasing acid concentration and temperature, the dissolution rate of copper was accelerated. However, by increasing acid concentration, the acid consumption of ores was also increased. Surface morphology of solid residues at various leaching times was examined with a scanning electron microscope (SEM). All SEM micrographs of the partially reacted particles displayed a needle structure. The kinetic studies showed that the malachite dissolution rate could be modeled in two stages. About 85% of the malachite dissolution occurred in Stage 1, while the remaining 15% occurred in Stage 2. The data obtained for the leaching kinetics indicate that the dissolution for Stage 1 was a diffusion-controlled reaction with an activation energy of about 20.6 kJ/mole, and the dissolution for the Stag 2 was a chemical-controlled reaction with an activation energy of about 87.6 kJ/mole.

Jan 1, 2008