Search Documents

By J. C. Armbrust

The Morenci Open Pit Mine, located in south-eastern Arizona, is owned and operated by Phelps Dodge Morenci, Inc. The Mine has been predominantly a rail mine since its origin in 1937. However, beginning in early 1986, a program was initiated to phase out the rail mining operation and replace it with a more flexible and productive truck haulage scheme. This transformation from rail to truck haulage will be accomplished when the current in-pit crushing and conveying project is completed in late 1988.

Jan 1, 1988

By C. W. Hoffman

A fairly recent development in the field of particle separation is now under investigation to determine its value to the mining industry. The method employed is probability sizing through a vibrating network of decreasing screen openings. While probability sizing as such is not new, the possibility of using it for coarse, highly abrasive ores at high tonnage rates has only recently appeared to merit practical consideration. The advantages to be gained by the use of probability sizing vs. conventional screening methods are: reduced space requirements for a high capacity unit, fewer moving parts, more versatile product sizing selection, reduced maintenance requirements and lower power consumption.

Jan 1, 1968

By Alex Naudts

Pre-excavation grouting is a predictable and reliable technique performed to prevent or minimize settlement in advance of, or during the tunneling operation. It safeguards the infrastructure above the tunnel alignment. Cement based suspension grouts and sodium silicate based grouts are frequently injected to consolidate and strengthen the formation and create a reinforced canopy above the tunnel trajectory. Grouting is typically performed through permeation and permeation in conjunction with hydrofracturing. Multiple injection passes through steel sleeve pipes are ideal, since they create an effective forespiling system to facilitate tunneling without causing unacceptable settlement, even with minimal overburden thickness. Ten pre-excavation grouting projects performed in the North America are discussed in this paper.

Jan 1, 2008

By Remo Grandori, Manfred Jaeger, Fabrizio Antonini, Luis Vigl

The EVINOS-MORNOS tunnel project with its 30 km of length is one of the longest hydraulic tunnel in the world realised with TBM method. The adverse geological conditions, the high cover and the short construction schedule were a great challenge for the successful construction of this tunnel. The paper will describe: the criteria adopted for the tunnel design, the selection of the construction methods and equipment, the productions of the 4 TBMs adopted and the comparison of the behaviour of the different type of TBMs in the various rock conditions, including special conditions, the characteristics of the adopted in situ and precast linings, a comparison between the foreseen and actual construction schedules, the contractual implications of realising a tunnel in such a severe and complex conditions.

Jan 1, 1995

By J. J. Moore

Combustion synthesis, or self-propagating high-temperature synthesis (SHS), reaction systems are discussed with respect to thermodynamics and kinetics. In particular, the effect of the process parameters, e.g. particle size, [All] ignition and combustion temperatures, on these self-sustaining reactions is discussed. Combustion theory is used to investigate the effect of the overall actuation energy of the SHS reaction on the combustion front propagation rate and in obtaining a clearer understanding of the transition from stable to unstable propagation. Finally, examples of the application of combustion synthesis to advanced materials processes are made, in particular the synthesis of Ni-Ti-X intermetallic shape memory alloys, TiC-AI2O3 and ZrB2-AI203 ceramic composite materials.

Jan 1, 1992

By Peter L. Hofmann

Significant quantities of nuclear wastes were first generated in 1944 as a byproduct of the national defense program. To establish the current inventories and future projections of nuclear waste products is not a simple task. The Oak Ridge National Laboratory recently issued a report which now constitutes the official basis for nuclear waste inventories and projections. Radioactive wastes originate from five major sources (U .S. Department of Energy, 1980b) : (1) From the commercial nuclear fuel cycle related to the production of electricity , (2) From defense related activities, (3) From institutions such as hospitals, universities, and research foundations, (4) From industrial uses of radioisotopes, and (5) From mining and milling of uranium ores.

Jan 1, 1981

By H. B. Oblad

The WEMCO® SmartCell™ flotation machine is a continuously-stirred tank reactor in which solids are suspended in water and are contacted with air. The reaction is particle flotation resulting in the separation of valuable material from gangue. The effects of several operating variables on the flows of water and air and on motor power were measured. A miniature magnetic flowmeter was installed in the draft tube that allowed measurement of the water flows into the rotor. This work has led to a better understanding of machine function which will lead to improved performance and better operation. General equations for optimization, design, and scale-up were inferred.

Jan 1, 2002

By James A. Barclay

Results of investigations over approximately the last 10 years by the Bureau of Mines and others on technology for recovering cell-grade alumina from domestic nonbauxitic resources such as clay, anorthosite, alunite, dawsonitic oil shale, coal ash, and coal shale are reviewed. It is concluded that, although many innovative techniques have evolved from this effort and have been shown to be technically feasible, energy and economic considerations will prevent any of the processes from competing with the Bayer process under normal conditions. Based on the Bureau's experience, some variation of clay-HCI leaching, HC1 gas sparging crystallization has the greatest potential as an alternative to the Bayer-bauxite process.

Jan 1, 1984

By Edward F. Divers, J. Drew Potts

Powered dust-filtering helmets (dust helmets) have become increasingly prevalent in the underground mine environment in recent years. Many longwall operations use dust helmets to reduce the respirable dust exposures of miners required to work downwind of crusher, roof support and shearer operations. While continuous mining sections are usually less dusty, use of diesel equipment represents a new potential health problem. The U.S. Bureau of Mines recently conducted a study to determine the efficiency of a dust helmet on diesel-size particulate. Two underground evaluations were conducted on continuous mining sections that were using diesel haulage vehicles. Model No. AH21 Racal airstream helmets equipped with AS22-3 prefilters, AS23-3 main filters and AS60476 tyvek full-face seals were tested. Helmets were placed on mannequin heads and mounted in the ram car cabs. Andersen Model 298 (eight-stage) personal cascade impactors were used to sample air inside and outside of the helmet. Impactor stages 8 and the final filters were analyzed to determine submicrometer (0 - 0.93 µm) particle concentrations. Results from this study showed that the dust helmet was 94% (± 3% at 95% confidence level) efficient on submicrometer particles. Typically, very little coal dust is observed in the submicrometer size range, therefore, these particles were assumed to be from diesel exhaust. Results from this study indicate that proper use of the dust helmet on continuous mining sections that are using diesel haulage vehicles may be beneficial to the health of miners.

Jan 1, 1991

By K. Y. Haramy, B. T. Brady

A scale-invariant theory of the strength and deformability, of rock masses in static equilibrium and at incipient failure is proposed The theory provides a rationale, for designing structures in rock. This paper presents results of experiments conducted by the US Bureau of Mines and presents theoretical methods to determine and interpret the in situ strength of rock masses using the borehole shear tester.

Jan 1, 1996

By Dennis Molvik, Roberto J. Guardia, Brad Cowles, Rick Andrews, Robert A. Robinson

A 220-meter (m) segment of the Henderson/ ML King Combined Sewer Overflow(CSO) consists of two 1.8-meter-inside diameter (I.D.) pipe-jacked tunnels that pass beneath Interstate-5 and the BNSF and UPRR railroads. A seismic tomography survey was conducted to develop a 3-dimensional profile of the tunnel zone and better define potential obstructions. The tomography was conducted through three 11 cm high-density polyethylene (HDPE) pipes installed in a triangular pattern around the future tunnel alignments using horizontal directional drilling methods. The pipe-jacked tunnels have been successfully completed, thus permitting a comparison between the predicted obstructions and those actually encountered. The top HDPE tomography pipe was also used to monitor settlements with an experimental horizontal profiler above the advancing tunnels during construction and located two areas of ground loss beneath I-5 that were subsequently grouted.

Jan 1, 2005

By Guido Deissnann, Jennifer L. Kirkaldy, Stephan Kistinger, Carol M. Pettit

Contaminated mine drainage presents a potential hazard for aquatic ecosystems and groundwater resources. Reliable predictions of long-term developments in seepage quality are necessary to select reasonable decommissioning options and remediation measures for waste-rock heaps during mine closure and/or mining site rehabilitation to minimize future risks and environmental hazards. Extensive geochemical modeling work was used to assess the consequences of various remediation options for waste rock heaps at a former uranium mine in Eastern Germany. The predicted contaminant discharges are used for an assessment of long- term benefits of decommissioning alternatives to derive conclusions for sustainable remediation measures using risk-based cost/benefit analyses.

Jan 1, 2000

By Chester O. Ensign

The White Pine Mine is situated in the southwestern portion of the Keweenaw Peninsula of Upper Michigan approximately 6 miles south of Lake Superior (Fig. 1). It is east of the Porcupine Mountains in Ontonagon County. The ore deposit is about 70 miles southwest of the famous native copper deposits of the "Copper Country" lying northeast of Houghton. Geological conditions are different at every mine and create a special set of problems in dilution control. This paper is largely intended to describe the techniques applied in mine dilution control (grade control) at White Pine, and present results of the program. For necessary background information major geologic characteristics of the deposit, particularly those that exert control over the distribution of ore, are briefly discussed. Mining methods are described in considerable detail since applied grade control techniques are adapted to these.

Jan 1, 1964

By Rudy Rogers

When Gas hydrate formation rates have two steps: a nucleation induction step and an agglomeration step. Hydrate induction in distilled water is extremely slow because of lack of nucleating particles. Our laboratory found that synthetic anionic surfactants greatly improve both hydrate induction and agglomeration because the surfactant?s hydrophilic head absorbs water molecules and the hydrophobic tail absorbs hydrocarbon gas molecules, creating necessary nucleation sites. Vast hydrate deposits inhabit seafloors. What is the seafloor hydrate nucleating mechanism? We find that nano-particles of smectite clays (bentonite and nontronite) are hydrate-nucleating sites in sea-water-saturated, packed porous media, especially when trace quantities of anionic biosurfactants adsorb on the clay particles. Microbes and their bioproducts proliferate around seafloor gas hydrate accumulations. The seafloor microbe-mineral-hydrate synergy is explored in this paper. Keywords: gas hydrates, biosurfactants, crystal nucleation, smectites

Jan 1, 2008

By Brian Fulcher, Michael Bell, Shimi Tzobery, Werner Burger, John Bednarski

The Arrowhead Tunnels Project represents the final portion of a 70 km (44-mile) long water conveyance facility that will bring up to 28 m3/sec (1,000 ft3/sec) of water into Southern California. The 13 km (8-mile) tunneling project is well underway and consists of two, 5.8 m (19-foot) diameter TBM bores through extremely variable geological conditions. The tunnels lie near the base of the San Bernardino Mountains and several significant faults including the San Andreas Fault run within one kilometer (0.6 miles) of the tunnel alignment. Numerous other significant faults cross the tunnel alignment and water pressures in the tunnel have been recorded as high as 20 bar (300 psi). This paper describes some of the problems and challenges encountered and the solutions implemented to advance the two hybrid TBMs under conditions that ranged from hard rock with no water inflows to full-face granular material under 10-bar pressure and in excess of 32 l/sec (500 gpm) inflows. Due to the range and severity of ground and water conditions actually encountered, the Owner-Contractor-Designer team eventually found that adjusting the means and methods to be more responsive—virtually on a day-by-day basis—was needed to suit the conditions

Jan 1, 2007

By Dirk van Zyl

Pad construction costs can impact the overall economics of heap leach projects. Pad construction costs for single-and double-lined pads, using various designs, are listed for a typical small and large project. Double-lined pads are now more often required by regulatory agencies. Unless such designs reduce the risk of site specific contamination significantly, the extra costs cannot be justified from an economical viewpoint. Specific attention is given to the short project life (typically five years) of heap leach projects. A few numerical examples are presented to demonstrate the overall economic impacts of these costs on economic parameters.

Jan 1, 1990

By U. Paschedag, H. Bussmann

"Bucyrus manufactures the most comprehensive product portfolio of mining equipment worldwide. Its mission is to have a positive, lasting effect on our world. Bucyrus makes sustainable development a fundamental way of doing business through economic, environmental and social initiatives that support, educate and benefit our employees, customers, shareholders and other stakeholders. Our participation in GRI (Global Reporting Initiative), a network-based organization that has pioneered the most popular sustainability reporting framework will be discussed as well as examples will be given on each major field of engagement. Two examples from surface machinery are most fuel efficient haul trucks as well as the Highwall mining system which allows access to coal reserves which are lost not making use of this kind of system. Two examples from underground machinery are Bucyrus’ automated plow systems for the mining of medium and thin coal seams with minimum rock and Bucyrus’ intelligent CST drive system for high-powered armored face conveyors (AFCs) for efficient use of energy."

Jan 1, 2011

By Jack S. Watson, Rasika Nimkar, Robert M. Counce, Matthew Gordy, Patrick Zhang

Waste phosphatic clay presents a difficult disposal problem and a significant loss of P2O5. Recent developments make this study on the use of phosphatic clay as a feed material for H3PO4 production worthwhile. (a) New data from Florida Industrial and Phosphate Research Institute (FIPR) suggest that the Bclay^ waste can be effectively treated by improved solid separation coupled with flotation to produce feed material for recovering additional phosphate. (b) The use of BOLI Flowsheet^ provides capability to predict performance of aqueous-based processes for a range of possible operating conditions. Using the new FIPR data and BOLI Flowsheet^ enabled the design of a new process that can potentially extend the usefulness of current P2O5 ore deposits. Predictions using OLI Flowsheet were able to identify process conditions that effectively overcome the difficulty of high Mg content of phosphatic clay. Estimated manufacturing cost in the current study lead to valuation of the P2O5 content of the phosphatic clay recovered/utilized at 60 to 70% of that of the phosphate rock feed material currently used. Phosphatic clay should be considered as a valuable material that is currently given zero value. The new FIPR data and BOLI Flowsheet^ enables the design of a new process that can potentially extend the usefulness of current phosphate ore deposits by extending the fraction P2O5 of recovered

By William A. Vogely, Robert T. Deacon, Walter J. Mead

Oil and gas together are the most important energy sources consumed in the United States. In 1983, 67% of total energy consumption was represented by these two resources (43% was oil and 25% natural gas), while coal accounted for only 23% of U.S. energy use. All other sources (hydroelectric, nuclear, geothermal, wood and other waste products) accounted for only 10% (U.S. Department of Energy, 1983, p. 1). In this chapter we address the issue of regulation in the oil and natural gas sectors of the U.S. energy industry. In addition, we analyze the cartel characteristics of the Organization of Petroleum Exporting Countries (OPEC). If OPEC is an effective cartel, then U.S. oil as well as substitute energy prices, production, and consumption will be affected by cartel action. Further, as the nation learned in the 1970s, major changes in oil prices produced major disturbances in other sectors of the U.S. and world economies. Consequently, it is important to determine whether the roughly ten-fold increase in nominal prices that occurred in the 1970s was the result of cartel action, the result of normal economic forces adjusting to the fact that the world was running out of cheap oil, or some combination of the two. Furthermore, the presence of OPEC- associated oil price increases is related to regulations that were imposed on the energy sector during the decade of the 70s. THE RATIONALE FOR GOVERNMENT INTERVENTION Economists have traditionally judged the state of an economy to be efficient if it is impossible to improve the welfare of any one member of society without harming someone else. Any economy that satisfies this condition is said to be Pareto efficient, after the Italian economist Vilfredo Pareto who first gave rigorous attention to such questions (see Chapter 4.10). It is easy to see why an economy that fails to satisfy this condition could not be efficient; by definition, it would be possible to alter the allocation of resources in a way that improves everyone's welfare.' Much of the appeal of this weak efficiency criterion is that it avoids comparisons of levels of well being among different individuals. The cost of such generality, however, is that in any given economic system a wide array of different Pareto efficient states will typically be attainable. In the simple Robinson Cursoe economy of the undergraduate textbook, for example, efficiency could just as easily be attained in the case where most of the island's resources are owned by Friday as in the case where they are under Crusoe's control. However, the distribution of welfare among the two inhabitants would obviously be quite different in the two situations. Such equity issues cannot be settled on objective or scientific grounds. To decide which distribution of welfare is socially "best" an explicit value judgment is needed. It is useful to keep in mind the preceding distinction between efficiency and equity issues when analyzing the role of government in a market economy. Decentralized market processes will not necessarily result in a distribution of welfare that society considers just. For this reason a potential role for government lies in the redistribution of income among individuals. In some circumstances, however, market pro-

Jan 1, 1985

By Y. Guan

The adsorption of zinc species onto silica in ammonical solutions has been studied. Adsorption isotherms reveal that increasing adsorption occurs as the solution pH is made more alkaline. Fr-IR spectroscopy revealed that the adsorbed species is a zinc ammine complex.

Jan 1, 1993