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By P. Tsang

To gain insight into the current status of pillar design practice in the underground coal mines of United States, a survey has been undertaken in the late 1993 and early 1994. A total of 552 room-and-pillar mines and 75 longwall mines have been surveyed to collect general, geological and mine plan information. The collected information are critically analyzed with special emphasis on the pillar design criteria adopted in these mines. A safety factor analysis has also been carried out for the pillars in room-and -pillar mines.

Jan 1, 1995

By Arnold E. Lamm

The degree of economic, progress of a nation is measured by its possession and use of energy, sources. The future of coal in the West hinges on its ability to participate and grow in the energy market. A source of energy is, in the long run, only as good as the ability of the industry to develop its reserves economically. The economic development of the tremendous coal reserves, literally hundreds of billions of tons of coal in the States of Colorado, Utah, Wyoming, Montana, New Mexico, and Arizona, poses a very real question in the light of the known mining technology of our day. Basically in America today, coal is mined from the earth either by the strip mine or underground mine method; in the West, the large long-term, contracts now in force with utilities are mostly from coal mines utilizing the strip mine method. However, the preponderance of the known coal reserves of the West are located deep underground and will have to be mined by the various; underground mining processes. The problems encountered in the West with regard to underground mining vary from state to state but, on the whole, do not present what might be considered a miner's bonanza. I do not mean to' infer that the underground coal of the West is unmineable, but I do want to emphasize that the tremendous reserve figures do not present a true picture in the light of present day technology.

Jan 1, 1965

By Y. Topkaya, R. E. Johnson, D. Buttinelli, B. R. Palmer, A. Geveci, L. Stoppa, C. Lupi, F. Pochetti

Representative samples of a composite mixture of three typical Cu/Zn complex sulphide ores, namely Black-, Yellow- and Altered-ore, from the Cayeli deposit in Turkey, were used for leaching tests in 2.2 M FeCl3, or 1 M CuC12-2 M NaCl solution in the temperature range from 313 K to 363 K (40O to 90O C), with and without the presence of an organic solvent for elemental sulphur, such as CCl4. The leaching rates of copper and zinc were quite high, as expected, in FeCl3 solution and complete recovery of both metals was obtained at the highest temperature when the solvent was present. However in CuC1, solution, extraction yields of the order of 95% only for Cu and Zn were achieved and the positive effect of the solvent was not clearly shown. The kinetics curves of Cu leaching by FeCl3 indicated a model of reaction rate depending on the particle surface, as in a chemically controlled reaction, in tests with the presence of CCl4. Without the solvent, or in CuCl2 media, the model of the diffusion controlled reaction seemed to prevail. Values of apparent activation energy, in both of the leaching processes, were determined and compared with those reported in literature.

Jan 1, 1993

By F. J. Klingler, K. M. Swaffar, M. M. Rabbaig

The Detroit Water and Sewerage Department has undertaken a $1.2 billion effort to capture and treat combined sewage overflows from various outfalls along the Detroit and Rouge Rivers in Detroit, Michigan. This program is planned to include a 455,000 m3 (120 million gallon) storage and treatment tunnel which will capture overflows from 19 outfalls along the Rouge River. The tunnel is currently in the conceptual design phase, with the bid date planned for mid-year in 2001,and completion planned for August 2005. The total design and construction cost is currently estimated to be approximately $450 million. Current concepts are for the storage and transport tunnel will be 6.1 m (20feet) in finished diameter, with a total alignment length of approximately 12,200 m(40,000 feet). The main tunnel will extend through the Traverse and Antrim Shalerock formations, while approximately 5,500 m (18,000 feet) of various diameter connecting tunnel will extend through both rock and soft ground. The project will include a total of 10 drop shafts, 13 riser shafts, various connecting structures, and a 455,000 m3/day (20 mgd) pumping station. This paper will present a discussion of the design philosophy, subsurface conditions, the various planned components, and the expected design and construction considerations for the proposed Upper Rouge Combined Sewage Overflow Tunnel.

Jan 1, 1999

By John H. Hollomon

In a recent paper,' a very early suggestion by Ludwik2 concerning the nature of the mechanical behavior of metals has becn reexamined and extended. In essence it was suggested that there exists, at least under certain conditions, a mechanical equation of state; that the stress required for flow depends upon the instantaneous values of the strain, strain rate, and temperature, and not upon their past values. It is proposed that under these circumstances thc stress does not depend upon past history of these variables, but is like the temperature of a gas that depends only upon the instantaneous values of the pressure and volume. This notion has not been applied to present-day studies of metals, though it is especially applicable to the study of creep. It is the purpose of this paper to analyze the significance and possible range of applicability of this idea and to determine how it influences the accepted ideas concerning creep. Stress-strain Relations It is wcll known that the stress-strain curves of metals are influenced by both train rate and temperature. For a fixed strain rate and temperature there is associated with each metal a stress-strain curve. If either the strain rate or temperature is changed a new stress-strain curve will be characteristic (Fig. I). A much more genera1 relation between the effects of these variables is possible, however. Consider the stress-strain curves of Fig. I determined at

Jan 1, 1947

By John H. Hollomon

In a recent paper,' a very early suggestion by Ludwik2 concerning the nature of the mechanical behavior of metals has becn reexamined and extended. In essence it was suggested that there exists, at least under certain conditions, a mechanical equation of state; that the stress required for flow depends upon the instantaneous values of the strain, strain rate, and temperature, and not upon their past values. It is proposed that under these circumstances thc stress does not depend upon past history of these variables, but is like the temperature of a gas that depends only upon the instantaneous values of the pressure and volume. This notion has not been applied to present-day studies of metals, though it is especially applicable to the study of creep. It is the purpose of this paper to analyze the significance and possible range of applicability of this idea and to determine how it influences the accepted ideas concerning creep. Stress-strain Relations It is wcll known that the stress-strain curves of metals are influenced by both train rate and temperature. For a fixed strain rate and temperature there is associated with each metal a stress-strain curve. If either the strain rate or temperature is changed a new stress-strain curve will be characteristic (Fig. I). A much more genera1 relation between the effects of these variables is possible, however. Consider the stress-strain curves of Fig. I determined at

Jan 1, 1947

By Gus L. Maciula

Although I will briefly review the current status of coal slurry pipeline technology, I wish to make it clear that this is not a technical paper. It is intended instead to review the current situation on energy resources and requirements, and the environmental, political and economic considerations that mandate a serious consideration of Slurry pipelines as a viable mode of coal transportation into the Georgia and Florida markets. In order to more fully appreciate our current energy situation, it will be helpful to go back a few years and review the evolution of our so-called energy "problem." It was about two decades ago that the first and only major natural gas transmission pipeline was built into the State of Florida by Florida Gas Company. This line was conceived and implemented during a time when gas was plentiful and cheap, and it appeared at that time that unlimited gas reserves were continually being discovered, thus assuring the availability of a clean, cheap fuel and the ,viability of the pipeline system. One of the major factors justifying the original pipeline construction as well as subsequent expansions was a series of long-term commitments under which Florida Gas transported natural gas owned by electric utilities for use as boiler fuel. Thus for the past 20 years Florida industry, commerce, and domestic fuel requirements have been met either directly or indirectly through clean, cheap natural gas which would not have been otherwise available without the pipeline system.

Jan 1, 1978

By Rob Kelso

The PISCES Goals ? To conduct research and develop programs to enable and promote planetary surface exploration ? To host international tests and technology demonstrations at the PISCES Test Site. ? To promote STEM education, inspiring students by connecting Hawaiian culture to space exploration and settlement. - economic and workforce development ? To involve the commercial sector, spinning off technologies to help the local Hawaiian economy. ? To develop a full-scale, technically valid, analog lunar/Martian outpost on Hawai`i Island.

May 1, 2013

By Michael Gobla

"Since 1994 the Bureau of Reclamation (BOR) has used risk analysis to evaluate dams. Risk considers both the likelihood of failure and the expected consequences should failure occur. Risk analysis relies on the detailed formulation and critical analysis of all possible potential failure modes. Potential failure modes are formulated by describing the sequence of events that must occur to result in failure, where failure is defined as the uncontrolled release of the impounded reservoir. Failure occurs in response to loadings such as water seepage through a dam (static forces), shaking from an earthquake (dynamic forces), sudden flood inflows (hydrologic forces), or accidental overfilling (operational errors). Reclamation has, to a limited extent, applied risk analysis to inactive and abandoned mines to evaluate tailings dams, pit lakes and flooded underground mines. Case histories of potential failure mode analysis, as applied to mine impounded water, illustrate what critical technical information is needed to determine if failure is likely, what the consequences of failure are likely to be, and what are the highest risks that should be addressed first.IntroductionImpounded water and high water content wastes at mining and industrial processing sites are potential threats to public safety and the environment. Recent failures such as the TVA Kingston flyash impoundment failure in Tennessee in 2008 (4.1 million m3 or 5.4 million cu yd) release, the Mt. Poly Tailings Dam failure in British Columbia in 2014 (4.4 million m3 or 5.8 million cu yd) release, and the Samarco Fundao Tailings Dam failure in Brazil in 2015 (59 millon m3 or 78 million cu yd) release have renewed attention to this issue. Potential risks from impounded water at mining and industrial sites originate not only from tailing dams, but also from water in process ponds and conveyance pipelines, sediment retention dams, water retention dams, mine pit lakes and flooded underground mine workings.Conventional water retaining dams also have a record of failure. Notable examples of failure include Vajont Dam in Italy in 1963 (2,600 lives lost), Banqiao and Shimantan Dams in China in 1975 (171,000 lives lost), and Machhu-II Dam in India (10,000 lives lost). After the 1976 Teton Dam failure in Idaho, the U.S. Bureau of Reclamation (BOR) established a Dam Safety Program. By 1984, the agency developed and began using risk analysis methods. BOR operates and maintains an inventory of hundreds of aging dams which were designed and constructed over a period of 100 years. Many of these facilities were designed and constructed prior to the development and adaptation of modern soil mechanics in dam engineering. Diligent observational monitoring, detailed site investigations and the application of risk evaluation to the BOR dam inventory has identified many deficiencies resulting in significant demands on available funding for remediation efforts. The application of risk analysis has allowed the agency to rank sites by risk. By giving priority of remedial efforts to high-risk sites, significant improvements to dam safety have been achieved."

Dec 1, 2016

By Jerry M. Eyster

The Bush Administration is committed to reducing emissions from existing power plants Candidate George W. Bush said: The key to reducing emissions from older power plants on the federal level is to cap emissions on a level that makes sense?. And harness the power of the market place and provide economic incentives to produce better environmental results. I would want to make sure that any program we pursue does not result in excessive and unnecessary increases in electric bills.

Jan 1, 2002

By W. F. Chiao

With the application of dislocation damping theory an attempt was made to determine whether the generation and extension of dislocations is inherently more difficult in a brittle steel than in a ductile steel. A ductile steel was compared with a brittle stee1 by simultaneously measuring the ultrasonic attenuation and velocity during tensile test, and the density of free dislocations and their mean loop length were then calculated as a function of strain. The results showed that in the ductile steel there was always a large generation of dislocations and great extension of loop length occurring at some stage within the early plastic region. In contrast, the brittle steel showed very little or no such sudden changes in dislocation dynamic states after the onset of plastic deformation. Furthermore, a strong temperature dependence of dislocation dynamic states was also observed in the ductile steel and a hypothesis was suggested that a thermally activated process of dislocation rearrangement could occur at higher deformation temperatures. The activation energy of dislocation rearrangement at room temperature was estimated as about 2030 cal per mole.C. DUCTILITY is an indispensible property in the application of engineering materials, especially steel. During the past two decades the theoretical and experimental approach to the understanding of flow and fracture of metals has been constantly undergoing changes and progress." while the fracture behavior of metals can be influenced by many factors such as chemical Composition,3 second-phase particle mor-phology,4 and dislocation arrangement,5 it is now a general belief that the fundamental understanding of the ductile-brittle fracture phenomena of solid materials must stem from the study of dislocation dv-namics developed under stress conditions.6,7 Most of the traditional ductility tests, such as Charpy impact test, slow bend test, and tensile fracture test, cannot by themselves reveal directly the mechanisms of ductile to brittle transition of materials. In the experimental investigation of tensile ductility it would be ideal to be able to study directly the dynamics of dis-locations in a bulk specimen during the process of deformation. Since the ultrasonic pulse technique is the only satisfactory method for studying dislocations and the fine details of deformation characteristics in metals in the course of a tensile test, it would appear that a comparative study of ultrasonic attenuation changes during tensile tests of metallic materials exhibiting different ductility might be very informative. So far no work comparable to this study has appeared in the literature. Recent progress in both theory and experiment has indicated the feasibility of studying the dislocation mechanisms of ductility behaviors by ultrasonic measurements during tensile test. Granato and Lucke8 have developed a quantitative theory that enables the calculation of dislocation density and their average loop length from the measurements of ultrasonic attenuation and velocity, and several investigators, including Chiao and Gordon,9'10 have shown that simultaneous ultrasonic measurements can be successfully made during a tensile test. Furthermore, many investigators11-13 have repeatedly proposed in the past several decades that deformation and fracture are mutually self-exclusive, and that the ability or inability of a material to deform plastically, i.e., to generate dislocations, is a major factor in determining whether the material will be ductile or brittle. Thus, in the present work an attempt was made to determine whether the generation and extension of dislocations is inherently more difficult in a brittle steel than in a ductile steel. This article is principally concerned with the study of the relation between the propagation of ultrasonic waves and tensile deformation in a steel series which displays quite different toughness at room tempera-turk. changes in attenuation and velocity of ultrasonic waves have been measured as a function of strain during the deformation process. The results have been interpreted in terms of the vibrating string model for dislocation damping as developed by Granato and Lucke, and it has been found that some of the more subtle predications of the model are in good agreement with the experiments. This would be especially meaningful because most of the previous experiments in testfying the model were carried out with single crystals of high-purity materials and little work has been done with polycrystalline steel alloys. EXPERIMENTAL PROCEDURES AND RESULTS Specimen Materials. The tensile specimens used throughout this experiment were of two compositions selected from a series of Fe-Mo-0.77 pct Mn-0.22 pct C steels prepared for a ductile-brittle fracture transition study. One steel contains 0.21 pct Mo and the other 1.03 pct Mo. These two compositions were chosen for the present study because they possess quite different toughness properties at room temperature. The 0.21 pct Mo steel is quite ductile while the 1.03 pct Mo steel is rather brittle, as measured by the standard Charpy impact test. The alloys had been prepared by vacuum induction melting and chill casting in steel molds. The ingots were hammer-forged into 1/2-in.-sq bars from which tensile specimen blanks were cut. These blanks were first normalized under argon atmosphere at 1700°F and then reaus-tenitized and isothermally transformed at 1050°F to a bainitic microstructure. The chemical compositions, heat treatments, hardness measurements, and Charpy transition temperatures of the two steels are listed in Table I.

Jan 1, 1970

By Fawad S. Niazi

Analysis of deep foundations in terms of axial capacity has been a topic of great interest in the soil-structure interaction problems. Soil behavior is governed by a series of complex stress-strain changes that occur during pile installation and subsequent loading. Owing to the difficulties and uncertainties on the basis of the soil strength-deformation characteristics, one of the most frequently followed design practice is to refer to the formulae correlating directly the pile axial capacity components of unit base resistance (qb) and unit shaft resistance (fp) to the data collected from cone penetration test (CPT), i.e. to the tip stress (qc or more proper qt), sleeve friction (fs), and shoulder pore water pressure (u2). The elementary basis for such formulations has been the idea of considering cone penetrometer as a mini-pile foundation. This has resulted in plethora of correlative relationships in the past over 60 years. Such correlations, although empirical, have been worked out on the basis of load test results from both instrumented and un-instrumented full scale piles and are able to accommodate many important variables. A quick review of the evolution process and development of such design formulations is presented with a view to propose recommendations for future research directions, where the latest version of CPT i.e. seismic piezocone test (SCPTu) can be used to advance from capacitysingularity to the complete axial pile load–displacement (Q–w) response.

Jan 1, 2013

By Milner SC

Four quartz latite rheoignimbrite units (units I to IV) mapped in the Goboboseb Mountains have been traced to their eruptive source, the Messum intrusive complex; this is a complex multistage ring structure (18 km diameter) with well defined gabbroic, monzonitic, and syenitic intrusive phases, and a central ring zone containing mixed rhyolitic to latitic agglomerates. Three of the four quartz latite units are correlated with the upper and lower (2 units) Springbok quartz latites outcropping some 90-130 km north of McIsum. This implies minimum volumes of 300-500 km for wits I and III (Lower Springbok) and 2200-2600 km for unit IV (Upper Springbok). This latter unit is still ti 300 m thick at its outcrop limit, some 130 km from Messum. Each of the four units represents single cooling units. Lithologically, each can be divided into three zones: A basal, dark grey to black flinty or glassy zone, often with highly attenuated fiamme (ressembling flow banding); a central massive and strongly recrystallised zone; and an upper variable zone which exhibit breccias, contorted flow banding, and amygdaloidal to pumiceous clasts. Their overall characteristics tend to be intermediate between ash flows and lava flows. The rheoignimbrites are interpreted as the oproducts of dense, high temperature (950¦-1100 C) ash flows which underwent rheomorphism and lava-like flow prior to their final cooling.These large scale eruptions are related to the initial rifting of Africa and S. America, possiby in response to a major hot spot.

Jan 1, 1990

By K. Oishi

We have developed a 76Cu-3Si-21Zn alloy "ECOBRASS®" containing no lead. When 3% Si is added to a 78Cu-22Zn alloy, kappa and gamma phases participate uniformly in the alpha matrix. When being machined, stress concentrates on these hard phases, namely kappa and gamma, and thereby lowering the required cutting force and yielding segmentalized chips without lubricant. Kappa and gamma phases transform into beta phase under high temperature, which makes it easier to extrude and/or forge the alloy. When 0.08% P and 50 ppm Zr are co-added, the grains of ECOBRASS® castings are refined significantly to become as small as several dozens of micrometers. The grain refinement by the co-addition of P and Zr improves castability, tensile strength and elongation of ECOBRASS® castings. Meanwhile, the lead leachate from an ECOBRASS® water meter, field-tested in pH 6.8 drinking water for one year, was less than 5 ppb without correction. No indication of dezincification corrosion was observed, either. ECOBRASS® is equally suitable for rods, forgings and castings, and makes it possible to produce a complete set of plumbing parts (valves, faucets, etc.) by its own. This way, not only improving recyclability, ECOBRASS® also realizes size and weight reduction due to its good corrosion resistance and high strength.

Jan 1, 2007

By E. M. Wilde

Through the USGS's National Coal Availability program, coal resource appraisals have been completed for three 7.5-minute quadrangles (Willow Crossing, Colstrip East, Colstrip SW) in the Powder River Basin area of southeastern Montana. Available coal reserves (original reserves minus tonnages affected by current restrictions) vary from 44 to 70 percent of the original reserves. Major restrictions impacting each area also vary. In each area, one or two beds contain most of the reserves, but up to eleven beds contain available coal. The main beds in completed studies are the Knobloch, Rosebud, Sawyer and Flowers-Goodale. Three additional areas (six 7.5-minute quadrangles) are in preparation.

Jan 1, 2001

By Carlos M. Fontes Vieira, Ruben J. Sanchez Rodriguez, Carlos E. Gomes Ribeiro

"The worldwide demand for ornamental stones in building construction is motivating the use of their wastes, generated during fabrication, to produce compound stones. This work has as its objective to investigate the production of an ornamental compound marble (OCM) under vacuum and compression processing of a polyester matrix composite with addition of marble waste as load and as filler. Square OCM composite plates were subjected to compression and flexural mechanical tests. Samples were analyzed to obtain the density and water absorption. The OCM composites presented properties within the expected range of an artificial stone.IntroductionMarble is a limestone, composed mainly of calcite, more or less crystallized by metamorphism that ranges from granular to compact in texture. It has a density 2.7 g/cm3 and its porosity is approximately 0.4%. The UNI 8458 standard defined marble as: ""every crystalline rock constituted mainly by minerals with a Mohs hardness equal to 3-4"". In marble production around70 - 75% of whole extract material is lost in byproducts generation [1,2].In function of large volume of residues generated, the ornamental stones industry has attracted ever more the attention of environmentalists [3].Actually the marble can be pulverized to obtain calcium carbonate for industrial applications. It is also possible to obtain a thinner powder to produce concretes [l]. Some authors study the use of stone residues in concrete mortars and ceramic bricks, getting better properties to these materials [3,4].The marble residues can be also used in engineered stones, or ''agglomerated"" stones, production. The most common engineered stones in the market consist, like a polymer concretes, in polymer matrix composites incorporating petreous components. In the formulation of the engineered stones, the particulate or granular petreous components are the result of fragmentation or trituration processes to which natural stones were submitted to [ 5]."

Jan 1, 2014

By Rufus J. Foster

During the discussion on the Preparation and Utilization of Sniall Sizes of Anthracite (page 613 of present volume), several inquiries were made concerning the use of the McClave grate, which was mentioned by Mr. Coxe as having proved satisfactory in the generation of steam at his collieries, and also at a large number of industrial estal)lishments in Scranton and elsewhere. For a more satisfactory repIy to such inquiries than could be furnished in the oral discussion, I have prepared the following paper to be included in the published proceedings. And, as the use of the fuel under consideration necessarily requires the employment of a blower to change the fire, from a condition giving an incandescent radiant heat only to one giving a hot gaseoua flame as well, I shall add a description of the McClave Argand blower and its method of action. The grate and blower combined form a complete and effective system fcr burning small fuels, such as anthracite culm, birdseye, buckwheat, bituminous slack, etc., in boiler and other furnaces; while the grate alone is now extensively used with the larger sizes of hard and soft coal in furnaces where blast is riot required. Fig. 1 is a view of the RlcClave grate as built in two sections. It is constructed on the principle best approved by practice to prevent warping and burning out; that is, it presents no long lines of

Jan 1, 1892

By D. W. Park

Longwall mining is popular in underground coal production in the United States due to higher production rates and safety concerns. Because of the extreme complexity, it is necessary to plan an adequate design to achieve a safe and efficient working place. The proper sizes of yield and abutment pillars and panels can be determined by simulation using numerical modeling techniques. By means of three-dimensional modeling, stresses to be imposed on the pillars, panels, gob, and powered supports can be analyzed. In this study, an initial three-dimensional finite element model was developed and then modified into four different models. Using these models, the numerical outputs of distributed stresses on three different sizes of yield pillars, three different sizes of panels, and two different sizes of abutment pillars were compared and analyzed to determine the most adequate pillar and panel sizes. Progressive failure theory based on the Hoek and Brown failure criterion was used to determine redistribution of stresses in the yielded and failed areas in the longwall mine.

Jan 1, 1992

By S. E. Clay, G. P. Martins, P. R. Taylor

A grain model for gas-solid reactions in cylindrical pellets is formulated and solved numerically. The numerical solution demonstrates when it is safe to assume either a thin disk or a long cylinder geometry, and when the more general two dimensional geometry must be used. The numerical solution also demonstrates the solution of a two-dimensional moving boundary problem (i.e., when the reaction is diffusion controlled and the ratio of the height to diameter dictates two dimensions).

Jan 1, 1986

By G. Belardi, N. Sheau, P. Plescia, F. Veglio

A study was conducted to assess a new wet gravity-separation machine, identified as the Multi-Gravity Separator(MGS). Chromite fines, obained from an Albanian chromite and olivine ore and containing 23% Cr2O3 and 18% SiO2, were used in the study. The first step was to determine the influence of various operating parameters. The study indicated that the most important variables for the MGS are rotational speed, tilt angle and shake amplitude. The best treatment conditions for the ore were then identified by investigating a series of circuits designed to produce a marketable product. In open circuit, a concentrate containing 50% CI-203 was obtained with a recovery of 72%.

Jan 1, 1996