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By Murali Gadde

Design of underground excavations in coal mines involves two major tasks: estimation of stresses and determination of rock mass strength. Owing to the complicated nature of rock mass, progress in its strength determination has lagged significantly compared to advancements in stress analysis techniques. Also, because of the impracticality of conducting field-scale strength tests, experimental approaches have very limited applicability in estimating rock mass strength. As a result, many empirical rock failure criteria have been developed based on observed performance of in situ rock structures. Unfortunately, all the popular rock mass strength criteria are based on data from large-scale ?isotropic? non-coal structures and thus can not be directly applied to coal mines. In this paper, an attempt has been made to adopt the popular Hoek-Brown (H-B) criterion for use with coal measure rocks. First, the H-B criterion is examined against laboratory triaxial strength data for different types of coal measure rocks. Then, procedures to estimate the H-B rock mass strength parameters relevant to coal measure rocks are suggested. Finally, a case-study has been given to show the usefulness of the proposed strength estimation approach.

Jan 1, 2007

By Paul F. Ziemkiewicz, Aaron Noble, Christopher R. Vass

The conventional rare earth element (REE) industry has historically sought to develop ore deposits where geologic processes have produced mineralized zones with commercially attractive REE concentrations. These deposits are extremely uncommon, particularly in the USA. Given the criticality of these materials and the need for sustainable domestic supply, the current research seeks to leverage other autogenous processes that lead to concentrated REE resources. One such process is the generation of acid mine drainage (AMD). AMD is very common in many coal mining districts and results from the exposure and oxidation of pyrite during mining. During the generation and migration of AMD, liberated sulfuric acid mobilizes several metal ions including REEs. Treatment of AMD is required under U.S.C §1251, the Clean Water Act, and often consists of neutralization, oxidation, and metal hydroxide precipitation. To investigate the deportment of REEs during this process, a field sampling campaign was undertaken, whereby the concentration of REEs in AMD and AMD precipitates was measured directly. In the nine sites evaluated in this study, the REE concentrations of the precipitates varied from 29 to 1286 ppm with an average of 517 ppm among the sampled sites. The individual elements were enriched compared with the associated bulk Northern Appalachian (NAPP) coal material by factors ranging from 3 to 15. Furthermore, the distribution of REEs in all precipitate samples favored the heavy REEs (HREEs) when compared with traditional REE ores. This research represents the first part of multi-part research endeavor to characterize, classify, and determine the practicality of refining REEs from AMD and its by-products.

By Paul F. Ziemkiewicz, Aaron Noble, Christopher R. Vass

The conventional rare earth element (REE) industry has historically sought to develop ore deposits where geologic processes have produced mineralized zones with commercially attractive REE concentrations. These deposits are extremely uncommon, particularly in the USA. Given the criticality of these materials and the need for sustainable domestic supply, the current research seeks to leverage other autogenous processes that lead to concentrated REE resources. One such process is the generation of acid mine drainage (AMD). AMD is very common in many coal mining districts and results from the exposure and oxidation of pyrite during mining. During the generation and migration of AMD, liberated sulfuric acid mobilizes several metal ions including REEs. Treatment of AMD is required under U.S.C §1251, the Clean Water Act, and often consists of neutralization, oxidation, and metal hydroxide precipitation. To investigate the deportment of REEs during this process, a field sampling campaign was undertaken, whereby the concentration of REEs in AMD and AMD precipitates was measured directly. In the nine sites evaluated in this study, the REE concentrations of the precipitates varied from 29 to 1286 ppm with an average of 517 ppm among the sampled sites. The individual elements were enriched compared with the associated bulk Northern Appalachian (NAPP) coal material by factors ranging from 3 to 15. Furthermore, the distribution of REEs in all precipitate samples favored the heavy REEs (HREEs) when compared with traditional REE ores. This research represents the first part of multi-part research endeavor to characterize, classify, and determine the practicality of refining REEs from AMD and its by-products.

By Alberto Eloy Anduze Nogueira

A pelotização é o método de aglomeração de minério que oferece o melhor custo benefício. No processo, é necessária a adição de um aglomerante para conseguir as propriedades desejadas. Entre estes, o cimento é um dos destaques pela facilidade e custo. A adição de pozolânicos no concreto na construção civil para o aumento da resistência é de longa data. Neste trabalho, se estuda o efeito da adição de 1% de SiO2 ou bentonita na mistura das pelotas autorredutoras. Realizam-se ensaios de compressão a frio, compressão após tratamento térmico 950°C, Teste de abrasão a quente, teste de quedas, além de difração de raios-X. Como resultados obteve-se um incremento da resistência a compressão a frio e a abrasão a quente com a adição da bentonita, porém com ambos pozolânicos tem-se uma perda de 50% na resistência a compressão após tratamento térmico a 950°C.

Aug 1, 2018

By Shanming He, Jinliang Wang, Xiaoming Wang, Chunfa Liao

Large amounts of manganese-rich slag were generated from smelting low-grade manganese ore containing high iron and high phosphorus in electric furnace or blast furnace, which contain 25–40 mass% Mn. This paper describes an efficient hydrometallurgical process for the utilization of high manganese slag instead of conventional usage of pyrometallurgical route for manganese recovery. Pressure acid leaching of manganese-rich slag using air as pressurized gas is studied systematically. The effects of mass ratio of manganese-rich slag to pyrite, concentration of sulfuric acid, leaching temperature, partial air pressure, leaching time, and liquid-solid (L/S) ratio on the separation of manganese with other main impurity components were investigated comprehensively. Under the following optimal process conditions, weight of manganese-rich slag powder,100 g; mass ratio of manganese-rich slag to pyrite, 20:1; sulfuric acid concentration of 140 g/L; air pressure of 0.6 MPa; leaching temperature of 140 °C; leaching time of 1 h; L/S of 7:1; ore size of 75–80 μm; and stirring rate of 600 rpm, the extraction rate of Mn reached 94%, and the dissolution percentage of Si, Al, and Fe are as low as 2%, 6%, and 10%, respectively. The leaching slurry presented a good solid-liquid separation characteristic. The silicic acid formed during sulfuric acid leaching manganese silicates was converted to filterable dehydrated SiO2 particles which precipitated in the residue under the condition of higher temperature with higher pressure. The effect of adding pyrite may be to reduced iron ions and decreased the output of iron hydroxide colloid and also reduced MnO2 to manganese sulfate in sulfuric acid leaching. Thus the formation possibility of colloid such as silica gel and iron hydroxide was decreased, and higher yield of manganese sulfate could be achieved.

By Shanming He, Jinliang Wang, Xiaoming Wang, Chunfa Liao

Large amounts of manganese-rich slag were generated from smelting low-grade manganese ore containing high iron and high phosphorus in electric furnace or blast furnace, which contain 25–40 mass% Mn. This paper describes an efficient hydrometallurgical process for the utilization of high manganese slag instead of conventional usage of pyrometallurgical route for manganese recovery. Pressure acid leaching of manganese-rich slag using air as pressurized gas is studied systematically. The effects of mass ratio of manganese-rich slag to pyrite, concentration of sulfuric acid, leaching temperature, partial air pressure, leaching time, and liquid-solid (L/S) ratio on the separation of manganese with other main impurity components were investigated comprehensively. Under the following optimal process conditions, weight of manganese-rich slag powder,100 g; mass ratio of manganese-rich slag to pyrite, 20:1; sulfuric acid concentration of 140 g/L; air pressure of 0.6 MPa; leaching temperature of 140 °C; leaching time of 1 h; L/S of 7:1; ore size of 75–80 μm; and stirring rate of 600 rpm, the extraction rate of Mn reached 94%, and the dissolution percentage of Si, Al, and Fe are as low as 2%, 6%, and 10%, respectively. The leaching slurry presented a good solid-liquid separation characteristic. The silicic acid formed during sulfuric acid leaching manganese silicates was converted to filterable dehydrated SiO2 particles which precipitated in the residue under the condition of higher temperature with higher pressure. The effect of adding pyrite may be to reduced iron ions and decreased the output of iron hydroxide colloid and also reduced MnO2 to manganese sulfate in sulfuric acid leaching. Thus the formation possibility of colloid such as silica gel and iron hydroxide was decreased, and higher yield of manganese sulfate could be achieved.

By Geraldo Lúcio de Faria

Amostras de aço baixo carbono (aço ABNT 1015) foram submetidas a tratamentos termoquímicos de cementação sólida fazendo-se uso de duas fontes distintas de carbono. Amostras do aço foram empacotadas em uma mistura de pós constituída pela fonte de carbono e cal hidratada e tratadas a 1000oC por 8 horas. As fontes avaliadas foram um tipo de carvão vegetal e uma remessa de coque de baixa qualidade metalúrgica. Realizados os tratamentos termoquímicos, as amostras cementadas foram devidamente caracterizadas por microscopia óptica e pela aplicação de ensaios de microdureza Vicker. Duas amostras cementadas foram, na sequência, submetidas a tratamentos térmicos de têmpera em água fazendo-se uso de duas temperaturas de austenitização (860ºC e 920ºC) e também foram caracterizadas. Observou-se que no processo de cementação sólida, a peça cementada com carvão vegetal apresentou melhores resultados do que a cementada com coque de baixa qualidade. Com carvão vegetal, a camada cementada se mostrou mais espessa e homogênea em todo o perímetro das amostras. A amostra cementada com o coque de baixa qualidade apresentou, além da menor espessura de camada cementada, heterogeneidades grosseiras no perímetro da peça.

Oct 30, 2017

By D. A. Rhys, M. Sieb, M. A. Prefontaine, C. L. Swanson, S. R. Frostad, H. Q. Smit

"Gold-silver mineralization at Red Mountain (1992 resource of 2.5 million tonnes grading 12.8 g/t Au and 38.1 g/t Ag) occurs within several discrete zones within a folded sequence of Middle to Late Triassic Triassic sedimentary rocks, Early Jurassic volcaniclastic and pyroclastic rocks, and Early Jurassic intrusions. Three phases of Early Jurassic sills and stocks collectively comprise the Golds/ide intrusions: (1) irregular bodies of medium-grained hornblende monzodiorite (Hillside porphyry); (2) hornblende-biotite + quartz porphyritic monzodiorite to quartz monzodiorite (Golds/ide porphyry; U-Pb zircon ages of 197.1 + 1.9 Ma); and (3) biotite porphyritic hornblende monzodiorite sills (Biotite porphyry). Contact breccias and igneous breccia dikes are common features of the Golds/ide intrusions. Chemical similarities and equivalent ages of volcanic rocks and intrusions, and the presence of intrusive clasts in volcanic rocks suggest that the intrusions are feeders to overlying volcanic units.Hydrothermal alteration affects all pre-Tertiary rocks on Red Mountain, including all phases of the Golds/ide intrusions. Several shallow-dipping alteration zones are developed sequentially above a propylitic quartz stockwork/molybdenum zone. These include: (1) sericite-quartz-pyrite alteration (pyrite-dominant alteration); (2) chlorite-K-feldspar-sericite-titanite alteration with disseminated and vein pyrrhotite (pyrrhotite-dominant alteration); and (3) brown to black tourmaline veins and K-feldspar-pyrite-titanite-actinolite alteration. Anomalous gold(> 0.3 g/t) mineralization is developed at the transition from the pyrite to the pyrrhotite dominant alteration over a > 1 km2 area. Within this anomalous zone, high-grade (3 g/t to 20 g/t Au) gold-silver mineralization occurs in 5 m to 29 m thick, semi-tabular pyrite + pyrrhotite stockworks with intense sericitic alteration and surrounding disseminated sphalerite + pyrrhotite.Stratigraphic, spatial and geochronologic relations and alteration zoning indicate that mineralization formed in a subvolcanic environment at the top of the Golds/ide intrusions and at the base of the Early Jurassic volcanic pile. The Golds/ide porphyry is interpreted to be the mineralizing intrusion. The alteration zoning, molybdenum-copper mineralized quartz stockworks, extensive Ksilicate and tourmaline alteration, and the relationship with a hypabyssal porphyritic intrusion show similarities to many porphyry systems."

Jan 1, 1995

By N. F. Sather

Results of comprehensive trace element analyses of samples of Illinois #5 and #6 seam coals and the unquenched ashes obtained from gasification of these coals in a Lurgi reactor are reported and discussed. Areas where additional background information is needed for assessment of the environmental impact of trace element emissions from coal gasification are identified.

Jan 1, 1976

[This Report represents the culmination of work perfomed under Contract No. .,JG1551A8 for the U.S. Bureau of Mine.The &apos;.:o-< embeded a site evaluation, engineering E:-y- ,, esign, and preparation of specifications for construction of a Transport Research 7 :4 (HTRF)The HTRF is designed as a research facility J evaluate the hydraulic transport of large lump coal at a prototype ;e scale. The HTRF is to be constructed and operated by the Pittsburgh and Safety Research Center of ;. re U.-AN a*, their Bruceton, Pennsylvania test center. In terms of technical capability, the HTRF will have transport pipeline:: of -, twelve-, and eighteen-inch diameter _&apos; with supporting coal handling n , water forage a.^ &apos;d conveyance, mixing, pumping, and dewatering equipment, plus instrumentation and controls. Maximum design velocity 13 20 ft/sec.; solids concentration, by, volume, will; 1 be a maximum-- of sixty, percent. Each test loop is designed to accommodate solids of up to one-third the diameter e - of the pine. The Final Report Pr.-&apos;I-rents information of t HTHF,. including the site evaluation, design criteria, a description of the a description of the procedure to be used for operation of the facility, an estimate of the cost to construct the f^Cilit:r, 1 p el_~lli.&apos;iU construe`, icn Schedule, and a construction suicJ_iicaT.l_ccn&apos;. T e c011SLr?Jc&apos;.ion soecl_ i.on _ccnta_i:s technic.&apos;..i re7,uir: (-n`,s for !&apos;urr1S~ &apos;~latcr..al. and ec-uipr,ent for :":C1 C_`:_C ti on of ti,_ H ice&apos; u:&apos;.:i ._II u s(-.6 for ~.Iir: .3!7 soliciting bids. `.l_o included n cc&apos;;,art_- c?r~.air sV:et..: :s ^nd rr^.?]

Jan 1, 1976

By W. Wittke

SUMMARY: Geotechnical problems often lead to an increase of construction time and costs for large highway and railway projects. Some reasons, which have led to failures and thus to a delay of construction works as well as to increasing costs, are demonstrated by means of case histories, in which the author was involved as expert or planner. Proposals are made how to identify the reasons and to avoid repetitions. ZUSAMMENFASSUNG: Bei Großprojekten der Verkehrsinfrastruktur stehen häufig geotechnische Aufgabenstellungen im Vordergrund. Wegen geotechnischer Probleme kam und kommt es häufig zu Termin- und Kostenüberschreitungen. Anhand einiger Beispiele, bei denen der Autor als Gutachter und Planer beteiligt war, wird gezeigt, welche Ursachen zu Schadensfällen und damit auch zu Termin- und Kostenüberschreitungen geführt haben. Es werden Hinweise und Anregungen gegeben, wie die Ursachen erkannt und Wiederholungen von Schadensfällen vermieden werden können. RÉSUMÉ: À grands projets de l&apos;infrastructure de la circulation, souvent des tâches géotechniques sont au premier plan. Par suite de problèmes géotechniques, souvent des dates et frais ont été dépassés. Au moyen de quelques exemples, à lesquels l&apos;auteur participait comme expert et planificateur, les causes sont mises en vue qui menaient à des cas de dommage et par cela aussi à des dépassements de dates et frais. Des indications et suggestions sont données pour s&apos;apercevoir des causes et éviter des répétitions de cas de dommages.

Jan 1, 2003

By Schlanger H. P

A theoretical model for gas outbursts in underground coal mines is as follows. An outburst is the structural failure ofcoal due to excess stress resulting from body forces caused by gas pressure gradients. These body forces influence the stability of a mine face in the same manner that gravitational body forces affect the stability of the roof of a mine. The magnitude ofthese body forces can be appreciated when it is realized that for an average density coal, the gravitational body force is equal in magnitude to the force from a gas flow with a pressure gradient of 14 kPa m-I. Gas pressure gradients and the resultant stresses within a seam can be calculated with numerical methods. Thus, providing the necessary parameters can be measured or estimated, in principle the theory can be applied to compare the outburst risk of various mining arrangements.

Jan 1, 1985

By G. G. Barbante

The oxidation behaviour of selenide matte with a substantial Cu content and low Ag differs significantly from that of high-Ag matte. Low-Ag selenide mattes display a large oxygen solubility and the upper boundary of the miscibility gap in the Ag-Cu-Se-O system is depressed to quite low Se contents. As a result, the formation of Ag metal is considerably delayed. The oxidised selenide matte, low in Se and with a relatively high oxygen content, has previously been termed oxymelt. With further oxidation, its composition enters the misciblity gap and crude Ag is formed. The sodium silicate slag captures very little of the SeO2 and the dissolved Ag2O(s) content of the slag is relatively small, with a Raoultian activity coefficient of 0.57. This value was found to be independent of the slag's Cu2O content

Jun 19, 1905

By Robert Hopler

A blast caused the destruction of a bridge and loaded freight train and the death of three men, near Chattanooga, Tenn., on May 16, 1907. The blast and its disastrous effect has been described by Mr. Hunter McDonald, M. Am. Soc. C. E., in a paper read before the Engineering Association of the South and reprinted in the Proceedings of the Association for April-June, 1907. The excessive damage was so largely due to coincidence and wreckage of the bridge and train so complete that the incident is worthy of notice.

Jan 1, 2008

By S. D. Zhang

The first reinforced earth railway bridge abutment in China has been successfully constructed of September, 1985 under the supervision of the Reinforced Earth Researth Group of Shanghai Institute of Railway Technology. In order to verify the reliability of the designed structure and its behaviuors, the 1:10 reduced scale model tests in laboratory and field tests on the actual structure during construction were proceeded. Various loads of different positions were charged, the vertical and lateral earth pressure in the filling soil, the stresses developed in the reinforcements, and the deformations of the models or the actual structure were recorded in those tests. The behaviors recorded are presented and discussed in this paper.

Jan 1, 2010

By Yuanbing Ling

Keywords: Calcium sulfate, Sulfuric acid, Phase transformations, Thermodynamic analysis As part of a boarder research project, seeking the development of a cost-effective process for direct production of the high value material, -calcium sulfate hemihydrate, from sulfuric acid at atmospheric as opposed to elevated pressure conditions, the fundamental work presented here has been undertaken. This includes experimental monitoring of phase transformation reactions and thermodynamic analysis of the relationships among the various phases, namely, calcium sulfate dihydrate, hemihydrate and anhydrite in aqueous sulfuric acid solution at temperatures ranging from 20oC to boiling point.

Jan 1, 2004

By Marco D. Boscardin

Control and mitigation of building response to construction activities are assuming a greater role in design decisions for underground construction. Alternatives for controlling building response have multiplied with the continued development of ground modification methods, better control of construction activities that cause ground movements, and increased understanding of building behavior and response. This paper describes approaches to estimating building response to construction-related ground displacements caused by adjacent excavation and highlights the discussion with several case history examples. Examples discussed includes experiences with two, seven-story historic structures, supported by timber piles with granite block pile caps, which were underpinned in preparation for ground-freezing ground stabilization and tunnel construction beneath the buildings. The elevation of each building column was monitored and elevation adjustments were actively performed during construction. The second example examines the performance of a slurry wall braced cut, 45 to 50 feet deep penetrating through a stiff crust into a soft clay layer and associated building response. This cut was immediately adjacent to two, approximately 15-story office buildings, which were supported by deep foundations founded in the stiff crust.

Jan 1, 2003

By P. A. Cox

Guidelines are provided for the design of explosion-proof electrical enclosures that will meet MSHA certification requirements according to Part 18, Title 30, of the Code of Federal Regulations, and fulfill their intended service underground. The guide covers only those aspects of design which affect enclosure strength, ruggedness, endurance and flame path, i. e., the enclosure ability to properly contain an internal explosion. Internal static and explosion pressures, external impact and thermal heating load are treated as well as the proper selection of materials and welding procedures.

Jan 1, 1985

By Daniel H. McClain

A unique partnership between the Colorado Mine Safety and Training Program (CMSTP), the Colorado Rock Products Association (CRPA) and the Higher Education and Advanced Technology (HEAT)Center resulted in a video CD-ROM training program for new miners entering the aggregate industry. Cooperation from everyone involved, including the U.S. Mine Safety and Health Administration (MSHA),made this the product against which other training materials in the mining industry will be measured in the 21stcentury. This product’s versatility and wide application make it a tool that is as critical to a mine’s success as any earthmoving machine. The state and federal grant money involved allows this product to be affordable to small operators and independent contractors. The quality of this two CD-ROM set rivals any commercially made CD-ROM training.

Jan 1, 2003

By Bráulio Salumão de Oliveira

A participação do petróleo e gás natural na matriz energética mundial aumenta gradativamente a cada ano. Em estimativas para as próximas duas décadas, tais fontes continuarão a figurar entre as principais na participação em suprir a demanda por energia mundial. Para que seja tecnicamente e economicamente viável a exploração destes recursos, são necessários utilizar produtos e processos inovadores que, por sua vez, exigem evolução da pesquisa e desenvolvimento de novos materiais e processos. Este estudo objetivou analisar o desenvolvimento tecnológico de ligas ferrosas para os produtos tubulares utilizados nesse mercado, através da elaboração de indicadores a partir de documentos de patentes indexados na base Derwent Innovations Index entre 1995 e 2014. Foram elaborados indicadores de evolução temporal, de identificação dos elementos de liga, das tecnologias em processamento dos produtos e das propriedades requeridas além de comparativos entre principais desenvolvedores e seus mercados de interesse. O número de documentos de patentes sobre o tema aumentou significativamente durante o período estudado. Foram notados países com destaque no número de depósitos de patentes, porém com pouca expressão de pedidos fora de seu território. Os principais titulares são empresas japonesas embora a China tenha apresentado a maior tendência de crescimento de depósitos no tema.

Aug 16, 2017