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By T. C. Sandford

Thermal conductivity measurements of intact rock specimens do not reflect the effects of natural rock discontinuities, and large scale insitu tests are location specific and costly. To allow extrapolation of laboratory measurements to rock masses with discontinuities, the effects of discontinuities on rock thermal conductivity were measured using divided-bar techniques. The introduced discontinuities lowered the thermal conductivity in all cases, and conductivity decreased systematically with increasing roughness of the discontinuity. Conductivity increased with increasing pressure on the discontinuity.

Jan 1, 1984

By J. J. Scott, L. Adler3

L. Adler (Assoc. Professor, Department of Mining Engineering, Virginia Polytechnic Institute, Blacks-burg, Va.) - Dr. Scott is to be commended for undertaking the arduous and specialized task of applying three-dimensional photoelastic techniques to a mining problem. However, 1 feel his analysis suffers seriously from a lack of clarification on one important matter, among several others; and that the paper as a whole lacks balance and thus tends to confuse the reader. 1) The major technical criticism refers to the fact that nowhere are the boundary conditions for his mod-

Jan 1, 1964

By B. Ramaswami, Y. Nakada, R. Schaefer

EARLY investigations1 of the tensile properties of fcc single crystals did not reveal the easy glide region of crystals with axial orientations inside the standard stereographic triangle. With the production of high-purity metal, a region of easy glide became known1 Consequently, modern work of fcc single crystals ordinarily uses high-purity metal. In order to determine whether further purification of aluminum beyond 99.992 pct purity would result in significant alteration of the tensile properties of single-crystal specimens, metal was zone-refined and crystals grown from the purified material were compared to crystals grown from the original material. Some similar studies were made of gold and silver crystals. Aluminum. The material to be zone-refined was cast into bars 1/4 by 1/2 by 8 in. A zone, approximately 1-1/2 in. in length, was passed over each bar eighteen times at a rate of 6 in. per hr. Melting and stirring were carried out by an induction heater under a vacuum of approximately 10"5 mm Hg, the metal being held in a graphite container. he last 3 in. of each processed bar were then cut off and discarded. No quantitative determination of purity was made, but the effectiveness of the zone refining was tested by a method first suggested by Walton, Tiller, Rutter, and winegard3 depending on the relation between cell structure and impurity content. Rutter and Chalmers4 have shown that a cellular substructure is associated with the presence of impurities during solidificatibn, and have shown how solute rejection at the freezing interface can lead to such an association. Thus the observation of cells gives evidence of impurities being present. To look for cells, the last quarter of a zone-refined bar was cut off, remelted, and grown rapidly into a single crystal. It was then heavily electropolished and thermally etched.~ Cells were revealed by the presence of many parallel rows of etch pits. The same process was carried out with material from the first half of the bar, but no cells were detected. These observations give evidence that a significant amount of impurity material was moved to the "dirty" end of the zone-refined bars. Further indication of purification was obtained from recrystallization experiments. It was found that, after cold rolling to a 97 pct reduction in thickness, the material from the pure end of the bar re-crystallized at room temperature, but the material from the "dirty" end did not. Other investigators6 have previously reported that zone-refined aluminum recrystallized at room temperature. The purified material was cast into 1/4 by 1/4 in. bars, and seeded crystals were grown in a (100) orientation and in a single slip orientation where the Schmid factor is m =2. The crystals were then cut to the desired length, annealed for 24 hr at 610°C, furnace-cooled, and etched in Tucker's etch. The crystals were tested in a floor-model Instron machine, using a gage length of 4 in. and a strain rate of 1/2 pct per min. The resulting curves are shown in Fig. 1. It is seen that the differences between the curves for zone-refined and original-purity materials are small. These differences are within the scatter observed for crystals of the original purity. In particular, the zone refining does not significantly affect the onset of the different "stages" of the curves.

Jan 1, 1964

By Letícia Gomes Mathias Netto Lima

Propriedades mecânicas podem ser melhoradas por meio de tratamentos térmicos, isso foi demonstrado por meio de estudos ao longo dos anos. O tratamento criogênico tem demonstrado que pode melhorar as propriedades dos aços temperados e revenidos, ao se reduzir a presença da austenita residual e ao promover a precipitação de microcarbonetos. Nesse contexto o presente trabalho, pretende realizar tratamentos de resfriamento e criogenia, buscando melhorias nas propriedades de aços temperados e posteriormente revenidos. Foram preparados corpos de prova em aços SAE 4140 submetidos a tratamento térmico de têmpera (a 850°C), e após foi realizado o tratamento criogênico (-196°C) ou resfriamento (-82°). E por fim, as amostras passaram pelo processo de revenimento. O tratamento criogênico ou de resfriamento são procedimentos que costumam ser utilizados após o tratamento térmico de têmpera, estes consistem em submeter os materiais a temperaturas muito baixas durante períodos prolongados de tempo. Foi realizado ensaio de tração nas amostras já preparadas, assim foi possível realizar um estudo comparativo sobre as mudanças estruturais, morfológicas e mecânicas de um aço SAE 4140. Para as análises estruturais, morfológicas e mecânicas foram utilizadas técnicas de caracterização como microscopia ótica, difração de raios-X e microdureza.

Aug 16, 2017

By T. Feroze, B. Genc

"The effect of some of the system variables in forcing and exhausting ducted fan systems on ventilation in an empty heading was investigated using computational fluid dynamics(CFD) and comparative analyses. The diameter of the duct, duct mouth to face distance, and the power of the fan (quantity delivered by the fan) were varied and their effect on ventilation determined through a comparative analysis of the flow rates calculated close to the face of the heading. Estimation models were developed, which can be used to calculate the flow rate close to the face of the empty heading for different settings of the system variables studied.The study showed that recirculation for a forcing ducted fan system can be reduced by increasing the duct diameter or increasing the duct mouth to face distance. For the exhausting ducted fan system, higher flow rates were achieved by reducing the duct mouth to face distance, andincreasing the fan design flow rate and duct diameter.The outcomes of this investigation will help ventilation engineers in deciding the optimum duct fan system required for sufficient ventilation.IntroductionThe ventilation of underground mines, irrespective of the type of mine and mining method, is divided into two broad branches, the primary ventilation and secondary or auxiliary ventilation. The primary ventilation is responsible for the total volumetric flow through the mine and the auxiliary ventilation is responsible for the ventilation of the development ends, production areas, and facilities disconnected from the main circuit with no through-ventilation connections. Auxiliary ventilation is the more difficult to achieve (Bise, 1996), and the disruption of this ventilation system is considered to be one of the primary factors contributing to methane and coal dust explosions (Creedy, 1996). A number of causalities have been recorded by many authors due to these explosions (Phillips and Brandt, 1995; Dubinski et al., 2011; Phillips, 2015). The ventilation of short headings, less than 10 m in depth, can be carried out without the use of any auxiliary equipment (Feroze and Phillips, 2015). However, for headings deeper than 10 m, auxiliary ventilation systems are required. These are generally classified into the three basic types, namely line brattice (LB) ventilation systems, ducted fan systems, and jet fans (Figures 1 through Figure 3 respectively)."

Jan 1, 2017

During the last decade mechanical rock excavation has become increasingly widespread in the mining industry and, more in general, in excavation engineering. This technology, especially the tools and their operating mode, has developed according to empirical procedures and for this reason their validity should be ascertained by systematically re-examining the rock breakage processes. This topic has been approached in the framework of a joint research project involving the Universities of Cagliari (Italy) and Wollongong (Australia). The investigation has been carried out experimentally as well as with the methods of numerical modelling which is based on fracture mechanics principles. The first results of this integrated research led to the proposal of an interpretation of rock breakage by means of drag tools and to the identification of a basic correlation between the rake angle of the tool and the grain size of the rock fragments produced and, therefore, the energy efficiency of the operation.

Jan 1, 1990

By M. E. Volin

To extend or delimit the known ore reserves of the Black Wonder manganese de-posit, the Bureau of Mines undertook an exploration project consisting of trenching, underground excavation, long-hole drilling, and sampling. The mineralization is spread over 6 square miles containing numerous small individual manganese deposits. There has been only small production from some of these deposits; however, simultaneous operations from many such small deposits could contribute considerably to the production from the district. A custom mill to treat oxide ore for battery use was built near Patterson in 1942 by the General Dry Batteries Co., Inc. It operated during World War II and was removed in 1944 when the manganese mines ceased operation. Except for some small experimental shipments, there has been no activity in the district since that time.

Jan 1, 1956

By Frank Tapia, Aldo Gutiérrez

El presente tiene el objetivo de mostrar las principales actividades que se realizan en la estabilización de taludes a doble banco en Sociedad Minera Cerro Verde SAA (Cerro Verde), con el fin de asegurar condiciones seguras y favorables en las operaciones mineras y trabajos en interacción con los taludes de mina.

Sep 30, 2022

By S. H. Ash

The Pennsylvania anthracite-mining region is the only one in the world of major magnitude. As the deposits of anthracite in the United States are limited virt113.lly to Pennsylvania, the difficulties of this industry have been commonly considered a State rather than a national problem. However, there is also national interest in the conservation and wise utilization of all fuel resources and in the control of interstate waterways. The anthracite industry is confronted with the very se:;-ious :problem of accumu.lation of water in many of the mines. This problem must be solved soon if progressively higr-er mi~ing costs are to be avoided. The water proble~ cannot be solved by the operating compa,nies without State or Federal aid, or both, owing to the magnitude of the work requir~d, diversity of interests of the coal ana surfa.ce ovmerships, hazard to the whole mining community, and interests affec~ed outside the mining region. The cost of abati~ the ever-increasing_surface seepage to mine workings and of handling this seepage once it }3s occurred is beyond the economic resources of most ope~ating ma.'18.gements. The data in this paper giving the high lights of the water problem and indicating what appears to be a step in the right direction are based upon observations made during the past year that the industry desires and believes it is to the npublic interesttr to keep mine workings free of flood end surface waters.

May 1, 1941

By M F. Gazley

The amphibolite-facies metabasaltic rocks of the Mine Mafic Package at Plutonic Gold Mine, Marymia Inlier, Western Australia, contain an estimated total endowment of 12.2 Moz of Au, which includes 4.71 Moz of past production and 2.77 Moz of reserves and resources; the remainder comprises lower-grade inventory. Over 65?000 multi-element analyses of whole-rock core and face channel samples from the underground workings of the deposit have been collected by portable X-ray fluorescence (pXRF) using a handheld Innov-X Omega pXRF unit. The analyses were performed on pulverised samples through paper bags, and were corrected using a pulverised, matrix-matched, reference standard. This method of data correction compares favourably with conventional XRF analyses performed on the same samples.A preliminary study based on pXRF analyses from a small number of drill holes found that a geochemical stratigraphy was evident in the pXRF data, and that this stratigraphy strongly controlled the location of Au mineralisation. The present study incorporates a much larger pXRF data set that samples a greater volume of diamond drill core and face channel samples and presents the data in a three-dimensional (3D) framework.This data set allows an investigation of the mineralogy of Au mineralisation with varying geochemical associations across the deposit. Historically, there has been a strong relationship identified between As and Au, which has caused issues with metallurgical performance, rendering some areas of the deposit only marginally economic. Utilising seamless data integration of the pXRF data set allows for recognition of the different styles of Au mineralisation using elemental concentrations and ratios from the multi-element analyses (Au:As, Au:As:Cu, As:Cu vs. K:V), and to visualise the distribution of these different mineralogical associations in 3D. The results of the 3D modelling and geochemical characterisation of the different styles of Au mineralisation are currently the focus of an extensive metallurgical testing program, the preliminary results of which are presented here.

Aug 22, 2011

By Xiaochao Shu, Kun Wang, Fanwei Meng, Rui Tao

Rapidly searching for carbonatite-related rare earth element (REE) mineralized systems is of paramount importance to explorers, because these systems provide the world’s most significant supply of REE. Biotite and barite are suitable indicator minerals that can offer reliable elemental geochemical information used for REE exploration. In this study, we provided an elemental geochemical dataset of biotite and barite from Cenozoic REE deposits in the eastern Tibetan Plateau, and compared the obtained data to those of biotite and barite forming in other geological settings. The F (i.e., fluorine) contents in carbonatite-hosted biotites are highly variable, with biotites from mineralized carbonatite complexes having much higher values (1.05–2.37 apfu, where apfu = atoms per formula unit) than their counterparts from barren carbonatite complexes (≤ 1 apfu). It is therefore believed that the presence of high-F biotites can be regarded as a sign for predicting REE reservoirs. Barites in REE mineralized systems contain much higher (even one or to orders of magnitude) total REE contents (ΣREE >100 μg/g) relative to those species forming in carbonate-hosted fluorite-barite deposits and open marine environments. This means that the high ΣREE concentration of barite can serve as an effective index for REE exploration. The above information is integrated into a REE exploration program in which the areas with strong local tectonism along cratonic edges are priority exploration targets, and high-F biotites and REE-rich barites can serve as direct indices for rapidly identifying carbonatiterelated REE mineralized systems at a strategic distance from other geological settings.

Jun 9, 2023

By B. W. Gandrud, G. D. Coe

"INTRODUCTION The Bureau of Mines, United States Department of the Interior, with the cooperation of the University of Alabama and coal producers of Alabama, is making a series of washability studies to obtain technically and commercially important data from the productive coal beds of the State. Based on the system followed in these studies, this report consists of screen-sizing and sink-and-float data on the America and Pratt beds at Gorgas, Ala.SAMPLING AT THE MINESAlthough operations were discontinued in 1929, the accessible openings of the old Gorgas mines of the Southeastern Fuel Co. made possible the taking of samples from the America bed at three openings and from the Pratt bed at two openings. A sample was taken from the America bed at the Klondyke opening; a second was taken about 1 rile south of the Klondyke at the Musgrove America opening, and a third sample was taken about 1-1/2 miles south of the Musgrove-America at the Cricket Lodge opening. A sample was taken from the Pratt bed at Musgrove-Pratt No. 1, which is about 3/4 mile east of Musgrove-America, and a second sample was taken at Musgrove-Pratt No. 2, which is about 3/4 mile west of Musgrove-America. The samples ranged in weight from 1/2 ton to 1 ton and were equivalent to approximately a 2-ton sample from each bed. Figure 1 shows sections of the beds at the places sampled.In addition to the samples for washability study, a seam sample for analysis was taken at each of the places sampled. So as to give a representative seam sample for each of the two beds, these samples were combined in the laboratory in proportion to the thickness of the bed at the places sampled."

Jul 1, 1939

By Richard S. Olsen

Prior work by the Bureau of Mines demonstrated a feed preparation method that eliminates the formation of slime during leaching of calcined kaolinitic clay and makes leached residues fast settling and easy to filter. Nitric acid leaching rates determined for calcined kaolinitic clay prepared by this method were found to correspond to a zero-order reaction model for both batch and continuous, stirred-tank leach-ing. A rate constant of 0.136 min-1 was determined. Separation of solid residues from the reacted slurry was examined, and filtration rates were determined. Permeabilities of the flocculated, leached residues were around 51 darcys, or 5.0 x 10-7 cm2 for laminar flow through 4-ft-deep beds.

Jan 1, 1983

By Pengfu Tan

A thermo-chemical model of the copper P-S converter and a viscosity model for the converter slag have been developed to predict the behavior of magnetite in the converter slag, amounts of slag and matte, compositions of slag and matte, volume of the bath, bath temperature, slag blow endpoint determination, SEMTECH OPC signals, and the viscosity of converter slags. The predictions of bath temperature, slag and matte compositions, and magnetite content in the slag have been validated by the industrial data. The effects of fluxing strategy, returns and skim charges, oxygen enrichment, and temperature on the magnetite formation in the slag have been predicted and discussed. The effect of oxygen potential, SiO2/Fe in slag, detection of slag blow endpoint, and temperature on Fe3O4 content in converter slag, slag viscosity, liquidus temperature of converter slag and skimming operation has been modeled and discussed as well. Some applications of the industrial operations have been presented.

Jan 1, 2009

By Romeo Calderón

El presente trabajo describe los trabajados realizados en la Compañía minera Huarón con el objetivo de realizar la explotación de vetas muy angostas y sinuosas de potencias inferiores a 1.20 m. de un modo seguro, eficiente y económico, donde fue necesario resolver el problema de carguío y acarreo en tajeos inferiores a 1.20 m. empleando equipo LHD de 0.80 m. de ancho, fabricado especialmente para este fin.

Nov 1, 1982

By Carina Ulsen

The existing construction and demolition (C and D) waste recycling technologies and standards have been essentially focused on the production and use of coarse recycled aggregates. Very few papers focus on the production of recycled sand, although some previous results show that fine aggregates fraction represents around 40 to 60% (in mass) of the Brazilian waste and it is usually used as road sub-base or disposed in landfills. The quality of the recycled aggregate is strictly related to the content of porous and low strength phases, mainly the patches of cement remaining on recycled aggregate surface. Some technologies have already been described in the literature, even though, to the moment none of these technologies has clearly succeeded in reaching the large market available. This paper presents a summary of the main properties of the sand produced from C and D waste by tertiary crushing at vertical shaft impact crusher (VSI). Additionally mineral processing technologies were applied on the attained product, such as gravity concentration by shaking table and spirals and removal of cement paste by attrition. The main properties of recycled sand are discussed and compared to the previous C and D waste, respectively: particle size distribution, particle shape, chemical composition, cement paste content and porosity. The results demonstrates that the crushing allowed producing a VSI-sand with low porosity and water absorption due to the increasing on the content of silicates from natural rock phases and increasing liberation between these phases and porous cement paste; the particles from the attained product presented also a better shape (sphericity and aspect ratio). The attrition tests assayed on VSI recycled fine aggregates accomplished a further selective disaggregation of cement paste and other porous materials - the porosity was reduced from 10% to 7%. The concentration by shaking table at narrow sieve fractions led to a product with low porosity and reduced content of cement paste, however, concentration on spirals did not succeed since separation was performed essentially by the size of the particles. The heavy product from shaking table represented almost 75% in weight and has less than 60% recovery of CaO+LOI, and expressive reduction on porosity. The aim of producing sand from construction and demolition waste through mineral processing unit operations changes the recycling approach and contributes for up cycling the recycled sand. The exhaustion of sand deposits on Brazilian large centers, the increasing price and the construction boom encourages the development of alternative materials as construction raw material. Keywords: recycled sand, construction and demolition waste, technological characterization

Sep 1, 2012

By Michael Moats, Weston Hartzell

The stable domestic supply of gallium, indium, and germanium has been identified as a critical need for the USA. Electric arc furnace dusts processed to recover zinc produce a process residue that could be a potential source of these critical materials. An industrial zinc leach residue was characterized to determine the predominant mineral phases and leached with common mineral acids. Atmospheric agitated leaching using sulfuric acid and hydrochloric acid were examined to determine the extractions of gallium, indium, and germanium as a function of concentration, temperature, and time. Extractions of gallium were found to be similar to iron in all experiments. The maximum percentage of Ga, Ge, and In leached into solution were 82%, ~100%, and 89%, respectively.

Aug 8, 2023

By V. V. Ramarao

Grinding and flotation operations deliver better-optimized performance when they are monitored and controlled in terms of the minerals they process rather than as elemental assays that we usually refer to. Mesh of grind (MoG), liberation, floatability, grade and recovery etc. are more directly related with the minerals and their characteristics rather than the elemental assays. Hence, online analyzers only provide the status for the grade and recovery of metals and not the direction for the enhanced performance. Central Research and Development Laboratory (CRDL) and Rampura Agucha Mine (RAM) mill section of Hindustan Zinc Limited (HZL) jointly undertook various survey campaigns in the grinding and flotation process streams. Grinding circuit surveys involved systematic collection of representative samples from different grinding circuit streams under stabilized conditions for monitoring particle size and process mineralogy details across individual grinding circuit. Flotation survey campaigns included study of fort-nightly / monthly composites of un-ground flotation feed, lead concentrate, lead tailing, zinc concentrate and final tailing samples for size distribution details in the 150 ? 38 micron range, chemical analysis and mineral characterization through optical microscope. This work details the investigations results and their implications on beneficiation performance. Grinding circuit survey campaigns supported the task for modifying the originally installed configuration of hydrocyclones, to limit recovery losses due to excess grinding of soft galena and related silver minerals. Flotation plant surveys helped in adjusting flotation circuit process parameters to reduce loss of liberated and floatable galena and sphalerite grains into their respective tailing streams. Keywords: grinding circuits, survey campaign, hydrocyclones, mineral liberation and locking, lead-zinc ore beneficiation operation

Sep 1, 2012

By S. W. Parr, T. E. Layng

There is presented below the results of experiments made on six samples of Utah coals furnished through the U. S. Bureau of Mines , under an agreement dated June 16th , 1920. The details of all values for all runs are tabulated and presented herewith . Clear The samples, consisting of approximately 150 pounds each, were received at the University of Illinois , on June 15 , 1920 , and are listed as follows : Creek , Wattis , Castle Gate , King , Standard , and Aberdeen . The proximate and ultimate, analyses of the various ccals from that region , representing all the types included in these samples , have already been made by the Bureau of Mines , and are available . * Similar determinations were also made on the particular samples forwarded for purposes of these experiments . The results obtained on the coal as received did . not very in any material feature from the values reported by the Bureau, they are shown in Table 1. It is of importance to note only that the oxygen content is uniformly high , namely approximately 9.5 to 11.5 per cent of the as- received coal , while the oxygen - hydrogen ratio is also high, being on the average approximately 2 ( oxygen) to 1 ( hydrogen) .

Sep 1, 1921

By De-qing Zhu, Feng Zhang, Jian Pan

Sintering performance of a series of sinter blends with high ratio of limonite was investigated. The metallurgical performance and mineralogy of product sinter were also examined. The results show that good sintering performance could be obtained when the ratio of limonite was below 43% in the blends of iron ore fines, while good microstructure and metallurgical properties were achieved under optimum sintering conditions. In contrast, sintering performance will rapidly deteriorate when the ratio of limonite is elevated up to 63% in the blends.

Mar 1, 2017