Search

This paper employs the method for evaluating abrasion proposed by Golovanevskiy e Bearman (2008). This method, Gouging Abrasion Test, employs high-stress load gouging/sliding impact wear. The method consists of a steel wear tool with a 90" sharp conical tip. This tip attacks a rock sample in a swinging trajectory with an impact energy of 300 J and a speed of around 5.2 m/s. The Gouging Abrasion Index (Gi) is determined as 10 times the average diameter in millimeters of the conical tip (now flat) after one event of wear. This paper evaluates the Gouging Abrasion Test suitability in a small group of rocks that represents some of the main types to be found in Brazil's rock cutting, drilling and crushing works. Its relationship to other usual tests like uniaxial compressive strength, Amsler abrasive wear and Knoop hardness were also verified. The results show high correlation between Gi and Knoop hardness (R² = 0,94), low correlation with Amlser wear (R² = 0,41) and no relation to uniaxial compressive strength. [ABSTRACT FROM AUTHOR]

This paper discusses the results of a mixed grinding simulator application based on an artificial neural network (multiple-layer perceptron using a back-propagation-like algorithm with moment). The data used came from a previous paper entitled "Selective grinding of dolomite and quartz mixes". The Shewhart control chart for individual values was used in order to verify the statistical stability of the simulation process results, which was useful for testing acceptance. The results have displayed good performance of this tool related to mix grinding simulation, a common issue in the mining and metallurgical sectors. [ABSTRACT FROM AUTHOR]

This paper presents the shell finite elements of the computer system INSANE (INteractive Structural ANalysis Environment): four-node rectangular and three-node triangular, obtained by combining membrane and bending efforts, based on the Theory of Kirchhoff; a quadrilateral of four, eight and nine nodes that combines membrane, bending and shear efforts, according to the Reissner-Mindlin Theory. After summarizing the characteristics of the elements, the paper presents results of three convergence studies and two practical applications: an arch dam and a conical-cylindrical reservoir. The results are compared with analytical solutions and those obtained with the shell finite element of SAP2000. [ABSTRACT FROM AUTHOR]

This paper compares the performance associated with both direct and reverse ball mill closed circuit configurations. Survey campaigns were carried out in both Samarco Mineração industrial plants, i.e., Concentrator I and Concentrator II. The former is equipped with a reverse-configured ball mill closed grinding circuit, while the latter is equipped with ball mills under a direct closed circuit. The study consisted of laboratory jar tests, as well as comparisons between historical data obtained for both industrial plants. Comparisons based on historical data indicated that Concentrator II, configured in a direct mode, exhibited a better performance than that of Concentrator I. Such a conclusion is in contrast with the results obtained from survey campaigns, which indicated a better performance for the reverse configuration. Such a difference was determined by the performance of the classification stage, carried out in cyclones, as demonstrated by simulations conducted on the basis of previously calibrated models. [ABSTRACT FROM AUTHOR]

This paper presents a study on the stability and nonlinear vibration analysis of planar pitched-roof frames. Special attention is dedicated to the influence of static preloading in natural frequencies and vibration modes of these structures. For this, used was a nonlinear beam-column element formulation that considers connection flexibility between the structural members. The global nonlinear static equilibrium problem is solved using an incremental-iterative procedure, where in each load increment, the Newton-type iteration scheme is coupled to an arc-length strategy. At convergence in each load step, the Jacobi method determines the natural frequencies and vibration modes of the preloaded structure. The complete nonlinear solution strategy adopted is detailed in an algorithm. The influence of a geometric parameter (scissors' height) and other physical (support's stiffness) in the pitched-roof frame behavior is highlighted in the analysis. The goal is thus to have a better understanding of some instability phenomena and structural sensitivity, and to show the importance of these parameters and static preloading on the buckling and vibration of these frames, which have great practical application. [ABSTRACT FROM AUTHOR]

This paper presents the parameters that guide the design of laboratory equipment to evaluate slabs and beams, in full-scale load, and in fire. Parameters of interest such as the internal dimensions, rate of temperature rise according to the time, infrastructure for installation of equipment, among others, are evaluated based on national and international standards. In the end, it is hoped that this report about the exercise of design and construction of the first horizontal Brazilian furnace encourage the future construction of this kind of equipment, helping national and international researchers in the area to start a similar, and arduous, task. [ABSTRACT FROM AUTHOR]

This paper presents a formulation for distortional buckling stress (σdist) in cold-formed steel lipped U section columns, with simply supported end conditions and free warping. This formulation is based on an adjusted model from an artificial neural network (ANN), whose data was provided by a program based on the Finite Strip Method (FSM). The results show the viability of the obtained equation for determining σdist on a columns made with the analyzed sections. [ABSTRACT FROM AUTHOR]

This paper presents the classification of 110 copper ore samples from Sossego Mine, based on X-ray diffraction and cluster analysis. The comparison based on the position and the intensity of the diffracted peaks allowed the distinction of seven ore types, whose differences refer to the proportion of major minerals: quartz, feldspar, actinolite, iron oxides, mica and chlorite. There was a strong correlation between the grouping and the location of the samples in Sequeirinho and Sossego orebodies. This relationship is due to different types and intensities of hydrothermal alteration prevailing in each body, which reflect the mineralogical composition and thus the X-ray diffractograms of samples. [ABSTRACT FROM AUTHOR]

This paper presents the results of geologic and gravimetric surveys carried out in the area of the Mendanha Alkaline Complex. The applied techniques were: geological mapping and terrestrial gravimetric survey with LaCoste & Romberg equipment and Differential GPS position control. The integrated analysis allowed for the building of 2.5D models and cross-sections, to estimate the geometry of the alkaline suite. The Mendanha Alkaline Complex is composed of siennite rocks with variable grain-size, with predominance of alkali-siennites, siennite and pyroclastic rocks in the region of the "Nova Iguacu Volcano" and nepheline-bearing siennites in the region of Morro do Marapicu. Siennitis rocks have an average bulk density of 2.54g/cm3 and the pyroclastic rocks about 2.46g/cm3, measured in the laboratory. In comparison with the host gneiss, with a bulk density of about 2.68g/cm3, these alkaline rocks have a negative gravimetric anomaly. The "Nova Iguacu Volcano" gravimetric model shows a funnel-like geometry of siennitic rocks with a columnar structure (conduct) of pyroclastic rocks. The Morro do Marapicu model shows a shallow convex structure and was interpreted as the continuation of Mendanha. Thereby, the current denudation stage is characterized by an eroded basal section of a magma chamber, with exposure of pyroclastic conduit and feeder dikes. [ABSTRACT FROM AUTHOR]

The use of scrap tires in civil engineering involves creative solutions and diversified applications. The present paper presents parametric analyses based on laboratory data with different tires, wall heights, filling materials, water levels and soil friction angles. A design draft for 376 different earth retaining structures (combining all variables) was made and a statistical analysis performed to study the effect that each variable had on the base value. Finally, a case study is presented of a tire wall construction near Ijuí City - RS. The cost of this solution is given in comparison with the traditional concrete ones. [ABSTRACT FROM AUTHOR]

This paper discusses the durability's influence on the geotechnical behavior of the West Slope's rocks of Pau Branco Mine, this being the mining site on Vallourec & Mannesman (V&M) property, located at Serra da Moeda, Brumadinho, Minas Gerais. At the site, the occurrence of acute fracturing and folding of the rocks, plus the effects of the local weather conditions, were responsible for forming low mechanical strength and high alteration grade rocks, favoring destabilization mechanisms. The influence that durability has on the phyllite's physical properties was evaluated through slake durability tests with different alteration grade and strength phyllites. Through the same tests, an attempt was made to identify the existence of an association between the durability and the failure mode in phyllite's slopes. This correlation was important to be found because it could be used as an expeditious indicative of the failure mechanism and the strength of the lithologies that exist in the slope studied. Furthermore, these studies included kinematic analysis to identify conditions for the occurrence of failures caused by discontinuities and to compare these failures to the ones observed at the mining site. For this purpose, Rocsciense's software Dips 5.0 was used. [ABSTRACT FROM AUTHOR]

Iron ore products are defined by their iron and contaminant grades and also by the granulometric partitions. Data from iron ore deposits constitute compositional data, involving a vector of variables adding up to a constant sum given by the mass balance among granulometric partitions or among chemical species in each granulometric fraction. The closed sums lead to spurious correlations and to a negative bias condition. This condition leads to estimates that do not satisfy the balances and estimates that take negative values or do not belong to the interval of values of the original data. Classic geostatistical methodologies do not take these facts into account and the common practices force the sum through determining one variable by difference, distributing the sum error or using an intrinsic corregionalization model and substituting of the negative values by valid ones. In this paper, cokriging of additive log-ratios (air), a transformation developed for compositional data, is presented as an alternative methodology to estimate grades in iron ores, in presence of multiple correlated variables with a closed sum. Results obtained through this methodology are better than the ones obtained by direct cokriging of the original data, leading to positive estimates, all in the original data interval and satisfying the considered constant sums, without post-processing. [ABSTRACT FROM AUTHOR]

The article offers information on the editorial policies, submission of research papers and subscriptions to serial publications of the journal.

This paper involves the characterization of marble waste, steelmaking fine sludge and aluminum dross, to ascertain the technical feasibility of using these in the desulfurization and dephosphorization of hot metal. The characterization of these residues was done taking into consideration: chemical analysis, particle size, X-ray diffraction results and scanning electron microscopy (SEM) with Energy Dispersive Spectrometry (EDS) data analyses. The steelmaking fine sludge has a EeO content of 84.90%, the marble waste lodged content of 61.5% CaO and 33.9% MgO, and alu-minum dross 36.5% ofAl metal and 62% of A I,(),. The particle size of marble waste had of the average grain size equal to 42.8 pm, in aluminum dross the average size was 101.8 pm and steelmaking fine sludge showed around 54.7% of its grain size between 0.15 and 0.075 mm. These results indicate the feasibility of using these materials in the desulfurization and dephosphorization of hot metal. [ABSTRACT FROM AUTHOR]

The aim of this paper is to present and discuss the air dispersion parameters determined for industrial Brazilian flotation circuits. The rougher and scavenger circuits of RPM, Taquari-Vassouras, Copebras and Fosfertil-Catalão (today Vale Fertilizantes) were investigated. For RPM and Taquari-Vassouras, the superficial gas velocity (Jg), gas hold-up (&egr;g), bubble size diameter (d32) and superficial area bubble flux (Sb were measured, whereas only the Jg and &egr;g were measured in the other circuits. The results pointed out that, except for RPM, all the circuits presented very low values for the air dispersion parameters. Taquari-Vassouras presented the lowest values for average Jg and gas hold-up: 0.05 cm/s and 5%, respectively. The highest value was presented for the rougher circuit of Cope-bras, 1.17cm/s, while RPM presented the highest values for &egr;g and bubble size, respectively 31% and 2.61mm. In the circuits where the calculation of the Sb parameter was possible, the results obtained lay in a range lower than those re-ported in literature. [ABSTRACT FROM AUTHOR]

Ophiolites are fragments of the ancient oceanic lithosphere formed at constructive plate margins or transforming divergent plates. Through extensive thrust faults, these bodies or part of them are emplaced into the continental crust, inside rock piles of orogenic belts, in solid state, but these bodies can be relatively warm. The possible environments which produce oceanic lithosphere include meso-oceanic ranges, basins related to juvenile island arcs and retro-arc basins. Ophiolites of the Phanerozoic age are abundant in orogenic belts around the world whilst Precambrian oceanic remnants are less common and are distributed mainly in Finland, Canada, Morocco, Saudi Arabia, Egypt, Russia, Brazil and China. Several registers of Precambrian oceanic remnants of different ages were recognized in Brazil. Most of these bodies are situated in Brazilian orogenic belts and they register the consumption of the Neoproterozoic oceans. This paper aims to synthetize the main information about ophiolitic sequences, bringing a brief review of concepts and classifications along the 200-year use of this term. [ABSTRACT FROM AUTHOR]

In this paper the technique of strengthening reinforced concrete beams to prevent the bending phenomenon by increasing the thickness in the compressed chord region is evaluated. Two reinforced concrete beams with identical longitudinal and transversal dimensions and fixings, were molded. After twenty-eight days, one of these beams was reinforced with a layer of high-resistant concrete in the compressed region. A third beam was single-stage molded using both types of concrete and had the final characteristics of the previously reinforced beam. Finally, the rupture behavior of the three beams was analyzed, proving the efficiency of the reinforcement technique proposal. [ABSTRACT FROM AUTHOR]

Underground mine planning is an important element for achieving project re-alization in the current highly competitive scenario. This is due to the peculiarities of the underground mines, where it is difficult to obtain profound knowledge about the body and location of the underground excavations. Computer applicationsspatially visualize the ore body with its geological sec-tions and mineral formation contours. This visual is in 3D that facilitates the alloca-tion of major mine development services. Although such resources are available, their mining applications are generally developed for open pit mining methods, and is still incipient for underground mine-development methodologies. With the use of applications for mine development and planning, and the simi-larity of existing mines, it was possible to prepare the infrastructure project for a specific underground mine, and a 3D view of its underground openings. It was also possible to develop a methodology for drawing the galleries described. This paper deals with the selection of mining methods for a major simulated mineral deposit and describes breakthroughs of underground mine development de-sign using a commercial mining application. [ABSTRACT FROM AUTHOR]

The paper describes the research carried out in the application of complexity analysis in order to evaluate the performance of the rock blasting process in mining. The main objective of the research is the development of a new method to allow the identification of a robust solution for managing rock fragmentation and to plan the process so that productivity targets can be achieved. The research uses complexity analysis tools introducing a particular approach for complex system analysis in min-ing and in rock blasting. The results indicate that the proper understanding of the correlations between the key-variables in blasting provides important benefits in the decision making process in the highly uncertain environment of rock blasting. The search for a robust system has proven to be more relevant than the search for a theo-retically optimum solution, as the levels of robustness and complexity can be used to compare different models and to measure the adherence of such models to the actual field data. [ABSTRACT FROM AUTHOR]

The Amazon Fan, located in the deep-sea Foz do Amazonas Basin on the Brazilian Equatorial Margin, is one of the largest submarine fan systems in the world. It 's most important features are shale diapirism and a linked extensional-compressional system on a basal detachment. In this paper, we re-interpreted six seismic reflection lines to provide new insights into the gravity tectonics of controversial age. On seismostratigraphic data, we recognized the acoustic basement and six sedimentary units. Extensional faults rooting into a detachment revealed seaward decreasing age, pre- to syn-tectonic with respect to the gravity sliding, and rare activity in the faults at present. For basal detachment became active during Mioceno Superior. Suggested is the basal portion of the paleocenic Travosas Formation that in consequence of an overload caused by the deposition of the Pará Group. [ABSTRACT FROM AUTHOR]

In underground mining, daily a fleet of LHDs must be allocated to a haulage network of drifts for extracting ore according to a plan-driven strategy. This plan is hierarchically decided by a higher management level and it contains the number of ore bucketfuls to be extracted from each drawpoint within a drift for each working shift. In this paper, an integer programming (IP) model for minimizing the makespan of drift workload is formulated and a polynomial time optimal algorithm for its resolution is proposed. Next, a set of decision rules obtained from the algorithm above is integrated into the decision-making process (DMP). This DMP is simple to execute for LHD operators, determines the optimal makespan, and whether or not it can be carried out in the working shift. Finally, a comparative analysis between the DMP proposed and the DMP used in El Teniente copper underground Chilean mine is studied. The results show that the cumulative operators experience has converged to solutions near to optimal makespan. [ABSTRACT FROM AUTHOR]

In the Ouro Preto - MG region, there are several soap stone workshops where artesans create souvenirs and pans. This activity produces a large amount of residues which are discarded without any control. The objective of this work was to recover the talc mineral present in the size fraction below 74µm of these residues by froth flotation and chemical leaching with HCl. Among the flotation variables studied, only the percentage of solids and frother dosage proved to be significant for mass recovery and whiteness. This process produced a concentrate whose whiteness (ISO) was 68.56% and whose chemical composition meets paint and paper standards. After chemical leaching of the flotation concentrate, a whiteness of 84% was obtained and its chemical composition met the specifications of the plastic and anti-adherant plastic industries. [ABSTRACT FROM AUTHOR]

Mineral research studies are fundamental for the recognition and incorporation of new reserves. This paper presents the results of an application of the Electrical Resistivity geophysical method to a mineral occurrence of copper carbonates, by an electrical profiling technique in an azimutal array. The parameter of physical electric resistivity was measured, using the Electrical Resistivity method and the technique of electrical profiling. This study area is inserted in the Camaquã sedimentary basin, formed by sedimentary and volcanogenic stratigraphy units, where several copper occurrences are encountered. The presence of azurite and malachite in the fractures and high porosity zones in arenitic hosts define the local geology. The inversion models reveal circular anomalies of moderate resistivity up to 25m below the outcropping surface, and anomalies of low resistivity for depths below 25m, besides adjacent areas with high resistivity. Mineralization indicators described for the copper occurence in the Camaquã sedimentary basin are encountered in previous studies as well as the area now studied and allow for characterization in terms of electrical resistivivity. Silicified areas present high resistivity, while intermediary values are attributed to carbonated zones, and finally, low resistivity areas probably indicate concentrations of disseminated sulfites. [ABSTRACT FROM AUTHOR]

Reconciliation can be divided into stages, each stage representing the performance of a mining operation, such as: long-term estimation, short-term estimation, planning, mining and mineral processing. The gold industry includes another stage which is the budget, when the company informs the financial market of its annual production forecast. The division of reconciliation into stages increases the reliability of the annual budget informed by the mining companies, while also detecting and correcting the critical steps responsible for the overall estimation error by the optimization of sampling protocols and equipment. This paper develops and validates a new reconciliation model for the gold industry, which is based on correct sampling practices and the subdivision of reconciliation into stages, aiming for better grade estimates and more efficient control of the mining industry's processes, from resource estimation to final production. [ABSTRACT FROM AUTHOR]

This paper addresses the characterization of fines stocked in a pond as tailings from an iron ore concentrator. The characterization consisted of size analyses by wet screening, chemical analyses by ICP, and mineralogical analyses by X-ray diffraction. The next stage consisted of technological tests. Two concentration routes were evaluated at bench scale: the first (route I) consisting of classification (0.15mm), magnetic separation (-1.0+0.15mm), desliming and flotation (-0.15mm); and the second (route II) consisting of magnetic separation (-1.0mm global), aiming at achieving a concentrate adequate for use in the metallurgical industry. The size distribution of the iron ore fines indicated 8.21% above 0.150mm and 58.81% passing 0.045mm. The calculated average chemical composition of the sample is 48.08% Fe, 20.58% SiO2, and 3.16% Al2O3. The iron minerals identified by X-ray diffraction were: hematite, martite, magnetite, and goethite; and the detected gangue minerals were: quartz, gibbsite, and kaolinite. The best performance came from route II, magnetic separation only: weight recovery 68.00%, metallurgical recovery 90.81%, 67.54% Fe, 1.50% SiO2, 0.49% Al2O3. [ABSTRACT FROM AUTHOR]

In Ouro Preto/MG, pyrite was exploited at an old mine from 1930 through 1967. Considered as one of the best resources of pyrite in Brazil, this mine was exploited in order to supply sulfuric acid for explosives manufacturing, at the President Vargas Plant in Piquete/SP. The mine site is abandoned and has slope instability and acid leakage generation as the main environmental liabilities. Lately, the site has been used for illegal deposition of all sorts of urban waste. The Ouro Preto Administration, on its turn, has the intention of using part of the mine site for the disposal of solid residues of civil construction. This paper presents the results of kinetic tests carried out, in leaching columns, to assess the acid mine drainage potential in samples collected from the mine site and to evaluate the possibility of controlling and minimizing acid generation by using solid residues as a covering system. Laboratory results show that cover with solid residues of civil construction was effective in the reducing the acidity, concentration of metals and sulfate. [ABSTRACT FROM AUTHOR]

This paper describes the application of diffuse reflectance spectroscopy in the development of a methodology for the identification and quantification of minerals in bauxite and iron ores. Selected samples containing a mineral variability were collected from the Iron Quadrangle (Minas Gerais) mines and from the region of Carajás (Pará). The different mineral concentrations were estimated from a combination of conventional methods such as chemical analysis, Mössbauer spectroscopy, Xray diffractions, magnetic susceptibility and optical microscopy. Diffuse reflectance spectra in the visible, near infrared and mid infrared regions were correlated to the mineralogical composition by chemometric algorithms. The mineralogical analysis showed satisfactory correlations, and on the average the statistical parameters were found to be close to R2 = 0.93 for bauxite and R2 = 0.87 for iron ores. Goethite [R2 = 0.96, average standard error of validation (RMSEC) = 3.6%] and hematite (R2 = 0.90, RMSEC = 7.3%) for iron ore. These results suggest that the diffuse reflectance spectroscopy is a fast and easy method for the simultaneous determination of various minerals present in bauxite and iron ores. [ABSTRACT FROM AUTHOR]

In this paper a Canadian proposal for waste dumps classification according to their physical stability is presented. The method is based on a semi-quantitative evaluation of key factors affecting the stability of a waste dump, and the result allows assigning a certain class of dump according to their instability potential. These classes define a recommended level of effort for investigation, design, construction and monitoring of the dumps. To check the effectiveness of the classification a case study was carried out in face of the iron ore mining reality, in Nova Lima City, Minas Gerais State. The implementation of this work involved a documentation search followed by field work and analyses in order to apply the collected information about the dumps in the classification. The work also shows innovations introduced by the Authors about the use of the classification system as a means of assessing the quality of the dumps management and also makes it possible to identify main aspects of a project. The proposed classification system showed that it is a very useful tool for both planning and evaluation of all stages of a waste dump life. [ABSTRACT FROM AUTHOR]

This paper presents the results obtained with the production of briquettes from the steel grit found in the residue of ornamental rocks. The grit recovered by magnetic separation was characterized by titrimetric analysis, EDS (Electron Dispersive Spectroscopy) and X-ray diffraction for the analysis of iron concentration in the residue. The size and distribution of particles were obtained by the granulometric analysis method and scanning electron microscopy (SEM). The process resulted in a concentrate containing 93% metallic iron. The maximum load before fracture of the green briquettes was 1.02kN and of the dry briquettes was 3.59kN. [ABSTRACT FROM AUTHOR]

Several mining companies operating in Brazil have been preparing mine closure plans describing end of life actions to ensure long term physical stability, land rehabilitation and, to a certain extent, socioeconomic measures. Most Brazilian and international guidelines, however, skip early closure and only feature guidance to closure planning after reserve depletion. In this paper, two cases of early closure in Australia are reviewed, causes for early closure are explored, criteria to evaluate preparedness to early mine closure are proposed and tested in two mines. It concludes that, despite recent advances, planning for mine closure seldom take account of early closure risks. [ABSTRACT FROM AUTHOR]

The water absorption of ceramic tiles is a basic parameter for its classification. In this paper the water absorption was studied in red clays of the Corumbataí Formation to verify the influence of the particle size distribution and mineralogical composition in four different samples of clays through the evolution of the sintering with the increase of the temperature. Mixtures of raw materials were prepared by the contribution of each one. It was based on the individual absorption of water to get prefixed water absorption for the mixture. The causes of the experimental variations were analyzed in relation to the expected value, to make corrections in the composition or temperature, allowing larger control on the products. The acquired packing for a constant compaction density of the test specimens and the mineralogical composition, responsible for the content of fluxing compounds, were effective to justify the observed ceramic behavior. [ABSTRACT FROM AUTHOR]

The Quadrilátero Ferrífero region, in the State of Minas Gerais, became internationally known due to the exploitation of gold in the eighteenth century. In this paper, we will present background values for arsenic in alluvial sediments from areas that were heavily affected by the exploitation of gold in the past, in the Carmo River Basin. The analyses of the facies succession of the alluvial profiles were carried out in the sedimentary deposits of flood plains, cutbank and alluvial terraces; this being the foundation for obtaining the arsenic background in the facies of the channel and flood plains. From the knowledge of the background obtained by the statistical method, and based on the construction of cumulative frequency curves on a linear scale, geochemical maps were generated in the SIG system. The acquisition of the background values and the geochemical map for arsenic in the Carmo River Basin, representing areas with anomalous concentrations of this element, are essential for the diagnosis and environmental planning of a mining district potentially contaminated by arsenic. [ABSTRACT FROM AUTHOR]

The main objective of this paper is to analyze the behavior of bulk material flow in rough-surface ore passes. A physical model of an ore pass in reduced scale has been used to observe the effect of the roughness on the flow. The insertion of wooden plates on the internal walls of the model was carried out in order to simulate the slickensided stepped roughness. This model of roughness has been selected from the standards adopted internationally by the ISRM due to its similarity with the actual roughness found in ore passes built using explosives. The tests showed that the slickensided stepped roughness causes a significant decrease of the flow rate when compared to the tests carried out with smooth walls. The tests' results also indicated the occurrence of mechanical arches, funnel flow and turbulent flow. [ABSTRACT FROM AUTHOR]

In the room-and-pillar mining method, conventional mining system had its peak along the 1950's and 1960's in the United States, giving place to the continuous mining system. In Brazil, these systems are still in use in some underground coal mines. This paper presents a production simulator developed to emulate the mining cycle at Carbonífera Metropolitana S.A., where all the unit operations in coal mining were included. A model was proposed for the room-and-pillar mining system, aiming to maximize the extraction at all coal faces from a given panel. The technique used was discrete-event simulation. After constructed and validated, the simulator proved to be efficient to forecast daily ROM production. Added to this, the simulator is able to help in visualizing bottlenecks and operations delays in the mining cycle. [ABSTRACT FROM AUTHOR]

Mine simulation depends on data that is both coherent and representative of the mining operation. This paper describes a methodology for modeling operational data which has been developed for mine simulation. The methodology has been applied to a case study of an open-pit mine, where the cycle times of the truck fleet have been modeled for mine simulation purposes. The results obtained have shown that once the operational data has been treated using the proposed methodology, the system variables have proven to be adherent to theoretical distributions. The research indicated the need for tracking the origin of data inconsistencies through the development of a process to manage inconsistent data from the mining operation. [ABSTRACT FROM AUTHOR]

The Radial Constriction Consolidation (RCC) process can be considered a powder metallurgical technique that allows for the fabrication of components with complex geometries, near-net-shape and full density at low production costs when compared to the traditional process. In some aspects, the RCC process is similar to the hot isostatic pressing process, but it uses a ceramic mold confectioned by investment casting and a powder as a secondary pressing media, all of which are confined in a metallic container. In this paper, a RCC experimental system was developed aiming to produce iron billets with the characteristics of near-net- shape and high density. Clay powder was used as a secondary pressing media. The obtained billets were characterized in terms of density, microstructure and hardness. It was observed that the configuration of the metallic container/ secondary pressing media/ceramic mold has an important influence on the characteristic of density and near-netshape of the billets. The billets presented satisfactory powder consolidation as shown in their microstructure, high density, elevated hardness, little oxide formation and a direct correlation between the values of density and hardness. [ABSTRACT FROM AUTHOR]

One of the major challenges for the mining industry is to supply the processing plant with ore that meets its specifications for maximizes production. This can only be achieved if proper knowledge of the geological domains of the orebody is acquired. However, this condition is not sufficient: once the geological domains of the orebody are properly known, it is also necessary to model the geological grades using estimation techniques such as kriging. The challenge for mining companies is to establish sampling processes and techniques that allow the appropriate estimation of the geological grades of the mined out ore. This paper presents a comparative analysis between three sampling methods and their impact on the estimation of the geological grade at the mine face in a case study carried out at the Cajati mine of Bunge Fertilizantes S/A, located in Sao Paulo, Brazil. [ABSTRACT FROM AUTHOR]

Reduced activation ferritic-martensitic (RAFM) steels display low-level radioactivity after their lifetime and have been considered for applications in fusion technology as structural materials. Unique properties such as good mechanical strength at high temperatures, good formability, high toughness and good oxidation resistance are found in these steels. Upon air cooling, they form a soft martensite (around 20 Rockwell C) when heated above the A1 temperature. These steels are usually employed in the as-tempered condition. This class of steels has a very refined microstructure that varies from fully martensitic to fully ferritic. To improve creep strength, this structure can be strengthened by a fine dispersion of particles (Y-based compounds and M23C6-type carbides). The main characteristics of these steels will be presented and discussed in the present paper. [ABSTRACT FROM AUTHOR]

This paper features a tool to carry out environmental performance evaluation in highway rehabilitation works, as a component of environmental supervision activities. The procedure involves (i) evidence gathering by conducting technical inspections and reviewing environmental compliance reports, (ii) ranking nonconformities according to a proposed weighting framework, and (iii) calculation of an environmental conformity index. For the sake of testing and calibration, the procedure was applied to five road segments that were submitted to rehabilitation works in São Paulo State and the results were treated qualitatively. [ABSTRACT FROM AUTHOR]

The current processing study seeks to improve operations for the direct and reverse flotation of apatite originating from carbonatically-affiliated rocks to obtain an apatite concentrate in accordance with the phosphoric acid industry specifications. The direct flotation of apatite was carried out in two flotation phases, rougher and cleaner. The aim of direct flotation was to generate a product to feed the reverse flotation circuit of apatite. Reverse flotation was performed in three stages (rougher, cleaner and recleaner) and at pH 5.0, using phosphoric acid (H3PO4) as an apatite depressor. Summing up, the results of reverse flotation tests pointed out apatite recovery, which shows that the specific reagents used favored system selectivity. It was possible to obtain an apatite concentrate with 38.11% of P2O5, 50.98% of CaO, 1.07% of Fe2O3, 0.67% of MgO and ratio CaO/ P2O5 of 1.34 [ABSTRACT FROM AUTHOR]