EM - Escola de Minas
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/6
Notícias
A Escola de Minas de Ouro Preto foi fundada pelo cientista Claude Henri Gorceix e inaugurada em 12 de outubro de 1876.
Navegar
6 resultados
Resultados da Pesquisa
Item Long-term evolution of heap surface of paste tailings under erosion.(2022) Branches, André Miranda Brito; Lima, Hernani Mota de; Luz, José Aurélio Medeiros daMany mines are moving from conventional tailings storage facilities to filtered tailings disposal systems. The benefits of these systems include increased water recovery, reduced size of containment landfills, improved facility safety, and reduced environmental impact. In geotechnical terms, the challenges are to find the correct way of waste disposal: whether in piles of dry sandy tailings or co-disposal waste rock. The long-term evolution of the surface of fine and sandy tailings stockpiles is a matter of concern. The goal of this study was to quantitatively evaluate the temporal evolution of a paste tailings pile, using a computational model of landscape evolution. For this, SIBERIA, a simulator of the evolution of landscapes under the action of runoff and erosion, was used. The effect of erosion on a trunk-pyramidal tailings pile with about 21% of slope after long periods of decommissioning (100 and 250 years) was studied. The SIBERIA modelling data considered the surface roughness and the average diameter of the sediment particles and the typical properties of iron ore tailings. The results indicate that for a lower Manning roughness coefficient and larger average apparent diameter of the sediment particles (or clods), the lower the sediment transport will be and, therefore, in the long term, the greater will be the integrity of the tailings pile.Item A comparative evaluation of vertical fractures using different azimuthal electrical resistivity survey arrays.(2019) Moreira, Simone Aparecida Simim; Bacellar, Luis de Almeida Prado; Aranha, Paulo Roberto AntunesThe identification of geological discontinuities such as fractures and faults is fundamental to geotechnical and hydrogeological characterization of rock masses. It is difficult to characterize these discontinuities, even by means of drill cores. Electrical resistivity has been historically employed as an alternative tool for the characterization of discontinuities, and new equipment for data acquisition and modern interpretation techniques have increased this possibility. However, when the characterization of vertical discontinuities is to be carried out in small areas, such as urban zones or for engineering works, traditional surveying may be impracticable, because it requires larger areas for proper acquisition. In these situations, azimuthal electrical resistivity surveying can be a good option, thanks to faster data acquisition and the possibility of reaching greater depths of investigation. There are several types of azimuthal arrays, but comparative analyses of their efficiency are still scarce. The objective of this study is to compare the applicability of several types of azimuthal resistivity surveys to identify vertical discontinuities in rock masses. The study was carried out in the laboratory using a scale model (tank), where boundary conditions could be well‐defined. We tried to replicate the natural conditions of a karstic area in Brazil, known to have hydrogeological and geotechnical problems associated with subvertical discontinuities. The simulations involved a limestone rock mass crosscut by a set of discontinuities with varied apertures. The selected arrays (square, equatorial dipole–dipole, Wenner and Schlumberger) encompassed varied inter‐electrode spacings and three different thicknesses of a saturated isotropic overburden, so as to represent field conditions. The azimuthal resistivity surveys, especially the Wenner array, proved to be promising in order to detect vertical discontinuities. The non‐collinear arrays are preferable when it comes to discerning the depth of investigation (square) and detecting electric anisotropy (equatorial dipole–dipole), despite small azimuthal distortions that were observed in relation to the strike of the discontinuities.Item Artificial neural networks to prediction fuel rate in the blast furnace operation.(2018) Carvalho, Leonard de Araújo; Assis, Paulo SantosThis paper proposes the use of artificial neural networks for the prediction of fuel consumption in the blast furnace. For this purpose, a dataset of 270 records, with 19 input variables were considered, based on the historical data of operation from the years 2014 to 2017 of a blast furnace of a Brazilian steel mill, and it was verified that model presented good results with correlation coefficient of 0.837, consisting of an input layer with 19 neurons, intermediate layer with 19 neurons and output layer with 1 neuron.Item Fluid flow and mixing characteristics in RH degasser of Companhia Siderúrgica de Tubarão, and influence of bottom gas injection and nozzle blockage through physical modelling study.(2004) Silva, Carlos Antônio da; Silva, Itavahn Alves da; Martins, Ernani Márcio de Castro; Seshadri, Varadarajan; Perim, Carlos Alberto; Vargas Filho, Geraldo AlvesA physical model based on similarity principles has been constructed for simulating the RH degasser of Companhia Sideru´rgica de Tubara˜o (CST), Vito´ ria, ES, Brazil. The influence of gas injection through nozzles in the upleg with simultaneous bottom injection of gas, as well as the influence of nozzle blockage, on the circulation rate has been investigated. In addition, mathematical relationships for mixing characteristics in the process have been evaluated.Item Modelling moisture distribution and isothermal transfer in a heterogeneous porous material.(1995) Philippi, Paulo César; Souza, Henor Artur deThis paper presents a study of moisture retention and isothermal transfer in a cement and lime mortar. The extended range of pore sizes and the intrinsic heterogeneity of the medium do not allow the use of a single-scale percolation network for numerically describing the topology and the physical processes related to fluid retention and transfer. Three different scales are used for the numerical description of the cement and lime mortar studied in this paper. Electron scanning pictures are used for the geometrical modelling of the material in the three different scales. The heterogeneity is associ,~ed with the fissures network, represented in the first scale, where the medium was conceived as a series of cubic blocks separated by straight channels. The second and third scale are used to represent the pores in the cement and lime paste. A 3D simple cubic percolation site network is used in the third scale to model imbibition and drainage and to predict the hydraulic conductivity in terms of the moisture content. In the second scale, pores are represented as embedded bodies in a continuous medium and the hydraulic conductivity is calculated using Maxwell De Vries theory for composite media. At the first scale level, the isothermal mass diffusivity D~ is modelled by studying an invasion process of liquid water into the fissures network, simulating an actual imbibition experiment, from one extremity of a sample column. Finally, the results of the simulation are compared with experimentally obtained values of Do.Item A physical modelling study of inclusion removal in tundish using inert gas curtain.(2012) Seshadri, Varadarajan; Silva, Carlos Antônio da; Silva, Itavahn Alves da; Araújo Júnior, Ely da SilvaThe control and minimization of non-metallic inclusions content in the tundish and in the mold of a continuous casting unit is crucial for ensuring the final quality of the steel cast product. Nonmetallic inclusions of sizes smaller than 15 m are hard to remove, as they are difficult to float. They are easily carried by the flow of steel melt into the mold and adversely affect the steel cleanliness. It is suggested that a gas curtain made of small bubbles of argon can be used to capture and remove these inclusions in the tundish, thus avoiding their transport into the mold. A 1:3 scale physical model of tundish of the continuous casting unit of ArcelorMittal plant, in Vitória, Brazil, was built to investigate the effects of gas flow, shape and positioning of the gas curtain inside the tundish, on the efficiency of removal of inclusions. The results suggest that the gas bubbling inside the tundish can be effective in inclusion removal. The efficiency is dependent upon the location of argon bubbling.