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.

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Resultados da Pesquisa

Agora exibindo 1 - 10 de 17
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    Blast-induced ground vibrations : a dynamic analysis by FEM.
    (2022) Zorzal, Caroline Belisário; Nogueira, Christianne de Lyra; Lima, Hernani Mota de
    The peak particle velocities (PPV) are fundamental for understanding and managing the levels of blast-induced ground vibrations and their effects on adjacent structures. Given that numerical analysis of seismic vibrations has been demonstrated to be a method that can significantly contribute to predicting PPV, this study adopts a numerical approach using the finite element method (FEM) to assess blasting-induced ground vibration in rock masses. A dynamic module of the stress-strain analysis based on the FEM displacement formulation is developed in ANLOG software to estimate the variations of displacement, velocity, strain, and stress induced by blasting. The dynamic modulus implemented is verified using two verification examples. After, ANLOG is used in an application example to estimate seismic vibrations induced by blasting and to define the attenuation law for a limestone quarry near an urbanized area in Spain. The effect of Rayleigh damping coefficients (α and β) on the PPV levels estimated by ANLOG was investigated, and the most appropriate numerical attenuation law is then obtained. The numerical analysis presents satisfactory results for elastic-wave propagation induced by blasting and the peak particle velocity values obtained shows good agreement with field and the numerical results available in the specialized literature. The results indicate that ANLOG can perform personalized analysis of rock mass under blast-induced dynamic stress taking into consideration the geological and geomechanical characteristics particular to each medium as well as the blast parameters.
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    Thermohydraulic flow problem in unsaturated porous media : FDM computational model.
    (2020) Souza, Karla Baêta e; Nogueira, Christianne de Lyra
    The moisture and heat fluxes in undeformable unsaturated porous media involve the movement of water, air, and heat that are induced by thermal and pressure gradients to which the porous medium is subjected under environmental conditions. Herein, the flow of the liquid phase is governed by the advective flow due to the hydraulic gradient and by the convective heat transfer due to the thermal gradient. The flow of the gas phase is governed by the advective flow due to the pressure gradient and the nonadvective flow of dry air and water vapor diffusion. The heat transport can be carried out by conduction, convection, and advection due to the pressure gradient. The mathematical model includes the air mass conservation, water mass conservation, and thermal energy conservation equations. This paper presents a detailed computational model based on the finite difference method (FDM) for one-dimensional analysis of the flow problem of heat and moisture in undeformable unsaturated porous media. Verification examples involving unsaturated flow analysis in isothermal and nonisothermal conditions are presented, highlighting the importance of having a relatively simple computational model to analyze a very complex physical problem.
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    Propagação de ondas mecânicas unidimensionais : uma análise numérica Via MDF.
    (2020) Zorzal, Caroline Belisário; Pereira, Amanda de Barros; Flávio, Mayra Vitorino Freitas; Nogueira, Christianne de Lyra
    As ondas mecânicas têm a capacidade de transportar energia através do meio em que se propagam e, em muitas situações, elas apresentam um grande potencial de dano. Daí a importância da previsão e controle de sua intensidade. O estudo do fenômeno da propagação de ondas mecânicas é de suma importância para diversas áreas da engenharia e constitui um problema de difícil solução inclusive para situações unidimensionais. Dessa forma, por meio da abordagem numérica, apresenta-se um modelo computacional com base na aproximação explícita do Método das Diferenças Finitas (MDF) para solução de problemas mecânicos unidimensionais de equilíbrio dinâmico. O modelo computacional é verificado através da análise da propagação de uma onda mecânica numa coluna, constituída por um material isotrópico com comportamento constitutivo linear elástico, engastada em uma extremidade e submetida a um carregamento periódico em sua extremidade livre. Os resultados numéricos são comparados com os resultados analíticos obtidos na literatura específica. Em seguida, o algoritmo é aplicado na análise da influência da intensidade do carregamento periódico, da geometria e das propriedades elásticas da haste, na amplitude dos movimentos. Pode-se concluir que a amplitude dos deslocamentos aumenta, como era esperado, com o aumento da amplitude do carregamento e da altura, e diminui com o aumento do módulo de Young. Observa-se também que a velocidade de propagação diminui com a diminuição do módulo de Young.
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    Physical and geometric non-linear analysis using the finite difference method for one-dimensional consolidation problem.
    (2019) Pereira, Ronald Dantas; Nogueira, Christianne de Lyra
    This article presents a numerical model based on the finite difference method for the physical and geometric non-linear analysis of a one-dimensional consolidation problem regarding a saturated, homogeneous and isotropic soil layer with low permeability and high compressibility. The problem is formulated by adopting the void ratio as the primary variable, considering a Lagrangian movement description. The physical non linearity is introduced on the formulation by the constitutive law defined as effective stress and permeability void ratio functions. Based on this numerical model, a computational system named AC-3.0 was developed, which has been verified and validated in terms of the temporal variation of the void ratio distribution throughout the soil layer, by comparing the numerical results with analytical and numerical solutions found in literature for some specific scenarios. Knowing the void ration distribution,it is possible to obtain secondary variables such as: superficial settlement, effective stress and excess of pore water pressure.The importance of the non-linear formulation is highlighted for the analysis of problems related to material presenting high compression and a very high initial void ratio.
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    Coupled numerical simulation of a tailings deposit by FEM.
    (2019) Braga, Ana Luiza Coelho; Nogueira, Christianne de Lyra
    Researchers have found that a valuable alternative for predicting the mechanical behavior of landfill construction is numerical simulation based on the finite element method. The results of such a numerical simulation for a sandy tailings deposit from the iron mining coupling flow and deformation are presented herein. This study investigates the influence of the construction rate, drainage system, and anisotropy of permeability on the magnitude of pore pressures generated during the construction process. The study also presents the results from different analyses considering different constitutive models including elastic, nonlinear elastic and nonlinear elastoplastic. In obtaining the constitutive parameters, the numerical results highlight the importance of having a more detailed set of conventional triaxial compression tests. Also highlighted by the numerical results is the importance of having an efficient drainage system and the necessity of taking into account the water level variation in the hydromechanical behavior of numerical simulations of landfills that are hydraulically constructed.
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    Nonlinear equilibrium and stability analysis of axially loaded piles under bilateral contact constraints.
    (2015) Silveira, Ricardo Azoubel da Mota; Maciel, Felipe Vieira; Silva, Andréa Regina Dias da; Machado, Fernando Carlos Scheffer; Nogueira, Christianne de Lyra
    This paper presents a nonlinear stability analysis of piles under bilateral contact constraints imposed by a geological medium (soil or rock). To solve this contact problem, the paper proposes a general numerical methodology, based on the finite element meth-od (FEM). In this context, a geometrically nonlinear beam-column element is used to model the pile while the geological medium can be idealized as discrete (spring) or continuum (Winkler and Pas-ternak) foundation elements. Foundation elements are supposed to react under tension and compression, so during the deformation process the structural elements are subjected to bilateral contact constraints. The errors along the equilibrium paths are minimized and the convoluted nonlinear equilibrium paths are made tracea-ble through the use of an updated Lagrangian formulation and a Newton-Raphson scheme working with the generalized displace-ment technique. The study offers stability analyses of three prob-lems involving piles under bilateral contact constraints. The anal-yses show that in the evaluation of critical loads a great influence is wielded by the instability modes. Also, the structural system stiffness can be highly influenced by the representative model of the soil.
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    Validation of coupled simulation of excavations in saturated clay : Camboinhas case history.
    (2011) Nogueira, Christianne de Lyra; Azevedo, Roberto Francisco de; Zornberg, Jorge Gabriel
    This paper presents the results of an elastoplastic finite-element back analysis of an excavation made on a saturated soft organic clay deposit in Rio de Janeiro, Brazil. The excavation was conducted as part of an urbanization program, in which artificial islands were to be created in a swamp along the margins of the Camboinhas Lagoon. An extensive laboratory testing program was performed on undisturbed soil samples to characterize the stress-strain-strength behavior of the involved materials. Results from this laboratory testing program were used to calibrate a nonassociated elastoplastic constitutive model implemented in the ANLOG (Nonlinear Analysis of Geotechnical Problems) code. This code is based on the finite-element method and is capable of conducting fully coupled analyses by using a variety of constitutive models. Coupled analyses were performed to simulate the Camboinhas excavation, which was conducted under plane strain condition. Field measurements of both displacements and pore-water pressures obtained during the excavation are compared with the results of the numerical simulation. Analyses of the results show that monitored in situ and numerical results are in good agreement.
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    Formation of secondary containment systems using permeation of colloidal silica.
    (2011) McCartney, John S.; Nogueira, Christianne de Lyra; Homes, Daniel; Zornberg, Jorge Gabriel
    U.S. Environmental Protection Agency (USEPA) regulations require the capture of spills from liquid tanks containing hazardous chemicals by using a secondary containment system. Compacted clay or geomembrane liners are commonly used in secondary containment systems, but they are cumbersome when used in conjunction with existing liquid tanks because of pipeline networks surrounding the tanks. This study evaluates the formation of hydraulic barriers for secondary containment through the permeation of colloidal silica grout. A simplified infiltration model is presented to predict the downward movement of the colloidal silica grout into a soil layer, considering the timedependent increase in dynamic viscosity of the colloidal silica for different concentrations of an electrolyte accelerator. Because the simplified infiltration model cannot predict the soil-grout interaction or the permeation of the colloidal silica by fingering, its results were calibrated by using the observations from a large-scale column test involving the permeation of colloidal silica into sand. The predicted position of the wetting front was found to match that of the experiment when the parameter governing the change in viscosity of the colloidal silica was increased by a factor of 30. The infiltration model calibrated with observations from column infiltration experiments provides a simple approach to the design of the secondary containment systems using permeation of colloidal silica.
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    Coupled analyses of excavations in saturated soil.
    (2009) Nogueira, Christianne de Lyra; Azevedo, Roberto Francisco de; Zornberg, Jorge Gabriel
    This paper presents finite-element analyses of excavations by using a coupled deformation and flow formulation. Specific numerical procedures were implemented into the finite-element codes to simulate the excavation construction and to solve the nonlinear coupled system. The paper discusses results of two generic excavations, with analyses conducted using different constitutive models and different excavation rates. Although the constitutive model affected the magnitude and distribution of the excess of the pore-water pressure due to the excavation process, the constitutive models only slightly influenced the dissipation rate of the excess pore-water pressure. Excavation rates that were one order of magnitude smaller than the hydraulic conductivity of the soil led to results representative of drained processes. Because of the slow rate needed for drained conditions, partially drained conditions normally prevail during excavations, highlighting the importance of coupled analyses.
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    Use of the DCP test for compaction control of staged dikes in mining tailings dams.
    (2013) Resende, Lincoln Ribeiro Maia de; Oliveira Filho, Waldyr Lopes de; Nogueira, Christianne de Lyra
    Esse artigo descreve a utilização de um método alternativo de controle de qualidade na compactação de aterros em barragens de rejeitos de mineração. O procedimento faz uso de um penetrômetro, conhecido pela sigla DCP (Dynamic Cone Penetrometer), de maior emprego na construção de estradas (avaliação da qualidade de camadas de pavimento). Com esse aparelho, pode ser feita a medição de resistência das camadas superficiais de solos naturais ou compactados, incluindo os rejeitos arenosos de mineração, de forma rápida e eficaz. O instrumento foi utilizado com sucesso no acompanhamento do alteamento de uma barragem de rejeitos de minério de ferro no Quadrilátero Ferrífero, Estado de Minas Gerais, e os resultados mostraram uma efetiva densificação das camadas compactadas, porém de forma irregular no que tange à distribuição espacial no corpo da barragem. Além disso, o controle da compactação também foi feito com método tradicional do cilindro biselado, permitindo a comparação das duas técnicas.