Numerical analysis via MEF of poroelastic problems: Análise numérica via MEF de problemas poroelásticos

This paper presents a fully coupled hydro-mechanical formulation, based on the finite element method in terms of the displacement and pore-water pressure, taking into account the effect of relative compressibility between the grains and the solid skeleton. Its main goal is to provide a clear formulation and reference examples to facilitate reproduction by anyone which intend to develop their own computer program to solve poroelasticity problems. The numerical model presented is verified with analytical solutions of problems in plane strain condition and others authors numerical results. The influence of material properties on the pore-water pressure dissipation process and, the performance of the time integration scheme are presented. Higher the Poisson’s coefficient and lower the grain compressibility faster is the process of dissipation highlighting the importance of taking into account the relative compressibility between the grains and the solid skeleton on the coupled analyses. The Crank Nicholson’s algorithm presents a good performance when comparing with other time integration scheme presented by other authors

Isotropic work softening model for frictional geomaterials : development based on lade and kim constitutive soil model.

An isotropic softening model for predicting the post-peak behavior of frictional geomaterials is presented. The proposed softening model is a function of plastic work which can include all possible stress-strain combinations. The development of softening model is based on the Lade and Kim constitutive soil model but improves previous work by characterizing the size of decaying yield surface more realistically by assuming an inverse sigmoid function. Compared to original softening model using the exponential decay function, the benefits of using the inverse sigmoid function are highlighted as: (1) provide a smoother transition from hardening to softening occurring at the peak strength point, and (2) limit the decrease of yield surface at a residual yield surface, which is a minimum size of yield surface during softening. The proposed softening model requires three parameters; each parameter has it own physical meaning and can be easily calibrated by a triaxial compression test. Data from triaxial compression testing on Monterey No. 30 sand is applied to demonstrate the calibration procedure and examine the variation of model parameters with different loading conditions. Results show all parameters are highly correlated to confining pressures. The proposed softening model can provide a useful tool for evaluating those structures on which the post-peak behavior of frictional materials should be emphasized, e.g. earth structures under large loading or deformation conditions or the structures having an intensive soilstructures interaction, etc

Propagação de ondas mecânicas unidimensionais: uma análise numérica Via MDF / Propagation of mechanical waves in one-dimensional: a numerical analysis Via FDM

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 Youn

Physical and geometric non-linear analysis using the finite difference method for one-dimensional consolidation problem.

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

Physical and geometric non-linear analysis using the finite difference method for one-dimensional consolidation problem

Abstract 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

Coupled numerical simulation of a tailings deposit by FEM.

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

Coupled numerical simulation of a tailings deposit by FEM

Abstract 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 hydro-mechanical behavior of numerical simulations of landfills that are hydraulically constructed