Finite element analysis of non-isothermal elasto-\ud plastic multiphase geomaterials is presented. The\ud multiphase material is modelled as a deforming porous\ud continuum where heat, water and gas flow are taken into\ud account. The independent variables are the solid displacements,\ud the capillary and the gas pressure and the\ud temperature. The modified effective stress state is limited\ud by the Drucker-Prager yield surface for simplicity. Small\ud strains and quasi-static loading conditions are assumed.\ud Numerical results of strain localization in globally undrained\ud samples of dense, medium dense and loose sands\ud and isochoric geomaterial are presented. A biaxial\ud compression test is simulated assuming plane strain\ud condition during the computations. Vapour pressure\ud below the saturation water pressure (cavitation) develops\ud at localization in case of dense sands, as experimentally\ud observed. A case of strain localization induced\ud by a thermal load where evaporation takes place is also\ud analysed

This paper presents a formulation for a saturated and partially saturated porous medium undergoing large elastic or elastoplastic strains. The porous material is treated as a multiphase continuum with the pores of the solid skeleton filled by water and air, this last one at constant pressure. This pressure may either be the atmospheric pressure or the cavitation pressure. The governing equations at macroscopic level are derived in a spatial and a material setting. Solid grains and water are assumed to be incompressible at the microscopic level. The isotropic elastoplastic behaviour of the solid skeleton is described by the multiplicative decomposition of the deformation gradient into an elastic and a plastic part. The effective stress state is limited by the Drucker-Prager yield surface, for which a particular "apex formulation" is advocated. The water is assumed to obey Darcy's law. Numerical examples of strain localisation of dense and loose sand conclude the paper

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We propose a mechanical and computational model to describe the coupled problem fuid flow, deformation and cracking in variably saturated porous media. A classical poromechanical formulation is adopted and coupled with a phase-field formulation for the fracture problem. The latter has the advantage of being able to reproduce arbitrarily complex crack paths without introducing discontinuities on a fixed mesh. The obtained simulation results show good qualitative agreement with desiccation experiments on soils from the literature

In this paper a new methodology to simulate saturated soils subjected to dynamic loadings under large deformation regime (locally up to 40\% in equivalent plastic strain) is presented. The coupling between solid and fluid phases is solved through the complete formulation of the Biot's equations. The additional novelty lies in the employment of an explicit time integration scheme of the u-w (solid displacement -- relative fluid displacement) formulation which enables us to take advantage of such explicit schemes. Shape functions based on the principle of maximum entropy implemented in the framework of Optimal Transportation Meshfree schemes are utilized to solve both elastic and plastic problems

[1] A fully coupled thermohydromechanical (THM) finite element approach is used here to model the groundwater and saturation response of a typical salt marsh of the Venice lagoon (Italy) subjected to both tide fluctuation and flooding. The soil forming the marsh, whose relevant material parameters have been measured experimentally in the laboratory, is assumed to be an homogeneous multiphase porous medium, in a thermodynamic equilibrium state both in fully saturated and partially saturated conditions. More particularly, the study is aimed at analyzing separately the various couplings of several factors such as soil stiffness, water conductivity, capillary suction, and humidity exchange with atmosphere including also the occurrence of marsh flooding on the overall mechanical response of the marsh subjected to tidal oscillations of very narrow amplitude. From the analysis carried out so far, the numerical approach adopted here seems capable of describing most of the relevant features of marsh behavior, thus showing the importance of THM couplings to explain the groundwater pressure evolution induced by lagoon tide cycles. In addition, the model seems to provide some interesting explanations concerning the evolving instability of marsh scarps, which is one of the main causes of the rapid overall deterioration of the typical Venice lagoon landscape.

Summary In this paper, rate‐dependent plasticity is employed to regularize, for the scope of mesh independency, the numerical solution in strain localization process of multiphase geomaterials. Towards this goal, the viscoplastic Duvaut–Lions and the viscoplastic Perzyna models are implemented in an existing finite element code for multiphase porous media. Perzyna's model is then extended according to the non‐local approach, allowing for handling weakly rate‐sensitive materials for which viscoplasticity is not sufficient to meet numerical requirements. Assuming quasi‐static and isothermal conditions, the models are validated and applied in the numerical simulation of an undrained plane strain biaxial compression test on initially water‐saturated dense sand taken from the existing literature. An overview of the significant factors such as loading velocity and soil permeability in conjunction with viscosity on the formation of localization pattern is presented. The interaction of the two internal lengths introduced by non‐locality and viscosity is also discussed. Finally, the obtained results are analysed and compared emphasizing the capabilities and shortcomings of each regularization technique. Copyright © 2015 John Wiley & Sons, Ltd.

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