Generalized Plasticity and Cyclic Pressuremeter Test Modelling

A constitutive model based on generalized elastoplasticity (Zienkiewicz et al., 1985) is used for the modelling of monotonic and cyclic pressuremeter tests in a clay. The permeability of the material is taken into account for the modelling of the excess pore water pressure generation during the test (combination of pore pressure build up and dissipation). It is shown how this type of model can simply represent the main features observed during a cyclic pressuremeter test in a clay, particularly the accumulation of excess pore water pressure during the cycles of loading, and the importance of dissipation on the excess pore water pressure build up

Micromechanics Contribution to Coupled Transport and Mechanical Properties of Fractured Geomaterials

International audienceThis article is devoted to the modelling of interdependent mechanical and hydraulic behaviours of geomaterials in presence of a single through-wall fracture by means of micromechanics arguments. Experimental results of fractured concrete samples show non-linear evolutions for both mechanical and hydraulic behaviours with respect to confinement intensity. These non-linear responses are interpreted by the progressive closure of crack-like pores defining the pore volume of the fracture interfacial domain. Disregarding tortuosity effects, we adopt a 2D representation for these cracks. The key role of the fracture initial porosity is also emphasized. It allows to discuss the shape of the distribution of the local apertures distribution function classically used, intercepted here in terms of the distribution of initial crack–aspect ratio within the fracture domain. Application on fractured concrete samples shows the capability of the theoretical model to accurately reproduce the experimental results

Micromechanical approach to the behavior of poroelastic materials

A micromechanical analysis of the behavior of saturated elastic porous media is presented. Pores are connected and saturated with a fluid at uniform pressure. The non-linear macroscopic response of the porous medium is assumed to be related to the existence of a network of microcracks in the solid phase. The progressive closure of cracks during loading is viewed to control the material non-linearity. Using averaging schemes based on both the classical and modified secant methods, the non-linearity of the overall response is shown to be sometimes controlled by an effective stress. The modified secant method accounts in a certain way for the non-uniform distribution of strains within the solid phase. Different definitions of the effective stress are found, each of them being a combination of the overall stress with the fluid pressure. The hypothesis of connexion between pores and microcracks is discussed in details. The consequences of this hypothesis on the non-linear overall response are illustrated and comparisons are made with experimental data

PAROS : un logiciel de calcul de stabilité des ouvrages en soutènement.

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