Comportement hydromécanique des argilites du Callovo-Oxfordien lors de cycles de désaturation-resaturation

Abstract : The Callovo-Oxfordian claystones properties make them reliable as a geological barrier for the confinement of radioactive wastes. In order to optimally predict their behavior, how they respond to various short and long terms loadings has to be studied. Particularly during the exploitation phase, air is continuously ventilated throughout the galleries. The climatic properties of this air are not balanced with those of the rock, and may perturb its hydromechanical (HM) attributes. Thus, assessing the HM response of the rock under hydric loading seems to be a priority.This dissertation begins with laboratory tests to propose an appropriate physical model. Drying tests were studied as they focus on the HM response of samples undergoing hydric loadings. A first 2D isotropic model is proposed, and then enhanced to 3D by considering a transversely isotropic Young modulus. Secondly, experimental results provide relevant data to estimate poroelastic and transport parameters involved in the model. Estimation is achieved according to an inverse procedure, which minimizes the error between measurements and model predictions. Finally, a real-size test is simulated using 2D models: an isotropic plastic one and a transversely isotropic elastic one.Model predictions reproduce well the laboratory tests data. When simulating the in situ behavior, a rather good agreement is obtained between the numerical and experimental results (although using the parameters estimated at the laboratory scale). However, the model highlights a limited influence of plasticity in the laboratory tests, while dissipative phenomena obviously occur in situ. 3D laboratory simulations do not improve the precision of 2D results, but reproduce more experimental data (mass variations, axial and lateral strains). Moreover, the inversion process is more efficient when ran over various kinds of data. Furthermore, stability of the algorithm is improved when adopting a two-phase convergence (simplex, followed by a gradient-like method). Numerical estimates of the parameters are in agreement with the direct experimental measurements obtained through other tests.
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Théophile Guillon. Comportement hydromécanique des argilites du Callovo-Oxfordien lors de cycles de désaturation-resaturation. Autre. Institut National Polytechnique de Lorraine, 2011. Français. ⟨NNT : 2011INPL101N⟩. ⟨tel-01749500⟩

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