Etude du comportement anisotrope de l’argile de Boom

Boom Clay, a transverse isotropic material, has been studied as one of the potential host rocks for HLW disposal. Its anisotropic THM properties was evidenced using measurements of thermal conductivity, hydraulic conductivity and small-strain shear modulus. Through these measurements on freshly cored samples (from the Connecting gallery at URL HADES), the damage due to excavation was identified and modelled using an empirical model based on the volume of macro-pores as damage variable. The anisotropy behaviour was studied under K0 condition (in the triaxial and oedometer cells) and through triaxial tests on three types of specimens (0°, 45°, and 90° to the bedding plane) by analysing the behaviour during and after the re-saturation under different stress states. The seismic waves velocity Vs et Vp were measured during the tests using the bender elements installed in the both bases of the triaxial cell to determine the anisotropic elasticity parameters. An anisotropic model with eight anisotropic parameters (fives elastic and three plastic parameters), based on an elasto-plastic isotropic model with two yield surfaces elaborated previously for Boom Clay (Hong, 2013), was developed using the theory of Boehler (Boehler et Sawczuk, 1977) and validated by the laboratory test results obtained in this study.