The present work explores the numerical modelling of the hydro-mechanical behaviour of the fractured zone in deep nuclear waste disposal schemes. This includes simulation of Callovo-Oxfordian argillite (COx) swelling, cracks estimation of fractured COx, coupled the hydro-mechanical behaviour of COx, self-sealing of fractured COx and the fractured zone by the means of mechanical loading and hydration. Callovo-Oxfordian argillite is a claystone with the properties of both soils and rocks. Therefore, Van Genuchten model (1980), which usually was used to describe water retention of soils and rocks, is employed to simulate water retention of COx. The relations between tensile strength, fracture energy, Young Modulus and water content of COx are formulated for application in numerical analysis. The Biot's model conbining to an extra deformation upon to the desaturation/resaturation is proposed to describe the deformation of rock under hydric and mechanical loading. The Von Mises yielding standard, Nadai criterion and the damage model (Fichant et al., 1999) are employed to analyse the plastic damage behaviour of COx. Crack opening/closure of unsaturated fractured COx samples is estimated using a post-processing method based on fracture energy regularization. Based on the crack width estimation, the permeability of fractured material is evaluated using the Cubic Law. Taking into account the permeability resulting from cracks, an classical model of hydraulic diffusion in fractured unsaturated COx has been formulated and executed in the Finite Element code CasT3M. Uniaxial compression tests under relative humidities of 32%, 44% and 76%, and triaxial compression tests with confining stresses of 0MPa, 2MPa, 6MPa, 12MPa under a relative humidity 90% are simulated and compared with experiments, which prove the reliability of the proposed model for describing the hydro-mechanical behaviour of COx. One of the most important properties of COx is its swelling potential upon saturation. In this respect, free and restrained swelling during hydration are simulated, and a good agreement between numerical and experimental results are obtained. The self-sealing potential of fractured COx is evaluated by means of numerical simulations. This analysis is based on laboratory tests and in-situ test CDZ (compression damage zone) performed within the Meuse/Haute-Marne Underground Research Laboratory. Laboratory tests show that the global gas permeability declined from 10-14 m2 to 10-16 m2 following an increase of XVII confining pressure from 0MPa to 17MPa. Self-sealing of fractured COx was accomplished by injecting water into the samples, which produced an increase of the global water permeability to the levels of the intact COx. For CDZ tests, the global gas and water permeabilities produced by self-sealing of the fractured zone are similar to the laboratory values. Self-sealing of the fractured zone was observed when water flowed into the zone of connected fractures and the zone of diffuse fractures. The numerical simulations of small fractured COx samples show good consistency with experimental results. At the scale of the CDZ tests, the consistency between the numerical and experimental results is worse because it is not easy to obtain the same fracture pattern in numerical simulations and experiments. In conclusion, a plastic damage model is formulated successfully in this thesis, which behaves correctly in analyzing the hydro-mechanical behaviour of unsaturated COx claystone. The comparison between simulations and experiments shows that the model can predict self-sealing of cracked COx samples at the scales of both small samples and the fractured zone.