Modeling Of Excavation Damaged Zone Through The Strain Localization Approach In Boom Clay

Deep disposal of the high-level nuclear wastes in the potential geological formations is a promising option for the long-lived radioactive waste management. A damaged zone with significant irreversible deformations and important host rock's properties changes is expected to be created around the underground galleries due to the excavation process that this zone is called as Excavation Damaged Zone (EDZ). The excavation process of the Connecting gallery in the Boom clay formation (Mol, Belgium) is analyzed in this study. Since during its construction, the localized crack propagation was observed around the gallery, we propose to analyze the EDZ and its extension around the Connecting gallery in the framework of strain localization approach. Numerical modeling of strain localization needs a specific approach to overcome the practical problem of mesh size dependency within the framework of classical finite elements. Therefore, the second gradient method as an enhanced technique is applied to adjust this problem. This study is aimed to model the coupled hydro-mechanical behavior of the Boom clay host-rock during the construction of the Connecting gallery. A quarter of the gallery is studied by symmetry in the plane strain conditions and under the initial anisotropic stress state providing the information on the evolution of strain localization in shear bands mode accomplished by the extension of EDZ. In addition, considering a concrete lining on the gallery wall, a discussion on the contact pressure on the interface between the massive and the lining is performed simultaneously by the evolution of shearing bands in the vicinity of the gallery.