On the swelling behavior of shallow Opalinus Clay shale

The Opalinus Clay shale is the selected geological formation for the construction of a deep geological repository in Switzerland. The geomaterial will experience cyclic drying and wetting paths during different stages of the repository lifetime. The shale, characterized by transversely isotropic behaviour, has the capacity to swell/shrink upon suction variation. The impact of suction variation on the shale behavior is therefore of interest. This paper presents the results on a shallow sourced sample, subjected to a complete hydric cycle in a wide range of applied suction (from ≈0 to 300 MPa). The results highlight the anisotropy in the shale strains and its evolution during the cycle, while slight irreversible strains cumulate.