Speaker: Hao Wang

Date: Thursday 26th of September 2024, 1:15pm.

Abstract:

The Callovo-Oxfordian (COx) claystone has been selected as the host formation for the construction of an Underground Research Laboratory (URL) in France, aimed at assessing the properties of COx claystone potentially involved in the geological disposal of radioactive waste. The mechanical behaviour of this claystone is crucial to the excavation of the URL, particularly in understanding the excavation damage zone (EDZ) around the openings, which reveals complex damage states influenced by stress paths and the properties of the host rock, such as anisotropy. In this study, the damage and anisotropic behaviour of COx claystone were investigated through triaxial tests using different loading paths that may occur near the openings. To further explore anisotropic mechanical behaviour, triaxial samples were prepared along different directions, based on the angle between the axial loading direction and the direction perpendicular to the bedding plane. The stress-strain curves from the triaxial tests displayed an elasto-plastic pattern. The measured elastic moduli showed a slight decrease with increasing deviator stress, indicating damage behaviour. Additionally, the Young's modulus and shear strength varied with the loading angle, highlighting the anisotropic nature of the COx claystone.