Effect of fracture voids on the swelling behaviour of Callovo-Oxfordian claystone

• Published in: Engineering geology 2021-01, Vol.280, p.105935, Article 105935
• Main Authors: Zhang, Feng, Cui, Yu-Jun, Conil, Nathalie, Talandier, Jean
• Format: Article
• Language: English
• Subjects: Applied geology; COx claystone; Earth Sciences; Fracture voids; Sciences of the Universe; Sealing; Swelling behaviour
• ISSN: 0013-7952; 1872-6917
• DOI: 10.1016/j.enggeo.2020.105935

The Callovo-Oxfordian (COx) claystone has been considered as a possible host rock for deep geological repository of high-level radioactive waste in France. When constructing the repository, it is unavoidable to generate a fractured zone in the vicinity of excavated repository walls. In the assessment of the repository performance, it is important to investigate the role of the fractures on the swelling capacity of COx claystone and to further characterize the fractured zone evolution. In this study, the effect of fracture voids on the swelling behaviour of COx claystone was investigated by simulating the fracture voids with a space created by a limited amount of grains sandwiched between claystone disks, and by performing a series of swelling tests in oedometer under a low vertical stress (0.05 MPa) and swelling pressure tests under constant-volume condition. Results showed that, with water infiltrating into the sample with fracture voids, the grains collapsed before the swelling of claystone disks. The whole sample was composed of swelling zones corresponding to the claystone disks with higher dry density than the expected final value, and of compression zones corresponding to the initial fractures with lower dry density. Moreover, the axial strain and swelling pressure decreased as the fracture void increased. The maximum fracture voids that might be fully filled by the swelling of COx claystone (sealing) were found to be 5.14%–7.65% without considering the long-term creep contribution in the field condition. •Fractures were simulated with soil grains of defined sizes.•Water infiltration led to collapse of soil grains first prior to claystone swelling.•The swelling zones corresponded to claystone disks.•The compression zones corresponded to initial fractures.•A maximum fracture voids that might be sealed was 5.14%–7.65%.