Multi-scale investigation of fracture apertures in clay rock subjected to desiccation

In the laboratory, the desiccation fracture apertures in Tournemire clay rock were investigated at different scales (millimetre and centimetre) and compared to the variations of the average water content and mean strains of the sample. The induced hydric strains and desiccation fractures were monitored by digital image correlation (H-DIC). At the centimetre scale, the results revealed the fracture aperture kinematics were separated into a first phase of opening and closure, and a second phase of only gradual closure. Closure of the cracks was only observed at the millimetre scale, revealing that the kinematics of cracks depends on the scale observed. The interpretation of the entire dataset emphasizes the need for a multi-scale approach to understand and model desiccation cracking mechanisms and their associated hydric strains in clay rocks.