The Heaviside-based digital image correlation (H-DIC) method, a new technique capable of accurately investigating the kinematics of cracks (displacement, opening/closure, sliding) was used on a cubic sample of clay rock taken from the Meuse/Haute-Marne Underground Research Laboratory (URL) at Bure (France). This sample was subjected to a controlled thermal loading (25°C-90°C) and a controlled hygrometry (62% relative humidity).

The results obtained confirmed that (a) the dominant mode of opening of desiccation cracks is type I (i.e., opening/closing is dominant over sliding) and (b) that desiccation cracking occurs parallel to bedding. Our results also illustrate two antagonistic effects from a thermo-hydro-mechanical point of view. On the one hand, the water loss associated with heating contributes to shrink the sample but on the other hand, the heating of the rock contributes to thermally expand the sample.

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