In the process of energy transition towards low-carbon energy sources, efficient and large scale storage solutions need to be developed, as renewable energies are intermittent. Hydrogen is considered as a promising energy carrier but massive storage of green hydrogen is still a major issue to be solved. Underground storage in salt caverns of hydrogen is one possible option as this mean of storage has been in use for decades for hydrocarbons. However, the hydrocarbon storage/withdrawal cycles used to be seasonal, whilst the new applications to hydrogen could imply as short as daily cycling. The adaptation to short-term hydrogen storage still requires further studies to ensure the stability of the caverns under such loading conditions.
Rock salt is a viscoplastic polycrystalline material. Different mechanisms are involved in its mechanical behaviour, such as crystal slip plasticity and grain boundary sliding.The presence of brine also affects the micro-mechanisms involved and thus the behaviour of rock salt.
The characterization of the different micro-mechanisms under triaxial conditions, representative of those in real underground caverns, is an essential step to assess the integrity and tightness of the cavern in operation.

Our studies aim at characterizing the development of damage networks in synthetic halite, through in situ X-ray microcomputed tomography (XR-$\mu$CT) analysis and digital volume correlation (DVC) and damage quantification. A triaxial device adapted to in situ XR-$\mu$CT tests has been recently developed and allow us to study the deformation of synthetic rock salt under different confining pressures. In addition, in order to study the effect of brine content, we study samples prepared in dry and humid conditions.