Hydro-mechanical modelling of swelling in clayey host rocks for subsurface energy applications

This study presents a double-structured hydro-mechanical model for clayey host rocks, based on the Barcelona Expansive Model (BExM), to capture the evolution of porosity during swelling. The formulation distinguishes the effects of net stress and suction and assumes that elastic behaviour is associated with the microstructure, while induced macroporosity evolves plastically. The model was calibrated against oedometric swelling tests performed on Opalinus Clay Shale under constant load. The results show that swelling behaviour is strongly stress-path dependent and that larger swelling during resaturation leads to a reduction in preconsolidation stress, likely associated with the development of induced macroporosity along bedding planes. The proposed framework provides a useful basis for analysing the hydro-mechanical response of clayey host rocks in applications such as underground energy storage and waste disposal.