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This study explores the elastoplastic response of Opalinus clay, a host rock for waste repositories, under thermo-mechanical loading. A fully coupled thermo-hydro-mechanical (THM) model is developed using a finite element model in COMSOL Multiphysics Software. The developed model is used to predict the THM response of a fully saturated sample of Opalinus clay in a hollow cylinder triaxial cell under different heating-cooling cycles in both drained and undrained conditions. The results demonstrate the importance of accounting for elastoplastic behavior and considering the effect of temperature on the THM properties of clay in predicting the stress-strain responses of claystone under THM loading. The role of drainage conditions is analyzed, and the results of pore pressure and volumetric strain are compared with experimental measurements, showing good agreement. A dilative behavior is seen in the heating phase until it reaches its highest experienced temperature and then a contraction behavior is observed, and the compression behavior is continued with the cooling phase in a naturally consolidated sample.
Mohammadzadeh et al. (Thu,) studied this question.