Due to the increasing need to find new alternative energy sources, more attention has been given to the development of energy geostructures, which not only serve as foundations, but also employ the geothermal properties of soils for heating and cooling structures, inducing mechanical and thermal loads. Additionally, the up -growing effects of climate change are influencing the performance of foundations due to the increase in temperature and seasonal variations. The previously mentioned examples correspond to scenarios where soils are subjected to thermo-hydro-mechanical loading, which can vary cyclically. To predict this behavior, in this article a coupled thermo-hydro-mechanical hypoplastic model for partially saturated fine-grained soils that accounts for both monotonic and cyclic loading is presented. The proposed constitutive model is capable of reproducing temperature and suction effects at large strains and asymptotic states. Additionally, coupled effects are predicted by incorporating a Water Retention Curve (WRC) that depends on temperature and void ratio. Small strain stiffness effects are captured based on the Improvement of the Intergranular Strain concept (ISI), modified to include the influence of temperature under cyclic loading, as well as a temperature dependent secant shear modulus formulation at very small strains. The capabilities of the constitutive model were evaluated through element tests simulations of monotonic and cyclic mechanical loading tests under temperature- and suction- controlled conditions, as well as heating/cooling experiments at constant stress. The proposed constitutive model shows accurate predictions when compare to experimental data. Nevertheless, some limitations have been encountered and further discussed.
