Extended Kelvin–Voigt Model for Simulating Thermally Accelerated Creep in Fine-Grained Soils

The subsurface undergoes temperature variations in many situations due to anthropogenic and natural causes, which strongly influence the long-term behavior of soils. These phenomena can involve temperature anomalies in the ground across distances of a few meters, as in the case of nuclear waste repositories, to distances encompassing entire cities, as in the case of subsurface urban heat islands. To date, a number of constitutive models have been proposed to capture the mechanics of soils under non-isothermal conditions, with particular attention to fine-grained soils due to their renowned sensitivity to temperature variations. However, most of the available models suffer from many constitutive parameters that hinder their applicability to the analysis of large and complex problems involving thermally induced deformations of fine-grained soils. This study extends the classical Kelvin-Voigt model with a temperature-dependent formulation for capturing the reversible or irreversible thermally induced deformations of fine-grained soils, interpreted through the theory of thermally accelerated creep. Implemented in a finite element software and validated against experimental data, the model shows that the thermally induced deformations of fine-grained soils are highly sensitive to the temperature variation rate, while they are little influenced by the magnitude of the applied mechanical loads. The proposed model effectively captures the complex, time-dependent deformations of fine-grained soils with only a few easily calibrated parameters, making it a practical tool for the long-term analysis of thermally induced creep in such materials.