Thermo-hydro-mechanical modelling of the heterogeneous subsidence and swelling in the desiccation cracked clayey strata

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Soil desiccation cracking as a consequence of severe environmental changes alters soil deformation mechanisms significantly. Therefore, this study aims to explore the effect of crack characteristics and environmental conditions on the heterogeneous deformation of desiccation-cracked soils using thermo-hydro-mechanical analyses. The model framework consists of balance equations, thermal, hydraulic, and mechanical constitutive equations, while the model scenarios were determined based on statistical analyses. The meteorological record of Qom city was used for three years, from 2015 to 2017, to capture long-term behaviour under wetting-drying cycles. Findings revealed that cracks extend the deformation range, potentially up to six times, with variation based on crack dimensions and spacing. Notably, narrower cracks experienced more pronounced deformation than wider ones. The cracked soil with a crack depth of 2.5 m showed 1.5 times higher swelling and subsidence than crack depth of 1 m. Furthermore, the wider cracks indicated a lower rate of increase in their dimensions compared to the initial state during drying. The investigation also highlights the mechanisms of soil surface shape due to swelling and shrinkage, resulting in concave and convex surfaces, respectively. The results provide new perspectives on the behaviour of fine-grained deposits in arid to semi-arid climates with deep groundwater levels.