Numerical Simulation of Unsaturated Expansive Soil Behavior in a Changing Climate Using a Single Stress State Framework

Global climate change is expected to alter climate patterns this century, significantly affecting soil behavior through soil-atmosphere interactions. This study employs numerical simulations to examine the impact of climate change on the deformation of Regina clay in Regina, Canada. A key innovation is the development of a coupled hydro-mechanical model that integrates a soil-atmosphere boundary to simulate moisture dynamics using a single stress state framework for unsaturated soils. This approach simplifies analysis by incorporating suction stress and aligns with classical soil mechanics principles, enhancing model accuracy and predictability. Climate projections from the latest CMIP6 data were utilized, incorporating 26 general circulation models (GCMs) and three shared socioeconomic pathways (SSPs). By using climate data from multiple GCMs and SSPs, the study captures a wide range of potential outcomes, increasing the reliability of predictions. A novel structured approach was applied to select critical future climate scenarios, enabling a comprehensive analysis of soil deformation under historical and future climatic conditions. Results indicate a shift from historical shrinkage behavior to swelling dominance in expansive soils, with the maximum yearly ground movement projected to be 59 mm in 2063, surpassing the historical peak of 44 mm in 1998. Ground movement (heave) is anticipated to exceed historical levels by more than 20%, despite future precipitation increases of less than 20%. The study highlights that ground deformation is influenced more by the timing and sequence of extreme precipitation events than by peak daily rainfall, particularly during colder months with minimal evaporation.