Crack-hydro-deformation analysis of expansive soil: Implications on heave-subsidence response

In arid regions, expansive soils along pavement shoulder and adjacent zones undergo pronounced seasonal moisture fluctuations, resulting in repeated swelling and shrinkage cycles and progressive formation of interconnected desiccation cracks. These cracks act as preferential flow paths, yet their influence on moisture dynamics and subgrade deformation remains largely unexplored. This study employs a numerical approach using an unsaturated dual-permeability model to investigate coupled effects of desiccation cracking, transient moisture flow, and subgrade deformation in expansive soil deposit under transient climatic conditions. The model parameters were experimentally determined for a naturally occurring, highly expansive soil based on the soil water retention curve, soil shrinkage curve, and hydraulic conductivity function. The climatic variations recorded at Trichy, India (rate of rainfall, rate of potential evaporation, relative humidity and temperature) were used. The simulation results at the end of dry and wet seasons revealed that desiccation cracks significantly alter moisture distribution and contribute to differential heave and subsidence in the subgrade. The developed crack network facilitates deep infiltration, leading to differential vertical deformation in the subgrade along the pavement edges. A parametric study further demonstrated that increasing crack depth amplifies moisture ingress and hydro-deformation responses, leading to more severe pavement distress.