Analysis of bearing capacity and deformation of unsaturated expansive soil foundations under flood-induced lateral seepage
To investigate the impact of flood-induced seepage on foundation bearing performance, a comprehensive numerical analysis was conducted on the vertical ultimate bearing capacity of a strip foundation resting on unsaturated expansive soil. Utilizing the ABAQUS platform with the Modified Cam-Clay model, the coupled hydro-mechanical responses, seepage field evolution, and subsequent reduction in bearing capacity were systematically analyzed under both transient and steady-state conditions. The numerical results indicate that saturated hydraulic conductivity and matric suction are key parameters affecting foundation stability. Under the influence of transient hydraulic gradients, the negative pore-water pressure gradually dissipates, leading to a nonlinear decrease in matric suction and a reduction of up to 65% in the ultimate bearing capacity of the foundation. Furthermore, the infiltration process alters the subsoil failure mechanism, shifting the general shear failure observed in the initial unsaturated ground toward an asymmetric local failure concentrated beneath the footing edges. This study reveals the localized weakening mechanisms of unsaturated expansive soil foundations subjected to flood-induced lateral seepage and provides a quantitative basis for the risk assessment of infrastructure founded on unsaturated soils.