Effects of non-homogeneity and anisotropy in the bearing capacity of geosynthetics-reinforced soil-strip foundations under unsaturated conditions

The ultimate bearing capacity of foundations is a key factor in ensuring the safety and reliability of critical transportation infrastructure. Field evidence shows that subgrade soils are often unsaturated, spatially variable, and anisotropic. However, most existing studies on reinforced soil foundations neglect these features, which can lead to notable discrepancies between theoretical predictions and actual performance. To address this gap, the present study develops a comprehensive framework for evaluating the bearing capacity of reinforced soil foundations. The approach incorporates the effects of soil anisotropy and non-homogeneity on effective cohesion, and introduces an anisotropic soil–water characteristic curve model to capture their influence on hydraulic behavior. Analytical expressions are derived for the shear strength at the reinforcement–soil interface, explicitly accounting for heterogeneity and anisotropy, and a depth-dependent failure mechanism is established. The ultimate bearing capacity is then obtained through the framework of the upper bound theorem. Results highlight that both soil non-uniformity and anisotropy strongly affect the bearing capacity and the optimal reinforcement embedment depth. The proposed method provides a practical and reliable reference for designing reinforced foundations in complex geological environments.