Assessment of Undrained Bearing Capacity of Foundations on Anisotropic Clay Slope Under Inclined Load

The development of marine energy requires reliable foundations, which may be located near submarine slopes. This paper utilizes the lower bound limit analysis (LBLA) to analyze the undrained bearing capacity of foundations on slopes with anisotropy and linearly increasing strength with depth. The anisotropic undrained strength (AUS) model is employed to simulate the anisotropy of the slope soil. This study considers five variables that affect the bearing capacity: the normalized foundation setback (L/B), load angle (θ), strength ratio (suc/γB), heterogeneous index (ρB/suc), and anisotropy ratio (re). Here, suc represents the soil strength obtained from triaxial compression tests, while ρ denotes the strength gradient. The results indicate that the bearing capacity increases with the increase in L/B, suc/γB, ρB/suc, and re, while the maximum bearing capacity corresponds to a load angle ranging from 75° to 90°. The failure modes of foundations under different boundary conditions were presented and discussed. To establish the relationship between the foundation bearing capacity and each variable, the multivariate adaptive regression splines (MARS) is introduced. The MARS results indicate that θ is the most significant variable, while the relative importance of L/B is the lowest; neither can be neglected in practical engineering. The empirical equation based on the MARS algorithm can accurately predict the bearing capacity of foundations in non-homogeneous and anisotropic clay. These results offer critical guidance for engineering practice, enabling efficient design of marine foundations near slopes while accounting for soil anisotropy and heterogeneous strength gradients, thereby reducing risks of instability in offshore energy infrastructure.