Investigation of the Behavior of Shallow Foundations with Different Shapes and Burial Depth Ratios Using the Finite Element Method

The distribution of contact stresses beneath shallow foundations governs both structural demand within the footing and the deformation response of the supporting soil. Although numerous analytical and numerical studies have investigated soil–foundation interaction, the combined influence of foundation geometry and embedment ratio on contact stress distribution, settlement behavior, stress bulb development, and foundation rigidity has not been systematically evaluated within a unified numerical framework. This study presents a comprehensive finite element investigation of shallow foundations with circular, square, and strip geometries subjected to four embedment ratios (Df/B, where Df denotes the embedment depth and B the footing width) of 0.25, 0.50, 0.75, and 1.00, considering six representative soil profiles ranging from soft clay to dense sand. A total of 216 numerical simulations were performed using PLAXIS 2D (version 2024.1) under drained conditions, employing the Mohr–Coulomb constitutive model. The numerical setup was checked against classical analytical stress and settlement solutions under corresponding idealized conditions. The results demonstrate that increasing embedment consistently reduces peak contact stresses, decreases foundation settlement, and produces shallower stress bulbs over the investigated range of Df/B. Within the adopted 2D numerical framework, the circular-footing representation exhibits the most uniform contact stress distribution and the lowest settlements, whereas the strip-footing representation develops the highest stress concentrations and deepest influence zones. In addition, a depth-adjusted formulation of the Relative Stiffness Factor is proposed to account for the increase in operative soil stiffness associated with embedment, providing a framework for evaluating the relative rigidity of embedded foundations. The findings provide quantitative insight into the influence of foundation geometry and embedment depth on stress transfer and settlement performance, thereby supporting the comparative assessment of shallow foundation behavior within the investigated conditions.