Sources such as wind or severe seismic activity often exert extreme lateral loading onto the shallow foundations supporting high-rise structures such as bridge piers, buildings, shear walls, and wind turbine towers. Such loading conditions may cause the foundation to exhibit nonlinear responses such as uplift and bearing capacity mobilization of the supporting soil (i.e., rocking behavior). Previous numerical and experimental studies suggest that while such inelastic behaviors may engender residual deformations in the soil–foundation system, they offer potential benefits to the overall integrity of structures through dissipating energy and reducing inertia forces transmitted to the superstructure, thereby limiting seismic demand on structural elements. This study investigates the effect of footing shape on the rocking performance of shallow foundations in different subgrade densities and initial vertical factor of safety (FSv). To this end, a series of reduced-scale slow cyclic tests under 1 g condition were conducted using a single degree of freedom (SDOF) structure model. The performance of different footing shapes was studied in terms of moment capacity, recentering ratio, rocking stiffness, damping ratio, and settlement. For three foundations with different length-to-width ratios, the results indicate that increasing the safety factor and length-to-width ratio leads to thinner, S-shaped moment–rotation curves, mainly owing to the enhanced recentering capability and the P-δ effect. Moreover, across all foundation types, the repetition of a limited loading cycles with consistent rotation amplitude does not cause stiffness degradation or moment capacity reduction.

Ground hydrocarbon contamination is a grave consequence of fossil fuel consumption, making it increasingly unsustainable. Consequently, researchers worldwide have been compelled to conduct a large number of studies on the geotechnical aspects of hydrocarbon-contaminated soils. Still, the complications arising from the integration of geotechnical complexities with diverse hydrocarbon properties present a substantial research need. The assessment of the foundation bearing capacity in hydrocarbon-contaminated soils is of paramount importance, especially given that numerous contaminated sites either house significant industrial facilities or are earmarked for critical infrastructure projects. This study investigates the shear strength and bearing capacity of gas oil-contaminated coastal sands using laboratory testing and physical modeling, with a special focus on the combined influence of the degree of saturation and relative density. Footing’s shear failure mechanisms were analyzed based on predicted and measured bearing capacity values. Findings show a decrease in the friction angle with a contamination increase, while the apparent cohesion initially rises before declining. Furthermore, the study revealed that the foundation’s bearing capacity exhibited an increase up to a specific contamination level, followed by a subsequent decrease. This increase is circa 90 and 100 percent at a 5 percent contamination content for loose and dense sand, respectively. Comparing the predicted and measured bearing capacity results shows that the general shear failure mechanism has occurred in the dense subgrade, while the loose subgrade’s failure mechanism is more inclined towards local shear failure.

Shallow foundations supporting high-rise structures are often subjected to extreme lateral loading from wind and seismic activities. Nonlinear soil–foundation system behaviors, such as foundation uplift or bearing capacity mobilization (i.e., rocking behavior), can act as energy dissipation mechanisms, potentially reducing structural demands. However, such merits may be achieved at the expense of large residual deformations and settlements, which are influenced by various factors. One key factor which is highly influential on soil deformation mechanisms during rocking is the foundation embedment depth. This aspect of rocking foundations is investigated in this study under varying subgrade densities and initial vertical factors of safety (FSv), using the PIV technique and appropriate instrumentation. A series of reduced-scale slow cyclic tests were performed using a single-degree-of-freedom (SDOF) structure model. This study first examines the deformation mechanisms of strip foundations with depth-to-width (D/B) ratios of 0, 0.25, and 1, and then explores the effects of embedment depth on the performance of square foundations, evaluating moment capacity, settlement, recentering capability, rotational stiffness, and damping characteristics. The results demonstrate that the predominant deformation mechanism of the soil mass transitions from a wedge mechanism in surface foundations to a scoop mechanism in embedded foundations. Increasing the embedment depth enhances recentering capabilities, reduces damping, decreases settlement, increases rotational stiffness, and improves the moment capacity of the foundations. This comprehensive exploration of foundation performance and soil deformation mechanisms, considering varying embedment depths, FSv values, and soil relative densities, offers insights for optimizing the performance of rocking foundations under lateral loading conditions.