Impact of the thin weak layer on the interaction of closely spaced shallow foundations resting on sand bed

In urban areas, shallow foundations are inevitably adjacent to each other. Moreover, the presence of thin, weak layers in these areas is not unanticipated. This study analyzes the combined impact of a thin, weak layer and the interaction of adjacent foundations on bearing capacity. Whereas previous research has separately explored the effects of weak layers and adjacent foundations. To attain the research objective, by utilizing the finite element method, the impact of various parameters, such as spacing between the foundations, the shear strength characteristics of a thin, weak layer, and the depth of this layer from the surface on the behavior of the adjacent shallow foundations studied. The foundation bed and thin-weak layer are assumed to be sandy soil. The analysis result indicates that the thin and weak layers reduce the bearing capacity of the shallow foundations, which is related to the shear strength parameters of the weak layer. Nevertheless, the placement of adjacent foundations at a short distance from each other reduces the negative impact of the existence of the thin, weak layer. This impact depends on the shear strength parameters, the depth of the weak layer, and the distance between the foundations. Compared to a single foundation, interfering footings can increase between 6 and 50% in the bearing capacity. The depth of the impact of the weak layer on the bearing capacity will also be a function of the distance between the adjacent foundations.