INFLUENCE OF FOOTING SPACING AND ADJACENT FOOTING INTERACTION ON SETTLEMENT OF SHALLOW FOUNDATIONS: A NUMERICAL STUDY USING PLAXIS 3D

Abstract

Settlement behavior of shallow foundations is a critical consideration in geotechnical design, particularly when multiple footings are constructed in close proximity. Conventional design methods often neglect the interaction between adjacent foundations, which may lead to inaccurate predictions of settlement behavior. This study investigates the interaction effects of multiple shallow foundations using three-dimensional finite element modeling in PLAXIS 3D. A parametric analysis was conducted for a 4 × 4 footing group by varying the spacing-to-width ratio (s/b) ranging from 1.0 to 3.0. The results show that foundation interaction significantly increases settlement compared with isolated footings due to the overlap of stress zones in the underlying soil, which leads to greater deformation and redistribution of stresses. At a spacing ratio of s/b = 2.0, the central footing exhibits the largest settlement amplification, approximately 77.85%, indicating strong interaction effects within the group. As the spacing ratio increases (s/b ≥ 3.0), the stress overlap reduces and the interaction effect becomes negligible, resulting in behavior similar to isolated footings. These findings demonstrate that neglecting footing interaction may lead to underestimation of settlement in dense foundation systems. Therefore, considering interaction effects is essential for improving the accuracy of settlement prediction and optimizing foundation layout in practical engineering design, especially in dense urban environments.