Response of Radially Distributed Stone Column-Improved Soft Soil under Uniformly Distributed Axisymmetric Load: A 3D Numerical Study

Stone columns are, in general, constructed in an arrangement of regular polygons like triangles and squares. From the geometry, the stone column-improved ground with a regular polygon arrangement of stone columns cannot confirm the proportionate stress distribution from the foundation to the improved ground despite symmetric loading when the shape of the foundation is axisymmetric. In addition, the response of a large soft soil area that was improved with a group of stone columns was reported in very limited cases. In this study, a three-dimensional (3D) numerical model of the whole stone column-improved soft soil is developed in FLAC3D, which considers advanced constitutive models and the anisotropic flow of pore water to study the contact stress and vertical deformation in the improved soil under a symmetrically loaded axisymmetric large foundation for triangular and radial arrangements of the stone columns. In addition to the vertical settlement and contact stress, the rate of settlement, effect of embankment height, stress concentration ratio (SCR), and lateral displacement are studied numerically using the FLAC3D explicit finite-difference package. A 3D study is performed that considers the dissimilar positions of stone columns along different diametric sections, where only a quarter of the model is developed due to symmetry. The pattern of the stone column arrangement significantly affects the response of the stone column-improved soft soil. In addition, the effect of the arrangement is more prominent in the peripheral stone columns compared with stone columns near the center. Therefore, the radial pattern is the most suitable arrangement of stone columns in soft soil under uniformly loaded axisymmetric loading.