Modeling Stone Columns in Soft Soil Using a Coupled Material Point–Discrete-Element Method

This study presents the first application of a coupled material point–discrete-element method to simulate the load–deformation behavior of a single stone column used for ground improvement in soft soil. In this framework, the stone column is modeled using the discrete-element method, while the surrounding soft soil is represented by the material point method, thereby combining the advantages of both discrete and continuum approaches. The reliability of the coupled framework is validated against experimental results, demonstrating good agreement in load–settlement behavior, stress transfer mechanisms, and column bulging deformation. A series of parametric studies are also conducted to evaluate the effects of soil stiffness, soil strength, column initial porosity, gravel gradation, and area ratio on the load-bearing response of the composite foundation. The load–settlement curves, distribution of stress transfer coefficients, and shear stress along the column–soil interface are presented, along with contour plots of equivalent plastic strain, horizontal and vertical displacements, and vertical stress. These findings offer critical insights into the complex mechanical behavior and safety design of stone columns in engineering practice.