3D DEM-FDM Coupled Analysis of the Behavior of an Isolated Geogrid-Encased Stone Column under Axial Loading

Abstract

The axial loading test on a geogrid-encased stone column has been simulated using 3D numerical model in the proposed study. The stone column was modeled using the discrete element method (DEM), and the geogrid was modeled by the shell-type encasement using finite difference method (FDM). The column was modeled using nonspherical rigid particles considering the actual shape and size distribution of gravel, which better represents the discrete nature of stone columns. The rationality of the proposed numerical model was successfully verified by experimental results from a previous model test. The complete deformation and failure process of the geogrid-encased stone column has been well captured. The numerical results have been discussed at both the macroscopic and microscopic levels. The stress state of the geogrid-encased stone column never approaches the limiting equilibrium state before the geogrid rupture. The bearing capacity of the geogrid-encased stone column mainly depends on transverse ribs of the geogrid. The force chain network and coordination number evolvements inside the stone column were determined during the complete loading process and related to macroscopic failure behaviors. The parametric analysis indicates that linear relationships can be established between the macroscopic performance of the geogrid-encased stone column and the properties of the geogrid and gravel. The macroscopic and microscopic numerical results in this study can provide researchers improved understanding of the geogrid–gravel system.