Effects of Geogrid Encasement on Behavior of Stone Column-Improved Soft Clay

Geosynthetic-encased stone columns (GESC) are commonly used to support embankments over soft clay. The load transfer mechanism and particle interactions have received little attention from researchers. This study presented some interesting results obtained from a numerical analysis using three-dimensional (3D) discrete element method (DEM). The aggregate, the geogrid encasement, and the soft clay were simulated using particles with different sizes and micromechanical properties. A validated DEM model was proposed to simulate the stone column-improved soft clay under a plate loading condition. Two important factors, the encasement length and the tensile stiffness of the geogrid, were investigated and showed different effects on the behavior of the stone column-improved soft clay. The encasement length had significant effects on the bearing capacity, the vertical and radial stresses of the column and the soft clay, and the tensile strain of the geogrid. The geogrid stiffness has negligible effect on the bearing capacity for partially encased stone column (e.g., the encasement length was twice the diameter of the column). The aggregate below the geogrid encasement was more likely to move laterally with the increase of the geogrid stiffness and caused bulging failure in the deep section.