Abstract: The centrifugal model tests are performed on embankments on composite foundation reinforced by two groups of geosynthetic-encased stone columns (GECs) with different stiffnesses and by a group of ordinary stone columns (OSCs) as a comparison test. The behavior and stability of GECs under actual stress conditions are studied. The results show that an increase in geosynthetic stiffness leads to a little decrease in the excess pore water pressure, apparent decrease in the settlements at the top of the columns and the soils, whereas apparent increase in the differential settlement. The stress concentration ratio increases with an increase in the geosynthetic stiffness, but the rate of increase decreases gradually. When the geosynthetic stiffness is low or embankment load is large, GECs can bend significantly so as to incur apparent settlement, while OSCs are apt to bulge to incur larger settlement. However, there is no tendency of shear sliding in the soils treated by GECs and OSCs.