This paper studies numerical modeling of geosynthetic-encapsulated floating sand column. It discusses the applicability of floating sand column in different shear strength clay. Moreover, the mechanical mechanism of floating sand column under different parameters is investigated. Most studies of the literature focus on the behavior of geosynthetic-encapsulated sand columns embedded in clay with end supported by a hard stratum. This paper studies the behavior of floating sand column embedded in different shear-strength clay, which is used to evaluate the effectiveness of geosynthetic-encapsulated sand columns under appropriate development of sand column expansion and subsidence. The analysis shows that for a sand column with diameter ranging between 0.5~1.5m wrapped by a geosynthetic having stiffness ranging between 100 ~ 5000 kN/m, the floating sand columns are suitable to be placed in clay with shear strength ranging between 20 ~ 35 kPa. Critical length of an encased floating sand column is defined as the length that bearing capacity of the column is no longer increases with the increase of column length. As for a 1 meter diameter sand column wrapped with geosynthetic of 1000 kN/m stiffness, the critical length is 6 m for column embedded in every four clay types adopted in this study.