When constructing structures receiving high vertical and horizontal force such as port facilities, caissons and breakwaters on a soft ground on the sea or seashore, it is very important to increase the strength of the ground and inhibit excessive settlement. Recently, there have been numerous studies on the method of wrapping the outer wall of granular piles with geotextile or geogrid that has a certain level of tensile strength. Since the geotextile increases the strength of granular piles by confinement effects, those confined granular piles more advantages than the Conventional Sand Compaction Piles (SCP) in terms of the bearing capacity and settlement. Furthermore, this method consumes less aggregate compared to the conventional Sand Compaction Pile (SCP) or Gravel Compaction Pile (GCP) method. This study proposed to determine the characteristics of mechanical behaviors such as bearing capacity and stress concentration ratio of a composite ground improved using SCPs reinforced with geotextile (Geotextile-Encased Sand Pile, GESP) as an alternative to the conventional SCP method. With this purpose, several loading tests were conducted on the artificially sedimented clay grounds reinforced using conventional SCPs and GESPs with geotextiles of three different tensile strengths with various replacement ratios. Based on the results of this study, the bearing capacity of the soft clay ground reinforced by the GESPs is larger than that of the soft ground reinforced by the conventional SCPs and the failure mode of the GESPs is buckling different from the bulging of the SCPs. The tensile strength of the geotextile has little effect on the bearing capacity in the buckling failure of GESPs.