One of the best improvement methods of soft clay soils, especially in order to increase the stability of embankments in highway and rail way projects is using of ordinary granular column or encased one. The present study, presents the results of numerical analysis for the studying of Interaction between granular columns and soft clay in two cases of ordinary and encased with geosynthetic situations. A single granular column has been modeled for the two cases of ordinary and encased with geosynthetic. Also, the effect of variation of column length and diameter has been investigated. The analysis is conducted with a two-dimensional finite element program (2D) using the (PLAXIS20) software package. Results from the present work have been oriented toward the influence of encased by geosynthetic, variation of column length and diameter on shear stress as well as the axial forces taking into consideration the effect of interface criterion. Based on the results of the current numerical analysis, correlation has been proposed for estimating the improvement ratio based on the interface criteria of granular column – soft clay composite.