SLOPE STABILITY ANALYSIS OF EMBANKMENT OVER STONE COLUMN IMPROVED GROUND

Two-dimensional (2D) limit equilibrium analyses were conducted in this research to predict the factor of safety (FS) against the circular failure of embankments supported by stone columns improved ground. The analyses were based on equivalent area method. In this method, the treated zone, which comprises of the soft soils and the stone columns are replaced by an equivalent homogeneous soil with equivalent properties. The equivalent properties such as cohesion, friction angle and unit weight for the treated zone were calculated based on the weighted average of the properties of stone columns and soft soils. The influencing factors affecting the stability of embankment over the stone column improved ground were examined. These include the cohesion of soft clay, area replacement ratio, friction angle of stone columns, the height of embankment fill, the slope angle of embankment and stone column length. The limit equilibrium analyses were performed using the excel spreadsheet developed with the capability to identify the critical slip surface and the corresponding factor of safety calculated by Simplified Bishop Method. The accuracy of this limit equilibrium analysis was validated with three-dimensional finite element program (PLAXIS 3D) where good agreement was obtained in terms of location of slip circle and the factor of safety. The results showed that the embankment height was the most influencing factors in the safety analysis of the embankment while the least influencing factor was the friction angle of stone columns.