Undrained stability analysis of embankments supported on geosynthetic encased granular columns

A systematic series of slope stability analyses were performed on embankments supported on soft clay soils treated with ordinary granular columns (OGCs) and geosynthetic encased granular columns (EGCs). The effect of various parameters such as the undrained shear strength of soft clay, friction angle of fill materials and aggregate in granular columns, area replacement ratio and the secant modulus of geosynthetic encasement on the factor of safety (FS) is analysed. A higher FS value is observed for EGC-supported embankments compared to embankments supported on OGC. In addition to full three dimensional (3D) modeling, an equivalent method is also presented in order to compare the solution accuracy and the relative computational efforts. The equivalent method yields similar FS values to 3D column models in the case of OGC, with lower computational costs. In the case of EGC, both methods give different FS values when the critical slip surface passes through the foundation soil, owing to the absence of the confinement effect provided by the geosynthetic in the equivalent method. For the same FS value, a significant reduction in area replacement ratio is observed when using geosynthetic encasement, which can reduce the consumption of natural resources.