Geosynthetic-encased stone columns in soft clay: A numerical study

This paper presents the findings of a series of numerical studies on the contribution of geosynthetic encasement in enhancing the performance of stone columns in very soft clay deposits. In this study, the imposed loading is from a fill embankment, and the stone columns act like reinforcements. Observed settlement of a trial embankment built on very soft clay strengthened with stone columns indicated that the stone columns alone were not adequately effective in reducing settlement because the very softy clay could not provide adequate confining stress to the stones. An alternative system utilizing geosynthetic encasement was examined numerically. As the primary issue is the development of settlement with time after the completion of stone column installation, a fully coupled analysis was performed. To reduce the computational effort, a unit cell idealization was adopted. This study showed that the use of geosynthetic encasement has the potential of significantly enhancing the effectiveness of stone columns in very soft clay and the simplified analysis presented in earlier work is valid. Furthermore, the predicted performance was found to be insensitive to assumed stiffness parameters of the compacted stone. However, it was found to be dependent on the locked-in stress in the geosynthetic encasement induced during installation.