Numerical study on ground improvement for liquefaction mitigation using stone columns encased with geosynthetics

The geosynthetic-encased stone column (ESC) strategy has been extensively used for improving soft soils. However, no studies have been conducted to assess the use of ESCs to mitigate sand strata. In this study, three-dimensional finite element (FE) analyses were conducted to explore the mitigation of mildly sloped saturated sand strata using ESC approaches. We investigated the encasement effect in ESC remediation and the effect of the following important design parameters in reducing lateral ground deformation: the thickness, the tensile stiffness, and the permeability of the geosynthetic; the ESC diameter; and the distributed load at the stone column (SC) surface. The results showed that the ESC remediation reduced more lateral deformation, compared to the SC approach. The ground stiffening was also dramatically enhanced as the stiffness and thickness of the geosynthetic and the ESC diameter were increased, but the encased efficiency gradually decreased. The lateral ground displacement began to decrease significantly when the permeability of the geosynthetic exceeded 0.1 m/s. The larger surface load did not prevent soil liquefaction, but it produced significantly less displacements and virtually no permanent deformation.