Geosynthetic-Encased Granular Columns Subjected to Vertical and Shear Loads

Granular columns are commonly used to support flexible structures over soft clay soils. The installation of such columns increases both the strength and stiffness of the ground. However, constructing these columns in clay soils having low cohesive strength of about 15 kPa is a challenge due to inadequate confinement. The columns may be encapsulated in geosynthetic tubes to enhance their constructability, strength and drainage properties. The geosynthetic encasement is also known to improve their performance under shear loading. This paper reviews the application of geosynthetic-encased granular columns for treatment of soft grounds. The design of these systems under vertical loads by two different methods is described in this paper. The performance of geosynthetic-encased granular columns under shear loads and the influence of geosynthetic encasement on the factor of safety of embankments supported on soft clay soils is discussed. The use of geosynthetic encasement of granular columns is seen to change the deep-seated foundation failure mechanism to toe failure mechanism.