Comparison of settlement between granular columns with and without geosynthetic encasement

Abstract

Granular columns have been used to improve load bearing capacity and to reduce the settlement of the soft soils for the past three decades. However, for soft soils with less than 15 kPa of undrained shear strength, the use of granular columns is ineffective because the soft soil does not mobilize sufficiently lateral confinement stress to balance the column lateral stress, which leads to the laterally deformed column (bulging) at the top section of the column. To overcome this limitation, many researchers have developed a new method of soil improvement using granular columns with geosynthetic encasement, which are actually an extension of the granular columns. This new approach, which is more advantageous than the granular columns, is thanks to geosynthetic providing additional confinement stress in conjunction with the soil surrounding the column. In this paper, the authors apply analytical solutions based on “unit cell concept” model in order to compare the effect of settlement between stone columns and stone columns with geosynthetic encasement implementing to reinforce the soft soil ground of Vifon II plant in Long An. The authors also investigate the effect on the column settlement due to variables of the column diameter, column spacing and embankment height. The results show that in all cases, the settlement of stone column is about 50-80% higher than stone column with geosynthetic encasement, which have proved the superior efficiency of geosynthetic encased column (GEC) compared to conventional stone applied in soft soil improvement.