Behavior of Geotextile-Encased Granular Columns Supporting Test Embankment on Soft Deposit

A 5.35 m high test embankment was constructed on a soft foundation improved by geotextile-encased granular columns (GECs). The embankment construction was performed in four stages over 65 days, resulting in a total applied stress of around 150 kPa. The soft soil and the encased columns were instrumented to measure surface settlements, excess pore pressure, surface vertical stresses, and radial deformation of the geotextile encasement. Stress concentration and the difference in settlement between the top of the encased columns and the soft soil were studied. Results showed that the differential settlement increased as the embankment height increased and when the excess pore pressure was being dissipated. Due to soil arching, the vertical stress supported by the encased column was over two times greater than the stress transmitted to the soft soil. Also, vertical stress on the encased column increased as consolidation progressed, whereas it did not vary significantly on the soft soil.