Investigation of liquefiable sandy soil improvement by ordinary and geotextile-reinforced stone columns using small-scale shaking table

The increase in construction in coastal cities, which are prone to liquefaction due to the high level of underground water and soil type, along with their soil conditions that do not meet the technical requirements, has led engineers to undertake soil improvement. Among the liquefaction mitigation methods, the stone column technique has been considered one of the most versatile and economical ground improvement techniques, including increasing the density of surrounding soil by vibration and replacement, expediting drainage, and reducing the shear stress of surrounding soil by introducing stiff elements. This study evaluated the seismic performance of stone columns and full- and partial-length geotextile-encased stone columns as a liquefaction countermeasure in the loose sample of Firoozkooh No. 161 sand. The sands were susceptible to liquefaction in a loose state, i.e., around 25% relative density, when subjected to a sinusoidal acceleration of 0.35g and 3Hz frequency. A group of nine ordinary and geotextile-reinforced stone columns with a diameter and length of 5 cm and 50 cm, respectively, has been created. In order to evaluate the seismic behavior, four reduced scale 1-g model tests were conducted using a uniaxial shake table on the group of ordinary and geotextile-reinforced stone columns. Based on the obtained results, reinforcing the full length of the stone columns using geotextile has prevented liquefaction in the surface layers, reduced the excess pore water pressure ratio, increased the soil stiffness, and overall more effective performance than ordinary stone columns. Conversely, acceleration amplitudes can be amplified when the soil has not reached the state of liquefaction since the rigidity of the soil medium is preserved. Stone columns are not effective against the liquefaction of surface layers. They can only reduce the time the area remains in a liquefaction state.


Based on the obtained results, reinforcing the full length of the stone columns using geotextile has led to the non-occurrence of liquefaction in the surface layers, the reduction of the excess pore water pressure ratio, the increase of the soil stiffness and overall more effective performance than ordinary stone columns.