Laboratory tests on geosynthetic-encapsulated sand columns

Granular columns have been introduced into engineering practice to improve the bearing capacity and reduce settlement of sand column in a weak or soft soil. The improvement can be enhanced by encapsulating the column with tensile resistant material. The improvement depends on the confinement offered by the surrounding soil, the reinforcing material and the granular column material. In this study, the extent of improvement for a sand column subjected to constant confining pressures is studied through laboratory experiments. A series of triaxial compression tests were carried out in laboratory to investigate the response of sand columns encapsulated by geotextiles. The tests consisted of triaxial compression tests on sand columns with two different densities and encapsulated by sleeves fabricated from three different geotextiles. The increase in deviatoric stress, the reductions in volumetric and radial strains, and the increase in confining pressure generated by the encapsulating reinforcement were measured and analyzed. The mobilized pseudo-cohesion and friction angle corresponding to various axial strains are analyzed to interpret the reinforcing effect. The experimental results are compared with data obtained from analytical method reported in the literature.