Vertical stability of geotextile-encased sand columns without and with surrounding soil

Use of geotextile encasement can enhance the axial capacity of individual sand columns by providing an additional confinement, hence reducing both the radial and axial deformations. In very weak soils, geotextile-encased sand columns (GESaCs) may buckle due to the lack of confinement offered by the surrounding soil. This paper focuses on the vertical stability of individual GESaCs of various diameters and lengths tested in air to demonstrate their performance in the extreme case where the surrounding soil offers no confinement, and in weak soil, which simulates the more likely case where such columns would be considered for use. Loose sand was selected to simulate the weak surrounding soil. Loading tests were conducted on individual GESaCs prepared in air and loose sand to investigate the load capacity, radial strain, and axial strain of columns. GESaCs of smaller diameters exhibited higher axial pressure capacities compared with those of larger diameters. GESaCs prepared in either air or loose sand delivered higher axial capacities at smaller length to diameter ratios. Columns in loose sand exhibited lower radial and axial strains as compared with those in air when the same pressure was applied on the top area of the column.