The bearing capacity and deformation characteristics of floating stone columns were complicated and are not thoroughly understood. In the present study, a series of experimental model tests of floating stone columns under vertical plate loading was performed. This study investigated the influence of geogrid encasement on the behavior of floating stone columns and provided valuable insight into the load-displacement behavior, bulging deformation, load transfer mechanism, and the radial stress of the geogrid encasement. The test results show that the bearing capacity of the floating stone column was significantly improved due to the geogrid encasement. The column with longer encasement showed higher stiffness at large settlements. The bulging deformation pattern of the column changed with different encasement lengths. More vertical pressure transferred from the top of the column to the bottom of the column due to the existence of the geogrid encasement. The fully encased stone columns developed high radial stress and achieved effective confinement of the column. The bearing capacities of the floating-encased stone columns with different encasement lengths were controlled by bulging deformation instead of penetration failure, which gave confidence that the floating-encased stone columns were an effective method for field construction in extensive soft soils.

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The ordinary (OSC) and geosynthetic-encased stone column (ESC) with different bearing strata significantly influenced its behavior. The paper established seven models for studying the behavior of floating stone columns using the finite difference method (FDM). The effect of geogrid and column length on the load-settlement behavior, bulging deformation, failure mode, and load transfer coefficient were also analyzed based on proposal models. The results showed that the bearing capacity of F-OSCs and F-ESCs increased with the increase in column and encasement length, respectively, and a critical length (i.e., 4D, where D was the column diameter) was found in settlement improvement. The bulging deformation was significant in F-OSCs and was observed at the top of a long column and the full length of a short column. The geogrid encasement could constrain the OSC to decrease the bulging deformation. The failure mode in F-OSCs was mainly a punching failure with bulging deformation for a short column (e.g., less than 4D), and was relative to the vertical pressure for a long column. The failure mode in F-ESCs was a punching failure, and the punching degree increased with an increase in encasement length. The load transfer coefficient of F-OSCs or F-ESCs was relatively stable as the column length increased to a critical value (e.g., 4D) or the encasement length increased to a critical value (e.g., 4D).