A simplified approach for evaluating the bearing performance of encased granular columns

Tensile resistant materials used to encase cylindrical granular columns significantly improve column strength. For an encased granular column subjected to axial load, the axial deformation and volumetric expansion causes lateral expansion, which induces circumferential strain and stress in the encasement and provides additional confining pressure to the column.To make good predictions of column behavior through numerical analysis, elaborate deductive and regressive work is needed to describe the mechanical properties of the filled material. This study analyzes the bearing performance of geosynthetic-encased sand columns using a simplified approach to reduce such laborious deductive efforts. A few equations and calculation steps are also proposed to evaluate the confining pressure increments and deviatoric stress due to encasement extension.The proposed approach employs an empirical correlation between the dilation rate and deviatoric strain of pure sand to evaluate the volumetric strain of deformed encased granular columns. The approach has also been extended to evaluate the use of the constant volume assumption in predicting the responses of encased granular columns. The relationships between the confining pressure increment and encasement stiffness/column diameter ratio are established through simplified assumptions.Results obtained from the proposed approach are validated and found to be in good agreement with the experimental measurements and numerically analysis results under rigorous parameter acquisition. The proposed approach provides accurate results without laborious analytical efforts.