Numerical analysis of a laboratory-modelled geosynthetic-partially encased columns applied as shallow foundation support in frictional-cohesive soils

The utilization of geosynthetic-encased granular columns is an advantageous and environmentally friendly technique for enhancing fine-grained soil foundations, particularly for supporting footings in specific conditions. These conditions may include collapsible and porous soils, serving as a viable alternative to conventional concrete piles. This study evaluates the geomechanical behavior of GECs as an improvement technique of fine-grained soils beneath shallow foundations, with a particular emphasis on evaluating the impact of encasement length and footing diameter. The investigation involves laboratory tests using 1-g small-scale models of granular columns subjected to incremental static load stages. These models were instrumented not only to measure the applied loads and resulting settlements, but also to assess the earth pressures developed along the depth. This approach was adopted for a comprehensive understanding of the stress transfer mechanisms inherent in employing partial encasement techniques. The responses of these models contribute to the development, calibration, and validation of a numerical model, based on the finite element method, facilitating further analyses to explore the impact of encasement length and granular column diameter in relation to footing dimensions. The findings demonstrate that employing partial encasements in granular columns effectively prevents columns bulging within shallow depths, concurrently improving stress transfer mechanisms in deeper soil strata. Additionally, the study highlights the critical influence of the encasement length concerning the column height (R/L) and the ratio between footing and column diameters (D/d). These factors significantly affect column failure mechanisms, thus bearing substantial implications for the design of shallow foundations supported by columns.