Improvement of consolidation settlement beneath square footings using uncased and encased stone columns

Stone columns are considered a sustainable stabilization technique that has environmental compatibility and economic aspects to enhance the properties of soft soils below the overlying structures. This paper explores the effects of main related parameters on the consolidation settlement of square footing that rests over soft clay soil that treated using encased and unreinforced (uncased) stone columns. A Finite element modeling is established using PLAXIS 3D Software and was verified by previous experimental data. An extensive parametric study is performed numerically using various stone column parameters such as different replacement area ratios (Ar), numbers, lengths, properties, and geotextile lengths to determine the strain-stress behavior of stone columns. The developed finite element models found that the stone column area ratio (Ar) reduces both the settlements beneath the foundation and excess pore water pressure by 43% and 41%, respectively at Ar = 20%. Also, by increasing the penetrated depth and elastic modulus of stone columns, the settlement decreases significantly under footing. Conversely, there are slight effects of the stone columns number that have a constant area ratio on the foundation settlement. Furthermore, the optimal geotextile encasement length that reduces the settlement effectively was achieved when the encasement height ratio was half of the stone column height. Utilizing half-height encasement leads to cost savings, as it yields a 34% reduction in settlement from the uncased case while the settlement reduction achieved with full-height encasement was 44%.