Optimized Design of Floating Stone Columns for Enhanced Long-term Settlement Performance of Soft Soils

In two-dimensional axial symmetry finite element analyses, compressible clayey deposits improved by a large group of floating stone columns were performed using the unit cell idealization. The primary focus of this study is to assess the efficiency of floating stone columns in enhancing the consolidation rate of low-permeable soils. Additionally, it aims to evaluate the long-term stability of constructions built along marine coastal areas. To this end, two real case studies were investigated; the Béjaïa and Algiers Mediterranean harbors. Various geometric variables, pertaining to the design of floating stone columns, have been considered to analyze their effect in impacting the consolidation process and the long-term behavior emphasizing their fundamental importance in the design. Besides, a thorough comparison between the design in both short-term and long-term conditions, satisfying the admissible settlement, has been made, ultimately resulting in the optimized design selected. The results also indicate that increasing both the area improvement ratio and the floating column length leads to a speeding up of the consolidation rate. However, in contrast to the area substitution ratio, the column length has comparatively lesser importance in terms of reducing the settlement. Importantly, it is demonstrated that the design of floating stone columns for long-term conditions is significantly distinct from that for short-term conditions, requiring an approximate 40% increase in the area improvement ratio as designs based on the immediate settlement may not align with improved soft soil long-term behavior. Finally, the study reveals that the applied load ultimately governs the design of floating stone columns.