Effect of area replacement ratio on consolidation settlement of floating stone column in soft soil

Soft clay soils present significant challenges in construction due to their low bearing capacity and high compressibility. While stone columns are commonly used to improve such soils, floating stone columns are less favored due to the complexity of predicting consolidation behavior, particularly with double-layered conditions. Limited experimental research using unit cell idealization exists to support numerical validation for floating columns, and the accuracy of settlement prediction in untreated zones remains unclear. This study investigates the effect of area replacement ratio (α = 0.10 - 0.33) on the consolidation behavior of floating stone columns using laboratory model tests and numerical simulations. Unit cell idealization was employed to assess settlement, excess pore water pressure, and stress concentration ratio, with floating columns (Hc = 160 mm and 320 mm) and end-bearing columns (Hc = 400 mm) embedded in soft kaolin clay under vertical loading. Results showed that increasing α reduced settlement by up to 70%, accelerated consolidation by up to 96%, and increased stress concentration ratio from 2.1 to 5.0. Although numerical analysis slightly overestimated early-stage settlement, it showed reasonable agreement with experimental results. A new design method was developed to estimate the settlement improvement factor and stress concentration ratio for floating stone columns, and it demonstrated good agreement with existing models, offering improved reliability for design applications.