Modeling the Stone Column Behavior in Soft Ground with Special Emphasis on Lateral Deformation
Among various ground-improvement techniques, soft-soil reinforcement by stone columns is one of the most common and convenient methods with numerous benefits including increased bearing capacity and consolidation, reduced postconstruction settlement and lateral movement, and improved slope stability and liquefaction control, among others. Because of the limited confinement offered by the surrounding soft soil especially at shallow depths, lateral deformation of stone columns is not uncommon. Although several analytical and numerical solutions are available to predict the load-settlement performance and consolidation characteristics of stone-column-improved soft ground, most existing models do not accurately capture the lateral deformation of stone columns. In view of this, the authors have developed in-house a novel numerical model based on the Fast Lagrangian Finite-Difference technique with associated subroutines to analyze the behavior of a stone column including its lateral deformation. In particular, the displacement compatibility and the barreling effect are considered in the model. Soft-soil consolidation under imposed loading is considered by adopting the modified Cam-clay theory. The proposed solutions are validated using available field observations and existing numerical solutions. The model was successfully applied to a selected case study at the Pacific Highway near the town of Ballina, New South Wales, Australia. It is demonstrated that both the deformation pattern and bulging depth of stone columns are dependent on several factors including the particle interlock, imposed load-intensity, soil-column stress concentration ratio, soil shear strength, and column geometry.
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