Stone Column-Stabilized Soft-Soil Performance Influenced by Clogging and Lateral Deformation: Laboratory and Numerical Evaluation

Stabilizing the soft clay by stone column reinforcement is one of the most accepted methods of ground improvement techniques. Because of their larger diameter and higher hydraulic conductivity, drainage with stone columns is much faster than prefabricated vertical drains (PVDs) or sand compaction piles (SCPs). Still, a significant hydraulic gradient at the soil-column interface induces migration of clay particles into the column pores, leading to clogging, which adversely affects the consolidation rate of soft soil. The load bearing capacity that stone columns acquire depends primarily on the lateral confinement offered by the surrounding soft soil. Because of limited confinement at shallow depths, the stone column deforms laterally leading to bulging. This paper presents an in-depth study on the load settlement and consolidation characteristics of soft clay stabilized by stone columns with particular reference to clogging and lateral deformation via laboratory model tests and numerical analysis. The laboratory investigation includes one-dimensional consolidation tests with instrumented columns in reconstituted soft clay, X-ray computed tomography (CT) scanning to study the load transfer, column deformation and clogging characteristics, and a numerical analysis based on a fast Lagrangian finite-difference technique with associated subroutines. Previous solutions developed by the authors have been substantially modified to accommodate a time dependency of clogging, load transfer, and lateral deformation of columns. The proposed solutions are validated by experimental results, which demonstrate that the load settlement and column deformation pattern as well as the consolidation characteristics are significantly affected by clogging and lateral deformation of stone column.