A Theoretical Solution for Consolidation Rates of Stone Column‐Reinforced Foundations Accounting for Smear and Well Resistance Effects

Abstract

Theoretical and experimental studies have proven that stone columns can be used for accelerating the consolidation rate of soft soil by providing a drainage path and reducing stresses in the soil. In constructing stone columns in fine‐grained soils, however, soil zones at the interface between the columns and their surrounding soil can become smeared and the fine‐grained soil particles can also be mixed into aggregates in the columns. The smear and well resistance due to aggregates contaminated with the fine‐grained soil particles reduce the effectiveness of stone columns in dissipating excess pore water pressures. A theoretical solution is developed in this article for computing the consolidation rates of stone column reinforced foundations accounting for smear and well resistance effects. In the derivations, stone columns and soft soil are both considered deforming one‐dimensionally and the stone columns having a higher drained elastic modulus than the surrounding soft soil. A modified coefficient of consolidation is introduced to account for the effect of the stone column‐soil modular ratio or stress concentration ratio. A parametric study investigates the influences of six important factors on the rate of consolidation. These influence factors include the diameter ratio of the influence zone to the stone column, the permeability of the stone column, the stress concentration ratio, the size of the smeared zone, the permeability of the smeared zone, and the thickness of the soft soil. To assist geotechnical engineers in utilizing the new solution for the design of stone column reinforced foundations, an illustrative design example is presented at the end of this article.