Simplified homogenization method in stone column designs

The homogenization technique has been developed to model stone column improved grounds by establishing the equivalent material properties for the composite ground. However, homogenization techniques based on the elasto-plastic behavior of the constituent materials found in literature require modification in terms of the finite element constitutive models which are difficult for practical engineers to apply. Therefore, a simple yet effective way of predicting the consolidation performance of stone column improved grounds has been invoked in this study. The method is called the equivalent column method (ECM). The new method provides not only equivalent stiffness for the composite material, but also equivalent permeability. The method is derived from an analysis using the unit cell model in a 2D finite element axisymmetrical model. The settlement is calculated and a correction factor is obtained via a comparison with the results calculated using a single averaging composite stiffness for the improved ground. Correlations are summarized in the form of design charts for the key parameters, such as the area replacement ratio, the loading intensity, and the friction angle of the column material. Through a series of tests for different area replacement ratios, the equivalent permeability is established and presented in a design chart for different permeability ratios. ECM shows a good agreement with the current design methods and field results. The advantage of the proposed method over other homogenization techniques is the simplicity of its use which renders easy model set-up in the finite element program, especially for embankments and large tank problems, besides its extra ability to predict the consolidation time.