Document Type : Original Article

Author

• Yazdan Shams Maleki

assistant professor, Civil Engineering Dept., Faculty of Engineering, Kermanshah University of Technology, Kermanshah, Iran

Abstract

In this study, the numerical modeling of end-bearing stone columns was carried out using both time-dependent and time-independent constitutive models. The numerical modeling was performed using the two-dimensional finite element method based on the unit cell concept and assuming axisymmetric conditions. Soft Soil Creep (SSC) constitutive model was adopted in this study to account for the effects of time-dependent behavior and the consolidation state of clayey soft soils during the numerical modeling of stone columns installed in soft ground. To investigate the time-dependent response of stone column-improved soft soils, a series of two-dimensional finite element consolidation analyses was performed. The results obtained using the time-independent elastic-perfectly plastic Mohr-Coulomb (MC) constitutive model were systematically compared with those obtained from the time-dependent Soft Soil Creep (SSC) model. For the same soil profile, key response parameters - including lateral displacement, settlement, excess pore water pressure (EPWP), and stress distribution between the surrounding soil and the stone columns, represented by the Stress Concentration Factor (SCF) - were evaluated under two different numerical modeling approaches. The first approach employed a time-independent constitutive model (MC) combined with a time-dependent consolidation analysis, whereas the second approach incorporated both a time-dependent constitutive model (SSC) and a time-dependent consolidation analysis. A noteworthy aspect of this study is that both numerical approaches were applied to the same case study, thereby enabling a direct assessment of the influence of constitutive modeling assumptions on the predicted behavior. A major limitation of this study is that the behavior of the triangular arrangement of stone columns was investigated within the framework of the unit cell concept, which should be taken into consideration. The results of this study indicate that the stress concentration factor predicted by the SSC model is approximately twice that predicted by the MC model. Furthermore, compared with the MC model, the SSC model predicts a more delayed buildup and dissipation of excess pore water pressure, primarily due to the incorporation of creep effects in the constitutive formulation.

Keywords

• Stone column
• Soft soil creep model
• Consolidation analysis
• Time factor
• Incrementally constructed embankment

Main Subjects

• Geotechnics