Hybrid Continuous-Discrete Modeling of an Ordinary Stone Column and Micromechanical Investigations

An innovative method for modeling a complicated geotechnical problem combining the coarse and fine zones is to use the hybrid methods. The granular zone of a geotechnical system can be modeled by the discrete element method (DEM) and the fine zone by continuum-based methods. The advantage of this approach is the use of the capabilities of both methods. In the present research, by combining DEM and finite difference method (FDM), a 2D numerical laboratory framework is constructed. Simulation of a vertically loaded stone column installed in clay was chosen to examine the capabilities of the present approach. The contrast between the stone column aggregates, which usually consist of crushed stone with distinct behavior, and the host medium, which is clay with continuum behavior, makes the stone column suitable for this kind of coupled simulation. The coupled numerical model is validated by comparing the load–settlement response of the numerical model and the reported experimental results. Afterward, the failure mechanism of the stone column is evaluated. The column bulging was captured properly, and it was found that in addition to the bulging, the contraction occurs at the upper portion of the column. It was also found that at the early stages of loading, the compaction occurs in the column. However, at later stages of loading, the bulging will happen. Furthermore, the results showed that bulging decreases the internal stresses of the column. All of these achievements were obtained by micro and macro investigations. The obtained results indicate that the coupled DEM–FDM method is a robust approach to simulate the behavior of some geotechnical problems.