Direct Shear Tests on Soft Clay Reinforced with Single Ordinary Granular Column: Discrete Element-Finite Difference Method

A great deal of research has been conducted on the performance of granular columns under vertical loads. However, in some situations, the movement of the soil mass can lead to lateral deformations and, as a result, shear stresses in the soil and columns. The primary objective of the present study is to numerically investigate the shear performance of soft clay soil improved with a single Ordinary Granular Column (OGC) in the direct shear test using a hybrid Discrete Element-Finite Difference Method (DEM-FDM). The numerical modeling method was first validated by simulating a direct shear test conducted previously on a soft clay-OGC composite in the laboratory. Afterward, an extensive parametric study was conducted to determine how various factors affect the shear strength of clay-OGC composites. According to the results, increasing the area replacement ratio from 15 to 35% can increase the peak shear strength of clay-OGC composites in the direct shear test by up to two times, depending on the level of applied normal stress. The micro-scale results also indicated that the surface roughness of soil particles in OGC has a greater effect on the shear strength of clay-OGC composites than their angularity. Furthermore, the results showed that the equivalent friction angle of clay-OGC composites should be calculated based on the residual friction angle of granular soil used in OGC. © 2024 The author(s). This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, as long as the original authors and source are cited. No permission is required from the authors or the publishers.