Influence of Gravel Size and Geogrid Aperture on Performance of Geosynthetic-Encased Stone Column: DEM-FDM Coupled Numerical Investigation

In order to investigate the effects of gravel particle size and geogrid aperture on the bearing performance of geosynthetic-encased stone columns, a discrete–continuum coupled numerical model was established based on laboratory test results, and a series of numerical simulations were conducted. The results indicate that, under the same loading level, the maximum lateral bulging of geosynthetic-encased stone columns increases with increasing geogrid aperture and decreases with increasing gravel particle size. The distance between the location of maximum lateral bulging and the pile-top decreases as the aperture increases, whereas it increases with increasing particle size. The bearing performance of geosynthetic-encased stone columns shows a positive correlation with gravel particle size and a negative correlation with geogrid aperture. The influence of particle size on bearing performance becomes insignificant when d50 exceeds 40 mm. When the particle size is smaller than the geogrid aperture, contact between the gravel and the geogrid is established but remains insufficient, leading to separation as the load increases. In contrast, when the particle size is larger than the aperture, the effect of particle size on bearing performance is much more pronounced than that of aperture. Therefore, the use of gravel with a particle size slightly larger than the geogrid aperture is recommended in practical engineering applications.