Abstract: The failure modes of the granular columns reinforced with Geogrid tubes are analyzed. The ultimate axial capacity of the single column is proposed based on each failure mode. The influence of various factors, such as, the limit tensile strength of geogrids, the reinforcement depth, the column diameter and the internal friction angle of granular material, on the ultimate axial capacity of a single column is also studied. The results indicate that the geogrids can greatly improve ultimate axial capacity of the granular columns. The ratio of the ultimate axial capacity of a column with geogrid tube over a column without the tube is decrease with the increase of the column diameter.  The capacity ratio is also increase with the reinforcement depth. The magnitude of the ultimate axial capacity is also increase with the column diameter and the internal friction angle of the granular material.

Key words: Composite Foundations, Axial Capacity, Geogrids, Granular Column Reinforced with Geogrid Tubes